MACROPOROUS OXYGEN SOLID CARRIER WITH OXIDE CERAMIC MATRIX, PROCESS FOR PREPARING THE SAME AND USE T

专利摘要:
The invention relates to an oxygen carrier solid, its preparation and its use in an oxidation-reduction process in chemical loop on active mass such as chemical looping combustion (CLC). The solid in the form of particles comprises an oxidation-reduction active mass formed of metal oxide (s) dispersed in a ceramic matrix comprising at least one oxide having a melting point greater than 1500 ° C., such as alumina, and has a specific macroporous initial texture. The oxygen-carrying solid is prepared from an aqueous suspension comprising grains of precursor oxides of the ceramic matrix of specific size, by a spray drying technique.
公开号:FR3061036A1
申请号:FR1663301
申请日:2016-12-23
公开日:2018-06-29
发明作者:Arnold Lambert；Mathieu Michau；Delphine MARTI；Elodie COMTE
申请人:IFP Energies Nouvelles IFPEN；Total Raffinage Chimie SAS；
IPC主号:

专利说明:

@ Holder (s): IFP ENERGIES NOUVELLES Public establishment, TOTAL REFINAGE CHIMIE Société anonyme.
o Extension request (s):
® Agent (s): IFP ENERGIES NOUVELLES.
® SOLID CARRIER OF MACROPOROUS OXYGEN WITH A CERAMIC OXIDE MATRIX, ITS PREPARATION METHOD AND ITS USE FOR A CHEMICAL LOOP OXYDO REDUCTION PROCESS.
FR 3,061,036 - A1 (57). The invention relates to an oxygen-carrying solid, its preparation and its use in a chemical loop oxidation-reduction process on an active mass such as chemical loop combustion (CLC). The solid in the form of particles comprises an active redox mass formed of metal oxide (s) dispersed in a ceramic matrix comprising at least one oxide having a melting temperature above 1500 ° C., such as alumina, and has a specific macroporous initial texture. The oxygen-carrying solid is prepared from an aqueous suspension comprising grains of precursor oxides of the ceramic matrix of specific size, by a spray drying technique.
0m (nm)
Field of the invention
The present invention relates to an oxygen-carrying solid, its preparation and its use in an oxidation-reduction process in chemical loop on active mass, commonly called "Chemical Looping" according to English terminology. In particular, the new type of oxygen-carrying solid according to the invention can be used in a chemical loop combustion (CLC) process.
General context
The chemical loop redox processes on active mass are known in the field of energy production, gas turbines, boilers and furnaces, especially for the oil, glass and cement industry.
In particular, the production of electricity, heat, hydrogen or steam can be carried out by this type of process, typically the CLC process, using redox reactions of an active mass, called mass redox, typically a metal oxide, to produce a hot gas from a fuel, for example natural gas, carbon monoxide CO, hydrogen H ₂ , coals or petroleum residues, a mixture of hydrocarbons, and isolate the carbon dioxide CO ₂ produced. It is therefore possible to store the CO ₂ captured in geological formations, or to use it as a reagent in other processes, or even to inject it into oil wells in order to increase the quantity of hydrocarbons extracted from deposits (enhanced recovery of EOR oil and EGR gas, for "Enhanced Oil Recovery" and "Enhanced Gas Recovery" in English).
In such an oxidation-reduction process in a chemical loop on active mass, a first oxidation reaction of the active mass with air or another oxidizing gas, playing the role of oxidizer, allows, due to the exothermic nature from oxidation, to obtain a hot gas whose energy can then be exploited. When the oxidizing gas is water vapor, the oxidation of the active mass also makes it possible to produce a gaseous effluent rich in H ₂ .
A second reaction for reducing the active mass oxidized using a gas, a liquid or a reducing solid (hydrocarbon feed) then makes it possible to obtain a reusable active mass as well as a gaseous mixture essentially comprising CO ₂ and water, or even synthesis gas containing CO and H ₂ , according to the conditions operated during the reduction step.
In a CLC process, energy can be produced in the form of steam or electricity, for example. The heat of combustion of the hydrocarbon feedstock is similar to that encountered in conventional combustion. This corresponds to the sum of the reduction and oxidation heats in the chemical loop. The heat is generally extracted by exchangers located inside, on the wall or in the appendix of the fuel and / or air reactors, on the smoke lines, or on the transfer lines of the active mass.
A major advantage of these oxidation-reduction processes in a chemical loop on active mass is then to allow the CO ₂ (or synthesis gas) contained in the gas mixture devoid of oxygen and nitrogen constituting l to be easily isolated. effluent from the reduction reactor. Another advantage consists in the production of a flow of nitrogen N ₂ (and of argon) containing practically no more oxygen, and corresponding to the effluent coming from the oxidation reactor, when the air is used as oxidizing gas.
In a context of growing world energy demand, the CLC process therefore provides an attractive solution for capturing CO ₂ with a view to its sequestration or its recovery for other processes, in order to limit the emission of greenhouse gases. greenhouse harmful to the environment.
US Patent 5,447,024 describes, for example, a CLC process comprising a first reactor for reducing an active mass using a reducing gas and a second oxidation reactor enabling the active mass to be restored to its oxidized state by an oxidation reaction with humid air. The circulating fluidized bed technology is used to allow the continuous passage of the active mass from the reduction reactor to the oxidation reactor and vice versa.
Patent application WO 2006/123925 describes another implementation of the CLC process using one or more fixed bed reactors containing the active mass, the redox cycles being carried out by gas permutation in order to successively carry out the oxidation and reduction in active mass.
The active mass, passing alternately from its oxidized form to its reduced form and vice versa, describes a redox cycle.
It should be noted that, in general, the terms oxidation and reduction are used in relation to the respectively oxidized or reduced state of the active mass. The oxidation reactor is that in which the active mass is oxidized and the reduction reactor is the reactor in which the active mass is reduced.
Thus, in the reduction reactor, the active mass, generally a metal oxide (M _x O _y ), is first of all reduced to the M _x O _{y state} . _2n -m / 2, via a hydrocarbon C _n H _m , which is correlatively oxidized to CO ₂ and H ₂ O, according to reaction (1), or optionally to a CO + H ₂ mixture depending on the nature of the active mass and the proportions used.
CnHm + M _x O _y Π CO ₂ + m / 2 H ₂ O + M _x O _y - ₂ nm / 2 (1)
In the oxidation reactor, the active mass is restored to its oxidized state (M _x O _y ) in contact with air according to reaction (2), before returning to the first reactor.
M _x O _y . _2n . _m / 2 + (n + m / 4) O ₂ * M _x O _y (2)
In the case where the active mass is oxidized by water vapor, a flow of hydrogen is obtained at the outlet of the oxidation reactor (reaction (3)).
M _x O _y . _2n . _m / 2 + (2n + m / 2) H ₂ O ”* M _x O _y + (2n + m / 2) H ₂ (3)
In the above equations, M represents a metal.
The active mass has a role of oxygen carrier in the oxidation-reduction process in chemical loop. One thus commonly designates as solid carrying oxygen the solid comprising the active mass, typically comprising the metal oxide or oxides capable of exchanging oxygen under the redox conditions of the oxidation-reduction process in chemical loop
The oxygen-carrying solid may also comprise a binder or a support in association with the active mass, in particular to ensure good reversibility of the oxidation and reduction reactions, and to improve the mechanical resistance of the particles. In fact, the active masses, chosen for example from the redox couples of copper, nickel, iron, manganese and / or cobalt, are generally not used pure because the successive oxidation / reduction cycles at high temperature cause a significant and rapid decrease in the oxygen transfer capacity, due to the sintering of the particles.
Thus, in US Pat. No. 5,447,024, the oxygen-carrying solid comprises an oxido-reducing couple NiO / Ni as active mass, associated with a binder YSZ which is zirconia stabilized by yttrium, also called yttria zirconia.
Many types of binders and supports, in addition to yttria zirconia YSZ, have been studied in the literature, in order to increase the mechanical resistance of particles at a lower cost than YSZ. Among these, there may be mentioned alumina, metal aluminate spinels, titanium dioxide, silica, zirconia, cerine, kaolin, bentonite, etc.
The efficiency of the chemical loop oxidation-reduction process depends mainly on the physicochemical properties of the oxygen-carrying solid. In addition to the reactivity of the active mass involved and the oxygen transfer capacity of the oxygen-carrying solid (active mass + binder / support), which influence the dimensioning of the reactors and, in the case of bed technology circulating fluidized, on the particle circulation rates, the lifetime of the particles in the process has a preponderant impact on the operating cost of the process, particularly in the case of the circulating fluidized bed process.
In fact, in the case of the circulating fluidized bed method, the attrition rate of the particles makes it necessary to compensate for the loss of solid oxygen-carrying solid in the form of fines, typically particles of the solid oxygen-carrying diameter of less than 40 pm, by solid carrying new oxygen. The rate of renewal of the oxygen-carrying solid therefore strongly depends on the mechanical resistance of the particles as well as on their chemical stability under the conditions of the process, which includes numerous successive oxidation / reduction cycles.
In general, the performances of the oxygen-carrying solids reported in the literature are satisfactory in terms of oxygen transfer capacity and reactivity with the various hydrocarbons tested (Adanez, J., Abad, A.,
Garcia-Labiano, F., Gayan, P. & de Diego, L.F., Progress in Chemical Looping Combustion and Reforming technologies, Progress in Energy and Combustion Science, 38 (2), (2012) 215-282). However, in most publications, a test duration that is too short and / or the absence of in-depth characterization of the particles after testing does not allow us to conclude as to the lifetime of the particles in the CLC process, although some authors have announced long service lives.
Some recent studies highlight the problem of the lifetime of the particles linked to the numerous redox cycles undergone by the particles in the CLC process.
For example, the problem of the lifetime of ilmenite particles (ore FeTiO ₃ ) was recently highlighted by P. Knutsson and C. Linderholm (Characterization of llmenite used as Oxygen Carrier in a 100 kW Chemical-Looping Combustor for Solid fuels, 3rd international Conference on Chemical Looping, September 9-11, 2014, Goteborg, Sweden). After a long-term test in a pilot in a circulating fluidized bed of 100kWth, the characterization by SEM of the aged particles shows that a high porosity has developed within the particles, which results in their disintegration in the form of fines which are eliminated. in gas / solid separation cyclones. The porosity of the particles of ilmenite ore increases sharply with redox cycles and results in their pulverization, potentially calling into question the suitability of this ore for the process, while the first studies on the use of ilmenite concluded that it good suitability for the CLC process. The increase in porosity observed by the careful characterization of the particles after testing is concomitant with the migration of ferrous and / or ferric ions by diffusion within the particles. According to the authors, a segregation of iron within the particles precedes its migration towards the surface, creating the porosity which results in the disintegration of the particles in the form of fines. The appearance of porosity constitutes the main mechanism for the formation of fine particles during the process, considerably limiting the lifetime of the particles, and therefore the potential advantage of the ore for CLC application. Indeed, the estimated lifetime of ilmenite particles is only around 200 hours ("Emerging CO ₂ capture Systems", JC Abanades, B. Arias, A. Lyngfelt, T. Mattisson, DE Wiley, H Li, MT Ho, E. Mangano, S. Brandani, Int. J. Greenhouse Gas Control 40 (2015), 126). The attrition phenomenon of the solid oxygen carrier is thus mainly due to a morphological evolution linked to the consecutive redox cycles undergone by the particles more than to shocks on the walls and between particles, usually considered as the main source of attrition in fluidized bed processes.
Wei et al. (“Continuous Operation of a 10 kWth Chemical Looping Integrated Fluidized Bed Reactor for Gasifying Biomass Using an Iron-Based Oxygen Carrier”. Energy Fuels 29, 233, 2015) also mention the conversion of synthetic particles of Fe ₂ O ₃ / AI ₂ O ₃ (70/30) in small grains (ie spraying of the particles into fines) after only 60 hours of combustion in a circulating fluidized bed.
L.S. Fan et al. (“Chemical-Looping Technology Platform”. AlChE J. 61, 2, 2015) claim that the absence of demonstration of the CLC process on an industrial scale is linked to the inadequacy of oxygen-carrying solids in terms of reactivity, recyclability, oxygen transfer capacity, mechanical strength and attrition resistance. According to these authors, the first studies on solid oxygen carriers did not realize the importance of the cationic and anionic migration mechanisms within the particles, which lead to phase segregation, the appearance of cavities or micropores, agglomeration, sintering, etc.
Patent application WO 2012/155059 discloses the use of oxygen-carrying solids consisting of an active mass (20 to 70% by weight), a primary support material of ceramic or clay type (5 to 70% by weight) , and a secondary support material (1 to 35% by weight), also of ceramic or clay type. Improved mechanical stability linked to the control of volume expansion is advanced for these oxygen-carrying solids. It is explained that a movement of diffusion of iron ions towards the outside of the particles causes the volume expansion of the particles, which leads to embrittlement of the particles. In the solid according to WO 2012/155059, the primary support material would make it possible to disperse the metallic active mass and prevent its agglomeration, preserving the redox activity, while the secondary support material would serve to reduce the speed of volume expansion by forming a phase stabilizing solid which would prevent iron migration to the surface.
The numerous studies relating to a metal oxide (active mass generally based on oxide of Cu, Ni, Co, Fe and / or Mn) on a support conclude that most of the formulations tested with the CLC process are suitable.
However, Forero et al. (CR Forero, P. Gayân, F. Garcia-Labiano, LF de Diego, A. Abad, J. Adânez, Int. J. Greenhouse Gas Control 5 (2011) 659-667) report a significant loss of copper oxide , probably due to the migration of the active phase towards the outside of the particles during the redox cycles. The copper on the surface is then removed in the fines by attrition. In addition, the porosity of the CuO / AI ₂ O ₃ particles increases with the number of cycles, and the aluminum matrix gradually cracks, resulting in the formation of fine particles. Adanez-Rubio et al. (Energy Fuels 2013 (27) 3918) report that the packed packed density of batches of CuO-based particles impregnated on different supports (TiO ₂ , SiO ₂ , MgAI ₂ O ₄ ) has decreased significantly, which can be attributed a significant increase in the porosity of the particles and means that the lifetime of these particles is limited.
The migration of the metal with the number of cycles is also encountered with the Fe ₂ O ₃ / AI ₂ O ₃ particles, as reported by LS Fan et al. (“Ionie diffusion in the oxidation of iron - effect of support and its implications to chemical looping applications”. Energy Environ. Sci., 4, 876, 2011).
Lyngfelt et al. performed a 1000h test with nickel-based particles (40% NiO / 60% NiAI ₂ O ₄ ) in a circulating fluidized bed installation with a power of 10kWth (Linderholm, C., Mattisson, T. & Lyngfelt , A., Long-term integrity testing of spray-dried particles in a 10-kW chemical-looping combustor using natural gas as fuel, Fuel, 88 (11), (2009) 2083-2096). The authors conclude that the particles have a lifespan of around 33,000 h, but a fairly high proportion of agglomerates is observed at the end of the test and part of the solid has adhered to the walls of the reactor. The presence of metallic nickel on the surface of the particles, due to the migration of nickel towards the outside, is probably at the origin of the formation of the agglomerates observed (Jerndal, E., Mattisson, T., Thijs, l., Snijkers, F. & Lyngfelt, A., Investigation of NiO / NiAI ₂ O ₄ oxygen carriers for chemical-looping combustion produced by spray-drying, International Journal of Greenhouse Gas Control, 4, (2010) 23). Such agglomerates represent a significant risk of accidental stopping of the CLC process. In addition, the characterization of the aged particles is insufficient to really conclude that this solid is of interest for CLC. Batch fluidized bed tests on particles of a similar carrier, carried out by the applicants, show a significant migration of nickel towards the periphery of the particles and the formation of fine particles (0.1 to 5 μm in size) consisting essentially of nickel on the surface of large particles. The particles tested are initially purely mesoporous.
The search for a solid oxygen carrier performing, in terms of oxygen transfer capacity, reactivity with the various hydrocarbon feedstocks likely to be treated, and mechanical resistance, therefore remains a primary objective for the development of the processes. redox in a chemical loop, such as
CLC.
Objectives and summary of the invention
The present invention aims to overcome the problems of the prior art set out above, and aims in general to provide an oxygen-carrying solid for a redox process in chemical loop which has a long lifetime during of its use in the process, in particular to reduce the investment and / or operating costs for such processes.
Thus, in order to achieve at least one of the abovementioned objectives, among others, the present invention proposes, according to a first aspect, a solid oxygen carrier in the form of particles for a redox process in chemical loop, comprising:
- an oxidation-reduction active mass constituting between 5% and 75% by weight of said oxygen-carrying solid, said oxidation-reduction active mass comprising a metal oxide or a mixture of metal oxides and being capable of exchanging oxygen under the redox conditions of said chemical loop oxidation-reduction process;
- A ceramic matrix within which is dispersed said active redox mass, said ceramic matrix constituting between 25% and 95% by weight of said oxygen-carrying solid, and said ceramic matrix comprising 100% by weight of at least one oxide having a melting temperature above 1500 ° C;
- a porosity such that:
the total pore volume of the oxygen-carrying solid, measured by mercury porosimetry, is between 0.05 and 1.2 ml / g,
- The total pore volume of the oxygen-carrying solid comprises at least 10% of macropores;
the size distribution of the macropores within the oxygen-carrying solid, measured by mercury porosimetry, is between 50 nm and 7 pm.
Preferably, the total pore volume of the oxygen-carrying solid is between 0.1 and 0.85 ml / g.
The total pore volume of the oxygen-carrying solid advantageously comprises at least 40% of macropores.
Preferably, the size distribution of the macropores within the oxygen-carrying solid is between 50 nm and 3 μm.
Preferably, the redox active mass comprises at least one metal oxide included in the list constituted by the oxides of Fe, Cu, Ni, Mn and Co, a perovskite having redox properties, preferably a perovskite of formula CaMnO ₃ , a metal aluminate spinel having redox properties, preferably a metal aluminate spinel of formula CuAI ₂ O ₄ or of formula CuFe ₂ O ₄ .
According to one embodiment of the invention, the active redox mass comprises at least one copper oxide.
Advantageously, said at least one oxide of the ceramic matrix has a melting temperature higher than 1700 ° C, and preferably higher than 2000 ° C.
Said at least one oxide of the ceramic matrix can be chosen from the list consisting of calcium aluminate of formula CaAI ₂ O ₄ , silica of formula SiO ₂ , titanium dioxide of formula TiO ₂ , perovskite of formula CaTiO ₃ , alumina of formula AI ₂ O ₃ , zirconia of formula ZrO ₂ , yttrium dioxide of formula Y ₂ 0 ₃ , barium zirconate of formula BaZrO ₃ , magnesium aluminate of formula MgAI ₂ O ₄ , the magnesium silicate of formula MgSi ₂ O ₄ , the lanthanum oxide of formula La ₂ O ₃ .
Advantageously, said at least one oxide of the ceramic matrix is silica, alumina, or a mixture of alumina and silica, and preferably is alumina.
Preferably, the particles have a particle size such that more than 90% of the particles have a size of between 50 μm and 600 μm.
According to a second aspect, the invention relates to a process for the preparation of an oxygen-carrying solid according to one of claims 1 to 11, comprising the following steps:
(A) the preparation of an aqueous suspension comprising an oxide or a mixture of precursor oxides of the ceramic matrix having a melting temperature above 1500 ° C, preferably above 1700 ° C, and even more preferably above 2000 ° C, said precursor oxide (s) forming grains of size between 0.1 pm and 20 pm, preferably between 0.5 pm and 5 pm, and more preferably between 1 pm and 3 pm;
(B) spray drying said suspension obtained in step (A) to form particles, said spray drying comprising spraying the suspension into a drying chamber using spraying means to form droplets , and the simultaneous contacting of said droplets with a hot carrier gas, preferably air or nitrogen, brought to a temperature between 200 ° C and 350 ° C;
(C) calcining the particles resulting from spray drying in step (B), said calcination being carried out in air and at a temperature between 400 ° C and 1400 ° C;
(D) optional screening of the calcined particles from step (C), by separation using a cyclone;
(E) the integration of an oxidation-reducing active mass according to a step e1) or a step e2) to produce the solid carrying oxygen in the form of particles:
e1) (i) impregnation of the particles resulting from step (C) with a precursor compound of an active redox mass, then (ii) drying of the impregnated particles followed (iii) by calcination;
e2) incorporation of the active redox mass during the preparation of the suspension in step (A).
According to one embodiment, step e1) comprises:
(i) impregnating the particles from step (C) with an aqueous or organic solution containing at least one soluble precursor compound of copper, nickel, cobalt, iron or manganese, preferably with an aqueous solution containing at least one precursor compound of the redox active mass chosen from the list consisting of nitrates of the following formulas: Cu (NO ₃ ) ₂ .xH ₂ O, Ni (NO ₃ ) ₂ .xH ₂ O, Co (N0 ₃ ) ₂ .xH ₂ 0, Fe (NO ₃ ) ₃ .xH ₂ O, Mn (NO ₃ ) ₂ .xH ₂ O.
Preferably, the impregnation (i) in step e1) is carried out in one or more successive steps, and preferably comprises intermediate steps of drying at a temperature between 30 ° C. and 200 ° C. and / or of calcination at a temperature between 200 ° C and 600 ° C when the impregnati® is carried out in several successive stages.
According to one embodiment, the drying (ii) in step e1) is carried out in air or in a controlled atmosphere, at a temperature between 30 ° C and 200 ° C, and preferably in air at a temperature between 100 ° C and 150 ° C.
According to one embodiment, the calcination (iii) in step e1) is carried out in air at a calcination temperature between 450 ° C and 1400 ° C, preferably between
600 ° C and 1000 ° C, more preferably between 7000 and 900 ° C, and is carried out for a period of 1 to 24 hours, and preferably for a period of 5 to 15 hours.
According to one embodiment, step e2) comprises (j) impregnating the grains of said precursor oxide (s) with the ceramic matrix with an aqueous or organic solution containing at least one soluble precursor compound of copper, nickel, cobalt , iron or manganese, preferably with an aqueous solution containing at least one precursor compound of the active redox mass chosen from the list consisting of nitrates of the following formulas: Cu (NO ₃ ) ₂ .xH ₂ O , Ni (NO ₃ ) ₂ .xH ₂ O, Co (N0 ₃ ) ₂ .xH ₂ 0, Fe (NO ₃ ) ₃ .xH ₂ O, Mn (NO ₃ ) ₂ .xH ₂ O, said impregnation being carried out before the suspension of said grains.
Alternatively, step e2) may comprise (jj) the addition of at least one precursor of the active redox mass, said precursor being a soluble compound of copper, nickel, cobalt, iron and / or manganese to the suspension prepared in step (A), and preferably a precursor compound of the active redox mass chosen from the list consisting of nitrates of the following formulas: Cu (NO ₃ ) ₂ .xH ₂ O, Ni (NO ₃ ) ₂ .xH ₂ O, Co (N0 ₃ ) ₂ .xH ₂ 0, Fe (NO ₃ ) ₃ .xH ₂ O, Mn (NO ₃ ) ₂ .xH ₂ O.
Alternatively, step e2) can comprise (dd) the addition to the suspension prepared in step (A) of grains of at least one metal oxide included in the list constituted by the oxides of Fe, Cu, Ni, Mn and Co, a perovskite having redox properties, preferably a perovskite of formula CaMnO ₃ , a metal aluminate spinel having redox properties, preferably a metal aluminate spinel of formula CuAI ₂ O ₄ or of formula CuFe ₂ O ₄ , said grains having a size between 0.1 pm and 20 pm, preferably between 0.5 pm and 5 pm, and more preferably between 1 pm and 3 pm, to form the active mass of oxido- reduction of the solid oxygen carrier.
According to one embodiment, in step A) at least one binder is added to the aqueous suspension intended to reinforce the cohesion of the particles obtained at the end of step (B), and / or to control the rheology of said suspension aqueous, said binder being an organic binder, preferably chosen from the list consisting of PEG, PVA, PA,
PVP, or an inorganic binder, preferably chosen from the list consisting of aluminum hydroxides, boehmite, diaspore, tetraethylorthosilicate, silicic acid, aluminosilicates and kaolin-type clays.
According to one embodiment, in step A) at least one pore-forming agent is added to the aqueous suspension intended to increase the macroporosity of the particles of the oxygen-carrying solid.
According to one embodiment, in step E), fines from the oxygen-carrying solid produced during the use of said oxygen-carrying solid are recycled in a chemical loop oxidation-reduction process.
According to a third aspect, the invention relates to a chemical loop redox process using an oxygen-carrying solid according to the invention or prepared according to the preparation process according to the invention.
Advantageously, the invention relates to a CLC process, preferably in which the oxygen-carrying solid is in the form of particles and circulates between at least one reduction zone and one oxidation zone both operating in a fluidized bed, the temperature in the reduction zone and in the oxidation zone being between 400 ° C and 1400 ° C, preferably between 600 ° C and 1100 ° C, and more preferably between 800 ° C and 1100 ° C.
Other objects and advantages of the invention will appear on reading the following description of examples of particular embodiments of the invention, given by way of nonlimiting examples, the description being given with reference to the appended figures described below. -after.
Brief description of the figures
FIGS. 1A, 1B, 1C and 1D relate to an oxygen-carrying solid according to example 2 (example not in accordance with the invention). FIG. 1A is a diagram giving information on the porosity of the oxygen-carrying solid. FIG. 1B is a diagram representing the conversion of methane as a function of the redox cycles in a CLC process using the solid carrying oxygen. Figure 1C is a diagram showing the particle size distribution of the oxygen-carrying solid before and after its use in a CLC process. Figure 1D is a scanning electron microscopy (SEM) image of a polished section of a sample of the oxygen-carrying solid after its use in a CLC process.
FIGS. 2A, 2B, 2C and 2D relate to an oxygen-carrying solid according to example 3 (example not in accordance with the invention). FIG. 2A is a diagram giving information on the porosity of the oxygen-carrying solid. FIG. 2B is a diagram representing the conversion of methane as a function of the oxidation-reduction cycles in a CLC process using the solid carrying oxygen. FIG. 2C represents in (a) a SEM photograph and in (b) a map of energy dispersive X-ray spectrometry (EDX) of the oxygen-carrying solid before its use in a CLC process. Figure 2D is a SEM image of a polished section of a sample of the oxygen-carrying solid after its use in a CLC process.
FIGS. 3A, 3B, 3C, 3D and 3E relate to an oxygen-carrying solid according to example 4 (example according to the invention). FIG. 3A is a diagram giving information on the porosity of the solid oxygen carrier before use in a CLC process. FIG. 3B is a SEM photograph in backscattered electrons on a polished section of the oxygen-carrying solid before its use in a CLC process. FIG. 3C is a diagram representing the conversion of methane as a function of the oxidation-reduction cycles in a CLC process using the solid carrying oxygen. Figure 3D is a diagram giving information on the porosity of the oxygen-carrying solid after use in a CLC process. FIG. 3E represents in (a) and (b) two SEM photographs of a polished section of a sample of the solid carrying oxygen after its use in a CLC process.
FIGS. 4A, 4B, 4C, 4D and 4E relate to an oxygen-carrying solid according to example 4 (example according to the invention). FIG. 4A is a diagram giving information on the porosity of the solid oxygen carrier before use in a CLC process. FIG. 4B is a SEM image in backscattered electrons on a polished section of the oxygen-carrying solid before its use in a CLC process. FIG. 4C is a diagram representing the conversion of methane as a function of the oxidation-reduction cycles in a CLC process using the solid carrying oxygen. FIG. 4D is a diagram giving information on the porosity of the oxygen-carrying solid after use in a CLC process. FIG. 4E represents in a SEM image in backscattered electrons of a polished section of a sample of the solid carrying oxygen after its use in a CLC process.
Description of the invention
The object of the invention is to provide an oxygen-carrying solid for a chemical loop oxidation-reduction process, such as a CLC process, but also for other chemical reduction oxidation-reduction processes on active mass such as a chemical loop reforming process (CLR with reference to the expression "Chemical
Looping Reforming) or a CLOU process (with reference to the expression "Chemical
Looping Oxygen Uncoupling ”).
The present invention also relates to the preparation and use of the oxygen-carrying solid in such processes.
The CLC processes generally use two separate reactors to effect on the one hand in a reduction reactor, the reduction of the active mass by means of a fuel, or more generally of a reducing gas, liquid or solid. The effluents from the reduction reactor mainly contain CO ₂ and water, allowing an easy capture of CO ₂ . On the other hand, in the oxidation reactor, the restoration of the active mass to its oxidized state by contact with air or any other oxidizing gas makes it possible to correlatively generate a hot effluent carrying energy and a flow of nitrogen. poor or nitrogen-free (if air is used).
In the present description, reference is made above all to the use of the oxygen-carrying solid in a CLC process in a circulating fluidized bed, but the oxygen-carrying solid according to the invention can also be used in any other type of process. 'oxidation-reduction in a chemical loop (CLC, CLR, CLOU) in a fixed, mobile or bubbling bed, or in a rotating reactor.
The solid oxygen carrier
The oxygen carrier comprises:
an active redox mass constituting between 5% and 75% by weight of the oxygen-carrying solid, preferably between 10% and 40% by weight, the redox active mass comprising a metal oxide or a mixture metal oxides and being capable of exchanging oxygen under the redox conditions of said oxidation-reduction process in a chemical loop;
a ceramic matrix within which the active redox mass is dispersed, the ceramic matrix constituting between 25% and 95% by weight of the oxygen-carrying solid, preferably between 60% and 90% by weight, and the ceramic matrix comprising 100% by weight of at least one oxide having a melting temperature greater than 1500 ° C., and preferably having a melting temperature greater than 1700 ° C., and even more preferably having a melting temperature greater than 2000 ° C.
By a ceramic matrix comprising 100% by weight of at least one oxide, it is meant that the matrix consists essentially of this oxide (or mixture of oxides), to within 1% by weight.
In addition to a ceramic matrix comprising at least one oxide having a melting temperature above 1500 ° C, and preferably a melting temperature above 1700 ° C, even more preferably a melting temperature above 2000 ° C, the carrier solid of oxygen, the invention has a particular porosity which, unexpectedly, makes it possible to limit the phenomenon of migration of the active mass within the particles of oxygen carrier. This initial texture significantly improves the lifetime of the particles in the chemical loop combustion process and is characterized in that:
- The total pore volume of the solid oxygen carrier Vtot, measured by mercury porosimetry, is between 0.05 and 1.2 ml / g;
- The total pore volume Vtot of the oxygen-carrying solid comprises at least 10% of macropores;
the size distribution of the macropores within the oxygen-carrying solid, measured by mercury porosimetry, is between 50 nm and 7 pm.
Note that according to the IUPAC nomenclature, we speak of micropores for pores whose size is less than 2 nm, mesopores for pores whose size is between 2 and 50 nm, and macropores for pores of size greater than 50 nm.
By initial texture is meant the texture before any use in a chemical loop oxidation-reduction process such as CLC.
The total pore volume of the solid is measured by mercury porosimetry, more precisely the measurement relates to the volume of mercury injected when the pressure exerted increases from 0.22 MPa to 413 MPa.
The total pore volume Vtot of the oxygen-carrying solid is preferably between 0.1 and 0.85 ml / g.
Preferably, the total pore volume Vtot of the particles is constituted for at least 40% by macropores. The rest of the pore volume can be made up of microporosity or mesoporosity in any proportion whatsoever.
The size distribution of the macropores within the particles, measured by mercury porosimetry, is more preferably between 50 nm and 3 μm, and even more preferably between 200 nm and 1 μm.
The reason (s) for which this initial macroporous texture of the oxygen-carrying solid minimizes the migration of the active mass within the particles is not yet explained. Without being bound to a particular theory, the inventors attribute this phenomenon, at least partially, to the fact that the diffusional limitations, usually reported for mesoporous particles according to the prior art, are largely minimized due to the particularly open texture of the particles according to the invention. The gases can easily access the active mass dispersed within the ceramic matrix, limiting the mobility of the active mass due to the concentration gradients, particularly during the oxidation of the particles. It is indeed known that metal cations generally migrate through the primary oxide layer formed during the oxidation of a reduced metal particle (S. Mrowec, Z. Grzesik, "Oxidation of nickel and transport properties of nickel oxide >>. J. Phys. Chem. Solids, 64, 1651, 2004), because the diffusion rate of metal cations in the oxide layer is higher than that of the oxygen anion (O ² j.
The matrix in. ceramic,
The ceramic matrix essentially consists of at least one oxide, or a mixture of oxides, having a melting temperature above 1500 ° C, preferably above 1700 ° C and more preferably above 2000 ° C, which is preference chosen from the list consisting of calcium aluminate CaAI ₂ O ₄ , silica SiO ₂ , titanium dioxide TiO ₂ , perovskite CaTiO ₃ , alumina AI ₂ O ₃ , zirconia ZrO ₂ , dioxide dioxide yttrium Y ₂ 0 ₃ , barium zirconate BaZrO ₃ , magnesium aluminate MgAI ₂ O ₄ , magnesium silicate MgSi ₂ O ₄ , lanthanum oxide La ₂ O ₃ .
Calcium aluminate CaAI ₂ O ₄ has a melting temperature above 1500 ° C, silica SiQ>, titanium dioxide TiO ₂ , perovskite CaTi0 ₃ have a melting temperature above 1700 ° C, and alumina A [O ₃ , zirconia ZrO ₂ , yttrium dioxide Y ₂ 0 ₃ , barium zirconate BaZrO ₃ , magnesium aluminate MgAI ₂ O ₄ , magnesium silicate MgSi ₂ O ₄ , and oxide lanthanum La ₂ O ₃ have a melting temperature above 2000 ° C.
Preferably, said oxide of the ceramic matrix is silica, alumina, or a mixture of alumina and silica.
In the present description, the term oxide covers a mixed oxide, that is to say a solid resulting from the combination of oxide ions O ^2- with at least two cationic elements (for example calcium aluminate CaAI ₂ O ₄ or magnesium aluminate
MgAI ₂ O ₄ ). By mixture of oxides is meant at least two separate solid compounds each being an oxide.
The oxide (s) of the ceramic matrix having a high melting temperature, greater than 1500 ° C., their use is a / antageuse within the framework of the oxidation-reduction processes in chemical loop such as CLC where the temperature reached by the particles of the oxygen carrier is higher than that of the fluidizing gas, sometimes up to 120 ° C (Guo, XY; Sun, YL; Li, R .; Yang F. "Experimental investigations on temperature variation and inhomogeneity in a packed bed CLC reactor of large particles and low aspect ratio >>. Chem.Eng.Sci. 107, 266, 2014). The higher the melting temperature of the oxide or mixture of oxides constituting the ceramic matrix, the more the said ceramic matrix is resistant to sintering. In fact, the temperatures of Hüttig (T _H ) and Tammann (T _T ), considered as indicative of the temperature from which the sintering of a phase can take place, are directly proportional to the melting temperature. They are expressed by the semi-empirical equations T _H = 0.33 T _f and T _T = 0.5.T _f (in Kelvin). When T _H is reached, the atoms become mobile on the surface, and when T _T is reached, the crystal lattices begin to be able to move (A. Cao, R. Lu, G. Veser. Stabilizing metal nanoparticles for heterogeneous catalysis. PHYSICAL CHEMISTRY CHEMICAL PHYSICS 12 13499-13510, 2010).
Table 1 below lists the examples of oxides that can make up the ceramic matrix of the oxygen-carrying solid, and indicates their melting temperature "T fusion", of Hüttig (T _H ) and of Tammann (T _T ) ,
Formula T fusion (° C) Th (° C) T _T (° C) C3AI2O4 1605 290 666 Sio ₂ 1713 323 720 Ta ₂ O ₅ 1785 344 756 TiO ₂ 1843 362 785 Mg ₂ SiO ₄ 1898 378 813 C3TIO3 1980 403 854 AI2O3 2072 431 900 SrTiO ₂ 2080 433 904 MgAI ₂ O ₄ 2135 449 931 Cs ₂ 03 2230 478 979 The ₂ O ₃ 2305 500 1016 CeO ₂ 2400 529 1064 Y ₂ O ₃ 2425 536 1076 Sc2O ₃ 2485 554 1106 BaZrO ₃ 2500 559 1114 ZrO ₂ 2715 623 1221
Table 1
According to the invention, the ceramic matrix can be obtained from the treatment of solid particles obtained by a spray drying technique of an aqueous suspension of oxide (s) of specific size.
The oxygen-carrying solid is obtained by integrating the redox active mass into the ceramic matrix, either from the stage of formation of the aqueous suspension of ceramic precursor oxide (s) or subsequently by impregnation of particles 10 of the ceramic matrix.
The preparation of the solid oxygen carrier according to the invention is detailed further on in the description.
The active mass c [xydp-Réductjpn
The oxygen-carrying solid according to the invention comprises an active redox mass which comprises, and is preferably constituted by, at least one metal oxide included in the list constituted by the oxides of Fe, Cu, Ni, Mn and Co, a perovskite exhibiting redox properties, preferably a perovskite of formula
CaMnO ₃ , a metal aluminate spinel having redox properties, for example a metal aluminate spinel of formula CuAI ₂ O ₄ or of formula CuFe ₂ O ₄ .
Preferably, the redox active mass comprises at least one copper oxide, preferably of formula CuO, and is more preferably constituted by at least one copper oxide, preferably of formula CuO.
According to the invention, the oxygen-carrying solid advantageously has an active mass dispersed within the ceramic matrix, typically an initial distribution of the relatively homogeneous initial active mass, and the migration of the active mass within the particles of the carrier solid. oxygen is minimized during the redox cycles of the oxidation-reduction process in a chemical loop, as illustrated by a few examples later in the description.
The redox active mass is capable of exchanging oxygen under the redox conditions of the redox chemical loop process. The active mass is reduced according to the reaction (1) already described above, during a reduction step in contact with a hydrocarbon feed, and is oxidized according to the reaction (2) or (3) already described above, during an oxidation step in contact with an oxidizing gas.
The oxygen storage capacity of the redox active mass is advantageously, depending on the type of material, between 1% and 15% by weight. Advantageously, the quantity of oxygen effectively transferred by the metal oxide is between 1 and 3% by weight, which makes it possible to use only a fraction of the oxygen transfer capacity.
Form dgsolidgpprteurdjpxygène
The oxygen-carrying solid according to the invention is preferably in the form of particles, which can be fluidized in the oxidation-reduction process in chemical loop, in particular be implemented in a circulating fluidized bed. They can be fluidizable particles (fluidizable powder, generally called "fluidizable carrier" in English) belonging to groups A, B or C of the Geldart classification (D. Geldart. "Types of gas fluidization >>. Powder Technol 7 (5), 285-292, 1973), and preferably the particles belong to group A or group B of the Geldart classification, and preferably to group B of the Geldart classification.
Preferably, the particles of the oxygen-carrying solid have a particle size such that more than 90% of the particles have a size between 50 μιτι and
600 μm, more preferably a particle size such that more than 90% of the particles have a size of between 80 μm and 400 μm, even more preferably a particle size such that more than 90% of the particles have a size of between 100 μm and 300 μm, and even more preferably a particle size such that more than 95% of the particles have a size of between 100 μm and 300 μm.
Preferably, the particles of the oxygen-carrying solid have a grain density between 500 kg / m ³ and 5000 kg / m ³ , preferably a grain density between 800 kg / m ³ and 4000 kg / m ³ , and even more preferably a grain density of between 1000 kg / m ³ and 3000 kg / m ³ .
The particles of the oxygen-carrying solid are preferably substantially spherical.
The particle size distribution and morphology for use in another type of chemical loop process (CLC, CLR, CLOU) in a fixed bed, in a moving bed or in a rotating reactor are adapted to the process envisaged. For example, in the case of the use of the solid oxygen carrier in a process using a fixed bed or rotating reactor technology, the preferred particle size is greater than 400 μm, in order to minimize the pressure losses in the reactor (s), and the particle morphology is not necessarily spherical. The morphology is dependent on the mode of shaping, for example in the form of extrudates, balls, monoliths or particles of any geometry obtained by grinding larger particles. In the case of shaping of the monolith type, the solid oxygen carrier, in the form of particles, is deposited on the surface of the channels of ceramic monoliths by the coating methods known to those skilled in the art. , or else the monolith itself consists of the particles according to the invention.
The particle size can be measured by laser granulometry.
Obtaining particles of the oxygen carrier in the desired size range requires a shaping step from smaller grains, the size of which is between 0.1 and 20 μm, preferably between 0.5 and 5 pm, and more preferably between 1 and 3 pm. The shaping can be carried out according to all the techniques known to those skilled in the art making it possible to obtain particles, such as extrusion, compacting, wet or dry granulation ("wet or dry granulation"). in English), for example agglomeration on a granulating plate or granulating drum, freeze-drying ("freeze granulation" in English), or by coagulation techniques of drops ("oil drop" in English), and preferably according to a spray drying technique, agglomeration on a granulating plate or granulating drum, making it possible to obtain particles of spherical shape.
A sieving and / or screening step (classification or separation, for example by means of a cyclone) can also be carried out in order to select the particles of the desired particle size.
Preparation of the solid oxygen carrier
The solid oxygen carrier can be prepared according to a process comprising the following steps:
Step (A): preparation of a suspension of precursor oxide (s) of a ceramic matrix
Step (A) involves the preparation of an aqueous suspension of oxide or a mixture of oxides, said solution having rheological characteristics suitable for pumping and spraying. The oxide (s) form grains whose size is between 0.1 μm and 20 μm, preferably between 0.5 μm and 5 μm, and more preferably between 1 μm and 3 μm.
The oxide or mixture of oxides are the precursors of the ceramic matrix of the oxygen-carrying solid and have a melting temperature above 1500 ° C, preferably above 1700 ° C, and even more preferably above 2000 ° vs.
These components are preferably chosen from the list consisting of calcium aluminate of formula CaAI ₂ O ₄ , silica of formula SiO ₂ , titanium dioxide of formula TiO ₂ , perovskite of formula CaTiO ₃ , alumina of formula AI ₂ O ₃ , zirconia of formula ZrO ₂ , yttrium dioxide of formula Y ₂ 0 ₃ , barium zirconate of formula BaZrO ₃ , magnesium aluminate of formula MgAI ₂ O ₄ , magnesium silicate of formula MgSi ₂ O ₄ , the lanthanum oxide of formula La ₂ O ₃ .
One or more organic and / or inorganic binders can be added to the suspension in order to adjust and control the rheology of the suspension and to ensure the cohesion of the particles which are obtained at the end of the 'shaping step, before consolidation by calcination in a later step.
The organic binder (s) of variable molar mass can be chosen from polyethylene glycol (PEG), polyvinyl alcohol (PVA), polyacrylate (PA), polyvinylpyrrolidone (PVP), etc. They can be added at a level of 0.5% to 6% by weight relative to the mass of oxide (s) in suspension.
The inorganic binder (s) can be chosen from aluminum hydroxides (bayerite, gibbsite, nordstrandite), boehmite, diaspore, tetraethylorthosilicate, silicic acid, aluminosilicates and kaolin-type clays, etc.
They can be added up to 5% to 30% by weight relative to the mass of oxide (s) in suspension.
One or more blowing agents intended to increase the macroporosity of the particles can also be added to the suspension. Preferably, when such agents are added to the solution, their amount is preferably less than 25% by weight relative to the mass of oxide (s) in suspension. Such agents are typically burnable organic compounds, such as starch, cellulose, polymers such as polypropylene, latex, poly (methyl methacrylate) (PMMA).
Step (B): spray drying
During this step, the suspension obtained in step (A) is spray-dried: the suspension is sprayed into fine droplets in a drying chamber using spraying means, for example using a pneumatic (bi-fluid) or hydraulic (monofluid) spray nozzle, and these droplets are simultaneously brought into simultaneous contact with a hot carrier gas, preferably air or nitrogen, brought to a temperature between 200 and 350 ° C. The hot carrier gas is introduced with a co-current flow (ceiling mode) or a mixed flow (fountain mode) allowing the evaporation of the solvent and obtaining spherical particles at the desired particle size.
This step advantageously allows the formation of particles of desired particle size. Preferably, this step is carried out so as to produce particles with the following particle size: more than 90% of the particles have a size between 50 and 600 μm, preferably more than 90% of the particles have a size between 80 μm and 400 pm, even more preferably more than 90% of the particles have a size between 100 pm and 300 pm, and even more preferably more than 95% of the particles have a size between 100 pm and 300 pm.
A subsequent optional screening step (D) can be carried out in order to obtain the desired particle size, described below.
Step (C): Calcination of the spray-dried particles
The particles resulting from spray drying in step (B) are calcined in air at a temperature between 400 ° C and 1400 ° C, preferably between 600 ° C and 1200 ° C, and very preferably between 650 and 900 ° vs. This calcination step has an impact on the mechanical behavior of the particles.
It is possible to produce a temperature rise ramp of between 1 ° C / min and 50 ° C / min, and preferably between 5 ° C / minet 20 ° C / min, to reach the given calcination temperature, especially when the integration of the redox active mass into the oxygen-carrying solid is carried out according to step e2) j) described below (prior impregnation with the active mass precursor of the oxide grains which are suspension in step (A)).
Step (D): optional screening of particles
Screening can be carried out at the end of the calcination step (C) aimed at selecting the particles in a desired size range. The screening can be carried out by separation of the particles by means of a cyclone, or any other means of separation.
Step (E): integration of the active redox mass
Step (E) includes either step e1) or step e2). Step (E) makes it possible to associate the redox active mass with the ceramic matrix to produce the oxygen-carrying solid in the form of particles according to the invention.
Step, e, 1J.imp.réçtnation ,, drying, and, calcination ,, particles, already, matrix, ceramic
According to this step e1), the calcined particles obtained at the end of step (C), and optionally screened at the end of step (D), are (i) impregnated with an aqueous or organic solution containing at minus a soluble precursor compound of copper, nickel, cobalt, iron or manganese.
Preferably, the impregnation is carried out with an aqueous solution containing at least one precursor compound of the active redox mass chosen from the list constituted by the nitrates of the following formulas: Cu (NO ₃ ) ₂ .xH ₂ O, Ni (NO ₃ ) ₂ .xH ₂ O, Co (N0 ₃ ) ₂ .xH ₂ 0, Fe (NO ₃ ) ₃ .xH ₂ O, Mn (NO ₃ ) ₂ .xH ₂ O.
Advantageously, the copper nitrate Cu (NO ₃ ) ₂ .xH ₂ O is chosen to carry out this impregnation, in order to obtain an oxidation-reducing active mass of copper oxide (s), for example a copper oxide of formula CuO, to form the solid oxygen carrier.
The amount of precursor of the active redox mass used for the impregnation step is chosen so that the active redox mass constitutes between 5% and 75% by weight of the solid carrying oxygen, preferably constitutes between 10% and 40% by weight of the solid carrying oxygen.
The impregnation can be carried out in one or more successive stages.
If the impregnation is carried out in several successive stages, intermediate stages of drying at a temperature between 30 ° C and 200 ° C and / or calcination at a temperature between 200 ° C and 600 ° C are preferably carried out.
The impregnated particles are then (ii) dried, for example in an oven, and preferably in air or in a controlled atmosphere (controlled relative humidity, under nitrogen). This drying is carried out at a temperature between 30 ° C and 200 ° C.
More preferably, this drying is carried out in air at a temperature between 100 ° C and 150 ° C.
Finally, the impregnated and dried particles are then (iii) calcined. This second calcination step (the first being that of step (C)) results in the oxygen-carrying solid in the form of particles according to the invention.
This calcination (iii) is preferably carried out in air between 450 ° C. and 1400 ° C., more preferably between 600 ° C. and 1000 ° C., and more preferably between 700 ° C. and 900 ° C.
This calcination can be carried out for a period of 1 to 24 hours, and preferably for a period of 5 to 15 hours.
Advantageously, a temperature rise ramp is applied between 1 ° C / min and 50 ° C / min, and preferably between SC / min and 20 ° C / min, to reach the given calcination temperature. The duration to implement this temperature ramp is not included in the ranges of calcination duration indicated above.
This calcination allows the formation of the redox active mass dispersed within the ceramic matrix.
It also appears that this calcination step (iii) has a limited impact on the initial macroporous structure of the particles, and all the more limited when the calcination is carried out at a temperature of between 700 ° C. and 900 ° C. A small increase in the diameter of the macropores and a small decrease in the total pore volume can be observed.
Step e2)
According to step e2), and as an alternative to what is carried out in step e1), the redox active mass is associated with the ceramic matrix during the preparation of the suspension in step (A) .
The incorporation of the redox active mass can then be done according to one of the following three steps:
(j) impregnation with at least one soluble precursor compound of copper, nickel, cobalt, iron or manganese of the grains of the oxide, of one of the oxides or of all the oxides used to prepare the suspension for l 'step (A). Said precursor compound of the active mass, soluble in water, can be chosen from the list constituted by the nitrates of the following formulas: Cu (NO ₃ ) ₂ .xH ₂ O, Ni (NO ₃ ) ₂ .xH ₂ O, Co (N0 ₃ ) ₂ .xH ₂ 0, Fe (NO ₃ ) ₃ .xH ₂ O, Mn (NO ₃ ) ₂ .xH ₂ O. Impregnation is carried out before the grains are suspended. Advantageously, a soluble copper precursor, and preferably copper nitrate Cu (NO ₃ ) ₂ .xH ₂ O, is chosen to carry out this impregnation, in order to obtain an oxidation-reducing active mass of oxide (s) copper, for example a copper oxide of formula CuO, to form the solid carrying oxygen. A drying step followed by a calcination step, as described in step e1) (ii) and (iii) can be carried out following this impregnation (j).
(jj) addition of at least one soluble precursor of copper, nickel, cobalt, iron and / or manganese to the suspension prepared in step (A). Advantageously, the soluble compound is chosen from the list constituted by the nitrates of the following formulas: Cu (NO ₃ ) ₂ .xH ₂ O, Ni (NO ₃ ) ₂ .xH ₂ O, Co (N0 ₃ ) ₂ .xH ₂ 0 , Fe (NO ₃ ) ₃ .xH ₂ O, Mn (NO ₃ ) ₂ .xH ₂ O. Preferably the precursor chosen is a soluble copper compound, more preferably copper nitrate Cu (NO ₃ ) ₂ . xH ₂ O.
(ddd) addition to the suspension prepared in step (A) of at least one oxide of copper, nickel, cobalt, iron, manganese, a perovskite having redox properties (for example CaMnO ₃ ), a metallic aluminate spinel having redox properties (for example CuFe ₂ O ₄ , CuAI ₂ O ₄ ), or any other compound capable of exchanging oxygen under the redox conditions of the oxidation-reduction process in chemical loop such as than the CLC. These precursors of the active mass added to the suspension prepared in step (A) are solids in the form of grains, of size between 0.1 pm and 20 pm, preferably between 0.5 pm and 5 pm , and more preferably between 1 pm and 3 pm. Preferably, a copper oxide is added to the suspension prepared in step (A).
The preparation of the solid oxygen carrier according to the invention can comprise the recycling in step E) of fines from the oxygen carrier produced during its use in a redox process in a chemical loop such as CLC , for example by adding during step (dd) in the suspension prepared in step (A) of less than 10% by weight of fines relative to the total oxide content (s) of the suspension. The recycled fines consist of a mixture of the active mass and the ceramic matrix, the size of which is less than 40 μm. A step of grinding the fines is therefore necessary to achieve a size distribution of the fine particles of between 0.1 pm and 20 pm, preferably between 0.5 pm and 5 pm, and more preferably between 1 pm and 3 pm.
Use of the solid oxygen carrier
The oxygen-carrying solid is intended for use in a chemical loop redox process.
The invention thus relates to a redox process in a chemical loop using the oxygen-carrying solid as described, or prepared according to the preparation process as described.
Advantageously, the oxygen-carrying solid described is used in a CLC process for a hydrocarbon feed, in which the oxygen-carrying solid is in the form of particles and circulates between at least one reduction zone and one oxidation zone all operating both in a fluidized bed.
The temperature in the reduction zone and in the oxidation zone is between 400 ° C and 1400 ° C, preferably between 600 ° C and 1100 ° C, and even more preferably between 800 ° C 1100 ° C.
The hydrocarbon feedstock treated can be a solid, liquid or gaseous hydrocarbon feedstock: gaseous fuels (e.g. natural gas, syngas, biogas), liquids (e.g. fuel oil, bitumen, diesel, gasoline etc.), or solids (e.g. : coal, coke, pet-coke, biomass, oil sands, etc.).
The operating principle of the CLC process in which the oxygen-carrying solid described is used is as follows: a reduced oxygen-carrying solid is brought into contact with an air flow, or any other oxidizing gas, in an area reaction called air reactor (or oxidation reactor). This results in a depleted air flow and a flow of re-oxidized oxygen-carrying solid particles. The flow of oxidized oxygen carrier particles is transferred to a reduction zone called a fuel reactor (or reduction reactor). The flow of particles is brought into contact with a fuel, typically a hydrocarbon feed. This results in a combustion effluent and a reduced flow of oxygen carrier particles. The CLC installation can include various equipment for heat exchange, pressurization, separation or any recirculation of material around the air and fuel reactors.
In the reduction zone, the hydrocarbon charge is brought into contact, preferably cocurrently, with the oxygen-carrying solid in the form of particles comprising the redox active mass in order to achieve the combustion of said charge by reduction of the redox active mass. The redox active mass M _x O _y , M representing a metal, is reduced to the state M _x Oy. _2n . _{m / 2} , via the hydrocarbon feedstock C _n H _m , which is correlatively oxidized to CO ₂ and H ₂ O, according to reaction (1) already described, or optionally in a CO + H ₂ mixture according to the proportions used . The combustion of the charge in contact with the active mass is carried out at a temperature generally between 400 ° C and 1400 ° C, preferably between 600 ° C and 1100 ° C, and more preferably between ®0 ° C and 1100 ° C. The contact time varies depending on the type of fuel charge used. It typically varies between 1 second and 10 minutes, for example preferably between 1 and 5 minutes for a solid or liquid charge, and for example preferably from 1 to 20 seconds for a gaseous charge.
A mixture comprising the gases from the combustion and the particles of the oxygen-carrying solid is discharged, typically at the top of the reduction zone. Gas / solid separation means, such as a cyclone, make it possible to separate the combustion gases from the solid particles of the oxygen carrier in their most reduced state. These are sent to the oxidation zone to be re-oxidized, at a temperature generally between 400 ° C and 1400 ° C, preferably between 600 ° C and 1100 ° C, and more preferably between S) 0 ° C and 1100 ° C.
In the oxidation reactor, the active mass is restored to its oxidized state M _x O _y in contact with air, according to reaction (2) already described (or according to reaction (3) if the oxidizing gas is H ₂ 0), before returning to the reduction zone, and after being separated from the oxygen-depleted air discharged at the top of the oxidation zone 100.
The active mass, passing alternately from its oxidized form to its reduced form and vice versa, describes a redox cycle.
The oxygen-carrying solid described can also be used in another oxidation-reduction process in a chemical loop such as a CLR process or a CLOU process.
The technology used in the oxidation-reduction process in a chemical loop is preferably that of the circulating fluidized bed, but is not limited to this technology, and can be extended to other technologies such as that of the fixed, mobile or bubbling bed. , or a rotating reactor.
Examples
The advantage of the oxygen-carrying solids according to the invention in the chemical loop processes, in particular CLC, in particular the minimization of the migration of the active mass within the particles during the redox cycles, is explained through the examples. 1 to 5 below.
Examples 2 and 3 relate to oxygen-carrying solids not in accordance with the invention. Examples 4 and 5 relate to oxygen-carrying solids in accordance with the invention.
Example 1 Aging test for oxygen-carrying solids in a batch fluidized bed
The aging of the oxygen-carrying solids in a batch fluidized bed was carried out in a unit consisting of a quartz reactor, an automated system for supplying the reactor with gas and a system for analyzing the gases leaving the reactor.
This aging test approximates the conditions for using the oxygen-carrying solid in a chemical loop redox process, in particular chemical redox combustion.
The gas distribution (CH ₄ , CO ₂ , N ₂ , air) is ensured by mass flowmeters. For safety reasons, a nitrogen sweep is carried out after each reduction and oxidation period.
The height of the quartz reactor is 30 cm, with a diameter of 4 cm in its lower part (24 cm high), and 7 cm in its upper part. A quartz frit is placed at the bottom of the reactor to ensure gas distribution and good fluidization of the particles. Another sinter is placed in the upper part of the reactor to avoid loss of fines during the test. The reactor is heated using an electric oven. Part of the gas leaving the reactor is pumped to the gas analyzers, cooled to condense most of the water formed during the reduction and then dried using calcium chloride. The gas concentrations are measured using non-dispersive infrared analyzers for CO, CO ₂ and CH ₄ , a paramagnetic analyzer for oxygen, and a TCD detector for hydrogen.
Standard test conditions: 100 grams of particles are introduced into the quartz reactor and then heated to 900 ° C under a flow of air (60 Nl / h). When the bed temperature is stabilized at 900 ° C in air, 250 cycles come out performed according to the following steps:
1- Nitrogen sweeping (60 Nl / h)
2- Injection of a CH ₄ / CO ₂ mixture (30 NI / h / 30 Nl / h) (reduction of particles)
3- Nitrogen sweeping (60 Nl / h)
4- Air injection (60 Nl / h) (particle oxidation)
The conversion of the oxygen-carrying solid (quantity of oxygen provided by the oxygen-carrying solid to carry out the conversion of methane, expressed in% by weight of the oxidized oxygen carrier) is calculated from the gas conversion data, and the reduction time (step 2 of the cycle) is adjusted after the first cycle so that the oxygen-carrying solid releases about 2% by weight of oxygen (relative to the oxidized mass of oxygen-carrying solid introduced) each time reduction cycle. The oxidation time (step 4 of the cycle) is sufficient to completely re-oxidize the particles (15 min).
The particle size distribution was measured using a Malvern particle size analyzer, using Fraunhofer's theory.
Mercury porosimetry measurements were performed on the device
Autopore IV marketed by Micromeritics, considering a surface tension of mercury of 485 dyn / cm and a contact angle of 140 °. The minimum pore size measurable by mercury porosimetry is 3.65 nm.
The nitrogen adsorption isotherms were carried out on the ASAP 2420 device sold by Micromeritics.
Example 2 Solid CuO / Alumina Oxygen Carrier
According to this example 2, an oxygen-carrying solid is formed from alumina as a support matrix for an active mass of oxidation-reduction of copper oxide (s).
The alumina used for this example is Puralox SCCa 150-200 sold by Sasol. The particle size distribution of the aluminum support indicates Dv10 = 104 pm, Dv50 = 161 pm and Dv90 = 247 pm. The pore volume of the particles measured by mercury porosimetry is 0.450 ml / g, and the pore size distribution is between 5 and 15 nm, centered on 9 nm. The macroporous volume of the support measured by mercury porosimetry is 0.007 ml / g (1.5% of the total pore volume).
The Puralox nitrogen adsorption isotherm allows to measure a specific surface of 199 m ² / g, a microporous volume (pores <2nm) zero and a mesoporous volume (2nm <pores <50 nm) of 0.496 ml / g.
233 g of Puralox alumina were impregnated using the dry impregnation method, with 96.5 g of copper nitrate trihydrate dissolved in the necessary volume of demineralized water. After drying at 120 ° C and calcination at 850 ° C for 12 hours, a solid containing 12% by mass of CuO is obtained; the crystallographic phases detected by XRD are γ-ΑΙ2Ο3 and CuO. The distribution of copper within the particles is homogeneous.
The pore volume of the particles of the solid obtained, measured by mercury porosimetry, is 0.367 ml / g, of which 0.015 ml / g (or 4% of the total pore volume measured by mercury porosimetry) is due to the macroporosity. The pore size distribution is between 5 and 20 nm and centered on 11.25 nm, as visible in the diagram in FIG. 1A representing the volume of mercury injected Vi (ml / g) in the porosity, as well as the dV / dD ratio (derived from (volume Hg introduced / pore size), giving information on the pore size distribution), as a function of the pore diameter (nm), for the oxygen-carrying solid according to this example . The particles are therefore essentially mesoporous.
The nitrogen adsorption isotherm of the oxygen-carrying solid according to this example makes it possible to measure a specific surface of 135 m ² / g, a microporous volume (pores <2nm) zero and a mesoporous volume (2nm <pores <50 nm) of 0.404 ml / g.
The solid oxygen carrier according to this example was aged under the conditions described in example 1.
FIG. 1B is a diagram representing the normalized conversion rate Xc of methane as a function of the number N of redox cycles in a CLC process using the solid oxygen carrier according to example 2.
Methane conversion is around 98% at the start of the test, it increases until it reaches 100%, then a gradual deactivation is observed after the hundredth cycle. The conversion then stabilizes around 95%.
It should be noted that the nature of the active mass used (CuO) causes the appearance of oxygen during the nitrogen sweeping step. The particles can therefore be used interchangeably in a CLC or CLOU type process.
After testing, the sample underwent very significant attrition, almost all of the particles having a size less than 100 μm, as is clearly visible in the diagram in FIG. 1C, representing the distribution of the size of the particles. (pm) of the oxygen-carrying solid according to this example before (curve 10) and after (curve 11) its use in a CLC process, that is to say before and after the aging test according to example 1.
SEM photographs on the polished section of the particles after the aging test according to Example 1, such as the photograph of FIG. 1D, show that the aluminum matrix constituting the particles has not withstood the 250 successive redox cycles. Most of the particles are effectively in the form of small fragments (a few tens of pm). In addition, additional SEM-EDX analyzes show that the finest particles observed (a few pm in size) consist almost exclusively of copper and oxygen.
This example shows that when the active mass is deposited on a purely mesoporous alumina, the accumulation of redox cycles results in the cracking of said aluminum matrix, and in the migration of copper within the aluminum matrix to form aggregates composed essentially of copper. The mechanical strength of the cracked ceramic matrix is then insufficient and the lifetime of the particles is drastically reduced.
Example 3: solid oxygen carrier CuO / Alumina siliceous with 5% SiO
According to this example 3, an oxygen-carrying solid is formed from siliceous alumina containing 5% of SiO ₂ as a support matrix for an active mass of oxidation-reduction of copper oxide (s) (CuO and CuAI ₂ O ₄ ).
The siliceous alumina used is Siralox 5 sold by Sasol and which contains 5% by weight of silica (SiO ₂ ). The particle size distribution indicates Dv ₁₀ = 60 pm, Dv ₅₀ = 89 pm and Dv _go = 131 pm. The pore volume measured by mercury porosimetry of the alumino-silica support is 0.549 ml / g, and the pore size distribution is between 5 and 30 nm, centered on 13 nm. The macroporous volume is 0.033 ml / g, or 6% of the total pore volume measured by mercury porosimetry.
The Siralox 5 nitrogen adsorption isotherm measures a specific surface of 173 m ² / g, a microporous volume (pores <2nm) zero and a mesoporous volume (2nm <pores <50 nm) of 0.601 ml / g.
240 g of silicate alumina were impregnated according to the dry impregnation method, with 109 g of copper nitrate trihydrate in aqueous solution. After drying at 120 ° C and calcination at 1000 ° C for 12 hours, a solid containing 13% by mass of CuO equivalent is obtained. The crystallographic phases detected by XRD are δ-ΑΙ ₂ Ο ₃ , θ-ΑΙ ₂ Ο ₃ , CuAI ₂ O ₄ and CuO. The SEM image of backscattered electrons (a) on the polished section and the EDX mapping (b) of FIG. 2C show that the copper is relatively well dispersed inside the particles, but less homogeneously than in Example 2.
The pore volume of the particles measured by mercury porosimetry is 0.340 ml / g, of which 0.029 ml / g (8.5%) is due to macroporosity. The pore size distribution is between 7 and 50 nm and centered on 15 nm, as visible in the diagram in FIG. 2A representing the volume of mercury injected Vi (ml / g) in the porosity, as well as the ratio dV / dD, as a function of the pore diameter (nm), for the oxygen-carrying solid according to this example. The particles after impregnation / calcination are essentially mesoporous.
The specific surface area measured by nitrogen adsorption is 77 m ² / g.
The oxygen-carrying solid according to example 3 was aged under the conditions described in example 1.
Methane conversion is stable, around 60% over the entire test (Figure 2B).
It should be noted that the nature of the active mass used (CuO) causes the appearance of oxygen during the nitrogen sweeping step. The particles can therefore be used interchangeably in a CLC or CLOU type process.
The partial conversion of methane compared to Example 2 is not a problem with respect to the CLC or CLOU process on an industrial scale, the total conversion of the fuel can be achieved by modifying the residence times of the particles. , gas velocities and / or inventory in the reduction reactor.
The size distribution of the particles after the aging test is similar to that of the material before the test, which indicates better mechanical resistance of the alumina-silica matrix compared to the particles on pure alumina.
However, it is observed that almost all of the copper initially dispersed within the particles has migrated towards the periphery of said particles to form porous zones containing essentially copper and a little aluminum, as can be seen on the SEM photograph of the Figure 2D. The mechanical resistance of these zones, although porous, is sufficient for the layers and aggregates formed to be still, in most cases, integral with the initial alumina-silica support under the conditions described in Example 1. It is however not possible to use this type of particles in a fluidized bed circulating on an industrial scale, where the higher gas velocities and the inevitable attrition by abrasion would lead to the rapid elimination of all the copper accumulated at the periphery.
According to the EDS measurements carried out, the zone of particles whose morphology is relatively unchanged compared to the initial silica-alumina consists mainly of alumina and contains only traces of copper, as well as almost all of the silicon. The presence of silicon in the ceramic matrix therefore makes it possible to stabilize said ceramic matrix. However, all of the copper initially well dispersed in the mesoporous matrix has migrated to the periphery of the particles during successive redox cycles.
Example 4 Solid Oxygen CuO / AbO ^ with Controlled Porosity
Method of making and preparing the solid oxygen carrier:
in Examples 4, 5 and 6, the particles of the oxygen-carrying solid are prepared from the synthesis of ceramic matrix particles of inert and stable oxide type serving as support for the active redox mass (supports not marketed). The particles of the solid oxygen carrier are prepared in the following manner:
Synthetic aluminosilicate materials are developed and formulated from aqueous suspensions which have been spray dried to result in microspheric solid particles, otherwise known as granules or microspheres.
The step of formulating the oxide support corresponds to adjusting the nature and the composition (content in percentage by mass) of the materials or precursors used in the starting suspension. Once the raw materials have been selected (in solid or liquid form depending on their physicochemical properties), they are then mixed with deionized water, acting as a solvent, in a stirred tank in order to obtain a fluid aqueous suspension and stable. This suspension is then transferred to a spray dryer where it is sprayed into fine droplets which, during the drying and evaporation phase of the water, will form spherical solid particles with a size close to a hundred μm.
Post-treatment stages follow such as the calcination or the screening of the oxide support then a stage of impregnation of an active metallic phase followed by a last calcination of the particles make it possible to obtain a usable oxygen-carrying material. in the oxidation-reduction process in a chemical loop such as CLC.
According to this example 4, an oxygen-carrying solid is formed comprising a ceramic alumina matrix within which is dispersed an active mass of oxidation-reduction of copper oxide (s).
The oxygen-carrying solid according to this example is obtained from an aqueous suspension of alumina, in particular using the spray drying technique.
The alumina used for this example is a powder resulting from a semi-industrial batch production which was obtained from an aqueous suspension of alumina by means of the spray drying process, as described above in the embodiment and preparation of the solid oxygen carrier.
The starting aqueous suspension is composed of 61% by weight of deionized water, 27.2% by weight of gamma alumina grains (y-AI ₂ O ₃ with particle size D _v50 = 2.8 pm, humidity of 5% wt), 3.8% by weight of boehmite grains (AIOOH with grain size D _V 50 = 45pm, humidity of 30% wt), 7.8% by weight of polyvinyl alcohol binder (PVA with
M ~ 4000g / mol, humidity of 80% by weight), and 0.2% by weight of nitric acid (HNO ₃ concentrated at 68% w / w).
In this formulation, the mass ratio relative to the mass of suspended oxide particles is 10.6% by weight for the inorganic binder (boehmite) and
5.2% by weight for the organic binder (PVA).
After a vigorous mixing step of the materials in a stirred tank for 30 minutes, the suspension is spray-dried: the homogenized suspension is pumped then sprayed into fine droplets, using a pneumatic nozzle positioned in part high of a drying chamber. Then, bringing the droplets into contact with a flow of air heated to 300 ° C. induces evaporation of the water and progressive drying, which makes it possible to obtain solid spherical particles collected at the bottom of the drying chamber. , and having a size between 30 pm and 200 pm.
These dry particles form a powder, which is then calcined for 4 hours in a muffle furnace at a temperature of 700 ° C., then which is screened between 125 and 315 μm to remove the finest particles.
The particles obtained constitute the final oxide support, and this final oxide material is composed of 100% by weight of alumina (AI ₂ O ₃ ).
The particle size distribution of the final oxide support indicates D _v10 = 58 pm, D _v50 = 159 pm and D _v90 = 278 pm. The pore volume measured by mercury porosimetry of the alumina support is 0.76 ml / g, and a bimodal pore size distribution is observed. The pore size distribution for the mesoporosity is between 5 and 50 nm (centered on 9.6 nm) and for the macroporosity is between 50 and 2800 nm (centered on 385 nm). The macroporous volume is 0.37 ml / g, or 49% of the total pore volume measured by mercury porosimetry.
200 g of this alumina are impregnated using the dry impregnation method, with 91.3 g of copper nitrate trihydrate dissolved in the necessary volume of demineralized water. After drying at 120 ° C and calcination at 850 ° C for 12 hours, a solid containing 13% by mass CuO equivalent is obtained
After calcination at 800 ° C for 12 hours, the X-ray diffraction shows that a copper aluminate (CuAI ₂ O ₄ ) substoichiometric in Cu is formed, as well as a little
CuO.
The size distribution of the particles of the oxygen-carrying solid measured by laser diffraction indicates Dv ₁₀ = 82 pm pm, Dv ₅₀ = 177 pm and Dv _go = 292pm. The pore volume measured by mercury porosimetry of the alumina support is 0.643 ml / g, and a bimodal pore size distribution is observed. The total pore volume consists for 50% of mesopores of size between 7 and 50 nm, and for 50% of macropores of size between 50 nm and 3 pm, centered on 400 nm. This distribution is visible in FIG. 3A, where Vi refers to the porosity of the particles of the initial oxygen carrier (before the aging test). The grain density of the oxygen-carrying solid is 987 kg / m ³ .
The SEM photograph of FIG. 3B on the polished section shows a particle of the spherical oxygen carrier. The small difference in contrast in backscattered electrons between the constituent grains of the oxygen carrier indicates that the copper is homogeneously dispersed within the particle.
Aging of the particles in a batch fluidized bed was carried out according to the same protocol as in Example 1.
The conversion of methane to H ₂ O and CO ₂ , visible on the diagram in FIG. 3C displaying the conversion of methane (normalized) as a function of the redox cycles during the test, is stable, of the order of 99 % on the entire test.
It should be noted that the nature of the active mass used (CuO) causes the appearance of oxygen during the nitrogen sweeping step. The particles can therefore be used interchangeably in a CLC or CLOU type process.
The particle size distribution after the aging test is similar to that of the material before the test.
The main crystalline phases detected by XRD after aging are tenorite (CuO) and alpha alumina. Some low intensity peaks characteristic of copper aluminate (CuAI ₂ O ₄ ) are also present.
Contrary to the observations of Example 2, the aluminum matrix withstood the redox cycles well.
The distribution of copper after 250 cycles in a batch fluidized bed within the particles of the oxygen carrier according to the invention remains relatively homogeneous, with a clearly minimized tendency of the copper to migrate towards the periphery of the particles compared to Example 3. Cuprous nodules with a size between 0.1 μm and 5 μm (bright CuO nodules on the SEM images (a) and (b) of FIG. 3E) are observed in the macroporosity of the particles of the solid carrying oxygen, thus than a few areas where copper is more dispersed and associated with aluminum (CuAI ₂ O ₄ ).
The total pore volume of the particles measured by mercury porosimetry (0.637 ml / g) has changed little, and consists essentially of macroporosity (0.634 ml / g). Almost all of the initial mesoporosity associated with the use of gamma alumina has disappeared to form macroporous alpha alumina in which the copper remains dispersed.
The pore size after 250 cycles varies between 200 nm and 3.5 pm, and is centered on 700 nm. The alumina matrix therefore sintered, but the pore size distribution and the pore volume limit the migration of copper within the particles. This distribution is visible in Figure 3D, where Vi refers to the porosity of the particles of the oxygen carrier after the aging test.
According to this example, the initially macroporous ceramic matrix has withstood very well the 250 successive redox cycles and the copper remains dispersed in the form of small nodules within the macroporosity developed by the matrix. In addition, the textural evolution of the particles is relatively low.
The morphological evolution of the oxygen-carrying solid according to the invention (porosity and distribution of copper) therefore makes it possible to envisage the prolonged use of these particles in an industrial redox process in a chemical loop, in particular in a circulating fluidized bed.
EXAMPLE 5 Solid Carrier of Oxygen CuO / Si-AI with Controlled Porosity
According to this example 5, an oxygen-carrying solid is formed comprising a ceramic matrix of siliceous alumina (13% of SiO ₂ ) within which is dispersed an active mass of oxidoreduction of copper oxide (s) .
The oxygen-carrying solid according to this example is obtained from an aqueous suspension comprising alumina and silicic acid, in particular using the spray drying technique.
The silica alumina used for this example is a powder resulting from a semi-industrial batch production which was obtained by granulation of an aqueous suspension of alumina and silica by means of the spray drying process, as described in the embodiment and preparation of the solid oxygen carrier.
The starting aqueous suspension was composed of 42% by weight of deionized water, 25.5% by weight of gamma alumina grains (γ-ΑΙ ₂ Ο ₃ with particle size Dv50 = 2.8 pm, humidity of 5% by weight) , of 4.8% by weight of boehmite grains (AIOOH with particle size Dv50 = 45 pm, humidity of 30% weight), of 3.7% by weight of grains of amorphous precipitated silica (commercial SiO ₂ type Solvay Tixosil 331, with particle size Dv50 = 3.5 pm, humidity 12% by weight), 16.8% by weight of silicic acid (Si [OH] ₄ concentrated to 50g of SiO ₂ per Kg), 5.6% by weight of polyvinyl alcohol binder (PVA with M ~ 4000g / mol, humidity of 80% by weight), and 1.5% by weight of nitric acid (HNO ₃ concentrated at 68% by weight).
In this formulation, the mass ratio relative to the mass of suspended oxide particles is 15% by weight for the inorganic binders (boehmite and silicic acid) and 3.3% by weight for the organic binder (PVA).
After a vigorous mixing step of the materials in a tank stirred for 30 minutes, the suspension is spray-dried: the homogenized suspension is pumped then sprayed into fine droplets, using a pneumatic nozzle positioned in the upper part a drying chamber. Then, bringing the droplets into contact with a flow of air heated to 300 ° C. induces evaporation of the water and progressive drying, which makes it possible to obtain solid spherical particles collected at the bottom of the drying chamber. , and having a size between 30 μιτι and 200 μιτι.
These dry particles form a powder, which is then calcined for 4 hours in a muffle furnace at a temperature of 700 ° C., then which is screened between 125 μm and 200 μm to remove the finest particles.
The particles obtained constitute the final oxide support, and this final oxide material is composed of 87.1% by weight of alumina (AI ₂ O ₃ ) and 12.9% by weight of silica (SiO ₂ ).
The particle size distribution of the final oxide support indicates Dv10 = 10 pm, Dv50 = 104 pm and Dv90 = 237 pm. The pore volume measured by mercury porosimetry of the alumina support is 0.94 ml / g, and a bimodal pore size distribution is observed. The pore size distribution for the mesoporosity is between 4 and 50 nm (centered on 9.8 nm) and for the macroporosity is between 50 and 1000 nm (centered on 426 nm). The macroporous volume is 0.51 ml / g, i.e.
54% of the total pore volume measured by mercury porosimetry.
120 g of this silica-alumina were impregnated using the dry impregnation method, with 52 g of copper nitrate trihydrate dissolved in the necessary volume of demineralized water. After drying at 120 ° C and calcination at 800 ° C for
12 h, a solid containing 12.4% by mass CuO equivalent is obtained.
After calcination at 800 ° C for 12 h, the X-ray diffraction shows that a copper aluminate (CuAI ₂ O ₄ ) sub-stoichiometric in Cu is formed. An amorphous band between 17 and 28 ° 2Θ corresponding to non-crystallized silica is also present.
The particle size distribution indicates Dv ₁₀ = 13 pm, Dv ₅₀ = 120 pm and Dv _go = 233 pm. The pore volume measured by mercury porosimetry of the oxygen-carrying solid is 0.808 ml / g, and a bimodal pore size distribution is observed. The total pore volume consists for 57% of mesopores of size between 7 and 50 nm, and for 43% of macropores of size between 50 nm and 900 nm, centered on 430 nm. This distribution is visible in FIG. 4A, where Vi refers to the porosity of the particles of the initial oxygen carrier (before the aging test). The grain density of the oxygen-carrying solid is 880 kg / m ³ .
The SEM photograph of FIG. 4B on the polished section shows a particle of the substantially spherical oxygen carrier. The small difference in contrast in backscattered electrons between the constituent grains of the oxygen carrier indicates that the copper is homogeneously dispersed within the particle.
Aging of the particles in a batch fluidized bed was carried out according to the same protocol as in Example 1.
The conversion of methane to H ₂ O and CO ₂ , visible on the diagram in FIG. 4C displaying the conversion of methane (normalized) as a function of the redox cycles during the test, is stable, of the order of 99 % on the entire test.
It should be noted that the nature of the active mass used (CuO) causes the appearance of oxygen during the nitrogen sweeping step. The particles can therefore be used interchangeably in a CLC or CLOU type process.
As in Example 4, the particle size distribution after the aging test is similar to that of the material before testing.
The main crystalline phases detected by XRD after aging are tenorite (CuO) copper aluminate (CuAI ₂ O ₄ ), mullite (AI ₆ Si ₂ O ₁₃ ), alumina delta and alumina alpha.
The distribution of copper after 250 cycles in a batch fluidized bed within the particles of the oxygen-carrying solid according to the invention remains relatively homogeneous, with a clearly minimized tendency of the copper to migrate towards the periphery of the particles compared to Example 3 One observes, for example on the SEM photograph of FIG. 4E of a section of the pile of particles of the oxygen-carrying solid after test, the presence of copper nodules of size between 0.1 μm and 5 μm distributed uniformly in the macroporosity, as well as large areas with copper over-concentration (in light gray, probably CuAI ₂ O ₄ ).
The total pore volume of the particles measured by mercury porosimetry (0.302 ml / g) has greatly decreased, and consists essentially of macroporosity (0.267 ml / g). The presence of silicon in the aluminum matrix leads to a behavior different from that of pure alumina during redox cycles. A greater densification of the ceramic matrix is observed.
The residual mesoporous volume represents only 11% of the total pore volume and is probably linked to the presence of CuAI ₂ O ₄ and / or delta alumina. The macroporous volume has decreased relatively little compared to the initial state.
The pore size after 250 cycles varies between 50 nm and 2.8 pm, and is centered on 780 nm. The alumino-silica matrix sintered, but the size distribution of the pores and the pore volume limit the migration of copper within the particles. This distribution is visible in FIG. 4D, where Vi refers to the porosity of the particles of the oxygen carrier after the aging test.
The morphological evolution of the oxygen-carrying solid according to the invention (porosity and distribution of copper) therefore makes it possible to envisage the prolonged use of these particles in an industrial redox process in a chemical loop, in particular in a circulating fluidized bed.

权利要求:
Claims (23)
[1" id="c-fr-0001]
1. Solid oxygen carrier in the form of particles for a chemical reduction oxidation-reduction process, comprising:
- an oxidation-reduction active mass constituting between 5% and 75% by weight of said oxygen-carrying solid, said oxidation-reduction active mass comprising a metal oxide or a mixture of metal oxides and being capable of exchanging oxygen under the redox conditions of said chemical loop oxidation-reduction process;
- A ceramic matrix within which is dispersed said active redox mass, said ceramic matrix constituting between 25% and 95% by weight of said oxygen-carrying solid, and said ceramic matrix comprising 100% by weight of at least one oxide having a melting temperature above 1500 ° C;
- a porosity such that:
the total pore volume of the oxygen-carrying solid, measured by mercury porosimetry, is between 0.05 and 1.2 ml / g,
- The total pore volume of the oxygen-carrying solid comprises at least 10% of macropores;
the size distribution of the macropores within the oxygen-carrying solid, measured by mercury porosimetry, is between 50 nm and 7 pm.
[2" id="c-fr-0002]
2. Solid oxygen carrier according to claim 1, wherein the total pore volume of the solid oxygen carrier is between 0.1 and 0.85 ml / g.
[3" id="c-fr-0003]
3. Solid oxygen carrier according to one of claims 1 and 2, wherein the total pore volume of the solid oxygen carrier comprises at least 40% of macropores.
[4" id="c-fr-0004]
4. Solid oxygen carrier according to one of the preceding claims, in which the size distribution of the macropores within the solid oxygen carrier is between 50 nm and 3 pm.
[5" id="c-fr-0005]
5. Solid oxygen carrier according to one of the preceding claims, in which said redox active mass comprises at least one metal oxide included in the list constituted by the oxides of Fe, Cu, Ni, Mn and Co, a perovskite having redox properties, preferably a perovskite of formula CaMnO ₃ , a metal aluminate spinel having redox properties, preferably a metal aluminate spinel of formula CuAI ₂ O ₄ or of formula CuFe ₂ O ₄ .
[6" id="c-fr-0006]
6. Solid oxygen carrier according to one of the preceding claims, wherein said redox active mass comprises at least one copper oxide.
[7" id="c-fr-0007]
7. Solid oxygen carrier according to one of the preceding claims, wherein said at least one oxide of the ceramic matrix has a melting temperature higher than 1700 ° C, and preferably higher than 2000 ° C.
[8" id="c-fr-0008]
8. Solid oxygen carrier according to one of the preceding claims, wherein said at least one oxide of the ceramic matrix is chosen from the list consisting of calcium aluminate of formula CaAI ₂ O ₄ , silica of formula SiO ₂ , titanium dioxide of formula TiO ₂ , perovskite of formula CaTiO ₃ , alumina of formula AI ₂ O ₃ , zirconia of formula ZrO ₂ , yttrium dioxide of formula Y ₂ 0 ₃ , zirconate barium of formula BaZrO ₃ , magnesium aluminate of formula MgAI ₂ O ₄ , magnesium silicate of formula MgSi ₂ O ₄ , lanthanum oxide of formula La ₂ O ₃ .
[9" id="c-fr-0009]
9. Solid oxygen carrier according to claim 8, wherein said at least one oxide of the ceramic matrix is silica, alumina, or a mixture of alumina and silica, and preferably is l alumina.
[10" id="c-fr-0010]
10. Solid oxygen carrier according to one of the preceding claims, in which the particles have a particle size such that more than 90% of the particles have a size of between 50 μm and 600 μm.
[11" id="c-fr-0011]
11. Process for the preparation of an oxygen-carrying solid according to one of claims 1 to 10, comprising the following steps:
(A) the preparation of an aqueous suspension comprising an oxide or a mixture of precursor oxides of the ceramic matrix having a melting temperature above 1500 ° C, preferably above 1700 ° C, and even more preferably above 2000 ° C, said precursor oxide (s) forming grains of size between 0.1 pm and 20 pm, preferably between 0.5 pm and 5 pm, and more preferably between 1 pm and 3 pm;
(B) spray drying said suspension obtained in step (A) to form particles, said spray drying comprising spraying the suspension into a drying chamber using spraying means to form droplets , and the simultaneous contacting of said droplets with a hot carrier gas, preferably air or nitrogen, brought to a temperature between 200 ° C and 350 ° C;
(C) calcining the particles resulting from spray drying in step (B), said calcination being carried out in air and at a temperature between 400 ° C and 1400 ° C;
(D) optional screening of the calcined particles from step (C), by separation using a cyclone;
(E) the integration of an oxidation-reducing active mass according to a step e1) or a step e2) to produce the solid carrying oxygen in the form of particles:
e1) (i) impregnation of the particles resulting from step (C) with a precursor compound of an active redox mass, then (ii) drying of the impregnated particles followed (iii) by calcination;
e2) incorporation of the active redox mass during the preparation of the suspension in step (A).
[12" id="c-fr-0012]
12. Process for the preparation of an oxygen-carrying solid according to claim 11, in which step e1) comprises:
(i) impregnating the particles from step (C) with an aqueous or organic solution containing at least one soluble precursor compound of copper, nickel, cobalt, iron or manganese, preferably with an aqueous solution containing at least one precursor compound of the redox active mass chosen from the list consisting of nitrates of the following formulas: Cu (NO ₃ ) ₂ .xH ₂ O, Ni (NO ₃ ) ₂ .xH ₂ O, Co (N0 ₃ ) ₂ .xH ₂ 0, Fe (NO ₃ ) ₃ .xH ₂ O, Mn (NO ₃ ) ₂ .xH ₂ O.
[13" id="c-fr-0013]
13. Method for preparing an oxygen-carrying solid according to claim 12, in which the impregnation (i) in step e1) is carried out in one or more successive steps, and preferably comprises intermediate drying steps at a temperature between 30 ° C and 200 ° C and / or calcination at a temperature between 200 ° C and 600 ° C when the impregnation is carried out in several successive stages.
[14" id="c-fr-0014]
14. Method for preparing an oxygen-carrying solid according to one of claims 11 to 13, in which the drying (ii) in step e1) is carried out in air or in a controlled atmosphere, at a temperature between 30 ° C and 200 ° C, and preferably in air at a temperature between 100 ° C and 150 ° C.
[15" id="c-fr-0015]
15. Method for preparing an oxygen-carrying solid according to one of claims 11 to 14, in which the calcination (iii) in step e1) is carried out in air at a calcination temperature of between 450 ° C. 1400 ° C, preferably between 600 ° C and 1000 ° C, more preferably between 700C and 900 ° C, and is carried out for a period of 1 to 24 hours, and preferably for a period of 5 to 15 hours.
[16" id="c-fr-0016]
16. A method of preparing an oxygen-carrying solid according to claim 11, wherein step e2) comprises (j) impregnating the grains of said precursor oxide (s) with the ceramic matrix with an aqueous or organic solution containing at least one soluble precursor compound of copper, nickel, cobalt, iron or manganese, preferably with an aqueous solution containing at least one compound precursor of the active redox mass chosen from the list constituted by nitrates with the following formulas: Cu (NO ₃ ) ₂ .xH ₂ O, Ni (NO ₃ ) ₂ .xH ₂ O, Co (N0 ₃ ) ₂ .xH ₂ 0, Fe (NO ₃ ) ₃ .xH ₂ O, Mn ( NO ₃ ) ₂ .xH ₂ O, said impregnation being carried out before the suspension of said grains.
[17" id="c-fr-0017]
17. Process for the preparation of an oxygen-carrying solid according to claim 11, in which step e2) comprises (jj) the addition of at least one precursor of the active redox mass, said precursor being a soluble compound of copper, nickel, cobalt, iron and / or manganese in the suspension prepared in step (A), and preferably a compound which is a precursor of the active redox mass chosen from list made up of the nitrates of the following formulas: Cu (NO ₃ ) ₂ .xH ₂ O, Ni (NO ₃ ) ₂ .xH ₂ O, Co (N0 ₃ ) ₂ .xH ₂ 0, Fe (NO ₃ ) ₃ .xH ₂ O, Mn (NO ₃ ) ₂ .xH ₂ O.
[18" id="c-fr-0018]
18. A method of preparing an oxygen-carrying solid according to claim 11, in which step e2) comprises (dd) the addition to the suspension prepared in step (A) of grains of at least one metal oxide included in the list
45 by the oxides of Fe, Cu, Ni, Mn and Co, a perovskite having redox properties, preferably a perovskite of formula CaMnO ₃ , a metal aluminate spinel having redox properties, preferably a metal aluminate spinel of formula CuAI ₂ O ₄ or of formula CuFe ₂ O ₄ , said grains having a size between 0.1 pm and 20 pm, preferably between 0.5 pm and 5 pm, and more preferably between 1 pm and 3 pm, to form the active redox mass of the oxygen-carrying solid.
[19" id="c-fr-0019]
19. Process for the preparation of an oxygen-carrying solid according to one of claims 11 to 18, in which in step A) at least one binder is added to the aqueous suspension intended to strengthen the cohesion of the particles obtained. the outcome of step (B), and / or control the rheology of said aqueous suspension, said binder being an organic binder, preferably chosen from the list consisting of PEG, PVA, PA, PVP, or a inorganic binder, preferably chosen from the list consisting of aluminum hydroxides, boehmite, diaspore, tetraethylorthosilicate, silicic acid, aluminosilicates and kaolin-type clays.
[20" id="c-fr-0020]
20. Method for preparing an oxygen-carrying solid according to one of claims 11 to 19, in which in step A) at least one pore-forming agent is added to the aqueous suspension intended to increase the macroporosity of the particles of the solid oxygen carrier.
[21" id="c-fr-0021]
21. Method for preparing an oxygen-carrying solid according to one of claims 11 to 20, in which, in step E), fines from the oxygen-carrying solid produced during the use of said solid are recycled oxygen carrier in a chemical loop oxidation-reduction process.
[22" id="c-fr-0022]
22. A chemical reduction oxidation-reduction process using an oxygen-carrying solid according to one of claims 1 to 10, or prepared according to the process according to one of claims 11 to 21.
[23" id="c-fr-0023]
23. A method of combustion of a hydrocarbon feedstock by oxidation-reduction in a chemical loop according to claim 22, preferably in which the oxygen-carrying solid is in the form of particles and circulates between at least one reduction zone and one zone d oxidation both operating in a fluidized bed, the temperature in the reduction zone and in the oxidation zone being between 400 ° C and 1400 ° C, and preferably between 600 ° C and 1100 ° C, and more preferably between 800 ° C and
1100 ° C.
1/10
Vi (ml / g) dV / dD (ml / g / nm)
0m (nm)

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同族专利:

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公开号 | 公开日

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BR112019011679A2|2019-10-15|

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CA3045420A1|2018-06-28|

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CN110225795A|2019-09-10|

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AU2017383045A1|2019-07-25|

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US20190388874A1|2019-12-26|

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WO2018115344A1|2018-06-28|

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EP3558515A1|2019-10-30|

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FR3061036B1|2021-07-02|

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FR3022160A1|2014-06-13|2015-12-18|IFP Energies Nouvelles|MESOPOROUS AND MACROPOROUS COMALAXATED NICKEL ACTIVE PHASE CATALYST HAVING MEDIAN MACROPOROUS DIAMETER BETWEEN 50 AND 300 NM AND ITS USE IN HYDROGENATION|

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FR3022161A1|2014-06-13|2015-12-18|IFP Energies Nouvelles|MESOPOROUS AND MACROPOROUS COMALAXATED NICKEL ACTIVE PHASE CATALYST HAVING A MEDIAN MACROPOROUS DIAMETER OF MORE THAN 300 NM AND ITS USE IN HYDROGENATION|WO2022023140A1|2020-07-31|2022-02-03|IFP Energies Nouvelles|Oxygen-carrier solid with sub-stoichiometric spinel for a chemical-looping redox process|JP3315719B2|1992-06-03|2002-08-19|東京電力株式会社|Chemical loop combustion power plant system|

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EP3584426B1|2011-05-11|2021-04-14|Ohio State Innovation Foundation|Oxygen carrying materials|US20210284540A1|2018-07-18|2021-09-16|University Of Florida Research Foundation, Inc.|Facile co2 sequestration and fuel production from a hydrocarbon|

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EP3721992A1|2019-04-09|2020-10-14|Vito NV|Redox preparation process of an oxygen carrier for a chemical looping process|

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CN111704949A|2020-07-06|2020-09-25|山西恒投环保节能科技有限公司|Oxygen carrier composition and preparation method thereof|

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CN113042753B|2021-06-02|2021-08-13|天津大学|Method for reducing SLM forming nickel-based superalloy cracks and improving mechanical property|

法律状态:
2017-12-14| PLFP| Fee payment|Year of fee payment: 2 |

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2018-06-29| PLSC| Publication of the preliminary search report|Effective date: 20180629 |

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2019-12-24| PLFP| Fee payment|Year of fee payment: 4 |

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2020-12-29| PLFP| Fee payment|Year of fee payment: 5 |

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2021-12-27| PLFP| Fee payment|Year of fee payment: 6 |

优先权:

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申请号 | 申请日 | 专利标题

---

FR1663301A|FR3061036B1|2016-12-23|2016-12-23|SOLID MACROPOROUS OXYGEN CARRIER WITH CERAMIC OXIDE MATRIX, ITS PREPARATION PROCESS AND ITS USE FOR A CHEMICAL LOOP OXIDO-REDUCTION PROCESS|

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FR1663301|2016-12-23|FR1663301A| FR3061036B1|2016-12-23|2016-12-23|SOLID MACROPOROUS OXYGEN CARRIER WITH CERAMIC OXIDE MATRIX, ITS PREPARATION PROCESS AND ITS USE FOR A CHEMICAL LOOP OXIDO-REDUCTION PROCESS|

---

CA3045420A| CA3045420A1|2016-12-23|2017-12-21|Macroporous oxygen carrier solid with a refractory matrix, method for the preparation thereof, and use thereof in a chemical-looping oxidation-reduction method|

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PCT/EP2017/084208| WO2018115344A1|2016-12-23|2017-12-21|Macroporous oxygen carrier solid with a refractory matrix, method for the preparation thereof, and use thereof in a chemical-looping oxidation-reduction method|

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BR112019011679A| BR112019011679A2|2016-12-23|2017-12-21|solid macroporous oxide carrier with ceramic oxide matrix, process for preparing it and using it for a chemical circuit oxide-reduction process|

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AU2017383045A| AU2017383045A1|2016-12-23|2017-12-21|Macroporous oxygen carrier solid with a refractory matrix, method for the preparation thereof, and use thereof in a chemical-looping oxidation-reduction method|

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US16/471,499| US20190388874A1|2016-12-23|2017-12-21|Macroporous oxygen carrier solid with an oxide ceramic matrix, method for the preparation thereof, and use thereof for a chemical-looping oxidation-reduction method|

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CN201780079798.5A| CN110225795A|2016-12-23|2017-12-21|Macropore carrier of oxygen solid with refractory matrix, preparation method and its purposes in chemical chain oxide-reduction method|

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EP17822300.4A| EP3558515A1|2016-12-23|2017-12-21|Macroporous oxygen carrier solid with a refractory matrix, method for the preparation thereof, and use thereof in a chemical-looping oxidation-reduction method|