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    • 专利摘要:
    The present invention relates to a method of continuously recovering styrene from a mixture by distilling a mixture containing styrene in a cascade consisting of n distillation columns, wherein (i) a feed stream comprising a stabilizer system comprising N-oxyl radicals is fed to the first column and / or the stabilizer system is introduced into at least one upstream distillation column of the nth distillation column; (ii) the boiling point is higher than the boiling point of styrene, and the high boiling fraction comprising the stabilizer system accumulates at the bottom of the nth distillation column; (iii) the lower stream of the high boiling fraction is recycled and introduced into at least one upstream distillation column of the nth distillation column; (iv) The residue of the high boiling fraction is withdrawn from the process.
    公开号:KR20010102394A
    申请号:KR1020017010849
    申请日:2000-02-25
    公开日:2001-11-15
    发明作者:미툴라콘라드；수토리스하인즈프리드리히
    申请人:요헨 카르크, 안드레아스 비베르바흐；바스프 악티엔게젤샤프트；
    IPC主号:
    专利说明:

    METHODE FOR THE CONTINUOUS RECOVERY OF STYRENE FROM A MIXTURE CONTAINING SAME
    [2] Crude styrene, ie a crude mixture comprising styrene and ethylbenzene, is obtained in the process of producing styrene from ethylbenzene by dehydrogenation. Normally, pure styrene is recovered from this mixture by purification. When the temperature increases, many unsaturated compounds are known to carry out free radical polymerization. For this reason, when the crude product obtained industrially is purified by distillation, vinylaromatic compounds such as styrene must be stabilized with suitable compounds to prevent premature polymerization. These stabilizers or polymerization inhibitors are usually added to the crude product to be purified before or during the purification step. Despite these measures, a fraction of oligomers or polymers are obtained. In some cases, especially in the case of operational disturbances, complete polymerization of the monomer batch can occur during purification or distillation. This raises the cost, because thorough cleaning is required and yield is reduced.
    [3] Soviet patents SU-1027150, SU-1558888 and SU-1139722 disclose stabilization of styrene using nitroxyl or bisnitroxyl compounds.
    [4] WO 96/16921 discloses mixtures of hindered nitroxyl compounds and vinylaromatic compounds which are activated by traces of oxygen.
    [5] JP Pyeong 1-165534 discloses piperidyloxy derivatives as polymerization inhibitors for styrene.
    [6] US-A-5254760 and DE-19622498 disclose mixtures of nitroxyl and nitro compounds for stabilizing vinylaromatic compounds during purification or distillation.
    [7] DE 19651307 discloses mixtures of vinyl-containing compounds such as styrene with N-oxyl compounds and iron compounds for inhibiting premature polymerization. These mixtures efficiently stabilize premature polymerization during purification or distillation.
    [8] In order to sufficiently stabilize the undesired polymerization, the stabilizer is used in an amount of about 5 to 1000 ppm based on the mixture containing styrene. Typically, the stabilizer accumulates at the bottom of the column where pure styrene exits to the top. This distillation residue is usually discarded together with the stabilizer dissolved therein.
    [9] US-A-4272344 discloses a distillation method of a vinylaromatic compound wherein 2,6-dinitro-p-cresol is used as polymerization inhibitor. The patent also discloses that part of the distillation residue can be recycled to the distillation system to reduce the required amount of stabilizer continuously consumed during distillation. However, in the actual implementation of the process, the distillation residue contains a high fraction of styrene polymer, which results in a higher viscosity or roughness similar to that of the resin, so that the opportunities for recycling as described above Limited. Thus, recycling is limited in small amounts so that the concentration of styrene polymer in the distillation column does not reach unacceptably high values. Most 2,6-dinitro-p-cresol inhibitors are irreversibly consumed by reaction with styrene radicals that form simultaneously during purification. Recirculation uses only non-consumed part of the stabilizer. No reactivation occurs to form new or already existing species that are effective as free radicals released from spent stabilizers. Since the residual content of the active stabilizer in the recycled distillation residue may not be constant in the method of US-4272344, a sufficient amount of new stabilizer must be added to ensure effective stabilization. Overall, stabilizers are hardly saved by recycling in the method of US-4272344.
    [1] The present invention relates to a process for the continuous recovery of styrene from a mixture containing styrene by distillation in a cascade comprising a plurality of distillation columns.
    [149] 1 illustrates a distillation plant that can be used in the present invention.
    [150] Figure 2 shows a distillation plant suitable for carrying out the process of the invention with oxygen treatment.
    [10] It is an object of the present invention to provide a method for the continuous recovery of styrene from a mixture containing styrene by distillation in the presence of a stabilizer, which utilizes the stabilizer as efficiently as possible.
    [11] We are able to achieve this goal with N-oxyl radicals which have been found to be effective polymerization inhibitors, which are surprisingly able to be activated or reactivated and can be recycled to distillation columns to a greater extent than possible in the case of other stabilizers. Confirmed that it can.
    [12] Accordingly, the present invention provides a method for continuously recovering styrene from a mixture by distillation of the mixture containing styrene in a cascade of n distillation columns, where
    [13] (i) a feed stream comprising a stabilizer system comprising N-oxyl radicals is fed to the first column and / or the stabilizer system is introduced upstream of at least one distillation column of the nth distillation column;
    [14] (ii) the boiling point is higher than the boiling point of styrene, and the high boiling fraction comprising the stabilizer system accumulates at the bottom of the nth distillation column;
    [15] (iii) the lower stream of the high boiling fraction is recycled and introduced into at least one distillation column upstream of the nth distillation column;
    [16] (iv) The residue of the high boiling fraction is withdrawn from the process.
    [17] The mixture containing styrene used in the process of the invention is an industrially obtained product mixture from which the styrene can be separated by distillation. Preferred examples are crude styrene, i.e. the crude mixture obtained in the process of producing styrene from ethylbenzene, which comprises in addition to styrene and ethylbenzene a lower amount of toluene, benzene, cumene and / or α-methylstyrene. Crude styrene is also generally a component having a boiling point higher than the boiling point of styrene in an amount of up to 3% by weight, for example 0.5 to 1.2% by weight of styrene, for example stilbenes, styrene oligomers and styrene polymers, Diphenylethane and 2-phenylnaphthalene.
    [18] Typical compositions of the styrene recoverable by the process of the invention are, for example, as follows: 1% benzene, 2% toluene, 40% ethylbenzene, 56% styrene and 1% high boiling.
    [19] Because of the similar boiling points of styrene and ethylbenzene (145 ° C. and 136 ° C. under atmospheric pressure, respectively) and the high purity of styrene required, separating styrene in pure form requires high separation efficiency in distillation. According to the invention, purification is carried out in a cascade consisting of n distillation columns, in which the bottom product from any distillation column is fed into the next downstream distillation column. The feed point is preferably the middle region of the column. The mixture containing styrene is fed to the first column as a feed stream. The variable n is a positive integer ≧ 2, meaning the number of distillation columns in the cascade. In general, n is 2 to 4, for example 2 or 3. In the nth distillation column, pure styrene is usually separated at the top, whereas the components of crude styrene, which have a lower boiling point than the boiling point of styrene, are separated at the top of the upstream purification column of the nth column. The bottom product of the nth column may be passed through a concentrator, for example a thin film evaporator or a flash evaporator, to separate residual styrene and / or methylstyrene. The low boiling fraction obtained in this way can be further fractionated in the working column. The arrangement and connection of the individual distillation columns for carrying out the process of the invention will be readily understood by those skilled in the art based on the technical judgment of those skilled in the art.
    [20] Typical arrangements for the industrial distillation of styrene are described in Kunststoff-Handbuch, Vol. 4 (Polystyrol) Section 2.3.1.4, 30 ff. (Munich 1996). A distillation plant that can be used in the present invention is disclosed in FIG. 1, for example essentially a benzene (toluene) column (1), ethylbenzene (2a) fed with a mixture of styrene, ethylbenzene, benzene and toluene (1a). Ethylbenzene column (2) responsible for the separation and recovery of) and styrene column (3) where the pure styrene (3a) is finally recovered. The ethylbenzene column (2) and styrene column (3) are each equipped with a boiler (2b) or (3b), that is, a boiler with a heated bottom.
    [21] According to the invention, for example, the substream is withdrawn from the bottom of column 3 and added to the feed stream of column 1 and / or column 2. In a preferred embodiment, the bottom product from column 3 is passed through a plant consisting essentially of equipment 4 and equipment 5. Here, the equipment 4 is, for example, a concentrator arranged as a thin film evaporator or flash evaporator in which the product stream discharged from the bottom of the column 3 does not contain low boiling water. The low boiler can be further separated into styrene and α- (β-) methylstyrene in a working column (not shown). The downstream of the concentrate obtained in the equipment 4 and intermediately stored in the equipment 5 is recycled.
    [22] 2 shows an expanded distillation plant in which a high boiling fraction of concentrate is treated with oxygen as a preferred embodiment of the process of the invention. Suitable temperatures for activation can be determined in the heat exchanger 6.
    [23] According to the invention, the distillation of the mixture containing styrene is carried out in the presence of a stabilizer system comprising N-oxyl radicals. The N-oxyl radicals are stable free radicals, also referred to as persistent radicals hereinafter. They have one or more unpaired electrons. In general, they can be made of pure materials and can be stored without degradation for many years. They themselves cannot trigger the onset of free radical polymerization. They react strongly with and resist organic free radicals, which are simultaneously formed, for example, in the distillation of ethylenically unsaturated compounds. The N-oxyl radicals are generally steric hindrance. That is, they are derived from secondary amines in which all hydrogen atoms in the α position with respect to the nitrogen atom bearing an oxyl group are substituted, for example, with alkyl groups.
    [24] In addition to the N-oxyl radicals, the stabilizer system may further comprise other components, for example a polymerization retardant and a polymerization activator as described below.
    [25] For example, a suitable N-oxyl structure is as follows:
    [26] or
    [27] Where
    [28] R is the same or different alkyl, cycloalkyl, aralkyl or aryl radical having up to 24 carbon atoms, a pair of R are linked in pairing fashion to form a ring system, X, Y and Z are mutually Independently CR ′ 2 , CR′OH, CR ′ (COOH), O, S, CO or a chemical bond, provided that up to one radical X, Y or Z is O or S and up to one radical X, Y Or Z is a chemical bond. R 'is hydrogen or an alkyl, cycloalkyl, aralkyl or aryl radical having up to 24 carbon atoms. For example, R is a C 1 -C 20 -alkyl radical, specifically a C 1 -C 8 -alkyl radical, a C 5 -cycloalkyl radical or a C 6 -cycloalkyl radical, benzyl radical or phenyl radical. XYZ is, for example,-(CH 2 ) 2 -or-(CH 2 ) 3- , -CH 2 -CH (OH) -CH 2- , -CH 2 -CO-O- or -CH 2 -O- to be.
    [29] More suitable N-oxyl radicals are those bearing aromatic substituents, for example aromatic substituents of the structure:
    [30] , or
    [31] Where
    [32] Each aromatic ring may additionally have 1 to 3 inert substituents, such as C 1 -C 4 -alkyl, C 1 -C 4 -alkoxy, esters, amides or cyanos.
    [33] Cyclic amines, for example, may contain additional heteroatoms such as nitrogen, oxygen or sulfur in the ring, which heteroatoms utilize N-oxyl radicals derived from piperidine or pyrrolidine that are not adjacent to the amine nitrogen. It is preferable. The steric hindrance is produced by substituents at two positions adjacent to the amine nitrogen, suitable substituents being hydrocarbon radicals that replace all four hydrogen atoms of the α-CH 2 group. Examples of substituents are phenyl, C 3 -C 6 -cycloalkyl, benzyl, specifically C 1 -C 6 -alkyl radicals, wherein said alkyl radicals attached to the same α-carbon atom are bonded to each other to form 5- or 6 -Can form a ring. N-oxyl of the hindered amines preferably used is a derivative of 2,2,6,6-tetraalkylpiperidine.
    [34] Preferred N-oxyl compounds are compounds of formula II or II ':
    [35]
    [36]
    [37] Where
    [38] R 1 and R 2 are each independently of each other C 1 -C 4 -alkyl or phenyl, R 1 or R 2 together with the carbon atom to which they are attached 1 or 2 heteroatoms selected from O, S or N and 1 Or forms a 5- or 6-membered substituted or unsubstituted saturated hydrocarbon ring which may contain two keto groups,
    [39] R 3 is bonded by hydrogen, hydroxy, amino, SO 3 H, SO 3 M, PO 3 H 2 , PO 3 HM, PO 3 M 2 , organosilicon radicals or carbon, oxygen or nitrogen, preferably 1 Monovalent organic radicals having from 36 to 36 atoms, wherein M is an alkali metal, preferably Li, Na or K,
    [40] R 4 is hydrogen, C 1 -C 12 -alkyl, C 1 -C 12 -alkoxy, or
    [41] R 3 and R 4 together are oxygen,
    [42] R 3 and R 4 are 5- or 6-membered substituted or unsubstituted which may contain 1 or 2 heteroatoms selected from O, S or N and 1 or 2 keto groups together with the carbon atoms to which they are attached To form a saturated hydrocarbon ring,
    [43] Q is bonded by carbon, oxygen or nitrogen and is preferably an m-valent organic radical having 2 to 10,000 atoms, specifically 4 to 2,000 atoms,
    [44] m is 2 to 100, preferably 2 or 3.
    [45] R 1 and R 2 are C 1 -C 4 -alkyl groups, for example methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, secondary-butyl or tert-butyl, or they together are tetramethylene Or pentamethylene group. R 1 and R 2 are preferably methyl.
    [46] Examples of suitable radicals R 4 are hydrogen, the aforementioned C 1 -C 4 -alkyl groups and also pentyl, secondary-pentyl, tert-pentyl, neopentyl, 2,3-dimethylbut-2-yl, hexyl, 2- Methylpentyl, heptyl, 2-methylhexyl, 2-ethylhexyl, octyl, isooctyl, 2-ethylhexyl, nonyl, 2-methylnonyl, isononyl, 2-methyloctyl, decyl, isodecyl, 2-methylnonyl, Undecyl, isododecyl, dodecyl and isododecyl.
    [47] Preferred radicals R 3 are hydrogen, a C 1 -C 20 -alkyl group, for example methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, pentyl, hydroxy, C 2 -C 20 -alkoxy group, For example methoxy, ethoxy, propoxy and t-butoxy, , , , , Wherein R 5 is C 1 -C 12 -alkyl, C 6 -C 12 -aryl or C 7 -C 14 -aralkyl, and Wherein the T groups are the same or different and are C 1 -C 12 -alkyl or phenyl) organosilicon radicals.
    [48] Examples of such organosilicon radicals are -Si (CH 3 ) 3 and -Si (C 2 H 5 ) 3 .
    [49] R 3 and R 4 together with the carbon atoms to which they are bonded e.g. Can be represented.
    [50] Preferred radicals Q can be, for example, the following groups.
    [51]
    [52]
    [53] Where
    [54] R 6 is C 1 -C 12 -alkyl,
    [55] R 7 is hydrogen or C 1 -C 18 -alkyl,
    [56] x is 1 to 12.
    [57] Further suitable N-oxyls include oligomers or polymeric compounds which carry polysiloxane as the main polymer chain and are substituted in the side chain by N-oxyl groups derived from 2,2,6,6-tetraalkylpiperidine. Can be. Wherein said preferred N-oxyl group is a 2,2,6,6-tetramethylpiperidine-N-oxyl group. In addition, examples of such N-oxyl which may be used in the present invention can be found in WO 69/17002. The publication also provides examples of the synthesis of amino compounds based on N-oxyl.
    [58] Further N-oxyl radicals suitable for the present invention include the N-oxyl radicals disclosed in DE 19651307, which is one component of the mixtures disclosed in this publication. The entire contents of this publication are incorporated herein by reference.
    [59] Preferred nitroxyl compounds are as follows:
    [60] 1-oxyl-2,2,6,6-tetramethylpiperidine,
    [61] 1-oxyl-2,2,6,6-tetramethylpiperidin-4-ol,
    [62] 1-oxyl-2,2,6,6-tetramethylpiperidin-4-one,
    [63] 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl acetate,
    [64] 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl 2-ethylhexanoate,
    [65] 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl stearate,
    [66] 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl benzoate,
    [67] 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl (4-tert-butyl) benzoate,
    [68] Bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) succinate,
    [69] Bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) adipate,
    [70] Bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) sebacate,
    [71] Bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) n-butylmalonate,
    [72] Bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) phthalate,
    [73] Bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) isophthalate,
    [74] Bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) terephthalate,
    [75] Bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) hexyhydroterephthalate,
    [76] N, N'-bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) adipinamide,
    [77] N- (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) caprolactam,
    [78] N- (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) dodecylsuccinimide,
    [79] 2,4,6-tris [N-butyl-N- (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl] s-triazine
    [80] N, N'-bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) -N, N'-bis-formyl-1,6-diaminohexane
    [81] 4,4'-ethylenebis (1-oxyl-2,2,6,6-tetramethylpiperazin-3-one) and
    [82] Tris (2,2,6,6, -tetramethyl-1-oxyl-piperidin-4-yl) phosphite.
    [83] The N-oxyl radicals used in the present invention can be prepared by various synthetic steps known per se. Preferred methods for the preparation include oxidation of secondary amines in which NH groups can be converted by oxidation to the corresponding N-oxyl groups. Suitable oxidizing agents are peroxides such as H 2 O 2 , t-butyl hydroperoxide, cumene hydroperoxide, metachloroperbenzoic acid, α-chloroperbenzoic acid, peracetic acid, paranitroperbenzoic acid, perbenzoic acid or magnesium Monoperoxyphthalate. The oxidation can be carried out in an inert solvent such as CH 2 Cl 2 , petroleum ether, toluene, xylene or benzene.
    [84] Parent secondary amines are known in the literature or can be readily prepared by one skilled in the art of organic chemical synthesis by modifying methods known per se. DE 19651307 discloses various preparations of N-oxyl radicals suitable for use in the present invention.
    [85] As a feed stream, the mixture containing styrene is fed to the first distillation column. The mixture containing styrene is already mixed with a stabilizer system comprising N-oxyl radicals. This is common when, for example, in the preparation of styrene-containing mixtures, the gaseous reaction mixture containing styrene is condensed using a crude liquid mixture containing stabilizers. Alternatively or additionally, the stabilizer system may be introduced into one or more upstream distillation columns of the nth distillation column. Advantageously the stabilizer system can be mixed with the feed fed into the distillation column or introduced into the bottom of the column.
    [86] Optional components of the N-oxyl radical and stabilizer system are relatively nonvolatile compounds. For this reason, high boiling fractions containing the stabilizer system accumulate at the bottom of the nth distillation column. In general, the high boiling fraction comprises a mixture containing styrene and / or a relatively high boiling component of styrene oligomers formed in small amounts during distillation. In a special case, the solvent, which has a higher boiling point than the boiling point of styrene and accumulates in the high boiling fraction and serves as a carrier for the stabilizer system, is mixed into the mixture containing styrene before distillation.
    [87] According to the invention, the substream of the stabilizer system solution in the high boiling fraction accumulating at the bottom of the nth distillation column is recycled and added to the feed fed to at least one upstream distillation column of the nth column. The recycled stream may be split and added to a number of points, for example the feed of the first column and the feed of the second column. In a preferred case of distillation in three successive distillation columns, 50 to 100% by weight of the recycled high boiling fraction is added to the feed fed to the first distillation column and 0 to 50% by weight of the recycled high boiling fraction Is preferably added to the feed fed to the second distillation column. The recycled stabilizer solution is advantageously mixed with the feed fed to the upstream distillation column, but the recycled solution may also be added directly to the bottom of the upstream distillation column.
    [88] In general, the high boiling fraction exiting the bottom of the nth column is preferably concentrated, i.e., removing the low boilers, before recycling or draining. Examples of devices suitable for this purpose are thin film evaporators or flash evaporators. The low boiling fraction obtained here can be further fractionated into styrene and α- or β-methylstyrene in an operating column. The content of α-methylstyrene in the recycled stabilizer solution is preferably less than 3% by weight, for example 0.01 to 2% by weight. The higher fraction of α-methylstyrene in the recycled stabilizer solution in some cases raises the α-methylstyrene content in the pure styrene fraction withdrawn at the top of the nth distillation column to an undesirable extent. Concentrating the high boiling fraction as described above prior to recycling can easily reduce the content of α-methylstyrene to a certain value. After concentration, the concentration of N-oxyl radicals in the high boiling fraction is generally between 0.2 and 100 g / l.
    [89] A new amount of stabilizer system comprising N-oxyl radicals is introduced into the first column discontinuously or continuously with the feed, or added to one of the columns to subtract the high boiling fraction from the bottom of the nth distillation column. Replace the amount of stabilizer system removed from the system in the stream. Supplemental amounts of N-oxyl radicals and possibly additional components of the stabilizer system can be used as such or in solvents such as water, C 1 -C 6 -alkanols (eg methanol, ethanol, propanol or n-butanol, solution in a solvent such as i-butanol or t-butanol, water, ketones (e.g. acetone, methyl ethyl ketone, methyl propyl ketone or methyl butyl ketone), diols (e.g. glycol or propylene glycol, or their Alkyl ethers), diamines (e.g., ethylene diamines or propylene diamines or monoalkylamino or dialkylimino derivatives thereof), oligomeric or polymeric ethylene diamines or their alkylimino derivatives. However, the mixture containing styrene to be purified is preferably used as a solvent or suspending medium for the stabilizer system. Thus, mixtures obtained in the course of dehydrogenation of ethylbenzene, ethylbenzene, toluene and further substituted aromatics, which constitute styrene entirely, can be used for this purpose. The stabilizer system solution may be introduced into a feed that is fed to the upstream distillation column of the nth distillation column, for example by mixing with the feed. Thus, fresh N-oxyl radical solution can be metered continuously into the feed fed to the first and / or second distillation column.
    [90] The N-oxyl radical is preferably used in an amount such that the concentration of the N-oxyl radical at the bottom of each distillation column is at least 0.1 ppm, specifically 1 to 500 ppm, preferably 5 to 150 ppm. The amount in the bottom of the distillation column is made by the amount of recycled N-oxyl radicals and the amount of newly added N-oxyl radicals.
    [91] The N-oxyl radicals used according to the invention are effective inhibitors of styrene polymerization and strongly inhibit the formation of styrene polymers during distillation. Therefore, the high boiling fraction of the n-th column is preferably low in viscosity even after concentration, so that a relatively large amount of substream can be recycled without any problems. The temperature in the bottom of the nth distillation column is generally higher than the temperature in the bottom portion of the upstream column, since fractions with boiling points below the boiling point of styrene are distilled off in the upstream column, but styrene is at the top of the nth column. Because it is discharged. Partial reactivation of the N-oxyl radical is thought to occur at the bottom of the nth distillation column. The reactivation can be represented by the following scheme 1:
    [92]
    [93] Where
    [94] R s is an organic group comprising at least one styrene radical. The bond between the R s group and the oxygen atom of the nitroxyl radical may be reversibly broken at elevated temperatures. In the equilibrium reaction at elevated temperature, there is a steady state concentration of free R s radicals that bind in pairs and release the nitroxyl radicals again.
    [95] By measuring the recycling according to the invention of the N-oxyl radicals present in the recycled stream of the high boiling fraction, it is possible to limit the number of cycles Z through which the N-oxyl radicals pass through the (n-1) th distillation column on average. have. The number of cycles Z is linked by Equation 1 for the fraction x of the high boiling fraction recycled based on the total amount of high boiling fraction obtained at the bottom of the nth column.
    [96]
    [97] The N-oxyl radical passes through the (n-1) th column on average at least 1.4 times, preferably at least 2.0 times, in particular at least 2.5 times, particularly preferably three times. The number of cycles described above generally corresponds to a proportion of at least 0.3, preferably at least 0.5, in particular at least 0.6, particularly preferably at least 0.67, of the recycled stabilizer solution. In general, it is preferred to recycle from 10 to 90% by weight, preferably from 30 to 85% by weight, in particular from 50 to 80% by weight of the high boiling fraction obtained at the bottom of the nth distillation column.
    [98] As can be seen from the ESR study, particularly good reactivation of the recycled stabilizer solution can be achieved when the downstream stream is heated above 130 ° C. prior to recycling. In a preferred embodiment of the invention, the substream of the stabilizer system solution is heated to at least 130 ° C., in particular 135 to 160 ° C., before recycling. The heating may advantageously be carried out for 1 to 300 minutes, preferably for 10 to 60 minutes.
    [99] In a further preferred embodiment of the process of the invention, the stabilizer system further comprises at least one polymerization retardant. Polymerization retarders do not completely inhibit the polymerization of free radical initiated styrene monomers, but are materials that reduce the rate of polymerization. The combination of the N-oxyl radicals used in accordance with the invention with at least one polymerization retardant has the advantage that if the concentration of the N-oxyl radicals is reduced below the threshold necessary for effective inhibition, for example, In this case, there is no sudden polymerization of monomers present in the system. Rather, the oligomer or polymer content is gradually increased so that countermeasures can be taken as necessary. The combination of the N-oxyl radical and the polymerization retardant shows a synergistic effect. In other words, the N-oxyl radical and the polymerization retardant have different mechanisms of action that complement each other, and the N-oxyl radical and the polymerization retardant are more effective than the polymerization inhibitory effect obtained when the N-oxyl radical alone or the polymerization retardant is used alone in the same total concentration of stabilizer system. When the oxyl radical and the polymerization retardant are used in combination, a greater polymerization inhibitory effect is obtained. The polymerization retardant is preferably used in an amount of 50 to 2000 ppm based on styrene. The weight ratio of N-oxyl radical to polymerization retardant is preferably in the range of 1:20 to 20: 1.
    [100] Suitable polymerization retardants are, in particular, aromatic nitro compounds, in particular compounds of the formula III:
    [101]
    [102] Where
    [103] R a , R b and R c are each independently of one another hydrogen, C 1 -C 6 -alkyl, halogen or a radical of the formula CN, SCN, NCO, OH, NO 2 , COOH, CHO, SO 2 H or SO 3 H Is,
    [104] The aromatic ring is benzo closed.
    [105] Examples of suitable compounds are as follows:
    [106] 1,3-dinitrobenzene, 1,4-dinitrobenzene, 2,6-dinitro-4-methylphenol, 2-nitro-4-methylphenol, 2,4,6-trinitrophenol, 2,4- Dinitro-1-naphthol, 2,4-dinitro-6-methylphenol, 2,4-dinitrochlorobenzene, 2,4-dinitrophenol, 2,4-dinitro-6-tert-butylphenol , 4-cyano-2-nitrophenol or 3-iodo-4-cyano-5-nitrophenol. Aromatic nitro compounds such as 2,6-dinitro-4-methylphenol, 2-nitro-4-methylphenol, 2,4-dinitro-6-secondary-butylphenol or 2,4-dinitro- Preference is given to using 6-methylphenol.
    [107] The stabilizer system in the process of the invention comprises at least one co-stabilizer selected from the group consisting of aromatic nitroso compounds, phenothiazines, quinones, hydroquinones and their ethers, phenols and ethers, hydroxylamines and phenylenediamines thereof. It may further comprise.
    [108] Further preferred co-stabilizers include substituted phenols or hydroquinones such as the following compounds:
    [109] 4-tert-butylcatechol, methoxyhydroquinone, 2,6-di-tert-butyl-4-methylphenol, n-octadecyl β- (3,5-di-tert-butyl-4-hydride Hydroxyphenyl) propionate, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris ( 3,5-di-tert-butyl-4-hydroxybenzyl) -benzene, 1,3,5-tris (3,5-di-tert-butyl-4-hydroxybenzyl) isocyanate, 1,3 , 5-tris [β- (3,5-di-tert-butyl-4-hydroxyphenyl) -propionyl-oxyethyl isocyanurate, 1,3,5-tris (2,6-dimethyl- 3-hydroxy-4-tert-butylbenzyl) isocyanurate or pentaerythryl tetrakis [β- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate].
    [110] In a preferred embodiment of the process of the invention, the stabilizer system further comprises an activator in addition to the N-oxyl radical used according to the invention. Activators are chemical compounds that can increase the effect of N-oxyl radicals, for example by promoting the binding reaction of free radicals.
    [111] The activator is preferably used in an amount of 0.01 to 20% by weight based on the N-oxyl radical.
    [112] Suitable activators are in particular iron compounds or other transition metal compounds, in particular transition metal compounds which may exist in various oxidation states.
    [113] Preferred iron compounds suitable as active agents are selected from the group consisting of the following (a) to (e):
    [114] (a) iron carbonyl and carbonyl ferrate
    [115] (b) organometallic iron carbonyl compounds
    [116] (c) unsubstituted and substituted ferrocene compounds
    [117] (d) iron compounds having ligands containing oxygen, nitrogen, sulfur or phosphorus or mixtures thereof as donor atoms
    [118] (e) Iron halides and iron pseudohalide compounds.
    [119] Examples of the group (a) compound include iron pentacarbonyl Fe (CO) 5 , ferric nonacarbonyl Fe 2 (CO) 9 , triiron dodecylcarbonyl Fe 3 (CO) 12, and hexagonal octadecacarbonyl Fe 6 ( CO) 18 , all of which are soluble in slightly polar or nonpolar media. Further examples that may be mentioned are carbonyl ferrates, for example M 2 Fe (CO) 4 , M 2 Fe 2 (CO) 8 and M 2 Fe 3 (CO) 11 , wherein M is equal to 1 equivalent Alkali metal or alkaline earth metal). Preference is given to using the corresponding Na compounds.
    [120] The organometallic iron carbonyl compounds of group (b) are, for example, compounds of the formula
    [121] or
    [122] Where
    [123] Variables have the following meanings.
    [124] L 1 -L 4 is hydrogen, C 1 -C 4 -alkyl, for example methyl, ethyl, propyl or t-butyl,
    [125] L5, L6Is-(CH2)n- Or -CO-, wherein L5, L6N is independently 0, 1, 2, or 3).
    [126] Examples of suitable compounds are as follows:
    [127]
    [128] And also
    [129]
    [130] Further compounds of this group which can be used according to the invention are binuclear Fe compounds, for example [H 5 C 5 Fe (CO) 2 ] 2 , [(H 3 C) 5 C 5 Fe (CO) 2 ] 2 And perate M [Fe (CO) 2 C 5 H 5 ] and M [Fe (CO) 2 (H 3 C) 5 C 5 derived therefrom, where M is one equivalent of an alkali or alkaline earth metal, Preferably using the corresponding Na compound).
    [131] Compounds of group (c) for use according to the invention include ferrocene derivatives substituted at one or both of the ferrocene itself and the cyclopentadienyl ring. It is also possible to use dimer ferrocene derivatives. Individual ferrocene units herein are linked by one carbon atom of each cyclopentadienyl ring by chemical bonds or methylene, ethylene, propylene, butylene or phenylphosphine bonds.
    [132] Possible substituents on the cyclopentadienyl ring are C 1 -C 4 -alkenyl radicals, C 7 -C 10 -aroyl, C 1 -C 4 -alkyl radicals, for example methyl, ethyl, n-propyl, i- Propyl, n-butyl, i-butyl, secondary-butyl or tert-butyl. In addition, one or two CH 2 or CH 3 groups of these substituents may be substituted by O, NH, NCH 3 or OH, NH 2 . These heteroatoms or moieties containing heteroatoms are bonded to a carbon atom. It is also possible for one or two CH 2 groups to be substituted by CO, or one or two CH 3 groups to be substituted by CN. It is also possible if necessary for the diphenylphosphino radical to act as a substituent on the cyclopentadienyl ring in addition to the groups mentioned above.
    [133] Examples of ferrocene derivatives which can be used according to the invention are as follows:
    [134]
    [135] Compounds of group d) include, for example, Fe (II) / Fe (III) and O-containing ligands such as sulfate, acetate, oxalate, citrate, tartrate, lactate, gluconate or acetyl It is possible to use complexes or salts with acetonates (acac), ie the following compounds:
    [136] [Fe 3 O (SO 4 ) 6 (OH) 3 ] 5- , [Fe 3 O (O 2 CCH 3 ) 6 (OH 2 ) 3 ] + , [Fe 3 O (O 4 C 2 ) 6 (OH 2 ) 3 ] 5- , [Fe (C 4 H 4 O 6 ) 2 ] 2-/- , Fe (C 4 H 4 O 6 ), Fe 2 (C 4 H 4 O 6 ) 3 , Fe (C 3 H 5 O 3 ) 2 , Fe (C 6 H 11 O 7 ) 2 , [Fe ( 2 O 4 ) 3 ] 3- , FeC 2 O 4 , [Fe (C 2 O 4 ) 2 ] 2- , Fe (acac ) 3 , Fe (acac) 2 , Fe (C 6 H 6 O 7 ), Fe (C 6 H 5 O 7 ).
    [137] Further, further or widely used further O-containing ligands for Fe (II) or Fe (III) are cyclic polyethers, for example Sperland, Cryptand, Crypthasperland, Hemisperland, Coronand. Or modified examples of these ethers and podandes.
    [138] In addition, N-containing chelate ligands such as ethylenediamine (en), 1,10-phenanthroline (phen), 1,8-naphthopyridine (napy), 2,2'-bipyridyl (bipy) And complexes bearing dibenzo [b, i] -1,4,8,11-tetraaza- (14) anulene (taa), ie 25 and 26 (Fe (taa)), as well as literature [see: For example, B. Mennier, Chem. Rev., Vol 92 (8), pp. 1411-1456 (1992), complexes of iron with various substituted porphyrin ligands can be used. Other N-containing ligands are phthalocyanines and derivatives thereof such as [Fe (en) (H 2 O) 4 ] 2 + / 3 + , [Fe (en) 2 (H 2 O) 2 ] 2 + / 3 + , [Fe (en) 3 ] 2 + / 3 + , [Fe (phen) 3 ] 2 + / 3 + , [Fe (napy) 4 ] 2 + / 3 + , [Fe (bipy) 4 ] 2 + / 3+ and to be. Other N-containing ligands are phthalocyanines and derivatives thereof such as And to be.
    [139] The radicals L 7 independently of one another are hydrogen, halogen, SO 3 H, SO 2 NH 2 , SO 2 NH (C 1 -C 12 -alkyl), SO 2 N (C 1 -C 12 -alkyl) 2 , CONH 2 , CONH (C 1 -C 12 -alkyl), CON (C 1 -C 12 -alkyl) 2 , cyano, hydroxy, C 1 -C 12 -alkyl, C 1 -C 12 -alkoxy or C 1 -C 12 -Alkylthio. Preferred halogens are Cl and Br.
    [140] N, O-containing ligands such as ethylenediaminetetraacetic acid (EDTA) or nitrilotriacetic acid (NTA) are [Fe (EDTA) (H 2 O)] -/ 2- , [Fe (NTA) (H 2 O ) 2 ] or [Fe (NTA) (H 2 O) 2 ] - , wherein 8-hydroxyquinoline (quin) or 5-methyl-8-hydroxyquinoline (H 3 C-quin) Additionally available [Fe (quin) 3 ] / [Fe (quin) 3 ] 2- or [Fe (H 3 C-quin) 3 ] / [Fe (H 3 C-quin) 3 ] 2- To provide a compound.
    [141] Further Fe compounds which can be used according to the invention are Fe complexes with the Schiff base of salicylic anhydride.
    [142] The preparation of these N, O-containing ligands is known and is generally carried out by condensation of aromatic or heteroaromatic α-hydroxyaldehydes with aliphatic or aromatic diamines or polyamines. The ligand reacts continuously with the Fe salt in aqueous solution.
    [143] Further Fe compounds which can be used are those having S-containing ligands, for example Or [Fe 4 S 4 (SR) 4 ] 4- / 3- , and Fe (II) / Fe (III) and dithiocarbamate R 2 NCS 2 − , for example [Fe (S 2 CNR 2 ) 3] it is a complex with (R = CH 3, C 2 H 5).
    [144] Moreover, the compound of said group (e) can also be used. It is desirable / 2- (X = Cl, Br ) - Fe halide from, Cl and Fe (II) and Fe (III) salts and complexes of the FeX 4 Br. Fe pseudohalide compounds used according to the invention include, for example, [Fe (CN) 6 ] 3- / [Fe (CN) 6 ] 4- and a series of [Fe (SCN) 3-x (H 2 O). ) 3 + x ] thiocyanate complexes of x + (x = 0, 1, 2).
    [145] Counterions for any complex ions charged by the above-mentioned sound is H +, Na +, K +, and ammonium ion NH 4 + and N (CH 3) and 4 +, in the case of hexacyanoferrate K +, as well as In the case of [Fe (CN) 6 ] 3-, in the case of Fe 2+ and [Fe (CN 6 )] 4- , it is preferable to use Fe 3+ .
    [146] In the case of the charged complex ions in the above-described amount, counter-ion used is Cl -, Br -, I - , SO 4 2-, H 3 CCO 2 -, CrO 4 2-, BF 4 - and B (C 6 H 5 ) 4 - is preferred.
    [147] In a further preferred embodiment of the process of the invention, the substream of the stabilizer system solution is treated with oxygen prior to recycling. Such oxygen treatment can be carried out at 20 to 200 ° C, preferably 50 to 170 ° C and especially 100 to 150 ° C. The oxygen treatment may be advantageously carried out with a gas mixture containing oxygen, in particular essentially a gas mixture containing oxygen and nitrogen, with an oxygen content of 3 to 10% by volume. Gas mixtures containing suitable oxygen are, for example, oxygen-depleted air. The treatment can be carried out at atmospheric or superatmospheric pressure. The treatment with oxygen will result in efficient regeneration of free N-oxyl radicals.
    [148] Suitable apparatus for carrying out the oxygen treatment are all apparatuses for contacting liquids, in particular viscous liquids, with gases, such as gas bubbling apparatuses through liquids, apparatuses for injecting gas streams into liquid streams, and the like. It is also possible to use suitable mixing vessels, for example stirred mixing vessels. Plants suitable for carrying out the process of the present invention with oxygen treatment are shown in FIG. 2.
    [151] Hereinafter, the present invention is illustrated by the following examples.
    [152] Example 1 and Comparative Example 1
    [153] The crude composition of the following composition was distilled at 100 kg / hour using the distillation apparatus shown in FIG. As the condenser 4, a thin film evaporator was used. The N-oxyl radical solution in the crude styrene was metered into the feed stream fed into the first column so that the concentration of N-oxyl radical at the bottom of the first column was always 5 to 100 mg / kg.
    [154] Crude styrene composition:
    [155] Benzene 1 wt%
    [156] Toluene 2% by weight
    [157] Ethylbenzene 40% by weight
    [158] Styrene 56% by weight
    [159] High Boiler 1 wt%
    [160]
    [161] The high boiling fraction obtained from the thin film evaporator was either discarded (Comparative Example 1) or the lower stream of 65% of the high boiling fraction was recycled to the ethylbenzene column 2 (Example 1). Table 1 below shows the viscosity, styrene content and polymer content of the high boiling fraction obtained from the thin film evaporator. The said viscosity is the value measured using Bisko tester VT02 (nominal rotation speed 62.5 minutes -1 ; rotating body 3) marketed by Karlsruhe Hake Mestech, Germany. The polymer content is the value measured according to ASTM D 2121-95.
    [162] As can be seen in the case where the high boiling fraction was recycled according to the invention, the viscosity and polymer content were stable and preferably kept at low levels. In Example 1, where the high boiling fraction was recycled according to the present invention, the N-oxyl stabilizer was saved about 15% compared to the comparative example without recycling.
    [163] Example 1Comparative Example 1 WorkViscosity (mPa s) 60 ° C 80 ° C 100 ° CStyrene content%Polymer content%Viscosity (mPa s) 60 ° C 80 ° C 100 ° CStyrene content%Polymer content% Beginning of observation period4002201809.755402801507.7- + 368003802103.356253101754.7- + 856002701709.467703702203.9- + 1066302801408.748004102502.6- + 1277803301909.7613008004752.7- + 1576503301908.8-12507004502.9- + 1973801901209.4-6003402002.8-
    [164] Example 2 and Comparative Example 2
    [165] The procedure of Example 1 was repeated, but the stabilizer used was in the form of iron dibenzo [b, i] -1,4,8,11-tetraaza (14) arylene as an activator together with the N-oxyl radical of the formula Phosphorus iron compound was used. The N-oxyl radical and the iron compound were used in a weight ratio of 99.9: 0.1.
    [166]
    [167] The viscosity and styrene and polymer content of the high boiling fraction obtained from the thin film evaporator are shown in Table 2 below.
    [168] Example 2Comparative Example 2 WorkViscosity (mPa s) 60 ° C 80 ° C 100 ° CStyrene content%Polymer content%Viscosity (mPa s) 60 ° C 80 ° C 100 ° CStyrene content%Polymer content% Beginning of observation period10506504506.769004803004.1- + 7> 13009005504.579004752753.8- + 219004402503.86- + 287003402104.668003802204.1- + 356803201753.976002301504.3- + 425502751803.3-6002501504.2- + 497003301703.9-6303301703.4- + 567003501903.6-6403301803.8- + 636003201904.8-550280180-- + 70300150905.4-3701801104.2- + 78230130856.1-290170904- + 8417090604.4-18090603.8-
    [169] As can be seen from Table 2, the viscosity and polymer content could be lower than in Example 1.
    [170] Example 3
    [171] The procedure of Comparative Example 1 was repeated, but the stabilizer used was N-oxyl of the following formula.
    [172]
    [173] A high boiling fraction sample obtained on a thin film evaporator was taken and examined by ESR spectroscopy. Measurements were carried out using a laboratory miniscope MS 100 ESR spectrometer, available from MagnetTech GmbH, Berlin, Germany. The measuring instrument was calibrated using a calibration solution that knew the concentration of N-oxyl radicals prior to use.
    [174] The sample was heated at 140 ° C. for 1 hour and the ESR measurements were repeated. The calculated contents of active N-oxyl radicals are shown in Table 3 below.
    [175] SampleBefore heatingAfter heating N-oxyl radical (mg)436660
    [176] As can be clearly seen from the results in Table 3 above, the N-oxyl radicals present in the high boiling fraction could be activated by heating to 130 ° C. or higher.
    权利要求:
    Claims (10)
    [1" claim-type="Currently amended] A method of continuously recovering styrene from the mixture by distilling a mixture containing styrene in a cascade consisting of n distillation columns, wherein
    (i) a feed stream comprising a stabilizer system comprising N-oxyl radicals is fed to the first column and / or the stabilizer system is introduced into at least one upstream distillation column of the nth distillation column;
    (ii) the boiling point is higher than the boiling point of styrene, and the high boiling fraction comprising the stabilizer system accumulates at the bottom of the nth distillation column;
    (iii) the downstream stream of the high boiling fraction is recycled and introduced into at least one upstream distillation column of the nth distillation column;
    (iv) the residue of said high boiling fraction is withdrawn from said process.
    [2" claim-type="Currently amended] The method of claim 1 wherein the high boiling fraction comprises a mixture containing styrene and / or a relatively high boiling point component of the styrene oligomer.
    [3" claim-type="Currently amended] The method of claim 1 or 2, wherein the high boiling fraction is concentrated prior to recycling.
    [4" claim-type="Currently amended] The method of claim 1, wherein the N-oxyl radical passes through the (n-1) th distillation column on average 1.4 or more times.
    [5" claim-type="Currently amended] The method of claim 1, wherein the substream is heated to a temperature of at least 130 ° C. prior to recycling.
    [6" claim-type="Currently amended] The method of claim 1, wherein the stabilizer system further comprises a polymerization retardant.
    [7" claim-type="Currently amended] The method of claim 6, wherein the polymerization retardant is an aromatic nitro compound.
    [8" claim-type="Currently amended] The method of claim 1, wherein the stabilizer system further comprises an activator.
    [9" claim-type="Currently amended] The method of claim 8, wherein the activator is an iron compound.
    [10" claim-type="Currently amended] 10. The method of any one of claims 1 to 9, wherein the substream is treated with oxygen prior to recycle.
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    同族专利:
    公开号 | 公开日
    TW483889B|2002-04-21|
    DE19908463A1|2000-08-31|
    CN1341087A|2002-03-20|
    CA2364265A1|2000-08-31|
    CN1186301C|2005-01-26|
    AU3806900A|2000-09-14|
    KR100632224B1|2006-10-11|
    BR0008544A|2001-11-06|
    EP1154974B1|2003-09-10|
    WO2000050367A1|2000-08-31|
    AT249407T|2003-09-15|
    AR022752A1|2002-09-04|
    SA731B1|2006-04-26|
    EP1154974A1|2001-11-21|
    JP2002537366A|2002-11-05|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    1999-02-26|Priority to DE1999108463
    1999-02-26|Priority to DE19908463.7
    2000-02-25|Application filed by 요헨 카르크, 안드레아스 비베르바흐, 바스프 악티엔게젤샤프트
    2000-02-25|Priority to PCT/EP2000/001584
    2001-11-15|Publication of KR20010102394A
    2004-06-09|First worldwide family litigation filed
    2006-10-11|Publication of KR100632224B1
    2006-10-11|Application granted
    优先权:
    申请号 | 申请日 | 专利标题
    DE1999108463|DE19908463A1|1999-02-26|1999-02-26|Process for the continuous production of styrene from a styrene-containing mixture|
    DE19908463.7|1999-02-26|
    PCT/EP2000/001584|WO2000050367A1|1999-02-26|2000-02-25|Method for the continuous recovery of styrene from a mixture containing same|
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