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    • 专利摘要:
    Described is a process for the production of choline hydroxide comprising reacting at a temperature above 30.0 ° C ethylene oxide, trimethylamine, and water in the presence of an aqueous medium in amounts such that a dilute choline hydroxide solution is formed at a concentration of less than 40 wt%, and removing at least a portion of the aqueous medium from the dilute choline hydroxide solution to form a concentrated aqueous choline hydroxide solution, having a choline hydroxide concentration that is at least 1.05 times the choline hydroxide concentration of the dilute choline hydroxide. The process enables large-scale, continuous production of good quality concentrated aqueous choline hydroxide solutions under economically advantageous ethylene oxide consumption factors.
    公开号:BE1021626B1
    申请号:E2014/0240
    申请日:2014-04-10
    公开日:2015-12-21
    发明作者:Kristof Moonen；Dieter Ulrichts；Daan Scheldeman
    申请人:Taminco；
    IPC主号:
    专利说明:

    IMPROVED METHOD FOR CHOLINE HYDROXIDE
    TECHNICAL FIELD
    The invention relates to processes for the preparation of concentrated aqueous choline hydroxide solutions. More specifically, the invention relates to a method that can prevent some of the safety risks associated with ethylene oxide as a reagent, and that produces a less strongly colored product that contains less by-product.
    BACKGROUND ART
    Choline hydroxide, choline base and simply "cbase" are interchangeable terms used in this document. Choline hydroxide or choline base is also known as (2-hydroxyethyl) trimethyl ammonium hydroxide or under the rules of the IUPAC nomenclature as 2-hydroxy-N, N, N-trimethylethanamine. The substance is a strong but organic base, which is an important element for its selection in many end-user applications. Choline hydroxide has applications in the production of other choline salts, for example by neutralization with a suitable acid and in applications where a strong base with very low levels of inorganic ions is needed or where only very low levels can be tolerated. Choline hydroxide is important in a number of applications, such as in the manufacture of electronics.
    Choline hydroxide can be manufactured in a variety of different ways. For example, choline hydroxide can be produced from choline halides (e.g., choline chloride), choline hydroxide can be formed by treating choline sulfate with Ba (OH) 2, or choline hydroxide can be formed from a direct reaction.
    Choline hydroxide can also be obtained by direct reaction of trimethylamine (TMA), water and ethylene oxide (EO). U.S. Pat. No. 2,774,759 describes in Example 2 the reaction of 236 parts of an aqueous solution of 25% TMA with 40 parts of EO. The mixture is stirred until the reaction is nearly complete, while the reaction temperature is kept below 30 ° C. Unreacted TMA is removed under vacuum at about 45-55 ° C, according to US 2,774,759, whereby cbase is dissolved in an aqueous solution of 40-45% abandoned. Starting from an ideal 100% selectivity of the reaction and the removal of TMA, one can calculate a product with 40.65% by weight of cbase in water. Applicants repeated this experiment and found that the reaction is very slow under these conditions and that it was difficult to remove the excess TMA from the reaction product. Applicants obtained a cbase solution with 38.5 wt% choline hydroxide and 2.2 wt% higher ethoxylated by-products.
    This direct method has the advantage of being much more atomic efficient when compared to other methods, such as those using a choline halide starting material. However, the direct reaction of EO and TMA in the absence of a strong acid (e.g., HX) also has a number of disadvantages.
    The ethoxylation of TMA is usually performed in batch mode. Typically, the use of so-called loop reactors (loop reactors), also known as circulating system reactors, wherein the reaction mixture is continuously pumped from the reactor vessel over a heat exchanger, to effectively remove the reaction heat and keep the reaction temperature low. To prevent excessive partial EO pressure, the EO is typically added gradually as the reaction proceeds. To drive TMA consumption to completion, a global molar excess of EO is typically provided. However, excess EO will be consumed in O-ethoxylation and the less desirable O-ethoxylates form as by-products. As the reaction approaches completion, it can take up to 10 moles of EO to further convert 1 mole of TMA.
    A first problem with this reaction path is mainly due to the nature of the trimethylamine (TMA) reactant. First, it is fairly volatile and has an atmospheric boiling point of approximately 3 ° C. TMA has a strong and unpleasant fishy odor, and the odor threshold in air is low, with 2 parts per billion (ppb, 10'9). Vapor-like by-product streams comprising TMA should therefore be burned prior to release, and this must be done at high temperature to prevent nitrosamine formation. This causes specific problems when the process involves vacuum conditions. These properties of TMA further determine that the choline product must ultimately be substantially free of unreacted TMA reagent. Removal of residual TMA from the reaction product by inert gas stripping is impractical because of the low atmospheric boiling point, which means that it is very difficult to condense it from a mixture with an inert gas.
    Another problem with the nature of TMA is that it has limited solubility in water. Excessive presence of TMA will lead to the formation of a separate liquid phase and not to a higher presence of the TMA reagent in the aqueous phase where the reaction takes place. It therefore has a disadvantage in competition with the cbase product for adding an EO molecule.
    A second problem of the ethoxylation of TMA to produce choline is because of the nature of the ethylene oxide reagent (EO reagent). EO is very reactive, highly flammable and toxic, and it is fairly volatile, and has an atmospheric boiling point of approximately 11 ° C. EO supplies its own oxygen for combustion. Autopolymerization with high energy release can easily be caused by a large number of factors, even in an inert atmosphere. The reaction is virtually impossible to control, and is usually accompanied by an explosion. Individual vapor phases with EO as part of the process are therefore preferably avoided. High partial pressures of EO in such vapor phases should certainly be avoided due to the risk of explosion.
    A third problem is because of the nature of the choline hydroxide product. Due to the highly basic nature of choline hydroxide, the molecule is sensitive to the formation of by-product via O-ethoxylation and to color formation and degradation, for example by Hofmann elimination during synthesis.
    Because choline hydroxide has a base strength similar to NaOH, it is able to activate its own hydroxyl groups, resulting in an important competition between N- and O-ethoxylation during the synthesis reaction. In N-ethoxylation, a TMA molecule reacts with an ethylene oxide molecule, resulting in the desired choline molecule. In O-ethoxylation, the hydroxyl group of a choline molecule reacts again with one or more other EO molecules, resulting in choline-like molecules with a higher degree of ethoxylation. The O-ethoxylated by-products still behave as a base, but have a lower strength and a higher molecular weight. In many applications they represent impurities in the end product. Moreover, in many applications, such as the production of choline salts, the molarity (usually expressed in moles / liter) of the hydroxide ion is important and therefore every molecule of EO spent on O-ethoxylation represents an economic loss. The degree of formation of O-ethoxylated products observed during choline hydroxide synthesis can depend on the base strength of the solution and thus also on the hydroxide concentration (mainly the choline hydroxide here). In addition to the concentration, undesired O-ethoxylation can be increased by higher reaction temperatures.
    In addition, choline hydroxide is known to be unstable and develop color during synthesis and storage due to decomposition. Dissolution can occur via a so-called Hofmann elimination, resulting in the formation of TMA and acetaldehyde. Released TMA leads to odor problems as explained above for unreacted TMA left in the choline product. Acetaldehyde ultimately leads to strongly colored condensation products, causing concentrated choline hydroxide solutions to turn brown and black over the course of a few days at room temperature. Hofmann elimination reactions are favored at higher temperatures and the temperature is therefore preferably kept low during the synthesis of choline hydroxide, so as not to obtain a strongly colored product immediately after preparation.
    Color formation is often prevented by the use of very low process temperatures, in the range of 0 ° C to 30 ° C. Although the reaction between TMA and ethylene oxide is highly exothermic, the heat of reaction released at such low temperatures cannot be efficiently and economically recovered. Moreover, keeping the reaction temperature of this exothermic reaction below 40 ° C is a challenge in a large-scale process, since the temperature of ambient cooling water is usually insufficiently low and the use of powerful and expensive cooling equipment would be required. Thus, the use of lower reaction temperatures requires an additional input of energy instead of a recovery of reaction heat. In addition, to ensure acceptable color when stored over a longer period of time, a stabilizer is often added to the choline hydroxide solution after production. DD 241596 A1 deals with avoiding the rebound of the reactor pressure in the EO train carriage container. The document describes how, using circulating system reactors, in a first reaction step, an aqueous solution of 25, 40, or 50% TMA, from a particular vessel selected from a battery of similar vessels, is reacted with gradually added EO in a primary reaction loop at a temperature of 50-60 ° C, at which the TMA concentration decreases and the cbase concentration increases until 80-95% of the required EO is administered. The further conversion of the remaining TMA is carried out by circulating the contents of that vessel over a secondary reaction loop, wherein the temperature is maintained at 10-15 ° C, preferably 12 ° C, with further addition of EO. The excess EO present in a small amount can then be removed by briefly applying a vacuum. The reaction of DD 241596 A1 starts with a solution of at least 25 wt% TMA, which after reaction in the first step leads to a cbase solution of at least 35.7 wt% and after the second step a cbase solution of at least at least 40% by weight after removal of the excessive EO. This two-step batch process leaves something to be desired in terms of by-products and color formation at high cbase concentrations in both steps, and in the field of efficient use of reaction volume and energy.
    Thus, there remains a need for an effective and efficient process with efficient and inexpensive heat control and efficient heat recovery for choline hydroxide production without unwanted by-products and color formation.
    DESCRIPTION OF THE INVENTION
    The present invention includes a process for the production of choline hydroxide and a product obtainable by this process. The present invention relates, for example, to a method that allows large-scale production of high quality concentrated aqueous choline hydroxide solutions under economically acceptable conditions. In particular, the process may include continuous processes for the synthesis of good quality choline hydroxide.
    In one embodiment, the invention provides a process for the production of choline hydroxide comprising: a) reacting at a temperature above 30.0 ° C, in the presence of an aqueous environment, of primary reagents comprising ethylene oxide, trimethylamine and water to a dilute choline hydroxide solution to form a choline hydroxide concentration of less than 40% by weight, and b) removing at least a portion of the aqueous medium from the diluted choline hydroxide solution to form a concentrated aqueous choline hydroxide solution that has a choline hydroxide concentration of at least 1.05 times the choline hydroxide concentration of the diluted choline hydroxide solution.
    Applicants have found that performing the reaction of step a) at the specified low concentrations of choline hydroxide or "cbase" greatly reduces the formation of O-ethoxylated by-products, in favor of the desired N-ethoxylation of TMA, and at the same time also the cbase product's tendency to undergo degradation reactions, and thus the tendency to develop color, greatly diminishes, and this despite performing the reaction at the specified relatively high temperatures. Performing the reaction of step a) at the higher temperatures above 30.0 ° C has the advantage of a higher reaction speed, which ensures a volume efficient use of the available reactor volume, and thus a higher throughput for a reaction device of a predetermined certain size.
    The process of the present invention can provide for the preparation, for example at a temperature above about 50 ° C, of a diluted aqueous choline hydroxide solution containing less than 40% by weight of cbase, which is then concentrated (e.g. to about concentrated 40% aqueous choline hydroxide solutions -50%), whereby all process steps can be carried out with efficient and inexpensive heat control and efficient heat recovery. According to an embodiment of the invention, the O-ethoxylation products can also be kept at a level below 10%, below 5%, or below 1% (with respect to choline hydroxide) to find economically favorable consumption factors for ethylene oxide. In addition, the process of the present invention can maintain the color of freshly synthesized, concentrated, 40% -50% aqueous choline hydroxide solutions below, for example, about 200 APHA, while using a process temperature above, for example, about 50 ° C.
    According to one part of the invention, a method for producing choline hydroxide comprises first reacting, in the presence of an aqueous medium, primary reactants comprising ethylene oxide, trimethylamine and water, to form a dilute choline hydroxide solution. A portion of the aqueous medium is then removed from the diluted choline hydroxide solution to form a concentrated aqueous choline hydroxide solution. In one embodiment, the aqueous medium comprises an excess of water and optionally an excess of trimethylamine.
    Aspects of the present invention may also include the production of a choline hydroxide solution that has a low APHA color value, for example of less than about 200 at room temperature and / or a stabilized choline hydroxide solution, for example, which comprises a stabilizer such as a dithionite salt and / or a dialkylhydroxylamine.
    EMBODIMENTS OF THE INVENTION
    The terms "comprising" and "including" as used herein and in the claims are open or inclusive, and do not exclude the presence of additional unmentioned elements, components in the composition, or process steps. Accordingly, the terms "comprising" and "including" the more restrictive terms include "consisting essentially of" and "consisting of." Unless otherwise stated, all values and ranges given herein are provided up to and including the end points, and the values of the constituents or components of the compositions are expressed in percent by weight or in percent by weight of each component in the composition.In addition, any compound used herein may be alternately discussed with regard to the chemical formula, chemical name, suitable abbreviation, etc.
    As used herein, the choline hydroxide concentration in a composition is intended to include not only the choline hydroxide per se, therefore only the (2-hydroxyethyl) trimethylammonium hydroxide itself, but also all by-products formed by O-ethoxylation of choline hydroxide in higher molecular weight ethoxylates, regardless of the number of EO molecules that are included in the molecule.
    In an embodiment of the present invention, the aqueous medium comprises water. Water has the advantage that it is widely available in a quality that is suitable for many cbase applications. An additional advantage of using water as the aqueous environment is that, when water and TMA are removed from the reaction product by evaporation, the water can easily be condensed at very suitable condensing temperatures, by a suitable choice of pressure, with the vapor phase enriched in TMA. This is a great advantage compared to when TMA is removed from the reaction product by stripping with an inert gas. This advantage can be further exploited so that TMA can also be easily condensed. The TMA vapor can be condensed together with water vapor, whereby a liquid mixture of water and TMA is obtained. The advantage of the process of the present invention is that at least a portion of such a liquid mixture of condensed TMA and water can be recycled to the reaction step a) of the process.
    A further advantage of the present invention, and in particular the use of water as the reaction medium, is that the process of the present invention is capable of producing high purity cbase product, namely a cbase product with a reduced content of non-volatile components, which can sometimes be referred to as "ash" content of an aqueous composition, particularly those that represent a low metal content.
    In more sensitive applications, it may be necessary to use at least partially and preferably entirely higher water quality as a raw material ingredient. In one embodiment, demineralized water can be used and can yield a cbase product with a considerably reduced content of non-volatile components. However, there are applications for which the cbase product made with demineralized water is still considered insufficiently pure. In such cases, a water quality of higher purity can preferably be used as the starting material.
    According to an embodiment of the invention, a method for producing choline hydroxide comprises reacting in the presence of an aqueous medium, from primary reagents comprising ethylene oxide, trimethylamine, and water to form a dilute choline hydroxide solution (e.g., to form an aqueous solution of 10 to less than 10 40% choline hydroxide comprising water as an important part of the equilibrium, for example comprising 90-60% water), removing at least a portion of the aqueous medium from the diluted choline hydroxide solution to form a concentrated aqueous choline hydroxide solution (e.g., an aqueous choline hydroxide solution of 40-50% including water as an important part of the 60-50% balance).
    In an embodiment of the method of the present invention, the aqueous medium comprises a molar excess of water from 100% to 6000% over the theoretically required stoichiometric amount to form the amount of choline hydroxide in the dilute choline hydroxide solution, preferably at least 500 %, more preferably at least 1000%, even more preferably at least 2000%, and even more preferably at least 2500% and optionally at most 5000%, preferably at most 4000%, more preferably at most 3500%, and even more preferably a maximum of 3000% relative to the theoretically required stoichiometric amount to form the amount of choline hydroxide in the dilute choline hydroxide solution.
    In an embodiment of the method of the present invention, the diluted choline hydroxide solution obtained in step a) comprises choline hydroxide in a concentration of 10% to 39.0% by weight based on the total weight of the diluted choline hydroxide solution, preferably at most 38.0 %, more preferably at most 37.0%, even more preferably at most 35.0%, even more preferably at most 32.0%, preferably at most 30.0%, more preferably at most 28, 0%, even more preferably at most 26.0%, even more preferably at most 24.0%, preferably at most 22.0%, more preferably at most 20.0% by weight, and optionally at least 10 , 0%, preferably at least 15.0%, more preferably at least 18% by weight, based on the total weight of the diluted choline hydroxide solution.
    Choline hydroxide, also known as (2-hydroxyethyl) trimethyl ammonium hydroxide, is an organic base suitable for many applications. For example, aqueous solutions of choline base are useful in connection with electronic applications such as positive photoresist developing agents, stripping photoresists, anisotropic etching agents and cleaning agents for silicon wafers. These electronic applications are among the most demanding applications, and may require the very low non-volatile content described elsewhere in this application, in particular a content of the metals belonging to the group consisting of Fe, Cr, Na, Al, Ca, Cu, K, Mg, Mn, Pb and Zn which is at most 1000 ppb by weight, preferably at most 500 ppb by weight and more preferably at most 200 ppb by weight, and optionally combined with a total metal concentration that is at most 5.0 ppm by weight, preferably at most 2.0 ppm by weight, more preferably at most 1.0 ppm by weight.
    In another embodiment, the sodium (Na) content of the cbase obtained by the process of the present invention is at most 1000 ppb by weight, preferably at most 500 ppb by weight.
    In an embodiment of the method according to the present invention, the water added to step a) comprises at least partially but preferably whole water with a total metal concentration that is at most 5.0 ppm by weight, preferably at most 2.0 ppm, more preferably at most 1.0 ppm, preferably the sodium content is at most 1000 ppb by weight, preferably at most 500 ppb by weight, and optionally the total content of the metals belonging to the group consisting of Fe, Cr, Na , Al, Ca, Cu, K, Mg, Mn, Pb and Zn are at most 1000 ppb by weight, preferably at most 500 ppb by weight and more preferably at most 200 ppb by weight.
    In the context of the present invention, metals are defined as a group as the elements shown in the IUPAC version of June 22, 2007 version, and the element groups are numbered from 1 to 18 inclusive in the groups indicated by numbers 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 and 15, except hydrogen (H), and which are arranged in that periodic table to the left of the semi-metals or metalloids, which semi-metals are found on a diagonal line from boron (B) to astate (At). In the context of the present invention, the semi-metals or metalloids, on the diagonal from B to At, are included in the meaning of metals.
    In another embodiment, the sodium content (Post content) of the water added to step a) is at most 800 ppb by weight, preferably at most 300 ppb by weight.
    In another embodiment, the water added to step a) has at least one and preferably all of the following: (i) an Iron concentration (Fe) of at most 200 ppb by weight, (ii) a Sodium concentration (Na) of at most 200 ppb by weight, (iii) a Calcium concentration (Ca) of at most 100 ppb by weight, (iv) a Magnesium concentration (Mg) of at most 50 ppb by weight, (v) a Potassium concentration (K) of at most 50 ppb in weight.
    Because the cbase product and some by-products contain water, there is a need for make-up water in the method of the present invention. The quality of the make-up water influences the quality of the cbase product, in particular with regard to the metal content. The applicants have found that for the manufacture of high-quality cbase product, such as the electronic grade discussed above, top-up water must be supplied of very high quality. Applicants have found that conventional demineralization techniques are unable to provide the very high water quality required for such a high-quality cbase product. Applicants prefer to use so-called "polished" water as make-up water for step a) in the production of the above described cbase product with high quality and low metal content.
    Choline hydroxide can be produced by the direct reaction of ethylene oxide (EO), trimethylamine (TMA), and water, which can be described as follows:
    In a method according to the invention, ethylene oxide, trimethylamine and water, the primary reagents, are reacted in the first step in the presence of an aqueous medium to form a dilute choline hydroxide solution. In other words, the primary reagents, including ethylene oxide, trimethylamine and water, can be introduced into a reaction zone to form a reaction mixture. The primary reagents can be added to the reaction zone sequentially or simultaneously as the starting materials, for example, in a continuous manner.
    The direct synthesis of choline hydroxide can be carried out in a suitable solvent. In other words, the reaction typically occurs in a reaction medium. The reaction medium preferably comprises an aqueous medium. An aqueous medium may include a water-based solvent such as, for example, water or water-miscible alkanols (e.g., methanol) or other solvents (e.g., acetone, acetonitrile, dimethylformamide (DMF), N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), and of such). For example, a water / methanol mixture can be used as an environment to react EO and TMA. Methanol (MeOH) is more easily removed by volatilization than water. Accordingly, a person skilled in the art can choose the ratios of water and methanol such that after evaporation of all methanol (and perhaps some of the water that is co-evaporated), the remaining solution reaches the desired concentrated aqueous choline hydroxide solution (e.g., an aqueous solution of 40 -50%). The synthesis of choline hydroxide can advantageously be carried out in an aqueous medium, such as water, which acts as a reagent and as an effective solvent for the reaction. Preferably, the aqueous reaction medium remains a continuous one-phase reaction medium during the reaction step a). The desired aqueous medium is water, and the water may be of any suitable type, for example distilled, deionized, treated, etc. Preferably, the water is in pure form with little to no impurities.
    In an exemplary embodiment, the reaction medium is excess water or excess water (e.g., primary reagents react in the presence of more water). The amount of water present in the first step may include, for example, a combination of (i) an amount of water that reacts to form choline-OH (e.g., a stoichiometric amount of water), (ii) an amount of water to form the final concentrated solution ( for example a concentration of 45%), and (iii) an amount of water to dilute the choline hydroxide solution in the first step (and which is removed in the second step). The amount of water recognized as (iii) can also be characterized as "dilution excess." In other words, the dilution excess comprises an amount of water required for dilution that is greater than the amount of water required for the concentrated form.
    The dilution excess can be equal to the amount that would subsequently be removed in the second removal step, for example via evaporation. Therefore, the terms "excess" or "molar excess" may include an amount of usually one reagent, such as water or TMA, that is present in excess of the stoichiometric amount necessary for choline formation, or more than the stoichiometric amount of 1: 1: 1: EO: TMA: water, and which may include an amount of reagent required to form a dilute aqueous choline solution, such as a larger amount of water or TMA than is required to form the concentrated aqueous choline solution.
    The excess water is preferably sufficient to produce a dilute choline hydroxide (e.g., an aqueous solution of 10-40% choline hydroxide comprising water as the major part of the balance, such as 90-60% water). The excess water can serve as a diluent during the reaction, and can therefore moderate the temperature rise that can occur locally in parts of the reactor volume, and can also greatly prevent the occurrence of degradation reactions and O-ethoxylation reactions. Preferably the amount of excess water is present in an amount suitable to maintain a single-phase continuous reaction environment.
    In one embodiment, the excess water can be characterized as "a molar excess" of water (e.g., more water than is necessary for the stoichiometry of the reaction to produce choline hydroxide, which comprises an amount of water needed to form a desired, dilute solution). The molar excess of water preferably comprises the dilution excess, which is based on a certain concentration of a diluted choline solution. The excess water may comprise up to about 7000% molar excess of water relative to a stoichiometric amount for a given dilute choline hydroxide solution (e.g., about 1000 to about 6000% may be used, preferably between about 1000% and 3000%). When more excess water is used, the resulting choline base solution is more diluted as indicated in Table 1.
    Table 1
    As one example, a 20% choline hydroxide solution, the diluted solution, can be formed in the first step with a molar excess of water of 2690%. Subsequently, in the second step, the dilution excess of water is removed to provide a 45% choline hydroxide solution.
    In an alternative embodiment, the reaction environment further comprises excessive trimethylamine (TMA) (e.g., the primary reagents react in the presence of excessive TMA). [CONCLUSION 4] In an embodiment of the method of the present invention, the reaction medium comprises a molar excess of TMA (e.g., more TMA than the stoichiometric ratio of 1: 1: 1 molar of EO: TMA: water). Preferably, the amount of excess TMA is present in an amount suitable to maintain a single-phase continuous reaction environment. Without wishing to be bound by a specific theory, it is believed that the competition between O and N ethoxylation during the synthesis of choline hydroxide can also be controlled to some extent through the use of an excess of TMA in the reaction environment. This factor is utilized in the usual so-called "fed batch" processes, in which ethylene oxide is gradually added to a charge of a premix of water and excess TMA present in the reactor. In the fed-batch process, a very high excess of TMA is present during the early stages of the reaction, with O-ethoxylated products being formed mainly towards the end of the EO addition, when the reaction reaches completion, most TMA is consumed, and also the concentration of hydroxide ions is highest. This stoichiometric effect, together with the careful temperature control necessary for ethoxylation reactions, explains why the use of a fed-batch process is so popular.
    Applicants have found that the process of the present invention for step a) can also use the reaction step used as part of the conventional "fed-batch" process. Applicants have found that even in such an embodiment, the reaction can be advantageously carried out at a temperature above 30.0 ° C, provided that the reaction step produces a dilute choline hydroxide solution that has a choline hydroxide concentration of less than 40% by weight. Applicants have found that also in this embodiment the effects of higher selectivity and reaction rate, and the improved color product can be obtained.
    However, in a completely continuous process, TMA and ethylene oxide can be mixed at the total stoichiometric ratio present at the reactor inlet. Therefore, the competition between N- and O-ethoxylation is more constant over time, and higher levels of O-ethoxylation are usually observed compared to the fed-batch operation. An excess of TMA can be used to counteract this effect. The excess TMA can be removed from the final product mixture by evaporation. However, the use of an excess of TMA is limited because two phases can form in the reaction mixture. The occurrence of two phases is detrimental to process operability because good mixing can no longer be guaranteed, and the availability for the reaction of at least one of the reagents can be reduced, which can affect the reaction rate and also the selectivity.
    The amount of excessive TMA causing phase separation is dependent on the choline hydroxide concentration of the mixture. With higher hydroxide concentration of the reaction mixture, the TMA solubility decreases considerably. At a typical commercial product concentration of 45% choline hydroxide, the molar excess of TMA cannot exceed 10% to 20% (this means 1.1 to 1.2 equivalents of TMA relative to EO) to prevent phase separation. By working at a higher degree of dilution, according to the present invention, a higher excess of TMA can be tolerated without the formation of two phases, and thus a better quality product can be obtained, also in a completely continuous process, but also in the fed-batch process. . When the process is carried out according to the present invention, an excess of trimethylamine may comprise up to about 200% excess trimethylamine relative to a stoichiometric amount necessary for the reaction (e.g., an excess of TMA between about 0 or 1 to about 200% may be used, preferably between about 20% and about 100%).
    Thus, in an embodiment of the process of the present invention, the molar excess of trimethylamine in the range of 5% to 200% excess trimethylamine relative to the stoichiometric amount required to form the amount of choline hydroxide in the dilute solution is choline hydroxide, preferably at least 10%, more preferably at least 20%, even more preferably at least 25%, even more preferably at least 30%, preferably at least 35%, more preferably at least 40%, even more preferably at least 45%, even more preferably at least 47% and optionally at most 150%, preferably at most 120%, more preferably at most 100%, even more preferably at most 80%, even more preferably at most 70%, preferably at most 60%, excess trimethylamine relative to the stoichiometric amount required to form the amount of choline hydroxide in the dilute choline hydroxide solution. This feature has the aforementioned advantage of ensuring a single-phase reaction environment, in terms of reaction speed and selectivity, but also in terms of product quality, in particular in fewer O-ethoxylation by-products and with a better color.
    The reaction medium can include any suitable reaction medium or a combination of environments, for example water and trimethylamine, etc. Without wishing to be bound by any particular theory, it is believed that the selection of an aqueous medium such as water as the reaction medium diluted choline hydroxide solutions are much less sensitive to color formation through product degradation and choline hydroxide solutions can be produced with few or no by-products (for example, O-ethoxylation products and degradation reaction (s) are minimized).
    Other reagents, solvents, catalysts, etc. may also be added to the primary reagents at the start of the reaction or during the reaction, for example, which will be apparent to one skilled in the art. In addition, any pretreatments, such as pretreatment of the water with trimethylamine, may also be carried out as needed (e.g., in the case where a stabilizer hydrolyses at a neutral or acidic pH).
    The reagents and the reaction medium can be in any suitable state (e.g., liquid). In an exemplary embodiment, the entire process is conducted in the liquid phase. Thus, the reagents and the reaction medium can be introduced into the liquid phase, and the products and by-products withdrawn in the liquid phase. The ethylene oxide and TMA can, for example, be injected as liquids into a reaction zone with circulating liquid water as the reaction medium. The liquid that circulates as the reaction medium is preferably a continuous, single-phase medium. A suitable reactor pressure can be used to keep all reagents and products in the liquid phase. The pressure can be, for example, between about 1 and 100 bar, preferably between about 2 and 50 bar, more preferably in the range of 3 to 30 bar, even more preferably from 4 to 15 bar, even more preferably from 5 to 10 bar, preferably from 6 to 8 bar, these pressures being expressed in excess pressure, meaning the additional pressure above atmospheric pressure.
    The reaction zone may comprise any suitable agent or device known in the art to provide the appropriate reaction conditions. The reaction zone may comprise a continuous reactor where reagents are continuously fed to the reactor and emerge as a continuous product stream. For example, the reaction zone may comprise a continuous reactor, such as a tubular reactor (tubular reactor), a multi-tubular reactor (multi-tubular reactor), a continuously stirred tank reactor (CSTR), a loop reactor (loop reactor), a plug flow reactor (PFR) ( for example a vessel through which flow is continuous, usually in a stable state, and arranged such that conversion of the chemical substances and other dependent variables are functions of the position within the reactor instead of the time), or any other type of reactor known to those skilled in the art and the reaction zone can be combinations thereof. In one embodiment of the present invention, the reaction zone is, for example, a continuous tube reactor (CTR), a continuously stirred tank reactor (CSTR) or a hybrid between the two, or a combination thereof.
    It was discovered that the aqueous liquid (e.g., excess water and optionally, excess TMA) was found to act as an ideal environment for performing choline hydroxide synthesis. When ethylene oxide was injected together with a sufficient amount of liquid TMA in water while sufficient mixing was envisaged, choline hydroxide was formed with a high reaction rate. Complete conversion of ethylene oxide can be observed with residence times in the reaction zone as short as 10 minutes. Longer residence times can also be used without adverse effects. However, the use of a longer residence time may require the use of larger and more expensive equipment. The residence time in the reaction zone is therefore preferably in the range of 5 to 1000 minutes, more preferably 7 to 300 minutes, even more preferably 9 to 200 minutes, even more preferably 10 to 100 minutes, preferably 12 to 75 minutes , more preferably 15 to 50 minutes, even more preferably 20 to 45 minutes, even more preferably 25 to 40 minutes.
    The exothermic reaction enthalpy, also known as the heat of reaction for the reaction of EO, TMA and water to form choline hydroxide, is 117 kJ / mol EO. Because the reaction is so strongly exothermic, the reaction requires careful temperature management. For example, when water, TMA and EO are mixed in the required ratios to obtain an aqueous choline hydroxide solution of 45%, the temperature would rise to about 200 ° C when the heat is uniformly removed by the reaction mixture. According to an inventive feature, the reaction takes place in a diluted form (for example in an aqueous medium) and therefore the heat of reaction released per mole of choline hydroxide formed is incorporated in a larger mass, which leads to a reduced temperature rise in an adiabatic reaction zone in comparison with the "adiabatic temperature rise" in an undiluted mixture. Water has a high heat capacity (Cp), which makes water the preferred reaction environment to control the temperature rise during the reaction.
    The reaction step is advantageously carried out at a temperature between 40 ° C and 150 ° C, more preferably between 50 ° C and 100 ° C. At these temperatures, a good balance between reaction kinetics, product quality (degradation and O-ethoxylation) and process economy can be achieved. For example, the high reaction temperature in the first step may allow the use of cost-effective cooling methods and efficient heat recovery (e.g., via heat exchangers).
    In an embodiment of the method of the present invention, the primary reagents in step a) are reacted at a temperature of at least 35 ° C, preferably at least 40 ° C, more preferably at least 45 ° C, with more preferably at least 50 ° C, even more preferably at least 55 ° C, and optionally at most 150 ° C, preferably at most 120 ° C, more preferably at most 100 ° C, even more preferably at most 90 ° C, even more preferably at most 80 ° C, preferably at most 75 ° C, more preferably at most 70 ° C, even more preferably at most 65 ° C. As already mentioned above, the higher reaction temperatures bring the advantage of a higher reaction speed, whereby a more effective use of the available reaction volume takes place and / or a higher throughput for a predetermined reaction volume.
    Removal of reaction heat can be achieved by any means known to those skilled in the art. Heat can be removed by circulating a cooling medium through integrated heat exchangers (for example, in a loop reactor or a reactor with an internal cooling coil) or around the reactor wall (e.g., tubular reactor or stirred tank reactor with double jacket). Inexpensive ambient cooling water, such as is available in a typical chemical plant (for example, water extracted from a nearby river or water from a closed cooling circuit cooled by cooling towers in air), is advantageously used as a cooling medium because it can be made more readily available at economically attractive conditions compared to the alternatives. The reaction is most preferably conducted in an adiabatic reactor. In this mode, it is not necessary to remove the heat during the reaction. Increase the temperature of the reaction mixture along the path of the reaction medium through such an adiabatic reactor. Moreover, the temperature rise of such an adiabatic reactor preferably does not lead to a significant deterioration in product quality. A major advantage of carrying out the reaction in an adiabatic reactor is that heat dissipation can be conducted more advantageously in a downstream process step (for example, during the removal of excessive TMA and / or during the concentration of the aqueous solution).
    If necessary, heat can be extracted and / or maintained at any suitable time before, during or after the reaction. For example, the inlet temperature of the reagents, the temperature of the reaction mixture during the reaction, and the product and by-product streams can be maintained at a certain temperature (e.g., above about 50 ° C). Without wishing to be bound by theory, by controlling the heat of the reaction mixture, economically acceptable amounts of choline hydroxide can be achieved and color formation can be minimized. In addition, conducting the TMA ethoxylation reaction in an aqueous environment permits the use of higher temperatures in the process. While prior art methods typically operate at low temperatures of up to 30 ° C to reduce by-product formation and degradation, the present invention allows higher process temperatures while still providing choline hydroxide solutions with acceptable low levels of higher ethoxylates and low color. In one embodiment, the temperature throughout the entire process is maintained at a temperature in the range of from about 40 ° C to about 150 ° C, about 50 ° C to about 150 ° C, preferably from about 50 ° C to about 100 ° C or more preferably from about 50 ° C to 80 ° C.
    The temperature can be maintained by any suitable means known to those skilled in the art. For example, the heat can be controlled by at least one heat exchanger directed in parallel, countercurrent and / or crosscurrent. The heat exchanger can be a part of the reaction zone, be before the reaction zone, and / or after the reaction zone. For example, the temperature in the reaction zone can be controlled by passing a temperature control medium through an external jacket provided on the reaction vessel. By running at a process temperature above 40 ° C or above 50 ° C, for example, the reaction heat can be efficiently removed with readily available ambient cooling water. The collected product streams can also be cooled by passing the streams through a heat exchanger.
    The direct synthesis within the scope of the process of the present invention forms a dilute choline hydroxide solution. In other words, the aqueous choline hydroxide solution can entrain a substantial amount of water from a single-phase reaction medium, which comprises more water than is strictly necessary to obtain a concentrated aqueous choline hydroxide solution (e.g., 45 wt% choline hydroxide). This results in an aqueous choline hydroxide in dilute form (e.g., a concentration of choline hydroxide of about 10% to about 40% by weight and about 90% to about 60% water, relative to the total weight of the dilute choline hydroxide solution). For example, the concentration range of dilute choline hydroxide may be between about 15% to about 30% by weight (e.g., about 85% to about 70% water) with respect to the total weight of the dilute choline hydroxide solution. At lower concentrations, the process can become inefficient because of the large amounts of water that must be removed in the second step and also because of the excessively large and expensive equipment required to have an industrially relevant throughput. The diluted choline hydroxide solution resulting from the first step is preferably transparent and generally has little color. For further improved color control, a color stabilizer, such as sulfite salts, formaldehyde, borohydrides and / or other stabilizer known in the art, for example, can be combined with the reagents to the reactor.
    The diluted choline hydroxide can then be concentrated to a concentration suitable for most applications (e.g., a concentration of about 40% to 50% by weight, relative to the total weight of the concentrated choline hydroxide solution). Thus, in a second step, a portion of the aqueous medium is removed from the diluted choline hydroxide solution to form a concentrated aqueous choline hydroxide solution.
    In an embodiment of the method of the present invention, the concentrated aqueous choline hydroxide solution has a choline hydroxide concentration that is at least 1.10 times the choline hydroxide concentration of the diluted choline hydroxide solution, preferably at least 1.20 times, more preferably at least 1.50 times, with even more preferably at least 1.75 times, even more preferably at least 2.00 times the choline hydroxide concentration of the diluted choline hydroxide solution formed in step a). Applicants have found that the concentration step can be carried out in such a way that any effects on product quality remain easily acceptable and can even be minimized.
    In an embodiment of the method of the present invention, the aqueous medium is at least partially removed from the diluted choline hydroxide solution by at least one of evaporation, stripping, membrane-based separation, and combinations thereof, preferably the evaporation at least partially carried out under vacuum, at preferably the evaporation followed by at least partial condensation of the evaporated water and possibly present evaporated trimethylamine, the method more preferably further comprising the step of recycling at least a portion of the condensed water to step a).
    The diluted choline hydroxide can be concentrated by any suitable technique known in the art. The concentration of the diluted choline hydroxide solution can be obtained, for example, by removing at least a portion of the water. The removal of a portion of the aqueous medium, such as water, can be accomplished by any of the known techniques, such as, for example, evaporation or membrane-based separations (e.g., dialysis, electrodialysis, reverse osmosis, etc.). Water evaporation can be achieved by any means known to the person skilled in the art, for example by distillation, flash evaporation and / or thin film evaporation. Water evaporation can be carried out at atmospheric pressure, for example, but is more advantageously carried out at reduced pressure, so that the temperature can also be lowered in order to obtain a low-colored product. To obtain a favorable energy consumption in the evaporation step, techniques such as multi-stage evaporation (multi-stage evaporation) and vapor recompression (vapor recompression) can be used. When the reaction in the first step of the process is carried out at a sufficiently high temperature, heat can be recovered from the reaction section in the first step a) for use in the evaporation section in the second step b). Shorter contact time and lower temperature in the water removal step may also favor the formation of a low color product. A stabilizer such as a sulfite salt, formaldehyde and / or others known in the art can be added after the first step but before evaporation to obtain a product with improved color.
    When an excess of TMA is used in step a) of the process of the present invention, the excess of trimethylamine is removed from the dilute choline hydroxide solution or from the concentrated choline hydroxide solution. This has the advantage that the problem of residual odor of TMA in the cbase product is limited and preferably even avoided or eliminated.
    The aqueous choline hydroxide in dilute or concentrated form can be stripped of excessive TMA to provide commercial grade choline hydroxide material. Residual TMA in the choline base product is not desirable in most applications because it creates a strong fishy odor with the product. Thus, TMA residues can be removed by one of the techniques known to those skilled in the art, such as inert gas stripping, vacuum boiling, distillation, and so on.
    In addition, most of the residual TMA, the excess in the aqueous medium and / or any residual EO can be separated from the choline hydroxide solution and reintroduced into the reaction zone (e.g., recycled to the reaction zone inlet) to be used further as reaction environment and / or as a reagent. For example, the water can advantageously be recycled to the reaction zone as a reaction medium. In this way the concentration of choline hydroxide in the reaction zone can be kept so low that O-ethoxylation is considerably disadvantaged and the amount of higher ethoxylates in the final solution is considerably lower than what is usually obtained according to the usual method operating at the higher choline hydroxide concentrations.
    The choline hydroxide solution may also include negligible amounts of other by-products (e.g., higher ethoxylates formed by O-ethoxylation). The choline hydroxide preferably comprises, in dilute and concentrated form, low levels of other important by-products (e.g., less than about 10%, less than about 5%, or less than about 3%), such as O-ethoxylates. When the preparation of aqueous choline hydroxide solutions is carried out as described herein, the amount of O-ethoxylated products can easily be kept below about 10% by weight relative to choline hydroxide. A 45% choline hydroxide solution with 10% by weight O-ethoxylation products consumed 7% more ethylene oxide than is theoretically necessary for a pure choline hydroxide solution of equal hydroxide polarity. Thus, the occurrence of O-ethoxylated products is therefore not only a possible product quality problem, but also an economic loss.
    In an embodiment of the method of the present invention, the dilute choline hydroxide solution comprises O-ethoxylation products at a concentration of at most 10% by weight, relative to the total weight of the dilute choline hydroxide solution, preferably at most 8.0%, more preferably at most 6.0%, even more preferably at most 5.0%, even more preferably at most 4.0%, preferably at most 3.0% and more preferably at most 2.0% by weight, relative to the total weight of the diluted choiin hydroxide solution.
    In applications where choline hydroxide is used as the base, for example in the neutralization of various acids in order to obtain the corresponding choline salts, the concentration of hydroxide ions is an important quality parameter. The higher ethoxylates still act as bases, and can participate as active components in these applications, but have the disadvantage of a higher molecular weight. Higher ethoxylates also lead to a higher consumption of EO for the same number of hydroxide equivalents produced, and O-ethoxylation therefore leads to a significant cost increase in choline hydroxide synthesis. Features of the present invention thus result in both a better quality of choline hydroxide product, with a higher concentration of hydroxide ions for the same concentration in weight of the total of bases, and a significant reduction in raw material prices.
    The desired products and / or by-products can be separated, extracted or purified using any means and device known to those skilled in the art. For example, the products can be separated from each other by distillation, stripping with an inert gas, cooking under vacuum, and so on. For example, the choline hydroxide solution can then be treated to remove some or all of the remaining reagents (e.g., trimethylamine) or O-ethoxylated by-products.
    The concentrated choline hydroxide solution can comprise any suitable choline hydroxide concentration. The choline hydroxide concentration in the concentrated solution can be high (for example, in the range of about 25 to about 75% by weight, about 30 to about 60% by weight, about 40 to about 50% by weight of choline hydroxide, or about 45% by weight of choline hydroxide), relative to the total amount of aqueous choline hydroxide solution. In one embodiment, the concentrated choline hydroxide solution comprises choline hydroxide at a concentration of about 40% to 50% by weight, relative to the total weight of the concentrated choline hydroxide solution.
    The diluted and / or concentrated choline solution is preferably produced with a clear appearance or slightly different in color (e.g. an APHA number of less than 500 and preferably less than 200) at room temperature (e.g. about 20-25 ° C) under standard conditions. The color of the choline solution is preferably evaluated by measuring the American Public Health Association color (APHA color), for example by following the procedures of the American Society for Testing and Materials (ASTM). Applicants prefer a method according to ASTM D1209. APHA measurements can be obtained, for example, with a calibrated Lovibond Tintometer PFX195 with a quartz cell with a 5 cm path length. The APHA color value represents a scale ranging from a low-colored, transparent / light-colored sample to a high-colored, opaque / dark-colored sample. For example, a value of less than 20 may indicate a clear or water-white sample, a value of less than 100 may indicate a clear or slightly color-deviating sample, a value of less than 500 may indicate a clear to amber sample, and a value greater than 500 indicates an amber color to an opaque dark color. A lower value thus indicates a more clear / lighter sample, while a higher value indicates an opaque / darker sample. Since the darkness and opacity represent the presence of degradation reactions and associated by-products of the choline base, a lower value is desired.
    In an embodiment of the method of the present invention, the concentrated aqueous choline hydroxide solution has an APHA color of less than 500 at room temperature, preferably at most 400, more preferably at most 300, even more preferably at most 200 at room temperature.
    The choline hydroxide solution made in the method of the present invention can also be stabilized. The diluted cbase solution can already be stabilized, and the majority of the stabilizer in the diluted cbase solution can be recovered and / or retained in the concentrated cbase product. Applicants prefer to add a possible stabilizer downstream of the reaction step a), more preferably in the already concentrated cbase solution, i.e. after the concentration step b). The applicants have found that this is operationally easier to achieve. Applicants have also found that this reduces the risk that the concentration step b) is affected by the stabilizer, and the risk that part of the stabilizer ends up in the water and / or TMA condensed after step b) and that can be excluded and thus is lost, or can be recycled to the reaction step, where it can affect the reaction itself.
    The concentrated cbase solution can therefore be stabilized. In one embodiment, the concentrated aqueous choline hydroxide solution comprises a stabilizer. Stabilization can be achieved, for example, by the use, preferably by addition, of, for example, any suitable stabilizer known in the art, for preventing color formation and maintaining the quality of the product. As used herein, the terms "stabilize" and "stabilized" are intended to include a choline hydroxide solution that undergoes few or no degradation reactions that would otherwise degrade the quality of the choline hydroxide solutions. In other words, there is a reduced or no development of a heavy / dark color, the formation of deposits, volatility, a strong odor, etc. Instead, the stabilized choline solution can prevent a clear or slightly color deviating (e.g. APHA of less than 500 and preferably less than 200) for extended periods of time (e.g., at least a week, at least a month, at least three months, etc.) at room temperature (e.g., about 20-25 ° C) under standard conditions.
    Any suitable stabilizer can be used, including but not limited to, dithionite salts (e.g., an alkali metal dithionite), amines (e.g., dialkyl hydroxylamines), sulfites, hydroquinones, hydrides, carboxylic acids, piperazines, formaldehyde, etc., and mixtures thereof. For example, the stabilizer may include sodium dithionite, N, N-diethylhydroxylamine, ethylenediaminetetraacetic acid (EDTA), methoxyhydroquinone (MEHQ), tetramethylpiperazine-N-oxide (TEMPO), diethylenetriamine (DETA), benzaldehyde, sodium sulfite, boric acid, tetrate trihydrate, tetrate trihydrate, tetrate trihydrate butyl hydroxyanisole, sodium metabisulfite, ascorbic acid, thiourea, formaldehyde, and mixtures thereof. The stabilizer can be added in any suitable form (e.g. powder, aqueous, or in any form suitable for use in the process of choline hydroxide preparation) and at any suitable time (e.g. for formation, after formation of dilute solution or after formation of concentrated solution ). For the desired stabilization techniques and stabilizer compounds, the applicants refer to WO 2013/077855 A1 and WO 2013/076190 A1.
    In an embodiment of the invention, a continuous process for producing choline hydroxide comprises reacting ethylene oxide, trimethylamine, and an excess of water to form a dilute choline hydroxide solution; and removing a portion of the water from the diluted choline hydroxide solution to form a concentrated aqueous choline hydroxide solution. Such a method allows large-scale continuous preparation of concentrated aqueous choline hydroxide solutions of good quality under economically acceptable conditions. In addition, the O-ethoxylation products can also be kept at a level below 10%, below 5%, below 2%, or below 1% (relative to choline hydroxide). In addition, the color of freshly synthesized, concentrated aqueous choline hydroxide solutions (e.g., 40% -50% concentrations) can be maintained below, for example, about 200 APHA when using a process temperature above 50 ° C.
    In one embodiment, the method of the present invention is performed in continuous mode. Features of the present invention may therefore include a continuous process for the production of choline hydroxide. The term "continuous," as used herein, is intended to include processes that synthesize choline hydroxide in one or a single continuous process. In other words, the choline hydroxide does not require multiple steps (e.g., synthesizing an intermediate compound or compounds and, for example, in a separate operation, converting the intermediate (s) to choline hydroxide) that are conducted in the same reactor vessel. The process can be continuous in the sense that at least some of the reagents are introduced and products are withdrawn simultaneously in an uninterrupted manner (for example, the method is not associated with or requires no start-up and stop of individual reaction steps or charges). The continuous process may or may not include the recirculation of products, intermediates, and / or by-products (e.g., a choline solution can be recycled to a reaction zone where EO can be constantly supplied until the desired concentration is reached). The term "single pass" can be used to indicate that there is no reuse of the specific component or product in the process.
    In one embodiment, the reaction of step a) of the process of the present invention is conducted in at least one loop reactor. A loop reactor is a reactor in which the reaction environment is continuously circulated. A loop reactor usually comprises at least one heat exchanger over which the reaction medium is circulated and which extracts heat from the reaction medium. The circulation of the medium in a loop reactor can be driven by any suitable means, for example by gravity, by using density differences between individual zones in the loop reactor. The circulation in a loop reactor can also be driven by a pump, which extracts, for example, medium from a reservoir, which routes the medium through the heat exchanger, whereafter at least a large part of the medium can be sent back to the reservoir. The heat exchanger can also be located upstream of the pump, between the reservoir and the pump. Reagents can be added at different locations in the reactor loop. For example, with a strong exothermic reaction such as the production of choline from TMA, water and EO, EO can be injected directly upstream of the heat exchanger, where the EO can be gaseous, or into the suction of the pump supplying the heat exchanger, whereby the EO is preferably liquid at reaction conditions to prevent pump cavitation problems.
    In one embodiment, the reaction step a) of the process of the present invention is carried out in at least two reactors in series, preferably three reactors in series, which means that the product from the first reactor is fed to a second reactor, and so on. This has the advantage that the upstream reactor can produce an intermediate with still significant amounts of unreacted reagents, such as unreacted TMA, that still have a chance of being converted into the downstream reactor or reactors. This has the advantage that the reaction rate is higher in the upstream reactor or reactors, due to a higher presence of unreacted reagents, and that the selectivity can be favorably influenced in the upstream reactor or reactors due to the lower concentration of the reaction product or products.
    In an embodiment where step a) uses more than one reactor, the ethylene oxide additive (EO) is split and distributed to more than one of the reactors. This has the advantage that not all EO required for the reaction have to move through the entire train of reactors, which has the advantage of a more volume-efficient reaction zone, thus a higher capacity and / or throughput for a predetermined reactor volume. It further has the advantage that the reaction and the associated generation of reaction heat can be controlled and managed by managing the cleavage and distribution of the EO feed on the number of reactors.
    In an embodiment of the process of the present invention, the trimethylamine is produced by the reaction of methanol and ammonia, preferably over a solid acid catalyst, more preferably over an aluminum silicate catalyst, even more preferably a catalyst selected from an amorphous aluminum silicate catalyst and a shape-selective zeolite catalyst.
    The concentrated cbase solution obtained in step b) of the method of the present invention can be used advantageously in a variety of ways. In one embodiment, the method of the present invention further comprises the step of using concentrated choline hydroxide from step b) for a use selected from the group consisting of neutralizing an acidic compound, preferably in a formulation such as a formulation selected from a detergent, an agrochemical formulation and combinations thereof.
    In one embodiment, the method of the present invention further comprises the step of reacting choline hydroxide of step a) or step b) to form an ionic surfactant, preferably a surfactant of the formula RA-SO3 '[(H 3 C) 3 N-CH 2 -CH 2 -OH] +, wherein A represents an oxygen atom or a group of the formula - [0-B] n-0-, wherein B represents an alkyl group with 2 to 4 carbon atoms and n is a whole number in the range of 1-20, and R represents a saturated or unsaturated, unbranched or branched alkyl group of 8 to 30 carbon atoms.
    The invention is now further illustrated by the following examples, without being limited thereto.
    EXAMPLES
    Example 1: Demonstration of the Effect of the Choline Hydroxide Concentration on the Amount of O-Ethoxylates TMA, EO and Water Formed were continuously fed into a 300 ml autoclave using a mass flow controller. Product was withdrawn from the reaction at a flow rate such that the liquid level in the reactor was kept constant. The autoclave was equipped with a magnetically coupled fast leaf stirrer and was heated to the desired temperature by means of an electric heating jacket. The total flow rate was chosen so as to have a residence time in the reactor of 20 minutes. The ratio of the TMA / EO / water stream was chosen in order to obtain a suitable theoretical choline base concentration ("cbase"), based on perfect selectivity of all reagents to the choline hydroxide product. Samples were taken at regular intervals and until a stable reactor output was found. The amount of O-ethoxylated products was measured in the samples expressed as wt% dry matter (DM) for comparison purposes (meaning without taking into account any water and excessive TMA in the samples). The results are shown in Table 2.
    Table 2
    These results demonstrate that a higher concentration of cbase leads to a higher level of O-ethoxylation and the formation of more O-ethoxylated by-products.
    Example 2: Demonstrating the Effect of the Use of Excessive TMA on the Amount of O-Ethoxylates Formed
    A series of experiments were performed as described in Example 1, wherein the molar ratio of TMA / EO was varied. The results are shown in Table 3.
    Table 3
    These results show that a stoichiometric excess of TMA leads to a lower O-ethoxylation and the formation of fewer O-ethoxylated by-products.
    Example 3: Demonstrating How to Benefit the Beneficial Effect of Using Excess TMA at Lower Choline Hydroxide Concentration (about 28.5%)
    A series of experiments were performed as described in Example 1 with Examples E and G performed at a lower choline base concentration of 28.5% and Example F at a higher choline base concentration of 48%. The results are shown in Table 4.
    Table 4
    * Phase separation occurred and no stable product composition could be obtained from the continuous reactor with repetitive sampling.
    These results demonstrate that high presence of TMA as well as high cbase concentration lead to a separation of the reaction mixture into two liquid phases. Phase separation limits the availability of some of the reagents in some phases, which may have an impact on selectivity and reaction rate, usually in a negative sense.
    Example 4: Demonstration of Production of 45% Choline Hydroxide Solution without Stabilizer
    A sample of aqueous choline hydroxide (25 wt%) was prepared in a first step in which a diluted choline hydroxide solution is prepared by reacting ethylene oxide with TMA in an excess of water. In a second step, the diluted choline hydroxide solution was evaporated to form a concentrated choline hydroxide solution. The sample was pumped continuously at a rate of 200 ml / h into a swept film evaporator for laboratory use. A vacuum of 35 mbar was applied and the evaporation was carried out at a temperature of 90 ° C. No stabilizer was added to the sample either during synthesis or prior to evaporation. Thus, an aqueous choline hydroxide solution of 45% by weight was obtained by concentration. The color evolved from pale yellow to yellow, corresponding to the concentration increase. There was no significant evidence of extra color formation in the samples.
    Example 5: Demonstrating Increasing Competition of O-Ethoxylation over N-Ethoxylation at Increasing Choline Hydroxide Concentrations in a Single Phase Fed Batch Reactor.
    Water (4000 g) and TMA (1680 g) were loaded into a 20 liter STR reactor (stirred tank reactor). EO (ethylene oxide, 1416 g) was supplied at such a rate that the EO in the fuel cap did not exceed the concentration of 10% VA / (this usually takes about 4 to 6 hours). During the course of the fed-batch reaction, the temperature was controlled between 35 and 40 ° C. Successive samples were taken over the course of the reaction and analyzed. The results are shown in Table 5.
    Table 5
    These results show that as the TMA concentration decreases and the cbase concentration in the reaction medium increases, the competition between the N-ethoxylation and the O-ethoxylation reaction evolves towards the formation of more O-ethoxylated by-products.
    Example 6: Demonstrations of Phase Separation between Choline Hydroxide / Water and TMA at High Choline Hydroxide Concentration.
    An aqueous solution of 45 wt.% Choline hydroxide was kept at a temperature of 60 ° C by a thermostat and stirred in a pressure-resistant glass reactor. Liquid TMA was added to the liquid phase until clearly two phases were observed. When stirring was stopped, two clear layers were formed within one minute. The choline hydroxide layer was sampled and found to contain 2% TMA. This would correspond to a molar excess of TMA of about 9%. Thus, when an excess of TMA is used that is higher than 9 mol%, two phases can be formed.
    Example 7
    To 97.6 parts by weight of an aqueous solution of 15% by weight of trimethylamine, 7.25 parts of ethylene oxide were added while maintaining the temperature at 60 ° C. The mixture was stirred until the reaction was nearly complete, keeping the fixed temperature at 60 ° C. Unreacted TMA and excess water were removed under a vacuum of 120 mbar absolute pressure and at a temperature in the range of 40-50 ° C until a concentrated choline hydroxide solution (cbase) of about 45 wt% cbase was obtained. The concentrated cbase solution contained only 1.93% by weight of O-ethoxylation by-products.
    Although the invention has been illustrated and described with reference to specific embodiments, the invention is not intended to be limited to the details shown. Instead, various changes can be made to the details within the scope and range of equivalents of the claims and without departing from the invention.
    权利要求:
    Claims (23)
    [1]
    CONCLUSIONS
    A method for the preparation of choline hydroxide comprising: a) reacting at a temperature above 30.0 ° C, in the presence of an aqueous environment, of primary reagents comprising ethylene oxide, trimethylamine and water in such amounts that a dilute choline hydroxide solution becomes formed having a choline hydroxide concentration of less than 40% by weight, and b) removing at least a portion of the aqueous medium from the diluted choline hydroxide solution to form a concentrated aqueous choline hydroxide solution that has a choline hydroxide concentration that is at least 1.05 times the choline hydroxide concentration is from the diluted choline hydroxide solution.
    [2]
    The method of claim 1, wherein the aqueous medium comprises water.
    [3]
    The method of claim 1 or 2, wherein the aqueous medium comprises a molar excess of water from 100% to 6000% over the theoretically required stoichiometric amount to form the amount of choline hydroxide in the dilute choline hydroxide solution.
    [4]
    The method of any one of the preceding claims, wherein a molar excess of trimethylamine is used in reacting the ethylene oxide, trimethylamine, and water.
    [5]
    The method of claim 4, wherein the molar excess of trimethylamine is in the range of 5% to 200% excess of trimethylamine relative to the stoichiometric amount required to form the amount of choiin hydroxide in the dilute choline hydroxide solution.
    [6]
    The method of claim 4 or 5, wherein excess trimethylamine is removed from the dilute choline hydroxide solution or from the concentrated choline hydroxide solution.
    [7]
    The method of any one of the preceding claims, wherein the diluted choline hydroxide solution comprises choline hydroxide in a concentration of 10 to 39.0 percent by weight based on the total weight of the diluted choline hydroxide solution.
    [8]
    The method of any one of the preceding claims, wherein the primary reagents in step a) react at a temperature of at least 35 ° C, and optionally at most 150 ° C.
    [9]
    The method of any one of the preceding claims, wherein the diluted choline hydroxide solution comprises O-ethoxylation products in a concentration of at most 10 percent by weight, based on the total weight of the diluted choline hydroxide solution.
    [10]
    The method of any one of the preceding claims, wherein the concentrated aqueous choline hydroxide solution has a choline hydroxide concentration that is at least 1.10 times the choline hydroxide concentration of the diluted choline hydroxide solution formed in step a).
    [11]
    The method according to any of the preceding claims, wherein the aqueous medium is at least partially removed from the diluted choline solution by at least one of evaporation, stripping, membrane-based separation, and combinations thereof, preferably the evaporation carried out at least partially under vacuum, preferably the evaporation followed by at least partial condensation of the evaporated water and possibly present evaporated trimethylamine, the method more preferably further comprising the step of recycling at least a portion of the condensed water to step a).
    [12]
    The method of any one of the preceding claims, wherein the concentrated aqueous choline hydroxide solution comprises choline hydroxide in a concentration of 30 to 60 weight percent, based on the total weight of the concentrated choline hydroxide solution.
    [13]
    The method of any one of the preceding claims, wherein the concentrated aqueous choline hydroxide solution comprises a stabilizer.
    [14]
    The method of the preceding claim, wherein the stabilizer comprises at least one of dithionite salts, amines, in particular hydroxylamines, sulfites, hydroquinones, hydrides, carboxylic acids, piperazines, and a mixture thereof.
    [15]
    The method of any one of the preceding claims, wherein the concentrated aqueous choline hydroxide solution has an APHA color value of less than 500 at room temperature.
    [16]
    The method of any one of the preceding claims that is performed in a continuous manner.
    [17]
    The method of any one of the preceding claims wherein the reaction is conducted in at least one loop reactor (loop reactor).
    [18]
    The method of any one of the preceding claims wherein the reaction is conducted in two reactors in series, preferably in three reactors in series.
    [19]
    The process of the preceding claim, wherein the ethylene oxide addition is split and distributed to more than one of the reactors.
    [20]
    The method according to any of the preceding claims, wherein the water added to step a) comprises at least partially water with a total metal concentration that is at most 5.0 ppm by weight, and optionally the total content of the metals belonging to the group consisting of Fe, Cr, Na, Al, Ca, Cu, K, Mg, Mn, Pb and Zn is at most 1000 ppb by weight.
    [21]
    The process according to any of the preceding claims, wherein the trimethylamine is produced by the reaction of methanol and ammonia, preferably over a solid acid catalyst, more preferably over an aluminum silicate catalyst, even more preferably a catalyst selected from an amorphous aluminum silicate catalyst and a form-selective zeolite catalyst.
    [22]
    The method of any one of the preceding claims, further comprising the step of using the concentrated choline hydroxide from step b) to neutralize an acidic compound, preferably in a formulation, such as a formulation selected from a detergent formulation, an agrochemical formulation, and combinations thereof.
    [23]
    The method of any one of the preceding claims, further comprising the step of reacting the choline hydroxide of step a) or of step b) to form an ionic surfactant, preferably a surfactant of the formula RA-SO 3 - [(H 3 C) 3 N-CH 2 -CH 2 -OH] +, wherein A represents an oxygen atom or a group of the formula - [O-Bjn-O-, wherein B represents an alkyl group of 2 to 4 carbon atoms and n is a integer in the range of 1-20, and R represents a saturated or unsaturated, unbranched or branched alkyl group of 8 to 30 carbon atoms.
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