MXPA01006058A - Catalyst stabilising additive in the hydrolysis of alkylene oxides - Google Patents

Abstract

A process for the preparation of an alkylene glycol by reacting an alkylene oxide with water in the presence of a solid catalytic composition which includes a strongly basic ion exchange resin coordinated with one or more anions, and a stabilising additive which is an acidic ion exchange resin. Preferably the acidic ion exchange resin is of the weakly acidic methacrylate type.

Description

ADDITIVE FOR THE STABILIZATION OF CATALYST IN THE HYDROLYSIS OF ALKYLENE OXIDES The present invention relates to a process for the preparation of an alkylene glycol by the reaction of an alkylene oxide with water. in the presence of a catalytic composition. Background of the Invention Alkylene glycols, in particular monoalkylene glycols, are of established commercial interest. For example, monoalicylene glycols are being used in antifreeze compositions, such as solvents or as base materials in the production of polyalkylene terephthalates, for example, for fibers or bottles. The production of alkylene glycols by liquid phase hydrolysis of alkylene oxide is already known. The hydrolysis is carried out without a catalyst, by adding a large excess of water, for example 20 to 25 moles of water per mole of alkylene oxide, or it can be carried out with a smaller excess of water in a catalytic system. The reaction is considered a substitution reaction Ref: 130531 nucleophilic, whereby the opening of the alkylene oxide ring occurs, the water acting as a nucleophilic agent. Since the initially formed monoalkylene glycol also acts as a nucleophilic agent, a mixture of monoalkylene glycol, dialkylene glycol and higher alkylene glycols is formed as a rule. In order to increase the selectivity to the monoalkylene glycol, it is necessary to suppress the secondary reaction between the primary product and the alkylene oxide, which competes with the hydrolysis of alkylene oxide. An effective means to suppress the side reaction is to increase the relative amount of water present in the reaction mixture. Although this measure improves the selectivity towards monoalkylene glycol production, it creates a problem in which large quantities of water have to be removed to recover the product. Considerable efforts have been made to find an alternative to increase the selectivity of the reaction without having to use a large excess of water. Generally these efforts have focused on the selection of more active hydrolysis catalysts and several catalysts have been developed. Both catalysts have been investigated, acid and alkaline, so it would seem that the use of acid catalysts improves the reaction rate without significantly affecting the selectivity, so when using alkaline catalysts, lower selectivities are usually obtained with respect to the monoalkylene glycol. Some anions, for example bicarbonate (hydrogen carbonate), bisulfite (hydrogen sulfide), formate and molybdate are known to show good catalytic activity in terms of the conversion of alkylene oxide and selectivity towards the monoalkylene glycol. However, when the salts of these anions are used as a catalyst in a homogeneous system, the formation of the reaction product by distillation will impose a problem because the salts are poorly soluble in the glycol and tend to make it semi-solid. The quaternary ammonium salts remain soluble in the glycol reaction product.

High conversions, good selectivity and a low water / alkylene oxide ratio can be obtained with the process disclosed in EP-A 0 156 449 and EP-A 0 160 330 (both by Union Carbide). According to these documents the hydrolysis of alkylene oxides is carried out in the presence of a material containing anion metalate which improves the selectivity, preferably a solid having sites of electropositive complexes having affinity for the metallate anions. Preferably, said solid is an anion exchange resin, in particular a copolymer of styrene-divinyl benzene. The electropositive complex sites are in the particular quaternary ammonium, the protonated tertiary amine or the quaternary phosphonium. Metallic anions are specified as anions molybdate, tungstate, metavanadate, hydrogen pyrovanadate and pyrovanadate. A complication of this process is that the product stream containing alkylene glycol also comprises an essential amount of metallate anions, displaced from the sites of electropositive complexes of the material containing the solid metallate anion. In order to reduce the amount of metallate anions in the alkylene glycol product stream, this stream is contacted with a solid having complex electropositive sites associated with anions that are replaceable by said metallate anions. In WO 95/20559 (Shell) a process for the preparation of alkylene glycols is disclosed wherein an alkylene oxide is reacted with water in the presence of a catalyst composition comprising a solid material having one or more electropositive sites, which are coordinated with one or more anions other than the metallate or halogen anions, for example, bicarbonate, bisulfite and carboxylate, with the proviso that when the solid material is an anion exchange resin of the quaternary ammonium type and the anion is bicarbonate the process is carried out in essential absence of carbon dioxide. According to this document, the presence of carbon dioxide in the feed is detrimental to the catalytic effect of bicarbonate exchange resins of the quaternary ammonium type.

A disadvantage shared by conventional anion exchange resins is their limited heat tolerance. In practicing the process of alkylene oxide hydrolysis according to WO 95/20559 with conventional organic quaternary ammonium ion permutation catalyst compositions it has been found that, under severe reaction conditions of alkylene oxide hydrolysis (high temperature and / or long service) the catalytic activity (selectivity and / or conversion) of conventional resin-based catalysts tend to deteriorate. Moreover, under these reaction conditions it was found that these catalysts were subject to swelling. The heat sensitivity of anion exchange resins has been found for a long time According to Elizabeth W. Baumann, in J. of Chem i ca nd En gin eerin g Da ta 5 (1960) 376-382, the degradation of the AMBERLITE IRA-400, which is a strong base ion exchange resin (quaternary ammonium) that has three methyl groups in its quaternary structure can release (according to two decomposition reactions the and lb) trimethylamine that can be absorbed by a cation exchange resin, such as AMBERLITE IR-120-H, if present, or methanol that is not absorbed by the cation exchange resin. In the first column of the article it is further remarked that "the presence of this resin (AMBERLITE IR-120-H) provides a means to absorb the basic decomposition products that could affect the progress of decomposition, allows the study of decomposition by the reaction la and, in general, doubles the conditions in a mixed layer deionization system ". The article does not contain any demonstration of any effect of AMBERLITE IR-120-H, which is a strongly acid ion exchange resin of the sulfonic type, in terms of the thermal stability of the anion exchange resin. And of course the article is not involved with the stability of any catalytic effect associated with an ion exchange resin. In US-A 4,759,983 (Union Carbide) there is disclosed a process for the preparation of alkylene glycols from alkylene oxide and water in the presence of a water-insoluble phase containing an organometalate which improves the selectivity, which may comprise a resin of exchanges of anion, and a stabilizing material that is soluble in water and comprises a cation and a metallation anion improving the selectivity. This stabilizing material is a metalate salt. In the corresponding European Patent Application No. 98204234.3, reported on the same date hereof, a process for the preparation of alkylene glycols is disclosed by the reaction of an alkylene oxide with water in the presence of a catalyst composition including a derivative of carboxylic acid, having in its chain molecule one or more carboxyl groups and one or more carboxylate groups, the individual carboxyl and / or carboxylate groups are separated from each other in the chain molecule by a separation group consisting of at least one an atom. Catalyst compositions including said carboxylic acid derivatives immobilized on a solid support, in particular an anion exchange resin, are those specifically claimed. An advantage of the carboxylic acid derivatives as defined in this application is that their catalytic combination with the anion exchange resins is more stable. It has been found that the stability of the solid catalysts in the conversion of alkylene oxide to alkylene glycol, whose solid catalysts include a strong basic ion exchange resin coordinated with one or more anions, can be considerably improved by adding a relatively small amount of a acid ion exchange resin. Brief description of the invention The present invention relates to a process for the preparation of an alkylene glycol by the reaction of alkylene oxide with water in the presence of a solid catalyst composition., which includes a strong basic ion exchange resin coordinated with one or more anions and a stabilizing additive which is an acid ion exchange resin. The present invention further relates to a solid catalyst composition for use in the preparation of an alkylene glycol by the reaction of an alkylene oxide with water, which includes a strong basic ion exchange resin coordinated with one or more anions, and an additive. stabilizer which is an acid ion exchange resin. Detailed Description of the Invention The solid catalyst compositions defined herein are effective as catalysts for hydrolysis of the alkylene oxide in a heterogeneous liquid reaction system. In comparison with the catalyst compositions having the same components without the acid ion exchange resin, the compositions according to the present invention are more stable and retain their selectivity and stability under severe reaction conditions as well as being more resistant to swelling . Any of a large number of strong basic anion exchange (IER) resins can be used as a solid support for the catalytic anion, particularly those in which the basic groups are quaternary ammonium or quaternary phosphonium groups. The IERs based on vinylpyridine or polysiloxanes can also be used.

Strong basic anion exchange resins which are of suitable use are known per se and many are commercially available, for example those sold under the trade names AMBERJET 4200, AMBERLITE 400, IRA 404, LEWATIT M 500 WS, DOWEX 1 x 8, DOWEX MSA-1 (all of which are products based on polystyrene crosslinked with divinylbenzene) and Reillex HPQ (based on polyvinylpyridine, crosslinked with divinylbenzene). The catalytic anion which is coordinated with the anion exchange resin can be advantageously chosen from the group of metalates such as molybdate, tungstate and vanadate, carboxylates such as formate and citrate, bicarbonate and bisulfite. Particularly advantageous are the polycarboxylates, which have in their chain molecule one or more carboxyl groups and one or more carboxylate groups, the individual carboxyl and / or carboxylate groups being separated from each other in the chain molecule by a separation group consisting of of at least one atom. Of the polycarboxylates, citrate is the most preferred.

There are three types of acid ion exchange resins, that is, the strong acid ion exchange resins of the sulfonic type, the acid ion exchange resins of the acrylate type and the strong acid ion exchange resins of the methacrylate type. For the purposes of the present invention, the overall acid function should be kept relatively low because otherwise the selectivity of the catalyst composition could be adversely affected. Therefore, a weak acid ion exchange resin, ie one of the methacrylate type, is the most suitable. However, it is to be understood that a small amount of one or both of the two types, either alone or in combination with the methacrylate type, is also within the scope of the present invention. Examples of weak acid ion exchange resins of the methacrylate type are those known from the trademarks AMBERLITE IRC-50, AMBERLITE GC-50, AMBERLITE IRP-64 and AMBERLITE IRP-88. Examples of commercially available acrylic ion exchange resins of the acrylate type are those known from the trademarks AMBERLITE IRC-86, AMBERLITE IRC-76, IMAC HP 336 and LEWATIT CNP 80, Examples of strong acid ion exchange resins of the sulfonic type commercially available are those known by the trademarks AMBERLYST 15, AMBERJET 1500H, AMBERJET 1200H, DOWEX MSC-1, DOWEX 50W, DIANON SKIB, LEWATIT VP OC 1812, LEWATIT S 100 MB and LEWATIT S 100 Gl. In terms of exchange capacity or equivalent of the active sites, the relative amount of acid ion exchange resin that will be used according to the present invention is generally from 10 to 200%, based on the total capacity of the exchange resin of strongly acid ion. Preferably, this amount reaches from 15 to 100%, more preferably from 20 to 50%. In terms of weight, the relative amount of acid ion exchange resin that will be used in accordance with the present invention generally ranges from 5 to 70% by weight of basic (anionic) exchange resin. Preferably, the amount is from 5 to 50% by weight, more preferably from 10 to 30% by weight. Preferably, the two components, i.e. the strong basic ion exchange resin which is coordinated with one or more catalytically effective anions and the stabilizing additive which is an acid ion exchange resin, are used in an intimate mixture. The coordination of the strong basic ion exchange resin with the catalytically effective anion can be carried out, in principle, before or after mixing with the stabilizing additive. Preferably, coordination is performed before mixing. The alkylene oxides used as starting material in the process of the invention have their conventional definition, that is, they are compounds that have a nearby oxide (epoxy) group in their molecules. Particularly suitable are the alkylene oxides of the general formula R1 CR2 CR3 R4 where R1 to R4 independently represent a hydrogen atom or an optionally substituted alkyl group having from 1 to 6 carbon atoms. Any alkyl group, represented by R1, R2, R3 and / or R4 preferably has from 1 to 3 carbon atoms. The inactive moieties, such as hydroxy groups, may be present as substituents. Preferably, R1, R2 and R3 represent hydrogen atoms and R4 represents an unsubstituted C? -C3 alkyl group and, more preferably, R1, R2, R3 and R4 all represent hydrogen atoms. Thus, examples of suitable alkylene oxides include ethylene oxide, propylene oxide, 1,2-epoxybutane, 2,3-epoxybutane and glycidol. Ethylene oxide and propylene oxide are of particular commercial importance. As previously mentioned, it is advantageous to carry out the hydrolysis of the alkylene oxides without using excessive amounts of water.

In the process according to the present invention, the amounts of water in the range of 1 to 15 moles per mole of alkylene oxide are quite adequate, the amounts in the range of 1 to 6 on the same basis being preferred. In the process of the invention, high selectivities are often achieved with respect to the monoalkylene glycol, when only 4 or 5 moles of water are supplied per mole of alkylene oxide. The process of the invention can be carried out in a batch operation. However, particularly for large-scale execution, it is preferable to operate the process continuously. Said continuous process can be carried out in a fixed bed reactor, operated in upflow or downflow. Downflow operation is preferred. The reactor can be maintained under isothermal, adiabatic or hybrid conditions. Isothermal reactors are generally hull and tube reactors, mostly of the muitubular type, where the tubes contain the catalyst and a cooler passes out of the tubes. The adiabatic reactors are not cooled and the product stream leaving them can be cooled in a separate heat exchanger. Under certain chosen circumstances, the catalytic conversion of EO may be incomplete, in which case the remaining EO may be thermally hydrolyzed in the reactor dead space below the catalyst layer. Since this thermal hydrolysis is less specific towards MEG, it is recommended to minimize the retention of liquid in the reactor. This can be achieved by filling the outlet part of the reactor with inert filler material to reduce its volume and / or by adding an inert gas, such as nitrogen, to the reactor feed mixture and operating the reactor under the so-called jet flow conditions. . In order to obtain the appropriate performance-time values, it is recommended to perform the process under conditions of high pressure and temperature. Suitable reaction temperatures are generally in the range from 80 to 200 ° C, whereby temperatures in the range from 90 to 150 ° C are preferred. The reaction pressure is usually selected in the range of 200 to 3000, preferably 200 to 2000 kPa. For the batch operations of the process, the selected reaction pressure is advantageously obtained by pressurizing with an inert gas, such as nitrogen. If desired, gas mixtures can be used, for example a mixture of carbon dioxide and nitrogen is advantageous in certain circumstances. In order to accommodate any swelling of the catalyst during operation, the volume of the reactor can advantageously be greater than the volume occupied by the catalyst, for example 10 to 70% larger volume. It is to be understood that the process of the present invention is not limited to this operation in the presence of the defined catalyst only. In certain situations, particularly when operating in a continuous flow manner, it has been found to be advantageous to subject at least a portion, such as about 30-60% by step, of the alkylene oxide feed stream to partial thermal hydrolysis in the absence of catalyst, before catalytically completing the hydrolysis. has found that partial hydrolysis, even in the absence of a catalyst, is sufficiently selective towards the monoalkylene glycol while on the other hand this measures its effectiveness in saving the catalyst. A problem that may occasionally arise in any process in which the ethylene oxide is being hydrolyzed is the presence of small amounts of amines and / or phosphines as impurities in the product stream. When a strong basic ion exchange resin is used as a solid support for the catalytic anion, the basic groups thereof are quaternary ammonium or quaternary phosphonium groups. It has been found that during operation, small amounts of amines or phosphines tend to unfold from the resin into the product stream. In addition, the amines in the product stream can also originate from corrosion inhibitors, which can be added to the water used in the process. Although the amounts of such amine or phosphine contaminants reaching the final product are generally very small, they can affect the quality of the final product so that it may be desirable to maintain them at the level of detection. For example, trimethylamine (TMA) and / or dimethylamine (DMA) can reach the final product in an amount of up to 10 ppm while the fishy odor of TMA can be detected in an amount as low as 1 ppb. An effective measure in removing the amines and / or phosphines present in the product stream from any process in which the ethylene oxide is being hydrolyzed, including the process of the present invention, is the use of a layer guard containing a Strong acid ion exchange resin that effectively captures amines or phosphines. The strong acid ion exchange resins are those of sulfonic type. Commercially available examples are those known from the trademarks AMBERLYST 15, AMBERJET 1500H, AMBERJET 1200H, DOWEX MSC-1, DOWEX 50W, DIANON SR1B, LEWATIT VP OC 1812, LEWATIT S 100 MB and LEWATIT S 100 Gl. These strong acid ion exchange resins are available in H + form and in salt form, such as the Na + form. When only the H + form of the strong acid resin is used in the guard layer, the product stream after passing through it becomes acid. The use of a mixture of the strong acid ion exchange resin and its H + form and the salt form has the advantage that the pH of the product stream remains close to the neutral. An added advantage of the strong acidic guard layer is that any remaining alkylene oxide that could still be present in the product stream is hydrolyzed to alkylene glycol, albeit with a lower selectivity towards the monoelkylene glycol. In order to accommodate the discharge of the strong acid ion exchange resin during operation, it is advantageous to operate the guard layer in two or more separate containers. The inactive strong acid ion exchange resin can be regenerated by treatment with an acid that is stronger than the sulfonic acid groups in the resin matrix, such as HCl and H2SO4. The 0.1-2 normal hot sulfuric acid has proven to be effective. The following Examples will illustrate the invention. Examples 1. Preparation of the Catalyst 1.1 Two strong basic ion exchange resins of the quaternary ammonium type were used: AMBERJET 4200, a polystyrene / divinylbenzene cross-linked resin mono-dispersed ex Rohm and Haas, in chloride form, exchange capacity 1.4 meq / ml; AMBERLITE IRA-404, a polystyrene / divinylbenzene based resin crosslinked ex Rohm and Haas, in chloride form, exchange capacity 1.05 meq / ml. 1.2 The resin was treated in the following way to immobilize the catalytically active anion (bicarbonate, formate, citrate mono anion) of the resin: - 150 ml of wet resin was formed in slurry in a glass tube filled with water (60 x 2.5 cm); - chloride is exchanged by treatment with sodium bicarbonate, sodium formate or monosodium citrate in each case in aqueous solution (10 molar excess, in 2500 g of water) for about 5 hours (LHSV: 4 1/1 h); - the exchanged resin was washed with 1200 ml of water for 2 hours (LHSV: 4 1/1 h). By this procedure the majority (> 98%) of the chlorine anions in the resin were exchanged for the desired anion. 1.3 The resin was treated in the following manner to immobilize the catalytically active anion (molybdate) of the resin: 140 ml of wet resin was gently stirred in 2300 g of a 30 weight% aqueous solution of sodium molybdate (Na2Mo04) overnight at room temperature; the resin was transferred to a vertical glass ion exchange column and then rinsed by passing water (2500 g) at room temperature through the column (LSVH: 3.4 1/1 h); - subsequently 6500 g of an aqueous sodium molybdate solution was passed through the column at room temperature (LHSV 1.7 1/1 h) and then treated with 1500 g of hot molybdate solution (75 ° C) (3% step); LHSV 3.4 1/1. H); - finally, the rinsing was carried out with 3000 g of hot water (75 ° C) and 3000 g of water at room temperature, respectively (LHSV 3.9 1/1 ). By this procedure the majority (> 98%) of the chlorine anions in the resin were exchanged for the desired anion. 1.4 A weak acid ion exchange resin of the methacrylate type was used: AMBERLITE IRC-50, a crosslinked polymethacrylate / divinylbenzene resin ex Rohm and Haas, in hydrogen form, exchange capacity 3.25 meq / ml; 1.5 A strong acid ion exchange resin of the sulphonic acid type was used: AMBERLYST 15, a cross-linked polysterene / divinylbenzene resin ex Rohm and Haas, in hydrogen form, exchange capacity 1.7 meq / ml. 1.6 The desired catalyst composition was prepared by mixing the catalyst based on the strong basic ion exchange resin (AMBERJET 4200, AMBERJET IRA-404) with the appropriate amount of acid ion exchange resin (AMBERLITE IRC-50, AMBERLYST 15) . II. Examples 1-22, EO hydrolysis batch A 250 ml autoclave was filled with the catalyst (30 mmol of total catalyst, thus mmol of quaternary ammonium on AMBERJET 4200 and mmol H + on IRC-50) and water (100 g, 5.55 mol). The gas cap was purged 3 times with nitrogen and an initial pressure of 1000 kPa was used. The mixture was heated to 100 ° C. The ethylene oxide (44 g, 1 mol) was added slowly under stirring (500 rpm). The reaction mixture was maintained under continuous stirring for 6 hours at 100 ° C. A sample of the final run was taken for GLC analysis. The results (EO conversion and MEG selectivity data) are summarized in Table 1 TABLE 1 or CM SJ 3TEG) **: Selectivity towards MEG (% mol) = 100 x MEG / (MEG + 2DEG + 3TEG).

WHAT OR c \? The results shown in Table 1 indicate that the acid ion exchange resins have little catalytic activity (base selectivity of the reaction without any addition, example 1) rather than their addition together with a basic ion exchange base catalyst does not decrease their catalytic effects III. Examples 23-27, Catalyst stability test. The thermal stability was tested under severe conditions by placing 20 ml of the catalyst in a 65 cm long 0.5 inch wide Hoke tube fitted with a heating jacket using a hot oil system. The water was pumped with an LHSV of 1 1/1 h over the catalyst layer at 150 ° C and a pressure of 1000 kPa for 48 or 168 hours. Then, the catalyst sample was removed from the reactor. The strong basic capacity (quaternary ammonium groups), the weak basic capacity (groups of tertiary anima) and the total capacity of the anion (the sum of the two previous capacities) in the fresh and used catalyst were determined by titration and the % difference (change during use). The results are summarized in Table 2.

TABLE 2 or m WHAT IT OR CM The results shown in Table 2 indicate that this severe accelerated stability test, the strong basic IER base catalyst in the presence of a small amount of acid ion exchange resin is more than 2 times more stable than the corresponding catalyst without the acid ion exchange resin. IV. Examples 28-29, continuous EO hydrolysis Example 28 The AMBERJET 4200 / HCO3"(bicarbonate) + IRC 50 (molar ratio 4/1) catalyst was used in this test, where the process parameters were varied (water molar ratio: EO between 7.5 and 20.6, LHSV between 0.92-2.82 and maximum layer temperature between 94-124 ° C.) The reactor was a 9 mm inner diameter stainless steel tube, with a hot oil heating liner, and was charged with 23 ml of catalyst EO / water feed was pumped in upflow through the catalyst layer EO liquid was pumped into the reactor by a plug pump (BHS-Labotron LDP-5) Before entering the catalyst layer This EO was mixed in line with water, it was pumped by means of a HPLC pump, the reaction temperature was controlled by the temperature of the oil, and in the center of the catalyst layer was placed a thermal well with a thermal pair to measure the temperatures of layer.The effluent The reactor was cooled and collected in a product container from which the samples were taken at time intervals for GLC analysis. The results are summarized in Table 3.1: Table 3.1 - Example 28 * Conversion EO (% mol) = 100 x (MEG + 2DEG + 3TEG) / (EO + MEG + 2DEG + 3TEG) **: Selectivity towards MEG (X mol) = 100 x MEG / (MEG + 2DEG + 3TEG).

Comparative Example 29 For comparison of the results of a similar test using an AMBERJET 4200 / bicarbonate catalyst (thus without IRC-50 stabilizer), Table 3.2 is presented. It is noteworthy that in this experiment a fixed molar ratio of water / EO (7.5) was used. The comparison with the results of Table 3.1 to this molar ratio shows that the addition of IRC-50 has no detrimental effect on the MEG selectivity in said fixed layer continuous mode operation. Table 3.2 - Comparative Example 29 *: Conversion EO (% mol) = 1 00 x (MEG + 2DEG + 3TEG) / (EO + MEG + 2DEG + 3TEG) * *: Selectivity towards MEG (% mol) = 1 00 x MEG / (MEG + 2DEG + 3TEG).

V. Examples 30-33, continuous EO hydrolysis Example 30 v Comparative Example 31 AMBERJET 4200 / fonnate + IRC-50 catalyst (ratio 4/1 mol / mol, Example 30) was used in a continuous fixed layer experiment. The long-term performance was compared to that of the AMBERJET 4200 / format (Comparative Example 3 1) under exactly identical process conditions. The experiments were carried out in a one-time mode. The 24 cm long reactor consisted of a 20 mm (internal diameter) glass tube in a 34 mm wide stainless steel tube. A Teflon (PTFE) layer was used as an insulator between the glass reactor tube and the external SS tube. An electric heating system was used in the external stainless steel tube to compensate for heat losses; The temperature point for this heating device was determined at the temperature of the water supply / EO reactor. The feed water was preheated to achieve the desired reactor inlet temperature prior to mixing with EO. The temperature of the feed was measured using a thermal pair placed in the upper part of the reactor and the outlet temperature was measured using a thermal pair just below the catalyst layer at the outlet of the reactor. The process conditions during these experiments are summarized in Table 4 1. Table 4.1 In each example the reaction was run to the cut when the swelling of the catalyst resulted in an increase in volume of 55 vol%. This volume increase was achieved for run time 2347 in Comparative Example 31, but only for run time 4037 in Example 30, which is in accordance with the present invention. EO conversion and MEG selectivity were followed in each Example until cut to 55% swelling volume of the respective catalyst. The results are summarized in Tables 4.2 and 4.3, which show that the addition of IRC-50 to the AMBERJET 4200 catalyst / format had no significant effect on the catalytic performance in terms of EO conversion and MEG selectivity under the process conditions. Table 4.2 - Example 30 Table 4.3 - Comparative Example 31 Example 32 and Comparative Example 33 The catalysts AMBERJET 4200 / mono-anion citrate + IRC-50 and AMBERJET 4200 / mono-anion citrate (Example 32 and Comparative Example 33 respectively) were compared in long-term experiments under the same conditions as in the Exus 30 and 31. In each Example the reaction was run to the cut when the swelling of the catalyst resulted in a volume increase of 55 vol%. This volume increase was achieved for run-time 2645 in Comparative Example 33, but only for run-time 3246 in Example 32, which is in accordance with the present invention. The EO conversion and the MEG selectivity were followed in each Example until the cut to 55% swelling volume of the respective catalyst. The results are summarized in Tables 5.1 and 5.2, which demonstrate that the addition of IRC-50 to the AMBERJET 4200 / citrate catalyst had no significant effect on the catalytic performance in terms of EO conversion and MEG selectivity under the process conditions. Table 5.1 - Example 32 Table 5.2 - Example 33 It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (8)

1. CLAIMS: Having described the foregoing, the claim contained in the following claims is claimed as property: 1. A process for the preparation of an alkylene glycol by the reaction of an alkylene oxide with water in the presence of a solid catalyst composition including a resin of strong basic ion exchange coordinated with one or more anions, which are chosen from a group of metalates, carboxylates, bicarbonate and bisulfite, and a stabilizing additive which is an acid ion exchange resin.
2. 2. A process according to claim 1, characterized in that the acid ion exchange resin is of the weak acid methacrylate type.
3. 3. A process according to claim 1 or 2, characterized in that the strong basic ion exchange resin is of the quaternary ammonium type.
4. 4. A process according to claim 1 or 2, characterized in that the strong basic ion exchange resin is of the quaternary phosphonium type.
5. 5. A process according to any of claims 1 to 4, characterized in that in terms of exchange capacity or equivalent of active sites, the relative amount of acid ion exchange resin is from 10 to 200%, based on the capacity total of the strong basic ion exchange resin.
6. 6. A process according to any of claims 1 to 5, characterized in that the carboxylate is formate.
7. 7. A process according to any of claims 1 to 5, characterized in that the carboxylate is a polycarboxylic acid derivative having in its chain molecule one or more carboxyl groups and one or more carboxylate groups, the carboxy groups being lo and / or individual carboxylates separated from one another in the chain molecule by a separation group consisting of at least one atom.
8. 8. A process according to claim 1, characterized in that the carboxylate is citrate.