KR20060054364A - Method for the hydrodecomposition of ammonium formates in polyol-containing reaction mixtures - Google Patents

Abstract

Disclosed is a method for removing trialkylammonium formate from methylolalkanes obtained by condensing formaldehyde with a higher aldehyde. The inventive method is characterized in that trialkylammonium formate is decomposed at an increased temperature on a catalyst which is placed on a titanium dioxide support and contains ruthenium in the presence of a gas containing hydrogen. Said method makes it possible to separate the trialkylammonium formate from methylolalkanes produced according to the organic Cannizzaro method and the hydration method.

Description

Methods for the Hydrodecomposition of Ammonium Formates in Polyol-Containing Reaction Mixtures

The present invention relates to the field of organic chemical industry. More specifically, the present invention provides a process for the efficient hydrocracking of trialkylammonium formate present in methylolalkanes formed from the process of using trialkylamine as catalyst in the preparation of methylolalkanal and forming formic acid as a byproduct. To provide.

Condensation of formaldehyde with the higher CH-acid alkanal to form methylol-alkanal, generally dimethylolalkanal and trimethylolalkanal, and the conversion of the obtained compound to polyol are widely used in the chemical industry. It is a process. Examples of important triols obtained in this way are trimethylolpropane, trimethylolethane and trimethylolbutane, which are widely used in the preparation of surface coatings, urethanes and polyesters. Further important compounds are pentaerythritol obtained by condensation of formaldehyde and acetaldehyde, and neopentyl glycol from isobutyraldehyde and formaldehyde. Pentaerythritol, such a tetrahydric alcohol, is frequently used in the surface coating industry and is also very important in the manufacture of explosives.

The polyols mentioned can be prepared by various methods. One method is the Cannizzaro process, which is subdivided into the inorganic Cannizzaro method and the organic Cannizzaro method. In the inorganic cannizzaro process, excess formaldehyde is reacted with the corresponding alkanal in the presence of a stoichiometric amount of an inorganic base such as NaOH or Ca (OH) ₂ . In the second step, the methylolalkanal formed in the first step is disproportionated with excess formaldehyde to form the corresponding polyol and formate for each base, e.g. sodium or calcium formate.

In the organic cannizzaro process, tertiary amines, generally trialkylamines, are used instead of the inorganic base. The reaction proceeds as described above, in which one equivalent of ammonium formate of the corresponding amine is formed. It may be further worked up by a suitable method and at least recovers the amine and returns to the reaction. The crude polyols obtained can be worked up in various ways to provide pure polyols.

A further improvement is the hydrogenation process in which suitable alkanal and formaldehyde are reacted with each other in the presence of catalytic amounts, generally about 5 to 10 mol% tertiary amine, rather than in stoichiometric amounts. In this method, the reaction is stopped at the stage of 2,2-dimethylolalkanal and then converted to trimethylolalkane by hydrogenation. Detailed description of this effective method can be found in Applicant's WO 98/28253.

Among them, various modifications of this hydrogenation method are described in patent applications DE-A-2507461, DE-A-2702582, DE-A-2813201 and DE-A-3340791.

Although the hydrogenation process advantageously does not form a quantitative formate as in the organic cannizzaro process, trialkylammonium formate is formed as the product of the cross-canizaro reaction which takes place in small amounts as a secondary reaction.

Trialkylammonium formate is reacted under special conditions, for example under dehydration or heating of the obtained trimethylolalkane solution, to form trialkylamine and trimethylolpropane formate. They lower the yield of trimethylolalkane and are difficult to separate without undesirable decomposition reactions. Therefore, particular attention is given to the removal of trialkylammonium formates.

DE # 198 # 48_569 discloses a process for the decomposition of formate of tertiary amines present as a byproduct in trimethylolalkane solutions prepared by the organic cannizzaro method. These formates are preferably decomposed into hydrogen and carbon dioxide and / or water and carbon monoxide and tertiary amine by heating in the presence of a modified noble metal catalyst and under superatmospheric pressure. In this method the formate conversion is not satisfactory and the formation of further byproducts is also observed.

DE 101 52 525 discloses the decomposition of trialkylammonium formate on a heterogeneous catalyst comprising at least one metal of groups 8 to 12 of the periodic table, particularly preferably supported copper-, nickel- and / or A cobalt containing catalyst is provided.

Furthermore, the process described above is only limited to the effective workup of the trimethylolalkane mixture obtained by the hydrogenation process in which only catalytic amounts of trialkylamine are used and the resulting mixture therefore contains only minor amounts of trialkylammonium formate. It is only suitable.

It is an object of the present invention to provide a method suitable for the workup of the reaction mixture obtained by the hydrogenation method and the reaction mixture obtained by the organic cannizzaro method. Furthermore, this method should be capable of decomposing trialkylammonium formate at a higher conversion than is possible with the prior art. In addition, this degradation leads to degradation products that are willing to be handled at the plant production scale and do not initiate any incidental reactions, providing a more economical method for producing high purity trimethylolpropane.

The inventors have found that this object is achieved by a method for removing trialkylammonium formate from methylolalkanes which can be obtained by the condensation of higher aldehydes with formaldehyde. The method involves decomposing trialkylammonium formate at elevated temperature in the presence of a hydrogen containing gas on a catalyst comprising ruthenium supported on titanium dioxide.

Methylolalkanes that can be worked up by the method of the present invention are, for example, neopentyl glycol, pentaerythritol, trimethylolpropane, trimethylolbutane, trimethylolethane, 2-ethyl-1,3-propanediol , 2-methyl-1,3-propane-diol, glycerol, dimethylolpropane, dipentaerythritol and 1,1-, 1,2-, 1,3- and 1,4-cyclohexane-dimethanol.

In the process herein, it is preferred to remove the trialkylammonium formate from the trimethylolalkane prepared by the organic cannizzaro method or the hydrogenation method, preferably under hydrogenation conditions. Preferably, it is preferred to purify trimethylolpropane, particularly preferably trimethylolpropane (hereinafter simply referred to as "TMP") produced in the hydrogenation process.

The preparation of crude TMP containing trialkylammonium formate by the Cannizzaro method is described, for example, in DE # 198 * 48 * 569.

In the hydrogenation process, TMP is obtained by condensation of n-butyraldehyde with formaldehyde under catalytic amount of tertiary amine and then catalytic hydrogenation of the resulting mixture of dimethylolbutanal. The crude TMP formed in this inorganic cannizzaro process does not contain any alkali metal or alkaline earth metal formate or other impurities. Likewise, unlike the products obtained from the organic cannizzaro process, the crude TMP contains only small amounts, about 5 to about 10 mol% of trialkylammonium formate or free trialkylamine.

Crude TMPs resulting from hydrogenation and undergoing the process of the present invention include methanol, trialkylamine, trialkylammonium formate, longer chain linear and branched alcohols and diols such as methylbutanol or ethylpropanediol; Addition products of formaldehyde and methanol to trimethylolpropane; Acetals such as dimethylolbutyraldehyde TMP acetal and di-TMP and water and trimethylolpropane.

10 to 40 weight percent trimethylolpropane, 0 to 10 weight percent 2,2-dimethylolbutanal, 0.5 to 5 weight percent methanol, 0 to 6 weight percent methylbutanol, 1 to 10 weight percent trialkyl Ammonium formate, 0-5% by weight of 2-ethyl-propanediol, 0.1-10% by weight of high boiling materials such as di-TMP or other adducts and 5 to 80% by weight of water using crude hydrogenation products It gave a good result. Crude hydrogenation products having this composition can be obtained, for example, by the process described in WO 98/28253. Prior to purification of the present invention that decomposes trialkylammonium formate, the crude hydrogenation product can first be worked up by continuous distillation as described in Examples 2 and 3 of DE-A-199 63 435. However, the purification of the crude hydrogenation product according to the invention is preferably carried out without prior treatment by distillation.

The present invention also provides a ruthenium supported on a titanium dioxide shaped body obtained by treating commercially available titanium dioxide with 0.1-30% by weight of an acid in which titanium dioxide is almost insoluble before or after molding, and the method use. Ruthenium can be used in the form of pure metals or in the form of their compounds, for example oxides or sulfides.

Catalytically active ruthenium can be applied as known to TiO ₂ preprocessed as a support.

Preferred titanium dioxide supports for use in ruthenium containing catalysts can be obtained by treatment with an acid of from 0.1 to 30% by weight (based on titanium dioxide) in which little or no titanium dioxide is dissolved before or after molding as described in DE 197 38 464. have. Preference is given to using anatase modified titanium dioxide. Examples of suitable acids are formic acid, phosphoric acid, nitric acid, acetic acid and stearic acid.

The active ingredient ruthenium may be applied in the form of a ruthenium salt solution to the titanium dioxide support obtained in this way using one or more soaking steps. The dipped support is then dried and calcined if necessary. However, it is also possible to precipitate ruthenium from the ruthenium salt solution, preferably sodium carbonate, on titanium dioxide present as a powder in the water suspension. This precipitate is washed, dried if necessary, calcined and molded. Furthermore, volatile ruthenium compounds such as ruthenium acetylacetonate or ruthenium carbonyl can be made into the gas phase and applied to the support as is known (chemical vapor deposition).

The supported catalyst thus obtained may have a known final form. Examples are extrudates, pellets or granules. Prior to use, the ruthenium catalyst precursor is reduced by treating with a hydrogen containing gas, preferably above 100 ° C. Preferably, the catalyst is preferably passivated by oxygen-containing gas mixture, preferably at 0-50 ° C., preferably at room temperature, by air / nitrogen mixture before use in the present method. It is also possible to install the catalyst in oxidized form in a hydrogenation reactor and reduce it under reaction conditions.

The catalyst of the present invention has a ruthenium content of 0.1 to 10% by weight, preferably 2 to 6% by weight, based on the total amount of catalyst catalytically comprising an active metal and a support. The catalyst of the present invention may have a sulfur content of 0.01 to 1% by weight based on the total amount of catalyst (sulfur measurement is performed coulometrically).

Ruthenium surface area is 1 to 20 m ² / g, preferably 5 to 15 m ² / g, BET surface area (determined according to DIN 66 131) is 5 to 500 m ² / g, preferably 50 to 200 m ² / g.

The catalyst of the present invention has a pore volume of 0.1 to 1 μml / g. Moreover, the catalyst has a cutting hardness of 1 to 100N.

The ruthenium-containing supported catalyst on titanium dioxide for the decomposition of the trialkylammonium formate present in the crude TMP according to the invention described above is also suitable for hydrogenation of the precursor (2,2-dimethylolbutanal) of TMP. Do.

In this case, since the decomposition of trialkylammonium formate is carried out in the hydrogenation reactor of the hydrogenation method described in WO # 98/28253 and no additional reactor is required, hydrogenation of dimethylolbutanal and decomposition of trialkylammonium formate are avoided. It is particularly economical to use the same catalyst for this purpose. Likewise, however, the decomposition of trialkylammonium formate by the present method can be carried out in a separate reactor.

In the present process, the decomposition of trialkylammonium formate is generally carried out at 100 to 250 ° C, preferably at 120 to 180 ° C. The pressure used is generally in the range of greater than 1 × 10 ⁶ Pa, preferably 2 × 10 ⁶ to 15 × 10 ⁶ Pa.

The present method can be carried out continuously or batchwise, preferably in a continuous method.

In the continuous process, the amount of crude trimethylolalkane from the hydrogenation process or organic cannizzaro method is preferably about 0.05 to about 3 kilograms, more preferably about 0.1 to about 1 kilograms per liter of catalyst per hour.

The process is carried out under hydrogenation conditions, ie using hydrogenation added from an external source.

As the hydrogenation gas, it is possible to use a gas containing free hydrogen which does not contain a harmful amount of a catalyst poison such as, for example, CO. For example, it is possible to use offgas from a reformer. Preferably, pure hydrogen is used.

The method is described in detail by the following examples.

I. Preparation of crude TMP by the method WO 98/28 253

An aqueous formaldehyde solution (4300 ccg / l in the form of a 40% aqueous solution) and n-butyr in a device with two heatable stirring vessels connected to each other by an overflow pipe and having a total capacity of 72 ml Fresh trimethylamine in the form of 45% concentration aqueous solution was fed as aldehyde (1 × 800 μg / h) and catalyst (130 μg / h). The reactor was kept at 40 ° C.

The output was fed directly to the top of a falling film evaporator with an overlap column (11 bar steam pressure for heating) and fractional distillation under atmospheric pressure, n-butyraldehyde, ethyl acrolein, formaldehyde, water and trimethyl A low boiling top product consisting essentially of an amine and a high boiling bottom product was obtained.

This top product was continuously condensed and recycled to the reactor described above.

High-boiling bottom product from the evaporator (about 33.5 kg / h) is continuously mixed with fresh trimethylamine catalyst (50 g / h in the form of a 45% aqueous solution) and heated to provide 12 L of empty volume with random packing. Introduced into a possible tube reactor. The reactor was kept at 40 ° C.

The output from the after-reactor is continuously introduced to the top of the distillation apparatus for further distillation for formaldehyde removal (vapor pressure for heating 11 bar) and fractional distillation to ethyl acrolein, formaldehyde, water and trimethyl A low boiling top product and a high boiling bottom product consisting essentially of amines were provided. The low boiling top product (27 kg / h) was continuously condensed and recycled to the first stirred vessel and the high boiling bottom product was collected.

The bottom product thus obtained consists essentially of water together with dimethylol butyraldehyde, formaldehyde and trace amounts of monomethylol butyraldehyde. The bottom product is then subjected to continuous hydrogenation. For this purpose, the reaction solution was operated in a circulating / downflow mode in the main reactor at 90 bar and 115 ° C. The catalyst was prepared by a method analogous to catalyst J in DE 198 09 418. It contains 40% CuO, 20% Cu and 40% TiO ₂ . The apparatus used was a 10 m long heated main reactor (inner diameter: 27 mm) and a 5.3 m length of post-reactor (inner diameter: 25 mm). The flow around the circuit is 25 l / h of liquid and the feed to the reactor was set at 4 kg / h. Thus, 4 kg / h of hydrogenated product was withdrawn. The hydrogenation products include 22.6 wt% TMP, 1.93 wt% dimethylolbutanal, 1.4 wt% methanol, 1.1 wt% methylbutanol, 0.7 wt% ethylpropanediol; 1.2% by weight of adducts of TMP and formaldehyde and methanol and TMP; It has a composition of less than 0.1 wt% TMP formate, 1.2 wt% TMP-dimethylbutanal acetal, 2.9 wt% high boiling point, 0.57 wt% trimethylammonium formate and 66.2 wt% water.

II. Measurement of porosity

The porosity of the catalyst was determined by Hg injection according to DIN 66 133.

III. Determination of BET Surface Area

The BET surface area of the catalyst was determined by DIN # 66 131.

IV. Determination of cutting hardness

To determine the cutting hardness, the specimens were divided into cutters. The force exerted on the cutter to cut across the specimen is the cutting hardness [unit N (Newtons)].

V. Formate Content by Ion Chromatography

The formate content was determined by ion chromatography according to DEV ISO 10304-2.

Example 1: Ru / TiO ₂  Preparation of the catalyst

121.3 g ruthenium nitrosyl nitrate solution (Ru content: 10.85 wt%) was diluted with 90 ml of water. 250 g of titanium dioxide extrudate in the form of a 1.5 mm extrudate having a BET surface area of 104 m ² / g and a porosity of 0.36 ml / g prepared as described in DE 197 38 463, Example 3 Was slowly immersed in. This wet extrudate was then dried at 100 ° C. for 2 hours and at 120 ° C. for 16 hours. The catalyst was activated by reduction with 10 l / h hydrogen (standard) and 10 l / h nitrogen (standard) at 300 ° C. for a period of 4 hours. This catalyst was then passivated with an air / nitrogen mixture at room temperature.

The Ru content of the finished catalyst extrudate was 4.2% by weight, BET surface area was 103 m ² / g, pore volume was 0.26 ml / g, ruthenium surface area was 12 m ² / g and the cutting hardness was 21.2 N.

Examples 1-4

The TMP prepared and used as described above is 22.6 wt% TMP, 1.93 wt% dimethylolbutanal, 1.4 wt% methanol, 1.1 wt% methylbutanol, 0.7 wt% ethylpropanediol, formaldehyde and methanol and the TMP adduct 1.2 wt%, less than 0.1 wt% TMP formate, 1.2 wt% TMP dimethylbutanal acetal, 2.9 wt% high boiling point, 0.57 wt% trimethylammonium formate and 66.2 wt% water. 180 μl of this crude solution was treated with hydrogen at 180 ° C., 90 bar in the presence of a catalyst as shown in Table 1 and pre-reduced at 180 ° C. and 25 bar. After one hour, the dimethylolbutanal content was determined by gas chromatography. Formate concentration was determined by ion chromatography. The results obtained are summarized in Table 1.

No. catalyst shape Catalyst amount [g] DMB ³ Area% ¹ Formate Weight% ² Formate conversion rate [%] Starting material 1.93 0.57 - One Cu / TiO ₂ (DE 198 09 418) 3x3 mm pellet 18.6 <0.05 0.39 32 2 Ni / SiO ₂ / Al ₂ O ₃ / ZrO ₂ (EP 0672 452) 1.5 mm extrudate 12.7 <0.05 0.51 11 3 Co / MnO ₂ / P ₂ O ₅ (EP 0 742 045) 4 mm extrudate 21.3 <0.05 0.18 68 4 Ru / TiO ₂ 1.5 mm extrudate 14.8 <0.05 0.006 99

¹ GC analysis (detection without water)

Crystallized by ² Ion Chromatography

³ DMB = 2,2-dimethylbutanal

From the table, it can be seen that ammonium formate can be catalytically decomposed with high conversion on the ruthenium catalyst used according to the invention at 150 ° C., and these catalysts are significantly more effective than copper, nickel and cobalt catalysts. Off-gas analysis showed that methane was the main product of formate decomposition.

Claims (7)

 Decomposing trialkylammonium formate at elevated temperature in the presence of a hydrogen containing gas on a catalyst comprising ruthenium supported on titanium dioxide, A method for removing trialkylammonium formate from methylolalkanes obtained by condensation of higher aldehydes with formaldehyde. The method for removing trialkylammonium formate from methylolalkane according to claim 1, wherein the ruthenium content of the catalyst is 0.1 to 10% by weight. A ruthenium supported on a titanium dioxide shaped body obtained by treating commercially available titanium dioxide with 0.1 to 30% by weight of an acid in which titanium dioxide is almost insoluble before or after molding is used. To remove trialkylammonium formate from methylolalkane. The method according to any one of claims 1 to 3, which is performed at 100 to 250 ° C. Process for removing trialkylammonium formate from methylolalkane. The method of any one of claims 1-4, wherein the trialkylammonium formate is removed from methylolalkane, which is carried out at a pressure of 1 × 10 ⁶ to 15 × 10 ⁶ Pa. ⁶ . The process according to any one of claims 1 to 5, which is carried out in a hydrogenation reactor in a hydrogenation process. A catalyst comprising ruthenium supported on a titanium dioxide shaped body obtained by treating commercially available titanium dioxide with 0.1-30% by weight of an acid in which titanium dioxide is almost insoluble before or after molding.