DE10334489A1 - Trialkylammonium by-products obtained in methylolalkane products from Cannizzaro or hydrogenation reactions are decomposed using a novel titanium dioxide-supported ruthenium-containing catalyst - Google Patents

Abstract

Removal of trialkylammonium formates (TAAF) from methylolalkanes obtained by condensation of formaldehyde with higher aldehydes involves decomposing the TAAF at elevated temperature on a titanium dioxide- supported ruthenium-containing catalyst in presence of a hydrogen-containing gas. An independent claim is also included for such a catalyst in which commercially-available titanium dioxide is treated before or after shaping to form the support with 0.1-30 wt.% of an acid in which the TiO 2 is difficultly soluble.

Description

The This invention relates to the field of industrial organic Chemistry. More specifically, the present invention relates to a method for the effective hydrogenating decomposition of methylolalkanes contained in Trialkylammonium formate, which from the in the Methylolalkanal preparation as a catalyst used trialkylamine and by-product formed formic acid arises.

The Condensation of formaldehyde with CH-acidic higher alkanals to methylolalkanals, in general Dimethylol- and Trimethylolalkanalen and transfer of the Compounds obtained in polyols is a widely used method in chemistry. examples for important triols obtained in this way are trimethylolpropane, trimethylolethane and trimethylolbutane used in the manufacture of paints, urethanes and Polyesters have found a wide application area. Further important compounds are pentaerythritol, obtainable by condensation of Formaldehyde and acetaldehyde, and neopentyl glycol from iso-butyraldehyde and formaldehyde. The tetravalent alcohol pentaerythritol will also often used in the paint industry, but also has a great importance obtained in the manufacture of explosives.

The mentioned polyols can be prepared by various methods. One method is the so-called Cannizzaro process, which is still subdivided into the inorganic and the organic Cannizzaro process. In the inorganic variant, an excess of formaldehyde is reacted with the corresponding alkanal in the presence of stoichiometric amounts of an inorganic base such as NaOH or Ca (OH) ₂ . The methylolalkanal formed in the first stage reacts in the second stage with the excess formaldehyde in a disproportionation reaction to the corresponding polyol and the formate of the corresponding base, for example sodium or calcium formate.

At the Organic Cannizzaro method is used instead of inorganic Base a teritäes Amine, generally a trialkylamine used. The reaction goes like above, where one equivalent Ammonium formate of the corresponding amine is formed. This can through appropriate measures be worked up further, whereby at least the amine recovered and can be attributed to the reaction. The crude polyol obtained can in various ways to pure polyol be worked up.

A Further development is the hydrogenation process, in which a corresponding Alkanene and formaldehyde not in the presence of at least stoichiometric Quantities, but of catalytic amounts of a tertiary amine, generally about 5 to 10 mol%, reacted with each other become. The reaction remains at the 2,2-dimethylolalkanal level stand, then is converted by hydrogenation in trimethylolalkane. The description of the effective method can be found in WO 98/28253 of the Applicant.

Various Variants of this hydrogenation process are described inter alia in the applications DE-A-25 07 461, DE-A-27 02 582, DE-A-28 13 201 and DE-A-3340791.

At the Although hydrogenation advantageously fall no stoichiometric Quantities of formate as in the organic Cannizzaro process, Nevertheless, trialkylammonium formate is one of the products in very low yield Scope as a side reaction running crossed Cannizzaro reaction educated.

trialkylammonium react under certain conditions, such as draining or Heating of containing trimethylolalkane solutions, to trialkylamine and Trimethylolpropanformiaten. These reduce the yield of trimethylolalkane and can difficult without unwanted Decomposition reaction are split. There was therefore interest in the Separation of trialkylammonium formates.

DE 198 48 569 discloses a process for the decomposition of formates of tertiary amines contained as by-products in trimethylolalkane solutions prepared by the organic Cannizzaro process. These formates are decomposed, preferably in the presence of modified noble metal catalysts and elevated pressure, by heating in hydrogen and carbon dioxide and / or water and carbon monoxide and the tertiary amine. The Formiatumsätze in this process are unsatisfactory, also the formation of other by-products is observed.

Out DE 101 52 525 For example, the decomposition of trialkylammonium formates to heterogeneous catalysts containing at least one metal of groups 8 to 12 of the periodic table is known Copper-nickel and / or cobalt-containing catalysts are particularly preferred.

Also the above method is only conditionally effective Workup of a contained by the so-called hydrogenation process Trimethylol mixture, in which only catalytic amounts of trialkylamine are used and thus also only small amounts of trialkylammonium formate contains.

It is therefore the object of the present invention, a method to provide, both for the workup by the hydrogenation process as well as obtained by the organic Cannizzaro method mixtures suitable is. This procedure should continue to allow Trialkylammoniumformiate with higher revenues, as can the methods known from the prior art, to decompose. Furthermore, this decomposition should be too large-scale good manageable decomposition products that do not cause side reactions trigger, so a more economical process for producing high purity Trimethylolpropane available to deliver.

These Task is solved by a process for removing trialkylammonium formate Methylolalkanes obtained by condensation of formaldehyde with a higher Aldehyde were obtained, this process being characterized is that trialkylammonium formate at elevated temperature at a Titanium dioxide supported Ruthenium-containing catalyst in the presence of hydrogen-containing Gas is decomposed.

For the purification by the method according to the invention suitable methylolalkanes are, for example, neopentyl glycol, pentaerythritol, Trimethylolpropane, trimethylolbutane, trimethylolethane, 2-ethyl-1,3-propanediol, 2-methyl-1,3-propanediol, glycerol, dimethylolpropane, dipentaerythritol and 1,1-, 1,2-, 1,3- and 1,4-cyclohexanedimethanol.

in the Framework of the method according to the invention are preferred trimethylolalkanes, according to the organic Cannizzarro or the hydrogenation process, under hydrogenation conditions purified from Trialkylammoniumformiaten. Are preferred after the Hydrogenation trimethylolalkanes prepared, particularly preferred Trimethylolpropane, abbreviated to TMP, purified.

The preparation of trialkylammonium formate-containing crude TMP by the Cannizzaro process is, for example, in DE 198 48 569 disclosed.

The TMP is obtained by the hydrogenation process by condensation of n-butyraldehyde with formaldehyde in the presence of catalytic amounts a tertiary Amines and subsequent catalytic hydrogenation of the resulting Dimethylolbutanal-mixture. This Contains crude TMP no alkali or alkaline earth formates or other impurities, produced by the inorganic Cannizzaro process. Also contains the crude TMP only small amounts, about 5 to 10 mol% of trialkylammonium formates or free trialkylamine, unlike the organic Cannizzaro method.

The the hydrogenation stemmende and the cleaning process according to the invention to be subjugated crude TMP contains in addition to trimethylolpropane and water, methanol, trialkylamine, Trialkylammonium formate, longer chain linear and branched alcohols and diols, for example methylbutanol or ethylpropanediol, addition products of formaldehyde and methanol trimethylolpropane, acetals such as dimethylol butyraldehyde TMP acetal as well as the so-called Di-TMP.

Quality Results were obtained with hydrogenation effluents containing 10 to 40% by weight of trimethylolpropane, 0 to 10% by weight of 2,2-dimethylolbutanal, 0.5 to 5% by weight of methanol, 0 to 6% by weight of methyl butanol, 1 to 10% by weight of trialkylammonium formate, 0 to 5% by weight of 2-ethylpropanediol; 0.1 to 10 wt .-% high boilers such Di-TMP or other addition products and 5 to 80 wt .-% water exhibit. hydrogenation products such a composition can be obtained, for example are prepared according to the method described in WO 98/28253. It is possible the thus obtained hydrogenation according to Examples 2 and 3 of DE-A-199 63 435 before the purification according to the invention for decomposition of the trialkylammonium formate initially by continuous Work up distillation. However, preference is given to the purification according to the invention the hydrogenation without prior distillative treatment.

The present invention furthermore relates to a catalyst comprising titanium dioxide form The titanium dioxide bodies are obtained by treating commercially available titanium dioxide before or after molding with 0.1 to 30% by weight of an acid in which titanium dioxide is sparingly soluble, which is used in the process according to the invention. Ruthenium can be used both in the form of the pure metal and as its compound, for example, oxide or sulfide.

The catalytically active ruthenium is applied by conventional methods, preferably on prefabricated TiO ₂ as a carrier material.

A titanium dioxide support which is preferably suitable for use in the ruthenium-containing catalyst may accordingly be used DE 197 38 464 by treating commercially available titanium dioxide before or after molding with 0.1 to 30% by weight of an acid, based on titanium dioxide, in which the titanium dioxide is sparingly soluble. Titanium dioxide is preferably used in the anatase modification. As such acid, for example, formic acid, phosphoric acid, nitric acid, acetic acid or stearic acid are suitable.

The Active component Ruthenium may be in the form of a ruthenium salt solution the titania support thus obtained in one or more drinking stages be applied.

Subsequently, will the soaked carrier dried and optionally calcined. However, it is also possible Ruthenium from a ruthenium salt solution, preferably with sodium carbonate, as a powder in aqueous Suspension precipitate present titanium dioxide. The precipitated precipitation will be washed, dried, optionally calcined and deformed. Farther can volatile Ruthenium compounds such as ruthenium acetylacetonate or Rutheniumcarbonyl, are converted into the gas phase and in per se known Way on the carrier be applied (chemical vapor deposition).

The thus obtained, carried Catalysts can present in all known packaging forms. Examples are strands, Tablets or granules. Before being used, the ruthenium catalyst precursors are passed through Treatment with hydrogen-containing gas, preferably reduced at temperatures above 100 ° C. Preference is given to the catalysts before they are used in the process according to the invention at temperatures from 0 to 50 ° C, preferably at room temperature, with oxygen-containing gas mixtures, preferably with air-nitrogen mixtures, passivated. It is also possible, to incorporate the catalyst into the hydrogenation reactor in oxidic form and reduce under reaction conditions.

Of the catalyst according to the invention has a ruthenium content of 0.1 to 10 wt .-%, preferably from 2 to 6, based on the total weight of the catalyst from catalytic active metal and carrier, on. The catalyst according to the invention can have a sulfur content of 0.01 to 1 wt .-%, based on the Total weight of the catalyst, wherein the sulfur determination coulometrically.

The ruthenium surface is from 1 to 20 m ² / g, preferably from 5 to 15 and the BET surface area (determined to DIN 66 131) of 5 to 500 m ² / g, preferably from 50 to 200 m ² / g.

The catalysts of the invention have a pore volume of 0.1 to 1 ml / g. Continue drawing the catalysts are characterized by a cutting hardness of 1 to 100 N.

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

The Use of the same catalyst for the hydrogenation of the Dimethylolbutanals and the decomposition of the trialkylammonium formate is particularly economical, there the

decomposition of the trialkylammonium formate in this case in the hydrogenation reactor of Hyd rierverfahrens according to WO 98/28253 can be done and no additional Needed reactor becomes. The decomposition of Trialkylammoniumformiate by the method according to the invention however, it may also be carried out in a separate reactor.

In the context of the process according to the invention, the decomposition of the trialkylam moniumformiate is generally carried out at a temperature of 100 to 250 ° C, preferably 120 to 180 ° C. The pressures used in this case are generally above 1 × 10 ⁶ Pa, preferably 2 × 10 ⁶ to 15 × 10 ⁶ Pa.

The process according to the invention can be carried out either continuously or batchwise be, with the continuous process execution is preferred.

at continuous process management is the amount of crude trimethylolalkane from the hydrogenation process or the organic Cannizzaro method preferably about 0.05 until about 3 kg per liter of catalyst per hour, more preferably about 0.1 to approximately 1 kg per liter of catalyst per hour.

The inventive method is carried out under hydrogenation conditions, i. with an added hydrogenation gas from an external source.

When Hydrogenation gases can Any gases containing free hydrogen may be used and no harmful ones Amounts of catalyst poisons, such as CO, have. For example can Reformer exhaust gases are used. Preferably, pure hydrogen uses.

in the The following is the process of the invention based on embodiments be explained in more detail.

I. Preparation of crude TMP according to WO 98/28 253

A Apparatus consisting of two heatable stirred tanks interconnected by overflow pipes with a capacity of a total of 72 l was washed with fresh, aqueous formaldehyde solution (4300 g / L in the form of 40% aqueous solution and n-butyraldehyde (1800 g / h) and with fresh trimethylamine as Catalyst (130 g / h) in the form of 45% aqueous solution continuously charged. The reactors were at 40 ° C tempered.

Of the Discharge was directly into the upper part of a falling film evaporator passed with attached column (11 bar heating steam) and there at normal pressure by distillation in a low - boiling overhead product, in essentially containing n-butyraldehyde, ethylacrolein, formaldehyde, Separated water and trimethylamine, and a high-boiling bottom product.

The Overhead product was condensed continuously and into those described above Reactors returned.

The high-boiling bottom product from the evaporator (about 33.5 kg / h) was continuously with fresh trimethylamine catalyst (50 g / h, in Form of 45% aqueous Solution) and placed in a heated, provided with packing tubular reactor with a void volume of 12 l. The reactor was there at 40 ° C tempered.

Of the Discharge of the postreactor was continuously in the upper part a further distillation device, the formaldehyde separation (11 bar heating steam), and there by distillation in a low-boiling overhead product, essentially containing ethylacrolein, formaldehyde, water and Trimethylamine, and a high-boiling bottom product separated. The low-boiling overhead product (27 kg / h) was condensed continuously and in the first stirred tank returned, whereas the high boiling bottoms product was collected.

The bottom product thus obtained contained, besides water, essentially dimethylol butyraldehyde, formaldehyde and traces of monomethylol butyraldehyde. It was then subjected to continuous hydrogenation. For this purpose, the reaction solution was hydrogenated at 90 bar and 115 ° C in a main reactor in circulation / trickle mode and a downstream downstream reactor in circulation mode. The catalyst was prepared analogously to J. DE 198 09 418 produced. It contained 40% CuO, 20% Cu and 40% TiO ₂ . The apparatus used consisted of a 10 m long heated main reactor (inner diameter: 27 mm) and a 5.3 m long heated Nachreaktor (inner diameter: 25 mm). The circulation throughput was 25 l / h liquid, the reactor feed was set to 4 kg / h. Accordingly, 4 kg / h of hydrogenation were obtained. The hydrogenation product had the following composition: 22.6% by weight of TMP, 1.93% by weight of dimethylolbutanal, 1.4% by weight of methanol, 1.1% by weight of methyl butanol, 0.7% by weight of ethylpropanediol, 1.2 wt .-% adducts of TMP with formaldehyde and methanol, <0.1 wt .-% TMP formate, 1.2 wt .-% TMP dimethyl butanal acetals, 2.9 wt .-% high boilers, 0 , 57% by weight of trimethylammonium formate and 66.2% by weight of water.

II. Measurement porosity

The Determination of porosity the catalysts were carried out by the HG intrusion method according to DIN 66 133.

III. Determination of BET surface area

The Determination of the BET surface area the catalysts were carried out according to DIN 66 131.

IV. Determination of cutting hardness

to Determination of cutting hardness Samples are cut with a cutting edge. The force with which the cutting edge must be burdened, to achieve a separation of the sample is called the cutting hardness in N (Newton).

V. Determination of formate content with ion chromatography

The Determination of formate content is carried out by means of ion chromatography according to the DEV ISO 10304-2.

Example 1: Catalyst preparation Ru / TiO ₂

121.3 g of a ruthenium nitrosyl nitrate solution (Ru content: 10.85% by weight) was diluted to 90 ml with water. 250 g of titanium dioxide strands in the form of 1.5 mm strands with a BET surface area of 104 m ² / g and a porosity of 0.36 ml / g, respectively DE 197 38 463 , Example 3, were slowly soaked in the ruthenium solution. The wet strands were then dried for 2 h at 100 ° C and 16 h at 120 ° C. The activation of the catalyst by reduction was carried out at 300 ° C with 10 Nl / h of hydrogen and 10 Nl / h of nitrogen over a period of 4 h. Subsequently, the catalyst was passivated at room temperature with air / nitrogen mixtures.

The finished catalyst strands had a Ru content of 4.2 wt .-%, a BET surface area of 103 m ² / g, a pore volume of 0.26 ml / g, a ruthenium surface of 12 m ² / g and a cutting hardness of 21.2 N.

Examples 1 to 4

The TMP prepared as prepared above has the composition 22.6% by weight of TMP, 1.93% by weight of dimethylolbutanal, 1.4% by weight of methanol, 1.1% by weight of methyl butanol, 0.7% by weight of ethyl propane diol, 1.2% by weight Adducts of TMP with formaldehyde and methanol, <0.1% by weight TMP formate, 1.2% by weight TMP dimethylbutanal-acetals 2.9 wt .-% high boilers, 0.57 wt .-% trimethylammonium and 66.2% by weight of water. From this crude solution was added 180 ml in the presence one at 180 ° C and 25 bar prereduced catalyst according to Table 1 with hydrogen at 180 ° C and treated 90 bar. After one hour, the dimethylol butanal content was gas chromatographed determined. The formate concentration was determined using ion chromatography determined. The results obtained are summarized in Table 1.

Out The table shows that the catalytic decomposition of Ammonium formate at 150 ° C to the invention used Ruthenium catalysts with high conversions is possible and significantly more effective is as on copper, nickel and cobalt catalysts. From exhaust gas analyzes goes that methane is the major product of the decomposition of form.

Claims (7)

A process for removing trialkylammonium formate from methylolalkanes obtained by condensation of formaldehyde with a higher aldehyde, characterized in that trialkylammonium formate is decomposed at elevated temperature on a titania-supported ruthenium-containing catalyst in the presence of hydrogen-containing gas. Method according to claim 1, characterized in that the catalyst has a ruthenium content of 0.1 to 10% by weight having. Method according to one of claims 1 or 2, characterized that uses titanium dioxide molded body before, by treating commercially available titanium dioxide after molding with 0.1 to 30 wt .-% of an acid in the titanium dioxide heavy soluble is, is received. Method according to one of claims 1 to 3, characterized that the process is carried out at 100 to 250 ° C. Method according to one of claims 1 to 4, characterized in that it is carried out at a pressure of 1 · 10 ⁶ to 15 · 10 ⁶ Pa. Method according to one of claims 1 to 5, characterized that it is carried out in the hydrogenation reactor of the hydrogenation process. Catalyst containing ruthenium supported on titania moldings, the titania moldings by treating commercially available Titanium dioxide before or after molding with 0.1 to 30 wt .-% of a Acid, sparingly soluble in titanium dioxide is, is received.