DE102013021509B4 - Process for the preparation of 3-hydroxyalkanals - Google Patents

Abstract

Process for the preparation of 3-hydroxyalkanals by reacting an aldehyde of the general formula (I) R1R2H-CC = (O) H with a further aldehyde of the general formula (II) R3-C = (O) H to form an addition product of the general formula ( III) [R3-C (OH) H] xC [R1] a [R2] bC = (O) H, in which R1, R2 and R3 each independently represent hydrogen or an aliphatic hydrocarbon radical of 1 to 8 carbon atoms, x an integer from 1 to 3, a is 0 or 1 and b is 0 or 1 and x + a + b is 3, characterized in that the reaction is carried out in solution at a temperature of 40 to 170 ° C in the presence of binary metal nitrides Formula A (m +) oN (3-) p, in which o can assume the integer values 1 to 3, p can assume the integer values 1 to 4 regardless of this, m means an integer from 1 to 4 and the condition (m + ) · O is equal to (3-) · p, or takes place in the presence of Si3N4.

Description

The present invention relates to a process for the preparation of 3-hydroxyalkanals in the presence of metal nitrides

Polyhydric alcohols or polyols are of considerable economic importance as condensation components for the synthesis of polyesters or polyurethanes, synthetic resin paints, lubricants and plasticizers. Important intermediate products for the production of polyols are 3-hydroxyalkanals, which can be produced by the aldol addition of two aldehydes. Polyhydric alcohols obtained by mixed aldol addition of formaldehyde with iso- or n-butyraldehyde are of particular interest here. In the aldol addition between formaldehyde and the corresponding butyraldehyde, an aldehyde intermediate is initially formed, which then has to be reduced to the polyhydric alcohol. Technically important polyhydric alcohols that can be obtained by this process are neopentyl glycol [NPG, 2,2-dimethylpropanediol- (1,3)] from the mixed aldolization of formaldehyde and isobutyraldehyde ( Chemiker-Zeitung, 100th year (1976) No. 12, pages 504-514; Ullmann's Encyclopedia of Industrial Chemistry, 6th edition, 2003, Wiley VCH Verlag GmbH & Co. KGaA, Weinheim, Volume 2, pages 50-52 ) or trimethylolpropane (TMP, 2-hydroxymethyl-2-methylpropanediol- (1,3)] from the mixed aldolization of formaldehyde and n-butyraldehyde ( Ullmann's Encyclopedia of Industrial Chemistry, 6th edition, 2003, Wiley VCH Verlag GmbH & Co. KGaA, Weinheim, Volume 2, pages 58-59 ).

It is known that in the aldol addition one aldehyde reacts as a carbonyl component and the other aldehyde as a methylene component to form a carbon-carbon bond. In order for the carbon-carbon bond to form, at least one aldehyde must have at least one hydrogen atom in the α-position to the carbonyl group. This aldehyde then reacts as a methylene component. The aldol addition is catalyzed by both basic and acidic compounds.

In base catalysis, an anion | C (R) ₂ -C (H) = O is initially formed from the aldehyde with the hydrogen atom in the α position, ie from the methylene component, according to reaction step (1), which is then combined with the carbonyl component R'- C (H) = O reacted to the addition product, releasing the basic catalyst B | ^- + HC (R) ₂ -C (H) = 0 → BH = | C (R) ₂ -C (H) = 0 (1)

The aldol addition is an equilibrium reaction and the position of the equilibrium depends on the base strengths of the reactants. So that the 3-hydroxyalkanal can be formed according to step (2), the base strength of the alcoholate anion R'-C (H) (O ^- ) -C (R) ₂ -C (H) = O must be greater than the base strength of the catalyst B1 ^- .

Uniform aldol addition products are formed when two structurally different aldehydes are reacted if one aldehyde component only carries an α-hydrogen atom and the other aldehyde component does not carry an α-hydrogen atom. This combination of starting compounds clearly defines which aldehyde reacts as the carbonyl component and which aldehyde reacts as the methylene component. An economically important process for this combination of the starting aldehydes is the conversion of formaldehyde with isobutyraldehyde to hydroxypivalaldehyde (2,2-dimethyl-3-hydroxypropanal). If n-butyraldehyde with two hydrogen atoms in the α position is reacted with formaldehyde to form the carbonyl group, formaldehyde is usually used in a molar excess per hydrogen atom in the α position in order to push the reaction in the direction of 2,2-dimethylolbutanal and the self-addition of n-butyraldehyde in to press the background.

It is known to carry out the aldol addition of two aldehydes in the presence of alkali or alkaline earth metal hydroxides as basic catalysts ( DE 1 518 784 A1 , U.S. 2,400,724 ). An aqueous catalyst solution is usually used and the organic phase is brought into intimate contact with the aqueous catalyst phase. After the reaction has ended, the organic phase and the aqueous catalyst phase are separated from one another and the organic phase is processed further. However, this method is disadvantageous the high amount of salt and the contamination of the aldol addition product obtained with alkali or alkaline earth metal ions, which prove to be disruptive to the metal catalyst in the subsequent catalytic hydrogenation of the aldol addition product to the polyol ( DE 1 768 274 A1 , DE 1 957 591 A1 ).

In the meantime, the use of tertiary amines as a catalyst for the aldol addition reaction has established itself in industry ( DE 1 957 591 A1 , U.S. 4,855,515 , EP 0 522 368 A1 ). Lower trialkylamines such as trimethylamine or triethylamine are often used as tertiary amines ( WO 2010/079187 A1 , EP 1 752 439 A1 ) or tri-n-propylamine ( DE 3 644 675A1 ). In contrast to the use of aqueous alkaline solutions, the amine-catalyzed aldol addition reaction takes place in a homogeneous organic medium. Accordingly, a high distillation effort has to be carried out to separate and recycle the amine catalyst. In the subsequent hydrogenation to polyols, the tertiary alkylamines also tend to form nitrogen-containing decomposition products, the presence of which, even in small traces, has a massive adverse effect on the quality of the polyol for many subsequent applications. When working up the polyol, almost complete removal of nitrogen-containing impurities must therefore be ensured.

In order to facilitate the separation of the basic catalyst from the organic reaction product, the use of solid, basic catalysts is also recommended. Such catalysts are, for example, macroporous ion exchange resins that carry basic tertiary amino groups ( DE 1 957 591 A1 ). Both weakly and strongly basic ion exchange resins are described, which are preferably based on a styrene-divinylbenzene polymer matrix with tertiary amino groups as functional groups ( EP 0 948 476 B1 , U.S. 2,818,443 ). Weakly basic ion exchange resins are preferably used ( WO 98/29374 A1 ). However, ion exchange resins are not always convincing with regard to the aldehyde conversion and their use is generally restricted by their poor stability.

The use of inorganic, basic solids is also described. According to WO 92/19579 A1 a mixture of tertiary amines and metal oxides of the elements IB, IVA, IVB, VA, VB, VIB and VIII of the Periodic Table of the Elements, in particular titanium and chromium, is used as the catalyst. Although the organic reaction product can easily be filtered off from the oxidic solid, complex work-up measures are necessary in order to separate off the nitrogen-containing compounds to a sufficient extent. To WO 00/00456 A1 Basically modified phyllosilicates can be used, which show advantageous conversions and selectivities. However, very long response times are required. EP 1 205 463 A1 deals with the catalytic production of aldols in a microstructured reaction system, whereby a heterogeneous catalyst is introduced into the microstructured system. Basic ion exchange resins, basic zeolites or metal oxides of Mo, W, Ca, Mg or Al can be used as the heterogeneous catalyst.

U. Rymsa, In-situ infrared spectroscopic investigations of the aldol condensation of n-butanal on basic solid-state catalysts, dissertation, University of Stuttgart, 2001 examines the aldol condensation of n-butanal in the gas phase on zeolitic and oxidic solid-state catalysts as well as on silicon dioxide impregnated with alkali metal acetates. In Applied Catalysis A: General 181 (1999), pages 331-346 describes the gradual substitution of oxygen by nitrogen in zirconium phosphate to zirconium phosphate oxide nitrides. The acid / base properties of these solids can be adjusted through the ratio of nitrogen to oxygen.

Because of the great importance that 3-hydroxyalkanals have as intermediates for the production of polyols, further improvements in relation to alternative processes and alternative catalysts for the production of 3-hydroxyalkanals are constantly being sought. The aldol addition should lead to the desired 3-hydroxyalkanal with high aldehyde conversion with high selectivity. The aldolization catalyst used should also have high stability in the reaction medium in order to ensure a sufficiently long catalyst service life.

The present invention therefore consists in a process for the preparation of 3-hydroxyalkanals by reacting an aldehyde of the general formula (I) R ¹ R ² HCC = (O) H with a further aldehyde of the general formula (II) R ³ -C = ( O) H to an addition product of the general formula (III) [R ³ -C (OH) H] _x -C [R ¹ ] _a [R ² ] _b -C = (O) H, in which R ¹ , R ² and R ^{3 are} each independently hydrogen or an aliphatic hydrocarbon radical of 1 to 8 carbon atoms, x is an integer from 1 to 3, a is 0 or 1 and b is 0 or 1 and x + a + b is 3, thereby characterized in that the reaction in solution at a temperature of 40 to 170 ° C in the presence of binary metal nitrides of the formula A ^{(m +)} _o N ^(3-) _p , in which o can assume the integer values 1 to 3, p regardless of this the integer values 1 to 4 can assume, m is an integer from 1 to 4 and the condition (m +) · o equal to (3-) · p is fulfilled, or takes place in the presence of Si ₃ N ₄ .

From J. Mol. Catal. A: Chem., 2006, 247, pp. 116-123 the reaction of cyclopentanone with valeraldehyde over AIPON and ZrPON catalysts to form the aldol condensation product is known, but it has surprisingly been found that binary metal nitrides are also suitable as solid catalysts in the aldol addition of two aldehydes. When solid metal nitrides are used, the aldolization catalyst can advantageously be separated off from the reaction mixture by filtration in a simple manner after the reaction has ended. When the reaction is carried out on solid catalysts, the residence time of the educts on the catalyst surface can also be set very specifically compared to a process procedure in which the aldolization catalyst is homogeneously dissolved in the reaction mixture or is dissolved in a separate aqueous phase that is intensively mixed with the organic educt phase.

The metal nitrides used according to the invention are binary metal nitrides of the general formula A ^{(m +)} _o N ^(3-) _p , in which o can assume the integer values from 1 to 3 and regardless of this p can assume the integer values from 1 to 4, m is an integer from 1 to 4 and the condition (m +) · o equal to (3-) · p is fulfilled.

Suitable metal nitrides are, for example, AlN, TiN, ZrN, HfN, VN, NbN, TaN, FeN, Fe ₂ N ₂ and CrN, either as individual substances or as mixtures. Mixtures of metal nitrides with other solids, such as carbides, transition metal oxides, silicon dioxide, aluminum oxide, boron oxide or activated carbon can also be used in the process according to the invention. Si ₃ N ₄ can also be used.

The binary metal nitrides used according to the invention are produced by processes known per se, for example by nitriding metal oxides under nitrogen or ammonia in the simultaneous presence of carbon or by reacting metal chlorides or organometallic compounds with nitrogen / hydrogen mixtures or with ammonia ( Ullmann's Encyclopedia of Industrial Chemistry, 6th edition, 2003, Wiley VCH Verlag GmbH & Co. KGaA, Weinheim, Volume 23, Pages 51-64 ). Both ionic nitrides, such as AlN, covalent nitrides, or transition metal nitrides of the formula AN, which are to be understood as intercalation compounds, for example TiN, TaN, FeN or CrN, are suitable as metal nitrides for the process according to the invention. AlN, TiN, TaN, FeN or CrN are particularly suitable for the method according to the invention. Si ₃ N ₄ is also suitable.

The solid aldolization catalyst is used in an amount of 1 to 10% by weight, preferably 3 to 8% by weight, based on the total reaction mixture.

The practical implementation of the aldol addition takes place in suspension in a stirred kettle or in a stirred kettle cascade, sufficient distribution of the solid in the reaction solution being ensured by vigorous stirring. The aldol addition can also be carried out in a tubular reactor on a fixed catalyst bed, for example also in a microstructured reaction system in which the reaction chamber is lined with the solid catalyst. Conducting the process with fixed catalysts makes it possible, in a simple manner, to recycle a partial stream from the reaction mixture removed as a recycle stream into the reactor. Otherwise, when using catalysts suspended in the reaction mixture, the catalyst is filtered off after the reaction has ended. The aldol addition can be carried out either continuously or batchwise.

The aldol addition is carried out at temperatures in the range from 40 to 170 ° C. under autogenous pressure or with application of an external gas pressure, preferably an inert gas pressure such as nitrogen pressure or noble gas pressure, at over autogenous pressure up to 5 MPa, preferably up to 3 MPa.

In the aldehydes of the general formula (I) R ¹ R ² HCC = (O) H, R ¹ and R ^{2 are} each, independently of one another, hydrogen or an aliphatic hydrocarbon radical of 1 to 8 carbon atoms, preferably 1 to 4 carbon atoms. R ¹ and R ² are particularly preferably each hydrogen, methyl, ethyl, n-propyl and iso-propyl.

Particularly suitable are acetaldehyde where R ¹ is R ² is hydrogen, propionaldehyde where R ¹ is methyl and R ² is hydrogen, n-butyraldehyde where R ¹ is ethyl and R ² is hydrogen, isobutyraldehyde where R ¹ is R ² is methyl , n-pentanal where R ¹ is n-propyl and R ² is hydrogen, 2-methylbutanal where R ¹ is ethyl and R ² is methyl and 3-methylbutanal where R ¹ is isopropyl and R ² is hydrogen.

In the aldehydes of the general formula (II) R ³ -C = (O) H, R ^{3 is} hydrogen or an aliphatic hydrocarbon radical of 1 to 8 carbon atoms, preferably 1 to 4 carbon atoms. R ³ particularly preferably represents hydrogen, methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl and 2-butyl.

R ³ particularly preferably represents hydrogen, so that the aldehyde of the general formula (I) is reacted with formaldehyde. In particular, the reaction with acetaldehyde gives 1,1,1-trimethylolethanal, with propionaldehyde 2,2-dimethylolpropanal, with n-butyraldehyde 2,2-dimethylbutanal and with isobutyraldehyde 2,2-dimethyl-3-hydroxypropanal. Formaldehyde can be used in solid form, as paraformaldehyde, or in solution. It is expedient to use commercially available aqueous formaldehyde solutions with a concentration of 30 to 50% by weight. When using an aqueous formaldehyde solution, a two-phase mixture is obtained which additionally contains the solid aldolization catalyst. After the reaction has taken place, the organic phase containing the 3-hydroxyalkanal is separated from the water and the metal nitride.

If the aldehydes of the general formula (I) and (II) represent structurally identical aldehydes, the self-condensation product is formed in the aldol addition. For example, the self-addition of n-butyraldehyde forms 2-ethyl-3-hydroxyhexanal and the self-addition of isobutyraldehyde forms 2,4-dimethyl-3-hydroxypentanal.

If the carbon atom α to the carbonyl carbon atom also carries a hydrogen atom, the 3-hydroxyalkanal can convert into an α, β-unsaturated alkenal with elimination of water. These α, β-unsaturated alkenals can be converted either by complete hydrogenation into the corresponding alcohols or by selective hydrogenation into the saturated aldehydes, from which carboxylic acids are accessible, for example, by subsequent oxidation. Both the complete hydrogenation to alcohols and the selective hydrogenation with subsequent oxidation are known from the prior art ( Ullmann's Encyclopedia of Industrial Chemistry, 6th edition, 2003, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, Volume 2, pages 24-25; Volume 6, pages 497-502 ). This further conversion of the aldol addition product to the aldol condensation product occurs when R ¹ and / or R ² are hydrogen in the aldehyde of the general formula (I). The self-addition with subsequent condensation of n-butyraldehyde, in which both the aldehyde of the general formula (I) and the aldehyde of the general formula (II) are n-butyraldehyde, is economically important. First of all, 2-ethyl-3-hydroxyhexanal is formed, which converts to 2-ethylhexenal with elimination of water. If the aldehyde of the general formula (I) is the same as the general formula (II) is n-pentanal, 2-propyl-3-hydroxyheptanal is initially formed, which is converted into 2-propylheptenal with elimination of water.

The 3-hydroxyalkanals obtained are important intermediates for the production of polyols, for example 1,3 diols. The hydrogenation of 3-hydroxyalkanals, for example of 2,2-dimethyl-3-hydroxypropanal to neopentyl glycol, is known per se and is implemented industrially in the form of gas-phase or liquid-phase hydrogenation on metal contact.

In the gas phase variant, the 3-hydroxyalkanal, for example 2,2-dimethyl-3-hydroxypropanal, is first freed of high boilers in an evaporator upstream of the hydrogenation stage. The subsequent hydrogenation is preferably carried out in the presence of Raney nickel catalysts or supported catalysts based on nickel, which can also contain other active metals such as copper or chromium and also activators. The gas phase variant is, for example, in EP 0 278 106 A1 ; U.S. 4,094,014 ; Ullmann's Encyclopedia of Industrial Chemistry, 6th Edition, 2003, Wiley VCH Verlag GmbH & Co. KGaA, Weinheim, Volume 2, pages 50-52; Chemiker-Zeitung, 100th year (1976), No. 12, pages 504-514 received.

The hydrogenation in the liquid phase is described many times, for example in EP 0 484 800 A2 using catalysts based on copper, zinc and zirconium. The liquid-phase hydrogenation of 2,2-dimethyl-3-hydroxypropanal often takes place in the presence of copper chromite catalysts. Copper chromite catalysts often contain other metals as activators, for example barium, cadmium, magnesium, manganese and / or a rare earth metal. According to U.S. 4,855,515 Manganese-doped copper chromite catalysts are particularly notable for the hydrogenation of the aldolization product from the reaction of formaldehyde with isobutyraldehyde. WO98 / 29374 A1 discloses the use of a barium-doped copper chromite catalyst for the hydrogenation of 2,2-dimethyl-3-hydroxypropanal in a methanolic solution. Also EP 0 522 368 A1 recommends the use of copper chromite catalysts for liquid phase hydrogenation in the presence of a lower alcohol and water.

Further copper-containing hydrogenation catalysts are, for example, in WO 95/32171 or WO 98/29374 described.

3-Hydroxyalkanals can also be reduced to the polyols in the presence of stoichiometric amounts of a base and formaldehyde after the Cannizzaro reaction. This process variant is also known per se and is operated technically ( WO 01/51438 A1 , EP 2 341 041 A1 , U.S. 5,948,943 ). Aqueous solutions of alkali or alkaline earth metal hydroxides, for example aqueous solutions of sodium hydroxide, potassium hydroxide or calcium hydroxide, are expediently used as the base. By reducing the aldehyde function, formaldehyde is oxidized to formic acid and the corresponding formates, such as sodium formate, potassium formate or calcium formate, are obtained as by-products.

Examples:

The investigation of the catalytic activity of various metal nitrides in the aldol addition of isobutyraldehyde with formaldehyde was carried out in a 50 ml digestion autoclave. To this end, 9 ml of an aqueous formaldehyde solution (37% by weight) and 12 ml of isobutyraldehyde, corresponding to a 10 mol% excess of isobutyraldehyde, based on formaldehyde, with 5% by weight of metal nitride were obtained to the reaction mixture, corresponding to 0.96 grams. The reaction was carried out over a period of 1.5 hours under an argon atmosphere at 150.degree. C. and the pressure which had set in, with intensive stirring.

The batch was then cooled to room temperature, relaxed and expanded. The results of the gas chromatographic analysis (% by weight) of the reaction mixture are compiled in Table 1 below. Table 1: Gas chromatographic analysis of the aldol addition product of isobutyraldehyde with formaldehyde in the presence of metal nitride catalysts attempt Metal nitride Iso-butyraldehyde conversion [%] Selectivity to 2,2-dimethyl-3-hydroxypropanal [%] Yield to 2,2-dimethyl-3-hydroxypropanal [%] 1 AlN 81.8 53.9 44.1 2 TlN 42.5 50.4 21.4 3 * TiN / TiC 52.7 45.4 23.9 4th TaN 13.1 60.6 8.0 5 ** Si ₃ N ₄ (M9) 22.9 65.8 15.1 6 *** Si ₃ N ₄ (M11) 35.8 57.9 20.7 * TiC / TiN in a mass ratio of 1: 1 ** M9: 95.70% by weight α-Si ₃ N ₄ , C 1779 ppm, O 1.12%, Al 375 ppm, Ca 38 ppm, Fe 30 ppm; Remainder to 100% by weight of further, X-ray amorphous Si / N compounds *** M11: 90.8% by weight of α-Si ₃ N ₄ , C 0.2%, O 1.5%, Al 0.01%, Fe 0.002%; Remainder to 100% by weight of further, X-ray amorphous Si / N compounds

Claims (11)

Process for the preparation of 3-hydroxyalkanals by reacting an aldehyde of the general formula (I) R ¹ R ² HCC = (O) H with another aldehyde of the general formula (II) R ³ -C = (O) H to form an addition product of general formula (III) [R ³ -C (OH) H] _x -C [R ¹ ] _a [R ² ] _b -C = (O) H, in which R ¹ , R ² and R ^{3 are} each independently hydrogen or an aliphatic hydrocarbon radical of 1 to 8 carbon atoms, x is an integer from 1 to 3, a is 0 or 1 and b is 0 or 1 and x + a + b is 3, characterized in that the reaction in solution at a temperature of 40 to 170 ° C in the presence of binary metal nitrides of the formula A ^{(m +)} _o N ^(3-) p, in which o can assume the integer values 1 to 3, p can assume the integer values 1 to 4 regardless of this can, m is an integer from 1 to 4 and the condition (m +) · o equal to (3-) · p is fulfilled, or takes place in the presence of Si ₃ N ₄ . Procedure according to Claim 1 , characterized in that A is aluminum, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium or iron. Procedure according to Claim 1 or 2 characterized in that the binary metal nitrides are selected from the group of AlN, TiN, TaN, CrN, FeN. Method according to one or more of Claims 1 to 3 , characterized in that the aldehyde of the general formula (I) represents acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, n-pentanal, 2-methylbutanal or 3-methylbutanal. Method according to one or more of Claims 1 to 4th , characterized in that in the general formula (II) R ^{3 represents} hydrogen, methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl or 2-butyl. Method according to one or more of Claims 1 to 5 , characterized in that the reaction is carried out under autogenous pressure or with application of an external gas pressure at over autogenous pressure up to 5 MPa. Procedure according to Claim 6 , characterized in that the reaction is carried out with the application of an external gas pressure at over autogenous pressure up to 3 MPa. Method according to one or more of Claims 1 to 7th , characterized in that the reaction takes place in the presence of suspended or fixed binary metal nitrides or Si ₃ N ₄ . Method according to one or more of Claims 1 to 8th , characterized in that the reaction takes place in a tubular reactor. Method according to one or more of Claims 1 to 9 , characterized in that the aldehyde of the general formula (I) stands for acetaldehyde, propionaldehyde, n-butyraldehyde or isobutyraldehyde and the aldehyde of the general formula (II) stands for formaldehyde. Method according to one or more of Claims 1 to 9 characterized in that the reaction for aldehydes of the general formula (I) with R ¹ and / or R ² equal to hydrogen is continued with elimination of water to form the aldol condensation product.