KR20140044871A - Method for producing formamides and formic acid esters - Google Patents

Abstract

The present invention provides a reaction mixture comprising carbon dioxide, hydrogen, and an alcohol of formula (Ib) or an amine of formula (Ic) below at a pressure ranging from 0.2 to 30 MPa and a temperature ranging from 20 to 200 ° C. in the presence of a catalyst comprising gold in a hydrogenation reactor. By reacting (Rm) a carboxylic acid derivative of formula (Ia): H- (C = 0) -R (Ia), wherein R is OR ¹ and NR ² R ³ Wherein R ¹ is unsubstituted or at least monosubstituted C ₁ -C ₁₅ alkyl, C ₅ -C ₁₀ cycloalkyl, C ₅ -C ₁₀ heterocyclyl, C ₅ -C ₁₀ aryl or C _5- C ₁₀ heteroaryl, wherein the substituent is selected from the group consisting of C ₁ -C ₁₅ alkyl, C ₁ -C ₆ alkoxy, C ₅ -C ₁₀ cycloalkyl and C ₅ -C ₁₀ aryl; R ² and R ³ They are each, independently of one another, hydrogen, unsubstituted or at least monosubstituted C ₁ -C ₁₅ alkyl, C ₅ -C ₁₀ cycloalkyl Kiel, a C ₅ -C ₁₀ heterocyclyl, C ₅ -C ₁₀ aryl or C ₅ -C ₁₀ heteroaryl, where the substituents are C ₁ -C ₁₅ alkyl, C ₅ -C ₁₀ cycloalkyl and C ₅ -C Or is selected from the group consisting of ₁₀ aryl, or R ² and R ³ , together with the nitrogen atom, optionally further comprise one or more heteroatoms selected from O, S and N and have 5- or 6-membered substituents R ⁴ ; A ring, wherein R ⁴ is hydrogen or C ₁ -C ₆ alkyl; R ¹ -OH (Ib), wherein R ¹ has the above meaning; NHR ² R ³ (Ic), wherein R ² and R ³ each independently have the above meaning.

Description

Method for preparing formamide and formic acid ester {METHOD FOR PRODUCING FORMAMIDES AND FORMIC ACID ESTERS}

The present invention relates to a process for producing formamide and formic acid esters, ie formamide and its N -substituted derivatives and also esters of formic acid and alcohols, starting from carbon dioxide and hydrogen.

Formamide and its N-substituted derivatives are important selective solvents and extractants because of their polarity. It is used, for example, for the extraction of butadiene from the C ₄ fraction of acetylene and from aliphatic from the C ₂ cracking fraction.

Formic acid esters such as methyl formate or ethyl formate are used as blowing agents or perfumes.

All industrial production methods for producing formamide and its alkyl derivatives, and also formic acid esters, have so far used carbon monoxide as the C ₁ building block.

Formamide, N -alkylformamide and N , N -dialkylformamide react methyl amate, ammonia, N -alkylamine and N , N -dialkylamine with methyl formate, which can be obtained by the reaction of carbon monoxide and methanol, respectively. Are prepared. Methanol liberated here can be recycled to the synthesis of methyl formate from carbon monoxide and methanol. Other formic acid esters are obtained with the removal of water by reaction of the formic acid with the corresponding alcohol.

In other syntheses used in industry likewise, ammonia or the amine reacts directly with carbon monoxide instead of methyl formate at 20-100 ° C. and 2-10 MPa. The reaction is carried out in methanol as solvent using alkoxide as catalyst (Hans-Juergen Arpe, Industrielle Organische Chemie, 6th edition, 2007, pages 48 to 49).

Carbon monoxide is a relatively expensive C ₁ building block. A further disadvantage of carbon monoxide is its toxicity, which requires that you work in strict safety precautions. In addition, a relatively high pressure in the production of formamide from carbon monoxide is expensive.

Therefore, low carbon monoxide, and a non-toxic there are several attempts to replace a C ₁ building blocks of carbon dioxide is available in large quantities (see, e.g., [Applied Homogeneous Catalysis with Organometallic Compounds, volume 2, pages 1058 to 1072, 1996, VCH Verlagsgesellschaft and W. Leitner, Angew. Chem. Int. Ed. Engl. 1995, 34, pages 2207 to 2221]. However, most of these studies used homogeneously dissolved catalysts that were difficult to separate from the product and recycle to hydrogenation.

Attempts have been made to immobilize the homogeneous catalyst on the support material to allow for easier separation. Such a process is described in [Y. Kayaki, Y. Shimokawatoko, T. Ikariya, Adv. Synth. Catal. 2003 , 345, 175-179, for dimethylformamide. However, this concept requires certain support materials, such as diphosphine-modified polystyrene or silica gel, that are complex to prepare. Another disadvantage is that the catalytic activity is significantly reduced at each recycle step. This may be due in particular to the homogeneous catalyst which remains completely unfixed. The production of economically attractive formamides is not described in this study.

The use of heterogeneous hydrogenation catalysts may allow for simple separation and reuse of the catalyst. US 4 269 998 describes the use of combinations of copper chromite catalysts with Group VIII compounds for the production of dialkylformamides. The disadvantage is that only dialkylformamide can be obtained with this process. The preparation of formamide or formic acid esters is not described. In addition, the group VIII compounds are sensitive to carbon monoxide. However, carbon monoxide is often present as an impurity in the hydrogen or carbon dioxide used. Therefore, high purity hydrogen and high purity carbon dioxide should be used in this process.

J. Liu, G. Guo, Z. Zhang, T. Jiang, H. Liu, J. Song, H. Fan, B. Han, Chem. Commun. 2010 , 46 , 5770-5772 describe copper oxide / zinc oxide catalysts, without Group VIII compounds, for preparing dimethylformamide. A disadvantage of this process is that only dimethylformamide can likewise be obtained. The preparation of formamide or formic acid esters is not described.

It is an object of the present invention to provide a process for preparing carboxylic acid derivatives, in particular formamide and N-substituted formamide derivatives and formic acid esters, based on the starting materials carbon dioxide, hydrogen and amines or alcohols. This method should preferably be operable continuously. The preparation of carboxylic acid derivatives, in particular formamide and N-substituted formamide derivatives and formic acid esters, should preferably be carried out in one reaction step (integration process). The target product, namely formamide, N-substituted formamide derivatives and formic acid esters should be obtainable with high yields and selectivity. Post-treatment of the reaction output from the hydrogenation reactor and removal of the catalyst are technically simple, require less energy, and preferably should be carried out exclusively using materials present in all cases of the process without additional auxiliaries.

This object is achieved by a reaction comprising carbon dioxide, hydrogen, and an alcohol of the formula (Ib) or an amine of the formula (Ic) By reacting the mixture (Rm), it is achieved by a process for preparing carboxylic acid derivatives of the general formula (la).

<Formula Ia>

H- (C = O) -R

(Wherein,

R is selected from the group consisting of OR ¹ and NR ² R ³ , wherein

R ¹ is unsubstituted or at least monosubstituted C ₁ -C ₁₅ -alkyl, C ₅ -C ₁₀ -cycloalkyl, C ₅ -C ₁₀ -heterocyclyl, C ₅ -C ₁₀ -aryl or C ₅ -C ₁₀ Heteroaryl,

Wherein the substituent is selected from the group consisting of C ₁ -C ₁₅ -alkyl, C ₁ -C ₆ -alkoxy, C ₅ -C ₁₀ -cycloalkyl and C ₅ -C ₁₀ -aryl;

R ² and R ³ are each, independently of one another, hydrogen, unsubstituted or at least monosubstituted C ₁ -C ₁₅ -alkyl, C ₅ -C ₁₀ -cycloalkyl, C ₅ -C ₁₀ -heterocyclyl, C ₅ -C ₁₀ -aryl or C ₅ -C ₁₀ -heteroaryl,

Wherein the substituent is selected from the group consisting of C ₁ -C ₁₅ -alkyl, C ₅ -C ₁₀ -cycloalkyl and C ₅ -C ₁₀ -aryl, or

R ² and R ³ optionally together with a nitrogen atom, optionally further comprise one or more heteroatoms selected from O, S and N and have a substituent R ⁴ Forms a 5- or 6-membered ring, wherein

R ⁴ is hydrogen or C ₁ -C ₆ -alkyl

(Ib)

R ¹ -OH

Wherein R ¹ has the meaning

<Formula I>

NHR ² R ³

(Wherein R ² and R ³ each independently have the above meaning).

The method of the present invention allows the use of inexpensive carbon dioxide instead of the relatively expensive carbon monoxide as the C ₁ building block. In addition, the process of the present invention allows for simple removal of the catalyst, good product yield and simple work up of the product mixture.

In the process of the invention, the reaction mixture (Rm) comprising carbon dioxide, hydrogen, alcohol (Ib) or amine (Ic) is reacted. When the reaction mixture (Rm), including alcohol (Ia) is used, a formic ester (Ia1) according to Reaction Scheme II is formed as a carboxylic acid derivative (Ia), wherein R ¹ of The above definition applies similarly to formic acid ester (Ia1). In other words, 1 mol of formic acid ester (Ia1) and 1 mol of water of reaction are formed from 1 mol of carbon dioxide, 1 mol of hydrogen and 1 mol of alcohol (Ib).

When a reaction mixture (Rm) comprising an amine (Ia) is used, formamide compound (Ia2) is formed as carboxylic acid derivative (Ia) according to Scheme III, wherein the above definitions of R ² and R ³ form Similarly applies to amide compounds (Ia2). In other words, 1 mol of formamide compound (Ia2) and 1 mol of reaction water are formed from 1 mol of carbon dioxide, 1 mol of hydrogen and 1 mol of amine (Ic).

In a preferred embodiment,

R ¹ is unsubstituted or at least monosubstituted C ₁ -C ₈ -alkyl,

Wherein the substituent is selected from the group consisting of C ₁ -C ₆ -alkyl and C ₁ -C ₆ -alkoxy

Alcohol R ₁ -OH (Ib) is used for the preparation of formic acid ester (Ia1).

Here, the corresponding formic acid ester of the general formula (la) is obtained.

<Formula Ia1>

H (C = O) -OR ¹

Where

R ¹ is unsubstituted or at least monosubstituted C ₁ -C ₈ -alkyl,

Wherein the substituent is selected from the group consisting of C ₁ -C ₆ -alkyl and C ₁ -C ₆ -alkoxy.

For the purposes of the present invention, the term C ₁ -C ₁₅ -alkyl refers to branched, unbranched, saturated and unsaturated groups. Preference is given to saturated alkyl groups (C ₁ -C ₆ -alkyl) having 1 to 6 carbon atoms. More preferred are saturated alkyl groups (C ₁ -C ₄ -alkyl) having 1 to 4 carbon atoms.

Examples of saturated alkyl groups are methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, amyl and hexyl.

Examples of unsaturated alkyl groups (alkenyl, alkynyl) are vinyl, allyl, butenyl, ethynyl and propynyl.

C ₁ -C ₁₅ -alkyl group is unsubstituted or selected from the group consisting of C ₁ -C ₁₅ -alkyl, C ₁ -C ₆ -alkoxy, C ₅ -C ₁₀ -cycloalkyl, C ₅ -C ₁₀ -aryl It may be substituted with more than one substituent.

For the purposes of the present invention, the term C ₅ -C ₁₀ -cycloalkyl refers to saturated, unsaturated monocyclic and polycyclic groups. Examples of C ₅ -C ₁₀ -cycloalkyl are cyclopentyl, cyclohexyl and cycloheptyl. The cycloalkyl group can be unsubstituted or substituted with one or more substituents as defined above for the C ₁ -C ₁₅ -alkyl group.

For the purposes of the present invention, C ₅ -C ₁₀ -aryl is an aromatic ring system having 5 to 10 carbon atoms. Aromatic ring systems can be monocyclic or bicyclic. Examples of aryl groups are phenyl, naphthyl such as 1-naphthyl and 2-naphthyl. The aryl group may be unsubstituted or substituted with one or more substituents as defined above for the C ₁ -C ₁₅ -alkyl group.

For the purposes of the present invention, C ₅ -C ₁₀ -heteroaryl is a heteroaromatic system comprising one or more heteroatoms selected from the group consisting of N, O and S. Heteroaryl groups can be monocyclic or bicyclic. When nitrogen is a ring atom, the invention also includes N-oxides of nitrogen-containing heteroaryls. Examples of heteroaryl are thienyl, benzothienyl, 1-naphthothienyl, thianthrenyl, furyl, benzofuryl, pyrrolyl, imidazolyl, pyrazolyl, pyridyl, pyrazinyl, pyrimidinyl, pyrida Genyl, Indolyl, Isoindoleyl, Indazolyl, Purinyl, Isoquinolinyl, Quinolinyl, Acridinyl, Naphthyridinyl, Quinoxalinyl, Quinazolinyl, Cinolinyl, Piperidinyl, Carboly Nil, thiazolyl, oxazolyl, isothiazolyl, isoxazolyl. Heteroaryl groups may be unsubstituted or substituted with one or more substituents as defined above for C ₁ -C ₁₅ -alkyl groups.

For the purposes of the present invention, the term C ₅ -C ₁₀ -heterocyclyl refers to a 5- to 10-membered ring system comprising at least one heteroatom selected from the group consisting of N, O and S. The ring system can be monocyclic or bicyclic. Examples of suitable heterocyclic ring systems include piperidinyl, pyrrolidinyl, pyrrolinyl, pyrazolinyl, pyrazolidinyl, morpholinyl, thiomorpholinyl, pyranyl, thiopyranyl, piperazinyl, indole Linyl, dihydrofuranyl, tetrahydrofuranyl, dihydrothiophenyl, tetrahydrothiophenyl, dihydropyranyl and tetrahydropyranyl.

For the purposes of the present invention, the term C ₁ -C ₆ -alkoxy refers to C ₁ -C ₆ -alkyl-O-radicals. As examples of the alkyl portion of the alkoxy group, mention may be made of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, amyl and hexyl.

Methanol, ethanol, 2-methoxyethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 1-pentanol, 1-hexanol, 1-heptanol and 1 Particular preference is given to using alcohols selected from the group consisting of octanol as alcohol (lb). By doing so, methyl formate, ethyl formate, 2-methoxyethyl formate, 1-propyl formate, 2-propyl formate, 1-butyl formate, 2-butyl formate, 2-methyl-1-propyl Corresponding formic acid esters (Ia1) selected from the group consisting of formate, 1-pentyl formate, 1-hexyl formate, 1-heptyl formate, 1-octyl formate can be obtained.

In a further preferred embodiment, methanol is used as alcohol (Ib) and methyl formate is obtained as formic acid ester (Ia1).

For the purposes of the present invention, the term "formamide compound (Ia2)" includes both formamide (H- (C = 0) -NH ₂ ) itself and N-substituted formamide derivatives. In a preferred embodiment, ammonia, methylamine, dimethylamine, ethylamine, diethylamine, n-propylamine, di-n-propylamine, isopropylamine, diisopropylamine, n-butylamine, di-n- An amine selected from the group consisting of butylamine, isobutylamine, diisobutylamine, morpholine, piperidine and piperazine is used as amine (Ic) in the preparation of formamide compound (Ia2). By doing so, formamide, methylformamide, dimethylformamide, ethylformamide, diethylformamide, n-propylformamide, di-n-propylformamide, isopropylformamide, diisopropylformamide, n- Butylformamide, di-n-butylformamide, isobutylformamide, diisobutylformamide, N-formylmorpholine, N-formylpiperidine and N-formylpiperazine A formamide compound (Ia2) can be obtained.

In a further preferred embodiment, an amine selected from the group consisting of ammonia, methylamine and dimethylamine is used as the amine (Ic). In this way, a corresponding formamide compound (Ia2) selected from the group consisting of formamide, methylformamide, dimethylformamide can be obtained.

In a particularly preferred embodiment, ammonia is used as amine (Ic) and formamide is obtained as formamide compound (Ia2).

In a further particularly preferred embodiment, morpholine is used as amine (Ic) and formylmorpholine is obtained as formamide compound (Ia2).

As hydrogenation reactors, all reactors which are basically suitable for heterogeneously catalyzed gas / liquid reactions at given temperatures and given pressures can in principle be used. Standard reactors suitable for gas-liquid reaction systems are described, for example, in K.D. Henkel, "Reactor Types and Their Industrial Applications" and Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH Verlag GmbH & Co. KGaA, DOI: 10.1002 / 14356007.b04_087. Examples that may be mentioned are stirred tank reactors, tube reactors, shell-and-tube reactors and fixed bed reactors.

The amines (Ic) or alcohols (Ib) used in the process of the invention are fed into the hydrogenation reactor in liquid or gaseous form. The molar ratio of alcohol (Ib) or amine (Ic) used in the process of the invention relative to carbon dioxide is generally from 0.01 to 30, preferably from 0.2 to 5.

The carbon dioxide used for the reaction of carbon dioxide and hydrogen in the hydrogenation reactor may be used in solid, liquid or gaseous form. Industrially available gas mixtures comprising carbon dioxide can be used. Hydrogen and carbon dioxide may also include other inert gases such as nitrogen or rare gases. It has surprisingly been found that the gold catalyst used in the process of the present invention is tolerant to carbon monoxide which often causes poisoning of the hydrogenation catalyst. The hydrogen and carbon dioxide used for the reaction in the hydrogenation reactor may thus also include carbon monoxide as impurities. The carbon monoxide content in the gas stream fed to the hydrogenation reactor is advantageously less than 20 mol%, based on the total amount of carbon dioxide and hydrogen in the hydrogenation reactor. While higher amounts are optionally likewise still acceptable, this generally requires the use of higher pressures in the reactor, which leads to the need for greater compressive energy.

The hydrogenation of carbon dioxide is carried out in the liquid phase preferably at a temperature of 20 to 200 ° C. and a total pressure of 0.2 to 30 MPa abs, and the total pressure is preferably at least 1 MPa abs. Especially preferably, it is 5 Mpa abs or more, More preferably, it is 15 Mpa abs or less. The temperature is preferably at least 30 ° C, particularly preferably at least 100 ° C, further preferably at most 180 ° C, particularly preferably at most 170 ° C, very particularly preferably at most 160 ° C.

The partial pressure of carbon dioxide is generally at least 0.5 MPa, preferably at least 2 MPa and also generally at most 8 MPa. The partial pressure of hydrogen is 0.5 MPa or more, preferably 1 MPa or more, and generally 25 MPa or less, preferably 15 MPa or less.

The molar ratio of hydrogen to carbon dioxide in the feed to the hydrogenation reactor is preferably 0.1 to 10, particularly preferably 1 to 3.

The molar ratio of carbon dioxide to amine (Ic) or alcohol (Ib) in the feed to the hydrogenation reactor is generally from 0.01 to 30, preferably from 0.2 to 5.

The catalyst used in the process of the invention comprises a catalytically active metal component comprising gold. Preference is given to using heterogeneous catalysts. Gold is preferably present in metallic form, ie in oxidation state (0). The metal component of the catalyst may comprise not only gold but also one or more additional metals, for example precious metals selected from the group consisting of Pd, Pt, Ag and Cu in alloy form. The metal component may further comprise a metal promoter. As metal components gold is used in pure form, ie in each case a metal component comprising at least 50% by weight, preferably at least 70% by weight, in particular 90% by weight of gold, based on the total weight of the metal component It is preferable.

The metal component of the catalyst is preferably used in the form of nanoparticles. The average particle diameter (D ⁵⁰ ) is usually in the range of 0.1 to 50 nm.

The metal component of the catalyst can be used as it is. In this case the metal component itself forms the actual catalyst, ie the metal component of the catalyst is used in unsupported form.

Suitable heterogeneous catalysts are, for example, gold itself, ie in pure form, or gold on the support material (supported gold). In the case of gold itself, preference is given to using "gold black", ie colloidally deposited elemental gold.

It is also possible to use a catalyst (supported catalyst) comprising a metal component and a support material. In this case the metal component is fixed on the surface of the support material. Supported gold nanoparticles can likewise be used.

It is also possible to use gold alloys on the support, such as Au-M, where M is a noble metal such as Pd or Pt or else another metal such as Ag or Cu as catalyst. Several metal promoters may also be present in the same catalyst.

Preference is given to using supported gold catalysts in the process of the invention. As support it is possible to use a wide variety of materials, such as inorganic oxides, graphite, polymers or metals. For inorganic oxides, silicon dioxide, magnesium oxide, zirconium oxide and / or titanium oxide are preferred. Magnesium oxide, aluminum oxide, silicon oxide, gallium oxide, zirconium oxide, cerium oxide and / or titanium oxide are particularly preferred as support materials. It is also possible to use mixtures of various inorganic oxides. Heterogeneous catalysts can be used in a variety of geometric shapes and sizes, for example pellets, cylinders, hollow cylinders, spheres, rods or extrudates. The average particle diameter is typically in the range of 1 to 10 mm. In the case of metals or polymers as supports, meshes, woven mesh wires or knitted fabrics can also be used.

In the case of supported catalysts, heterogeneous catalysts generally contain from 0.01 to 50% by weight, preferably from 0.1 to 20% by weight, particularly preferably from 0.1 to 5% by weight, based on the total mass of the supported catalyst used. Include. For unsupported catalysts, the gold content is generally in the range of 0.01 to 100% by weight, based on the total amount of catalyst used.

Suitable gold catalysts are commercially available or can be obtained by known methods of treating the support material with a solution of the gold compound or by coprecipitation and subsequent drying, heat treatment and / or calcining.

Regardless of whether a gold-comprising catalyst is supported and whether additional metals are included (eg in the form of a gold alloy), gold catalysts are generally 0.1-50 nm in diameter as measured by X-ray diffraction. It includes gold particles having a. In addition, particles having a diameter of less than 0.1 nm, or alternatively more than 50 nm, may also be present.

In addition, regardless of whether a gold-comprising catalyst is supported and whether additional metals are included (eg in the form of a gold alloy), the heterogeneous catalyst may range from 1 m ² / g to 1000 m ² / g. Have a BET surface area (measure BET surface area according to DIN ISO 9277). The BET surface area of the heterogeneous catalyst is preferably in the range of 10 m ² / g to 500 m ² / g.

The volume of heterogeneous catalyst in the hydrogenation reactor generally ranges from 0.1 to 95% of the reaction volume of the hydrogenation reactor, where the catalyst volume is obtained by dividing the catalyst mass by the bulk density of the catalyst.

In the process of the invention, the reaction mixture (Rm) may additionally comprise a polar solvent. This is particularly advantageous when the amine (Ic) reacts with carbon dioxide and hydrogen to form formamide compound (Ia2) according to Scheme III. Amines (Ic), for example ammonia, may form salts with carbon dioxide. The use of polar solvents can improve the solubility of these salts in the reaction mixture (Rm).

In the process of the invention, the reaction mixture (Rm) may comprise a polar solvent or a mixture of two or more polar solvents. Preference is given to alcohols and diols and their formic acid esters, formamides such as formamide, methylformamide or dimethylformamide or water as materials which are suitable as polar solvents.

Suitable alcohols are, for example, methanol, ethanol, 2-methoxyethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol and 2-methyl-1-propanol.

Preference is given to diols and formic acid esters thereof, polyols and formic acid esters thereof, sulfones, sulfoxides, open chain or cyclic amides and mixtures of the mentioned series as materials which are suitable as polar solvents.

Suitable diols and polyols are, for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, dipropylene glycol , 1,5-pentanediol, 1,6-hexanediol and glycerol.

Suitable sulfones are tetramethylene sulfones (sulfolanes).

Suitable sulfoxides are, for example, dialkyl sulfoxides, preferably C ₁ -C ₆ -dialkyl sulfoxides, in particular dimethyl sulfoxide.

Suitable open chain or cyclic amides are for example formamide, methylformamide, dimethylformamide, N -methylpyrrolidone, acetamide and N -methylcaprolactam.

The molar ratio of the polar solvent or solvent mixture used in the process of the invention to the amine (Ic) used is generally in the range from 0.5 to 30, preferably from 1 to 20.

The hydrogenation of carbon dioxide in the process of the invention can be carried out batchwise or continuously. In a batch process, the reactor is charged with the desired liquid and optionally solid starting materials and auxiliaries and subsequently pressurized with carbon dioxide and hydrogen to the desired pressure and the desired temperature. After completion of the reaction, the reactor is generally depressurized and the liquid reaction mixture is separated from the heterogeneous catalyst.

In a continuous process, starting materials and auxiliaries, including carbon dioxide and hydrogen, are continuously fed to the hydrogenation reactor. The catalyst can be used as a fixed bed (fixed bed reactor). In the case of a fixed bed reactor, the heterogeneous catalyst is fixed in place within the hydrogenation reactor.

It is also possible to suspend the catalyst in the reaction mixture (Rm). In the case of suspended heterogeneous catalysts, they may be present in the hydrogenation reactor before the start of the reaction. In a continuous process, however, the heterogeneous catalyst is preferably fed into the hydrogenation reactor at the same rate as it is continuously withdrawn from the reactor.

In a continuous process, the liquid phase is discharged continuously from the hydrogenation reactor so that the liquid level in the reactor remains on average the same. Continuous hydrogenation of carbon dioxide is preferred.

The average residence time of the reaction mixture (Rm) in the hydrogenation reactor is generally from 10 minutes to 5 hours.

Regardless of the type of heterogeneous catalyst and whether the hydrogenation is continuous or batchwise, the carboxylic acid derivative (Ia), the water of reaction and possibly unreacted alcohol (Ib) or unreacted amine (Ic) A hydrogenation mixture (H) comprising is obtained in the reaction of the reaction mixture (Rm) in a hydrogenation reactor. The hydrogenation mixture (H) may additionally comprise a polar solvent or a polar solvent mixture. If a suspended heterogeneous catalyst is used, it is likewise included in the hydrogenation mixture (H).

In the case of fixed bed catalysts, the catalyst is held in place and thus maintained in the hydrogenation reactor, and the hydrogenation mixture does not contain any catalyst, ie contains less than 5 ppm gold catalyst based on the total weight of the reaction mixture (Rm). In the case of suspended heterogeneous catalysts which are not fixed in place, they are usually held in the hydrogenation reactor by means known in the reactor outlet, for example by a mesh or a filter. However, the catalyst can also be separated from the hydrogenation mixture (H) by means of a simple mesh, such as filtration, decant or centrifugation, in a downstream step after the reaction and recycled to the hydrogenation reactor. After the catalyst has been separated off, the hydrogenation mixture (H) is virtually free of gold (after-treated hydrogenation mixture (Hw)), ie, the gold content of the post-treated hydrogenation mixture (Hw) gives It is less than 5 ppm by weight.

After the catalyst is separated off, the post-treated hydrogenation mixture (Hw) is worked up by distillation to include the first stream comprising the carboxylic acid derivative (Ia), unreacted alcohol (Ib) or unreacted amine (Ic). To obtain a third stream comprising a second stream and water of reaction.

If the reaction is carried out in the presence of a polar solvent, the polar solvent can be separated off via the fourth stream. However, it is also possible to remove the polar solvent together with the unreacted alcohol (Ib) or unreacted amine (Ic) (second stream). In addition, it is also possible to separate the polar solvent together with the water (third stream) of the reaction.

Post-treatment by distillation may be carried out in one or two or more stages, depending on the separation problem.

In the preparation of formamide compound (Ia2) in the presence of a polar solvent, distillation for separating off low-boiling polar solvents such as monohydric alcohol methanol, ethanol, propanol and butanol can be carried out at atmospheric pressure or under reduced pressure. In a preferred embodiment, the polar solvent is recycled to the hydrogenation reactor.

Even when low-boiling carboxylic acid derivatives (Ia) such as methyl formate, ethyl formate or propyl formate are prepared, they are preferably water of reaction and at atmospheric or slight superatmospheric pressure (below a gauge pressure of 0.2 MPa) and Comes off from unreacted alcohol (lb). Unreacted alcohol R ¹ -OH, in a preferred embodiment, is recycled to the hydrogenation reactor and the water of the reaction is discarded.

On the other hand, when diol is used as the polar solvent and a relatively high boiling carboxylic acid derivative (Ia) such as formamide is obtained, the post-treatment by distillation is preferably under reduced pressure, more preferably in the range from 0.1 to 500 mbar abs. Is performed. Unreacted amine (Ic), in a preferred embodiment, is separated off during distillation and recycled to the hydrogenation reactor. Likewise, any polar solvent used is recycled to the hydrogenation reactor after distillation, in a preferred embodiment. The water of the separated reaction is discarded.

Depending on the separation problem, various arrangements are possible as distillation units for workup by distillation of the workup hydrogenation mixture (Hw). If the boiling points of the materials used, ie the carboxylic acid derivatives (Ia), unreacted alcohols (Ib) or unreacted amines (Ic) and any polar solvents differ significantly, for example using an evaporator such as a falling film evaporator It is possible to do However, distillation units used generally comprise distillation columns comprising random packing elements, regular packings and / or trays.

If additional polar solvents are used, the distillation unit comprises at least one distillation column, preferably two or three distillation columns. Such columns include, for example, random packing elements, regular packings and / or trays, depending on the separation problem.

The carboxylic acid derivative (Ia) (target product) is released from the process and, if necessary, sent to fine purification, preferably by distillation.

The invention is illustrated with the aid of the following figures, without being limited thereto.

1 shows a block diagram of a plant for a preferred embodiment of the process of the invention for preparing formamide compound (Ia2) from carbon dioxide, hydrogen and amine (Ic).
2 shows a block diagram of a plant for a preferred embodiment of the process of the invention for producing formic acid ester (Ia1) from carbon dioxide, hydrogen and alcohol (lb).
3 shows a block diagram of a plant for a preferred embodiment of the process of the invention for preparing formamide compound (Ia2) from carbon dioxide, hydrogen and amine (Ic) without the addition of a polar solvent.
Reference numerals in FIGS. 1, 2 and 3 have the following meanings.
1
I-1 Hydrogenation Reactor
II-1 Distillation Unit
1 stream containing carbon dioxide
2 stream containing hydrogen
Stream Containing 3 Amines (Ic)
A stream comprising 4 formamide compound (Ia2), water of reaction, unreacted amine (Ic); Post Treated Hydrogenation Mixture (Hw)
A stream comprising 5 formamide compound (Ia2); Target product; First stream
A stream comprising 6 reaction water; Third stream
7 stream comprising unreacted amine (Ic), second stream
2
I-2 hydrogenation reactor
II-2 Distillation Unit
11 stream containing carbon dioxide
12 streams containing hydrogen
13 stream containing alcohol (lb)
A stream comprising 14 formic acid ester (Ia1), water of reaction, unreacted alcohol (Ib); Post Treated Hydrogenation Mixture (Hw)
A stream comprising 15 formic acid ester (Ia2); Target product; First stream
A stream comprising 16 reaction water; Third stream
17 stream comprising unreacted amine (Ic), second stream
3
I-3 Hydrogenation Reactor
II-3 Distillation Unit
Stream containing 21 carbon dioxide
22 stream containing hydrogen
Stream Containing 23 Amines (Ic)
A stream comprising 24 formamide compound (Ia2), water of reaction, polar solvent, unreacted amine (Ic); Post Treated Hydrogenation Mixture (Hw)
A stream comprising 25 formamide compound (Ia2); Target product; First stream
A stream comprising 26 reaction water; Third stream
27 stream comprising unreacted amine (Ic), second stream
Stream containing 28 polar solvents
In the embodiment shown in FIG. 1, carbon dioxide, stream (1), hydrogen, stream (2), and amine (Ic), stream (3) are fed to hydrogenation reactor (I-1). Here, the stream is reacted in the presence of a heterogeneous gold catalyst to provide formamide compound (Ia2) and water of reaction. The heterogeneous catalyst is separated from the liquid hydrogenation mixture (H) comprising formamide compound (Ia2), water of reaction, heterogeneous catalyst and unreacted amine (Ic). The worked up hydrogenation mixture (Hw) thus obtained is fed as distillation unit (II-1) as stream (4). Here, the workup hydrogenation mixture (Hw) is fractionally distilled to give formamide compound (Ia2), stream (5), effluent of the reaction water, stream (6) and unreacted amine (Ic), stream (7). And it is recycled to the hydrogenation reactor (II-1).
In the embodiment shown in FIG. 2, carbon dioxide, stream 11, hydrogen, stream 12 and alcohol (lb), stream 13 are fed to hydrogenation reactor (I-2). Here, the stream is reacted in the presence of a heterogeneous gold catalyst to provide formic acid ester (Ia1) and water of reaction. The heterogeneous catalyst is separated from the liquid hydrogenation mixture (H) comprising formic acid ester (Ia1), water of reaction, heterogeneous catalyst and unreacted alcohol (Ib). The work up hydrogenation mixture (Hw) thus obtained is fed as distillation unit (II-2) as stream (14). Here, the workup hydrogenation mixture (Hw) is fractionally distilled to give formic acid ester (Ia1), stream (15), the discharge of the water of reaction, stream (6) and unreacted alcohol (lb), stream (17) , Which is recycled to the hydrogenation reactor (II-2).
In the embodiment shown in FIG. 3, carbon dioxide, stream 21, hydrogen, stream 22 and amines (Ic), stream 23 are fed to a hydrogenation reactor (I-3) which also comprises a polar solvent. In the reactor, the stream is reacted in the presence of a heterogeneous gold catalyst to provide formamide compound (Ia2) and water of reaction. The heterogeneous catalyst is separated off from the liquid hydrogenation mixture (H) comprising formamide compound (Ia2), water of reaction, polar solvent, heterogeneous catalyst and unreacted amine (Ic). The worked up hydrogenation mixture (Hw) thus obtained is fed as stream 44 to distillation unit (II-3). The post-treated hydrogenation mixture (Hw) was fractionally distilled to form formamide compound (Ia2), stream (25), effluent of the reaction water, stream (26), and unreacted amine (Ic), stream (27). Which is recycled to the hydrogenation reactor (II-3) and also the polar solvent is recycled to the hydrogenation reactor (II-3) as stream 28 as well.
The invention is illustrated with the aid of the following examples, without being limited thereto.

Example

Heterogeneous gold catalyst, made of Hastelloy C and equipped with a magnetic stir bar, placed in the catalyst basket and starting materials (alcohol (Ib) or amine (Ic)) as described in Table 1 below in each case under inert conditions Charged. In the synthesis of formic acid esters the amine was introduced when the corresponding alcohol, or liquid amine, was used. The autoclave was subsequently sealed and pressurized with carbon dioxide (CO ₂ ), hydrogen (H ₂ ) and optionally ammonia or dimethylamine at room temperature and the reactor was heated with stirring (700 rpm). After the appropriate reaction time, the reactor was cooled down and the reaction mixture was depressurized. The catalyst was kept in a catalyst basket. The composition of the reaction solution (after-treated hydrogenation mixture (Hw)) was measured by gas chromatography, and the gold content was measured by atomic absorption spectroscopy (AAS). The parameters and results of the individual experiments are shown in Table 1.

Examples A-1 to A-11 show that formamide and formic acid ester can be easily obtained by hydrogenation of CO ₂ using a gold catalyst. Gold was not found in the reaction solution (after-treated hydrogenation mixture (Hw)) within the detection limit, which makes it very simple to separate the catalyst and recycle it.

Comparative experiment:

Comparative Examples A12 and A13 are standard hydrogenation catalysts, such as Raney nickel or palladium on carbon, where other conditions are used the same as for gold catalysts, where no formamide is produced (in Raney nickel) or only significantly lower. It is shown that the yield (1/5 times Pd) can be achieved. This shows the advantage of the use of the catalyst according to the invention in this reaction.

Claims (14)

Reaction mixture (Rm) comprising carbon dioxide, hydrogen, and an alcohol of formula (Ib) or an amine of formula (Ic) below at a pressure in the range of 0.2-30 MPa and a temperature in the range of 20-200 ° C. in the presence of a catalyst comprising gold in a hydrogenation reactor A process for producing a carboxylic acid derivative of formula (Ia) by reacting
<Formula Ia>
H- (C = O) -R
(Wherein,
R is selected from the group consisting of OR ¹ and NR ² R ³ , wherein
R ¹ is unsubstituted or at least monosubstituted C ₁ -C ₁₅ -alkyl, C ₅ -C ₁₀ -cycloalkyl, C ₅ -C ₁₀ -heterocyclyl, C ₅ -C ₁₀ -aryl or C ₅ -C ₁₀ Heteroaryl,
Wherein the substituent is selected from the group consisting of C ₁ -C ₁₅ -alkyl, C ₁ -C ₆ -alkoxy, C ₅ -C ₁₀ -cycloalkyl and C ₅ -C ₁₀ -aryl;
R ² and R ³ are each, independently of one another, hydrogen, unsubstituted or at least monosubstituted C ₁ -C ₁₅ -alkyl, C ₅ -C ₁₀ -cycloalkyl, C ₅ -C ₁₀ -heterocyclyl, C ₅ -C ₁₀ -aryl or C ₅ -C ₁₀ -heteroaryl,
Wherein the substituent is selected from the group consisting of C ₁ -C ₁₅ -alkyl, C ₅ -C ₁₀ -cycloalkyl and C ₅ -C ₁₀ -aryl, or
R ² and R ³ , together with the nitrogen atom, optionally further comprise one or more heteroatoms selected from O, S and N and form a 5- or 6-membered ring with substituent R ⁴ , wherein
R ⁴ is hydrogen or C ₁ -C ₆ -alkyl
(Ib)
R ¹ -OH
Wherein R ¹ has the meaning
<Formula I>
NHR ² R ³
(Wherein R ² and R ³ each independently have the above meaning) The process of claim 1 wherein the catalyst is a heterogeneous catalyst. The method of claim 1 or 2, wherein the catalyst comprises at least one support material. 4. The method of claim 3 wherein the support material is selected from the group consisting of silicon dioxide, aluminum oxide, zirconium oxide, magnesium oxide and titanium oxide. The process according to claim 3 or 4, wherein the heterogeneous catalyst comprises 0.1 to 20% by weight of gold, based on the total mass of the supported catalyst used. 6. The compound of claim 1, wherein R ¹ is unsubstituted or at least monosubstituted C ₁ -C ₈ -alkyl, wherein the substituents are C ₁ -C ₆ -alkyl and C ₁ -C _6- . Wherein an alcohol of formula (Ib) is used, which is selected from the group consisting of alkoxy. The process according to claim 6, wherein the alcohol (Ib) is methanol, ethanol, 2-methoxyethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 1-pentanol, Wherein an alcohol selected from the group consisting of 1-hexanol, 1-heptanol and 1-octanol is used. 8. Process according to claim 6 or 7, wherein methanol is used as alcohol (Ib) and methyl formate is obtained as carboxylic acid derivative (Ia). Ammonia, methylamine, dimethylamine, ethylamine, diethylamine, n-propylamine, di-n-propylamine, isopropylamine, according to any one of claims 1 to 5, Wherein an amine selected from the group consisting of diisopropylamine, n-butylamine, di-n-butylamine, isobutylamine, diisobutylamine, morpholine, piperidine and piperazine is used. 10. The process according to claim 9, wherein an amine selected from the group consisting of ammonia, methylamine and dimethylamine is used as the amine (Ic). The process according to claim 9 or 10, wherein ammonia is used as the amine (Ic) and formamide is obtained as the carboxylic acid derivative (Ia). The process according to any one of claims 1 to 11, wherein the residence time of the reaction mixture (Rm) in the hydrogenation reactor is 10 minutes to 5 hours. The process of claim 12 wherein the mixture obtained in the reaction is worked up in a distillation apparatus,
A first stream comprising a carboxylic acid derivative (la),
A second stream comprising unreacted alcohol (Ib) or unreacted amine (Ic), and
A third stream comprising water of reaction formed in the reaction
How to give it. The process according to claim 12 or 13, wherein the second stream is recycled to the hydrogenation reactor.

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