KR100308731B1 - Hydrogenation of carbon dioxide and hydroformylation using rhodium catalyst/salt co-catalyst system - Google Patents

Abstract

The present invention provides aldehydes, alkylesters or carboxylic acids by hydroformylation, carboalkoxylation or carboxylation of olefins in the presence of a rhodium catalyst system comprising a rhodium component as a catalyst and a salt as a promoter, or hydrogenated carbon dioxide to formic acid, The present invention relates to a method for preparing methyl formate, methanol, ethanol, and the like, and the catalyst system of the present invention using a salt cocatalyst together with a rhodium catalyst can perform the above reactions with high reactivity, selectivity, and catalyst stability.

Description

HYDROGENATION OF CARBON DIOXIDE AND HYDROFORMYLATION USING RHODIUM CATALYST / SALT CO-CATALYST SYSTEM}

The present invention relates to various reactions characterized by the use of rhodium catalysts / salt cocatalysts, in particular the hydrogenation of carbon dioxide and the hydroformylation, carboalkoxylation and carboxylation of olefins.

Since rhodium is a metal component that shows excellent ability in various catalytic reactions, it is particularly used for the conversion of double bonds, and is typically used for hydroformylation reaction, which is known as oxo reaction, to synthesize aldehyde by reacting olefin and synthesis gas. have. The reaction using rhodium as the core metal of the catalytic reaction is very diverse. In most cases, however, the reaction proceeds in the liquid phase, so that rhodium in the molecular state is dissolved in the reaction solvent. This condition causes a problem of the stability of the rhodium catalyst, so a stable ligand is usually placed around the rhodium to increase the selectivity while maintaining the stability of the rhodium. Therefore, in the reaction of rhodium, in most cases, phosphine-based compounds such as triphenylphosphine compounds are used as additives. However, phosphine compounds are oxidized over time and converted to phosphine oxides, which are readily liberated in the system, resulting in a decrease in the reactivity and stability of the rhodium metal.

On the other hand, carbon dioxide is a special form of unsaturated double bonds, and it has been reported that the synthesis of formic acid by hydrogenation of carbon dioxide is possible by the catalytic system of gold rhodium and phosphine ligand (Paperner, Angew. Chem. , Int. Ed. Engl. Vol. 34, page 2207). Here, in order to enable thermodynamic synthesis of formic acid, an amine is added to form the resulting formic acid and an acid group compound. However, this reaction only showed that carbon dioxide was hydrogenated by rhodium, and commercially it had its own limitations. That is, carbon dioxide, which is a reactant, has a property of acting as an oxidant, thereby directly oxidizing phosphine, which is a reaction catalyst system, to synthesize phosphine oxide, thereby rapidly decreasing reactivity and in some cases, rhodium is also precipitated in oxide form.

Accordingly, it is an object of the present invention to improve the reactivity and selectivity in the reaction using a rhodium-based catalyst and to improve the stability of the rhodium catalyst.

In order to achieve the above object, the present invention provides a method for preparing an aldehyde, alkyl ester or carboxylic acid by hydroformylation, carboalkoxylation or carboxylation of olefin in the presence of a rhodium catalyst system comprising a rhodium component as a catalyst and a salt as a promoter. To provide.

The present invention also provides a process for producing formic acid, methyl formate, methanol and ethanol by hydrogenating carbon dioxide in the presence of the rhodium catalyst system.

Hereinafter, the present invention will be described in more detail.

The present invention is characterized in that the catalytic reaction is carried out using a rhodium catalyst system consisting of a rhodium catalyst and a salt promoter.

The rhodium / salt catalyst system according to the present invention has a high solubility in aqueous solution due to its characteristics, and thus has a great advantage in that reactions based on conventional rhodium can be carried out in aqueous solution. When the reaction proceeds in an aqueous phase, the product of the reaction forms an organic layer that is insoluble in water, and the catalyst is dissolved in the water layer, which is advantageous for the recovery time of the reaction product. Roplan in France converts phosphine into water-soluble form, for example tris (3-sulfonatotophenyl) phosphine with SO ₃ Na in the phenyl group, sodium salt and then uses it to react with oxo Although it was proceeded to the aqueous phase, in this case, the degree of oxidation of phosphine is more severe than in the conventional oxo reaction, and the price of this water-soluble phosphine salt is also very expensive, which requires a lot of effort to recover and regenerate it. On the contrary, in the present invention, since the phosphine does not need to be used due to the increased stability of the catalyst due to the addition of the salt, the above problem when using the water-soluble phosphine does not occur.

The rhodium compound which can be used for the preparation of the rhodium catalyst used in the rhodium / salt catalyst system according to the present invention can be used as long as it can be dissolved in an organic solvent or an aqueous solution. Representative rhodium compounds include RhX ₃ and RhX ₃ · nH. ₂ O, Rh ₂ (CO) ₄ X ₂ , [Rh (CO) X ₄ ] Na, Rh ₂ (CO) ₈ , Rh [(C ₆ H ₅ ) ₃ P] ₂ (CO) X, Rh (NO ₃ ) ₃ , RhX [(C ₆ H ₅ ) ₃ P] ₂ (CH ₃ I) ₂ , Rh (SnCl ₃ ) [(C ₆ H ₅ ) ₃ P] ₃ , RhX (CO) [(C ₆ H ₅ ) ₃ As] ₂ , RhI (CO) [(C ₆ H ₅ ) ₃ Sb] ₂ , Y [Rh (CO) ₂ X ₂ ], [(nC ₄ H ₉ ) ₄ N] [Rh (CO) ₂ X ₂ ], [Rh (CO) X ₄ ] Y, [(nC ₄ H ₉ ) ₄ As] ₂ [Rh (CO) ₂ Y ₄ ], [(nC ₄ H ₉ ) ₄ P] [Rh (CO) X ₄ ], Rh [(nC ₄ H ₉ ) ₃ P] ₂ (CO) X, RhX [(C ₆ H ₅ ) ₃ P] ₃ , RhX [(C ₆ H ₅ ) ₃ P] H ₂ , Rh (CO) H [(C ₆ H ₅ ) ₃ P] ₃ , [Rh (C ₂ H ₄ ) ₂ X] ₂ , Y ₄ Rh ₂ X ₂ (SnCl ₃ ) ₄ , Rh (CO) ₂ acetylacetonate, RhH (PPh ₃ ) _4, etc. (where X is a halide such as Cl ⁻ , Br ⁻ or I ^−, and Y is an alkali metal such as Li, Na, K or Rb or Mg, Ca, Sr or Ba and Same alkaline earth metal).

Salt is used as cocatalyst in the catalyst system according to the present invention is _{^{PO 4 -, I -, Br}} -, Cl -, NO 3 -, CH 3 COO -, NCO -, CN -, CNO -, SCN -, CO 3 ^-, SO ₄ ^- anion, and _{NR 1 R 2 R 3 R 3} (R 1, R 2, R 3 = H or C _{1-15 ^{alkyl), PPN +, (PhP =}} N = PPh) +, alkali metals, such as , Alkaline earth metals, transition metals, cations such as Al, Ga, Sn, Pb, In, and the like, and may be appropriately selected depending on the desired product. For example, the selectivity of formic acid during the hydrogenation of carbon dioxide in the case of negative ions NO ₃ ^-> I ^-> an order of PO ₄ ^3-, selectivity for methanol is the opposite and, in the case of the cation is Al ^3+> Cr ^{3 +} > K ⁺ > NH ₄ ^{+ in} order to have a reactivity.

Solvents that can be used in the reaction using the catalyst system of the present invention are esters, ethers, alcohols, aldehydes, ketones, hydrocarbons, DMSO (dimethyl sulfoxide) and the like, which promotes the reaction more efficiently as the polarity increases.

In the catalyst system according to the present invention, the reaction can be freely selected at a temperature ranging from room temperature to 300 ° C., and the reaction is performed at various temperatures according to the type of reaction. In the case of the oxidization of olefins, temperatures in the range of 100 to 150 ° C. show optimum reactivity and selectivity. The reactivity increases with the pressure of the gas used in the reaction and the reaction can proceed under a pressure in the range of 1 atm to 300 atm, preferably at 40 to 80 atm.

The rhodium / salt catalyst system according to the invention can be used for the reaction as such or in the presence of a certain amount, for example, on a rhodium basis, in the presence of 0.01 to 100 equivalents of phosphine compound, in most cases of liquid phase reactions. It leads to an improvement in stability and reactivity, especially when there is a double bond such as olefins.

For example, the rhodium / salt catalyst system of the present invention may be used to selectively generate n-aldehyde by carrying out an oxo reaction between an olefin and a synthesis gas as in Scheme 1 below.

CH ₂ = CH-R + CO / H ₂ → HCOCH ₂ -CH ₃ -R

In this reaction, in some cases, the addition of a predetermined amount of phosphine compound (PPh ₃ ) may partially increase the selectivity of the n-structure compound.

Olefins usable in the reaction include compounds having 2 to 20 carbon atoms, and examples thereof include ethylene, propylene, butylene, pentene, hexene, heptene, oxene and the like. The reaction can be completed by running for approximately 1 hour at a temperature in the range of about 70 to 150 ° C.

The catalyst system according to the present invention can also be usefully used for hydrogenation of carbon dioxide, such as Scheme 2 below. By controlling the amount of rhodium and phosphine, the hydrogenation reactivity of the catalyst is further improved, and as a reaction product, it is possible to synthesize not only formic acid but also methyl formate and methanol, and even ethanol, and methyl acetate, acetic acid and acetaldehyde as by-products. May be generated.

CO ₂ + nH ₂ → CH ₃ OH + CH ₃ CH ₂ OH + CH ₃ OCOH + HCOOH + CH ₃ COOH + CH ₃ COOCH ₃ + CH ₃ CHO

To date, there have been many efforts to synthesize methanol from carbon dioxide, but in most cases, the reaction proceeds under severe conditions such as high temperature of 1000 atmospheres (Inoue, Y. Chem. Commun., 718, 1975] and [Chem. Letter, 863, 1975], and the most recent relaxed conditions are catalyst systems based on Ru as reported by Tominaga, K. et al. This catalyst also requires harsh reaction conditions of 200 atm and 190 ° C. (see J. Chem. Soc., Chem. Commun., 629, 1993). However, using the catalyst system of the present invention shows a remarkable reactivity in which the hydrogenation proceeds at low reaction pressures of 40 to 50 atm and even at room temperature. A predetermined amount of alkylphosphine may be added to give the selectivity of the reaction, but the addition of conventional PPh ₃ greatly increases the selectivity to formic acid. The reaction temperature can be appropriately selected depending on the compound selected within the range of room temperature to 200 ° C.

In addition, the use of phosphites in the hydrogenation reaction can increase the selectivity of alcohols, such as cyclic phosphites (eg, P [O (CH ₂ ) n] CR, n = 1-20, R = C _{1- 20} ) can change the selectivity of the alcohol. The cyclic phosphite can be used in amounts ranging from 0.1 to 100 equivalents based on rhodium. Some carbon monoxide may be used in combination with carbon dioxide to change the selectivity of the reaction and increase the amount of alcohol synthesized, with carbon monoxide alone having a high yield of alcohol synthesis (ie CO / CO + CO ₂ = 0 to 1).

Due to its stability, the rhodium / salt catalyst system according to the present invention is also highly reactive in the synthesis of alkyl esters by carboalkoxylation of olefins of Schemes 3 and 4 and the synthesis of carboxylic acids by carboxylation, which are considered to be difficult to date. And selectivity.

In the above reaction, the alcohol participating in the reaction has 1 to 20 carbon atoms, and any alcohol can be used as long as it can be dissolved in the reaction system. In the case of using carbon monoxide and water or carbon monoxide and alcohol as reactants, a reaction may be promoted by adding a certain amount of hydrogen to prepare an active catalyst, or alternatively, by using rhodium in the form of hydride. . In addition, an acid capable of providing H ⁺ to the reaction system may be added to change the selectivity of the reaction. The acid may be selected from inorganic acids such as HCl, HNO ₃ , H ₂ SO ₄ and organic acids such as acetic acid and p-toluenesulfonic acid as appropriate. The reaction is carried out under conditions of 1 to 100 atm of carbon monoxide, preferably at 10 to 50 atm. If the temperature is too high, the reaction proceeds quickly but it is preferred to use a temperature range in the range of 100 to 120 ° C. to maintain selectivity.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

Example 1 Hydrogenation of Carbon Dioxide

20 ml of DMSO, 23 mg (0.02 mmol) of HRh (PPh ₃ ) ₄ and 146 mg (1.45 mmol) of NEt ₃ were added to a 150 ml high-pressure reactor, and hydrogen and carbon dioxide were supplied to a partial pressure of 20 atm and 40 atm, respectively. . To this was added 26 mg (0.1 mmol) of triphenylphosphine and a salt as described in Table 1 below was added 10 molar times relative to rhodium as cocatalyst. After the reaction was performed for 5 hours while mechanically stirring the reactor at room temperature, the reaction product was analyzed by 1 H NMR (for measuring HCOOH), gas chromatography (for analyzing other organic products) and mass spectrometer. Formic acid was analyzed in combination with amines. The amount of reaction product produced is shown in Table 1 below. For comparison, the same reaction was carried out without using salts and the results are shown in Table 1 below.

Type of added salt Formic Acid Production (mmol) Methyl Formate Production (mmol) Methanol Production (mmol) none 420 - - KNO ₃ 1250 20 50 NaNO ₃ 930 18 48 NH ₄ NO ₃ 960 18 50 LiNO ₃ 1100 21 52 Na ₃ PO ₄ 800 80 75 KI 950 70 80 K ₂ SO ₄ 530 10 30 K ₂ CO ₃ 690 2 15 PPNNO ₃ 1200 22 55

Example 2

RhCl (PPh ₃ ) ₃ was used as the rhodium component, and the analysis results of the reaction products according to the added salts are shown in Table 2 below.

Type of added salt Formic Acid Production (mmol) Methyl Formate Production (mmol) Methanol Production (mmol) none 380 - - KNO ₃ 1250 21 30 NaNO ₃ 950 18 29 NH ₄ NO ₃ 680 11 15 LiNO ₃ 930 42 54 Al (NO ₃ ) ₃ 650 130 120 Cr (NO ₃ ) ₃ 640 150 150 Na ₃ PO ₄ 850 85 65

Example 3

In the same manner as in Example 1, 10 mole times of potassium nitrate was used as the cocatalyst, and 6 mole times of phosphine was used, and the reaction solvent was changed as shown in Table 3 below. The analysis results of the reaction products are shown in Table 3 below.

Solvent used Formic Acid Production (mmol) Methyl Formate Production (mmol) Methanol Production (mmol) Heptane - - - benzene - - - DMSO 650 - - THF - - - Methanol 1800 10 Methanol / cyclic phosphite ^* - 10 DMSO / Methanol 1200 10 DMSO / water 700 10 15 DMSO / cyclic phosphite - 7 100 water - 35 20 Water / cyclic phosphite - 80 300

* Cyclic phosphite: ETPO (P (OCH ₂ ) ₃ CC ₂ H ₅ )

Example 4

In the same manner as in Example 1, using potassium nitrate or potassium iodide as cocatalyst 20 mole times relative to rhodium, phosphine amount to 12 mole times relative to rhodium, and the kind of rhodium compounds used in the catalyst system and the kind of salt The change was made as shown in Table 4. The analysis results of the reaction products are shown in Table 4 below.

Catalyst system Formic Acid Production (mmol) Methyl Formate Production (mmol) Methanol Production (mmol) RhCl (PPh ₃ ) ₃ w / o KNO ₃ 450 - - RhCl (PPh ₃ ) ₃ + KNO ₃ 1250 18 50 RhCl ₃ + KI 700 10 10 RhCl ₃ + KNO ₃ 500 10 10 Rh (CO) ₂ acetylacetonate + KNO ₃ 700 850 650 Rh (CO) ₂ acetylacetonate + KI 750 250 80

Example 5

In the same manner as in Example 1, using RhCl ₃ compound as a catalyst potassium nitrate as a catalyst, the solvent was changed as shown in Table 5. The analysis results of the reaction products are shown in Table 5 below.

Solvents and catalysts Formic Acid Production (mmol) Methyl Formate Production (mmol) Methanol Production (mmol) DMSO / RhCl (PPh ₃ ) ₃ 1250 10 - DMSO / CH ₃ OH (1: 1) / RhCl (PPh ₃ ) ₃ 1800 10 100 CH ₃ OH / RhCl (PPh ₃ ) ₃ 10 10 100 DMSO / RhCl ₃ 450 10 - DMSO / CH ₃ OH (3: 1) 550 10 10

Example 6

In the same manner as in Example 1, using RhCl ₃ as a catalyst, and using potassium nitrate, potassium iodide or potassium carbonate at 20 molar times of rhodium as a cocatalyst, carbon monoxide in the reaction to determine the effect of carbon monoxide in Table 6 It was added to the reaction system as in. The analysis results of the reaction products are shown in Table 6 below.

salt P _CO2 (atm) P _H2 (atm) P _CO (atm) Methanol ethanol Methylformate Formic acid KNO ₃ 40 20 - 40 - 10 1250 KNO ₃ 20 20 20 40 10 10 - KI 40 20 - 30 25 40 850 KI 20 20 20 35 20 50 - K ₂ CO ₃ 40 20 - 150 90 120 750 KNO ₃ ? 25 25 25 - - -

Example 7: Hydroformylation of Hexene

C ₇ aldehyde was synthesized by reacting 1-hexene with syngas at 100 ° C. in a high pressure reactor at 120 ° C. and 60 atm. In this case, as the catalyst system, rhodium compounds and salts as shown in Table 7 were used. The rhodium compound was 0.1 mmol and the salt was used 10 mol times compared to rhodium. No separate phosphine was added to the reaction, and a synthesis gas containing a mixture of carbon monoxide and hydrogen in a molar ratio of 1: 1 was used under 50 atm, and 30 ml of xylene was used as a reaction solvent. After 3 hours of reaction, the reaction product was analyzed by gas chromatography and mass spectrometry, and the results are shown in Table 7 below.

Rhodium compound salt Aldehyde (mmol) Rhacac (CO) ₂ PPNCl 35 Rhacac (CO) ₂ KNO ₃ 50 Rhacac (CO) ₂ KI 30 Rhacac (CO) ₂ NEt ₃ Cl 32 Rhacac (CO) ₂ Na ₃ PO ₄ 30 Rhacac (CO) ₂ K ₂ CO ₃ 28 Rhacac (CO) ₂ PPNCN 28 Rhacac (CO) ₂ PPNacetate 36 Rhacac (CO) ₂ NH ₄ NCO 37 Rhacac (CO) ₂ K ₂ SO ₄ 30 RhCl (PPh ₃ ) ₃ PPNBr 42 RhCl (PPh ₃ ) ₃ K ₂ CO ₃ 40 RhCl (PPh ₃ ) ₃ KNO ₃ 65 RhCl (PPh ₃ ) ₃ NEt ₄ Cl 48 RhCl (PPh ₃ ) ₃ PPNI 40 RhCl (PPh ₃ ) ₃ LiCl 35

Rhacac (CO) ₂ : Rh (CO) ₂ acetylacetonate

Example 8

Example 7 was carried out in the same manner as in the reaction solvent, but 30 ml of water was used as the reaction solvent, and the reaction product was analyzed for 3 hours at the beginning of the reaction.

Rhodium compound salt Aldehyde (mmol) Rhacac (CO) ₂ PPNCl 30 Rhacac (CO) ₂ KNO ₃ 46 Rhacac (CO) ₂ KI 32 Rhacac (CO) ₂ Na ₃ PO ₄ 25 Rhacac (CO) ₂ K ₂ CO ₃ 20 Rhacac (CO) ₂ PPNCN 22 Rhacac (CO) ₂ PPNacetate 36 Rhacac (CO) ₂ NH ₄ NCO 32 Rhacac (CO) ₂ K ₂ SO ₄ 20 RhCl (PPh ₃ ) ₃ PPNBr 25 RhCl (PPh ₃ ) ₃ K ₂ CO ₃ 23 RhCl (PPh ₃ ) ₃ KNO ₃ 45 RhCl (PPh ₃ ) ₃ NEt ₄ Cl 40 RhCl (PPh ₃ ) ₃ LiCl 30

Example 9: Carbomethoxylation of Propylene

Carbomethoxylated propylene with a carbon monoxide partial pressure of 30 atm in a methanol solvent in a 100 ml high pressure reactor. In this case, Rhacac (CO) ₂ and salts as shown in Table 9 were used as the catalyst system. The rhodium compound was 6 mmol and the salt was used 10 mol times compared to the rhodium. 5 ml of methanol was added, 15 ml of xylene was added as a solvent, and the reaction was performed at 120 ° C. for 4 hours (from the start of the reaction). Hydrogen was added at a partial pressure of 10 atm in order to advance the reaction start time and increase the reaction rate. The reaction product of the reaction was analyzed by gas chromatography and mass spectrometry, and the results are shown in Table 9 below.

salt % Conversion PPNCl 70 KNO ₃ 75 KI 50 Na ₃ PO ₄ 45 K ₂ CO ₃ 50 PPNCN 55 PPNacetate 60 NH ₄ NCO 55 K ₂ SO ₄ 35 KI 10

Using a catalyst system using a salt promoter together with a rhodium catalyst according to the present invention, hydroformylation, carboalkoxylation and carboxylation of olefins and hydrogenation of carbon dioxide are carried out with high reactivity, selectivity and catalyst stability.

Claims (4)

In the presence of a rhodium catalyst system comprising a rhodium component as a catalyst and an inorganic salt as a promoter which dissolves in the reaction solvent to form a homogeneous system with the rhodium catalyst, at a pressure ranging from 40 to 80 atmospheres and at a temperature ranging from room temperature to 200 ° C or A method of producing a reaction product comprising formic acid, methyl formate, methanol and ethanol by hydrogenating carbon monoxide or a mixture of these gases. The method of claim 4, wherein Said salt is _{^{PO 4 -, I -, Br}} -, Cl -, NO 3 -, CH 3 COO -, NCO -, CN -, CNO -, SCN -, CO 3 - and SO ₄ ^- anion selected from the group consisting of And NR ₁ R ₂ R ₃ R ₃ (R ₁ , R ₂ , R ₃ = H or C _1-15 alkyl), PPN ⁺ _, (PhP = N = PPh) ⁺ , alkali metal, alkaline earth metal, transition metal, Al And cations selected from the group consisting of Ga, Sn, Pb and In. The method of claim 4, wherein A method for adding a phosphine compound to the reaction system. The method of claim 4, wherein The method characterized by further adding a phosphite compound to the reaction system.