PROCESS FOR PRODUCING 2-HYDROXY-METHYLENE-3,3-DIALKOXYPROPANE-NITRILE ALKALI METAL SALT AND PROCESS FOR OBTAINING ALCOHOLIC SLURRY OF SAID COMPOUND FROM ITS SYNTHETIC REACTION MIXTURE

Abstract: There are disclosed a process for producing a 2-hydroxy­ methylene-3,3-dialkoxypropanenitrile alkali metal salt (ALVM₂) represented by the formula (I): wherein R represents a lower alkyl group having 1 to 4 carbon atoms and M represents an alkali metal, which comprises allowing a 3,3-dialkoxypropanenitrile represented by the formula (II): (RO)₂CHCH₂CN (II) wherein R is the same as defined above, to react with carbon monoxide in a lower alcoholic solu­ tion of an alkali metal lower alkoxide; and a process for obtaining ALVM₂, which comprises adding a lower alcohol having 1 to 4 carbon atoms to a synthetic reaction mixture containing ALVM₂ represented by the above formula (I) and methyl formate and heating the mixture to 30 to 70 °C, thereby taking methyl formate out of the system.

Description: This invention relates to a process for producing 2-hydroxymethylene-3,3-dialkoxypropanenitrile alkali metal salt and a process for obtaining alcoholic slurry of said compound from its synthetic reaction mixture. 2-hydroxymethylene-3,3-dialkoxypropanenitrile alkali metal salt (hereinafter called "ALVM₂") is useful as the synthetic intermediate for vitamin B₁, and has been produced from 3,3-dialkoxypropanenitrile (hereinafter called "DAPN") according to the normal pressure methyl formate process (Japanese Provisional Patent Publication No. 19755/1985) or the high pressure carbon monoxide process (Japanese Provisional Patent Publication No. 84526/1979 and Japanese Patent Publication No. 21623/1986), of which the latter is said to be more advantageous. The normal pressure process is a process, in which the reaction between DAPN and methyl formate is carried out in the presence of an alkali metal alcoholate, and the reaction is permitted to proceed by expelling the methanol formed by the reaction out of the system. The high pressure carbon monoxide process is a process in which DAPN, carbon monoxide and methanol are allowed to react in the presence of an alkali metal alcoholate. In either process, a large amount of methyl formate coexists in the reaction mixture after completion of the reaction. In spreading the methyl formate from the ALVM₂ obtained by the reaction, it is important to obtain a slurry with good flowability without deterioration of ALVM₂ and methyl formate. Further, if methyl formate can be taken out of the system, the reaction can be made more economical by reutilization thereof. Methyl formate can be expelled out of the system by filtration or drying. However, according to the method by filtration, because methyl formate has a boiling point of 31.5°C and an ignition point of -19°C, which are both low, and also exhibits excessive toxicity to human body, special care is required for separation, recovery operation of methyl formate attached on the crystals, typically filtration operation, such as making the system a closed system, etc. On the other hand, since the filtrate obtained contains dissolved ALVM₂ and sodium methylate, etc. remained therein, it cannot be utilized as such, and it is not necessary to perform separation operation such as distillation, etc. Besides, during the separation operation of methyl formate, deterioration (decomposition) of the remaining ALVM₂ or decomposition of methyl formate by the catalytic action of sodium methylate are caused to occur, whereby recovery of methyl formate will be lowered. The method by drying is the method, in which the reaction mixture slurry is led as such into a dryer and dried all at once by evaporation of methyl formate, etc., which may be expected to be an industrially advantageous method and experiments were conducted by use of various dryers provided with functions of stirring blade, etc. As the result, troubles of scaling and solidification particularly at the heat transmission surface occurred, and also deterioration (decomposition) of ALVM₂ and lowering in recovery of methyl formate occurred similarly as in the case of the method by filtration. Thus, it may be judged to be industrially practiced with difficulty. On the other hand, the above known high pressure carbon monoxide process comprises allowing DAPN, carbon monoxide and an alkali metal alkoxide to react in a solvent, including ethers such as ethyl ether, dioxane, tetrahydrofuran, etc.; aromatic hydrocarbons such as benzene, toluene, etc.; and so on. However, the yield of the desired ALVM₂ in the above known high pressure carbon monoxide process is at most about 97%, which cannot be said to be sufficiently satisfactory. Accordingly, the present inventors have intensively studied in order to make the yield of the high pressure carbon monoxide process sufficiently satisfactory, and consequently found that the desired product can be obtained substantially quantitatively by carrying out the reaction in a lower alcoholic solution of an alkali metal lower alkoxide. The present invention concerns a process for producing ALVM₂ represented by the formula (I): wherein R represents a lower alkyl group having 1 to 4 carbon atoms and M represents an alkali metal, which comprises reacting 3,3-dialkoxypropanenitrile represented by the formula: (RO)₂CHCN₂CN wherein R is as defined above, with carbon monoxide, said reaction occuring at from 20 to 100°C in a 20 to 35 wt% C₁-C₄ lower alcoholic solution of an alkali metal C₁-C₄ lower alkoxide, the molar ratio of alkali C₁-C₄ lower alkoxide to 3,3-dialkoxypropanenitrile ranging from 1.0 to 1.3: 1, and the carbon monoxide being delivered into the system at from 2.0 to 9.8 MPa (20 to 100 kg/cm² (gauge pressure)). The present invention also concerns a process for obtaining ALVM₂, which comprises adding a lower alcohol having 1 to 4 carbon atoms to a synthetic reaction mixture containing ALVM₂ represented by the above formula (I) and methyl formate and heating the mixture to 30 to 70°C, thereby taking methyl formate out of the system. Fig. 1 is a diagram showing the steps in Example 2. In the above formulae (I) and (II), the lower alkyl group represented by R may be exemplified by a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group and a tert-butyl group. In the above formula (I), the alkali metal represented by M may be include sodium, potassium, lithium, etc. The lower alcohol to be used in the present invention is a lower alcohol having 1 to 4 carbon atoms, as exemplified by methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, sec-butyl alcohol and tert-butyl alcohol, etc. The alkali metal lower alkoxide to be used in the present invention corresponds to the above lower alcohol. The amount of the alkali metal lower alkoxide employed may be generally 1.0 to 1.3 moles, preferably 1.03 to 1.15 moles, per one mole of DAPN. The concentration of the alkali metal lower alkoxide in the lower alcoholic solution may be generally 20 to 35% by weight, preferably 24 to 30% by weight. The pressure of the carbon monoxide gas delivered into the system may be generally 2.0 to 9.8 MPa (20 to 100 kg/cm² (gauge pressure)), preferably 2.9 to 5.9 MPa (30 to 60 kg/cm² (gauge pressure)). The reaction temperature may be generally 20 to 100°C, preferably 40 to 60°C. In the production process of the present invention, a lower alkyl formate will be by-produced through the reaction between carbon monoxide and the lower alcohol. Accordingly, if the lower alkyl formate or the mixture thereof with the lower alcohol is treated with a pyrolysis catalyst and the carbon monoxide generated is used as the starting material, the present invention can be made further economical. As the method for taking out the lower alkyl formate from the reaction mixture, there may be employed, for example, the method according to filtration and the method in which a lower alcohol having 1 to 4 carbon atoms is added and the lower alkyl formate is distilled under normal pressure or reduced pressure. Particularly, when the lower alkyl formate is methyl formate, after the above lower alcohol is added to the reaction mixture, the mixture should preferably be heated to 30 to 70°C under normal pressure. If the treatment temperature is lower than 30°C, methyl formate cannot be taken out of the system, while if it is over 70°C, ALVM₂ which is the product will be decomposed. Said treatment temperature should be particularly preferably 40 to 60°C. The amount of the lower alcohol added should be preferably 50 to 250% by weight based on the ALVM₂ amount in the reaction mixture (calculated as the reaction is effected quantitatively), more preferably 80 to 200% by weight. The synthetic reaction mixture of ALVM₂ to be used in the present invention may be any one, provided that it contains ALVM₂ and methyl formate, irrespectively whether it is obtained by the normal pressure methyl formate process or the high pressure methyl formate process, and also includes reaction mixture according to other synthetic processes. In the present invention, for taking out methyl formate out of the system, distillation is conducted generally under normal pressure, but distillation under reduced pressure may be also feasible. As the method for decomposing a lower alkyl formate into carbon monoxide and the lower alcohol, there may be employed the methods as disclosed in Japanese Provisional Patent Publications No. 167233/1980, No. 32315/1981 (Japanese Patent Publication No. 21482/1982), No. 88801/1981, No. 125212/1981 and No. 123811/1982 (Japanese Patent Publication No. 11525/1984). The pyrolysis catalyst is not particularly limited, but activated charcoal, zeolite itself or a catalyst containing an alkaline earth metal compound or an alkali metal compound as the active component is particularly preferred. The reaction temperature may be generally 200 to 500 °C, preferably 250 to 450°C. The liquid space velocity per one hour (hereinafter called "L.H.S.V.″) may be generally 0.1 to 100, preferably 0.5 to 20. EXAMPLES The present invention is described in more detail by referring to Examples and Comparative examples, but these are not limitative of the present invention at all. Example 1 Into an autoclave made of stainless steel of 800 ml inner volume were charged 92.3 g (0.803 mole) of 3,3-dimethoxypropanenitrile and 160.7 g (sodium methoxide: 0.833 mole) of a methanolic solution of sodium methoxide and, after the system was internally replaced with nitrogen gas, carbon monoxide gas was injected into the autoclave to a pressure of 3.9 MPa (40 kg/cm² (gauge pressure)), and the mixture was heated to 50°C under stirring to initiate the reaction. The reduction in pressure accompanied with the progress of the reaction was supplemented with carbon monoxide gas to maintain the pressure at about 3.9 MPa (40 kg/cm² (gauge pressure)). After the reaction for 2 hours, the autoclave was cooled with ice-cold water and the contents were taken out. The crystals obtained were filtered and then vacuum dried to give 132.0 g (Yield: 99.6%) of 2-hydroxymethylene-3,3-dimethoxypropanenitrile sodium salt. Comparative example 1 Into an autoclave made of stainless steel of 300 ml inner volume were charged 23.0 g (0.200 mole) of 3,3-dimethoxypropanenitrile and 13.0 g (0.240 mole) of powdery sodium methoxide, 12.8 g (0.400 mole) of methanol and 65 ml of toluene and, after the system was internally replaced with nitrogen gas, carbon monoxide gas was heated to under stirring to initiate the reaction. The reduction in pressure accompanied with the progress of the reaction was supplemented with carbon monoxide gas to maintain the pressure at about 3.9 MPa (40 kg/cm² (gauge pressure)). After the reaction for 3 hours, the autoclave was cooled with ice-cold water and the contents were taken out. The crystals obtained were filtered and then vacuum dried to give 32.0 g (Yield: 96.9%) of 2-hydroxymethylene-3,3-dimethoxypropanenitrile sodium salt. Example 2 Following the steps shown in Fig. 1, 2-hydroxymethylene-3,3-dimethoxypropanenitrile sodium salt was produced. Into an autoclave (1) made of stainless steel of 20-liter inner volume were charged 2,019 g (17.55 mole) of 3,3-dimethoxypropanenitrile and 3,750 g (sodium methoxide: 18.51 mole) of a methanolic solution of sodium methoxide and carbon monoxide was injected from the supplementing line (8) to a pressure of 3.9 MPa (40 kg/cm² (gauge)), followed by heating of the mixture to 50°C under stirring to initiate the reaction. The reduction in pressure accompanied with the progress of the reaction was supplemented with carbon monoxide gas to maintain the pressure at about 3.9 MPa (40 kg/cm² (gauge pressure)). At this time, methyl formate may be fed to the methyl formate supplementing line (10) and carbon monoxide gas may be introduced through the carbon monoxide feeding line (12) via the carbon monoxide generating device (5) by decomposition. The reaction was completed in 4 hours, and 2.58 Nm³ of carbon monoxide was necessary. Most of methanol was found to be converted to methyl formate. After the pressure in the autoclave (1) was released by cooling, the reaction mixture was transferred into the methyl formate stripper (2), and 5,270 g of methanol was added through the methanol feeding line (9). The methyl formate stripper (2) was heated to 65°C to distill the methanolic solution of methyl formate, and 7,130 g of a methanolic solution of methyl formate (methyl formate 84.6% by weight) was obtained via the methyl formate condenser (3). On the other hand, 6,647 g of a methanolic solution containing 2,837 g (17.19 mole) of 2-hydroxymethylene-3,3-dimethoxypropanenitrile sodium salt containing no methyl formate was obtained through the ALVM₂ slurry withdrawing line (13). The methanolic solution of methyl formate recovered was passed into the carbon monoxide generating device (5) (reaction tube made of stainless steel of 50 mm in diameter × 3,500 mm in length filled with one liter of a catalyst of activated charcoal carried on KCl). The reaction was carried out under the conditions of L.H.S.V. of 2.0 hr⁻¹, pressure of 4.9 MPa (50 kg/cm² gauge pressure)) and 290°C. The carbon monoxide gas containing methanol exiting from the carbon monoxide generating device (5) was transferred into the condenser (6) to condense methanol, and the gas was delivered to the gas holder (7). Conversion of methyl formate was found to be 99.4% and the gas in the gas holder (7) was carbon monoxide with a purity of 98.0%. Thus, in the carbon monoxide feeding line (12), 0.62 Nm³/hr of carbon monoxide was generated. Further, 1,160 g/h of methanol was recovered from the recovered methanol withdrawing line (11). Conversion was 97.8% based on methyl formate. On the other hand, in the autoclave (1), charging of the starting materials for production of 2-hydroxymethylene-3,3-dimethoxypropanenitrile sodium salt for the next time had been completed, and the reaction could be carried out by controlling the pressure in the autoclave (1) with the gas from the carbon monoxide feeding line (12). Carbon monoxide corresponding to shortage was fed from the bomb through the carbon monoxide supplementing line (8). At this time, methyl formate may be fed to the methyl formate supplementing line (10) and carbon monoxide gas may be introduced through the carbon monoxide feeding line (12) via the carbon monoxide generating device (5) by decomposition. Also, the methanol recovered from the recovered methanol withdrawing line (11) was found to have a quality sufficiently satisfactory for preparation of the methanolic solution in the ALVM₂ slurry withdrawing line (13), and this can be also used in the methanol feeding line (9). Example 3 The reaction mixture slurry obtained in the same amounts of the starting materials and the same manner as in Example 1 was transferred into a round bottom flask of one liter volume equipped with a Claisen type distillation device, a condenser and a stirrer, and 253 g of methanol was added thereto. The flask was heated under stirring to evaporate methyl formate. The end point of this separation procedure was when the inner temperature in the flask reached 65°C. In 339.7 g of the distillate, 68.3% by weight of methyl formate was found to be contained, and the recovery as calculated from the methyl formate amount measured by gas chromatogram immediately after the above reaction was 98.1%. Also, the weight of the flask residual solution was 310.5 g and according to the result of analysis by liquid chromatogram, it was found to contain 42.1% by weight of 2-hydroxymethylene-3,3-dimethoxypropanenitrile as calculated on sodium salt, which corresponded to a yield of 98.7% based on 3,3-dimethoxypropanenitrile provided for the reaction in Example 1. Comparative example 2 The reaction mixture slurry obtained by use of the same device and method as in Example 1 except for using 90.1 g (0.784 mole) of 3,3-dimethoxypropanenitrile was passed through a pressure filter device mounted with a filter cloth made of polypropylene with a gas permeation amount of 0.8 ml/cm² · sec without applying any cooling means, and under pressurization with nitrogen gas to 2.5 kg/cm² (gauge pressure), sodium salt of 2-hydroxymethylene-3,3-dimethoxypropanenitrile was separated. The crystals were dried in a vacuum dryer equipped with a condenser by dry ice-acetone bath cooling of a vacuum degree of 8000 Pa (60 Torr) and a temperature of 50°C to obtain 121.7 g of 2-hydroxymethylene-3,3-dimethoxypropanenitrile sodium salt and 31.7 g of the condensate (methyl formate: 87.4%). The sodium salt was obtained in a yield of 92.7% based on 3,3-dimethoxypropanenitrile. On the other hand, the filtrate containing 80.2% by weight of methyl formate was evaporated by a Claisen distillation device at the final temperature of 65°C to remove methyl formate. During the distillation operation, generation of gas which was considered to be formed by decomposition of methyl formate was observed, and formation of carbon monoxide was recognized. The methyl formate was distilled in an amount of 148.4 g, and the recovery combined with the methyl formate recovered during drying amounted to 88.1%. The residual solution in the flask was dark brown viscous material, and 1.4 g of 2-hydroxymethylene-3,3-dimethoxypropanenitrile was found to be contained therein, but it was unrecoverable because of the co-present impurities. Comparative example 3 The reaction mixture slurry obtained by use of the same device and method as in Example 1 except for using 91.2 g (0.793 mole) of 3,3-dimethoxypropanenitrile was charged into a jacketed stirring tank of one liter inner volume equipped with a Claisen type distillation device, a condenser and provided with a stirring blade made of a resin which contacts gently the inner wall, and methyl formate was evaporate by heating by passing hot water of 70°C through the jacket side. About 10 minutes after initiation of distilling out, formation of scale was observed on the inner wall of the tank, whereby heat transmission state, stirring state became bad to enable no stable drying, and drying was discontinued after one hour. Also, on the stirring shaft, crystals were attached in a mass, and they could be taken out in the crystal state out of the system with difficulty. Also, the brown matter hardly attached on the vessel wall contained a portion even difficultly soluble in methanol, which was apparently found to be deteriorated. According to the result of analysis by liquid chromatogram obtained by dissolving the whole amount in water, the 2-hydroxymethylene-3,3-dimethoxypropanenitrile sodium salt was obtained in an amount of 122.6 g, which corresponded to a yield of 93.7% based on 3,3-dimethoxypropanenitrile used for the reaction. According to the present invention, ALVM₂ can be produced substantially quantitatively with a yield of 98% or more. Also, according to the present invention, a reaction mixture slurry of ALVM₂ containing a large amount of methyl formate and unstable to heat can be obtained without contact with the outer air, and without deterioration of ALVM₂ and methyl formate with good slurry state, and at high yield.

Claims: 1. A process for producing a 2-hydroxymethylene-3,3-dialkoxypropanenitrile alkali metal salt represented by the formula: wherein R represents a lower alkyl group having 1 to 4 carbon atoms and M represents an alkali metal, which comprises reacting a 3,3-dialkoxypropanenitrile represented by the formula: (RO)₂CHCH₂CN wherein R is as defined above, with carbon monoxide, said reaction occuring at from 20 to 100°C in a 20 to 35 wt% C₁-C₄ lower alcoholic solution of an alkali metal C₁-C₄ lower alkoxide, the molar ratio of alkali metal C₁-C₄ lower alkoxide to 3,3-dialkoxypropanenitrile ranging from 1.0 to 1.3: 1, and the carbon monoxide being delivered into the system at from 2.0 to 9.8 MPa (20 to 100 kg/cm² (gauge pressure)). 2. The process according to Claim 1, wherein a lower alkyl formate by-product or the mixture of said lower alkyl formate with the C₁-C₄ lower alcohol is treated with a pyrolysis catalyst and the carbon monoxide generated is used as the starting material. 3. The process according to Claim 6, wherein said lower alkyl formate is methyl formate. 4. A process for obtaining a 2-hydroxymethylene-3,3-dialkoxypropanenitrile alkali metal salt-alcoholic slurry, which comprises adding a lower alcohol having 1 to 4 carbon atoms to a synthetic reaction mixture containing 2-hydroxymethylene-3,3-dialkoxypropanenitrile alkali metal salt represented by the formula: wherein R represents a lower alkyl group having 1 to 4 carbon atoms and M represents an alkali metal, and methyl formate and heating the mixture to 30 to 70°C, thereby taking methyl formate out of the system.

Inventors: FUJIKAWA, SHUZO C/O UBE CHEMICAL FACTORY, NISHIHIRA, KEIGO C/O UBE CHEMICAL FACTORY, YAMASHITA, MASAYOSHI C/O TOKYO MAIN OFFICE
Applicants: UBE INDUSTRIES, LTD.
Application year: 1988
Main classification: C07C255
IPC codes: C07C255, C07C253