~™ II 1 1 III II II 1 1 II II I Ml II I II I II (19) J European Patent Office Office europeen des brevets (11) EP 0 406 676 B1 (12) EUROPEAN PATENT SPECIFICATION (45) Date of publicationation and mention (51 ) |nt. CI.6: C07C 69/54, C07C 67/20 of the grant of the patent: 27.03.1996 Bulletin 1996/13 (21) Application number: 90112194.7 (22) Date of filing: 27.06.1990 (54) Process for producing methyl methacrylate Verfahren zur Herstellung von Methylmethacrylat Procede pour la fabrication de methacrylate de methyle (84) Designated Contracting States: • Ebata, Shuji, DE ES FR GB IT NL C/o Mitsubishi Gas Chem. Com. Tayuhama, Niigata-shi, Niigata-ken (JP) (30) Priority: 04.07.1989 JP 171190/89 (74) Representative: Turk, Gille, Hrabal, Leifert (43) Date of publication of application: Brucknerstrasse 20 09.01.1991 Bulletin 1991/02 D-40593 Dusseldorf (DE) (73) Proprietor: MITSUBISHI GAS CHEMICAL (56) References cited: COMPANY, INC. DE-A- 3 436 608 Chiyoda-ku, Tokyo (JP) • PATENT ABSTRACTS OF JAPAN vol. 14, no. 68 (72) Inventors: (C- 686)(401 1 ), 8 February 1 990; & JP-A-1 290653 • Higuchi, Hirofumi, (MITSUBISHI GAS CHEM) 22.11. 1989 C/o Mitsubishi Gas Chem. Com. Tayuhama, Niigata-shi, Niigata-ken (JP) Remarks: • Kida, Koichi, The file contains technical information submitted C/o Mitsubishi Gas Chem. Com. after the application was filed and not included in this Tayuhama, Niigata-shi, Niigata-ken (JP) specification CO CO CO o Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in o a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. Q_ 99(1) European Patent Convention). LU Printed by Rank Xerox (UK) Business Services 2.9.16/3.4 1 EP 0 406 676 B1 2 Description (4) the step of dehydrating the compound obtained in step (3), i. e. the a-hydroxyisobutyric acid amide 1 . Field of the Invention is first reacted with methyl formate or with methanol and carbon monoxide to formamide and methyl a- The present invention relates to a novel process for s hydroxyisobutyrate which is then dehydrated to the producing methyl methacrylate from acetone and methyl target compound methyl methacrylate. formate, or from acetone, methanol and carbon monox- ide as starting materials. SUMMARY OF THE INVENTION A large amount of methyl methacrylate is used as a starting material for production of various polymers and u An object of the present invention is to provide a the methyl methacrylate is a greatly important interme- novel process for production of methyl methacrylate from diate in industrial use. starting materials easily available and in stable supply. Another object of the present invention is to provide 2. Description of Related Arts a process for production of methyl methacrylate with sim- H15 ple operations at low cost. For production of methyl methacrylate on a commer- Still another object of the present invention is to pro- cial scale, an acetone cyanohydrin method in which vide a process for production of methyl methacrylate in prussic acid and acetone are used as starting materials, which starting materials can circulate by regeneration and methyl methacrylate is produced through acetone during reactions. cyanohydrin (hereinafter referred to as "ACH") formed 2t20 The present invention relates to a process for pro- from the starting materials, and a C4 oxidation method ducing methyl methacrylate which comprises: in which isobutylene or tert-butanol is used as a starting material have been put into practical use. (I) a step of reacting prussic acid and acetone to In addition, it has been proposed that methyl meth- form acetone cyanohydrin (ACH); acrylate can be produced by an oxidation-dehydrogena- 2521 (II) a step of hydrating ACH obtained in the above tion of isobutyric acid, or a condensation-dehydration of step (I) to form a-hydroxyisobutyric acid amide; propionic acid or propion aldehyde and formaldehyde. (III) a step of dehydrating a-hydroxyisobutyric acid But, these methods have not been put into practice. amide obtained in the above step (II) to form meth- In accordance with the ACH method, ACH is synthe- acrylic acid amide; sized from prussic acid and acetone, and then the result- 303< (IV) a step of reacting methacrylic acid amide ing ACH is reacted with methanol in the presence of an obtained in the above step (III) with methyl formate excess amount of concentrated sulfuric acid to produce or with methanol and carbon monoxide to form methyl methacrylate. This ACH method is widely carried methyl methacrylate and formamide; and out now, because the reaction proceeds easily with high (V) a step of dehydrating formamide separated from yields. The ACH method, however, has disadvantages in 353t the product obtained in the above step (IV) to form that large amounts of waste sulfuric acid and ammonium prussic acid and recycling the prussic acid as a sulfate are by-produced and the treatment thereof regenerated starting material in the step (I). increases production costs of methyl methacrylate. Also the C4 method has disadvantages in that a DESCRIPTION OF PREFERRED EMBODIMENTS number of side reactions are caused, the yield of methyl 404t methacrylate is low, purification costs are high, the oper- The process of the present invention eventually ations are complicated, and an expensive reactor is employs acetone and methyl formate, or acetone, meth- required. In addition, isobutylene and tert-butanol to be anol and carbon monoxid as starting materials. Although used as starting materials are not easily available. the process of the present invention produces the objec- DE-A-3 436 608 discloses a process for the produc- 45« tive methyl methacrylate through ACH, it is not accom- tion of methyl methacrylate comprising the following panied by by-production of ammonium sulfate at all steps: unlike the conventional ACH method. Acetone is formed as a by-product in large amounts (1) The step of reacting acetone and prussic acid to and at low cost in production of phenol by a cumene form acetone cyanohydrin, 50st method. If necessary, it can easily be produced from pro- pylene. (2) the step of hydrating acetone cyanohydrin to form Methyl formate can easily be produced through car- a-hydroxyisobutyric acid amide, bonylation or dehydrogenation of methanol which is commercially available in large amounts and at low cost. (3) the step of reacting the amide with methyl for- st In the process of the present invention, ACH is pro- mate or with methanol and carbon monoxide to form duced by reacting prussic acid and acetone by the con- methyl a-hydroxyisobutyrate and formamide, and ventional methods. More specifically, ACH can be produced in a high yield by reacting prussic acid and ace- 2 3 EP 0 406 676 B1 4 tone at a temperature as low as about 1 0°C in the pres- carbon moxide is preferably 1:1 to 10:1 and more pref- ence of a basic catalyst such as alkalis or amines. erably 2:1 to 5:1. a-Hydroxyisobutyric acid amide is produced by Addition of a solvent is effective in increasing the sol- reacting ACH and water in the presence of a catalyst. As ubility of solid methacrylic acid amide, and the selectivity such catalysts, those effective for the hydration reaction s of the reaction. As the solvent to be used, methanol is of nitriles can be used. Although strong acids such as most preferable, and the molar ratio of methanol to meth- sulfuric acid can be used, metal or metal oxide catalysts acrylic acid amide is preferably 2:1 to 10:1 . are desirable from an economical standpoint including Known catalysts to be used in the above reaction post-treatment. More specifically, manganese, copper, include inorganic acids, organic acids, alkalis, and their nickel and their oxides are effective, with manganese n salts as described in Japanese Patent Application Laid- oxide being particularly preferred. Open Nos. 55444/1983 and 78937/1985. However, The weight ratio of ACH to water is suitable to be in when these known catalysts are used, both the rate of a range of 10:90 to 90:10. In the reaction system, a sol- reaction and selectivity are insufficiently low. vent such as acetone or methanol can be also present. Alkali metal alcolate and alakaline earth metal oxide When manganese oxide is used as a catalyst, the reac- n15 are excellent as catalysts for use in the above reaction. tion temperature is preferably 20 to 1 50°C and more pref- Representative examples of the alkali metal alcolate erably 40 to 1 00°C. The reaction time is preferably 0.3 to to be used as a catalyst in the process of the present 6 hours and more preferably 0.5 to 3 hours. The reaction invention are methylate, ethylate and butyrate of sodium can be carried out batchwise or continuously. and potassium. They can be prepared from metallic lith- Although production of methacrylic acid amide by a 202t ium, sodium or potassium and lower alcohol. dehydration reaction of a-hydroxyisobutyric acid amide The alkaline earth metal oxide to be used as a cat- can be carried out by a liquid phase reaction using, for alyst in the process of the present invention includes example, sulfuric acid or phosphoric acid, it can be car- magnesium oxide, calcium oxide, and barium oxide. ried out more effectively by a gas phase reaction using In connection with reaction conditions, when the a solid catalyst.