Process for Producing Methyl Methacrylate Verfahren Zur Herstellung Von Methylmethacrylat Procede Pour La Fabrication De Methacrylate De Methyle

Home , Acetone cyanohydrin, Methyl formate, Methyl methacrylate

~™ 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 monoxide 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- 2125 (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- 3<30 (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 3t35 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 4t40 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, st50 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 2t20 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. 2125 alkali metal alcolate or alkaline earth metal oxide is used In connection with catalysts for the gas phase cata- as a catalyst in the process of the present invention, the lytic reaction, Japanese Patent Application Laid-Open suitable amount of the catalyst used is 0.001 to 0.30 per No. 183654/1983 discloses a process in which a solid mol of methacrylic acid amide under conditions that the acid catalyst such as solid phosphate is used. This proc- reaction temperature is 20 to 1 00°C and the reaction time ess, however, has a disadvantage in that a large amount 3<30 is 0.5 to 6 hours. of methacrylic acid is by-produced. In the process of the Japanese Patent Application Laid-Open No. present invention, normally the nitrogen atoms are recy- 301 5/1 977 discloses that an alkali metal alcolate catalyst cled between amide and nitrile in the reaction system, is used in production of carboxylic acid ester from car- but undesirable by-production of methacrylic acid leads boxylic acid amide and alcohol. to taking nitrogen atoms out of the reaction cycle 3i35 This alcoholysis, however, has a disadvantage in whereby it becomes difficult to make the process advan- that the yield of carboxylic acid ester is low, as well as tageous from an economical standpoint. operational disadvantages in that the reaction tempera- According to the present invention, use of an amide ture must be as high as 200°C, high pressure is needed compound as a diluent in the dehydration reaction pre- and the intermittent release of the pressure in the reac- vents methacrylic acid as a by-product from forming and «40 tion system is required since ammonia is generated dur- permits production of the objective product with high ing the reaction. selectivity at a high conversion of the starting materials. On the contrary, in the process of the present inven- Amide compounds which can be used include dime- tion, when an esterification reaction by using methyl for- thyl formamide, dimethylacetamide, and N-methylpyrro- mate is carried out, the aforementioned disadvantages lidone. Of these compounds, N-methylpyrrolidone is 4145 can be all dissolved. particularly preferred. In the process of the present invention, the reaction In the process of the present invention, the reaction product is separated and recovered by an operation such of methacrylic acid amide and methyl formate, or the as distillation, and unreacted materials can be used reaction of methacrylic acid amide, methanol and carbon again as starting materials. monoxide for production of methyl methacrylate can be st50 Formamide by-produced along with the objective effectively carried out in the presence of a solvent and a methyl methacrylate is subjected to a dehydration reac- catalyst, although it proceeds only by heating a mixture tion to produce prussic acid. This prussic acid is sepa- of methacrylic acid amide and methyl formate in the rated and recovered, and then reintroduced to the absence of a catalyst. reactor for production of ACH. Since the above reaction is an equilibrium reaction, st In the process of the present invention, the reaction the yield of methyl methacrylate varies with the molar proceeds with high selectivity at each step, and thus ratio of methacrylic acid amide to methyl formate, or to methyl methacrylate can be produced with high selectiv- methanol and carbon monoxide. The molar ratio of meth- ity from acetone and methyl formate, or from acetone, acrylic acid amide to methyl formate, or to methanol and methanol and carbon monoxide. Moreover, undesirable

3 5 EP 0 406 676 B1 6 by-products, such as ammonium sulfate produced in the Step (III): Synthesis of methacrylic acid amide by dehy- conventional methods, are not formed at all, and thus the dration of a-hydroxyisobutyric acid amide process of the present invention is of high industrial value. 20.3 g of sodium hydroxide was dissolved in 100 ml The present invention is described in greater detail s of water, and 1 0. 1 g of magnesium oxide was suspended with reference to the following examples, although it is therein. To this suspension, 1 16.4 g of 85% phosphoric not limited thereto. acid was gradually poured and mixed. Then, the resulting mixture was heated while stirring to evaporate water, Example 1 thereby making it paste-like, and this paste was calcined 10 at 700°C for 1 2 hours. This calcined material was ground Step (I) : Synthesis of ACH from prussic acid and acetone to 10-16 mesh, and a 20 ml portion thereof was packed in a tubular reactor made of Pyrex glass with an inner 1 1 6 g of acetone and 1 ml of a 1 N aqueous sodium diameter of 1 8 mm. On the calcained material as packed hydroxide solution were placed in a 500-milliliter flask above, 1 0 ml of a porcelain Raschig ring with a diameter equipped with a stirrer, a thermometer, and a dropping 15 of 3 mm was placed to form an evaporation zone. While funnel for prussic acid, and 59.4 g of prussic acid was maintaining the reactor at 320°C and flowing nitrogen dropped thereto while maintaining the temperature in the gas from the top of the reactor at a rate of 10 ml/min, a flask at 20°C. After dropping of prussic acid was com- 30 wt% N-methylpyrrolidone solution of a-hydroxyisobu- pleted, the reaction was completed by maintaining the tyric acid amide obtained in the step (II) was supplied at mixture at 20°C for 2 hours. Then 50% sulfuric acid was 20 a rate of 10.5 g/hr. added thereto to adjust the reaction solution to pH 3. Reaction gas was collected by cooling with ice and The flask was connected to a vacuum system, and analyzed by a gas chromatography. unreacted prussic acid was distilled away to obtain 171 The conversion of the a-hydroxyisobutyric acid g of ACH. amide as starting material was 95.8%, and the yield of The purity of ACH was 98.4%, and the yield of ACH 25 methacrylic acid amide based on the converted starting based on acetone was 99%. material was 81.6 mol %. In addition, 10% of acetone and 4% of acetonitrile were formed, and no methacrylic Step (II): Synthesis of a-hydroxyisobutyric acid amide by acid was detected. hydration of ACH 600 g of the reaction solution was distilled under 30 reduced pressure to obtain 1 1 3 g of methacrylamide with 63.2 g of potassium permanganate and 500 g of a purity of not less than 98% as a main component. water were placed in a 1 -liter flask equipped with a stirrer, a reflux condenser and a thermometer, and stirred while Step (IV): Synthesis of methyl methacrylate and forma- heating at 70°C. Then, 240 g of an aqueous solution con- mide from methacrylic acid amide and methyl formate taining 96.2 g of manganese sulfate and 40 g of 15% 35 sulfuric acid were added thereto, and reacted at 70°C for 85.6 g of methacrylic acid amide obtained in the step 3 hours. (III), 180 g of methyl formate, 96 g of methanol, and 1.1 The contents in the flask were cooled, and then a g of sodium methylate were placed in a 1 -liter stainless resulting precipitate was suction filtered and washed with steel autoclave equipped with a stirrer, and reacted by 2.4 L (L=liter) of water. The precipitated cake was dried 40 heating at 60°C for 2 hours while stirring. at 60°C overnight to obtain 74 g of active manganese The reaction product was cooled, and analyzed by dioxide, which was used as a catalyst in the subsequent gas chromatography. This analysis showed that the con- step. version of methacrylic acid amide was 94%, the selec- 1 50 g of ACH obtained in the step (I), 350 g of water, tivity of methyl methacrylate based on methacrylic acid 1 00 g of acetone, and 60 g of manganese dioxide were 45 amide was 91%, and the selectivity of formamide was placed in a 1 -liter flask equipped with a stirrer, a reflux 98%. In addition, methyl a-methoxyisobutyrate was condenser and a thermometer, and reacted by heating obtained in a yield of 8%. at 60°C for 5 hours while stirring. After neutralization of sodium methylate in the reac- The reaction solution was cooled with ice, and then tion solution with hydrochloric acid, distillation was con- the catalyst was removed by suction filtration. A gas so ducted by the usual method to recover methyl formate, chromatographic analysis of the filtrate showed that the methanol and methacrylic acid amide, and at the same conversion of ACH was 99.5%, the yield of u-hydrox- time, 79 g of methyl methacrylate with a purity of 99% yisobutyric acid amide was 95%, and small amounts of and 40 g of formamide with a purity of 99% were acetone and formamide were contained. obtained. The above filtrate was distilled under reduced pres- 55 sure to obtain 155 g of a-hydroxyisobutyric acid amide with a purity of not less than 99.5% as a main component.

4 7 EP 0 406 676 B1 8

Step (V): Production of prussic acid by dehydration of (I) a step of reacting prussic acid and acetone formamide to form acetonecyanohydrin; (II) a step of hydrating the acetonecyanohydrin 30 ml of a spherical a-alumina catalyst (calcined at obtained in the step (I) to form a-hydroxyisobu- 1 ,500°C for 2 hours) with a diameter of 2 mm was packed 5 tyric acid amide; in a SUS 316 reactor with an inner diameter of 18 mm, (III) a step of dehydrating the a-hydroxyisobu- and a small amount of dilution nitrogen gas and forma- tyric acid amide obtained in the step (II) to form mide obtained in the step (IV) were continuously sup- methacrylic acid amide; plied under conditions that the pressure was 10665.76 (IV) a step of reacting the methacrylic acid Pa (80 Torr), the temperature was 450 to 500°C, and the 10 amide obtained in the step (III) and methyl for- contact time was 0.1 second. The reaction was contin- mate to form methyl methacrylate and forma- ued for 10 hours. Non-condensed gas was introduced mide; and into a gas washing container containing water to make (V) a step of dehydrating formamide separated prussic acid accompanied absorbed therein. from the product obtained in the step (IV) to form The condensed solution and the absorbing solution 15 prussic acid and recycling said prussic acid as were analyzed. This analysis showed that the conversion a starting material in the step (I). of formamide was 98%, and the yield of prussic acid based on formamide was 92%. 2. A process for producing methyl methacrylate which Upon distillation of the product, high purity prussic comprises: acid was obtained. This prussic acid was recycled as a 20 starting material for production of ACH. (I) a step of reacting prussic acid and acetone to form acetonecyanohydrin; Comparative Example 1 (II) a step of hydrating the acetonecyanohydrin obtained in the step (I) to form a-hydroxyisobu- At the step (III) of Example 1 , the reaction was car- 25 tyric acid amide; ried out in the same manner as in Example 1 except that (III) a step of dehydrating the a-hydroxyisobu- an aqueous solution was used in place of the N-methyl- tyric acid amide obtained in the step (II) to form pyrrolidone solution. As a result, the conversion of the a- methacrylic acid amide; hydroxyisobutyric acid amide as starting material was (IV) a step of reacting the methacrylic acid 98.6%, and the yield of methacrylic acid amide based on 30 amide obtained in the step (III) with methanol the converted starting material was 41 .8 mol %. In addi- and carbon monoxide to form methyl methacr- tion, 32% of methacrylic acid, 10% of acetone, and 8% ylate and formamide; and of methacrylonitrile were formed. (V) a step of dehydrating formamide separated from the product obtained in the step (IV) to form Example 2 35 prussic acid and recycling said prussic acid as a starting material in the step (I). At the step (IV) of Example 1 , 200 g of methanol was supplied in place of 1 80 g of methyl formate and 96 g of 3. The process as claimed in Claim 1 or 2, wherein the methanol, and carbon monoxide was introduced under reaction of prussic acid and acetone in the step (I) a pressure of 40520 hPa (40 atm). The reaction was car- 40 is carried out in the presence of a basic catalyst. ried out by heating while stirring. When the temperature in the autoclave reached 4. The process as claimed in Claim 1 or 2, wherein the 60°C, carbon monoxide was introduced so as to maintain hydration of acetonecyanhydrin in the step (II) is car- the reaction pressure at 40520 hPa (40 atm), and the ried out in the presence of a catalyst selected from reaction was further continued for 3 hours. 45 manganese, copper, nickel or oxide thereof. Then, the temperature in the autoclave was lowered to 10°C by cooling, and the pressure was gradually 5. The process as claimed in Claim 1 or 2, wherein the decreased to atmospheric pressure. Thereafter the reac- dehydration of a-hydroxyisobutyric acid amide in the tion product was taken out and analyzed by gas chroma- step (III) is carried out in a gas phase using an amide tography. This analysis showed that the conversion of so compound as a diluting agent. methacrylic acid amide was 87%. The selectivity of methyl methacrylate, and the 6. The process as claimed in Claim 5, wherein the selectivity of formamide both based on mehtacrylic acid amide compound is N-methylpyrrolidone. amide were 95% and 94%, respectively. 55 7. The process as claimed in Claim 1, wherein the Claims reaction of mehtacrylic acid amide and methyl formate in the step (IV) is carried out in a solvent and 1 . A process for producing methyl methacrylate which in the presence of a catalyst. comprises:

5 9 EP 0 406 676 B1 10

8. The process as claimed in Claim 2, wherein the (III) einen Schritt der Dehydratisierung des in reaction of methacrylic acid amide with methanol Schritt (II) erhaltenen a-Hydroxyisobuttersaure- and carbon monoxide is carried out in a solvent and amids zur Bildung von Methylacrylsaureamid; in the presence of a catalyst. (IV) einen Schritt des Reagierens des in Schritt 5 (III) erhaltenen Methacrylsaureamids mit 9. The process as claimed in Claim 1, wherein the Methanol und Kohlenmonoxid zur Bildung von molar ratio of methacrylic acid amide to methyl for- Methylmethacrylat und Formamid; und mate is 1:1 to 10:1. (V) einen Schritt der Dehytratisierung des von dem in Schritt (IV) erhaltenen Produktes abge- 10. The process as claimed in Claim 2, wherein the 10 trennten Formamids zur Bildung von Blausaure molar ratio of methacrylic acid amide to methanol und deren Wiederverwertung als Ausgangsma- and carbon monoxide is 1:1 to 10:1 . terial in dem Schritt (I).

1 1 . The process as claimed in Claim 7, wherein the cat- 3. Verfahren nach Anspruch 1 oder 2, wobei die Reak- alyst is alkali metal alcolate or alkaline earth metal 15 tion von Blausaure und Aceton in dem Schritt (I) in oxide. Gegenwart eines basischen Katalysators durchge- ftihrt wird. 12. The process as claimed in Claim 11, wherein the alkali metal alcolate is sodium methylate, sodium 4. Verfahren nach Anspruch 1 oder 2, wobei die Hydra- ethylate, sodium butyrate, potassium methylate, 20 tisierung von Acetoncyanhydrin in dem Schritt (II) in potassium ethylate, or potassium butyrate. Gegenwart eines Katalysators durchgefiihrt wird, der aus Mangan, Kupfer, Nickel oder deren Oxide 13. The process as claimed in Claim 11, wherein the ausgewahlt ist. alkaline earth metal oxide is magnesium oxide, calcium oxide, or barium oxide. 25 5. Verfahren nach Anspruch 1 oder 2, wobei die Dehy- dratisierung von a-Hydroxyisobuttersaureamid in Patentanspruche dem Schritt (III) in einer Gasphase durchgefiihrt wird, wobei eine Amidverbindung als Verdiinnungs- 1. Verfahren zur Herstellung von Methylmethacrylat, mittel verwendet wird. das folgende Schritte aufweist: 30 6. Verfahren nach Anspruch 5, wobei die Amidverbin- (I) einen Schritt des Reagierens von Blausaure dung N-Methylpyrrolidon ist. und Aceton zur Bildung von Acetoncyanhydrin; (II) einen Schritt der Hydratisierung des in 7. Verfahren nach Anspruch 1 , wobei die Reaktion von Schritt (I) erhaltenen Acetoncyanhydrins zur Bil- 35 Methacrylsaureamid und Methylformiat in dem dung von a-Hydroxyisobuttersaureamid; Schritt (IV) in einem Losungsmittel und in Gegen- (III) einen Schritt der Dehydratisierung des in wart eines Katalysators durchgefiihrt wird. Schritt (II) erhaltenen a-Hydroxyisobuttersaure- amids zur Bildung von Methacrylsaureamid; 8. Verfahren nach Anspruch 2, wobei die Reaktion von (IV) einen Schritt des Reagierens des in Schritt 40 Methacrylsaureamid mit Methanol und Kohlenmon- (III) erhaltenen Methacrylsaureamids mit oxid in einem Losungsmittel und in Gegenwart eines Methylformiat zur Bildung von Methylmethacry- Katalysators durchgefiihrt wird. lat und Formamid; und (V) einen Schritt der Dehydratisierung des von 9. Verfahren nach Anspruch 1 , wobei das molare Ver- dem im Schritt (IV) erhaltenen Produkts abge- 45 haltnis von Methacrylsaureamid zu Methylformiat trennten Formamids zur Bildung von Blausaure 1:1 bis 10:1 betragt. und deren Wiederverwertung als Ausgangsma- terial in Schritt (I). 10. Verfahren nach Anspruch 2, wobei das molare Ver- haltnis von Methacrylsaureamid zu Methanol oder 2. Verfahren zur Herstellung von Methylmethacrylat, so Kohlenmonoxid 1:1 bis 10:1 betragt. das folgende Schritte aufweist: 1 1 . Verfahren nach Anspruch 7, wobei der Katalysator (I) einen Schritt des Reagierens von Blausaure ein Alkalimetallalkoholat oder ein Erdalkalimetallo- und Aceton zur Bildung von Acetoncyanhydrin; xid ist. (II) einen Schritt der Hydratisierung des in 55 Schritt (I) erhaltenen Acetoncyanhydrins zur Bil- 1 2. Verfahren nach Anspruch 1 1 , wobei das Alkalime- dung von a-Hydroxyisobuttersaureamid; tallalkoholat Natriummethylat, Natriumethylat, Natri- umbutyrat, Kaliummethylat, Kaliumethylat oder Kaliumbutyrat ist.

6 11 EP 0 406 676 B1 12

1 3. Verfahren nach Anspruch 1 1 , wobei das Erdalkali- 4. Procede selon la revendication 1 ou 2, dans lequel metalloxid Magnesiumoxid, Calciumoxid oder Bari- on effectue I'hydratation de la cyanhydrine de I'ace- umoxid ist. tone dans I'etape (II) en presence d'un catalyseur choisi parmi le manganese, le cuivre, le nickel ou un Revendications s oxyde de ceux-ci.

1. Procede pour la production de methacrylate de 5. Procede selon la revendication 1 ou 2, dans lequel methyle qui comprend: on effectue la deshydratation d'un amide d'acide a- hydroxyisobutyrique dans I'etape (III) en phase (I) une etape consistant a faire reagir de I'acide 10 gazeuse en utilisant un amide en tant qu'agent prussique et de I'acetone af in de former la cyan- diluant. hydrine de I'acetone; (II) une etape consistant a hydrater la cyanhy- 6. Procede selon la revendication 5, dans lequel le drine de I'acetone obtenue dans I'etape (I) afin compose amide est la N-methylpyrrolidone. de former un amide d'acide a-hydroxyisobutyri- is que; 7. Procede selon la revendication 1, dans lequel on (III) une etape consistant a deshydrater I'amide effectue la reaction de I'amide d'acide methacrylique d'acide a-hydroxyisobutyrique obtenue dans et le formiate de methyle dans I'etape (IV) dans un I'etape (II) afin de former un amide d'acide solvant et en presence d'un catalyseur. methacrylique; 20 (IV) une etape consistant a faire reagir I'amide 8. Procede selon la revendication 2, dans lequel on d'acide methacrylique obtenue dans I'etape (III) effectue la reaction de I'amide d'acide methacrylique et du formiate de methyle afin de former du avec du methanol et du monoxyde de carbone dans methacrylate de methyle et du formamide; et un solvant et en presence d'un catalyseur. (V) une etape consistant a deshydrater le for- 25 mamide separe a partir du produit obtenu dans 9. Procede selon la revendication 1 , dans lequel le rap- I'etape (IV) afin de former de I'acide prussique port molaire de I'amide d'acide methacrylique au for- et a recycler ledit acide prussique en tant que miate de methyle est compris entre 1:1 et 10:1 . matiere premiere dans I'etape (I). 30 1 0. Procede selon la revendication 2, dans lequel le rap- 2. Procede pour la production de methacrylate de port molaire de I'amide d'acide methacrylique au methyle qui comprend: methanol ou au monoxyde de carbone est compris entre 1:1 et 10:1. (I) une etape consistant a faire reagir de I'acide prussique et de I'acetone afin de former la cyan- 35 11. Procede selon la revendication 7, dans lequel le hydrine de I'acetone; catalyseur est un alcoolate de metal alcalin ou un (II) une etape consistant a hydrater la cyanhy- oxyde de metal alcalino-terreux. drine de I'acetone obtenue dans I'etape (I) afin de former un amide d'acide a-hydroxyisobutyri- 12. Procede selon la revendication 11, dans lequel que; 40 I'alcoolate de metal alcalin est le methylate de (III) une etape consistant a deshydrater I'amide sodium, I'ethylate de sodium, le butyrate de sodium, d'acide a-hydroxyisobutyrique obtenue dans le methylate de potassium, I'ethylate de potassium I'etape (II) afin de former un amide d'acide ou le butyrate de potassium. methacrylique; (IV) une etape consistant a faire reagir I'amide 45 13. Procede selon la revendication 11, dans lequel d'acide methacrylique obtenue dans I'etape (III) I'oxyde de metal alcalino-terreux est I'oxyde de avec du methanol et du monoxyde de carbone magnesium, I'oxyde de calcium ou I'oxyde de afin de former du methacrylate de methyle et du baryum. formamide; et (V) une etape consistant a deshydrater le for- so mamide separe a partir du produit obtenu dans I'etape (IV) afin de former de I'acide prussique et a recycler ledit acide prussique en tant que matiere premiere dans I'etape (I). 55 3. Procede selon la revendication 1 ou 2, dans lequel on effectue la reaction de I'acide prussique et de I'acetone dans I'etape (I) en presence d'un catalyseur basique.