Röhm GmbH

A process can be used for preparing methyl methacrylate by direct oxidative esterification of methacrolein. Methyl methacrylate is used in large amounts for preparing polymers and copolymers with other polymerizable compounds. In addition, methyl methacrylate is an important synthesis unit for a variety of specialty esters based on methacrylic acid (MAA) which can be prepared by transesterification with the appropriate alcohol. There is consequently a great interest in very simple, economic and environmentally friendly processes for preparing this starting material. A corresponding optimized workup of the reactor output from the oxidative esterification of methacrolein, through which unconverted methacrolein (MAL) can be recycled very efficiently, is useful. In addition, the process can be carried out in a manner which compared to known variants is markedly more energy- and water-saving.

A process for producing alkyl methacrylates, in particular methyl methacrylate (MMA), includes production of methacrolein (MAL) in a first reaction stage; direct oxidative esterification (DOE) of the methacrolein with an alcohol, preferably methanol, to afford an alkyl methacrylate in a second reaction stage; and workup of the alkyl methacrylate crude product from the second reaction stage. An optimized workup of the reactor output from the oxidative esterification of methacrolein involves minimizing the amount of employed water, the amount of employed acid, and/or the amount of aqueous waste streams, through an optimized recycling of the generated process water streams.

A continuous process can be used for preparing methacrylic acid by catalytic hydrolysis of methyl methacrylate that has been prepared proceeding from C-2, C-3, or C-4 raw materials. In this process, methyl methacrylate of high purity is reacted with water in the presence of a Brønsted catalyst to give a reaction mixture containing the reactants and products and worked up in a distillation column. In the distillation column, a condensate containing an azeotrope of MMA with methanol is produced at the top, a vapour condensate containing methacrylic acid of high purity is produced in the middle part of the column, and a substance mixture containing high-boiling by-products and a small amount of methacrylic acid is obtained in the bottom of the column.

A novel process can be used for a heterogeneously catalysed oxidation reaction, in the presence of a pulverulent noble metal-containing catalyst, where (meth)acrolein, an alkyl alcohol, in particular methanol, and an oxygen-containing gas are converted to an alkyl (meth)acrylate, in particular methyl (meth)acrylate. A corresponding reactor suitable for performing the reaction is also useful. The process allows for an effective retention of the particulate catalyst and the continuous discharge of fines fractions of the catalyst powder which are present, particularly in a fresh catalyst batch as a consequence of its preparation. Such fines fractions may also be produced by abrasion during the reaction. The process allows for effective recycling, recovery, and utilization of these discharged catalyst fractions.

An improved process for synthesizing alkyl methacrylates, in particular methyl methacrylate (MMA), involves reacting acetone cyanohydrin (ACH) and sulfuric acid in a first reaction stage (amidation). The process then involves heating the first reaction mixture in a second reaction stage (conversion) such that methacrylamide (MAA) is obtained; and then esterifying methacrylamide (MAA) with alcohol and water, preferably methanol and water, in a third reaction stage such that alkyl methacrylate is formed. The sulfuric acid used has a concentration of 98.0 wt % to 100.0 wt %. A subsequent working up of the third reaction mixture involves least two distillations in which the byproducts methacrylonitrile (MeAN) and acetone are obtained as an aqueous heteroazeotrope at least in part in the top fraction. At least some of the aqueous heteroazeotrope is removed from the process and at least partially reintroduced into the third reaction stage.

A process for preparing methyl methacrylate (MMA) and/or methacrylic acid (MAS) having improved yield, involves amidation, conversion, and hydrolysis/esterification. Especially high yields are obtained during the amidation and in the subsequent so-called conversion.

A novel process can be used for preparing methacrylates, such as methacrylic acid and/or alkyl methacrylates, especially MMA. The process allows for prolonging of the catalyst service life and an increase in efficiency of the methacrylate preparation based on C2 or C4 raw materials, especially when proceeding from isobutylene or tort-butanol or ethylene as raw material. The process allows for performance for longer periods without disruption, with constant or even increased activities and selectivities. This gives rise to the possibility of performing such processes in a very simple, economically viable, and environmentally benign manner. In addition, it has been possible to minimize known safety risks that emanate from the methacrolein intermediate.

A process produces methyl methacrylate by direct oxidative esterification of methacrolein. Methyl methacrylate is used in large amounts for producing polymers and copolymers with other polymerizable compounds. An optimized workup of the reactor discharge from the oxidative esterification of methacrolein allows for co-discharged fine catalyst particles to be very efficiently separated and optionally removed or recycled. In addition, this process can reduce the formation of byproducts in extended continuous operation compared to known variant. A reactor system contains stirrer configurations which allow virtually abrasion-free operation and thus a catalyst on-stream time of several years.

A process for producing alkyl methacrylates, in particular methyl methacrylate (MMA), includes production of methacrolein (MAL) in a first reaction stage; direct oxidative esterification (DOE) of the methacrolein with an alcohol, preferably methanol, to afford an alkyl methacrylate in a second reaction stage: and workup of the alkyl methacrylate crude product from the second reaction stage. An optimized workup of the reactor output from the oxidative esterification of methacrolein involves minimizing the amount of employed water, the amount of employed acid, and/or the amount of aqueous waste streams, through an optimized recycling of the generated process water streams.

A process for producing alkyl methacrylates, in particular methyl methacrylate (MMA), includes production of methacrolein (MAL) in a first reaction stage; direct oxidative esterification (DOE) of the methacrolein with an alcohol, preferably methanol, to afford an alkyl methacrylate in a second reaction stage; and workup of the alkyl methacrylate crude product from the second reaction stage. An optimized workup of the reactor output from the oxidative esterification of methacrolein involves minimizing the amount of employed water, the amount of employed acid, and/or the amount of aqueous waste streams, through an optimized recycling of the generated process water streams.