Methyl Methacrylate Production from Isobutylene

The process under analysis comprises 4 major sections: (1) Methacrylic acid (MAA) synthesis; (2) MAA Purification; (3) Methyl methacrylate (MMA) production; and (4) MMA purification.

MAA Synthesis. Initially, heated isobutylene is oxidized with air to methacrolein in the presence of a multicomponent oxide catalyst of Mo-Bi. The yield of methacrolein reaches over 80%. In addition to methacrolein, other oxygenated compounds by-products are formed. Then, the effluent is directly fed with air to another reactor, where methacrolein is oxidized to methacrylic acid with P-Mo heteropoly acid solution as catalyst.

MAA Purification. The effluent from MAA synthesis is directed to a quencher where most of the MAA condenses. The aqueous solution is routed to a solvent extraction unit, where the methacrylic acid is concentrated by extraction into dibutyl ketone organic solvent. The organic solution then fed to a column where it is dehydrated, yielding crude MAA, which is fed to a vacuum distillation column to obtain acetic acid as by-product.

MMA Production. MAA is fed with methanol to a reactive distillation column, where the esterification reaction takes place.The reaction occurs in the liquid phase, in the presence of an ion exchange resin as catalyst. Besides MMA, small amounts of by-products are formed. Heavy compounds withdrawn in column bottom are burned for fuel.

MMA Purification. The overhead stream of the reactor is fed to an extractor where it is contacted with water, in such a way that unreacted methanol is removed. A column strippes off water and low boiling impurities from the crude ester produced. Finally, components heavier than MMA are removed from the MMA stream in a rectifier. The column overhead vapor, consisting of high-purity MMA, is condensed and sent to storage.