Using methacrolein and methanol as dehydration and absorption agents during production of methyl methacrylate

A method for producing methyl methacrylate, which comprises:

• (1) subjecting at least one starting material selected from the group consisting of isobutylene and tert-butanol to a gas phase catalytic oxidation reaction with molecular oxygen in the presence of a catalyst to thereby obtain gas (a) containing methacrolein gas and steam;
• (2) introducing said gas (a) and a liquid mixture (I) containing liquid methacrolein and liquid methanol into a dehydration tower at a lower portion thereof and at an upper portion thereof, respectively, thereby allowing said liquid mixture (I) to flow downwardly in said dehydration tower and contact countercurrently with said gas (a) in said dehydration tower, so that said liquid mixture (I) is gasified to thereby generate a gas mixture (I') containing methacrolein gas and methanol gas while causing the steam contained in said gas (a) to be condensed to thereby produce water,
• wherein the produced water is discharged from a bottom portion of said dehydration tower to thereby dehydrate said gas (a), while withdrawing the resultant dehydrated gas (a') containing the methacrolein gas, together with said gas mixture (I'), from an uppermost portion of said dehydration tower in the form of a dehydrated gas mixture (b) containing methacrolein gas and methanol gas;
• (3) introducing said dehydrated gas mixture (b) and a liquid mixture (II) containing liquid methacrolein and liquid methanol into an absorption tower at a lower portion thereof and at an upper portion thereof, respectively, thereby allowing said liquid mixture (II) to flow downwardly and contact countercurrently with said dehydrated gas mixture (b) in said absorption tower, wherein said liquid mixture (II) is introduced in an amount sufficient to absorb substantially all of the methacrolein gas and methanol gas which are contained in said dehydrated gas mixture (b), thus causing substantially all of said methacrolein gas and methanol gas of said dehydrated gas mixture (b) to be absorbed into said liquid mixture (II), to thereby obtain a liquid mixture (III) containing liquid methacrolein and liquid methanol, followed by withdrawal of said liquid mixture (III) from a bottom portion of said absorption tower;
• and
• (4) introducing the withdrawn liquid mixture (III) into an oxidative esterification reactor and subjecting the methacrolein and methanol, which are contained in said liquid mixture (III), to an oxidative esterification reaction in said reactor in the presence of molecular oxygen and in the presence of a palladium catalyst, to thereby produce methyl methacrylate in the form of a reaction mixture containing methyl methacrylate, water, methacrolein and methanol.