Maleic Anhydride → Dimethyl maleate

Participants

Reaction Steps

This example also refers to FIG. 1. A butane oxidation reactor (not shown) produces 100 moles per hour of maleic anhydride, of which 40 kmols are condensed by cooling the gases in condensers (not shown). The remaining 60 moles per hour are recovered as a 50 wt % aqueous solution of maleic acid from an absorber (2) in line 5 and mixed together with the crude maleic anhydride from the partial condensers (line 8). The aqueous maleic acid is fed to the mono-ester reaction column (9). Recycle methanol from the refining section is fed (line 16a) to the bottom of the column (9). More than 80% of the maleic acid is converted to mono-methyl maleate and the bottom product (line 17) contains less than 20 mol % water. Mainly water and methanol and a small amount of maleic acid in the overhead are fed (line 14) to the methanol column (25). The bottom product from the mono-ester reaction column (9) is fed to a reaction column (19) to react the mono-methyl maleate with methanol to produce di-methyl maleate. 300 moles per hour of methanol are fed (line 24) to the bottom of the reaction column (19). Essentially water free, fully converted di-methyl maleate is fed (line 26) to hydrogenation. Recycle methanol from the refining section is fed to the top of the reaction column as wash (line 16b) to minimise the di-methyl maleate and maleic acid in the overhead of the column. Methanol and water from the overhead (line 31) of the reaction column is fed to the methanol column (25) where the methanol is separated and recycled to the reaction column (line 24). Water and a small amount of recovered maleic acid and di-methyl maleate from the bottom of the methanol column are recycled to the absorber (2) in line 3. Thus in this arrangement the evaporator and the mono-ester reaction column duties are combined in a single unit which will reduce the equipment costs by eliminating the evaporation equipment.

Provenance & Evidence