Patent ID: 8338636

Claim:
A process for making dialkyl succinate, comprising: a. providing a mixture comprising about 30 to 90 wt % maleic anhydride and about 5 to 68 wt % fumaric acid; b. contacting the mixture of (a) with an alkyl alcohol solvent in sufficient amount to form a solution and holding the solution at a temperature of from about 20° C. to about 250° C. for a holding time; c. hydrogenating the solution of (b), in the absence of an intermediate distillation between (b) and (c), at hydrogenation conditions of temperature from about 50 to 200° C. under hydrogen pressure from about 50 to 1000 psig (about 450 to 7000 kPa) in the presence of a hydrogenation catalyst to form a hydrogenation product; d. treating the hydrogenation product with alcohol at an esterification temperature of about 100° C. to 140° C. to form crude product containing dialkyl esters, wherein at least 85 percent of maleic anhydride, fumaric acid and their derivatives of (a) have been converted to dialkyl esters in the crude product; and e. isolating dialkyl succinate from the crude product of (d).