Catalysts and processes for the conversion of succinates to citraconates or itaconates

A process for the preparation of citraconic anhydride which comprises:

• contacting a molar excess of an aqueous solution of formaldehyde, gaseous formaldehyde or trioxane in a solvent with at least one compound selected from the group consisting of succinic anhydride, mono- and di-lower alkyl esters of succinic acid in vapor phase with a metal oxide catalyst at a temperature from about 320° to 440° C., at a pressure from about 20 to 400 psi, at a Weight Hourly Space Velocity (WHSV) from about 0.3 to 4 kg succinate/hr*kg catalyst, the catalyst consisting of a porous material having a surface area between about 30 m2/g and 700 m2/g, surface acid site density from about 66 to 2350 micromole/g, surface base site density from about 0 to 500 micromole/g and acid strength (pKa) of about +3 to −3 until reaction is substantially complete and recovering from the reaction products the citraconic anhydride thereby produced, said lower alkyl having from 1 to 4 carbon atoms.