Catalysts and processes for the conversion of succinates to citraconates or itaconates
AssigneeBoard of Trustees operating Michigan State University
InventorsDennis J. Miller, Dushyant Shekhawat, Kirthivasan Nagarajan, James E. Jackson
Life of this patent
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Abstract
Processes for producing citraconic anhydride and citraconic acid using porous materials with specific surface acidities and surface areas are described. The preferred catalyst is a porous gamma alumina. Itaconic acid is produced from citraconic acid. Itaconic acid is an intermediate to a variety of compounds including polymers.
Claims23
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.
A process for the preparation of formaldehyde, citraconic acid and succinic acid which comprises:
- (a) reacting a molar excess of formaldehyde with dimethyl succinate in vapor phase with a 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 at a temperature of 320° to 440° C. at a pressure of about 20 to 400 psi;
- (b) hydrolyzing the citraconic anhydride to citraconic acid and the dimethyl succinate to succinic acid at elevated temperatures in water so that the methanol is distilled from the reaction mixture;
- (c) oxidizing the methanol from step (b) to produce formaldehyde;
- and
- (d) separating the citraconic acid and succinic acid from the reaction mixture.
A process for the preparation of itaconic acid from citraconic acid which comprises:
- (a) isomerizing citraconic acid to itaconic acid in an aqueous solution at a first temperature of about 140° C. to 200° C., which produces citramalic acid and mesaconic acid as by-products;
- (b) crystallizing and separating the itaconic acid from the aqueous solution by cooling to a temperature between about 20° to 25° C.;
- and
- (c) heating the aqueous solution from step (b) to a temperature of 200° to 300° C. in the presence of a catalyst to convert a portion of the itaconic acid remaining in the aqueous solution and the by-products in the aqueous solution to citraconic acid;
- (d) recycling the citraconic acid solution of step (c) to step (a).
Dependencies are inferred from the claim text.