Process for preparing methacrylic acid
View Patent ↗The present invention relates to a process for preparing methacrylic acid based on the hydrolysis of methacrylic esters.
1. A process for preparing methacrylic acid, the process comprising:
converting acetone cyanohydrin to methacrylamide;
esterifying the methacrylamide in the presence of at least one alcohol, thereby obtaining at least one methacrylic ester; and
hydrolyzing the at least one methacrylic ester in the presence of at least one heterogeneous catalyst, thereby obtaining methacrylic acid,
wherein:
a feed stream to the hydrolyzing comprises a water stream, and a methacrylic ester stream from the esterifying;
a recirculation stream to the hydrolyzing comprises a first circulation stream from the input of a vacuum rectifying column for low boiler removal, and a second circulation stream from the output of a rectifying column for alcohol removal; and
the mass ratio or the volume ratio of the recirculation stream to the feed stream ranges from 5-50.
2. The process according to claim 1 , wherein the at least one heterogeneous catalyst is selected from the group consisting of a zeolite, an ion exchange resin, and an amorphous acid catalyst.
3. The process according to claim 1 , wherein, during the hydrolyzing, the flow through a catalyst bed is from bottom or from top.
4. The process according to claim 1 , wherein the hydrolyzing occurs at a temperature of 50-200° C.
5. The process according to claim 1 , wherein the hydrolyzing occurs at an elevated pressure.
6. The process according to claim 1 , wherein the ratio of the at least one methacrylic ester to water in the hydrolyzing is between 0.5 and 5.
7. The process according to claim 1 , wherein the residence time during the hydrolyzing is 10-120 min.
8. The process according to claim 1 , wherein the mass ratio or the volume ratio of the recirculation stream to the feed stream ranges from 15 to 30.
9. The process according to claim 1 , wherein a methanol/methyl methacrylate mixture is supplied during said esterifying.
10. The process according to claim 1 , wherein the hydrolyzing occurs at a temperature of 70-150° C.
11. The process according to claim 1 , wherein the hydrolyzing occurs at a temperature of 90-120° C.
12. The process according to claim 1 , wherein the hydrolyzing occurs at a temperature of 100-110° C.
13. The process according to claim 1 , wherein the hydrolyzing occurs at an elevated pressure of from 0.1 to 9 bar gauge.
14. The process according to claim 1 , wherein the hydrolyzing occurs at an elevated pressure of from 2 to 4 bar gauge.
15. The process according to claim 1 , wherein the ratio of the at least one methacrylic ester to water in the hydrolyzing is between 1 and 4.
16. The process according to claim 1 , wherein the ratio of the at least one methacrylic ester to water in the hydrolyzing is between 1.5 and 3.