Method for producing methylmethacrylate
The present invention relates to a process for producing methyl methacrylate, comprising the following steps: A) producing methacrolein and B) reacting the methacrolein obtained in step A) in an oxidative esterification reaction to give methyl methacrylate, characterized in that the two steps A) and B) take place in a liquid phase at a pressure of from 2 to 100 bar, and step B) is carried out in the presence of a heterogeneous noble-metal-containing catalyst comprising metals and/or comprising metal oxides.
1. A process for producing methyl methacrylate, the process comprising:
A) producing methacrolein from propanal and formaldehyde and
B) reacting the methacrolein in an oxidative esterification reaction to obtain methyl methacrylate,
wherein
the producing A) and the reacting B) take place in a liquid phase at a pressure of from 2 to 100 bar, and
the reacting B) is carried out in the presence of a heterogeneous noble-metal-comprising catalyst which does not comprise palladium and which comprises at least one selected from the group consisting of gold and nickel.
2. The process according to claim 1 , wherein the producing A) is carried out in the presence of from 0.1 to 20 mol % of organic base and from 0.1 to 20 mol % of acid, based in each case on propanal.
3. The process according to claim 1 , wherein the producing A) is carried out at a temperature of from 100 to 300° C.
4. The process according to claim 1 , wherein the producing A) is carried out at a pressure of from 5 to 100 bar.
5. The process according to claim 1 , wherein the heterogeneous oxidation catalyst comprises one or more ultra-finely dispersed metals with an average particle size of <20 nm selected from the group consisting of gold and nickel.
6. The process according to claim 2 , wherein the organic base comprises a secondary amine.
7. The process according to claim 2 , wherein the acid comprises at least one organic acid.
8. The process according to claim 2 , wherein a molar ratio of the acid to the organic base ranges from 20:1 to 1:20.
9. The process according to claim 1 , wherein the producing A) is carried out with a residence time ranging from 0.1 to 300 seconds.
10. The process according to claim 1 , wherein the reacting B) is carried out with a pressure ranging from 2 to 50 bar.
11. The process according to claim 1 , wherein the oxidative esterification reaction is carried out at a temperature ranging from 10 to 200° C.
12. The process according to claim 1 , wherein the oxidative esterification reaction takes place in the presence of methanol with a molar ratio of methanol to methacrolein ranging from 1:1 to 50:1.
13. The process according to claim 1 , wherein the producing A) and the reacting B) are carried out in a continuous process.
14. The process according to claim 1 , wherein a volume ratio of a reactor in the producing A) to a reactor in the reacting B) ranges from 1:1000 to 1:100.
15. The process according to claim 1 , wherein a total amount of any separately added water in the producing A) and the reacting B) during the process is not greater than 100 mol %, based on methacrolein.
16. The process according to claim 1 , wherein no water is separately added in the producing A) and the reacting B) during the process.
17. The process according to claim 1 , wherein a content of water in reaction mixture during the reacting B) is at most 10% by weight based on a total weight of the reaction mixture.
18. The process according to claim 17 , wherein no dewatering is conducted after the producing A) and before the reacting B).
19. The process according to claim 1 , wherein the heterogeneous noble-metal-comprising catalyst comprises nickel.