Process for preparing unsaturated esters proceeding from aldehydes by direct oxidative esterification

Patent metadata

Field	Value
Publication number	US-2016251301-A1
Application number	US-201415030775-A
Country	US
Kind code	A1
Filing date	Dec 5, 2014
Priority date	Dec 20, 2013
Publication date	Sep 1, 2016
Grant date	—

Abstract

The present invention relates to a process for preparing methyl methacrylate by a direct oxidative esterification of methacrolein with oxygen and methanol, which is conducted in the liquid phase at a pressure of 2 to 100 bar with a gold catalyst. According to the invention, the liquid phase is withdrawn continuously from the reactor and optionally enriched with oxygenous gas, the pH, after the withdrawal, is adjusted to a pH between 5 and 9 by means of addition of a basic solution and this liquid phase is conducted back into the reactor again to an extent of at least 50%.

First claim

1 . A process for preparing methyl methacrylate, comprising:
reacting methacrolein in a continuous oxidative esterification with oxygen and methanol which is conducted in a liquid phase in a reactor at a pressure of 2 to 100 bar in the presence of a heterogeneous catalyst comprising gold-containing nanoparticles having a particle size less than 20 nm; withdrawing continuously the liquid phase from the reactor and adjusting the pH after the withdrawal to a pH between 5 and 9 by addition of a basic solution outside of the reactor; and conducting at least 50% of the withdrawn liquid phase having a pH between 5 and 9 back into the reactor.

2 . The process according to claim 1 , wherein at least 70% of the withdrawn liquid phase having a pH between 5 and 9 is conducted back into the reactor.

3 . The process according to claim 1 , wherein at least 90% of the withdrawn liquid phase having a pH between 5 and 9 is conducted back into the reactor.

4 . The process according to claim 1 , wherein the gold-containing nanoparticles are present on support particles having a total diameter between 0.2 and 20 mm, and wherein the reactor is a fixed bed reactor.

5 . The process according to claim 1 , wherein the gold-containing nanoparticles are present on support particles having a total diameter between 0.2 and 20 mm, and wherein the reactor comprises a stirring apparatus.

6 . The process according to claim 1 , wherein the oxidative esterification reaction is conducted at a pressure in the range from 2 to 50 bar and at a temperature in the range from 10 to 200° C.

7 . The process according to claim 1 , wherein a feed mixture of methanol and methacrolein passed into the reactor prior to the reacting has a proportion of methacrolein, based on the mixture, in the range between 20 and 60% by weight.

8 . The process according to claim 1 , wherein a residual proportion of the liquid phase withdrawn continuously from the reactor which is not conducted back into the reactor is dewatered to form a reduced-water mixture containing methacrolein and methanol which is passed back into the reactor.

9 . The process according to claim 1 , wherein 100% of the withdrawn liquid phase is conducted back into the reactor, and wherein a product liquid phase for further workup is withdrawn continuously, semicontinuously, or batchwise elsewhere from the reactor.

10 . The process according to claim 1 , wherein an offgas from the reactor has an oxygen content of less than 8% by volume.

11 . The process according to claim 1 , wherein the pH of the liquid phase conducted back into the reactor is between 6 and 8.5.

12 . The process according to claim 1 , wherein the methacrolein is dewatered by distillation in the presence of methanol before being fed into the reactor.

13 . The process according to claim 1 , wherein the reactor is operated with a catalyst volume to reactor volume ratio greater than 0.2.

14 . The process according to claim 1 , wherein the methyl methacrylate prepared in the reactor has a 1,1-dimethoxyisobutene content of less than 0.6%.

15 . The process according to claim 1 , wherein the catalyst has a space-time-yield of greater than 3.20.

16 . The process according to claim 1 , which has a methyl methacrylate selectivity of greater than 94%.

17 . The process according to claim 1 , which has a methacrolein conversion of greater than 53%.

18 . The process according to claim 1 , wherein the gold-containing nanoparticles are present on support particles having a total diameter between 0.2 and 20 mm, and wherein the reactor is a fluidized bed reactor.

19 . The process according to claim 4 , wherein the support particles comprise at least one selected from the group consisting of SiO 2 , Al 2 O 3 , and MgO.

Assignees

• Lygin Alexander
• Krill Steffen
• Balduf Torsten
• Burghardt Rudolf
• Tepperis Andreas
• Grömping Matthias
• Evonik Roehm Gmbh

Inventors

• Krill Steffen
• Lygin Alexander
• Balduf Torsten
• Burghardt Rudolf
• Tepperis Andreas
• Groemping Matthias

Classifications

• Y02P20/582

  Recycling of unreacted starting or intermediate materials · CPC title

• B01J23/892

  Nickel and noble metals · CPC title

• B01J23/02

  of the alkali- or alkaline earth metals or beryllium · CPC title

• B01J35/19

  Catalysts containing parts with different compositions · CPC title

• B01J35/45

  Nanoparticles · CPC title