Process and apparatus for preparing alkyl esters of methacrylic acid

Patent metadata

Field	Value
Publication number	US-9637574-B2
Application number	US-51596407-A
Country	US
Kind code	B2
Filing date	Aug 31, 2007
Priority date	Dec 8, 2006
Publication date	May 2, 2017
Grant date	May 2, 2017

Abstract

The present invention relates to a process for preparing alkyl methacrylates and their conversion products which can be used in a multitude of chemical synthesis processes which can lead to a wide variety of different further processing products, and to an apparatus for performing this process.

First claim

The invention claimed is:

1. A process for preparing an alkyl methacrylate, comprising the following steps a)-j) in order:
a) subjecting a reaction mixture comprising methacrylamide, water, concentrated sulphuric acid and at least one alkanol to an esterification reaction in a series of two or more reaction chambers comprising at least a first reaction chamber and a second reaction chamber to obtain a crude reaction product, wherein the water, the methacrylamide and the concentrated sulphuric acid are charged to the first reaction chamber and the alkanol is charged to each of the reaction chambers in the series such that the amount of the alkanol charged decreases by at least 10% from the reaction chamber to the next reaction chamber based in each case on the amount charged in the preceding reaction chamber;
b) heating the reaction chambers in the series with steam such that vapor phase of an esterification reaction product mixture comprising water, alkyl methacrylate, alkanol and compounds having a higher boiling point than the alkyl methacrylate and alkanol, is formed;
c) transferring the vaporous esterification reaction product mixture from the first reaction chamber to the second reaction chamber and any further reaction chambers, and transferring the vapor phase from the at least the second reaction chamber to a rectification column using steam as a carrier;
d) separating the high boiling compounds of the vapor phase from the water, the alkyl methacrylate and the alkanol in the rectification column, recycling the high boiling compounds to the first reaction chamber and drawing off a vapor mixture of the water, the alkyl methacrylate and the alkanol from the top of the rectification column;
e) condensing and cooling the vapor mixture of the water, the alkyl methacrylate and the alkanol in one or more heat exchangers to provide a condensate having an aqueous phase comprising water and alkanol and an organic product phase comprising the alkyl methacrylate;
f) separating the aqueous phase of the condensate from the product organic phase and recycling the separated aqueous phase to the first reaction chamber;
g) washing the separated product organic phase with water to obtain a washed product organic phase comprising a crude alkyl methacrylate and an aqueous phase comprising the washing water and alkanol washed from the product organic phase;
h) recycling the aqueous phase comprising the washing water and alkanol from the step g) back into the first reaction chamber;
i) freeing the crude alkyl methacrylate of low-boiling impurities which have a lower boiling point than the alkyl methacrylate by distillation in a distillation column; and
j) freeing the alkyl methacrylate obtained in i) of higher-boiling impurities which have a higher boiling point than the alkyl methacrylate prepared;
wherein
the low-boiling impurities from step i) are condensed in one or more heat exchangers, to obtain a condensate of the low boiling impurities;
the condensate of the low boiling impurities is treated with water, followed by a phase separation, the aqueous phase of the condensate of the low boiling impurities is recycled into at least one reaction chamber in the series, and the organic phase removed by phase separation is used to spray the top of the distillation column in the step i);
wherein the water present in the reaction mixture stems to an extent of at least 60% by weight from the following sources:
the recycled aqueous phase in h),
a portion of the aqueous phase obtained from the water treatment of the low-boiling impurities of i),
distillatively removing the high boiling impurities from the crude alkyl methacrylate in j), and

optionally comprising the steps of obtaining a stream comprising a spent sulfuric acid from the esterification reaction chambers in the series, contacting the spent sulfuric acid with steam and subsequently condensing a mixture of a crude reaction product and the steam thus obtained, and recycling the condensate of the mixture of the crude reaction product and the steam to the first reaction chamber.

2. The process of claim 1 , further comprising:
k) withdrawing a stream mixture comprising water, ammonium salts, a reaction product, solids and a spent sulphuric acid from at least one of the second reaction chamber and any further reaction chambers in the series,
l) feeding the stream mixture to at least one flotation vessel, wherein the stream mixture is freed of solids by flotation,
m) charging the flotation vessel with steam wherein the reaction product is converted from the stream mixture into the vapour phase,
n) cooling the vapour phase comprising at least water and an alkyl methacrylate in a heat exchanger to form a postcondensate comprising the water and the alkyl methacrylate, and
o) recycling the postcondensate into the first reaction chamber.

3. The process of claim 1 , further comprising:
recycling the higher-boiling impurities from step j) into the first reaction chamber.

Assignees

• Gropp Udo
• Weber Robert
• Schaefer Thomas
• Perl Andreas
• Sing Rudolf
• Mertz Thomas
• Evonik Roehm Gmbh

Inventors

• Gropp Udo
• Weber Robert
• Schaefer Thomas
• Perl Andreas
• Sing Rudolf
• Mertz Thomas

Classifications

• C08F20/10 Primary

  Esters · CPC title

• C07C67/20 Primary

  from amides or lactams · CPC title

• C09D4/00

  Coating compositions, e.g. paints, varnishes or lacquers, based on organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond {; Coating compositions, based on monomers of macromolecular compounds of groups C09D183/00 - C09D183/16} · CPC title

• D21H17/37

  Polymers of unsaturated acids or derivatives thereof, e.g. polyacrylates · CPC title

• C07C69/54

  Acrylic acid esters; Methacrylic acid esters · CPC title