Method for the continuous production of unsaturated carboxylic acid anhydrides

An unsaturated and carboxylic acid anhydride technology, applied in the field of continuous preparation of unsaturated carboxylic acid anhydrides, can solve problems such as the inability to completely remove by-products

Active Publication Date: 2009-06-24
EVONIK OPERATIONS GMBH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

Many by-products are formed th

Method used

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  • Method for the continuous production of unsaturated carboxylic acid anhydrides
  • Method for the continuous production of unsaturated carboxylic acid anhydrides

Examples

Experimental program
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Effect test

Embodiment 1

[0057] Embodiment 1: the preparation of methacrylic anhydride

[0058] For the preparation of methacrylic anhydride by the reaction of methacrylic acid with acetic anhydride, the assembly is according to figure 1 test device. The rectification column ( 2 ) has a total of about 35 separation stages (15 in the upper zone ( 2a ), 12 in the middle zone ( 2b ) and 8 in the lower zone ( 2c )). The columns were 5.5 m high with an internal diameter of 100 mm and were assembled with structured packings of type CY from the company Sulzer (areas 2a and 2b) and BSH 400 from the company Montz (area 2c) with intermediate connections (Zwischenstück) and bottoms. Phenothiazines are used as polymerization inhibitors. The pressure at the top of the column was 20 mbar. A temperature profile of 164° C. (bottom) to 23° C. (top) was set under static conditions. The removal of acetic acid at the top of the column and methacrylic anhydride at the side outlet (between regions 2b and 2c ) and the h...

Embodiment 2

[0063] Embodiment 2: the preparation of acrylic anhydride

[0064] For the preparation of acrylic anhydride by the reaction of acrylic acid with acetic anhydride, the same experimental setup as described in Example 1 was used.

[0065] The pressure at the top of the column, the reaction temperature and the recycle flow are practically the same as those described in Example 1. The same reactor setup, the same polymerization inhibitor, the same catalyst (type and amount) and the same boiling oil (type and amount) were also used. A temperature profile of 167° C. (bottom) to 23° C. (top) was set under static conditions.

[0066] 1500 g / h of acetic anhydride and 2118 g / h of acrylic acid were continuously metered in freshly.

[0067] 1712 g / h of acetic acid are produced overhead. 1797 g / h of acrylic anhydride with a purity of 99.7% (GC-analysis) were withdrawn at the side stream draw. The yield of acrylic anhydride was 97% based on the acetic anhydride used or the acrylic acid u...

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Abstract

The invention relates to a method for the continuous production of unsaturated carboxylic acid anhydrides of formula (I) R-C(O)-O-C(O)-R (I), wherein R is an unsaturated organic group with 2 to 12 C atoms, by anhydride exchange interaction of an aliphatic carboxylic acid anhydride with a carboxylic acid of formula (II) R-COOH (II), wherein R is defined as above, in a rectification column having an upper, a middle and a lower zone. The method is characterized in that f) an inert boiling oil is present in the sump of the column, g) the feed-stock is fed to a reaction zone in stoichiometric ratios, h) the carboxylic acid formed as a by-product is removed at the top of the column, i) the non-reacted feed-stock is returned to the reaction zone, and j) the product of formula (I) is obtained via a lateral outlet, preferably between the middle and the lower column zone.

Description

technical field [0001] The present invention describes a process for the continuous preparation of unsaturated carboxylic anhydrides, in particular the reaction of unsaturated carboxylic acids with low molecular weight aliphatic carboxylic anhydrides. Background technique [0002] DE-A-3510035 describes the continuous preparation of unsaturated carboxylic anhydrides by acid-catalyzed anhydride exchange reaction of acetic anhydride with unsaturated carboxylic acids in the middle of a distillation column. To achieve complete conversion, an excess of acetic anhydride of 0.1 to 0.5 mol per mol of carboxylic acid is used, then a mixture of acetic acid and acetic anhydride is produced overhead, ie no pure acetic acid is obtained. [0003] Furthermore, catalyst-contaminated products are formed which first have to be removed in a further process step. [0004] In US-A-4,857,239 a process is described for the preparation of methacrylic anhydride in which the molar ratio of methacryl...

Claims

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Application Information

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IPC IPC(8): C07C57/04
CPCC07C51/56C07C51/567Y02P20/582C07C57/04C07C51/083C07C67/04C07C69/757
Inventor D·布罗尔H·西格特
Owner EVONIK OPERATIONS GMBH
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