Device and method for preparing propionic anhydride through reactive distillation of acetic anhydride and propionic acid

Abstract

The invention discloses a device and method for preparing propionic anhydride through reactive distillation of acetic anhydride and propionic acid. The device comprises a reactor, a reactive distillation tower, a propionic anhydride refining tower, a condenser, a reboiler, a reflux tank, a kettle outlet tank, a pump and a pipeline. A process flow combining the reactive distillation tower with the reactor and the propionic anhydride refining tower is adopted. The method comprises the following steps: the acetic anhydride and propionic acid enter the reactor and react, and the acetic anhydride and propionic acid flowing into the reactive distillation tower react and are distilled on each layer of a tower plate of the section; the material flowing from the reaction section is distilled by a stripping section; the material rising from the reaction section is distilled by a distillation section, and 80-100% acetic acid is extracted from the tower top; the tower kettle discharge of the reactive distillation tower is pressurized and enters the propionic anhydride refining tower for distillation; several of acetic acid, acetic anhydride, propionic acid, propionic anhydride acetate and propionic anhydride are obtained from the tower top of the propionic anhydride refining tower, and the propionic anhydride with purity of 80-100% is obtained from the tower kettle of the distillation tower. The problems of unstable quality, relatively low yield and relatively low production efficiency of the products in batch production of propionic anhydride are solved.

Description

technical field [0001] The invention belongs to a device and a process for preparing propionic anhydride, in particular to a device and a process for preparing propionic anhydride by reactive distillation of acetic anhydride and propionic acid. technical background [0002] The traditional production method of propionic anhydride has the following methods: propionyl chloride and sodium propionate are heated together, the by-product sodium chloride of this method is easy to crystallize and is not easy to remove, the yield is small, and the conversion rate is low; propionic acid is dehydrated with sulfur chloride as a catalyst to obtain propionic anhydride. The by-product propionyl chloride pollutes the environment, and there are many side reactions; there are many side reactions between propionic acid and ketene, and the purity of propionic anhydride is low; under the catalysis of cobalt dioxide, propionyl chloride and propionic acid can generate propionic Acid anhydride, the...

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Problems solved by technology

[0002] The traditional production method of propionic anhydride has the following methods: propionyl chloride and sodium propionate are heated together, the by-product sodium chloride of this method is easy to crystallize and is not easy to remove, the yield is small, and the conversion rate is low; propionic acid is dehydrated with sulfur chloride as a catalyst to obtain propionic anhydride. The by-product propionyl chloride pollutes the environment, and there are many side reactions; there are many side reactions between propionic acid and ketene, and the purity of propionic anhydride is low; under the catalysis of cobalt dioxide, propionyl chloride and propionic acid can generate propionic Acid anhydride, the yield is low, and the energy consumption of separation is high; the exchange method of acetic anhydride and propionic acid is currently produced by batch method in China, and the acetic acid generated by the reaction is continuously distilled to obtain propionic anhydride with high purity. Due to batch production, the product Unstable quality, low yield and low production efficiency

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