Catalyst for ethylene process of preparing vinyl acetate

Abstract

The catalyst for the gas phase reaction of ethylene, acetic acid and oxygen to prepare vinyl acetate has SiO2 or SiO2-Al2O3 mixture as carrier and oval distributed Pd, Au and KOAc as active components. The catalyst grain is a rod-like one with vane wheel cross section and the vane wheel has one central circular hole and 3-7 semicircular vanes. The grain length is 3-6 mm, the central hole diameter is 1.0-2.5 mm and the outer diameter of the vane wheel is 3.5-8.0. The proper shape of the grain results in the proper volume of gas passage in catalyst bed, and this results in high space-time yield, low pressure loss in catalyst bed and excellent selectivity.

Description

technical field [0001] The invention relates to a catalyst for preparing vinyl acetate by gas phase reaction using ethylene, acetic acid and oxygen or oxygen-containing gas as raw materials. Background technique [0002] In the reaction of preparing vinyl acetate by gas phase reaction with ethylene, acetic acid and oxygen or oxygen-containing gas as raw materials, the suitable catalyst is that the active component contains Pd and KOAc, and may contain Au, Ba or Cd, and / or its corresponding Salt compounds, these active components are usually loaded on SiO 2 or SiO 2 -Al 2 o 3 on the mixture. The active components of this type of catalyst have already matured. After the 1970s, people mostly studied the distribution of the active components on the carrier, and there were continuously active components such as egg yolk, egg white and eggshell. Catalyst pushes out in a non-uniform distribution. The apparent activity, selectivity and anti-poisoning ability of catalysts with ...

AI Technical Summary

Problems solved by technology

[0004] However, the size of the gas channel volume in the catalyst bed, which is directly related to the shape of the catalyst particles, has a question of moderation

Obviously, the increase of the volume of the gas channel can obtain a higher space-time yield and reduce the pressure drop loss of the bed, but if it is too large, it will cause the aggravation of the back-mixing phenomenon of the reaction material, and the residence time of the reaction material in the catalyst bed is too long , on the contrary, it is difficult to remove the heat of reaction in time, which will lead to the increase of side reactions

At the same time, the more serious back-mixing of materials also causes the products generated in the first reaction to stay excessively and cause deep oxidation, thus causing coking on the surface of the catalyst and blocking the active centers on the surface of the catalyst.

All of these will eventually lead to a decrease in the selectivity of the catalyst and the inability to keep the catalyst active for a long time

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