Catalyst for preparing isoolefin by cracking tertiary alkyl ether, preparation method for catalyst and application of catalyst

Abstract

The invention relates to a catalyst for preparing isoolefin by cracking tertiary alkyl ether. The catalyst comprises an amorphous silicon-aluminum composite carrier and sulfur oxide which is supported on the carrier. The invention also relates to a method for preparing the catalyst. The method comprises the following steps of: impregnating the amorphous silicon-aluminum composite carrier by using an ammonium sulfate solution, an ammonium bisulfate solution, a sulfuric acid solution or a mixture of the ammonium sulfate solution, the ammonium bisulfate solution and the sulfuric acid solution, and drying and roasting the impregnated amorphous silicon-aluminum composite carrier. The invention further relates to a method for preparing the isoolefin by cracking the tertiary alkyl ether by using the catalyst. The methods for preparing the catalyst and preparing the isoolefin by using the catalyst have the advantages of high conversion rate of tertiary alkyl ether, high selectivity of isoolefin and alcohol, high feed loading, high stability and the like.

Description

technical field [0001] The invention relates to a catalyst for cracking tertiary alkyl ethers to prepare isoolefins, a method for preparing the catalyst and its application in cracking tertiary alkyl ethers to prepare isoolefins. Background technique [0002] With the development of chemical industry, isoolefin has become an important raw material in the field of organic chemical industry. For example, isobutylene and isopentene, especially isobutylene, have been widely used. For example, isobutylene can be used to manufacture dozens of chemical products such as butyl rubber, polyisobutylene, antioxidants, and plexiglass. Compared with other isobutene production processes such as sulfuric acid extraction, tert-butanol dehydration, isobutane dehydrogenation, n-butene isomerization, etc., the production of isobutene by cracking methyl tert-butyl ether (MTBE) is a better economic benefit. and widely used method. [0003] The main reaction of cracking tertiary alkyl ethers to ...

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Problems solved by technology

But the feed load of the catalyst is low, specifically the reaction feed space velocity is only 0.5-1.0h -1 , resulting in too large cracking reactor volume and high investment in production equipment

[0005] The catalyst described in Chinese invention patent application CN 1432431A published on July 30, 2003 is composed of alumina-modified silica carrier and fluoride supported on the carrier, which is prepared by cracking methyl tert-butyl ether The reaction of isobutene has the characteristics of high conversion rate, good selectivity of isobutene and methanol, etc., but the reaction activity of this catalyst decreases obviously after a short period of use, which is not conducive to industrial use

[0006] The catalyst described in the Chinese invention patent application CN 1853772A published on November 1, 2006 is obtained by treating amorphous silica-alumina with saturated water vapor, but its reactivity is relatively low and the required reaction temperature is relatively high

However, too high temperature will also promote the dehydration of methanol to generate dimethyl ether, reducing the yield of methanol

At the same time, in the subsequent refining process of isobutene, a part of isobutene has to be discharged in order to remove dimethyl ether, which leads to the reduction of isobutene yield and production economic benefits

In addition, in the method described in CN 1853772A, in order to improve the selectivity of methanol, water needs to be added to the reactor, and the water is heated to the reaction temperature, which leads to an increase in reaction energy consumption, and at the same time, the added water will promote Hydration of isobutene to tert-butanol reduces isobutene selectivity

[0007] In the case of using some modified alumina catalysts, in order to maintain the high selectivity of isobutene and methanol, it is often necessary to control a lower conversion rate of methyl tert-butyl ether such as about 80%. At this time, unreacted formazan needs to be recovered tert-butyl ether and recycle it, and thus increase separation equipment and energy consumption

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