Preparation method of catalyst in preparation of dimethyl ether by methyl alcohol

Abstract

The invention discloses a preparation method of a catalyst in the preparation of dimethyl ether by methyl alcohol, the preparation process is that: eudo-boehmite powder is roasted to be active alumina powder at the temperature of 500 DEG C; then, the active alumina powder is mixed with catalysis additives such as HZSM-5 molecular sieve, titanic sulfate, heteropolyacid and the like; chemical paste, citric acid and a peptizing agent are added into the mixture for uniform mixing and rolling compaction, so as to form dough material; the dough material is extruded into bands and molded in a band extrusion machine; and after the drying and roasting, the catalyst in the preparation of dimethyl ether by methyl alcohol is obtained. The catalyst prepared in the invention not only has good activation, selectivity and stability, but also has appropriate acidity and environmentally friendly, has no corrosion to equipment and can be used in the industrial production for preparing the dimethyl ether.

Description

technical field [0001] The invention relates to a method for preparing a catalyst, in particular to a method for preparing a catalyst for preparing dimethyl ether from methanol. Background technique [0002] Dimethyl ether, also known as methyl ether, or DME for short. Dimethyl ether is a colorless, odorless, low-toxic, chemically stable, and water-soluble gas at room temperature. As an important chemical raw material, it is widely used as aerosol, refrigerant and various organic synthetic raw materials in the chemical and pharmaceutical industries. DME can be used in the synthesis of many fine chemicals, such as pharmaceuticals, fuels, pesticides, etc. Liquid DME has good solubility to polar and non-polar organic substances, so it is widely used in aerosol spray solvents, such as hairspray, mousse, air freshener, insecticide, spray paint, foaming agent, etc., and DME is also It can replace Freon as a low-toxic refrigerant, extractant and anesthetic. In recent years, wit...

AI Technical Summary

Problems solved by technology

Invention patents CN1322704 and CN1111231A reported a method for preparing dimethyl ether using liquid acid as a catalyst. The reaction temperature of this method is low and the conversion rate is high. The treatment method is not matched, and the pollution of the environment is serious

The stronger the acidity of the catalyst, the faster the dehydration reaction speed, the lower the activation temperature, and the higher the conversion rate of methanol; but as the conversion rate increases, the selectivity of the target product dimethyl ether becomes worse, and more side reactions occur At this time, carbon deposits and coking occur on the surface of the catalyst, resulting in a rapid decline in the activity of the catalyst.

If the catalyst is weak in acidity and the catalyst activity temperature is low, the reaction temperature must be increased to increase the conversion rate of methanol. Although dimethyl ether has high selectivity, the energy consumption is high, which is not conducive to the improvement of economic benefits.

Although HZSM-5 molecular sieve, dealuminated Y molecular sieve, dodecatungstophosphoric acid, aluminum cyanate, superacid modified alumina, etc. have the advantages of low activation temperature and high methanol conversion rate, they have narrow applicable temperature range and poor selectivity of dimethyl ether. , the side reaction is serious, and the surface of the catalyst is easy to deposit carbon, and the activity decreases rapidly

Although ordinary alumina is used as a catalyst, although the selectivity of dimethyl ether is good, there are disadvantages such as poor low-temperature activity and serious high-temperature carbon deposition.

At present, there is a common shortcoming in commercially available catalysts: when crude methanol is used as raw material, the alkaline substances such as ammonia contained in it will easily destroy the acidic center of the catalyst, causing the catalyst to be poisoned and deactivated.

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