Phosphotungstic acid modified catalyst, preparation method and application in acrolein preparation thereof

Abstract

The invention provides a phosphotungstic acid modified catalyst, and a preparation method thereof. In the catalyst, Al2O3, SiO2 or a zeolite molecular sieve is used as a vector; the vector is modified by using metal oxide, and then, glycerol is dehydrated by using supported phosphotungstic acid as the catalyst to prepare acrolein, wherein the metal oxide is alkaline-earth metal oxide, rare-earth metal oxide or transition metal oxide; the supported metal oxide accounts for 1 to 10 mass percent of the vector; and the capacity of the phosphotungstic acid is 30 percent. When the phosphotungstic acid modified catalyst is applied in the acrolein preparation, the reaction temperature is 300 DEG C, the concentration of the glycerol aqueous solution is 30 percent, inert solvent is added in the ratio of 20 to 200 percent of the glycerol solution, and space velocity of the volume of a fixed bed is 1 to 10 h-1. The precursor of the catalyst has wide sources, low price and low production cost. After the catalyst is modified by the metal oxide, the passivating speed of the catalyst is slowed down, the service life of the catalyst is prolonged, and catalytic activity is high. The catalyst can be recycled, has small corrosion to equipment, and reduces pollution to environment.

Description

technical field [0001] The invention relates to a phosphotungstic acid modified catalyst and a preparation method thereof in the process of preparing acrolein by dehydration of glycerin, and a method for treating carbon deposition on the catalyst in the process of preparing acrolein. Specifically, the modified zeolite molecular sieve loaded phosphotungstic acid is used as a catalyst, and the glycerin solution and the inert solvent are injected into the fixed-bed reactor through a micropump at the same time, and a certain reaction space velocity is controlled at the same time. In the process, the carbon deposition on the catalyst is treated, which is beneficial to prolong the life of the catalyst. Background technique [0002] Acrolein is an important fine chemical intermediate, which has a wide range of uses in coatings, papermaking, oil fields, medicine, and organic synthesis industries. In recent years, with the shortage of animal feed additives such as methionine, glutar...

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Problems solved by technology

Although the catalyst showed high selectivity, the conversion rate was very low, probably because acrolein polymerized on the surface of the catalyst and covered the surface of the catalyst, resulting in a low conversion rate of glycerol

[0007] Chinese patent CN 101070276A reports glycerol on acidic zeolite at a temperature of 200-500°C, a pressure of 0.001-3.0MPa and a liquid space velocity of 0.1-100.0h -1 Under the condition of direct dehydration to generate acrolein, the selectivity of acrolein is only about 8-10%, and the conversion rate of glycerin is not high

When the molar yield of acrolein is 61.0%, the conversion rate of glycerol is 100%, but the amount of coke adhered on the catalyst is relatively large, so that the catalyst cannot be continuously produced for a long time

[0009] In the above-mentioned patent report, although the "green" solid acid catalyst is used to reduce the investment in equipment, the reaction of dehydration of glycerol to acrolein is usually accompanied by the generation of high boiling point compounds and tar compounds, resulting in accumulation on the catalyst. Carbon formation, which deactivates the catalyst quickly

However, in this production process, how to more effectively reduce the amount of carbon deposition on the catalyst and prolong the life of the catalyst has not been reported in patents.

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