Mesoporous Molecular Sieve Tungsten Carbide Catalyst

Tungsten carbide is a kind of important transition metal carbides, which has the catalytic properties similar to noble metals. It has shown excellent catalytic performance in oil, gas hydrodesulfurization, denitrification, hydrocarbon isomerization and other reactions, and is the focus of attention.

The assembled mesoporous molecular sieve tungsten carbide catalyst is prepared by using triblock copolymer as template, tetraethyl orthosilicate as silicon source, ammonium paratungstate and SBA-15 mesoporous molecular sieves under acidic conditions and stirring conditions. The product is dried, roasted and template removed. Finally, the product is reduced by CH4/H2 mixture to carbonize and prepared. The specific operation steps of catalyst products are as follows:

(1)mix the template EO20PO70EO20, hydrochloric acid and water together, stir well at 40-50 degrees, and make the uniform acidic emulsion.

(2)adding ammonium partrammonium tungstate into the acidic emulsion of step 1, and stirring it well.

(3)under the stirring condition, ethyl tetraethyl orthosilicate was slowly added to the emulsion of step (2), and continued stirring for less than 20 hours.

(4)the emulsion of step (3) was crystallized for 24-32 hours at 85-100 degrees in a closed reactor.

(5)The solid precipitation obtained in step (4) is washed and dried, then calcined at 550-600 C for 6-7 hours to obtain the solid product with tungsten carbide precursor in the mesoporous molecular sieve pore.

(6)A mesoporous molecular sieve tungsten carbide catalyst was prepared from the solid product of step (5) in a fixed-bed reactor using CH4:H2 mixture with a volume ratio of 1:4. After temperature programmed reduction and carbonization, the catalyst was purged to room temperature with H2.

When tungsten carbide enters the mesoporous molecular sieve, the active components of tungsten carbide can be highly isolated and dispersed, which is conducive to improving the performance and stability of the catalyst. The structure of molecular sieves is well ordered, the catalysts have good catalytic activity at low temperature, and the particles of active components of tungsten carbide are not easy to agglomerate in the reaction process, which is of great significance to improve the application space of tungsten carbide catalysts.

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