Study On SBA-16 Supported Transition Metal Carbides Catalysts

Transition metal carbides have showed superior activities in hydrodesulfurization, dehydronitrogen and isomerization as their catalytic properties similar to those of the noble metals. Using Al₂O₃ and SiO₂ as Cartier of carbides catalysts can't meet the requirements because of having inferior dispersion of active components and worse stability. The mesoporous molecular sieve SBA-16 was reported to have many advantages as follows: Very high surface area, high thermal stability. It may avoid active components to get together and improve the stability of catalysts as carrier supported transition metal carbides. So in this paper, the preparation, characterization and catalytic performance of catalysts on SBA-16 cartier were mainly investigated.Firstly, SBA-16 was prepared by hydrothermal synthesis method using TEOS as silicate material and F127 and P123 as surfactant in the acidic condition. A series of MoO3/SBA-16 catalysts with different Mo contents (Si/Mo molar ratio is 30～1.0) were prepared by the incipient wetness method. Then the corresponding Mo₂C/SBA-16 catalysts were obtained by a temperature programmed carburization method. The results indicated that have the best relative catalytic activity in deep HDS of thiophene.Secondly, A series of WO_3SBA-16 catalysts with different W contents (Si/W molar ratio is 40～7.5) were synthesized by the incipient wetness method and for the first time by hydrothermal synthesis method in acidic medium. Then the corresponding W_xC/SBA-16 catalysts were prepared by a temperature programmed carburization method. The results indicated that both oxides and metal carbides were still maintained well cage-like structure of SBA-16 mesoporous molecule sieve with a cubic symmetry. In the tungsten carbide catalysts prepared by hydrothermal synthesis method, the tungsten carbide was the W₂C phase when Si/W was from 30 to 10. However, the tungsten carbides were the mixture phases of W₂C and WC when Si/W was 7.5. The WxC/SBA- 16 catalysts prepared by hydrothermal synthesis method had maintained better ordered mesoporous structure and exhibited better catalytic activity for HDS of thiophene than these by the incipient wetness method.Finally, Mo components were incorporated into WO_3SBA-16 samples in impregnation step. Then the corresponding W and Mo carbides-SBA-16 catalysts were prepared by a temperature programmed carburization method. The results indicated that all samples were still maintained well cage-like structure of SBA-16 mesoporous molecule sieve with a cubic symmetry. The catalytic activity for the thiophene improved in evidence after Mo loading has the higher conversion of thiophene than the corresponding W_xC/SBA-16 catalysts.