不同载体负载的磷化钨催化剂加氢脱硫和降烯烃性能研究

Hydrodesulfurization and reducing-olefin of tungsten phosphide catalysts over different supports

A series of supported tungsten phosphide catalysts of 30% W (counted in WO3) supported over γ-Al2O3, TiO2, SiO2, γ-Al2O3/SiO2, γ-Al2O3/TiO2 and SiO2/TiO2, respectively, were prepared by temperature-programmed reduction of the corresponding phosphates. The samples were characterized by XRD, BET and TG analysis. The activity of these catalysts were determined in the hydrodesulfurization (HDS) of thiophene and simultaneous thiophene HDS and cyclohexene reducing-olefin (HDY), respectively. The results showed that WP species could not be clearly detected in tungsten phosphide over the supports containing alumina, while species with a structure of -Al-O-W-P was obviously formed. TiO2 could play a better role in restraining the generation of WP species on the surface of composite supports than that of SiO2. TG results indicated that the starting reaction temperature of phosphiding-reduction of the supported tungsten phosphide precursor was probably determined by the structure of catalyst, while the extent of phosphiding-reduction was probably related to the interaction between support and active species and between two supports. W species on the surface of catalysts over the support containing alumina could not be completely reduced to WP and some W species may be existed in the form of -Al-O-W-P. Tungsten phosphide over different supports showed better cyclohexene HDY conversion than that of thiophene HDS conversion. The -Al-O-W-P species favor the thiophene HDS reaction and also favor the simultaneous thiophene HDS and cyclohexene HDY reactions. Besides of the TiO2, thiophene HDS activities of supported tungsten phosphide catalysts decreased to some extent by adding cyclohexene.