Studies on physico-chemical characterization and catalysis on high surfacearea titania supported molybdenum hydrotreating catalysts

A series of titania supported molybdenum catalysts were prepared by incipie nt wetness impregnation method and characterized by BET surface area, XRD, TPR, FTIR, ESCA, and low temperature oxygen chemisorption. Thiophene. cyclo hexene and tetrahydrofuran were taken as model compounds for evaluating cat alytic activities for hydrodesulfurization (HDS), hydrogenation (HYD), and hydrodeoxygenation (HDO) reactions, respectively. XRD results indicate that molybdenum oxide species are dispersed as a monolayer on the support up to 8 wt.% Mo and the formation of crystalline MoO3 is observed above this loa ding. FTIR and TPR results showed that molybdenum oxide species were presen t predominantly in tetrahedral form at lower loading and polymeric octahedr al forms are dominant at higher loading. Both oxygen chemisorption and rate s of reaction were found to increase with increasing Mo loading up to 8 wt. % and then decrease with further increase in loading. HDS and HYD activitie s are more or less same but HDO activity is two times higher than HDS and H YD activities. The results are also interpreted with the help of other para meters, like dispersion, equivalent molybdenum surface area, surface covera ge, crystalline size, quasi-turnover frequencies and intrinsic activities. ESCA results suggest that electron transfer is taking place from support to metal. (C) 2001 Elsevier Science B.V. All rights reserved.