Sk. Maity et al., Studies on physico-chemical characterization and catalysis on high surfacearea titania supported molybdenum hydrotreating catalysts, APP CATAL A, 205(1-2), 2001, pp. 215-225
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.