Intrinsic potential of alumina-supported CoMo catalysts in HDS: Comparison between gamma c, gamma T, and delta-alumina
Résumé
MoS2 catalysts were firstly prepared over three different alumina supports gamma c-Al2O3, gamma T-Al2O3, and delta-Al2O3 with the same Mo loading per nm(2). Then, using various deposition methods and different Co-precursors as Co(NO3)(2), Co(acac)(2) and Co(CO)(3)NO, Co-promoted MoS2 catalysts were obtained. The different catalytic systems were tested in hydrodesulfurization (HDS) reactions of thiophene and 4.6-dimethyldibenzothiophene (4,6-DMDBT) under atmospheric and high pressure (4 MPa), respectively. For the non-promoted catalysts, we observed for delta-alumina supported system a higher intrinsic catalytic activity than for gamma c-Al2O3 and gamma T-Al2O3. For the Co-promoted systems, the use of cobalt organometallic complex allowed obtaining catalysts which exhibit higher intrinsic activity than the catalysts prepared by impregnation of Co inorganic salts on supported Mo sulfide. Furthermore, the intrinsic catalytic activities of promoted systems obtained with delta-alumina support were always higher than for the classical gamma-alumina. This support effect can be partially explained and supported by physicochemical characterization results of XPS and IR of adsorbed CO at low temperature (77 K). (c) 2012 Elsevier Inc. All rights reserved.