New insight on competitive reactions during deep HDS of FCC gasoline

Dos Santos, N. Dulot, H. Marchal, N. Vrinat, M.In order to satisfy requests for high purity fuel, sulfur compounds have to be removed selectively from FCC gasoline with a minimum of olefins hydrogenation and recombination between olefins and H2S (product of hydrodesulfurization) to form thiols. Competition between hydrodesulfurization (HDS) and olefin hydrogenation (HYD) is truly a non-trivial subject. In this study, the impact of H2S on reactivity and selectivity has been studied for model compounds (3-methylthiophene and 1-hexene in heptame) under operating conditions allowing kinetic studies. Formation of C-6-thiols appears to be under thermodynamic control. Inhibition of H2S on both HDS and HYD reactions has been demonstrated. Moreover, inhibition of olefins on HDS and of 3MT on hydrogenation have been observed. This competition between HYD and HDS reactions is an argument in favor of an adsorption of both olefin and sulfur compounds on the same active sites. (C) 2008 Elsevier B.V. All rights reserved

Amorphous cobalt oxysulfide as a hydrogen trap

Solid amorphous cobalt oxysulfide "CoSOH" obtained by basic aqueous precipitation absorbs gaseous hydrogen up to limit close to the H 2/Co molar ratio of 0.5. To understand the nature of this phenomenon, the cobalt compound was characterized before and after hydrogen absorption (XRD, IR, TEM, XPS, inelastic neutrons scattering, and extended X-ray absorption fine structure spectroscopy). The initial oxysulfide is an amorphous solid containing hydroxide groups and sulfide moieties. Considerable amounts of hydrogen (as high as 0.3 mol of H2/Co atom) can be absorbed by this solid without any apparent changes of its structure and morphology, due to the reductive opening of S-S bridges leading to the formation of -SH groups. At higher levels of hydrogen consumption (0.3-0.5 mol of H2/Co atom), formation of crystalline Co9S8 compound was observed. Isotopic exchange and volumetric experiments demonstrated that the absorption of hydrogen is a slow and irreversible first-order solid-gas reaction. © 2006 American Chemical Society

Compensation effect and volcano curve in toluene hydrogenation catalyzed by transition metal sulfides

Guernalec, N. Geantet, C. Cseri, T. Vrinat, M. Toulhoat, H. Raybaud, P.Within the framework of volcano curves, a kinetic study of toluene hydrogenation catalyzed by transition metal sulfides highlights the variation of the apparent kinetic parameters as a function of the ab initio sulfur-metal bond energy descriptor and sulfo-reductive reaction conditions

Low-temperature hydrogen interaction with amorphous molybdenum sulfides MoSx

SURF:RAFFInternational audienc