Date of Award
Doctor of Philosophy
Chemical and Biological Engineering
The catalytic activity of Chevrel phase compounds (M(,x)Mo(,6)S(,8)) for thiophene hydrodesulfurization at 400(DEGREES)C has been found to be comparable to or greater than that of model industrial catalysts (unpromoted and cobalt-promoted MoS(,2)). The most active Chevrel phase catalysts were those containing the "large" ternary compo- nent cations Ho, Pb, Sn; the "intermediate" cation materials (M = Ag and In) were less active; the "small" cation materials (M = Cu, Fe, Ni, and Co) were the least active catalysts. The 1-butene hydrogenation activities of the Chevrel phase catalysts at 400(DEGREES)C were much lower than MoS(,2), with the exception of Ni(,1.6)Mo(,6)S(,8.);X-ray powder diffraction and laser Raman spectroscopy analysis of the used (10 hours of thiophene reaction) catalysts revealed that the bulk structures were stable under reaction conditions. XPS analysis of the fresh Chevrel phase catalysts (Mo 3d(,5/2) binding energies near 227.5 eV) showed reduced molybdenum surface oxidation states compared to the Mo('+4) state of MoS(,2) catalysts. After thiophene reaction, various degrees of oxidation of the surface molybdenum states could be detected for the small and intermediate cation materials, with an accompanying loss of ternary component from the surface. For the large cation materials, there was no analogous surface molybdenum oxidation or loss of the ternary component;Using a deuterium-thiophene feed at 400(DEGREES)C, the amount of deuterium incorporated into thiophene and into the desulfurization products (hydrogen sulfide, butadiene, and butenes) was determined as a function of reaction time. For all Chevrel phase and MoS(,2) catalysts examined, H(,2)S was almost exclusively formed (typically 90+ %); only small amounts of HDS and D(,2)S were detected. At the same levels of thiophene conversion, unpromoted MoS(,2) introduced up to 10 times more deuterium into the nondesulfurized thiophene than did the "promoted" catalysts. With the exception of the unpromoted MoS(,2) catalyst, the deuterium distributions of cis and trans-2-butene were nearly identical but distinct from that of 1-butene;A mechanism of thiophene hydrodesulfurization is proposed: butadiene is the initial reaction product and the hydrogen of hydrogen sulfide originates from the hydrogen-exchange of thiophene; ('1)DOE Report IS-T-1168. This work was performed under contract No. W-7405-Eng-82 with the U.S. Department of Energy.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Kevin Francis McCarty
McCarty, Kevin Francis, "Hydrodesulfurization catalysis by Chevrel phase compounds " (1985). Retrospective Theses and Dissertations. 7870.