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Effect of Sulfur on Mo2C-Supported Liquefied Petroleum Gas Steam Reforming Catalysts

Peng Wang, FCC catalyst, RIPP,Sinopec, No.18 Xueyuan Road, Beijing, China and Levi Thompson, Chemical Engineering Department,Hydrogen Energy Technology Laboratory, University of Michigan, 3074 H.H. Dow, 2300 Hayward, Ann Arbor, MI 48109.

Liquified Petroleum Gas (LPG) is easily transported and stored on-site, and has emerged as a promising candidate for use in residential fuel cell power supplies. Like other fossil fuels, LPG contains sulfur, a poison for most catalysts including those electrocatalysts in fuel cells and thermochemical catalysts in fuel processors. Research described in this paper investigated the effects of sulfur on Mo2C-supported metal steam reforming catalysts. A mixture containing 10~50 ppm ethyl mercaptan and propane was used as a surrogate. While most of the materials were severely and irreversibly poisoned by sulfur, some materials exhibited good tolerance to sulfur. The degree of sulfur tolerance was evaluated based on decay curves collected for a range of ethyl mercaptan concentrations. Properties for the Mo2C-supported catalysts were compared with those for more traditional Al2O3-supported base and noble metal catalysts containing, for example, Ni, Cu, and Pt. In general, the Mo2C-supported catalysts were more resistant to poisoning by sulfur. The basis for the sulfur tolerance was investigated using x-ray diffraction, x-ray photoelectron spectroscopy, thermal desorption spectroscopy and infrared spectroscopy. The results indicated that the surface areas and bulk phases were not significantly affected by the presence of sulfur. Some sulfur was incorporated into the surface producing what we believe were sulfido-carbide domains. We also explored the use Mo2C-supported bimetallic catalysts. Tin appears to be a particularly effective secondary component producing materials with better resistance to deactivation by carbon deposition and sulfur incorporation. These and other results will be presented in this paper.