(402d) Contaminant-Tolerant Fuel Reforming/Upgrading Catalyst for Fuel Cell Systems

Authors: 
Goyal, A., Southern Research
Lucero, A., Southern Research
McCabe, K., Southern Research
Gangwal, S., Southern Research

Fuel cells can efficiently produce electricity using hydrogen.  Fuels proposed for use in fuel cell processors include gaseous fuels (e.g. natural gas, liquefied petroleum gas, landfill gas, and digester gas), liquid fuels (e.g. gasoline, jet fuel, and diesel) and solid fuels (e.g. coal, biomass, and municipal solid waste).  All fuels are either reformed or gasified to produce syngas (CO + H2) and the syngas is then subjected to water gas shift (WGS) to produce hydrogen for the fuel cell.  Typically, solid fuels are thermally (non-catalytically) gasified whereas gaseous and liquid fuels are catalytically reformed using steam and air.  The contaminants in the solid fuels, particularly sulfur and nitrogen, appear in the syngas as H2S and NH3.  In addition, gasification invariably leads to light gaseous hydrocarbon and tar formation, unless carried out at temperatures in excess of 1300oC.  The raw syngas from solid fuel gasification containing light hydrocarbons, H2S, NH3, and tar must be cleaned prior to its use in the fuel cell to prevent the poisoning of the fuel cell anode catalyst.  Also, to reduce cost, the light hydrocarbons need to be reformed to produce additional syngas.  Gaseous and liquid fuels on the other hand need to be desulfurized prior to the catalytic reformer to avoid the poisoning of the conventional nickel-based reforming catalyst.  This paper describes the development and laboratory-scale test results of cost-effective contaminant-tolerant reforming/upgrading catalysts suitable for reforming of sulfur containing gaseous and liquid fuels as well as for cleaning/upgrading of raw syngas from solid fuel gasification. Experiments were carried out using raw simulated gasifier syngas.  Results showed that the best performing catalysts maintained high methane reforming, tar reforming, and ammonia decomposition activity for the duration of the testing (200 hours) in the presence of about 100 ppmv H2S.  Furthermore, the catalysts demonstrated significant tolerance to H2S even at H2S concentration levels of 500 ppmv.  Techno-economic evaluation showed that the use of the sulfur- and contaminant-tolerant catalysts developed in this work for an auto-thermal reformer, as opposed to using a desulfurizer prior to the auto-thermal reformer employing a conventional nickel reforming catalyst, can result in a more compact and economical overall fuel processor for gaseous and liquid fuels.