(529j) Biomass Gasification: Effect of Sulfur Compounds On Catalytic Tar Removal Activity Using Nickel-Clay Catalysts

Biomass gasification is one of the thermochemical routes of converting biomass to fuel gas. This fuel gas can be used in various possible applications such as generation of heat or electricity, synthesis of liquid transportation fuels, production of hydrogen, synthesis of chemicals and generation of electricity in fuel cells. However, this fuel gas needs to be cleaned from the impurities like particulates, ammonia, hydrogen sulfide, hydrogen chloride, alkali metals, metals, and tars. The presence of tars in the fuel gas is one of the main technical barriers in the biomass gasification development. Tar buildup cause cracking in the pores of filters, forming coke and plugging the filters, and condensing in the cold spots and plugging the lines, resulting in serious operational interruptions.

Nickel (Ni) supported clays have been developed and evaluated for its activity towards tar removal at Mississippi State University. The results from these studies suggested that Ni-Clay catalysts have very good activity for tar removal.  However, the influence of sulfur compounds, although, present in very low concentrations has not been evaluated. Hence, this study focuses on the effect of sulfur compounds on the catalyst performance for removal of tars from syngas. Literature suggests that the presence of sulfur in the fuel gas decreases the catalytic activity of the Ni catalysts due to strong chemisorption of sulfur on the Ni surface forming Nickel Sulfide, which is inactive. Although, the presence of sulfur has shown to have an inhibiting effect on the catalytic activity, the effect of sulfur on tar removal using Ni-Clays has not been investigated till date. This study investigates the influence of sulfur compounds on tar reforming activity of Ni Clay catalysts. A plug flow reactor has been designed and fabricated to perform these studies. Experiments are being conducted using naphthalene as a tar model compound and hydrogen sulfide as a sulfur compound in syngas. The effect of hydrogen sulfide partial pressure, temperature(650-850^o C), steam to carbon ratio, and residence time on naphthalene removal activity is being evaluated, the results of which will be presented. Also, the influence of catalyst support, clay in this study is being investigated and will be compared with commercial silica/alumina supports.