Liquid phase sulfur passivated nickel catalyst for dry reforming of methane.

Abstract

Dry reforming of methane (DRM) utilizes the two most abundant greenhouse gases: carbon dioxide (CO2) and methane (CH4) to produce a useful syngas mixture of carbon monoxide (CO) and hydrogen (H2). DRM operates at high temperatures (700℃). Thus, the traditional Ni-based catalyst used for the reforming reaction is subjected to deactivation due to coke formation and especially due to the formation of carbon whiskers. These whiskers will grow in the pores of the catalyst pellets leading to their destruction. It was shown that sulfur passivation of the catalyst during the reaction, by introducing small amounts of hydrogen sulfide gas (H2S), blocks carbon formation while allowing the reforming reaction to take place. In an attempt to improve the currently proposed gas phase sulfur passivation process, sulfur was introduced as liquid phase during the synthesis of the catalyst to eliminate the use of gaseous H2S in coating the catalyst. Partially covered nickel catalysts with different sulfur concentrations were tested in the reformer. Characterization of fresh and spent catalysts were done by XRD, TGA, BET and SEM analysis. A compromise on CH4 and CO2 conversions of 21percent and 27percent respectively with 80percent loss in carbon formed on the catalyst surface resulted from a sulfur concentration of 80 ppm (12percent coverage). The carbon deposited was in the form of undeveloped whiskers called “octopus carbon”.