Development of calcium silicate–based catalytic filters for biomass fuel gas reforming

Calcium silicate–based particulate filters were catalytically activated by coating first with γ-alumina and then nickel layers. Different coating techniques were compared, namely dry impregnation, wet impregnation, dry deposition-precipitation, and wet deposition-precipitation. All samples were characterized by ICP-OES, XRD, and N₂ adsorption/desorption in order only to determine total surface area and loading but also to give insight into coating dispersion and coating-substrate interaction. Regarding alumina layer, the best specific surface area was achieved when colloidal alumina sol was applied via dry impregnation method. Likewise, nickel loading onto alumina layer via dry impregnation was found to be feasible. All catalytic filters successfully gave cross-sectional pressure drop values of below 25 mbar under flowing air, which was required for sustainable filtration. Catalytic activity tests performed under simulated H₂S-free biomass gasification atmosphere gave reasonable methane and benzene conversion values between 77% and 88%. Tests performed under H₂S-containing gas caused significant activity loss despite the addition of an alkali promoter to suppress sulfur-catalyst interaction. However, the decrease of benzene conversion due to sulfur poisoning was not found to be as severe as that of methane. As a plausible explanation, a possible reaction of benzene with species like traces of CH_x and/or H₂S was claimed for the high benzene conversion.