(557f) Molecular-Size Selective Zeolite Membrane Encapsulated Novel Catalysts for Biomass to Liquid Process

Biomass to Liquid (BTL) is a promising process available to produce renewable liquid fuels. However, a major challenge is the H₂:CO ratio of biomass gasification product is insufficient for production of hydrocarbon fuels due to formation of methane and tars. The steam reforming of hydrocarbons, to improve the H₂:CO ratio, is generally conducted as part of the gas conditioning. However, tars cause the catalysts to deactivate rapidly. Zeolites can be used to solve this challenge since they have molecular sieve properties. To achieve a catalyst capable of reforming methane without potential for deactivation by tars, the encapsulation of a core reforming catalyst with porous zeolite shell is examined in this study. A composite H-β zeolite membrane encapsulated 8wt%Ni/8wt%Mg/Ce_0.6Zr_0.4O₂ steam reforming catalyst was prepared by a physical coating method. Scanning Electron Microscopy (SEM) and Energy Dispersion Spectroscopy (EDS) analyses indicated that H-β zeolite was coated successfully on the core reforming catalyst. The pore size of H-β zeolite shell was between 0.43-0.57 nm, as measured by the HK method. Steam reforming of CH₄ and C₇H₈ (as a tar model) were conducted with the prepared catalysts as a function of temperature (780 to 840°C). CH₄ conversion was enhanced by a factor of 2-3 (depending on temperature) for the composite catalyst as compared to the core reforming catalyst individually even though the zeolite did not have any activity alone. Alternatively, due to molecular-size selectivity, the composite H-β zeolite coated reforming catalyst demonstrated a decrease in C₇H₈ conversion when compared to the uncoated reforming catalyst. The results validate the use of size selective catalysts to control molecular traffic and enhance the reforming reactant selectivity.