Molecular-Size Selective Zeolite Membrane Encapsulated Novel Catalysts for Enhanced Biomass to Liquid (BTL) Processe

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 dissertation. After detailed introduction in the first chapter, a composite H-beta zeolite membrane encapsulated 1.6wt%Ni/1.2wt%Mg/Ce 0.6Zr0.4O2 steam reforming catalyst was prepared by a physical coating method in the second chapter of the study. Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) analyses indicated that H-beta zeolite was coated successfully on the core reforming catalyst. The pore size of H-beta zeolite shell was between 0.43 and 0.57 nm, as measured by the HK method. Steam reforming of CH4 and C 7H8 (as a tar model) were conducted with the composite H-beta zeolite coated reforming catalyst, the two components individually, and physical mixtures of the two components as a function of temperature (780--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. Possible reasons for the enhanced CH4 conversion include confined reaction effects (increase residence time within pores) of the catalyst containing the zeolite coating and/or Al3+ promotion of the active sites. Alternatively, due to molecular-size selectivity, the composite H-beta 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.;A composite catalyst consisting of an outer layer of zeolite membrane encapsulating an inner reforming catalyst core was synthesized by a double physical coating method to investigate reactant selectivity (ratio of methane/toluene conversion rate) in steam reforming of methane (CH4) and toluene (C7H8). A double encapsulation (51 wt % H-beta zeolite) of a 1.6 wt % Ni--1.2 wt % Mg/Ce0.6Zr0.4O 2 steam reforming catalyst was compared to a singly coated composite catalyst (34.3 wt % H-beta zeolite) to investigate zeolite thickness effects on the conversion of different sized hydrocarbons. The increase in the zeolite content from 34.3 to 51 wt % decreased both CH4 and C7H 8 conversions (by up to 14% depending upon the temperature) as a result of the increase in diffusional limitations. Weisz-Prater criteria and Thiele moduli calculations confirmed that the reactions were performed under internal diffusion limitations. The C7H8 conversion of the 51 wt % composite (SR beta51%) catalyst was similar to the zeolite alone, indicating negligible contribution from the protected catalyst core. The reactant selectivity increased by up to 1.5 times on SR beta51% in comparison to the SR beta34.3% composite. Combined reforming at 800°C on the SR beta51% catalyst indicated that the catalyst was stable during the 10 h time on stream.;Continuing this work, a non-acidic Silicalite-1 zeolite membrane encapsulated 1.6wt%Ni-1.2wt%Mg/Ce0.6Zr0.4O2 steam reforming composite catalyst, synthesized by a physical coating method, was used to investigate effect of encapsulation on size selective steam reforming, using methane (CH4) and toluene (C7H8) as representative species. Weisz-Prater Criteria and Thiele moduli calculations indicated internal diffusion limitations. Combined reforming of CH4 and C7H 8 at 800°C on the composite catalyst demonstrated stability during the 10 h time on stream while uncoated SR catalyst deactivated. The non-acidic Silicalite-1 encapsulated catalyst showed decreases (∼2-7%) in both CH 4 and C7H8 conversions compared to acidic H-beta zeolite confirming that shell acidity did contribute to conversion and suggesting that shell defects/grain boundaries were responsible for the C7H 8 conversion.;Finally, low temperature 0.16wt%Pt--1.34wt%Ni--1.00wt%Mg/(Ce 0.6Zr0.4)O2 reforming catalyst was triple coated with H-beta zeolite (60 wt% of zeolite) to be utilized synthesis of combination steam reforming catalyst (SR) and Fischer-Tropsch Synthesis (FTS) catalyst (CRAFT) for a single-step conversion of methane to liquid fuels. Scanning electron microscopy (SEM) image and energy-dispersive spectroscopy (EDS) analysis result demonstrated that H-beta zeolite was successfully encapsulated onto the low temperature reforming catalyst. The catalyst was tested in steam reforming of methane (CH4) and toluene (C7H8) and the results was compared with 51 wt%. While CH4 conversions are very similar on the 60wt% composite catalyst with 51wt% composite catalyst, no C7 H8 conversion was seen on the 60 wt% composite catalyst. Thus, it is concluded that the 60 wt% composite catalyst can be utilized to synthesis CRAFT catalyst. (Abstract shortened by ProQuest.).