Master of Science in Chemical Engineering (MSChE)
Biomass gasification and subsequent conversion to liquid hydrocarbons using Fischer-Tropsch synthesis is a promising source of energy in today’s scenario when the focus has shifted from conventional fuels to alternate sources of energy. Biomass derived syngas is different from other sources of syngas such as steam reforming of methane followed by water gas shift, in terms of H2/CO ratio. Biomass syngas is usually hydrogen deficient and contains various impurities which need to be removed prior to Fischer-Tropsch Synthesis. Syngas derived from biomass also differs significantly with the different sources of biomass, gasification process and the cleanup conditions it is subjected to. The syngas used in this study has been produced by the air-blown, atmospheric pressure gasification of wood. The syngas from the gasification step is compressed and cleaned in a series of sorbents to produce the following feed to the F-T step: 2.78% methane, 11% CO2, 15.4 % H2, 21.3% CO and balance N2. The relatively high level of CO2, suggests the need to explore catalysts that are active for CO2 hydrogenation as well is resistant to oxidation in presence of high levels of CO2. Here we report the effect of three different structural promoters Si, Al and Zn on iron-based Fischer-Tropsch catalysts; specifically 100Fe/5Cu/4K/15Si, 100Fe/5Cu/4K/15Al and100Fe/5Cu/4K/15Zn. Although the effect of Si, Al or Zn on iron-based F-T catalysts has been examined previously in separate studies for CO+CO2 hydrogenation, there is no direct comparison of these three structural promoters, nor any studies of these promoters for a syngas that has been directly derived from biomass and has a similar composition. In the present study, we found that catalysts promoted with Zn and Al showed higher extent of reduction and carburization and higher amount of carbides and CO adsorption as compared to Fe/Cu/K/Si catalyst, resulting in higher activity and selectivity to C5+ hydrocarbons than the catalyst promoted with silica. The activity as measured by CO+CO2 conversion was in the order Zn>Al>Si. The Si-promoted catalyst had highest selectivity for methane and lower weight hydrocarbons.
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Sharma, Pratibha, "Catalytic Conversion of Biomass Derived Syngas to Liquid Fuels using Fischer-Tropsch Synthesis" (2013). LSU Master's Theses. 3193.
Spivey, James J