The sustainable biomass economy requires development of different integral processes to lower the cost of producing fuels and chemicals form ligno-cellulosic biomass. Accordingly, the new concept for the catalytic conversion of the biomass to monofunctional hydrocarbons and targeted liquid fuels have been provided, where the sugars and polyols were first converted into small oxygenates over a Pt-Re/C catalyst. The development of the limited steps for the upgrading those mono-functional oxygenates are necessary in order to achieve value added chemicals or fuels. We conducted the gas phase butanal self-condensation reactions as a model study for the carbon-carbon forming reactions. The unsupported MgO and CeZrOx solid solution showed less active for the reaction. The silica supported MgO, SrO and a mixture of MgO/SrO catalyst showed improved activity. However, the catalysts deactivated very quickly due to the self-poisoning by butanoic acid, a compound generated through side reactions. CeZrOx/SiO2 showed a promising performance on butanal self-condensation with about 40% conversion of butanal at 300 ēC and good stability. The effects of the reaction temperatures, addition of butanoic acid and supports were studied and compared over the MgO/SiO2 and CeZrOx/SiO2 catalysts. The CeZrOx/SiO2 catalyst is much more acid-tolerant compared with MgO/SiO2 and lowered the reaction temperature approximate 100 ēC with the same butanal conversion. The reaction chemistry was studied. The predominate reaction pathway is the aldol condensation of butanal with about 85% selectivity to first addition product and 6 % selectivity to second addition products. The side reactions include Tishchenko esterification reactions, hydrolysis, ketonizations, isomerizations and hydrogenation/dehydration reactions. The nature of the active sizes and the reaction mechanism were also studied by a combination of TPD and in-situ FTIR studies.
Keywords: Butanal self-condensation; CeZrOx solid solution; Silica supported CeZrOx, supported and unsupported alkaline metal oxide; CO2-TPD; NH3-TPD; in-situ FTIR
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