Abstract
This thesis investigates the catalytic conversion of synthesis gas (syngas) to mixed alcohols (C1-C5) over alkali-doped molybdenum sulfide (MoS2) catalysts, a potential pathway of producing fuels and chemicals. If using biomass as the feedstock for the syngas generation, carbon-neutral fuels can be produced. Alkali-promoted MoS2-based catalysts show various characteristics: high coke resistance, sulfur tolerance, high selectivity to higher alcohols, and high water-gas shift activity. These advantages make them suitable for syngas derived from biomass, which typically has a low H2/CO ratio and moderate sulfur content. In this work, a total of six experiments were conducted on a bench-scale mixed-alcohol synthesis (MAS) system, with variations in temperature, pressure, syngas-mixture composition, and amount of methanol injection. These experiments are designed to study the effects of the various parameters on the MAS liquid production and composition as well as the resulting sulfur compounds in the gas and liquid phase. As a result, it was found that lower temperatures favored the production of mixed alcohols while higher temperatures favored the production of methane. Increasing the CO2 concentration and decreasing the H2/CO ratio in syngas mixtures resulted in lower alcohols production. Higher pressure increased productivity of all alcohols. Finally, recycle of methanol into the supplied syngas had little effect on the production and distribution of alcohols at low temperature while most of the methanol was converted into methane at high temperature.