Catalysis of methanol decomposition and carbon monoxide hydrogenation by supported molten salts.

摘要

Heterogeneous catalysis is an important tool in energy production technologies. Petrochemical industries rely heavily on heterogenous catalysts for processes such as reforming, fluid cracking and hydrogenation. Catalyst improvements have historically been responsible for commercialization of many processes. One key to economic competitiveness is the development of catalysts with improved performance.; This dissertation describes a novel heterogeneous catalyst technology, supported molten salt catalysis (SMSC). The catalysts consist of binary or ternary metal chloride (CuCl, CoCl{dollar}sb2{dollar}, KCl, ZnCl{dollar}sb2{dollar}) mixtures impregnated onto porous supports. The salt mixtures were chosen so as to be molten below the reaction temperature. SMSC has been applied to carbon monoxide hydrogenation (Fischer-Tropsch synthesis, FTS), and methanol decomposition. FTS organic products were paraffins and olefins in the range C{dollar}sb1{dollar} to C{dollar}sb{lcub}10{rcub}{dollar}. Appreciable water-gas shift activity was also detected. The methanol decomposition catalysts gave very high rates (exceeding 6,000 mol-CH{dollar}sb3{dollar}OH/L-cat{dollar}cdot{dollar}h), were stable at temperatures as high as 530{dollar}spcirc{dollar}C, and produced mainly CO and H{dollar}sb2{dollar}.; Methanol and other alcohols are of great interest as fuels, either pure or blended with gasoline. Catalytic, on-board decomposition of methanol to CO and H{dollar}sb2{dollar} could make methanol economically competitive with gasoline as a transportation fuel. The endothermic decomposition can be used to cool the engine and to produce fuel with a combustion enthalpy up to 90.6 kJ/mol higher than the stock. Methanol can also be used as a chemical feedstock. It can be safely transported to remote process sites and decomposed to regenerate synthesis-gas for catalytic conversion to higher-value chemicals.; SMSC catalyst activity increased over time, particularly during methanol decomposition. EM, EDX microanalysis and XRD were used to probe changes in the catalyst following methanol decomposition. It was found that copper chloride in the eutectic was largely reduced to metallic copper, resulting in loss of the molten salt character. Copper particle size estimates from EM and XRD were 10-50 nm.; The primary goal of this research was to establish the significance of SMSC in the development of novel catalysts. Emphasis was placed on understanding the effect of catalyst composition and process parameters on activity and selectivity.