The kinetics of the heterogeneous catalytic epoxidation of propene to propene oxide with hydrogen peroxide and titanium silicalite (TS-1) as the catalyst was studied under mild conditions in an autoclave reactor using methanol/ water mixtures as the solvent. The effects of reactant concentration, solvent composition, catalyst loading, stirring speed, and reaction temperature on the propene oxidation were investigated. The initial rates increased almost linearly with catalyst loading. The apparent orders of reaction with respect to hydrogen peroxide and propene were found to be 0.67 (0.17-0.70 wt %) and 0.63 (0.3-0.8 bar), respectively. The apparent activation energy was found to be 25.8 kJ mol -1 . Methanol content in the solvent was shown to have a dual influence on the reaction rate, enhancing the solubility of propene and inhibiting the epoxidation reaction by competitive adsorption.

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Propene oxide is an important chemical intermediate and titanium silicalite (TS-1) has been widely investigated as a promising catalyst for the direct epoxidation of propene with ex-situ or in-situ produced hydrogen peroxide as an oxidant. In order to clarify the effects of the kind of precious metal and treatment process in the catalyst preparation on the propene epoxidation and the hydrogen peroxide decomposition, TS-1 was impregnated with gold and palladium via drying, calcination and reduction and the experiments to check its catalytic performance were conducted in a gas aspirating autoclave reactor in the absence of mass transfer limitations. The presence of precious metals vigorously catalyzed the side reactions and hydrogen peroxide decomposition. Some of the precious metal containing TS-1 catalysts showed high initial rates but there was no catalyst with a propene oxide yield after 5 h reaction time comparable to TS-1 alone because of the enhancement of side reactions by precious metals. The significant decline in the selectivity to propene oxide over the dried precious metal containing TS-1 catalysts was attributed to the leaching of precious metals into the reaction medium. Palladium containing TS-1 showed exceptionally high decomposition of hydrogen peroxide. Reduction and calcination increased the decomposition by forming metallic gold and palladium. Homogeneous dispersion of gold nanoparticles was achieved by a sol immobilization method which led to a decrease of propene oxide selectivity and an increase of hydrogen peroxide decomposition.

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Heterogeneous catalytic epoxidation of propene to propene oxide with hydrogen peroxide was investigated in a monolith and a confined Taylor flow (CTF) reactor in which titanium silicalite (TS-1) catalyst was coated on the walls. The influence of gas and liquid superficial velocity on the hydrodynamic characteristics of the monolith and CTF reactor was also investigated under Taylor flow regime at atmospheric and high pressure. The reactors showed distinctly different hydrodynamic properties which in turn led to different performance for propene epoxidation. The production rate of propene oxide was higher in the monolith reactor due to its larger catalyst coating area, larger mass-transfer surface area and more frequent recycling of liquid flow. A variation of reactor column structures confirmed that the propene oxide production was highly dependent on the catalyst coating area and cross-sectional area of the reactor column. High operating pressure made a significant impact on the length of Taylor bubbles and the propene oxide production rate was found to increase in proportion to the operating pressure.