Non-oxidative dehydrogenation of propane and isobutane over unconventional ZrO2- or TiO2-based catalysts: Understanding the role of coordinatively unsaturated metal cations

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Non-oxidative dehydrogenation of propane and isobutane to the corresponding olefins are established large-scale processes that, however, faces challenges, particularly in catalyst development, which are toxicity of chromium compounds and high cost of platinum. To address these challenges, this proposal will deal with development of environmentally friendly and cost-efficient catalysts based on bulk materials (ZrO2 and TiO2). In comparison with typical supported catalyst, lattice defects on the surface of such catalysts are the catalytically active sites. They are coordinatively unsaturated metal cations (Mecus = Zr or Ti) located at oxygen vacancies. The main fundamental questions to be answered in this proposal are the effects of the host oxide (ZrO2 vs TiO2) and the metal oxide promoter (e.g. K2O, La2O3, or CeO2) used for creating anion vacancies in the host oxides on (i) formation of surface Mecus in the host oxides and (ii) the activity, on-stream stability and particularly selectivity (including coke formation) of Mecus in dehydrogenation of propane and isobutane. The alkanes were chosen both from fundamental and applied viewpoints. In comparison with propane/propene, isobutane and particularly isobutene (the desired product) can be isomerized to n-butane and linear butenes respectively. Therefore, it is important to elucidate if such isomers may open another pathways for formation of cracking products and carbon deposits. In order to understand the fundamentals of catalyst functioning on a level as elementary as possible, we will follow a complementary approach combining steady-state and transient catalytic tests as well as operando catalyst characterization with Density Functional Theory (DFT) calculations. In particular, the proposal is intended i) to establish structure-reactivity-selectivity relationships, which are the key factor for rational catalyst design as well as ii) to provide guidelines for an optimal production of propene and isobutene. The knowledge derived would permit to improve the efficiency of functionalization of raw materials in terms of saving natural resources and reducing harmful environmental impacts.