Non-oxidative dehydrogenation of propane to propene over precious-metal free anatase titania

Khan, Iqtidar Ali
Propylene is a versatile compound in the petrochemical industry. Albeit, it is merely used as a final product, propylene serves as a building block for the production of a wide variety of chemicals such as polypropylene, cumene, isopropanol, propylene oxide, and acetone, to name a few. Conventionally, propylene is produced as a by-product during fluid catalytic cracking (FCC) and steam cracking (SC) of oil fractions. However, the supply-demand gap of propene produced from these processes and their economic/environmental limitations have led to alternative greener propene production routes such as non-oxidative propane dehydrogenation (PDH). The PDH technology has been commercialized and applied on a wide scale where alumina-supported chromia or platinum catalysts are used. However, the toxicity of chromia and the high cost of platinum has surged interest in the use of low-cost and environmentally benign catalysts. Bulk metal oxides such as zirconia, titania, and alumina are the quintessence of such materials and have shown promising results for non-oxidative propane dehydrogenation. Over these materials, coordinatively unsaturated cations located near oxygen vacancies(defects) are demonstrated to be the active sites for C-H activation. With the aforementioned fact, we aimed to synthesize non-toxic, non-noble, and dopant-free titania for non-oxidative propane dehydrogenation. Synthesized catalysts were characterized by Nitrogen physisorption, Raman spectroscopy, Thermal Gravimetric Analysis(TGA), Temperature programmed reduction (TPR), X-ray diffraction, UV-visible spectroscopy, X-ray Photoelectron spectroscopy(XPS) and in-situ pyridine DRIFT. In our study, we have demonstrated that the oxygen vacancies(defects) and surface properties of titania can be tuned during the in-situ synthesis of titania by varying the volume (0,2,6,8 and 10mL) of 1M HCl. The propane conversion and the yield of propene showed the volcano-shaped curve with respect to the volume of HCl added during the sol-gel synthesis of titania. Titania synthesized with 6mL addition of HCl showed the best catalytic performance in comparison with other synthesized titania samples. Over 99% selectivity was achieved for our best-performing catalyst tested in a differential regime. Our best-performing catalyst also revealed industrial relevance by showing a high initial propane conversion(~25%) with high propene selectivity(~96%).


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Citation Formats
I. A. Khan, “Non-oxidative dehydrogenation of propane to propene over precious-metal free anatase titania,” M.S. - Master of Science, Middle East Technical University, 2022.