Total oxidation of propane over Co3O4-based catalysts: Elucidating the influence of Zr dopant

A series of Zr-doped CoO catalysts (x% Zr-CoO), prepared by citrate sol-gel method with a low doping amount of zirconium, was applied in the catalytic oxidation of 1000 ppm propane at a weight hourly space velocity of 40,000 mL g h. Different techniques were used to characterize the catalysts. The results showed that the physicochemical properties and catalytic performances of the x% Zr-CoO catalysts were significantly influenced by the addition of zirconium. Only a small part of Zr could be doped into the CoO lattice and the spare Zr would prefer to aggregate on the surface to form zirconium oxide. In the x% Zr-CoO catalysts, Zr disordered CoO spinel is formed by entering into the CoO lattice and forming Co-O-Zr species, resulting in smaller CoO crystallite size, larger specific surface area, better low-temperature reducibility, higher surface Co concentration, and higher content of surface oxygen vacancies and active oxygen species. The best performance was achieved on 1% Zr-CoO for propane oxidation, with 90% propane conversion at 241 °C. The most active catalyst showed excellent performance in toluene and propene oxidation as well. Propane reaction tests, carried out without oxygen in the gas stream, indicated the promoting effect of the low amount of Zr on the oxygen mobility of x% Zr-CoO catalysts. Durability tests of propane oxidation showed that stable conversion could be achieved over 1% Zr-CoO, thus being a potential active catalyst for practical application.