Flame Synthesis of Zr/Zsm-5 Catalysts with Tunable Acidity for the Oxidative Dehydrogenation of Propane to Propene

A series of functional Zr/ZSM5 nanocatalysts with different ratios (4:0, 4:1, 1:1, 1:4 and 0:4) were synthesized in a premixed methane flame coupled with a pulse spray evaporation system for the oxidative dehydrogenation of propane (ODHP) to propene. The interaction between Zr and ZSM5 has significantly impacted the physicochemical surface and acidity properties. With increasing the ratio of zirconium in ZSM5, the XRD and BET analysis showed an increase in crystallite sizes and a decrease in specific surface area due to the synergetic effect between Zr and ZSM5. The SEMEDS analysis shows coated layers consisting of homogeneous dispersion of irregular nano-sized morphology of Zr particles. XPS results revealed an increase in the lattice oxygen on the Zr modified ZSM5(1:4) compared to pure ZSM5. The NH3TPD analysis indicated that the distribution of the acidic sites on ZSM5, tuned to medium and strong acid sites distribution on the catalyst surface with the increment of Zr content in ZSM5, which promoted the propene selectivity and suppresses the formation of carbon oxides at high propane conversion. The modified Zr/ZSM5 (1:4) exhibited the best performance yield having a high reaction rate, low activation energy, and the highest stability among the prepared catalysts, with 57.19% propane conversion and 75.54% selectivity to propene. This work provides a promising strategy for tuning the surface acidity of ZSM5 with Zr by flame synthesis as an efficient catalyst for ODHP applications