The properties and catalytic performance of PtIn/Mg(Al)O catalysts for the propane dehydrogenation reaction: Effects of pH value in preparing Mg(Al)O supports by the co-precipitation method

• Co-precipitation pH value influences the properties of PtIn/Mg(Al)O-pX catalysts.
• Co-precipitation pH value markedly influences the catalytic performance.
• PtIn/Mg(Al)O-p8 catalyst exhibits the best catalytic performance.
• Propane conversion of PtIn/Mg(Al)O-p8 remains above 50% for 28 h reaction.

PtIn/Mg(Al)O-pX catalysts were prepared with co-precipitation method at different pH values (X = 6–12), with the aim of investigating the effect of pH value on their catalytic performance for the propane dehydrogenation reaction. It was found that the co-precipitation pH value could strongly influence the crystalline phase, the specific surface area, the surface morphology, the distribution of surface acidity, the reduction properties of the metal phase, the surface chemical state, the distribution of metal particles, and coke formation, giving rise to different catalytic performance. All the results reveal that the catalyst prepared at pH 8 shows the best catalytic performance; it possesses the primary crystal phase of periclase (MgO) and the highest specific surface area of support, the lowest fraction of strong acidic sites and In0 species, the strongest interaction between the metal phase and support, the highest Pt dispersion (41.6%), the best distribution of Pt particles with the smallest Pt particle size (1.8 nm), and the lowest coke amount. Furthermore, the highest once-though yield of 0.37 mol propylene can be obtained over PtIn/Mg(Al)O-p8, in which 0.60 mol propane is consumed in a whole dehydrogenation reaction period (28 h).

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