Propane combustion over Pt/Al2O3 catalysts with different crystalline structures of alumina

Abstract

-The effects of the crystalline phases (α-Al2O3, κ-Al2O3, δ-Al2O3, θ-Al2O3, η-Al2O3, and γ-Al2O3) of the alumina support of Pt/Al2O3 catalysts on the catalyst activity toward propane combustion were examined. The catalysts were characterized by N2 physisorption, CO chemisorption, temperature-programmed reduction (TPR), temperatureprogrammed oxidation (TPO), transmission electron microscopy (TEM), and infrared spectroscopy (IR) after CO chemisorption. The Pt dispersion of the catalysts (surface Pt atoms/total Pt atoms), measured via CO chemisorption, was more dependent on the crystalline structure of alumina than on the surface area of alumina. The highest catalytic activity for propane combustion was achieved with Pt/α-Al2O3, which has the lowest Brunauer, Emmett, and Teller (BET) surface area and Pt dispersion. The lowest catalytic activity for propane combustion was exhibited by Pt/γ-Al2O3, which has the highest BET surface area and Pt dispersion. The catalytic activity was confirmed to increase with increasing Pt particle size in Pt/δ-Al2O3. The apparent activation energies for propane combustion over Pt/α-Al2O3, Pt/κ-Al2O3, Pt/δ-Al2O3, Pt/θ-Al2O3, Pt/η-Al2O3, and Pt/γ-Al2O3 were determined to be 24.7, 21.4, 24.3, 22.1, 24.0, and 19.1 kcal/mol, respectively.