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The partial oxidation of propane and the mechanism of selective catalytic reduction (SCR) of NO by propane over Ga2O3/Al2O3 in excess of O2 have been investigated using in situ Fourier transform infrared spectroscopy. An optimized Ga2O3/Al2O3 catalyst shows high activity and efficiency of the reducing agent propane (100% conversion of NO at 623 K, GHSV: 10,000 h(-1)). One molecule of propane converts more than 4 NO molecules to N2. The reaction starts with the partial oxidation of C3H8 by O2 and carboxylates (acetate, formate) are formed on the catalyst surface above 573 K. This oxidation represents the rate-determining step of the SCR reaction. These surface carboxylates represent a dominating intermediate and (easily) react with (adsorbed) NO forming nitrogen-containing organic species. The latter are proposed to react with NO to form N2. Total oxidation of propane was enhanced at temperatures above 773 K leading to decreased reductant efficiency. Surface nitrite and nitrate species can also be observed, but they were found to be spectators only. This could be concluded from the electron balance (conversion of propane relative to NO) and from the relative rates of the single reaction steps. On the basis of these investigations and stoichiometric calculations, a conclusive reaction mechanism is proposed.

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The microkinetic reaction network of the oxidative dehydrogenation of ethane to ethene over Li/Dy/Mg/O and Li/Dy/Mg/O/Cl catalysts was investigated. With Li/Dy/Mg/O catalysts, the reaction kinetics is compatible with a heterogeneous-homogeneous radical based reaction mechanism. The formation of ethyl radicals on the surface is concluded to be the rate-determining step. In contrast, the reaction kinetics for Li/Dy/Mg/O/Cl is in line with a purely surface catalyzed reaction mechanism. However, also in this case, alkane activation is rate determining.

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