Structural evolution and catalytic mechanism of the non-thermal plasma modified Pd/Al2O3 in C2H6 catalytic combustion

Abstract

Catalytic combustion of C2H6 at equivalence ratios of 1.0 and 1.4 over non-thermal plasma (NTP) modified Pd/Al2O3 was studied experimentally to examine the effect of O2 and N2 plasma on the catalyst activity and physico-chemical property. C2H6 conversion, chemical product distribution and selectivity were taken into account to evaluate the performance of modified catalysts in C2H6 oxidation at 200–500 ℃. The results showed that the plasma modification had suppressive effects on the activity of Pd/Al2O3. When compared to Pd/Al2O3, T30 for the modified Pd/Al2O3 were shifted to higher temperatures by approximately 30–50 ℃. For catalysts modified by plasma, significantly more CO was formed in the C2H6 combustion at high temperature region. Moreover, the structure, morphology and chemical states of Pd/Al2O3 after modification were thoroughly analyzed with the means of N2 adsorption–desorption, XRD, XPS and SEM. The surface area of modified catalysts decreased, resulting in the activity degradation. The leaching of Pd species and transform of γ-Al2O3 to θ-Al2O3 were observed after the NTP treatment with highly energetic electrons. It should to be highlighted that the reduction of Pd2+ to Pd0 by NTP modification on the catalyst surface from XPS analysis. The NTP had the potential to reduce catalysts while employing oxidizing or inert gases.