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

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 O-2 and N-2 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 degree celsius. The results showed that the plasma modification had suppressive effects on the activity of Pd/Al2O3. When compared to Pd/Al2O3, T-30 for the modified Pd/Al2O3 were shifted to higher temperatures by approximately 30-50 degree celsius. 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 N-2 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 gamma-Al2O3 to theta-Al2O3 were observed after the NTP treatment with highly energetic electrons. It should to be highlighted that the reduction of Pd2+ to Pd-0 by NTP modification on the catalyst surface from XPS analysis. The NTP had the potential to reduce catalysts while employing oxidizing or inert gases.