Regeneration Of Pd/Ac Catalysts Deactivated By Organic Pollutants In Dielectric Barrier Discharge Plasma

Pd/AC catalysts are widely used in chemical industry such as catalytic hydrogenation and wastewater treatment processes due to its good catalytic properties. Impurties in reactants and intermediates can be adsorbed by Pd/AC catalysts during reaction processes, which might cause deactivation of Pd/AC catalysts. Pd/AC catalysts decativated by diphenyl were chosen as model deactivated catalysts in this research. To regenerate deactivated Pd/AC catalyst, Dielectric barrier discharge (DBD) was employed. DBD could produce many active species including hydroxyl radicals, hydrogen peroxide, ozone and UV etc. These strong oxidants are able to degrade the adsorbates on the surface of Pd/AC catalysts and thus regenerate catalysts. Regeneration of Pd/AC catalysts by DBD has advantages compared with traditional methods such as low energy consumption, short regeneration time, high regeneration efficiency and less equipment requirments. The operation parameters optimization of Pd/AC catalysts regeneration by DBD as well as the regeneration mechanisms were studied in this paper.The results indicated that Pd/AC catalysts regeneration rate achieved95%after30min treatment under the condition of input voltage of9kV, frequency of8kHz and in wet oxygen atmosphere with flow rate of60mL/min. Nitrobenzene degradation efficiency was87%in catalytic ozonation reaction catalyzed by Pd/AC catalyst which was regenerated under the optimized condition. The regeneration efficiency of Pd/AC catalysts decreased slightly as regeneration times increased. After3times regeneration, the regeneration efficiency was still around88%, which proved good stability of DBD catalyst regeneration process.The surface morphology, surface area and organic compounds were characterized by SEM, BET and TG respectively. The results showed that the weight of organic pollutant on Pd/AC cataysts was13%the weight of catalysts, which fouled the pores stucture of Pd/AC catalysts. The mineralization rate of organic compounds on Pd/AC catalysts was83.7%(calculated by concentration of CO2 generation). Furthermore, concentration of O3and plasma emission spectra during DBD process were also detected. The regeneration efficiency attributed to UV, heat and ozone solely was3%,15.9%and25.6%, respectively, indicated that radicals with strong oxidation ability produced in DBD process was the main factor for Pd/AC catalysts regeneration.