Chemical Engineering Journal, Vol.323, 160-170, 2017
Synergistic catalytic effect of (Ce,Cr)(x)O-2 and HZSM-5 for elimination of chlorinated organic pollutants
A series of y(Ce,Cr)(x)O-2/HZSM-5 composite materials (with different mass ratios of.(Ce,Cr)(x)O-2 to the HZSM-5 zeolite) are firstly constructed via traditional deposition-precipitation method, and then evaluated for eliminating low concentration chlorinated organic pollutants with different molecule structures. Compared to single (Ce,Cr)(x)O-2 or HZSM-5, the synergistic catalytic effect between (Ce,Cr)(x)O-2 and HZSM-5 improves the destructive efficiency of y(Ce,Cr)(x)O-2/HZSM-5. This is due to that the abundant strong/weak acid centers on HZSM-5 firstly favor the adsorption and dechlorination of the chlorinated organic molecules, while the superior oxidation property of (Ce,Cr)(x)O-2 promotes the oxidative destruction of these CIVOCs (chlorinated volatile organic compounds) and the by-products, and also suppresses the surface deposition of chlorine and carbon species. Particularly, the (Ce,Cr)(x)O-2/HZSM-5 catalyst with the same weight of (Ce,Cr)(x)O-2 and HZSM-5 (50%:50% for (Ce,Cr)(x)O-2:HZSM-5) exhibits the highest oxidative activity, since its appropriate concentration of acid and oxidative sites can play to the largest degree. Moreover, adding slight benzene or water into the reaction system slightly decreases the catalytic activity owing to the competitive adsorption effect on the active centers, whereas water reduces the formation of byproducts, since it can accelerate the eliminating of the surface chlorine species. The preferable catalytic activity and durability in the continuous long-time reaction reveals that the (Ce,Cr)(x)O-2/HZSM-5 catalyst deserves more attention and is potential for industrial application to eliminate the chlorinated organic pollutants. (C) 2017 Elsevier B.V. All rights reserved.
Keywords:Catalytic elimination;Chlorinated organic pollutants;HZSM-5 zeolite;CeO2-Cr2O3;Synergistic catalytic effect