Performance of H-ZSM-5-supported bimetallic catalysts for the combustion of polluting volatile organic compounds in air

摘要

The performance of H-ZSM-5-supported bimetallic catalysts with chromium as the base metal in the combustion of ethyl acetate and benzene is reported. A reactor operated from 100 to 500 degrees C at a gas hourly space velocity (GHSV) of 32 000 h(-1) was used for study of the activity. A combination of 1.0 wt% chromium and 0.5 wt% copper yielded a catalyst (Cr1.0Cu0.5/Z) with improved conversion and carbon dioxide yield. Cr2O3 (Cr3+) and CuO (Cu2+) were the predominant metal species in the catalyst. In agreement with the Mars-van Krevelen model, improved reducibility of Cr3+ in the presence of Cu2+ led to an improvement in activity. The copper content in Cr1.0Cu0.5/Z also favored the formation of deep combustion products. Condensation and subsequent growth of coke precursors in the catalyst pores led to the formation of a softer and less aromatic coke fraction while dehydrogenation activity on acid sites formed a harder and more aromatic coke fraction. The use of Cr1.0Cu0.5/Z favored the formation of lower molecular weight intermediates, leading to reduction in formation of softer coke. (c) 2005 Society of Chemical Industry.