Catalytic reduction of NOx by biomass-derived activated carbon supported metals

In this study, to prepare a series of activated carbon-supported metals for the catalytic reduction of NOx to N-2 in excess O-2, activated carbons derived from lignocellulosic and herbaceous biomasses were selected as the reducing agents, and alkali and transition metals were used as the catalytic active phases. The effects of the type of biomass, carbonization temperature and catalyst composition on NOx reduction efficiency were analyzed in a fixed-bed flow reactor. The results showed that two temperature regimes are present for the NOx-carbon reaction: at temperatures below 250 degrees C, the NOx adsorption process on the carbon surface was predominant, whereas true NOx reduction by carbon occurred at temperatures above 250 degrees C, producing N-2, CO2 and CO. The influence of the carbonization temperature on carbon reactivity depended on the effect of the carbonization temperature on the carbon surface area and the reduction of the metal species on carbon. All studied metals catalyzed both NOx and O-2 reduction by carbon, and potassium could strongly enhance the C-NOx reaction without substantial carbon consumption by O-2. Moreover, the potassium supported by sawdust-derived activated carbon exhibited higher selectivity and capacity towards NOx reduction than did its previously reported coal-derived counterparts. These properties were ascribed to the high dispersion of the active potassium species on the carbon surface, as observed through the comparison of X-ray photoelectron spectroscopy and powder X-ray diffraction results for the carbons made from biomass and coal-based precursors. (C) 2018 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.