Catalytic Steam Gasification of Coals Oxidized by Nitric Acid

Abstract

In order to find a better method of catalyst addition for gasification of coals, some new or improved methods have been developed by our laboratory.As one of them, nickel and potassium carbonate were impregnated on the surfaces of four coals oxi-dized by nitric acid at 40t.The amount of nickel actually loaded on oxidized coals was much larger than on original coals.The better dispersion of nickel particles on the char surface of oxidized Leopold coal was observed by scanning electron microscope.An eight-fold increase in the concentration of carboxyl functional groups was obtained on the oxidized coal.Therefore the better dispersion is due mainly to the increased amount of nickel ion combined with these groups.The rates of steam gasification of the catalyst-impregnated coals were much higher with oxidized coals than with original coals.For example, when 2.0% of catalyst metal was impregnated on Shin-Yubari coal, the ratio of initial gasification rate with the oxidized coal to that with the original one at 750t was 2.0 for nickel and 3.8 for potassium carbonate.The finely dispersed catalyst on oxidized coals may lead to the higher gasification rate.An extraordinary high activity of nickel catalyst was observed when it was impregnated on coals which had a large amount of carboxyl groups.