A comparison of the features of catalysis in coal gasification.

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The catalytic properties of three catalysts, potassium, calcium and nickel, in coal char gasification were compared using Blair Athol char devolatilized at 750°C and steam-helium or -hydrogen as the gasifier. The three catalysts behaved differently in reaction pattern, dependence on the amount of the catalyst and composition of the products. In steam-helium, the activities of the calcium and nickel decreased more rapidly than those of the potassium. The catalytic conversion with the nickel was almost proportional to the amount of the nickel, while that with the calcium slightly depended on its amount and this is ascribed to its poor dispersion on char surface. The rate of the nickel-catalyzed gas-ification in steam-hydrogen increased gradually with time until a maximum at about 25% burn-off and then decreased.<BR>With a demineralized char, smaller amount of potassium was effective, as compared to the untreated char, probably due to the absence of the deactivating action of mineral matters. In the initial stage of this reaction, carbon monoxide was the main product, whereas carbon dioxide was the main one in the later stage. This is taken to indicate that potassium salt catalyzed the formation of carbon dioxide directly from carbon and steam, under the differential reaction conditions.
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