Gasification of carboneous materials by carbon dioxide with molten carbonate catalysts

Reactions of graphite, activated carbon and lignin with carbon dioxide are carried out at 973 K by using alkali metal carbonates (m.p. 891 similar to 1,164 K) and eutectic mixtures of these compounds (m.p. 669 similar to 787 K) as catalysts. The reaction occurrs by mixing catalyst with graphite physically when the melting points of the catalysts are lower than the reaction temperature. The gasification rates of graphite and activated carbon by this physical mixing method are almost the same as those of the impregnation method of the catalyst. However, the reaction with catalyst using the physical mixing method did not proceed when the melting points of the catalysts are higher than the reaction temperature. Repeated use of the molten catalyst is also studied to investigate the possibility of continuous gasification of carboneous materials. After the activated carbon(or lignin) is consumed in a batch reactor, the same amount is added in the reactor containing the catalyst and the reaction starts again. It is found that the eutectic molten catalyst can be reused without any loss of catalytic activity by repeating this operation. Furthermore, the co-existing effect of molten catalyst with Ni catalyst is investigated. The reaction rate at 773 K in the case of co-existing these catalysts is 4.3 times of Ni catalyst.