Formation, fates and roles of catalytic precursors generated from the K2CO3-carbon interactions in the K2CO3-catalyzed CO2 gasification of coal char.

A study was carried out in both inert and CO 2 atmosphere to investigate the interaction mechanism of K 2 CO 3 with graphite and coal char during the catalytic gasification of coal char. The formation of K 2 CO 3 catalytic precursors was identified by using series of different techniques. The results obtained in an inert atmosphere show that the interaction between K 2 CO 3 and carbon readily took place at low temperature. For the K 2 CO 3 loaded graphite, the intermediate of C n K clusters formed by the interactions of K 2 CO 3 with carbon prevented the evaporation of K at low temperature. At temperatures above 800 °C, however, the C n K clusters were unstable, and decomposed to release K through vaporization. On the contrary, for the K 2 CO 3 loaded demineralized coal char, due to the presence of oxygen groups, K was tightly bonded to carbon during heating, forming a complex precursor containing O and K with high thermal stability. The reaction pathway of carbon-K 2 CO 3 interactions in an inert atmosphere are proposed for both char and graphite. The results of DRIFTs experiment suggest that CO 2 is chemisorbed by the K- catalytic precursors during CO 2 gasification to form potassium phenolate species and a covalently bound carbonate group (dimethyl carbonate). It is believed that these species act as active intermediates in the gasification process. [ABSTRACT FROM AUTHOR]