Significant parameters in the catalysed CO2 gasification of coal chars

Alkali and alkaline earth carbonates have been used to catalyse the C0₂ gasification of coal chars prepared by pyrolysis of Illinois No.6 coal. This study found that alkaline earth carbonates are fair gasification catalysts, though throughputs are insensitive to loadings in the range of 5–20 wt%. The order of efficacy is Ba > Sr > Ca. Alkali carbonates are excellent catalysts, with throughputs showing a dependence on loadings and atomic number. In particular, at high loadings (20 wt%) the order is Cs > K > Na > Li. As kinetic parameters for the alkali carbonate catalysed Boudouard reaction with coal chars differ significantly from those for graphites, an alternative redox cycle mechanism has been proposed involving an alkali hydride intermediate.