Group VIII metals effects on lignite pyrolysis and char gasification with Ca-based catalyst

Group VIII metals Fe, Co and Ni have various effect on catalytic performance for lignite pyrolysis and char gasification. In this work, Fe, Co and Ni were introduced into Ca-based catalysts to modulate the catalytic activity for lignite pyrolysis and char conversion. 7Ca-2Ni, 7Ca-2Co and 7Ca-2.5Fe showed the highest activity in the catalytic pyrolysis. Ca facilitated the conversion of heavy tar to light tar, while transition metals promote the cleavage of the C-H, C-C, and C = O bonds, further cracking the light tar to obtain gas products. 7Ca-2Co showed high activity in char steam gasification. The carbon conversion of the catalyst increased from 52.14 % to 94.26 %, and the hydrogen production was 84.45 mmol/g. The introduction of Fe, Co and Ni can gain electron from Cabased catalysts and Ca-Co showed the optimized electronic structure. The optimized d-band center was conducive to reactants adsorption as calculated by density functional theory calculations. The S element adsorption energy on Ca-Co can protect the activity sites form S poisoning to improve the activity. This work provides guidance for regulating the distribution of pyrolysis products by regulating the electronic structure of catalysts.