Catalytic gasification of coal using eutectic salts: reaction kinetics with binary and ternary eutectic catalysts

Abstract

Kinetic studies of the catalytic steam gasification of Illinois No. 6 coal were carried out using binary and ternary eutectic salt mixtures in a fixed-bed reactor. The effects of major process variables such as temperature, pressure, catalyst loading and steam flow rate were evaluated for the binary 29% Na 2CO 3–71% K 2CO 3 and ternary 43.5% Li 2CO 3–31.5% Na 2CO 3–25% K 2CO 3 eutectic catalyst systems. A Langmuir–Hinshelwood rate expression was developed to explain the reaction mechanism for steam gasification using the binary and ternary catalysts. The activation energy of the ternary catalyst (98 kJ/mol) was less than that of the binary catalyst (201 kJ/mol) or single salt such as K 2CO 3 (170 kJ/mol). The molar heats of adsorption for the ternary and binary catalysts were exothermic and about 180 and 92 kJ/mol, respectively. The molten nature of the ternary eutectic at the gasification temperatures and its lower activation energy favored higher gasification rates compared to the single and binary alkali metal salts.