Structural effects in the reaction between carbon dioxide and coke doped with various potassium bearing catalytic precursors

Abstract

The rate of reaction between carbon dioxide and coke with and without the additions of KCN, KOCN, and K2CO3 was studied using thermogravimetry. Since both potassium and carbon are lost during the reaction, the concentration of potassium in the coke samples was determined as a function of the extent of the reaction by atomic absorption spectrometry. The changes in the specific surface area due to the reaction were studied by the nitrogen adsorption technique. The changes in the pore structure of coke were investigated by mercury porosimetry and scanning electron microscopy. The distribution of potassium in the coke structure was examined as a function of the reaction time by the energy dispersion X-ray technique. Furthermore, since sulfur is known to influence the rate of the C-CO2 reaction, the sulfur content of the coke samples with or without the addition of catalytic precursors was monitored as a function of the extent of reaction. The influences of the structural parameters and the concentration of potassium on the rate of the coke-CO2 reaction were determined. The rate data were analyzed on the basis of a structural model to examine the contributions of the chemical reaction and the pore diffusion on the overall rate of the coke-CO2 reaction.