Effects of clay minerals on the low-temperature oxidation of heavy oil

Abstract

In situ combustion (ISC) is an efficient method to recover heavy oil, in which low-temperature oxidation (LTO) is an important process. A fixed-bed reactor was used to conduct ramped temperature oxidation experiments on a mixture of heavy oil from China, silica and clay minerals, including montmorillonite, kaolinite, illite and chlorite. The four clay minerals promoted the LTO of heavy oil, which was reflected in the increase in the total amount of O2 consumption with the decrease in the peak temperature and the change in the composition and yield of gas, liquid and solid products. The total amounts of CO and CO2 release increased, and the peak temperature decreased. The total amount of hydrocarbons in the gas phase decreased, whereas the peak temperature and main components didn’t change. The presence of clay minerals showed little effect on the composition of produced oil, whereas the presence of montmorillonite decreased the yield of produced oil. The yield and O/C ratio of coke increased, the heat value of coke decreased and the oxidation activity of coke improved in the presence of clay minerals. Montmorillonite showed the most notable effect. The mechanism of the effects of clay minerals on the LTO of heavy oil was analyzed by combining the change in the distribution proportion of O and C in products. Montmorillonite had large specific surface area and adsorption capacity and catalyzed decarbonylation, decarboxylation and polycondensation. The other three clay minerals mainly affected the LTO of heavy oil through the catalysis of decarbonylation, decarboxylation and polycondensation.