Mechanistic and kinetic insight into catalytic oxidation process of heavy oil in in-situ combustion process using copper (Ⅱ) stearate as oil soluble catalyst

Abstract

In this study, copper (Ⅱ) stearate was proposed as oil-soluble catalysts for catalyzing heavy oil oxidation in in-situ combustion (ISC) process to improve the efficiency of ISC for heavy oil recovery. Its catalytic mechanism and kinetics were deeply investigated by joint use of TG-FTIR, autoclave experiments, FESEM-EDX, and XPS, etc., together with isoconversional kinetic methods. We find that the addition of copper (Ⅱ) stearate initiated both efficient homogenous and heterogenous catalytic oxidation/combustion process of heavy oil. In low-temperature range, copper (Ⅱ) stearate (before its full decomposition) played a homogenous catalytic role in low temperature oxidation (LTO), and in high-temperature range, in-situ formed CuO nanoparticles (after the full decomposition of copper (Ⅱ) stearate) played a heterogenous catalytic role in the formation and combustion process of fuel (coke-like residues) in fuel deposition (FD) and high temperature oxidation (HTO) stages. Specifically, the addition of copper (Ⅱ) stearate significantly reduced the values of Eα of all reaction stages (LTO, FD, and HTO), especially at the later stage of LTO, FD and the beginning of HTO (the maximum values of Eα were decreased from about 500–600 KJ/mol to 300–400 KJ/mol), decreased the energy required to overcome reaction barriers, and improved the formation rate and quality of coke-like residues, which thus promotes the formation of coke-like residues and their combustion a more continuous process. Such a superior catalytic effect makes copper (Ⅱ) stearate have a great potential in improving efficiency of ISC process for heavy oil recovery.