Study on synergistic catalysis of ex-situ catalyst and in-situ clay in aquathermolysis of water-heavy oil-ethanol at low temperature

There are so many studies on aquathermolysis for enhancing heavy oil recovery, but almost all of them are limited to the catalytic effect of an external catalyst on the reaction, ignoring its possible interaction with in-situ inorganic minerals after entering the reservoir. Therefore, we prepared and characterized ex-situ and in-situ catalyst compounds using metal complexes prepared from salicylic acid and chloride salts as ex-situ catalysts and bentonite (B) as in-situ carrier catalyst. Their synergistic catalytic viscosity reduction performance in aquathermolysis was investigated. [email protected](II)L appears to be the most effective synergistic combination of an ex-situ catalyst with copper ions and ligands Cu(II)L and in-situ compound bentonite. Under the optimized conditions, 0.2 wt% [email protected](II)L with 30 wt% ethanol at 180 °C for 4 h, the viscosity was decreased by 91.5 %. The temperature was about 70 °C lower than the traditional reaction temperature. The results of TGA and DSC of the heavy oil show that the macromolecular substances in the heavy oil had cracked into small molecules with a low boiling point after the reaction. The amounts of resin and asphaltene decrease, and those of saturated and aromatic HC increase. In addition, GC–MS analysis of polar substances dissolved in water after reaction shows that [email protected](II)L can help to decrease the polar substances in heavy oil and reduce the aromaticity of polar substances. In addition, model compounds were used to study the reaction mechanism. GC–MS analysis results showed that CC, CN and CS bonds were broken during the reaction, thereby reducing the viscosity of the heavy oil.