The effect of free radical initiator in promoting aquathermolysis of heavy oil under mild conditions

Aquathermolysis is a pivotal process in the recovery of heavy oil. The key issue is that the high temperature required for the reaction needs to be further reduced to enhance energy efficiency. In this study, a free radical initiator was used to overcome this problem. The promoting effects of introducing di- tert -butyl peroxide (DTBP) into the aquathermolysis system of Shengli heavy oil in the temperature range of 150–310 °C were investigated. Oil samples and asphaltenes were characterized before and after the reaction, respectively. The results revealed that DTBP could enhance the reactivity of both cracking and condensation reactions . It exhibited excellent performance in upgrading heavy oil at 250 °C and 310 °C. Compared with the experiment without DTBP, the relative viscosity reduction ratio increased by 9.64 %, while the asphaltene and resin contents relatively decreased by 28.34 % and 6.78 % at 250 °C with only 0.2 wt% DTBP added. However, at 150 °C and 210 °C, the addition of DTBP resulted in condensation progression, which proved detrimental to the viscosity reduction of heavy oil. Through an in-depth analysis of the hydrogen supply capacity of hydrogen donors and the structure changes of asphaltenes, the possible reaction mechanism of DTBP was discussed. Finally, these findings provide a comprehensive understanding of the performance of DTBP and cast a new insight into the aquathermolysis of heavy oil.