Catalytic thermolysis is considered to be an effective process for viscosity reduction, the conversion of high-molecular components of oil (resins and asphaltenes) into light hydrocarbons, and the desulfurization of hydrocarbons. In this paper, we conducted non-catalytic and catalytic thermolysis of a heavy oil sample isolated from the Ashalcha oil field (Tatarstan, Russia) at a temperature of 250 °C. Fullerene C60 nanoparticles were applied to promote selective low-temperature thermolytic reactions in the heavy oil, which increase the depth of heavy oil upgrading and enhance the flow behavior of viscous crude oil. In addition, the influence of water content on the performance of heavy oil thermolysis was evaluated. It was found that water contributes to the cracking of high-molecular components such as resins and asphaltenes. The destruction products lead to the improvement of group and fractional components of crude oil. The results of the experiments showed that the content of asphaltenes after the aquatic thermolysis of the heavy oil sample in the presence of fullerene C60 was reduced by 35% in contrast to the initial crude oil sample. The destructive hydrogenation processes resulted in the irreversible viscosity reduction of the heavy oil sample from 3110 mPa.s to 2081 mPa.s measured at a temperature of 20 °C. Thus, the feasibility of using fullerene C60 as an additive in order to increase the yield of light fractions and reduce viscosity is confirmed.

The high viscosity of heavy oil is the main challenge hindering its production. Catalytic thermolysis can be an effective solution for the upgrading of heavy oil in reservoir conditions that leads to the viscosity reduction of native oil and increases the yield of light fractions. In this study, the thermolysis of heavy oil produced from Ashalchinskoye field was carried out in the presence of FеР and Al(H2PO4) nanocatalysts at a temperature of 250 °C in N2 gas environment. It was shown that Al(H2PO4)3 and FeP catalysts at a concentration of 0.5% significantly promoted the efficiency of the heavy oil thermolysis and are key controlling factors contributing to the acceleration of chemical reactions. The Al(H2PO4)3 + NiCO3 nanoparticles were active in accelerating the main chemical reactions during upgrading of heavy oil: desulfurization, removal of the side alkyl chains from polyaromatic hydrocarbons, the isomerization of the molecular chain, hydrogenation and ring opening, which led to the viscosity reduction in heavy oil by 42%wt. Moreover, the selectivity of the Al(H2PO4)3 + NiCO3 catalyst relative to the light distillates increased up to 33.56%wt., which is more than two times in contrast to the light distillates of initial crude oil. The content of resins and asphaltenes in the presence of the given catalytic complex was reduced from 34.4%wt. to 14.7%wt. However, FeP + NiCO3 nanoparticles contributed to the stabilization of gasoline fractions obtained after upgraded oil distillation. Based on the results, it is possible to conclude that the thermolysis of heavy oil in the presence of FеР and Al(H2PO4)3 is a promising method for upgrading heavy oil and reducing its viscosity.