Home – Home – Jornals – Chemistry for Sustainable Development 2020 number 3

The thermal stability and reactivity of heavy oil asphaltenes at temperatures below 300 °C were evaluated. In this work, we used an original method of sequential stepwise thermolysis of asphaltenes at temperatures of 120, 230, and 290 °C in the inert gas flow with the removal of the resulting products from the reaction zone at each stage of the process. This approach allows us to minimise the occurrence of secondary reactions to assess the true reactivity of asphaltenes, and also to take into account the differences in the binding energies in their molecules to determine the real thermal stability of asphaltenes within different temperature ranges. It was established that when asphaltenes are heated to 300 °C, they undergo intense thermal degradation with the formation of gas, oils, resins and insoluble coke-like substances. In the process of sequential stepwise thermolysis up to 290 ºС, the conversion of heavy oil asphaltenes exceeds 90 %. At a temperature of 120 °C, the conversion of asphaltenes can reach 13 % with the formation of mainly resinous substances (more than 10 mass %). An increase in thermolysis temperature to 230 °C leads to an increase in the conversion of asphaltenes to 40 % due to their ability to generate significant amounts of gas and oils (14-18 mass %), as well as coke-like products (2-10 mass %) under these conditions. In the process of subsequent thermolysis of asphaltenes at a temperature of 290 ºС, the maximum amount of coke-like substances (29-37 mass %) is formed. The yield of low molecular weight products is also significant and amounts to about 20 mass %. Thus, at temperatures below 300 ^oС, asphaltenes of heavy oils are characterised by low thermal stability and extremely high reactivity in thermal processes. The results obtained must be taken into account when developing new and modernising existing oil refining technologies.