Change in the Concentration of Stable Free Radicals and Vanadyl Complexes in the Products of Reaction of Petroleum Asphaltenes with Sulfuric Acid

The products from the reaction of petroleum asphaltenes with sulfuric acid under various conditions, accompanied by oxidation, sulfonation, and decomposition reactions, were studied. The change in the content of stable free radicals and vanadyl complexes in the products from the reaction of asphaltenes with sulfuric acid in relation to the time and temperature was determined by EPR spectroscopy. The chemical processes in the reaction of asphaltenes with sulfuric acid take place most strongly in the first hour, being accompanied by peak growth of the concentration of stable free radicals. With increase in the length of treatment of the asphaltenes with sulfuric acid there is a decrease in the concentration of stable free radicals accompanied by a decrease in the content of sulfo groups in the products. After only 30 min of the process there was a marked decrease in the content of vanadyl complexes in the reaction products.