Nitration of Petroleum Asphaltenes with Concentrated Nitric Acid under Various Conditions

The relationships of the reaction of the of tar asphaltenes with concentrated nitric acid were studied under various quantitative, temperature, and time conditions. According to IR spectroscopic data, nitration occurs to the highest degree during the action of a 50-fold excess of 64% nitric acid on the asphaltenes at 60°C for 4 hours. Nitration is accompanied by oxidation side reactions leading to the formation of nitrate, phenolic, carbonyl, and sulfoxide groups. It was established by mass spectrometry that there is a tendency for the number-average and weight-average molecular weights of the nitration products to decrease in comparison with the initial asphaltenes. It was found by electron paramagnetic resonance that the content of stable free radicals and vanadyl complexes in the products of the nitration reaction decreases.