Reactivity and structural changes of asphaltene during the supercritical water upgrading process

Abstract Experiments on the reactivity and structural changes of asphaltene in the SCW upgrading process were conducted with a batch reactor. The reactivity and structural changes of asphaltene was evaluated with the yield of products (gas, maltene and coke) and the characterizations of remaining asphaltene with elemental analysis (C, H, N, and S), gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR) and 1H nuclear magnetic resonance (1H NMR). As shown from the transformation of asphaltene, the enhance of severity condition would increase the conversion of asphaltene but resulted in the secondary reaction of maltene and the formation of more coke and gases. And the characterizations fully illustrated that the size was greatly reduced, the ratios of H/C, N/C and S/C were seriously lowered, the alkyl side chains were much shorted and the aromaticity and condensation degree were significantly enhanced as for remaining asphaltene obtained from the SCW upgrading process. Finally, the transformation pathway of asphaltene was analyzed with the reconstruction of asphaltene macromolecular model at various severity condition and the results showed that the reactivity and structural changes of asphaltene was closely related to the cracking of asphaltene macromolecular into smaller one, the fracture of alkyl side chains and the reaction of dehydrogenation and polymerization.