Kinetic and reaction pathway of upgrading asphaltene in supercritical water

Experiments of upgrading asphaltene in Supercritical Water (SCW) were conducted in autoclaves with sealed gold tube reactors to elucidate the reaction pathway and reaction kinetics. The experiments were performed at temperature of 400-450 degrees C, pressure of 30 MPa and residence time ranging from 0 to 120 min. The products obtained from the upgrading asphaltene in SCW included gas, maltene and coke. Kinetic analysis showed that upgrading asphaltene in SCW obeyed a first-order kinetic with apparent activation energy of 51.11 kJ/mol. Three possible 4-lump kinetic models were proposed to discuss the detailed reaction pathway of upgrading asphaltene in SCW. The first-order kinetic equations were used to evaluate the reliability of each model from the aspect of correlation coefficient (R-2). The results showed that Model 2, considering the parallel reaction of asphaltenes transformation to gas, maltene and coke, the consecutive reaction from maltene to gas and coke, the secondary reaction of coke to gas, was illustrated as the optimal reaction pathway model for upgrading asphaltene in SCW. (C) 2015 Elsevier Ltd. All rights reserved.