Kinetic study for the Ashalcha heavy crude oil upgrading at supercritical water conditions

The lack of proper kinetic models for the supercritical water application to heavy crude oil upgrading is the driving force of this work. Thus, experiments for Ashalcha heavy oil upgrading were conducted in a batch reactor at supercritical water conditions (380-420 degrees C and 15-120 min). Three different reaction schemes were studied based on the reactions occurring between saturates, aromatics, resins, asphaltenes, coke, and gas, including new proposed reaction pathways. The best model was selected based on statistical and sensitivity analyses. It is corroborated that asphaltenes conversion follows first-order reaction, and that the free radical mechanism prevails for all reactions at supercritical water conditions. The results indicate that resins are the main reagent instead of asphaltenes since the content of the latter fraction is low for the heavy oil employed. Thus, the main route is through in-series decomposition and polyaddition reactions between maltenes (resins -><- aromatics -><- saturates), being resins the main gas precursors. The conversion of heavy fractions into lighter compounds is preferably carried out by ring-opening reactions rather than dealkylation. The higher yield of light fractions is achieved at 380 degrees C since over 400 degrees C the coke and gas formation is promoted due to condensation, dehydrogenation, and secondary cracking reactions.