Comparison of different power-law kinetic models for hydrocracking of asphaltenes

Hydrotreating of Maya crude oil was carried out at a pilot plant scale under the following reaction conditions: pressure of 70-100 kg/cm2, hydrogen-to-oil ratio of 5,000 ft3/bbl, temperature of 380°C-420°C, and space-velocity of 0.33-1.5 h-1. Asphaltenes were precipitated from the feed and from all hydrotreated products using n-heptane as solvent. Hence, variations in asphaltenes concentration were obtained as a function of reaction conditions. Three different kinetic models were studied: a simple power-law model, a modified power-law model which assumes a parallel path reaction for asphaltenes hydrocracking with the same reaction order for more reactive and less reactive asphaltenes, and the same modified power-law model with different orders for both types of asphaltenes. This latter model exhibited the best fit of experimental asphaltenes concentrations.