Catalytic conversion of a biomass-derived oil to fuels and chemicals II: Chemical kinetics, parameter estimation and model predictions

Abstract

Kinetic modeling of the conversion of a bio-oil over HZSM5 catalyst in a fixed-bed microreactor was studied. Based on the two reaction pathways proposed earlier (Part I), the yields of various products were calculated as a function of temperature. The predicted results from the kinetic models matched closely the results obtained from experiments. The results showed that a model for bio-oil conversion must also account for the formation of coke and residue from reactions of both volatile and nonvolatile components of the bio-oil. The kinetic models showed that bio-oil upgrading was a complex combination of parallel and series reactions. Bio-oil deoxygenation and cracking of the nonvolatiles were identified as the rate controlling steps. Since the hydrocarbon component of the organic distillate fraction (ODF) was the main product of interest, hydrocarbon selectivity models based on coke, residue, and combined coke and residue (as undesired products) also were developed. The results showed that the selectivity for hydrocarbons could be improved by selecting operating conditions that would either reduce the rate of coke formation, increase the rate of cracking of the nonvolatile fraction of the bio-oil or by operating at low concentrations and at low temperatures. However, operating at low concentrations and temperatures may not be desirable as conversions are low under these conditions.