Adaptable kinetic model for the transient and pseudo-steady states in the hydrodeoxygenation of raw bio-oil

Abstract

The hydrodeoxygenation (HDO) of raw bio-oil is an attractive route for the production of fuels and chemicals from biomass. For the sake of advancing towards the implantation of HDO at larger scale, an adaptable kinetic model is presented for this process. A CoMo bifunctional catalyst supported on an activated carbon has been used. The P-functionalities of the activated carbon support provide the catalyst with enhanced acidic features. The HDO runs have been carried out in a continuous packed bed reactor at 425–475 °C. Two subsequent reaction stages have been observed during the experimental runs: a transient and a pseudo-steady state. In the former stage, the catalyst is partially deactivated whereas in the latter, an apparent constant activity is reached. The model decodes the complex reaction network of HDO with seven lumps and eleven reaction steps. The proposed model accounts for the evolution with time of the reaction medium composition in the transient state, considering the reactions involved in the gas phase and the ones of solid product deposition and catalyst deactivation. Important contributions of decarboxylation/decarbonylation/decomposition and repolymerization pathways towards CO/CO2/CH4 and thermal lignin are observed. The model also estimates the product distribution in the pseudo-steady state, in which the net deposition of solid products and the catalyst deactivation are negligible. In this state, the catalyst shows a partially inhibited conversion of phenolic compounds and the maximum yield of aromatics, which are the most interesting value-added chemicals. The proposed kinetic model could play a key role in the design of reactors for the HDO process at higher scale.