Cost-effective upgrading of biomass pyrolysis oil using activated dolomite as a basic catalyst

Abstract

This study deals with a continuous process on a calcined dolomite operating at atmospheric pressure and by cofeeding water for cost-effective upgrading of raw bio-oil at 400 °C and 500 °C. The distribution of carbon in the feed to the product fractions (gas and upgraded bio-oil) and to the dolomite (as CO2 captured and coke) was investigated with time on stream, as well as the evolution of the gas and the upgraded bio-oil composition. Acids and high-molecular weight phenols were completely removed from the raw bio-oil for 0.5 h time on stream, with the upgraded bio-oil being mainly composed of ketones (acetone, 2-butanone and cyclopentanones). Chromatographic analyses of the reaction products were combined with analysis of the dolomite characteristics by thermogravimetry and X-ray diffraction. The results are explained on the basis of possible reaction mechanisms on the dolomite basic sites (CaO, Ca(OH)2 and MgO) and the extent of dolomite carbonation with adsorbed CO2. Composition of the upgraded bio-oil makes it suitable for further catalytic valorization for obtaining fuels and chemicals, such as H2 (by steam reforming) and aromatic hydrocarbons (by dual-stage hydrogenation- cracking processes).