In situ catalytic upgrading of biomass derived fast pyrolysis vapours in a fixed bed reactor using mesoporous materials

Abstract

Seven mesoporous catalysts were compared in how they can convert the pyrolysis vapours of spruce wood in order to obtain improved bio-oil properties. Four Al-MCM-41 type catalysts with a Si/Al ratio of 20, a commercial FCC catalyst, a pure siliceous SBA-15 and an aluminium incorporated SBA-15 materials were tested. The catalytic properties of Al-MCM-41 catalyst were modified by pore enlargement that allows the processing of larger molecules and by introduction of Cu cations into the structure. Spruce wood pyrolysis at 500 °C was performed in a lab-scale fixed bed reactor, the solid, gaseous and liquid products were separated and the gases and the organic part of the liquids were analysed with the help of gas chromatography and mass spectrometry. The gas yield increased in each catalytic case, the coke yield remained the same or slightly decreased compared to the non-catalytic experiments. The aqueous part in the liquid phase increased in the catalytic runs. The obtained products in the organic phase were grouped into eight groups and further into desirable and undesirable product groups, and the yields were evaluated. In the catalytic experiments the hydrocarbon and acid yields increased, while the carbonyl and the acid yields decreased. All catalysts tested reduced the undesirable product yield, while the desirable product yield remained the same or increased. To study the feedstock effect on the catalytic upgrading of the pyrolysis vapours, some tests were performed with Miscanthus biomass. With spruce the FCC, with Miscanthus the unmodified Al-MCM-41 are the best performing catalysts. Concerning the feedstocks, with Miscanthus a better quality bio-oil has been obtained.