Exploring the potential of red mud and beechwood co-processing for the upgrading of fast pyrolysis vapours

Red mud, a by-product of the Bayer process in the aluminium industry, is co-processed with beechwood for the in-situ upgrading of fast pyrolysis vapour products. It is revealed that the co-processing of beechwood with thermally pre-treated red mud enhanced the vapour upgrading effect. Individual oxides (α-Al₂O₃, Fe₂O₃, SiO₂, and TiO₂), which are the main constituents of red mud were also tested for the identification of their individual impact on the upgrading process. A biomass/catalyst weight ratio of 1:4 showed the strongest effect on the product distribution. Red mud was found to reduce the yield of phenolic compounds and promote the formation of cellulose- and hemicellulose-derived furfurals and hemicellulose-derived acetic acid, which can be used for the production of a broad range of chemicals and liquid transportation fuels. α-Al₂O₃ and Fe₂O₃ reduced the relative yield of phenols as well, whereas the formation of furfurals was promoted by Fe₂O₃ and TiO₂. SiO₂ showed negligible effect on fast pyrolysis vapours. The impact of catalysts on the product distribution is discussed for phenols, furfurals, and acids, for which the strongest effects were observed.