Solid phosphoric acid catalysts based on mesoporous silica for levoglucosenone production via cellulose fast pyrolysis

BACKGROUND Biochemicals are interesting alternatives for biomass valorization owing to their much higher added value compared to biofuels and energy products. Several methods for the production of valuable chemicals such as levoglucosenone (LGO) via thermochemical processes over solid acid catalysts are being investigated due to their important advantages compared to conventional biomass acid impregnation techniques. The present work explores the synthesis of catalytic materials for the production of this platform molecule. RESULTS Aluminum-loaded SBA-15 mesoporous silica and the corresponding solid phosphoric acid (SPA) catalysts were prepared, characterized by TEM, FTIR, MAS NMR, NH3-TPD, N-2 adsorption, ICP-AES and titration of 'free H3PO4', and tested in cellulose fast pyrolysis. Post-synthesis Al deposition on the silica support produced an increase of bio-oil yield and LGO amount in pyrolysis products. The presence of Al in SPA catalysts led to the formation of aluminum phosphates, decreasing the concentration of H3PO4 species in the surface and therefore the LGO levels. The SPAs presented relatively high LGO levels in the GC-MS detectable liquid products (up to 85 peak area%) which was found to be correlated with the amount of free H3PO4 in the solid catalysts. CONCLUSION Aluminum grafting over SBA-15 is an effective way to increase the selectivity to the target anhydrosaccharide. In SPAs, the presence of Al reduced the easily leachable H3PO4 amount, which is desirable from the point of view of catalyst stability because deactivation is mainly caused by H3PO4 leaching, but also led to lower levels of LGO in bio-oil. (c) 2018 Society of Chemical Industry