Study of glucose isomerisation to fructose over three heterogeneous carbon-based aluminium-impregnated catalysts

Driven by the worldwide demand for sustainable resources and renewable energy, the synthesis of bio-based platform chemicals has attracted broad interest. The isomerisation of glucose to fructose acts as a critical intermediate step among many chemical synthesis routes. In this study, biochar (BC), graphitic oxide (GIO), and graphene oxide (GO) were used as carbon supports to synthesize Al-impregnated heterogeneous catalysts, which were then used for glucose isomerisation under microwave heating in the water at 140 degrees C. The kinetics model with parameters was used to reveal the interplay of the active sites and compare the activity of the three carbon-based catalysis systems. Catalyst characterisation results showed effective aluminium (Al) impregnation onto the three types of catalysts, and it was found that GIO-Al200 and GO-Al200 showed comparable catalytic activity (fructose yield of 34.3e35.0%) for glucose isomerisation. At the same time, BC-Al200 exhibited slightly lower catalytic activity (fructose yield of 29.4%). The conversion kinetics suggested similar catalytic mechanisms on the three catalysts while BC-Al200 manifested slower kinetics, possibly implying higher activation energy. The fructose selectivity decreased with increasing time due to the formation of side products, yet BC-Al200 resulted in less carbon loss than GIO-Al200 and GO-Al200, probably attributed to its lower catalytic activity and higher pH buffering capacity. A green synthesis route of this study promotes biomass valorisation and makes engineered biochar a promising carbon-based catalyst for sustainable biorefinery. (c) 2020 Elsevier Ltd. All rights reserved.