A robust mesoporous sulfated zirconium-doped KIT-6 solid acid catalyst for the hydrolysis of microcrystalline cellulose

BACKGROUND The exploration of a robust solid acid catalyst for the efficient hydrolysis of cellulose is a research hotspot due to the need for clean production and sustainable development. KIT-6 silica offers abundant three-dimensionally interconnected mesopores, which are expected to be superior to mesoporous structures with one- or two-dimensional channels due to faster diffusion of reactants and products during reaction. The catalytic conversion of microcrystalline cellulose is examined in detail over a functionalized KIT-6 catalyst prepared by the method of Zr addition and subsequent sulfation.RESULTS In terms of cellulose conversion and product yield, the activity of the catalysts followed the order of sulfated Zr-KIT-6 > Zr-KIT-6 > SO42--KIT-6 > KIT-6. Over the sulfated Zr-KIT-6 catalyst with a Si/Zr molar ratio of 7:1, a maximum cellulose conversion of 95.0% was achieved with glucose yield of 23.4%, 5-hydroxymethylfufural yield of 4.9% and levulinic acid yield of 11.7% under the optimized reaction conditions: reaction temperature of 200 degrees C, reaction time of 2 h, catalyst amount of 0.3 g, cellulose-to-water mass ratio of 1:1.CONCLUSION The sulfated Zr-KIT-6 catalyst possessed the strongest and richest Bronsted acid sites, which readily provided protons for the cleavage of beta-1,4 glycosidic bonds in cellulose, thus conferring superior catalytic activity in cellulose hydrolysis. A plausible pathway at the initial stage of cellulose hydrolysis over the catalyst was proposed. (c) 2023 Society of Chemical Industry (SCI).