Synthesis of Mg–K-biochar bimetallic catalyst and its evaluation of glucose isomerization

• Published in: Biochar (Online) 2023-09, Vol.5 (1), p.1-17, Article 56
• Main Authors: Kang, Xiheng, You, Zi, Peng, Jian, Ragauskas, Arthur J., Pang, Jingdong, Zhao, Peitao, Yin, Yongjun, Song, Xueping
• Format: Article
• Language: English
• Subjects: Agriculture; BASIC BIOLOGICAL SCIENCES; Biochar; Catalyst; Ceramics; Composites; Earth and Environmental Science; Environment; Environmental Engineering/Biotechnology; Fossil Fuels (incl. Carbon Capture); Fructose; Glass; Isomerization; MgO; Natural Materials; Original Research; Renewable and Green Energy; Soil Science & Conservation
• ISSN: 2524-7867; 2524-7867
• DOI: 10.1007/s42773-023-00250-w

Highly efficient isomerization of glucose to fructose is essential for valorizing cellulose fraction of biomass to value-added chemicals. This work  provided an innovative method for preparing Mg-biochar and Mg–K-biochar catalysts by impregnating either MgCl 2 alone or in combination with different K compounds (Ding et al. in Bioresour Technol 341:125835, 2021, https://doi.org/10.1016/j.biortech.2021.125835 and KHCO 3 ) on cellulose-derived biochar, followed by hydrothermal carbonization and pyrolysis. Single active substance MgO existing in the 10 Mg–C could give better catalytic effect on glucose isomerization than the synergy of MgO and KCl crystalline material present in 10 Mg–KCl–C. But the catalytic effect of 10 Mg–C was decreased when the basic site of MgO was overloaded. Compared to other carbon-based metal catalysts, 10 Mg–KHCO 3 –C with 10 wt% MgCl 2 loading had  excellent catalytic performance, which gave  a higher fructose yield (36.7%) and selectivity (74.54%), and catalyzed excellent glucose conversion (53.99%) at 100 °C in 30 min. Scanning electron microscope–energy dispersive spectrometer and X-Ray diffraction revealed that the distribution of Mg 2+ and K + in 10 Mg–KHCO 3 –C  was uniform and the catalytic active substances (MgO, KCl and K 2 CO 3 ) were more than 10 Mg–C (only MgO). The synergy effects of MgO and K 2 CO 3 active sites enhanced  the pH of reaction system and  induced H 2 O ionization to form considerable OH − ions, thus easily realizing a deprotonation of glucose and effectively catalyzing the isomerization of glucose. In this study, we developed a highly efficient Mg–K-biochar bimetallic catalyst for glucose isomerization and provided  an efficient method for cellulose valorization. Graphical Abstract Highlights The bimetallic Brønsted catalyst designed in this study ( 10 Mg–KHCO 3 –C) could achieve high fructose yield (36.7%) and selectivity (74.54%). The MgO  could give obtain good catalytic effect on glucose isomerization, but the catalytic effect decreased when the Mg + was overloaded. The synergy effects of MgO  and K 2 CO 3 could enhance the pH of reaction system and effectively catalyze the isomerization of glucose.