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

Highly efficient isomerization of glucose to fructose is essential for valorizing cellulose fraction of biomass to valueadded 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.biort ech.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℃ in 30 min.Scanning electron microscope-energy dispersive spectrometer and X-Ray diffraction revealed that the distribution of Mg^(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 H2O 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.