Since efficient isomerization of glucose to fructose is vital for valorizing cellulose fraction of biomass to value-added chemicals, an approach of engineering aluminum-hydrochar catalyst by impregnating aluminum on swollen cellulose derived hydrochar has been studied. The results showed that Al-hydrochar calcinated at 300°C achieved fructose yield of 26.3% in acetone/H 2 O reaction medium. It was found that the amorphous Al structures with nano-size on the surface of the carbon microspheres were the major contributor of the catalytic activity on glucose to fructose isomerization , while the formation of Al crystal had an inhibition effect on glucose isomerization. The deactivation study of Al-hydrochar catalysts showed the exfoliation of colloidal carbon containing aluminum active catalytic sites. This finding provides a novel strategy for efficient isomerization of glucose by Al-hydrochar prepared through hydrothermal carbonization and mild calcination activation process.
Hydrochar microspheres supported Al catalysts with hierarchically porous structure (Al/HPHMs) for glucose to fructose isomerization were fabricated. Superior catalytic selectivity (93.3%) and fructose yield (32.6%) were achieved in aqueous under 160 °C for 20 min. Hierarchically porous structure was formed after KHCO 3 and K 2 CO 3 activation and the roles of KHCO 3 and K 2 CO 3 in controlling the Al phase and tailoring morphology of hydrochar supported Al were evaluated. The major active sites were characterized as Al hydroxides including β-Al(OH) 3 , γ-Al(OH) 3 , γ-AlO(OH), Al-C-O linkages. Active sites by KHCO 3 activation with high contents of Al-C-O and Al(OH) 3 have better selectivity. Oxygen-containing functional groups including aluminum‑oxygen groups on the hydrochar microspheres have contributed to the formation of hydrogen bond and π-π interactions between glucose and Al species. Green process synthesized aluminum-hydrochars have potential for their application as a variety of stable, recyclable, and efficient catalysts for lignocellulosic biorefining.
Pengfei Yao,Guangpin Lin,Yi Su,Li Shu,Yingpin Wen,Fengli Yang
The isomerization of glucose catalyzed by attapulgite (ATP) modified by MgCl 2 was investigated. The catalytic performance of ATP on glucose isomerization was significantly enhanced after MgCl 2 modification (Mg-ATP), achieving a fructose yield of 36.5 % and a selectivity of 90.2 % in an aqueous system at 120 °C for 1 h. Combined with the characterization results, it could be concluded that the microstructure of ATP has been changed after MgCl 2 modification, leading to an increase in surface area and the number of weak basic sites, which are beneficial for the glucose isomerization reaction.
The catalytic isomerization of glucose to fructose plays a pivotal role in the application of biomass as a feedstock for chemicals. Herein, we propose a facile solid-state-grinding strategy to construct ZrO2/MgO mixed oxides, which offered an excellent fructose yield of over 34.55% and a high selectivity of 80.52% (80 °C, 2 h). The co-mingling of amphiphilic ZrO2with MgO improved the unfavorable moderate/strongly basic site distribution on MgO, which can prohibit the side reactions during the reaction and enhance the fructose selectivity. Based on the catalyst characterizations, MgO was deposited on the ZrO2surface by plugging the pores, and the addition of ZrO2lessened the quantity of strongly basic sites of MgO. Additionally, the presence of ZrO2largely enhanced the catalyst stability in comparison with pure MgO by recycling experiments.
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