Yan Wan,Lina Zhang,Yeyun Chen,Jinhan Lin,Wenda Hu,Shuai Wang,Jingdong Lin,Shaolong Wan,Yong Wang
The selective conversion of levoglucosan to gluconic acid, widely used in food and pharmaceutical industries, has been achieved in one pot by using a heterogeneous bifunctional catalyst comprising gold on Cs salts of tungstophosphates. With the concerted operation of active Au sites and acidic sites of Cs2.5H0.5PW12O40, gluconic acid was obtained with a high selectivity of 93.1% in nearly complete conversion. The gluconic acid product itself was found to accelerate the overall reaction rate, since the homogeneous Brønsted acidity introduced by gluconic acid could enhance the hydrolysis step of levoglucosan to glucose, a rate-limiting step as revealed by further kinetic analysis. This work provides a new and effective approach for the production of gluconic acid from levoglucosan, potentially enabling the efficient utilization of lignocellulose biomass to obtain value-added chemicals.
Miao Wang,Shuai Zhang,Xiangjun Liu,Yayun Ma,Junqi Wang
A comprehensive study of alkali and alkaline earth metal (AAEM) salts including two different anions (Cl - and CH 3 COO - ) in the catalytic pyrolysis of cellulose to produce levoglucosan (LG), bio-oil, and biochar were investigated. At the same time, the catalytic pyrolysis mechanism was also speculated. The thermogravimetric analyzer (TGA) and lab-scale fixed-bed reactor system were used to determine the thermal degradation process and the pyrolysis products of LG, bio-oil, and biochar. The optimized pyrolysis parameters were obtained by using Box-Behnken design-response surface method. According to the results, AAEM salts significantly boosted the yield of biochar, as well as greatly cut down the output of LG and bio-oil. The rank of effect on LG yield was as follows: CaCl 2 , MgCl 2 > CH 3 COOK, CH 3 COONa > (CH 3 COO) 2 Mg, (CH 3 COO) 2 Ca > KCl, NaCl. Moreover, the addition of AAEM salts considerably dropped the activation energy E of cellulose pyrolysis as well as prompted microcrystalline cellulose pyrolysis under lower temperatures. This study was pivotal in deducing the pathway of cellulose pyrolysis, thereby offering critical insights to hasten the progress of biomass utilization.
Ke Wang,Junyu Pan,Yi Gao,Gang Wu,Guiying Lin,Kuan Ding,Xun Hu,Shu Zhang,Yong Huang
Levoglucosan (LG), a valuable chemical derived from carbohydrates, is challenging to obtain with high yield directly from raw biomass. In this study, pyrolysis of a lignocellulosic biomass to LG was studied with various pretreatment methods, including acid, alkali, and torrefaction pretreatments. The results indicated that the hydrochloric acid washing effectively promoted the production of LG when the concentration of HCl was lower than 0.5 mol/L, mainly caused by the improved crystallinity of the cellulose fraction and the removal of alkali and alkaline earth metals (AAEMs). When 4% of NaOH solution was employed for the alkali pretreatment, the relative content of LG significantly increased from 3.07 to 73.59 with the temperature ranging from 130 to 170 ℃, owing to the effective removal of lignin and hemicellulose fractions. Biomass torrefaction at temperature lower than 250 ℃ slightly promoted LG production, but it inhibited the formation of LG when the temperature reached 300 ℃.
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