Qiang Lu,Hui-yun Tian,Bin Hu,Xiao-yan Jiang,Chang-qing Dong,Yong-ping Yang
Fast pyrolysis of biomass will produce complex pyrolytic products. Hydroxyacetaldehyde (HAA) is one of the most important pyrolytic products, derived from fragmentation (ring scission) of holocellulose. In this study, density functional theory (DFT) calculations are employed to reveal the HAA formation mechanisms from fast pyrolysis of four holocellulose-based monosaccharides, i.e., β- d -glucopyranose, β- d -mannopyranose, β- d -xylopyranose and O -acetyl-β- d -xylopyranose. Moreover, the theoretical calculation results of the β- d -glucopyranose are confirmed by isotopic labeling fast pyrolysis experiments. The results indicate that during β- d -glucopyranose pyrolysis, the HAA is mainly derived from C1 C2, C5 C6 and C3 C4. The C2 C3 bond is easy to break via retro-aldol reaction to form 1,2-ethenediol (ED) which will tautomerize into the HAA from C1 C2 with high selectivity, accounting for the largest proportion of total HAA. The second largest origin of the HAA is the C5 C6 segment in multiple pathways with low energy barriers. However, these reactions to form the HAA from C5 C6 are thermodynamically unfavorable, and moreover, there are facile competing reactions to produce other products. Importantly, the HAA and levoglucosan (LG) are mainly formed via competing parallel pyrolytic pathways. Only a little HAA will be derived from the secondary cracking of LG. In addition, the HAA formation mechanisms from β- d -mannopyranose and β- d -xylopyranose are similar as those from β- d -glucopyranose. However, O -acetyl-β- d -xylopyranose behaves differently from the other three monosaccharides due to the acetyl group at C2 position. The HAA will be mainly derived from C4 C5, accompanied with the formation of acetic acid (AA) from scission of the acetyl branch.
Shuangshuang Jing,Xuefei Cao,Linxin Zhong,Xinwen Peng,Xiaoting Zhang,Sha Wang,Runcang Sun
Converting cellulose to renewable energies and chemicals is the most promising and sustainable route to solving the crisis of fossil fuel resources. Up to now, however, it is still a big challenge to effectively transform recalcitrant cellulose into targeted compounds. For the first time, this study proposes a new and highly effective catalysis system with a synergy effect to convert cellulose into formic acid and levulinic acid simultaneously by using in situ carbonic acid from CO2 as a green acid in the presence of CrCl3. The synergy effect of in situ carbonic acid and CrCl3 could highly effectively hydrolyze cellulose to glucose, isomerize glucose to fructose, dehydrate fructose to HMF, and rehydrate HMF to formic acid and levulinic acid in a one-pot way. Here, 49% formic acid and 32% levulinic acid could be obtained from cellulose at a moderate condition. Our results demonstrated that this new catalysis system is comparable to other catalysis systems, and in situ carbonic acid can be used as a low-cost acid to replace mineral acids such as H2SO4, HCl, and H3PO4 and organic acids such as C6H6O3S, H2C2O4, and Cl3CCOOH to constitute novel, highly effective, low-cost, and less environmental impact catalysis systems for producing formic acid and levulinic acid from cellulose.
The electrosynthesis of multi-carbon chemicals such as glyoxylic acid (GX) and glycolic acid (GC) from oxalic acid (OA) offers a feasible pathway to achieve sustainable chemical production, especially when coupled with the electroreduction of CO2 to form OA. Here, we demonstrate a series of gallium tin oxide catalysts for selective, controlled OA electroreduction to GX and GC in acidic media. The product distribution can be tuned by changing the reaction temperatures. At room temperature using the GaSnOx/C catalyst, GX can be obtained with a GX Faradaic efficiency (FEGX) of 92.7% at −0.7 V vs RHE and a GX current density (jGX) of −100.2 mA cm–2. At a raised temperature of 80 °C using the GaSnOx/C catalyst, a GC Faradaic efficiency (FEGC) of 91.7% at −0.8 V vs RHE can be obtained. The accelerated OA electroreduction results from the Ga/Sn synergy in the catalysts. A proper Ga/Sn ratio not only enriches OA adsorption and enhances surface binding of intermediates, but also ensures catalyst stability in acidic media.
危险品化学品经营许可证（带存储）