Lincai Peng,Chaonan Tao,Hui Yang,Junhua Zhang,Huai Liu
Catalytic upgradation of carbohydrates in concentrated feeds well conforms to the demands for the industrial deployment of bio-based fuels and chemicals, but the majority of existing explorations merely focused on the utilization of dilute feedstock. In this contribution, the degradation behavior of both dilute (20 g L−1) and concentrated glucose (200 g L−1) in an ethanol medium was comparatively investigated by acid catalysis. The increase of the glucose concentration from 20 to 200 g L−1 largely boosted the formation of water-soluble oligomers (WSO) instead of solid humins (SHU). The high initial glucose concentration favored the formation of glucose oligomers, and the high instantaneous concentration of EL and 5-hydroxymethylfurfural (HMF) also exacerbated the polymerization reactions, both of which are responsible for the formation of excessive WSO in a concentrated feed. Structural characterization revealed that substituted furans, 2,5-dioxo-6-hydroxyhexanal (DHH) and its analogue are the main fragments in WSO20, while WSO200 largely consisted of glucosyl units as well as furanic and aromatic fragments linked with aliphatic units, leading to the distinct structure of SHU from the two feed concentrations. This work provides insights into the effect of the feed concentration on product formation during acid-catalyzed ethanolysis of glucose, facilitating the development of optimal processes for valorizing concentrated sugars.
Inspired by inorganic oligomers, we herein develop a novel inorganic gel based on calcium oxalate oligomers, and the crystallization morphology has been studied initially in this paper. The prepared oligomer is translucent gel and can exist stably in ethanol, but in aqueous medium it will change from gel to powder. In the crystallization process, because of the volatile speed of solvent and capping agent TEA at different temperature, CaC 2 O 4 oligomer gels (COOGs) exhibited distinct crystallization behavior and morphology. Compared with conventional inorganic crystallization, the crystallization process of the gel at room temperature shows a tendency to gradually extend to the inside of the gel. Moreover, the XRD pattern and SEM images shown that the COOGs achieved distinctly different crystal morphology under different temperature. These provide a preliminary research foundation for the crystallization behavior and control conditions of inorganic gels. Graphical abstract
Mingqiang Chen,Longyang Li,Yishuang Wang,Defang Liang,Zinan Zhou,Haosheng Xin,Chang Li,Gang Yuan,Jun Wang
Converting cellulose (Cel) into ethyl levulinate (EL) is one of the promising strategies for supplying liquid fuels. In this paper, the prepared sulfonated P-W-modified N-containing carbon-based solid acid catalyst (PWNCS), in which the Polyaniline (PANI) was employed as N and C precursors, successfully converted Cel into EL under the water-ethanol medium. The characterization results demonstrated that a tiny addition of P increased the Brønsted acid sites (BAS) content and defective WO 3 provided the Lewis acid sites (LAS), meanwhile, the sulfonation process did not change the fundamental structure but introduced the sulfonic groups to dramatically increase the acidic content. Therefore, under optimized reaction conditions, PWNCS realized about 100% Cel conversion and 71.61% of EL yield, furthermore, the selectivity of EL reached 89.14%. In addition, the effect of water on the reaction pathway of Cel to EL over PWNCS was proposed. The addition of water generally resulted in the hydration of defective WO 3 to reduce the LAS and increase BAS, which significantly inhibited the side reactions of retro-aldol condensation (RAC) and subsequent etherification reactions during Cel conversion and then improved the selectivity of EL.
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