Gui-Zhuan Xu,Chun Chang,Wei-Na Zhu,Bo Li,Xiao-Jian Ma,Feng-Guang Du
Direct production of ethyl levulinate (EL) from glucose catalysed by a liquid acid catalyst (sulfuric acid) and a solid acid zeolite catalyst USY NKF-7 (USY) in ethanol media was investigated in this study. Effects of the initial glucose concentration (C
G0), reaction temperature (T), amount of acid catalyst, and water addition on the yields of EL were compared, respectively. The results show that higher yield of EL can be obtained at lower C
G0. Higher temperature and acid concentration can accelerate the reaction rate, but the formation rate of the by-products increases more quickly than that of EL. Water addition also can result in the decrease of the yield of EL. Although sulfuric acid is efficient in the production of EL, the USY is more efficient in converting glucose to 5-ethoxymethyl-2-furaldehyde. Moreover, the use of USY can limit the diethyl ether production, and it can be reused for multiple times.
Three kinds of Pt nanocrystals with different morphologies (5 nm cubes, 10 nm cubes and 5 nm truncated octahedrons) were synthesized and employed to fabricate Pt/CNT-USY catalysts for selective ring opening of decalin. The 5 nm truncated octahedral Pt/CNT-USY with exposed (100) and (111) facets exhibited higher yield of ring-opening products (53.9 wt%) than the CNT-USY-supported 5 nm cubic Pt catalyst enclosed by the (100) facets (39.6 wt%). Moreover, the 5 nm cubic Pt showed better catalytic activities compared to the 10 nm cubic Pt/CNT-UST catalyst, which ascribed to the smaller size of Pt NCs enriched more revealable metal active sites. DFT calculations demonstrated that the adsorption of decalin on Pt (111) was stronger than that on Pt (100) facets, which was profitable for the selective ring-opening reaction. Graphical Abstract
The selective oxidation of 5-hydroxymethylfurfural (HMF) to value-added products plays an important role in biomass catalytic transformation, which essentially depends upon design of highly efficient and selective catalysts. This study aims to identify contributions of silanols (Si-OH groups) on Ag/USY catalysts to regulating catalytic performances in selective oxidation of HMF to HMFCA (5-hydroxymethyl-2-furancarboxylic acid), by means of aluminium tri-sec-butoxide (AlBO) modification to suppress Si-OH groups of USY and 2,6-di-tert-butylpyridine (2,6-DTBPy) selective poison to shield Brønsted acid sites in the reaction system. The catalysts are characterized by XRD, BET, TEM, XPS and FT-IR to examine the crystal structures, surface areas, porosity, morphology, Ag distribution, chemical states, and surface adsorptive properties. The HMF conversion (44-49.2%) slightly changes with increasing AlBO content, whereas the HMFCA selectivity gradually goes down from 56.2 to around 22.1% and the levulinic acid (LA) selectivity minorly raises from 5.6 to 12.8%. The production of LA originates from enhanced Brönsted acid sites after AlBO modification, and the decline of HMFCA selectivity is principally attributed to the suppression of Si-OH groups that weakens the interaction between HMF reactants and catalysts. This work provides new insights into the role of surface modification in tailoring metal and zeolite-based catalysts for organic conversions. Graphical
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