RSC Advances
·
2017
·Vol. 7
·期 24
·14330-14336
·
IF 3.108
Minghao Li,Wenzhi Li,Yijuan Lu,Hasan Jameel,Hou-min Chang,Longlong Ma
Biomass derived 5-hydroxymethylfurfural (HMF) is regarded as an important platform molecule for the synthesis of value-added chemicals and fuels, but the high production cost has always been a bottleneck for the industrial scale use of HMF. Different mineral acids (HCl and H2SO4) being used as the catalyst and different salts being used as the reaction promoter were evaluated. It was found that HCl, in combination with NaCl, in a water/γ-valerolactone system showed high selectivity and impressive efficiency for the synthesis of HMF from glucose. The optimal conditions to obtain the best HMF yield (62.45%) were 0.2 M HCl and 0.1 M NaCl at 140 °C with a residence time of 60 minutes. An 18.22% molar yield of LA was obtained as a by-product. The effect of different anions was also investigated, and it was determined that not only the hydrogen ions, but also the nature of the acid and the type of salt played a joint role in improving the HMF yield. In addition, a possible synthesis pathway was proposed for large scale production of HMF.
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高影响因子
RENEWABLE ENERGY
·
2024
·
IF 9
Hongjin Qu,Tianliang Lu,Xiaomei Yang,Lipeng Zhou
Tin-containing β zeolite exhibits excellent catalytic performance in various biomass conversions to high-value chemicals due to its strong Lewis (L) acidity produced by framework Sn 4+ sites. However, it is difficult to incorporate Sn species into the framework of β zeolite due to that the ionic radius of Sn (0.69 Å) is larger than that of Si (0.40 Å). Herein, organic additives with carbonyl, hydroxyl , aldehyde or amine groups were used to stabilize Sn species in the gel and framework Sn 4+ in the zeolite. Among all additives, acetone (AC) has the best stabilizing effect on Sn species. The stabilization effect between AC and Sn 4+ sites was observed by FT-IR. The characterization results indicate that more tin species were incorporated into β framework and the L acid density increased due to the complexation between carbonyl group and Sn species. Compared to Sn-β-3d synthesized without additive, the L acid density of Sn-β-AC-3d increased by ∼50% (from 21 μmol g −1 to 34 μmol g −1 ). For the conversion of ethyl levulinate to γ-valerolactone, the reaction reached equilibrium faster over Sn-β-AC-3d than over Sn-β-3d at the investigated reaction temperatures. A yield of 98% was obtained over Sn-β-AC-3d at 110 °C. Besides, Sn-β-AC-3d exhibited good stability and reusability.
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高影响因子
GREEN CHEMISTRY
·
2024
·
IF 9.3
Mingzhu Yao,Baojie Liu,Lina Qin,Zicheng Du,Zenglin Wang,Chengrong Qin,Chen Liang,Caoxing Huang,Shuangquan Yao
Deep eutectic solvents (DESs) are widely used as recyclable green solvents for the separation of lignin from lignocellulosic biomass. However, the poor permeability of DES solution limits the green advancement of separation systems. In addition, lignin fragment molecules are susceptible to repolymerization reactions during separation, resulting in reduced lignin reactivity. In this study, a DES consisting of choline chloride (ChCl) as a hydrogen acceptor, 5-sulfosalicylic acid (5Saa) as a hydrogen donor, and a certain amount of γ-valerolactone (GVL) as an additive was designed. The system not only efficiently fractionated lignin from poplar (71.35%), but also selectively retained almost complete cellulose (retention 92.87%) under the optimal fractionation (ChCl/5Saa/GVL molar ratio 1/4/15, temperature 120 °C, time 3.0 h). Pre-crushing processing of raw materials was avoided as the new DES solution has stronger permeability compared to the previous DES solution. Selective deconstruction of lignocellulose was achieved due to a strong hydrogen network structure. The lignin fragments were effectively dissolved. The results showed that the stability of the carbo-positive active intermediates was enhanced by ChCl–5Saa/GVL. Lignin with a low molecular weight (2305 g mol−1), high purity (98.77%) and high total phenolic hydroxyl content (6.92 mmol g−1) was obtained. Homogeneous lignin nanoparticles (LNPs) were prepared with an average particle size of 23 nm. LNPs had high dispersion stability and excellent UV shielding properties. The green advancement of the new DES has been significantly improved and the efficient fractionation of high-value lignin was realized.
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Molecular Catalysis
·
2022
·
IF 5.089
Peng Zhang,Mingwei Ma,Pan Hou,Jingjie Cao,Qi Guo,Huijuan Yue,Ge Tian,Shouhua Feng
A series of ultrathin metal intercalated montmorillonite (Mont) nanosheet materials were prepared and characterized for the one-pot cascade conversion of furfural (FAL) to obtain γ-valerolactone (γ-GVL). The coordination of the intercalated metal ions and the hydroxyl groups between the montmorillonite layers leads to an increase in the specific surface area and pore volume of the material, which coupled with the acidity of the metal ions themselves improves the catalytic performance of the material. Thus Zr-Mont-0.1 exhibited optimal catalytic performance with 100% conversion of FAL and 50.4% yield of GVL under mild conditions, and more importantly, the catalyst maintained its good catalytic performance after the fourth use. Meanwhile the number of Lewis and Brønsted acid sites in the Zr-Mont catalyst can be varied by adjusting the zirconium ion concentration. The proposed reaction mechanism provides initial insights into the role of metal-functionalized montmorillonite in catalyzing the reaction. In addition, the ten-fold magnification reaction confirmed the potential industrial application of the catalyst.
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INORGANIC CHEMISTRY
·
2021
·
IF 5.165
Jie Li,Shuaiheng Zhao,Zhen Li,Dan Liu,Yingnan Chi,Changwen Hu
Catalytic transformation of levulinic acid (LA) to γ-valerolactone (γ-GVL) is an important route for biomass upgradation. Because both Bro̷nsted and Lewis acidic sites are required in the cascade reaction, herein we fabricate a series of H3PW12O40@Zr-based metal–organic framework (HPW@MOF-808) by a facile impregnation method. The synthesized HPW@MOF-808 is active for the conversion of LA to γ-GVL using isopropanol as a hydrogen donor. Interestingly, with the increase in the HPW loading amount, the yield of γ-GVL increases first and then decreases, and 14%-HPW@MOF-808 gave the highest γ-GVL yield (86%). The excellent catalytic performance was ascribed to the synergistic effect between the accessible Lewis acidic Zr4+ sites in MOF-808 and Bro̷nsted acidic HPW sites. Based on the experimental results, a plausible reaction mechanism was proposed: the Zr4+ sites catalyze the transfer hydrogenation of carbonyl groups and the HPW clusters promote the esterification of LA with isopropanol and lactonization to afford γ-GVL. Moreover, HPW@MOF-808 is resistant to leaching and can be reused for five cycles without significant loss of its catalytic activity.
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PubMed
高影响因子
FUEL
·
2024
·
IF 6.7
Wei Xue,Mingwei Ma,Pan Hou,Peng Zhang,Wenzheng Liu,Yongchen Liu,Huijuan Yue,Xiaofeng Wang,Ge Tian,Shouhua Feng
The one-pot tandem conversion of furfural (FUR) to γ-valerolactone (GVL) is desirable due to the high value of GVL and the efficiency of the synthesis process. While MOF-808 presented a good catalytic potential among Zr-MOFs, it lacked the necessary Brønsted acidity for the tandem conversion. In this study, Zr-based metal–organic framework (MOF-808) was modified with acids of different strengths (triflic acid, sulfuric acid, sulfamic acid, and trifluoroacetic acid) using a two-step post-synthesis impregnation method. EPR results revealed the appearance of coordinatively unsaturated sites of Zr (Zr-CUS) in the first step of HCl-treated Zr-808-HCl and their disappearance in the subsequent acid-modified catalysts, clarifying the impregnation process. These modified frameworks (Zr-808-TF, Zr-808-S, Zr-808-SN, and Zr-808-CF) were employed as catalysts for the tandem conversion of FUR to GVL. Zr 3d XPS and solid-state 31 P MAS NMR spectra of TMPO adsorbed on the catalysts proved that Zr-808-TF outperformed other catalysts in terms of both Brønsted/Lewis acid strength and ratio. With such catalytic active sites, Zr-808-TF exhibited superior catalytic activity, achieving 83% GVL yield over an 8-hour reaction period. The four acid-modified catalysts not only differed in Lewis/Brønsted acid sites, but also exhibited different catalytic performances in the tandem conversion. The in-depth insight into the relationship between the modified functional groups and the acid-base sites provides a new avenue to optimize the acid-base sites and expands the application of MOFs in cascade catalysis.
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