CHINESE JOURNAL OF CATALYSIS
·
2019
·
IF 4.914
Yan Wan,Congcong Zheng,Xianchi Lei,Mengqi Zhuang,Jinhan Lin,Wenda Hu,Jingdong Lin,Shaolong Wan,Yong Wang
ABSTRACT Acetol is a major light oxygenate and readily produced from staged or fast pyrolysis of lignocellulose biomass. Herein we report that acetol can be selectively converted to methyl pyruvate, an important fine chemical, through oxidative esterification over Au-based catalysts. Detailed experimental studies showed that Au on amphoteric supports with appropriate strength and balanced ratio of acid and base sites can facilitate the desired oxidative-esterification pathway without accelerating undesired aldol-condensation or Cannizzaro reactions. In particular, hydroxyapatite (with a Ca/P ratio of 1.62) supported Au achieved 87% selectivity to methyl pyruvate at an acetol conversion of 62%.
研究领域:
化学工程
·
催化科学
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DOI
高影响因子
JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY
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2021
·
IF 5.279
Haixia Xu,Xiaofeng Li,Xuan Xin,Lan Mo,Yucong Zou,Guanglei Zhao
In this paper, an enzymatic route for synthesizing phenolic glycoside azelaic acid esters was successfully set up via lipase-catalyzed esterification and transesterification. Among the lipases tested, Candida antarctica lipase B (Novozyme 435) showed the highest activity in catalyzing esterification and Thermomyces lanuginosus (Lipozyme TLIM) gave the highest substrate conversion in catalyzing transesterification for the synthesis of ester. The addition of 4A molecular sieves into the reaction system is found to be an effective method for in situ absorption of the byproduct water and methanol, with which the substrate conversions of the enzymatic esterification and transesterification were 98.7 and 95.1%, respectively. Also, the main product ratios in transesterification were above 99.0% with lipozyme TLIM as a catalyst because the hydrolysis reaction was hindered. The results of the physical and biological properties indicate that all esters had higher Clog p values than their parent compounds. Also, the esters showed higher intracellular tyrosinase inhibitory and depigmentating activities than phenolic glycosides, azelaic acid (AA), and their physical mixtures due to their higher membrane penetration and tyrosinase inhibitory effects. In particular, piceid 6″-O-azelaic acid ester (PIA) showed the strongest inhibitory effect against melanin production. Its inhibitory rate was 77.4% at a concentration of 0.25 mM, about 4.2 times higher than that of arbutin (18.5%).
研究领域:
生物化学
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药理学
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化妆品科学
✓ 已验证
DOI
PubMed
高影响因子
Polymer Chemistry
·
2020
·Vol. 11
·期 34
·5512-5525
·
IF 5.342
Ming Zhang,Yifei Tu,Zibo Zhou,Guozhang Wu
The exo-hydroxyl group (exo-OH) on isosorbide (ISB) has long been asserted as a highly reactive moiety compared with the endo-hydroxyl group (endo-OH). In this study, calculations based on density functional theory and experiments without adding catalysts reveal that endo-OH has strong nucleophilic ability, and in the case of transesterification with diphenyl carbonate, the nucleophilic attack surmounts steric hindrance in rendering endo-OH more reactive than exo-OH. The kinetics of transesterification with different catalysts is investigated to determine the catalytic reactivity and molecular structure evolution. The results show that preferential activation of exo-OH moieties can be achieved either by reducing the coordination ability of catalytic cations (lg β1) or by enhancing the alkalinity of catalytic anions. Despite the low reactivity of exo-OH on ISB monomers, terminal exo-OH on carbonate oligomers exhibits higher reactivity than terminal endo-OH, justifying the experimental fact that ISB-based polycarbonates (ISB-PCs) are mostly terminated by endo-OH. Balancing the reactivity between endo-OH and exo-OH can be promoted by increasing the reaction temperature, thus accelerating transesterification to a high equilibrium constant. These findings help to clarify the mechanism of ISB transesterification and provide new strategies for the synthesis of high-molecular-weight ISB-PCs.
研究领域:
化学
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材料科学
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DOI
高影响因子
Materials
·
2017
·Vol. 10
·期 7
·694
·
IF 2.654
Yi-Cheng Feng,Hui Zhao,Tong-Hui Hao,Guo-Hua Hu,Tao Jiang,Qun-Chao Zhang
To understand the role of molecular structure on the crystallization behavior of copolyester in thermoplastic poly(ether ester) elastomers (TPEEs), series of poly(butylene-co-1,4-cyclohexanedimethylene terephthalate) (P(BT-co-CT))-b-poly(tetramethylene glycol) (PTMG) are synthesized through molten polycondensation process. The effects of poly(cyclohexanedimethylene terephthalate) (PCT) content on the copolymer are investigated by Fourier transform infrared spectroscopy (FT-IR),1H and13C nuclear magnetic resonance (NMR), gel permeation chromatographs (GPC), wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), mechanical, and visible light transmittance tests. FT-IR and NMR results confirm the incorporation of PCT onto the copolymer. WAXD and DSC indicate that the crystalline structure of the copolymers changed from α-PBT lattice to trans-PCT lattice when the molar fraction of PCT (MPCT) is above 30%, while both crystallization and melting temperatures reach the minima. An increase inMPCTled to an increase in the number sequence length of PCT, the thermal stability and the visible light transmittance of the copolymer, but to a slight decrease in tensile strength and elastic modulus.Keywords:poly(ester ether);copolymerization;microstructures;crystallization behavior
研究领域:
材料科学
·
高分子化学
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DOI
PubMed
高影响因子
Catalysts
·
2021
·Vol. 11
·期 2
·162
·
IF 4.146
Huayin Li,Yuan Tan,Xingkun Chen,Wenshao Yang,Chuanqi Huang,Jie Li,Yunjie Ding
Methyl methacrylate (MMA) is an important monomer in fine chemicals. The synthesis of MMA by one-step oxidative esterification from methacrolein with methanol over a heterogeneous catalyst with high activity, selectivity and stability is highly desirable. Herein, Zn-Al-hydrotalcites (HTs)-supported atomically precise Au25nanoclusters with different molar ratios of Zn2+/Al3+were prepared and used as the precursors for this reaction. They exhibited good performances in comparison with the gold catalysts prepared by the deposition precipitation method. The structural and electronic properties were evaluated by various characterization technologies, including X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), in situ diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) of CO adsorption, X-ray photoelectron spectroscopy (XPS), and CO2temperature-programmed desorption (TPD). The combined characterization results suggested that the adsorption property of gold and the basicity of the catalyst contributes to their high activities. Substrates extended experiments and stability tests implied the potential application of Zn-Al-mixed oxides supported gold catalysts, which paves a new way for supported gold catalyst in the one-step oxidation esterification reaction.Keywords:gold cluster;hydrotalcite;methacrolein;methyl methacrylate;oxidative esterification
研究领域:
化学工程
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催化化学
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DOI
高影响因子
RSC Advances
·
2021
·Vol. 11
·期 25
·15054-15059
·
IF 3.361
Miaojia Song,Xiaohui Di,Yu Zhang,Yongming Sun,Zhongming Wang,Zhenhong Yuan,Ying Guo
As an important bio-based chemical, methyl levulinate (ML) can be produced via enzymatic esterification of levulinic acid with methanol. A kinetic model is developed in this work based on the law of mass action and reaction reversibility, to investigate the effect of enzyme loading, alcohol/acid ratio and temperature on ML yield. Data analysis shows that newly developed binary regression is apparently more persuasive than the commonly used unitary regression. Kinetic study reveals: (1) rate constants of esterification/hydrolysis increase with increasing enzyme loading, while their ratio (equilibrium constant) remains invariant. (2) Methanol has no toxicity towards lipase, and hence, neither the rate constants of esterification/hydrolysis nor the equilibrium constant are affected by alcohol/acid ratio. (3) Both rate constants of esterification/hydrolysis and the equilibrium constant increase with temperature elevation, and their relationships agree with Arrhenius equation and Van't Hoff equation, respectively. (4) The esterification is endothermic and spontaneous. In total, the application of binary regression analysis for the developed model to study the enzymatic esterification kinetics is quite successful.
研究领域:
生物化学
·
酶工程
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DOI
高影响因子
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS
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2021
·
IF 4.539
Jun Yan,Pingfan Xu,Peikun Zhang,Haojun Fan
Seeking a facile strategy to synthesize efficient, inexpensive and robust flame retardants which endow the polyurethane (PU) composites with desirable flame retardancy and mechanical property remains compelling but challenging. Here, we report the surface modification of commercial ammonium polyphosphate (APP) by 3-amino-1,2-propanediol in water solution to construct a novel organic–inorganic hybrid. The functionalized APP (FAPP) with multi-hydroxyl, which acts as both intumescent flame retardants and crosslinking agent, was covalently introduced into solvent-free PU composite via a thermo-curing process. Interestingly, FAPP exhibits good compatibility and strong interfacial interactions within PU matrix, which in turn significantly enhances the tensile strength (~40%) of the resultant PU composite, but without compromising the flexibility. With the incorporation of 15 wt% FAPP, the PU composite reaches a limiting oxygen index of 27.2%, and passes UL-94 V-0 rating. Meanwhile, the peak heat release rate and total heat release are respectively decreased by 64.5% and 37.8% over that of pristine PU, which is far superior to original APP. The high flame-retardant efficiency primarily results from the formation of compact and intumescent char layers in condensed phase. Accordingly, our practice may be extendable to the implementation in other high-performance flame-retardant polymer-matrix composites.
研究领域:
材料科学
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高分子化学
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DOI
高影响因子
JOURNAL OF POLYMERS AND THE ENVIRONMENT
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2021
·Vol. 30
·期 2
·528-540
·
IF 3.667
Wu GuangFeng,Song Xin,Yang ZhiHui,Li YingChun,Zhang HuiXuan
Polyester diol PCL and PBA, polyether diol PTMG and polycarbonate diol PCDL were used as components of WPU soft segment, respectively. Polyether PTMG-WPU has the worst hydrolytic property and the highest thermal stability. The maximum degradation rate temperature Tmax is 407.8 °C, the water contact angle reaches 89.5 °. Traditional polyester PCL-WPU shows the strongest hydrolysis performance, the smallest water contact angle, only 71.7 °, the water absorption rate of 72 h at room temperature is as high as 26.7%. However, the thermal stability of PCL-WPU is lower, the soft segment Tg is −52.3 °C, and Tmax is only 333.7 °C, but the mechanical property of which is the best, the tensile strength is 58.3 MPa, and the elongation at break reaches 857.9%. The most important thing is that the structure of polyester PCL-WPU is more easily destroyed by lipase and water molecules. The acidic products produced after hydrolysis will further promote the degradation of polyester. Therefore, compared with other WPUs, PCL-WPU has the best biodegradability and the most obvious degradation effect under the same conditions. The degradation rate of PTMG-WPU after 30 days of degradation in 0.6% lipase PBS buffer solution and soil was only 4.2% and 2.3%, while the highest degradation rate of traditional polyester PCL-WPU reached 41.7% and 32.0%, respectively. In addition, polycarbonate PCDL-WPU has the highest hardness, reaching 95.5 HD. But its other performances are lower than PCL-WPU.
研究领域:
材料科学
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环境科学
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DOI
高影响因子
EUROPEAN POLYMER JOURNAL
·
2020
·
IF 3.862
Yuejia Zhu,Yongzhu Hu,Zhenjiang Li,Bo Liu,Yuanyuan Qu,Zhihao Zhang,Tianfo Guo,Yongqiang Li,Luoyu Gao,Kai Guo
Hydrogen bond donor (HBD) and organic base binary cocatalyst established a gold standard in organocatalytic ring-opening polymerizations (ROPs). In depth probe of the mechanisms revealed that proton abstraction of the acidic H on the HBDs by the bases do occur frequently. A truly simple HBD and Lewis base (LB) cocatalysis, however, was elusive. We proposed genuine HBD/LB cocatalyst for ROPs by introducing 3-amino-1,2,4-benzothiadiazine-1,1-dioxide (ABTD) as a bidentate H-bond donor and triethylamine (TEA) as a mild Lewis base. ROPs of lactide (LA) and trimethylene carbonate (TMC) in solutions at room temperature were success. The mild ROPs produced polylactide (PLA) of predictable molecular weights (from 1.6 to 26.7 kg mol −1 ) and extremely narrow dispersities (Đ 1.01 to 1.06). Furthermore, well-defined diblock copolymers PTMC-b-PLA were synthesized. NMR titration experiments verified exclusive H-bond donor activation of the monomer and TEA activation of the hydroxyl chain end without trace of proton abstraction.
研究领域:
化学
·
材料科学
✓ 已验证
DOI
高影响因子
COMPOSITES PART B-ENGINEERING
·
2025
·
IF 14.2
Baozheng Zhao,Fei Song,Zheng Pan,Yijiao Xue,Linfeng Tian,Tiancheng Zhang,Li Tan,Rui Yang,Yonghong Zhou,Meng Zhang
At present, thermoset polyurethane foams were mainly derived from petroleum-based resources and faced inherent challenges such as difficulty in recycling and fire hazard. In this study, tung oil and catechol were used to prepare tung oil-derived polyphenols via Friedel-Crafts alkylation reaction. These polyphenols were combined with isocyanate to synthesize tung oil-derived polyurethane (TPU) foam. With the presence of dual dynamically cross-linked phenol-carbamate bonds, the TPU foam could be hot-pressed several times into a smooth and homogeneous TPU film. To improve the fire resistance and compressive strength of TPU foam, phytic acid functionalized metal-organic frameworks (UiO-66-NH 2 @PA) flame retardants were successfully synthesized by one-pot solvothermal method. By adding 20 wt% of flame retardants, the TPU composite foams achieved a UL-94 V-0 flammability rating with a limiting oxygen index of 28.1 vol%. The total heat release, total smoke release, CO production and CO 2 production of the TPU composite foams were reduced by 43.1 %, 57.8 %, 63.6 % and 62.1 %, respectively, compared to the pure TPU foam. Furthermore, the compressive strength of the TPU composite foam continued to increase with increasing flame retardants content, reaching a maximum of 0.55 MPa. Importantly, the introduction of the flame retardants didn't affect the hot-press recycling performance of the TPU foam, but instead improved the tensile strength and flame retardancy of the recycled TPU film. This work paved the way to produce bio-based PU foam with excellent flame retardancy and recyclability.
研究领域:
材料科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
POLYMER
·
2025
·
IF 4.5
Zi-Xuan Luo,Guo-Qiang Tian,Si-Chong Chen,Gang Wu,Yu-Zhong Wang
Biodegradable polyesters derived from cyclic monomers offer sustainable alternatives with closed-loop recyclability, yet practical implementation of conventional systems like polylactide (PLA) and poly( ε -caprolactone) (PCL) remains hindered by some challenges during depolymerization-repolymerization cycles. Herein, we present a solvent-free recycling strategy for mixed recyclable polyester plastics via catalytic alcoholysis and chain extension, yielding useable copolymer polyurethane (PLA/PCL-PU) with trade-off mechanical properties. Under a high-activity transesterification catalyst (i.e. tetrabutyl titanate), short-chain diol precursors (PLA/PCL-diol) were obtained from PLA and PCL mixtures and subsequently chain-extended with 1,6-diisocyanatehexane. The PLA/PCL-PU with a block copolymeric architecture characterized by diffusion-ordered spectroscopy and 13 C nuclear magnetic resonance exhibits enhanced thermal stability and crystallinity of the PLA segments due to the incorporation of PCL segments. Significantly, the resultant PLA/PCL-PU copolymers deliver good comprehensive mechanical properties with a tensile strength of up to 51.0 ± 0.8 MPa and an elongation at break of maximum 379.4 ± 29.1 %. The recycled materials demonstrate packaging preservation ability and 3D printability, with an outstanding biocompatibility. PLA/PCL-PUs can be depolymerized into the corresponding re-polymerizable monomers, showing chemical recyclability. This one-pot solvent-free recycling approach circumvents traditional depolymerization bottlenecks, offering an eco-friendly and simplified route to convert mixed plastics into high-value materials.
研究领域:
材料科学
·
环境科学
·
高分子化学
✓ 已验证
产品关联
DOI
高影响因子
BIOCHEMICAL ENGINEERING JOURNAL
·
2024
·
IF 3.7
Jiaojiao Sun,Yaxing Pang,Ziyi Lei,Bo OuYang,Wanxian Lai,Yonghua Wang,Dongming Lan
Advancing the efficiency of polyethylene terephthalate (PET) degradation is pivotal for sustainable and versatile PET recycling. In this study, we initially screened eight esterases , pinpointing Pyrobaculum calidifontis VA1 esterase (PCEST) as markedly effective in decomposing PET intermediate products. Building on this discovery, we engineered fusion proteins combining a robust cutinase (HRC) with PCEST, connected by flexible glycine-serine linkers. We further optimized the linker length, the sequential arrangement and the enzymatic conditions of the conjugated enzymes . Notably, the synergistic activity of the HRC-PCEST fusion protein significantly enhanced the breakdown of PET, thereby promising to streamline recycling processes. Collectively, this methodology not only propels the efficiency of PET degradation but also broadens the horizons for sustainable and versatile PET waste management protocols.
研究领域:
生物化学
·
环境科学
·
材料科学
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）