ANALYTICAL BIOCHEMISTRY
·
2018
·
IF 2.275
Jianyong Zheng,Wei Wei,Xing Lan,Yinjun Zhang,Zhao Wang
This study describes a sensitive and fluorescent microplate assay method to detect lipase transesterification activity. Lipase-catalyzed transesterification between butyryl 4-methyl umbelliferone (Bu-4-Mu) and methanol in tert -butanol was selected as the model reaction. The release of 4-methylumbelliferone (4-Mu) in the reaction was determined by detecting the fluorescence intensity at λ ex 330 nm and λ em 390 nm. Several lipases were used to investigate the accuracy and efficiency of the proposed method. Apparent Michaelis constant ( K m) was calculated for transesterification between Bu-4-Mu and methanol by the lipases. The main advantages of the assay method include high sensitivity, inexpensive reagents, and simple detection process.
研究领域:
生物化学
·
酶学
✓ 已验证
DOI
PubMed
高影响因子
AICHE JOURNAL
·
2020
·Vol. 66
·期 9
·e16292
·
IF 3.519
Xin Yuan,Yu Liu,Fan Cao,Panliang Zhang,Jian Ou,Kewen Tang
Enzyme immobilization enhances the catalytic activity and stability of the enzyme, and also improves reusability. Metal–organic frameworks (MOFs), which possess diversified structures and porosity, have been used as excellent carriers for enzyme immobilization. Pseudomonas fluorescens lipase (PFL) has been successfully immobilized onto MOFs by covalent cross-linking to obtain a series of immobilized lipase (PFL@MOFs). PFL@MOFs are used for catalytic enantioselective hydrolysis of 2-(4-hydroxyphenyl) propionic acid ethyl ester enantiomers (2-HPPAEE) in aqueous medium and transesterification of 4-methoxymandelic acid enantiomers (4-MMA) in organic medium. The experimental results indicated that PFL@Uio-66(Zr) exhibits excellent enzymatic catalysis performances and high enantioselectives. In addition, to improve catalytic activity and reusability, PFL is modified by the polyethylene glycol (PEG) to prepare PEG-modified lipase (PFL-PEG), then PFL-PEG is immobilized onto Uio-66(Zr) to prepare PFL-PEG@Uio-66(Zr), demonstrating better reusability and catalytic activity compared with PFL@Uio-66(Zr).
研究领域:
生物化学
·
酶工程
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
FUEL
·
2020
·
IF 5.578
Yue Yu,Lei Shi,Jianjun Guo,Xin Li,Wenbing Yang,Zhigang Zhang,Guangwen Xu
Soluble strong bases such as NaOH or CH 3 ONa were industrially applied in production of multiple carbonates via the transesterification route. However, the catalytic efficiency decreased significantly after recycling and insoluble solids were formed, leading to a complicated and non-eco-friendly manufacture process. In this study, the influence of Na-based soluble basic catalysts (C 4 H 9 ONa, C 2 H 5 ONa, CH 3 ONa, NaOH, Na 2 CO 3 , and NaHCO 3 ) structures, amounts, reusability, reaction atmospheres, and different reactants treatment were systematically studied for in-depth understanding the deactivated processes and mechanism. The results indicated dimethyl carbonate (DMC) was responsible for the deactivation and with decreasing the pK b (alkalinity coefficient) value, the alkali strength, nucleophilicity, and catalyst efficiency increased. The properties of fresh, DMC-treated and recycled NaOH or CH 3 ONa samples were characterized by means of XRD, FT-IR, Raman, TG, and SEM. Nearly all the characterizations proved that the final deactivation species was Na 2 CO 3 after long-time treatment or recycle. A possible deactivation mechanism of soluble bases during the transesterification process was proposed. The presence of trace H 2 O was the induction of CH 3 ONa deactivation, whereas the interaction between DMC and NaOH led to the formation of Na 2 CO 3 . This finding will contribute to the development of strategies to design homogeneous catalysts with high activity and stability for carbonate transesterification.
研究领域:
化学工程
·
催化化学
✓ 已验证
产品关联
DOI
高影响因子
CHINESE JOURNAL OF CHEMICAL ENGINEERING
·
2022
·
IF 3.898
Tengjie Wang,Wenkai Li,Xuehui Ge,Ting Qiu,Xiaoda Wang
High-purity ethylene carbonate (EC) is widely used as battery electrolyte, polycarbonate monomer , organic intermediate, and so on. An economical and sustainable route to synthesize high-purity ethylene carbonate (EC) via the transesterification of dimethyl carbonate (DMC) with ethylene glycol (EG) is provided in this work. However, this reaction is so fast that the reaction kinetics, which is essential for the industrial design, is hard to get by the traditional measuring method. In this work, an easy-to-assemble microreactor was used to precisely determine the reaction kinetics for the fast transesterification of DMC with EG using sodium methoxide as catalyst. The effects of flow rate, microreactor diameter, catalyst concentration, reaction temperature, and reactant molar ratio were investigated. An activity-based pseudo-homogeneous kinetic model, which considered the non-ideal properties of reaction system, was established to describe the transesterification of DMC with EG. Detailed kinetics data were collected in the first 5 min. Using these data, the parameters of the kinetic model were correlated with the maximum average error of 11.19%. Using this kinetic model, the kinetic data at different catalyst concentrations and reactant molar ratios were predicted with the maximum average error of 13.68%, suggesting its satisfactory prediction performance.
研究领域:
化学工程
·
材料科学
·
反应动力学
✓ 已验证
产品关联
DOI
高影响因子
BIORESOURCE TECHNOLOGY
·
2014
·
IF 5.039
Binbin Jin,Peigao Duan,Yuping Xu,Bing Wang,Feng Wang,Lei Zhang
The activities of several Lewis acid catalysts such SnCl 2 , FeCl 3 , ZnCl 2 , AlCl 3 , and NbCl 5 for the in situ transesterification/esterification of lipid contained within a microalga ( Chlorella pyrenoidosa ) in ethanol at 350 °C were examined to identify the most suitable catalyst in term of crude biodiesel (CBD) yield. Of those catalysts tested, ZnCl 2 showed the highest performance toward the CBD production. Using ZnCl 2 as catalyst, effects of reaction temperature (200–370 °C), time (0–120 min), ethanol to microalga ratio (EtOH:MA) (5/5–40/5), catalyst loading (0–30 wt.%), and algae moisture (0–80 wt.%) on the yields of product fractions and the properties of CBD were studied. The presence of ZnCl 2 not only promoted the production of CBD but also showed activities toward the deoxygenation and denitrogenation of CBD. The moisture content in the starting material is the most influential factor affecting the yield and properties of CBD.
研究领域:
生物化学
·
可再生能源
·
催化化学
✓ 已验证
DOI
PubMed
高影响因子
Scientific Reports
·
2018
·Vol. 8
·期 1
·1-6
·
IF 4.122
Fu Feiya,Huang Meiqi,Zhang Weilan,Zhao Yang,Liu Xiangdong
A self-healing polybenzoxazine is synthesized solely based on dynamic ester bonds. For this purpose, an anhydride (succinic anhydride) was added into bisphenol F derived benzoxazine monomer before thermocuring. Owing to the transesterification of newly formed ester bonds, the thermoset network behaves as a thermoplastic at 140 °C in the presence of Zn (Ac) 2 , and shows self-healing properties even after multiple damage-healing cycles. Furthermore, kinetics study indicates that the transesterification is a first-order reaction and the activation energy is about 135.4 kJ/mol. This study proposes a facile and economical way to prepare self-healing polybenzoxazine. It has promising applications in coating, adhesive, and other smart materials that rely on structurally dynamic polymers.
研究领域:
材料科学
·
化学工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
NEW JOURNAL OF CHEMISTRY
·
2018
·Vol. 43
·期 1
·330-337
·
IF 3.201
Chaoping Yuan,Wentao Shi,Peng Chen,Huaxin Chen,Lihua Zhang,Gang Hu,Longming Jin,Haibo Xie,Qiang Zheng,Shengjun Lu
Cellulose dissolution is crucial for its regeneration and the application of its derivative materials. In this study, the dissolution of cellulose in γ-valerolactone (GVL), promoted by 1-ethyl-3-methylimidazolium acetate ([Emim]OAc), was investigated and 15 wt% α-cellulose was rapidly dissolved by the designed mixed organic electrolyte solvents (OESs) at 80 °C in 1 h. The rheological study indicated that the activation energy of dissolution is lower than that in pure [Emim]OAc, and the overlap concentration was determined to be C* = 1.7 wt%. The viscosity of the α-cellulose solution overlapped well with the complex viscosity, suggesting that the Cox–Merz law is valid therein. The potential of the solution for homogeneous derivatization through transesterification of α-cellulose with vinyl esters was also investigated at 80 °C in 4 h with a low vinyl ester/anhydroglucose unit (AGU) molar ratio of 3, achieving a cellulose laurate ester with a DS = 3.0, cellulose pivalate ester with a DS = 3.0 and cellulose chloroacetate ester with a DS = 1.43.
研究领域:
化学工程
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
ChemSusChem
·
2019
·Vol. 12
·期 6
·1169-1178
·
IF 7.804
Wei Qian,Xin Tan,Qian Su,Weiguo Cheng,Fei Xu,Li Dong,Suojiang Zhang
Graphical Ecofriendly catalysts : The ionic liquids [P 66614 ][4-R-Phen] (R=H, F, Cl, Br, I) with weak alkalinity can activate not only isosorbide but also dimethyl carbonate, thereby achieving the more reactive isosorbide-based polycarbonate precursor dicarboxymethyl isosorbide with high selectivity. This strategy may allow the development of other ionic liquids for transesterification reactions, providing various polymers through a green synthetic pathway. Green synthesis of high-molecular-weight isosorbide-based polycarbonate (PIC) with excellent properties is a tremendous challenge and is profoundly influenced by the precursor. Herein, an ecofriendly catalyst was employed to obtain the more reactive PIC precursor dicarboxymethyl isosorbide (DC) with 99.0 % selectivity through the transesterification reaction of isosorbide with dimethyl carbonate. This is the indispensable stage of a one-pot green synthesis of PIC, playing a critical role in giving an insight into the polymerization mechanism of polymer synthesis through the melt transesterification reaction. To this end, a series of 4-substituted phenolate ionic liquids (ILs) were developed as a new type of high-efficiency catalyst for this reaction. These homogeneous ILs exhibited outstanding catalytic performances. The DC selectivity increased gradually with decreasing IL basicity; among the ILs studied, trihexyl(tetradecyl)phosphonium 4-iodophenolate ([P 66614 ][4-I-Phen]) showed the highest catalytic activity. Additionally, according to the experimental results and DFT calculations, a plausible nucleophilic activation mechanism was proposed, which confirmed that the reaction is activated through the formation of H-bonds and electrostatic interactions with the IL catalyst. This strategy of tunable basicity and structure of anions in ILs affords an opportunity to develop other ILs for the transesterification reaction, thereby conveniently providing a variety of polymers through a green synthetic pathway.
研究领域:
化学
·
材料科学
·
环境科学
·
高分子科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
CHEMICAL ENGINEERING & TECHNOLOGY
·
2022
·Vol. 45
·期 10
·1842-1849
·
IF 2.215
Junteng Ma,Weihua Shen,Wenxuan Wei,Yunjin Fang
The catalytic activity of an ionic liquid catalyst decreased during the transesterification of propylene carbonate (PC) with methanol to dimethyl carbonate (DMC). The interaction between the strong basic sites of ionic liquid catalyst and carbonyl compounds of PC and/or DMC was considered to attribute to this deactivation. The presence of H 2 O accelerated this process by the formation of OH – . The strong basic ionic liquid reacted with the trace amount of H 2 O in the reaction system to generate OH – , which then reacted with the carbonyl structure in PC and/or DMC to form the inactive compound HCO 3 – , resulting in the deactivation of the ionic liquid catalyst. A plausible mechanism was proposed for the deactivation of the ionic liquid catalyst in this reaction.
研究领域:
化学工程
·
催化
·
绿色化学
✓ 已验证
产品关联
DOI
高影响因子
FLUID PHASE EQUILIBRIA
·
2022
·
IF 2.745
Jingjun Liu,Dandan Pan,Qing Zhang,Yulei Guan,Bolun Yang
Glycerol carbonate is a value-added glycerol derivative, which can be obtained by transesterification with dimethyl carbonate. Phase splitting and merging exist in the transesterification due to the low solubilities of glycerol with dimethyl carbonate. The isobaric liquid-liquid equilibrium data for two ternary systems (glycerol – dimethyl carbonate – glycerol carbonate/methanol) and one quaternary system (glycerol – dimethyl carbonate – glycerol carbonate – methanol) involved in the glycerol transesterification were measured at reaction relevant temperatures (333.2, 353.2, 373.2, and 393.2 K) and 1.5 MPa. The equilibrium data were correlated using the NRTL model to calculate activity coefficients, with temperature-dependent interaction parameters, which were estimated through data regression and validated by checking the consistency of the Gibbs free energy. The NRTL model with the regressed parameters could reproduce the phase equilibrium trends of all the studied systems.
研究领域:
化学工程
·
热力学
✓ 已验证
产品关联
DOI
高影响因子
RSC Advances
·
2014
·Vol. 4
·期 104
·60025-60033
·
IF 3.708
Juan Chen,Lihua Jia,Xiangfeng Guo,Lijun Xiang,Shengfeng Lou
A series of KF-modified Ca–Al hydrotalcite (xKF/HTL-M) solid base catalysts was prepared in methanol, and characterized by thermogravimetry analysis (TG-DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and carbon dioxide temperature-programmed desorption (CO2-TPD). The catalytic activity was investigated in the transesterification of ethylene glycol monomethyl ether (EGME) with methyl laurate (ML) to produce a novel biodiesel of ethylene glycol monomethyl ether monolaurate (EGMEML). The effect of the mass content of KF and the main reaction parameters such as EGME to ML molar ratio, amount of catalyst, reaction time and temperature on the yield of EGMEML were examined. The results indicate that a new phase of KCaF3 formed in xKF/HTL-M, and acted as the main active sites for the transesterification. In addition, xKF/HTL-M has excellent catalytic performance in the production of EGMEML. The highest yield of 97.7% was obtained over 24.7KF/HTL-M at EGME/ML molar ratio of 3.0, catalyst amount of 5 wt%, and reaction time of 4 h at 120 °C. Moreover, the catalyst displays a good stability and reutilization. A satisfactory yield of 90% was obtained after use for five consecutive cycles without significant deactivation. Finally, the activation energy (Ea) of the reaction of EGME with ML over 24.7KF/HTL-M was obtained as 27.11 kJ mol−1.
研究领域:
化学工程
·
催化材料
✓ 已验证
DOI
高影响因子
JOURNAL OF APPLIED POLYMER SCIENCE
·
2021
·Vol. 138
·期 39
·51010
·
IF 3.125
Yue Yin,Jian Yang,Linghui Meng
Poly(butylene succinate) (PBS) refers to a high-performance biodegradable polymer employed to substitute petroleum polymers that cause environmental issues. However, PBS exhibits the defect of flowing above the melting point and rapid dripping for its poor melt strength. Accordingly, this study proposed a novel method to fabricate PBS vitrimer by exploiting reactive extrusion technology to mix diepoxide with PBS and then by employing zinc acetate as a catalyst to crosslink the PBS. Therefore, after the reaction extrusion blending, the blend still has a lower viscosity and high processing performance; in the subsequent curing process, the polymer undergoes a transesterification reaction and the viscosity increases. Via transesterification to form a cross-linked network, the storage modulus, and loss modulus of PBS vitrimer at 140°C reach 55,800% and 3500% of pure PBS, respectively. At this time, the crystallinity of PBS vitrimer is still as high as 56.9% (The crystallinity of pure PBS is 47.4%). And the shape stability of PBS at high temperatures was significantly improved. Moreover, PBS vitrimer could still be reshaped after the cross-linking process. This study proposed a facile method to produce PBS materials exhibiting high thermal shape stability.
研究领域:
材料科学
·
高分子化学
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）