Molecular Catalysis
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2018
·
IF 0
Shanshan Jie,Congqiang Yang,Yuan Chen,Zhigang Liu
The highly dispersed active sites are desirable to optimize the atom efficiency. In this study, a series of novel cobalt grafted in N-doped carbon (Co-N-C) catalysts for selective oxidation of ethylbenzene are synthesized by heating a solution of cobalt porphyrin and peptides in ionic liquids, which are also characterized by techniques such as FT-IR, XRD, SEM-EDX, HR-TEM, and XPS. The results show that the as-prepared catalysts have an attractive catalytic performance, namely, 40% of ethylbenzene conversion and 75% of selectivity to acetophenone. Especially, the activity and selectivity of the as-prepared catalysts remain almost similar even after the 10th run. Moreover, the modified-complexometry method is verified to improve the dispersion of metal active sites. The remarkable catalytic performance of the as-prepared catalysts is attributed to the highly dispersed active sites and strong interactions between Co and N species in Co-N x moieties.
研究领域:
催化
·
材料科学
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化学工程
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分析化学
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产品关联
DOI
APPLIED CATALYSIS B-ENVIRONMENTAL
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2024
·
IF 20.2
Lin Wang,Hao Jiang,Jun Zhang,Xinhua He,Fangfang Li,Jing Feng,Bo Pan
Dissolved black carbon (DBC) can generate reactive oxygen species (ROS), playing significant roles in contaminants degradation and chemical stresses to microorganisms. However, little is known regarding the photoproduction sites to ROS generation, mainly because of its extremely complicated composition. Herein, the ROS generation and photoexcited alteration of DBC were investigated. The generation mechanisms of hydroxyl radical (•OH), superoxide anion (O 2 •− ) and singlet oxygen ( 1 O 2 ) were inferred by employing various model chemicals. Results showed that the photo-excited aliphatic carbonyls greatly contributed to ∙OH, O 2 •− , and 1 O 2 generation. Ether groups were identified as the main structural source of H 2 O 2 -dependent ∙OH generation. The novel non-electron transfer process involved carbonyl, ether, alcohol, and ester groups to produce O 2 •− was proposed. These findings reveal the vital role of oxygenated functional groups within DBC in the photoactive generation of ROS, and thus provides new theoretical information for DBC’s environmental geochemical behavior.
研究领域:
环境科学
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化学
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地球化学
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产品关联
DOI
高影响因子
CHEMICAL ENGINEERING SCIENCE
·
2026
·
IF 5.1
Wenna Tang,Letao Guo,Lixia Yang,Liewei Qiu,Hongchen Liu,Mei Yang
Ester enolates, generated by lithium diisopropylamide (LDA)-mediated deprotonation of the α-hydrogen of esters, serve as highly reactive intermediates for C-C bond formation. However, they readily undergo self-condensation and decomposition, substantially reducing product yields, particularly in reactions with electrophiles that exhibit intrinsically slow kinetics. However, the key factors governing these side reactions, especially across esters with diverse structural features, remain insufficiently understood, limiting the rational design of effective suppression strategies. Here, we systematically studied the consumption behavior of enolates derived from esters with diverse structural features and developed tailored strategies to maintain high enolate concentrations over extended reaction times, several of which leveraged microreactor-based enolate generation. Using ethyl acetate (EA)-derived enolates, the most susceptible to side reactions, as a model, key factors governing enolate depletion in batch operation were identified, including insufficient mixing, excessive LDA consumption, and localized alkaline environments. Guided by these insights, a hybrid strategy operable under cryogenic conditions that coupled continuous-flow enolate generation with batch reaction time extension for EA-derived enolates were developed. Rapid mixing in continuous flow efficiently engaged most of the LDA in EA-derived enolate formation, thereby suppressing both self-condensation and decomposition. This hybrid approach sustained elevated EA-derived enolate concentrations for more than 60 min, outperforming conventional batch protocols. Subsequently, ester-specific enolate generation and preservation strategies for structurally diverse esters based on their distinct consumption pathways were established. Finally, using EA as a representative case, this tailored strategy significantly improved the yield of slow-kinetic Claisen condensation to the corresponding β-keto ester within 60 min.
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DOI
高影响因子
JOURNAL OF CATALYSIS
·
2016
·
IF 7.354
Haoran Yuan,Xiang Fang,Qiyi Ma,Jianyong Mao,Kexian Chen,Zhirong Chen,Haoran Li
The mechanism for aerobic oxidation of methylaromatic compounds using Co(CH 3 COO) 2 –Mn(CH 3 COO) 2 –KBr was further studied. The experimental results suggested that the intermediates (aromatic alcohols) are unexpectedly inert to direct oxidation via Co–Mn–Br catalysts under moderate conditions. In addition, it is found that both aromatic and aliphatic alcohols can inhibit the oxidation of the substrates and other intermediates (aromatic esters, aromatic aldehydes). UV–vis spectra indicated that oxidation from Co(II) to Co(III) would be interrupted in the presence of a given amount of alcohol. A plausible mechanism was also proposed. The intermediates analyzed by LC–MS and control experiments showed that aromatic alcohols prefer to undergo esterification rather than being directly oxidized as described in previous studies, and aromatic acetates are subsequently oxidized to corresponding aldehydes. According to the new mechanism, a strategy of highly selectively synthesizing aromatic alcohols and aldehydes from corresponding methylaromatic compounds was designed. The selectivities of aromatic alcohols and aldehydes could also be tuned by the added amount of CH 3 COOK.
研究领域:
催化化学
·
有机化学
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产品关联
DOI
高影响因子
Molecular Medicine Reports
·
2016
·Vol. 15
·期 1
·387-395
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IF 1.559
Bing Wang,Rui‑Ning Yang,Yue‑Rong Zhu,Ji‑Cheng Xing,Xiao‑Wei Lou,Yu‑Jie He,Qi‑Long Ding,Ming‑Yue Zhang,Hong Qiu
Xanthine oxidase (XOD) and paraoxonase 1 (PON1) are important enzymes in redox reactions in vivo, and are predominantly synthesized by the liver. The aim of the present study was to investigate the redox state in nonalcoholic fatty liver disease, and determine the association between the activities of XOD and PON1 and the severity of NAFLD. Sprague‑Dawley rats were randomly divided into control, model and α‑lipoic acid (high and low dose) groups. The rats in the NAFLD model were induced by feeding a high fat diet for 12 weeks and the in vitro cell model of hepatocyte steatosis was induced by treating L‑02 cells with oleic acid for 24 h. The body weight, liver function, lipid and oxidative stress indices, and histological features of the liver were examined in the rats. Compared with the control group, the rats in the NAFLD model group showed impaired liver function, lipid disorders and damage from oxidative stress. The serum activity of XOD increased significantly from the 4th week and was markedly higher, compared with that in the control group, reaching a peak in the 12th week. The activity of PON1 was negatively correlated with that of XOD. Compared with the control cells, the activity of XOD and levels of free‑fatty acids were significantly higher, and the activity of PON1 was significantly lower in the NAFLD L‑02 cell model. All the above indicators were significantly improved by treatment with the antioxidant, α‑lipoic acid. The activities of XOD and PON1 may be promising as markers in a noninvasive approach for detecting the severity of NAFLD clinically. α‑lipoic acid had protective effects on the NAFLD rats, and the potential mechanism may be associated with the inhibition of oxidative stress and lipid peroxidation.
研究领域:
肝病学
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生物化学
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药理学
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产品关联
DOI
PubMed
高影响因子
ORGANIC PROCESS RESEARCH & DEVELOPMENT
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2020
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IF 3.023
Yuanyuan Zhang,Yangjian Sun,Hui Tang,Qiuxiang Zhao,Wenjie Ren,Kuiying Lv,Fengke Yang,Fanye Wang,Junhong Liu
The dynamic covalent kinetic resolution protocol was efficiently used for the synthesis of the enantiopure ((R)-5-acetoxy-1,3-oxathiolan-2-yl)ethyl benzoate (PR) from substrates 2-(phenylmethoxy)acetaldehyde (A), 1,4-dithiane-2,5-diol (B), and phenyl acetate (D) by a one-pot process with 99.6% conversion, 97.3% yield, and 96.5% ee through the combination of reversible hemithioacetal transformation and enantiomer-selective lactonization catalyzed by immobilized lipase from Trichosporon laibachii. A proposed kinetic model consisting of transformation and lactonization was developed herein for the first time, fitting the experimental data very well. It was concluded that (1) the transformation in a chemical fashion may follow a power law. (2) The enzymatic lactonization may follow a sequential mechanism with product inhibition. The reaction kinetic data reveal that phenol (P1) would have strong product inhibition, while noncompetitive inhibition, product inhibition of PR, and substrate inhibition were not recognized. The model suggests that there is a common limitation of both enzyme and chemistry in the chemo-enzymatic system, and thus the amount of lipase was increased to accelerate the enzymatic lactonization and to reduce the limitation caused by the enzymatic reaction, resulting in the increase of the yield of PR significantly. The experimental results demonstrate that both the internal and external mass diffusion resistance could be negligible, and thus the kinetic model developed is the inherent kinetic one.
研究领域:
生物化学
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有机合成
·
酶工程
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DOI
高影响因子
AMB Express
·
2021
·Vol. 11
·期 1
·1-10
·
IF 3.298
Yao Jian,Gui Lun,Yin Shaocheng
A novel esterase gene was isolated from a soil metagenomic library. The gene encoded a protein of 520 amino acids which contained a 21 aa signal peptide. Primary structure analysis of the protein sequence revealed that it contained a conserved active site motif (SxSxG) and a structural motif (CS-D-HC). Then the esterase gene was cloned and expressed in Escherichia coli BL21(DE3). SDS-PAGE analysis of the purified esterase showed that it was expressed in a highly soluble form and its molecular mass was estimated to be 55 kDa. Characterization of the esterase revealed that it exhibited high activity toward p-nitrophenyl esters with short acyl chains and especially p-nitrophenyl acetate, suggesting that it was a typical carboxylesterase rather than a lipase. With p-nitrophenyl acetate as substrate, the enzyme showed its optimal activity at pH 7.0 and 30 °C, and it was stable at a broad pH range from 4.5 to 10.0 and temperature not higher than 50 °C. Furthermore, the enzyme showed different substrate specificity from known esterase, it was not only hydrolyzing against p-nitrophenyl esters, but also hydrolyzing all hydroxybenzoic esters and hydroxycinnamic ester assayed. As it was an enzyme active on a broad range of phenolic esters, simultaneously possessing feruloyl esterase, chlorogenate esterase and tannase activities, it could serve as a valuable candidate for applications in biotechnology.
研究领域:
生物化学
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环境微生物学
·
酶工程
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产品关联
DOI
PubMed
高影响因子
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