CATALYSIS SURVEYS FROM ASIA
·
2018
·Vol. 22
·期 4
·222-229
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IF 3.081
Gao Meixiang,Jiang Haoxi,Zhang Minhua
Series of ZrO 2 supported on the different kinds of SiO 2 carriers were applied in the reaction of 1, 3-butadiene formation from ethanol and acetaldehyde. ZrO 2 /Nano-SiO 2 performed the best performance with the 1, 3-butadiene selectivity 91.43% and the total conversation 52.39%. Prepared catalysts were characterized by N 2 adsorption–desorption, TEM, XRD, temperature-programmed desorption of NH 3 and CO 2 , FTIR spectroscopy of adsorbed pyridine and CO 2 , Raman XPS. The results show that the weak Lewis acid and basic sites are appropriate for BD formation. Furthermore, more and balance acid-basic sites are rather important for the reaction of ethanol and acetaldehyde conversion to BD.
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RSC Advances
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2018
·Vol. 8
·期 59
·34069-34077
·
IF 2.936
Minhua Zhang,Xuechao Tan,Tong Zhang,Zheng Han,Haoxi Jiang
A deactivation study on the ethanol/acetaldehyde conversion to 1,3-butadiene over a ZnO promoted ZrO2–SiO2 catalyst prepared by a sol–gel method was performed. The samples were characterized by N2 adsorption–desorption isotherms, scanning electron microscopy (SEM), NH3 temperature programmed desorption (NH3-TPD), X-ray powder diffraction characterization (XRD), thermogravimetric analyses (TGA), Fourier transform infrared resonance (FT-IR), 13C magic-angle spinning nuclear magnetic resonance (13C NMR) and X-ray photoelectron spectroscopy (XPS). The pore structure characteristics and surface acidity of Zn0.5–Zr–Si catalysts were largely decreased with time-on-stream and no crystal structure was formed in the used catalyst, indicating that the deactivation was caused by carbon deposition. Two main types of carbon deposition were formed, namely low-temperature carbon deposition with the oxidation temperature of around 400 °C and high-temperature carbon deposition with the oxidation temperature of 526 °C. The carbon species were mainly composed of graphitized carbon, amorphous carbon, carbon in C–O bonds and carbonyls. The deactivated catalyst could be regenerated by a simple oxidation process in air. Adding a certain amount of water into the feed had a positive effect on reducing the carbon deposition.
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Environmental Chemistry
·
2018
·Vol. 15
·期 7
·411-423
·
IF 2.923
Shuyan Wang,Lin Du,Narcisse T. Tsona,Wenxing Wang
Environmental context Acetate esters, emitted into the atmosphere from both natural and anthropogenic sources, can participate in photochemical processes leading to the formation of secondary organic aerosols. We report a study on the kinetics and mechanisms of the reaction of two acetate esters with O3, OH, NO3, and Cl radicals. The results help our understanding of the chemical behaviour of this important class of compounds in the atmosphere. The photodegradation reactions of isopropenyl acetate (IPA) and 2-methyl-2-propenyl acetate (MPA) initiated by O3, OH, Cl and NO3 radicals have been investigated in a 100 L Teflon reactor at 293 ± 3 K, by using gas chromatography with flame-ionisation detection as well as thermal desorption–gas chromatography–mass spectrometry to monitor the reactants and the products. The rate constants for the reactions of IPA and MPA with the four atmospheric oxidants were determined by using either absolute or relative rate methods. The following rate constants (in units of cm3 molecule−1 s−1) were obtained: k(O3 + IPA) = (0.37 ± 0.06) × 10−18, k(OH + IPA) = (6.44 ± 0.74) × 10−11, k(Cl+ IPA) = (4.33 ± 0.52) × 10−10, k(NO3 + IPA) = (1.62 ± 0.22) × 10−14, k(O3 + MPA) = (2.76 ± 0.40) × 10−18, k(OH + MPA) = (7.41 ± 0.92) × 10−11, k(Cl + MPA) = (3.33 ± 0.39) × 10−10, k(NO3 + MPA) = (1.34 ± 0.23) × 10−14. With the exception of the kinetic study of the reactions of O3 and OH with IPA and the mechanistic study of the reaction of IPA with O3, the current research reports the first kinetic and mechanistic investigation for these reactions at atmospheric pressure. Acetic anhydride and 1-acetoxyacetone are the main products of the reactions of IPA and MPA, respectively. On the basis of the products and estimated tropospheric lifetimes of the two esters, reaction mechanisms are proposed and the atmospheric implications are discussed.
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Canadian Journal of Chemistry
·
2018
·Vol. 96
·期 8
·
IF 1.084
Yongshu Li,Nizhou Xu,Guangyao Mei,Yun Zhao,Yiyong Zhao,Jinghui Lyu,Guofu Zhang,Chengrong Ding
A mild, simple process for the effective aerobic oxidative deoximation of a wide range of ketoximes and aldoximes has been developed that utilizes Fe(NO3)3·9H2O as the single catalyst and molecular oxygen as the green oxidant. The environmentally benign protocol provides moderate to excellent yield and broad functional groups tolerance and is a valuable synthetic method for practical applications. According the relevant verification experiment, a plausible mechanism has been proposed.
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NEW JOURNAL OF CHEMISTRY
·
2018
·Vol. 42
·期 11
·9140-9150
·
IF 3.201
Jiliang Ma,Xinwen Peng,Linxin Zhong,Runcang Sun
The application of biomass-based carbonaceous solid acids in catalysis is attracting increasing attention in the field of chemistry. In this study, a heterogeneous carbon-based solid acid biocatalyst (CXH-SO3H) with regular spherical structure was synthesized from xylan-type hemicellulose (XH) by a simple two-step method. The catalyst was successfully applied in the synthesis of O- and N-heterocycles with yields of 80–99% and 60–97%, respectively. In view of environment and economy, CXH-SO3H shows the merits of environmental friendliness, easy operation, simple work-up, excellent yields, and the avoidance of use of organic solvents and expensive catalysts. Moreover, the as-synthesized solid acid catalyst could be used for several cycles without significant loss in its catalytic activity. The results of FT-IR, XRD, and SEM showed that no distinct differences in physico-chemical structures of CXH-SO3H were observed. Thus, the eco-friendly CXH-SO3H catalyst is a promising candidate for green synthesis of O- and N-heterocycles from low-cost feed-stocks and has good prospect in partially substituting commercially available solid and liquid acid catalysts and precious metal catalysts.
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MOLECULES
·
2018
·Vol. 23
·期 5
·1066
·
IF 3.098
Lingxi Li,Minna Zhang,Shuting Zhang,Yan Cui,Baoshan Sun
Anthocyanin-flavanol pigments, formed during red wine fermentation and storage by condensation reactions between anthocyanins and flavanols (monomers, oligomers, and polymers), are one of the major groups of polyphenols in aged red wine. However, knowledge of their biological activities is lacking. This is probably due to the structural diversity and complexity of these molecules, which makes the large-scale separation and isolation of the individual compounds very difficult, thus restricting their further study. In this study, anthocyanins (i.e., malvidin-3-glucoside, cyanidin-3-glucoside, and peonidin-3-glucoside) and (–)-epicatechin were first isolated at a preparative scale by high-speed counter-current chromatography. The condensation reaction between each of the isolated anthocyanins and (–)-epicatechin, mediated by acetaldehyde, was conducted in model wine solutions to obtain ethyl-linked anthocyanin-flavanol pigments. The effects of pH, molar ratio, and temperature on the reaction rate were investigated, and the reaction conditions of pH 1.7, molar ratio 1:6:10 (anthocyanin/(–)-epicatechin/acetaldehyde), and reaction temperature of 35 °C were identified as optimal for conversion of anthocyanins to ethyl-linked anthocyanin-flavanol pigments. Six ethyl-linked anthocyanin-flavanol pigments were isolated in larger quantities and collected under optimal reaction conditions, and their chemical structures were identified by HPLC-QTOF-MS and ECD analyses. Furthermore, DPPH, ABTS, and FRAP assays indicate that ethyl-linked anthocyanin-flavanol pigments show stronger antioxidant activities than their precursor anthocyanins.Keywords:anthocyanin;antioxidant activity;ethyl-linked anthocyanin-flavanol pigment
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JOURNAL OF PHARMACOLOGY AND EXPERIMENTAL THERAPEUTICS
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2018
·Vol. 365
·期 2
·398-407
·
IF 3.706
Jie Gao,Zhao Wang,Gao-Ju Wang,Hong-Xin Zhang,Na Gao,Jie Wang,Cai-E. Wang,Zhao Chang,Yan Fang,Yun-Fei Zhang,Jun Zhou,Han Jin,Hai-Ling Qiao
Hepatocellular carcinoma (HCC) is one of the most common types of primary liver cancer and the third most frequent cause of cancer death worldwide. Diethylnitrosamine (DEN) is one of the recognized risk factors for hepatocarcinogenesis likely due to CYP2E1-mediated metabolic activation. However, CYP2E1-mediated DEN metabolic activity in non-neoplastic liver tissue from HCC patients has not been determined; the role of CYP2E1 activity, in particular CYP2E1 constitutive activity and CYP2E1 inhibited activity, with respect to the hepatocarcinogenesis induced by DEN is not yet clear. Herein, we determined CYP2E1-mediated DEN metabolic activity in non-neoplastic liver tissue from HCC patients and found that CYP2E1-mediated DEN metabolic activity was significantly elevated with a 43.3% positive rate, and clinicopathologic parameters did not affect the activity. Then, using a Sprague-Dawley rat liver tumor model induced by DEN, the relationship between CYP2E1 constitutive/inhibited activity and hepatocarcinogenesis was explored. The results showed that the CYP2E1 constitutive activity was strongly correlated with tumor incidence and severity of liver tumorigenesis (nodule numbers and size), whereas inhibition of CYP2E1 activity decreased hepatocyte proliferation, liver injury, and liver carcinogenesis in the presence of DEN. In conclusion, the higher CYP2E1 activity would lead to an increased incidence of HCC as a result of CYP2E1-mediated DEN activation. Therefore, higher CYP2E1 activity might be a risk factor for HCC induced by DEN.
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MICROPOROUS AND MESOPOROUS MATERIALS
·
2019
·
IF 4.182
Yeqing Wang,Jian Zhang,Xiangju Meng,Shichao Han,Qiuyan Zhu,Na Sheng,Liang Wang,Feng-Shou Xiao
In this work, we show sustainable and efficient synthesis of nanosized EMT zeolite under organotemplate-free and solvent-free conditions, which not only completely avoids the use of organic templates for production of NOx and CO 2 but also effectively reduces the formation of polluted water. In addition, the yield of EMT zeolite is significantly enhanced by this route, compared with conventional hydrothermal synthesis . The nanosized EMT zeolite obtained has good crystallinity, uniform crystal size distribution, and high surface area. Ion-exchange tests show that the nanosized EMT zeolite owes high Ca 2+ and Mg 2+ ion exchange capacity at room temperature, which is potentially important for softening hard water in the industrial processes. Catalytic tests in Knoevenagel condensation show that the nanosized EMT zeolite exhibits higher activity than that of the EMT zeolite synthesized using organic template, indicating the importance of the nanosized EMT zeolite as a base catalyst.
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ANALYTICAL CHEMISTRY
·
2017
·
IF 6.32
Zhengyi Chen,Gongke Li,Zhuomin Zhang
It still remains a great challenge for quantification of trace analytes in complex samples by surface-enhanced Raman scattering (SERS) technique due to potential matrix influence or weak SERS responses of analytes. In this work, a miniaturized thermal-assisted purge-and-trap (MTAPT) device was designed and developed to eliminate matrix influence coupled with derivatization method before SERS analysis. The design of MTAPT chamber was optimized based on quantitative calculation of its dead volume by computational fluid dynamics simulation. The small straight chamber was selected as an optimized design with a recovery of 96.1% for formaldehyde. The practical feasibility of MTAPT was validated based on four real analytical applications including phenthiol in industrial water, formaldehyde in flour, sulfion in wastewater, and methanol in industrial alcohol. The results showed that SERS responses of all analytes dramatically increased by eliminating sample matrices after MTAPT process. Phenthiol, formaldehyde, sulfion, and methanol in real samples could be accurately quantified with recoveries of 80.9–110.0%, and the analytical results were validated by corresponding standard methods. The time consumption of MTAPT-SERS for real sample analysis including sample preparation and determination was within 16 min. It is highly expected that the combination of MTAPT technique with portable SERS instrument can greatly expand the range of SERS analysis. The proposed MTAPT-SERS method has high potential for on-site analysis of complex samples.
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ANALYTICA CHIMICA ACTA
·
2017
·
IF 4.95
Yao Sun,Zhaobing Guan,Hongwei Cai,Yiyong Huang,Yawei Lin,Xiaosong Hu
A pre-column fluorescent derivatization method based on nitrone formation has been applied to determine furfurals (e.g. furfural (F), 5-methyfurfural (5-MF) and 5-hydroxymethylfurfural (5-HMF)) in food samples for the first time. An N-substituted hydroxylamine reagent 4-((hydroxyamino)butyl)-7-hydroxycoumarin (HAHC) was used to react with the aldehyde group of furfurals to form stable nitrone derivatives with high fluorescence intensities . The reactions proceeded under mild conditions in 30 min with high derivatization yields (>93%). A baseline-separation of three furfurals derivatives was subsequently achieved within 25 min on a reversed-phase column. The detection limits were at the low femtomol level (S/N = 3, 20 μL per injection). The linear range of the calibration curve was 0.4–4000 nM with good correlation coefficients (R 2 ≥ 0.9991). The proposed method was further applied for food sample analysis, such as bovine milk powder and raisin. Satisfactory recoveries were obtained in the range of 94.7%–103.5%. Above all, this pre-column derivatization method is simple, fast and highly sensitive, providing an effective and promising way for future studies of aldehydes in different matrices.
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TALANTA
·
2024
·
IF 5.6
Hao-Jie Bai,Hong-Wei Li,Yi Li,Zhijiu Huang,Sha Liu,Xin-He Duan,Yuqing Wu
Detecting the furfural concentration in Baijiu can be used to assess the quality of Baijiu , allowing for the optimization of processing techniques and the enhancement of overall quality. In this paper, a fluorescence-enhanced method based on carbon dots ( o -CDs) is developed for the furfural determination in Chinese Baijiu . In an environment full-filled with · SO 4 ‐ and · OH , furfural undergone a direct surface reaction with the ortho -diamino groups at o -CDs. The created furan-based imidazole increased the surface electron density, leading an emission enhancement and color changes from orange to green. Thereby, a linear fluorescence response of o -CDs-TA to furfural is established in water with a detection limit of 30.5 nM. Finally, after ethanol correction it is used to determine furfural in Chinese Baijiu with high precision and reproducibility, providing a new strategy with low-cost and high sensitivity. In particular, the idea of covalently connecting target molecule to the CDs surface via the assistance of free radical opens a new avenue to merge the nanoscale and molecular realms through implementing chemical role into carbon nanostructures.
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ANALYTICA CHIMICA ACTA
·
2025
·
IF 6
Xuhui Xia,Peng Zhao,Jia Zheng,Xuheng Li,Xin Zeng,Dianhui Men,Yiyao Luo,Changjun Hou,Danqun Huo
Background Discriminating the quality of baijiu is critical for fostering the growth of the China baijiu market and safeguarding customers' rights. However, establishing a small-scale and rapid baijiu discriminating sensor assay still remains a challenge. Results Here, we first introduced ratiometric fluorescence sensor array for the detection of reducing substances in baijiu to achieve baijiu discrimination. A ratiometric fluorescence sensor array is built using 2,3-diaminophenazine (oxidized-state OPD, oxOPD) to quench three distinct fluorescence signals of quantum dots while reducing interference from background signals. The reducing chemicals in baijiu can react with Ag + , weakening the quenching effect and changing the ratio. The discriminating of 12 types of organic small molecules which were presented in baijiu was achieved with 97.2 % accuracy by using machine learning classification methods. Meanwhile, 0.1 μM limit of detection (LOD) for ascorbic acid shows that our methods have the potential to quantitative detect reducing substances. In real sample detection, our methods can discriminate 10 distinct qualities of baijiu with 100 % accuracy. We also encoded the fingerprints of different varieties of baijiu for quality control and information reading. Significance and novelty Overall, our easy but robust sensing array not only overcomes the problem of background signal interference but also gives an ideal way for discriminating different qualities of baijiu, food and other areas.
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危险品化学品经营许可证（带存储）