JOURNAL OF CHROMATOGRAPHY A
·
2016
·
IF 3.926
Tao Bao,Pingxiu Tang,Deying Kong,Zhenkun Mao,Zilin Chen
Covalent-organic frameworks (COFs) are attractive materials for their fascinating properties, such as rigid structures, exceptional thermal stabilities, low densities, and permanent porosity with specific surface areas, which indicate potential for application in chromatography similar to related metal-organic frameworks (MOFs). However, the utilization of COFs in analytical chemistry is far behind as compared to that of the MOFs due to the challenging work of their immobilization. Here, we have successfully demonstrated the growth of the boron COF-5 on the inner wall of the fused silica capillary by a developed polydopamine-supported method. Combined with the layer-by-layer strategy, multilayer COF-5-coated capillary was obtained. The formation of COF-5 on polydopamine-coated substrate has been confirmed by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction. A novel stationary phase of COF-5 was developed on the basis of successful growth of COF-5 on polydopamine for open-tubular capillary electrochromatography (OT-CEC). Baseline separation of neutral, acidic and basic analytes was achieved on multilayer COF-5-coated capillary column. The fabricated capillary columns showed high column efficiency (154,060 plates/m for methylbenzene), excellent stability and repeatability. The precision (relative standard deviation (RSD), n = 3) of retention time, peak height, and peak area for tested neutral compounds were in the range of 1.2–1.3%, 1.8–4.2%, and 0.9–2.4%, respectively. To the best of our knowledge, it was the first demonstration that COF-5 was developed as a novel stationary phase.
✓ 已验证
产品关联
DOI
PubMed
高影响因子
COMBUSTION AND FLAME
·
2016
·
IF 4.168
Wenhao Yuan,Yuyang Li,Gaëlle Pengloan,Casmir Togbé,Philippe Dagaut,Fei Qi
The flow reactor pyrolysis and jet-stirred reactor (JSR) oxidation of ethylbenzene are investigated in this work. The flow reactor pyrolysis is studied at pressures of 0.04, 0.2, and 1.0 atm and temperatures from 850 to 1500 K using synchrotron vacuum ultraviolet photoionization mass spectrometry . The jet-stirred reactor oxidation is studied at 1 atm with three equivalence ratios ( ϕ = 0.5, 1.0, and 1.5) and at 10 atm with the equivalence ratio of 1.0, using gas chromatography and Fourier transform infrared spectroscopy for mole fractions measurements. A detailed kinetic model of ethylbenzene pyrolysis and oxidation is developed by extending our recently reported oxidation models for toluene and styrene , and is validated on the new experimental data reported here. The benzyl radical and styrene are demonstrated to be the most important intermediates in both the pyrolysis and oxidation of ethylbenzene. For the JSR oxidation of ethylbenzene, the low temperature chemistry is found to play a significant role at 10 atm. The present model is also validated on the experimental data from the literature, including the species concentration profiles and global combustion parameters such as ignition delay times and laminar flame speeds. The good performance of the model for reproducing these data reveals its ability to predict ethylbenzene combustion over a wide range of conditions.
✓ 已验证
产品关联
DOI
高影响因子
MICROCHIMICA ACTA
·
2017
·Vol. 184
·期 4
·1169-1176
·
IF 4.58
Kong Deying,Bao Tao,Chen Zilin
The covalent organic framework LZU1 (Lan Zhou University-1) is one of the imine-based covalent organic frameworks (COFs) that possesses attractive properties such as structural regularity, stability and good porosity. This work reports on the in-situ synthesis of COF-LZU1 on the inner walls of capillary column for open-tubular capillary electrochromatography (OT-CEC). The fused-silica capillary was first modified with 3-aminopropyltriethoxysilane and glutaraldehyde. Epitaxial growth of COF-LZU1 on the inner walls was accomplished by Schiff base reaction. The formation of COF-LZU1 was confirmed by SEM and FT-IR. The COF-LZU1 coating increases the interactions between analytes and coating, which remarkably improves the CEC separation selectivity of neutral analytes, amino acids and nonsteroidal anti-inflammatory drugs. The COF-LZU1-modified column exhibits good stability and repeatability. The precisions (relative standard deviations) for intra-day, inter-day and column-to column are <1.6%, 5.6% and 6.8%, respectively. Hence, the imine-based COFs represent attractive stationary phase for application in CEC separations.
Covalent organic framework (COF-LZU1) was in situ synthesized on the inner wall of a capillary column for electrochromatographic separation of nonsteroidal drugs and amino acids.
✓ 已验证
产品关联
DOI
高影响因子
TALANTA
·
2016
·
IF 4.035
Tao Bao,Pingxiu Tang,Zhenkun Mao,Zilin Chen
A novel capillary column with metal-organic framework-5 (MOF-5) as the stationary phase was prepared for open-tubular capillary electrochromatography (OT-CEC). To grow MOF-5, the fused-silica capillary was functionalized firstly using 3-aminopropyltriethoxysilane and glutaraldehyde as covalent linkers; and then MOF-5 would be immobilized on the inner wall of COOH-terminated capillary by epitaxial growth , to produce a MOF-5-modified capillary. The successful growth of MOF-5 has been characterized and confirmed by scanning electron microscopy, X-Ray diffraction and Fourier transform infrared spectra . The influence of pH value and methanol on electroosmotic flow (EOF) of the MOF-5-modified capillary column was investigated. The EOF showed a pH-dependent from anode to cathode. The immobilization of MOF-5 improved the interactions between analytes and layer on inner wall of the capillary. Excellent separations of substituted benzenes and acidic and basic analytes were obtained on the fabricated capillary columns. The MOF-5-modified capillary columns exhibited good repeatability, with relative standard deviations for intra-day, inter-day runs and column-to-column less than 1.87%, 3.53%, and 8.49%, respectively. Our successful application of MOF-5 paved the way for introducing series of dicarboxylate-based isoreticular MOFs to OT-CEC as novel stationary phase.
✓ 已验证
产品关联
DOI
PubMed
高影响因子
JOURNAL OF SEPARATION SCIENCE
·
2016
·Vol. 40
·期 4
·954-961
·
IF 2.741
Yilin Li,Tao Bao,Zilin Chen
In this work, we developed a capillary column modified with zeolitic imidazolate framework-8 as a novel stationary phase for open-tubular capillary electrochromatography. To immobilize zeolitic imidazolate framework-8 onto the inner surface of silica capillary, a bio-inspired polydopamine functionalization was used to functionalize the capillary surface with polydopamine. First, a polydopamine layer was assembled inside the capillary. Second, due to noncovalent adsorption and covalent reaction ability, polydopamine could attract and anchor zeolitic imidazolate framework-8 onto the inner surface of capillary. It has been demonstrated that zeolitic imidazolate framework-8 was successfully grafted on the inner wall of the capillary by scanning electron microscopy, and Fourier transform infrared spectroscopy. The electro-osmotic flow characteristics of capillaries were also investigated by varying the pH value and acetonitrile content of mobile phase. The zeolitic imidazolate framework-8 coating not only increased the phase ratio of open-tubular column, but also improved the interactions between tested analytes and the stationary phase. Three groups of isomers including acidic, basic, and neutral compounds were well separated on the zeolitic imidazolate framework-8 bonded column, with theoretic plate numbers up to 1.9 × 10 5 N for catechol. The repeatability of the prepared columns was also studied, and the relative standard deviations for intra- and interday runs were less than 5%.
✓ 已验证
产品关联
DOI
PubMed
高影响因子
JOURNAL OF CHEMICAL TECHNOLOGY AND BIOTECHNOLOGY
·
2017
·Vol. 93
·期 5
·1347-1358
·
IF 3.135
Yu Shen,Fumin Wang,Zongzhuang Han,Xubin Zhang
BACKGROUND ZSM-5 zeolites are of great importance in industrial catalysis. However, the diffusion limitations caused by small pore opening restrict the extent of catalytic conversions over conventional ZSM-5. Many studies have shown that mass transfer in zeolite channels can be improved by controlling the morphology or creating additional mesoporosity. Here, the catalytic performance is further improved by the creation of hollow structure and intracrystalline mesopores in ZSM-5 zeolite. RESULTS The characterization results demonstrated that hollow ZSM-5 with intracrystalline mesopores can be synthesized by using a simple one-step hydrothermal strategy with a commercial gemini-type cationic surfactant containing hydrophilic hydroxyl groups. Compared with the Fe-substituted conventional ZSM-5, the Fe-substituted hollow ZSM-5 with intracrystalline mesopores show remarkably enhanced catalytic performance in the hydroxylation of phenol. About 52.2% conversion of phenol can be obtained with almost 96.8% selectivity to dihydroxybenzenes. The catalytic activity remained almost unchanged after five cycles. CONCLUSION The newly created hollow structure and intracrystalline mesopores in ZSM-5 zeolite showed enhanced catalytic activity and reusability for the hydroxylation of phenol, which is higher than most reported systems. The prepared catalyst is a promising alternative material for the hydroxylation of phenol. © 2017 Society of Chemical Industry
✓ 已验证
产品关联
DOI
高影响因子
ChemCatChem
·
2017
·Vol. 10
·期 4
·825-830
·
IF 4.803
Jun Ma,Nan Wu,Shi-an Sun,Ting Yao,Gong-yi Li,Tian-jiao Hu,Yi-he Li,Xiao-dong Li
Graphical Stack it up ! Vertically aligned N-doped graphene rooted on SiC microspheres (NG on SiC) is prepared by precursor pyrolysis by using a lab-made continuous preparation system. The use of acetonitrile as a raw material promotes the lateral dimensions and improves the graphitization degree of NG on SiC significantly. The metal-free carbocatalyst NG on SiC is an effective and selective oxidation catalyst towards targeted C−H bond activation of ethylbenzene. Vertically aligned N-doped graphene rooted on SiC microspheres (NG on SiC) is prepared by precursor pyrolysis. One of the raw materials, acetonitrile, has three important effects that could facilitate the N-doping process effectively, promote the lateral dimensions and improve the graphitization degree of NG on SiC significantly. The metal-free carbocatalyst NG on SiC is an effective and selective oxidation catalyst towards targeted C−H bond activation of ethylbenzene. The unique nanostructure of NG on SiC is composed of predispersed graphene, which is expected to avoid harmful agglomeration during preparation, storage, transportation, and applications.
✓ 已验证
产品关联
DOI
高影响因子
BIORESOURCE TECHNOLOGY
·
2016
·
IF 4.917
Yimeng Wang,Jie Wang
The pinewood was pyrolyzed in the first reactor at a heating rate of 10 °C min −1 from room temperature to 700 °C, and the vapor was allowed to be cracked through the second reactor in a temperature range of 450–750 °C without and with HZSM-5. Attempts were made to determine a wide spectrum of gaseous and liquid products, as well as the mass and element partitions to gas, water, bio-oil, coke and char. HZSM-5 showed a preferential deoxygenation effect via the facilitated decarbonylation and decarboxylation with the inhibited dehydration at 550–600 °C. This catalyst also displayed a high selectivity for the formations of aromatic hydrocarbons and olefins by the promoted hydrogen transfer to these products at 550–600 °C. The bio-oil produced with HZSM-5 at 500–600 °C had the yields of 14.5–16.8%, the high heat values of 39.1–42.4 MJ kg −1 , and the energy recoveries of 33–35% (all dry biomass basis).
✓ 已验证
产品关联
DOI
PubMed
高影响因子
FUEL PROCESSING TECHNOLOGY
·
2016
·
IF 3.847
Guodian Zhu,Xinping Ouyang,Linfeng Jiang,Yuan Zhu,Dongxue Jin,Yuxia Pang,Xueqing Qiu
Lignin is a future feedstock for the production of low molecular weight aromatics, and hydrogenolysis is probably the most promising process for lignin depolymerization . Effect of the benzylic alcohol group, aromatic methoxyl and phenolic hydroxyl groups on the hydrogenolysis of β -O-4 bonds in lignin model compounds was investigated in Pd/C hydrogenolysis system. It was found that the β -O-4 bonds in compounds with no a benzylic alcohol group were cleaved directly and quickly to form two aromatic monomers in near-quantitative yield. However, both dehydrogenation and dehydroxylation occurred for the model compounds containing a benzylic alcohol group, and resulted in more complicated products distribution. The dehydrogenation of a benzylic alcohol group hindered the cleavage of β -O-4 bonds to form aromatic monomer products. The results also indicated that both the aromatic methoxyl and phenolic hydroxyl groups had no impact on products distribution. The aromatic methoxyl group in non-phenolic and phenolic compounds promoted the cleavage of β -O-4 bonds, while the phenolic hydroxyl group had a slightly negative impact on cleavage of β -O-4 bonds.
✓ 已验证
产品关联
DOI
高影响因子
PETROLEUM CHEMISTRY
·
2017
·Vol. 57
·期 3
·209-214
·
IF 0.493
Liu G. L.,Wang Y. D.,Zhang R.,Liu H. Y.,Liu Z. C.,Meng X. H.
The catalytic cracking performance of light hydrocarbon model compounds (1-hexene, n -octane, i -octane, ethylcyclohexane and ethylbenzene) over a mesoporous catalyst based on ZSM-5 zeolite was analyzed and compared using a microscale apparatus with a fixed-bed reactor. The effects of reaction temperature and weight hourly space velocity (WHSV) on feed conversion and the yields of ethene and propene were investigated. The results showed that with increased reaction temperature, the conversion of model compounds increased monotonically, and that of 1-hexene was close to 100% above 660°C; the yield of ethene plus propene of n -octane, i -octane and ethylcyclohexane increased continuously, while that of 1-hexene and ethylbenzene passed through maximum. With increased WHSV, the yield of ethene plus propene of ethylbenzene increased continuously, and that of the other model compounds decreased continuously. Through comprehensive analysis of the data, it is indicated that 1-hexene exhibited the highest cracking performance, followed by n -octane and ethylcyclohexane, whereas i -octane and ethylbenzene exhibited the lowest.
✓ 已验证
产品关联
DOI
高影响因子
Polymer Chemistry
·
2016
·Vol. 7
·期 47
·7216-7222
·
IF 5.687
Yan Li,Cheng Chen,Jinlong Wu,Xiangxiang Jia,Yufan Lu,Fangjuan Chen,Lijian Liu
Copolymerization between alkyl diazoacetates and α,β-unsaturated aldehydes, which is a one-pot, one-step and catalyst-free reaction, is presented. The product is a ternary copolymer composed of an alkyl diazoacetate, an α,β-unsaturated aldehyde and an α-carbalkoxy carbene, which is derived from the alkyl diazoacetate by the release of N2. Thus, the reaction is named as the C1N2/C2/C1 copolymerization. Various diazoacetates and α,β-unsaturated aldehydes were utilized to establish the methodology. The products are down-/up-conversion fluorescence molecules that can significantly enhance cell imaging through the synchronized excitation of near-ultraviolet and near-infrared light and may be widely used in other optical fields. The up-conversion fluorescence is the result of a two-photon excitation process.
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF SEPARATION SCIENCE
·
2017
·Vol. 40
·期 23
·4521-4529
·
IF 2.557
Haixia Lyu,Heqing Zhao,Wenfei Qin,Zenghong Xie
A simple “one-pot” approach for the preparation of a new vinyl-functionalized organic–inorganic hybrid monolithic column is described. In this improved method, the hydrolyzed alkoxysilanes of tetramethoxysilane and triethoxyvinylsilane were used as precursors for the synthesis of a silica-based monolith, while 1-hexadecene and sodium ethylenesulfonate were used as vinyl functional monomers along with azobisisobutyronitrile as an initiator. The effects of reaction temperature, urea content, and composition of organic monomers on the column properties (e.g. morphology, mechanical stability, and chromatographic performance) were investigated. The monolithic column was used for the separation of neutral solutes by reversed-phase pressurized capillary. Furthermore, the monolith can separate various aromatic amines, which indicated its excellent cation-exchange capability and hydrophobic interactions. The baseline separation of the aromatic amines was obtained with a column efficiency of up to 78 000 plates/m.
✓ 已验证
产品关联
DOI
PubMed
高影响因子
危险品化学品经营许可证（带存储）