Reaction Kinetics Mechanisms and Catalysis
·
2013
·Vol. 109
·期 2
·551-562
·
IF 1.104
Cui Wenjing,Zhu Huaiyong,Jia Meilin,Ao Wulan,Zhang Yulin,Zhaorigetu Bao
Imines were synthesized from benzyl alcohol and amines by using catalysts of gold nanoparticles supported on ZrO 2 (Au/ZrO 2 ). The effects of reaction time, temperature, gold loadings and base were investigated. High yields were achieved under moderate conditions (60 °C) in the presence of KOCH 3 . For instance, the yield of N -benzylidenebenzylamine produced from benzyl alcohol and benzylamine on 3 wt% Au/ZrO 2 is 87 %. The synthesis of imine involves two reaction steps: selective oxidation of benzyl alcohol to benzaldehyde and the coupling reaction of amines with benzaldehyde. In the first step, the base promotes the selective oxidation. The reactions of benzyl alcohol with three different amines, aniline, n -butylamine and benzylamine, were conducted to produce corresponding imines. The results show that the amine with stronger nucleophilicity has better ability to react with benzaldehyde in the second step, resulting in higher yield of the corresponding imine. We proposed a tentative mechanism for the synthesis process.
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Scientific Reports
·
2015
·Vol. 5
·期 1
·1-7
·
IF 5.578
Liao Peng,Al-Ani Yasir,Malik Ismael Zainab,Wu Xiaohui
A recently developed Pd-based electro-Fenton (E-Fenton) process enables efficient in situ remediation of organic contaminants in groundwater. In the process, H 2 O 2 , Fe(II) and acidic conditions (~pH 3) are produced in situ to facilitate the decontamination, but the role of ubiquitous natural organic matters (NOM) remain unclear. This study investigated the effect of Aldrich humic acid (HA) on the transformation of toluene by the Pd-based E-Fenton process. At pH 3 with 50 mA current, the presence of HA promoted the efficiency of toluene transformation, with pseudo-first-order rate constants increase from 0.01 to 0.016 as the HA concentration increases from 0 to 20 mg/L. The HA-enhanced toluene transformation was attributed to the accelerated thermal reduction of Fe(III) to Fe(II), which led to production of more hydroxyl radicals. The correlation of the rate constants of toluene transformation and HA decomposition validated hydroxyl radical (·OH) as the predominant reactive species for HA decomposition. The finding of this study highlighted that application of the novel Pd-based E-Fenton process in groundwater remediation may not be concerned by the fouling from humic substances.
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POLYMER
·
2015
·
IF 3.562
Yingying Ren,Zhiyong Wei,Xuefei Leng,Yurong Wang,Yang Li
Boric acid ( 1 , B(OH) 3 ) was investigated as metal-free biocatalyst for its activity towards the bulk ring-opening polymerization (ROP) of ε -caprolactone (CL) initiated by benzyl alcohol (BnOH). Moreover, other boric acid derivates such as phenylboronic acid ( 2 ), 2-thienylboronic acid ( 3 ), 2-furanylboronic acid ( 4 ) and 5-pyrimidinylboronic acid ( 5 ) were also used as acidic catalysts to synthesize poly( ε -caprolactone) (PCL), poly( δ -valerolactone) (PVL) and poly(trimethylene carbonate) (PTMC). The studies on the polymerization kinetics for all catalysts confirm that the reaction rates are first-order with respect to monomer and their catalytic activities follow the order 1 > 3 > 2 ≈ 4 > 5 . Furthermore, the block copolymerization of ε -caprolactone (CL) with δ -valerolactone (VL) and trimethylene carbonate (TMC) successfully proceeded by the sequential monomer addition to give PCL- b -PVL and PTMC- b -PCL copolymers , indicating the living nature of the present polymerization system. The end group analysis by 1 H NMR and MALDI-TOF MS measurements suggested that the benzyl moiety of initiator inserted into the synthesized polymeric chain. The existence of the interaction between the catalyst B(OH) 3 and the monomer CL supports that B(OH) 3 catalyzed ROP of CL preferred an activated monomer mechanism. A possible model for the initiation and propagation procedures of ROP of cyclic esters catalyzed by boric acid in the presence of benzyl alcohol was proposed.
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JOURNAL OF CHEMICAL THERMODYNAMICS
·
2014
·
IF 2.423
Hui Wang,Qinbo Wang,Zhenhua Xiong,Chuxiong Chen,Binwei Shen
The solubility of benzoic acid in binary (benzyl alcohol + benzaldehyde) solvent mixtures was measured at temperature from (298.35 to 355.65) K and atmospheric pressure. The measured solubility increases with the increasing temperature at constant solvent composition. The effects of mass fraction benzaldehyde in the solvent mixtures at (0.0 to 1.00) on the solubility were studied. The measured solubility decreases with the increasing mass fraction of benzaldehyde. The experimental results were correlated with the non-random two-liquid (NRTL) equations, and good agreement between the correlated and the experimental values was obtained. Thermodynamic functions for the solution of benzoic acid in binary (benzyl alcohol + benzaldehyde) solvent mixtures were calculated with the van’t Hoff plot. The apparent dissolution Gibbs free energy change was also calculated.
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JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY
·
2014
·Vol. 52
·期 19
·2715-2724
·
IF 3.245
Jizhen Zhang,Aihua Li,Huihui Liu,Dongjiang Yang,Jingquan Liu
A recyclable solid-state photoinitiator based on the surface modified niobium hydroxide is prepared and successfully introduces into reversible addition–fragmentation chain transfer (RAFT) polymerization under visible light illumination. It is revealed by gel permeation chromatography analysis that well-defined polymers with controlled molecular weight and narrow polydispersity index can be achieved when the feed ratio of photoinitiator to the RAFT agent was controlled properly. It is also found that the polymerization is highly responsive to external stimulus and when light is removed from the system polymerization stops almost immediately. In addition, the photoinitiator can be recycled and reused to initiate the polymerization for many times without significant decrease of initiation efficiency. At last, the mechanism for the light initiated polymerization is proposed to illuminate how the initiation and chain propagation proceed. This facile, green and visible light initiation methodology could attract more and more applications in polymer science with the depletion of fossil energy. A recyclable solid-state photoinitiator based on the surface modified niobium hydroxide was prepared and successfully introduced into reversible addition–fragmentation chain transfer (RAFT) polymerization under visible light illumination. It is revealed that well-defined polymers with controlled molecular weight and narrow polydispersity index (PDI) can be achieved when the feed ratio of photoinitiator to the RAFT agent was controlled properly. It is also found that the polymerization is highly responsive to light initiation. In addition, the photoinitiator can be recycled and reused to initiate the polymerization for many times without significant decrease of initiation efficiency. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52 , 2715–2724
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FOOD CHEMISTRY
·
2014
·
IF 3.259
Yunzi Feng,Guowan Su,Haifeng Zhao,Yu Cai,Chun Cui,Dongxiao Sun-Waterhouse,Mouming Zhao
Twenty-seven commercial soy sauces produced through three different fermentation processes (high-salt liquid-state fermentation soy sauce, HLFSS; low-salt solid-state fermentation soy sauce, LSFSS; Koikuchi soy sauce, KSS) were examined to identify the aroma compounds and the effect of fermentation process on the flavour of the soy sauce was investigated. Results showed that 129 volatiles were identified, of which 41 aroma-active components were quantified. The types of odorants occurring in the three soy sauce groups were similar, although their intensities significantly differed. Many esters and phenols were found at relatively high intensities in KSS, whereas some volatile acids only occurred in LSFSS. Furthermore, 23 aroma compounds had average OAVs > 1, among which 3-methylbutanal, ethyl acetate, 4-hydroxy-2-ethyl-5-methyl-3(2 H )-furanone, 2-methylbutanal and 3-(methylthio)propanal exhibited the highest average OAVs (>100). In addition, omission tests verified the important contribution of the products resulting from amino acid catabolism to the characteristic aroma of soy sauce.
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RSC Advances
·
2017
·Vol. 7
·期 68
·42819-42825
·
IF 3.108
Yanghe Fu,Huan Yang,Rongfei Du,Gaomei Tu,Chunhui Xu,Fumin Zhang,Maohong Fan,Weidong Zhu
Co-doped NH2-MIL-125(Ti) catalysts [Co/NH2-MIL-125(Ti)] are developed for the photocatalytic reduction of CO2 upon visible-light irradiation. Compared with NH2-MIL-125(Ti), Co/NH2-MIL-125(Ti) exhibits a significantly enhanced activity in CO2 reduction, due to the fact that the doping of Co nanoparticles onto NH2-MIL-125(Ti) can promote the visible-light harvesting and electron transfer. In addition, when benzylic alcohols as electron donors, instead of triethanolamine (TEOA) which is often used as a sacrificial agent, are added into the reaction system, Co/NH2-MIL-125(Ti) can simultaneously catalyze CO2 reduction to formic acid (HCOOH) and the selective oxidation of the benzylic alcohols to the corresponding aldehydes, making the proposed process more economical and environment-friendly.
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RSC Advances
·
2016
·Vol. 6
·期 51
·45791-45801
·
IF 3.289
Yingying Ren,Zhiyong Wei,Tong Wu,Yufei Bian,Xuefei Leng,Cheng Zhou,Yang Li
A large diversity of tailor-made linear-comb and star-comb poly(δ-valerolactone)s (PVL) have been obtained with hydroxylated polybutadiene (HPB) as a macroinitiator and 1,5,7-triazabicyclo-[4.4.0]dec-5-ene (TBD) as a catalyst by a simple “one-step” method. The critical content of this research was to explore systematically the differences in the physicochemistry properties between highly branched PVLs and linear PVLs, including the intrinsic viscosity, rheological properties, and crystallization and melting behavior. Studies of solution behavior and melting behavior elucidated that intrinsic viscosities in solution and complex viscosities in the bulk for comb branched PVLs were much lower compared with their linear and star counterparts. Both WAXD and DSC analysis of PVLs with different topological structures indicated that the comb branched architectures do not alter the structures of the PVL crystallites, but markedly improve the crystallization behavior, e.g. higher crystallinities. Moreover, the influence of the molecular weight of a single arm on the thermal properties and crystallization properties of the obtained linear-comb PVLs was explored. The results demonstrated that the crystallization temperatures (Tcs), melting temperatures (Tms) and crystallinities increased with the increase of molecular weight of a single arm. As such, a structure–property correlation is expected to be constructed which is of great practical importance in the syntheses and applications of highly branched polymers (HBPs).
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JOURNAL OF PHYSICAL CHEMISTRY B
·
2016
·
IF 3.187
Yingying Ren,Zhiyong Wei,Xuefei Leng,Tong Wu,Yufei Bian,Yang Li
Highly branched polymers (HBPs) are a special class of functional polymeric materials and possess unique properties due to their unique topological structure. A new series of highly branched linear–comb and star–comb amorphous poly(trimethylene carbonate)s (PTMC) and crystalline poly(ε-caprolactone)s (PCL) with well-defined structure and high molecular weight were first synthesized using hydroxylated polybutadiene (HPB) as macroinitiators by simple “one-step” and “graft from” strategies. It is expected that the impact of long-chain, highly branched architecture on the properties of amorphous and crystalline polymers, respectively, is different. We explored systematically for the first time the effect and comparison of branched architectures on the physical and chemical properties of highly branched PTMCs and PCLs, including the intrinsic viscosity, glass transition, thermal degradation, creep property, rheological property, and crystallization and melting behaviors. It is found that the intrinsic viscosities in solution for both comb-branched PTMCs and PCLs were much lower compared with their linear and star counterparts arise from more compact structure and smaller hydrodynamic volumes. For amorphous PTMC, the creep strain and rate increased remarkably with degree of branching increasing due to the shorter side chains making it difficult for the highly branched molecules to entangle. For crystalline PCL, both WAXD and DSC analysis of PCLs with different topological structures indicated that the comb branched architectures have no significant influence on the crystal structure of PCL, but greatly promote the crystallization behavior, e.g., higher crystallinities. The deep understanding of structure–property relationship expects to guide the synthesis of designed functional polymer materials and the processing of polymer products.
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POLYMERS FOR ADVANCED TECHNOLOGIES
·
2017
·Vol. 29
·期 1
·384-393
·
IF 1.907
Qing Shang,Aixin Zhang,Zhaoying Wu,Sijin Huang,Ruiqiong Tian
The aim of this study was to fabricate different risperidone (RIS)–loaded poly(lactic-co-glycolic acid) microspheres (PLGA MS) with various viscosity of PLGA polymers and investigate the RIS release profiles. Risperidone-loaded PLGA MS were fabricated via an oil/water–type emulsion solvent evaporation method, using ethyl acetate and benzil alcohol as the dispersed solvents. The PLGA (75:25) with the viscosity of 0.82, 0.93, and 1.10 dL/g was used in the fabrication. The morphology and the degradation of the RIS-PLGA MS were investigated with a scanning electron microscope. The distribution states of RIS in the PLGA MS were studied with differential scanning calorimetry. The residual of ethyl acetate and benzil alcohol in the resulting MS was monitored with gas chromatography. The in vitro release profiles of RIS from PLGA MS were also studied. Scanning electron microscope photographs illustrated that the obtained PLGA MS were monodisperse spheres with an average diameter of 100 μm. Gas chromatography results suggested that no residual ethyl acetate was left in the final RIS-PLGA MS, and the residue amount of benzil alcohol was about 1%. In vitro drug release profiles from the microsphere showed a substantially sigmoidal pattern of negligible initial burst up to 24 hours and minimal release (time lag) for 14 days. After the lag phase, slow release took a place up to 30 days, and then rapid release occurred sharply for about 2 weeks. The RIS release reached equilibrium around day 50. All release profiles showed the similar trend, and no significant difference was observed among these release profiles ( P > .05). This phenomenon indicated that RIS-loaded PLGA MS with the viscosity of 0.82 to 0.93 dL/g showed the optimal release behavior. However, no obvious differences were found among the MS obtained from the viscosity of 0.82 to 1.10 dL/g. These studies provided basis for the quality control in the industrial production of PLGA MS.
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MACROMOLECULAR CHEMISTRY AND PHYSICS
·
2017
·Vol. 218
·期 16
·1700178
·
IF 2.5
Xuefei Leng,Yingying Ren,Zhiyong Wei,Yufei Bian,Yang Li
A series of highly branched star-comb poly(ε-caprolactone)- block -poly( l -lactide) (scPCL- b -PLLA) are successfully achieved using star-shaped hydroxylated polybutadiene as the macroinitiator by a simple “grafting from” strategy. The ration of each segment can be controlled by the feed ratio of comonomers. These star-comb double crystalline copolymers are well-defined and expected to illustrate the influences of the polymer chain topology by comparing with their counterparts in linear-shaped, star-shaped, and linear-comb shape. The crystallization behaviors of PCL- b -PLLA copolymers with different architectures are investigated systematically by means of wide-angle X-ray diffraction, differential scanning calorimetry, and polarized optical microscopy analysis. It is shown that the comb branched architectures promote the crystallization behavior of each constituent significantly. Both crystallinity and melting temperature greatly raise from linear to comb-shaped copolymers. Compared to linear-comb topology, the star-comb shape presents some steric hindrance of the graft points, which decrease the crystallinity of scPCL- b -PLLA. Effects of copolymer composition and chain topology on the crystallization are studied and discussed.
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CHEMISTRY OF MATERIALS
·
2017
·
IF 9.466
Tao Wang,Pengfei Zhang,Yan Sun,Bing Liu,Yunling Liu,Zhen-An Qiao,Qisheng Huo,Sheng Dai
Herein, we report the synthesis of new colloidal polydiaminopyridine (PDAP) nanospheres with uniform particle size tuned from 76 to 331 nm. The polymer colloidal nanospheres and thin films assembled by the nanospheres exhibit amphiphilic or superhydrophilic properties, originated from the different polymer surfactants. In addition, the polymer nanospheres can be easily carbonized into microporous carbon nanospheres with high N content up to 24 wt %, thus enabling a preferred basicity for CO2 adsorption. As-synthesized PDAP show good compatibility that can not only encapsulate typical nanoparticles to form core–shell composite nanospheres but also stabilize noble metal ions to obtain ultrasmall metal nanoparticles (e.g., Pd and Au) during the thermal reduction process by the nitrogen sites from sphere frameworks. The nanocomplex Pd/PDAP-500 shows exceptional activity and high selectivity in the solvent-free oxidation of alcohols with O2.
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