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151.
Yu Mo Lei Zhao Chia-Lung Chen Giin Yu Amy Tan Jing-Yuan Wang 《Journal of Thermal Analysis and Calorimetry》2013,111(1):781-788
Pyrolysis is one important way to treat polystyrene waste and upcycle it into useful materials. A comparative pyrolysis study of virgin polystyrene (VPS) and two types of commonly used polystyrene products, expanded polystyrene (EPS) and polystyrene container (CPS) was carried out. Various values were found in the thermodynamic study and kinetic study of VPS, EPS, and CPS pyrolysis, suggesting distinct thermal degradation characteristics of these materials. The energy barrier order of the pyrolysis processes was EPS, CPS, VPS, showing activation energy of 230, 219, and 145 kJ mol?1, respectively. The order of amount of heat absorbed was EPS, CPS, VPS, with enthalpy of 224, 213, and 139 kJ mol?1, respectively. The reaction favorability order was EPS, CPS, and VPS with Gibbs free energy of 118, 132, and 210 kJ mol?1, respectively. Thermogravimetric analysis indicated the use of high heating rate would increase the reaction rate and shorten the reaction time. Product evolution profiles showed that VPS and CPS pyrolysis produced mainly aromatics, while EPS pyrolysis produced aromatics at the initial phase of the reaction and aliphatic hydrocarbon at the latter phase. The diverse pyrolysis behaviors of VPS, EPS, and CPS demonstrated that an examination on different polystyrene materials was desired to optimize the pyrolysis conditions and product distribution, and thus benefit the process of valuable materials recovery. 相似文献
152.
Xiantong Guan Bing Ding Xiaofeng Liu Jiajia Zhu Changhuan Mi Xiaogang Zhang 《Journal of Solid State Electrochemistry》2013,17(7):2087-2093
Li-rich layered Li1.2Ni0.2Mn0.6O2 has been surface modified by nickel–manganese composite oxide (Ni0.5Mn1.5O x ) to serve as a novel cathode material with novel layered spinel structure for lithium-ion battery. The as-prepared Li1.2Ni0.2Mn0.6O2 before and after surface modification by Ni0.5Mn1.5O x as well as simply blended Li1.2Ni0.2Mn0.6O2 with spinel LiNi0.5Mn1.5O4, have been characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electronic microscopy, and differential scanning calorimetry. Electrochemical studies indicate that the Ni0.5Mn1.5O x surface modified Li1.2Ni0.2Mn0.6O2 with peculiar layered spinel character dramatically represented increased discharge capacity, improved cycling stability as well as excellent rate capability at high-voltage even up to 5.0 V. 相似文献
153.
Xiaofeng Niu Weifeng Li Hongbo Xu Xia Liu Lin Qi 《Journal of separation science》2013,36(13):2090-2095
Isoquinoline alkaloids are the primary active ingredients of Corydalis, but an analytical method for quality assessment of the active ingredients in Corydalis impatiens (Pall). Fisch has not been reported. A new, simple, and multiple‐component quantification method was developed for the simultaneous quantification of 11 isoquinoline alkaloids including capnoidine, chelianthifoline, bicuculline, protopine, isoapocavidine, apocavidine, cavidine, tetrahydroepiberberine, ochotensimine, tetrahydrocoptisine, and tetrahydrocorysamine in C. impatiens. Separation of the isoquinoline alkaloids was performed on a RP C18 column (150 × 4.6 mm, 5 μm) with potassium dihydrogen phosphate buffer (pH 2.5, adjusted by phosphoric acid)/acetonitrile (53:47, v/v) containing 0.3% sodium dodecyl sulfonate. The flow rate and detection wavelength were set at 1 mL/min and 295 nm, respectively. Full validation of the assay was carried out including linearity, precision, accuracy, stability, LOD, and limit of quantitation. All calibration curves showed a good linear relationship (r > 0.999) in test range. The results demonstrated that the developed method was reliable, rapid, and specific. Six batches of C. impatiens samples from different sources were determined using the established method. The contents of alkaloids ranged from 11.68 to 351.83 μg/g. This method can be applied for quality evaluation and control of C. impatiens. Eleven isoquinoline alkaloids were first reported on simultaneous determination with HPLC. 相似文献
154.
1-Alkynylphosphonates 3 are prepared in a one-pot procedure from diethyl phosphorochloridates 2 and alkynyllithiums 1, which are readily generated by the reaction of 1-alkynes with n-BuLi. 相似文献
155.
A series of self-healable polyurethane (SHPU)/modified graphene (MG) nanocomposites were synthesized from poly(tetramethylene glycol) (PTMG) and 4,4′-methylene diphenyl diisocyanate (MDI) with minute amounts (0–1 wt%) of MG which was chemically modified graphene oxide (GO) with phenyl isocyanate and reduced in the presence of phenylhydrazine. 相似文献
156.
Xiaofeng Wang Weiyi Xing Gang Tang Ningning Hong Weizhao Hu Jing Zhan Lei Song Wei Yang Yuan Hu 《Polymer Degradation and Stability》2013
A novel sulfur-bearing secondary antioxidant with a high molecular weight of 2252 (OS-POSS), successfully synthesized via photoinitiated thiol-ene click reaction, was compared with two commercial sulfur-bearing secondary antioxidants on the stabilization of polypropylene (PP). The results of their oxidation induction time (OIT) via differential scanning calorimeter measurement (DSC) showed that the higher the molecular weight of secondary antioxidant is, the longer the OIT value, whether such sulfur-bearing antioxidant is used singly or in combination with primary antioxidant. The study of their long-term accelerated thermal aging in the air oven at 150 °C displayed that the molecular structure of sulfur-bearing secondary antioxidant, besides molecular weight, is another highly important factor determining the antioxidant efficiency, i.e., physical loss of antioxidants with the relatively low molecular weight may determine antioxidant efficiency, whereas thioether groups having neighboring ester carbonyl moieties may decompose more hydroperoxides with quicker rate. 相似文献
157.
Abstract The phase diagram of a two component system composed of two smectic compounds: 4-octyloxy-4′-cyanobiphenyl (8OCB) and 4-isothiocyanatophenyl 4-butylbenzoate (4TPB) was investigated. Three Miesowicz viscosity coefficients η1, η2, η3 and the refractive indices at different temperatures as well as the enthalpies of the phase transitions were measured. It was stated, that the properties of the induced nematic phase, for example, the nematic phase existing between two smectic regions, are the same as the ones observed in the case of low viscosity nematic mesogens. 相似文献
158.
Wangdong Zeng Dr. Masatoshi Ishida Sangsu Lee Young Mo Sung Dr. Zebing Zeng Yong Ni Prof. Chunyan Chi Prof. Dongho Kim Prof. Jishan Wu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(49):16814-16824
A p‐quinodimethane (p‐QDM)‐bridged porphyrin dimer 1 has been prepared for the first time. An unexpected Michael addition reaction took place when we attempted to synthesize compound 1 by reaction of the cross‐conjugated keto‐linked porphyrin dimers 8 a and 8 b with alkynyl/aryl Grignard reagents. Alternatively, compound 1 could be successfully prepared by intramolecular Friedel–Crafts alkylation of the diol‐linked porphyrin dimer 14 with concomitant oxidation in air. Compound 1 shows intense one‐photon absorption (OPA, λmax=955 nm, ε=45400 M ?1 cm?1) and a large two‐photon absorption (TPA) cross‐section (σ(2)max=2080 GM at 1800 nm) in the near‐infrared (NIR) region due to its extended π‐conjugation and quinoidal character. It also exhibits a short singlet excited‐state lifetime of 25 ps. The cyclic voltammogram of 1 displays multiple redox waves with a small electrochemical energy gap of 0.86 eV. The ground‐state geometry, electronic structure, and optical properties of 1 have been further studied by density functional theory (DFT) calculations and compared with those of the keto‐linked dimer 8 b . This research has revealed that incorporation of a p‐QDM unit into the porphyrin framework had a significant impact on its optical and electronic properties, leading to a novel NIR OPA and TPA chromophore. 相似文献
159.
160.
Changwei Wang Dr. Zhenhua Chen Prof. Dr. Wei Wu Prof. Dr. Yirong Mo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(4):1436-1444
The generalized anomeric effect refers to the conformational preference of a gauche structure over an anti structure for molecules with a R‐X‐C‐Y moiety. Whereas there are conflicting reports regarding the origin of this ubiquitous effect, a general consensus is that both the steric (more specifically electrostatic) and hyperconjugative interactions contribute. Here we employed the block‐localized wavefunction (BLW) method, which is the simplest variant of ab initio valence bond (VB) theory and can define reference electron‐localized states self‐consistently, to evaluate the magnitude of the hyperconjugation effect in a number of acyclic molecules exhibiting the generalized anomeric effect. The BLW‐based energy decomposition analysis revealed that both the steric and hyperconjugation effects contribute to the conformational preferences of methoxymethyl fluoride and methoxymethyl chlorides. But for the other systems under investigation, including methanediol, methanediamine, aminomethanol and dimethoxymethane, the hyperconjugative interactions play a negative role in the conformational preferences and the steric effect is solely responsible for the generalized anomeric effect. 相似文献