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Dai Y.-Q.,Beijing University of Chemical Technology | Zhang L.,Northwest Research Institute of Chemical Industry | Jin R.-G.,Beijing University of Chemical Technology
Asian Journal of Chemistry | Year: 2013

Through the study of three grades of low polymerization degree poly(vinyl chloride) resins, the molecular weight distribution of low polymerization degree PVC resins was influenced by the particle size. The number of sub micro particles in low polymerization degree poly(vinyl chloride) resin is related to the molecular weight distribution. The higher the number of sub micro particles are, the higher the molecular weight and molecular weight distribution. It is presented a detailed study on the relationship of the molecular weight distribution and inner morphology. Source


Zhang L.,Beijing University of Chemical Technology | Zhang L.,Northwest Research Institute of Chemical Industry | Liu Z.,Research Institute of Shaanxi Yanchang Petroleum Group | Dai Y.,Beijing University of Chemical Technology | Jin R.,Beijing University of Chemical Technology
Asian Journal of Chemistry | Year: 2013

Thermal degradation of both high molecular polyacrylonitrile precursor fiber and pre-oxidation fibers with different extent of stabilization were studied in N2 atmospheres using thermogravimetric analysis coupled with Fourier transform Infrared analysis (TG-FTIR). Degradation mechanism and volatile products at various temperatures of each sample were studied. The results show that the fibers with higher stabilization were more stable. It is indicated that degradation process of fibers can be divided into three stages and most of the weight loss occurs at the second stage. The gaseous products such as H2O, NH3., HCN, CO and CO2 are formed, meanwhile, the amount of volatile products of fibers were closely related to stabilization of fibers. Source


Zhang L.,Beijing University of Chemical Technology | Zhang L.,Northwest Research Institute of Chemical Industry | Liu Z.,Research institute of YangChang Petroleum Group Co. | Dai Y.,Beijing University of Chemical Technology | Li Q.,Beijing University of Chemical Technology
Asian Journal of Chemistry | Year: 2013

Isotactic polyacrylonitrile with triad isotacticity of 0.53 was successfully synthesized by using dialkylmagnesium as initiator. The effects of oxygen concentrating on chemical evolutions and thermal properties of iso-polyacrylonitrile were studied by Fourier transform infrared spectroscopy and thermal gravimetric analysis at different concentration (0, 20, 50 and 80 vol. %). Activation energy of thermal stabilization was obtained under non-isothermal conditions by using iso-conversional methods. The results showed that the amount of un-cyclized nitrile groups increased with oxygen concentration. This indicated that the cyclization was affected by oxygen concentration. Two stages and a large residue mass of iso-polyacrylonitrile pyrolysis during oxidation were detected in the oxygen-containing atmosphere. The activation energies were calculated by Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) iso-conversional method under different oxygen concentration varying from 0 to 80 %. Source


Yin X.,Hainan University | Yu C.,Hainan University | Zhang X.,Northwest Research Institute of Chemical Industry | Yang J.,Hainan University | And 3 more authors.
Polymer Bulletin | Year: 2011

Bacterial cellulose (BC) was homogenously modified with succinic anhydride in N,N-dimethylacetamide/LiCl in the presence of triethylamine and heterogeneously in pyridine in the presence of 4-dimethylaminopyridine. FTIR, XRD, 13C CP MAS NMR, SEM were used to characterize BC and succinylated bacterial cellulose (SBC). For homogeneous modification, the degree of substitution (DS) of SBC differs from 0.21 to 1.45 with the variation of the adding amount of succinic anhydrate, temperature, reaction time, and the amount of triethylamine. DS and XRD profiles reveal that heterogenous reaction mainly happens on the surface of BC membrane. The adsorption capacity and mechanism of Cu2+ onto BC and SBC were investigated. The result shows the adsorption is affected by the morphology and the DS of adsorbents. © 2010 Springer-Verlag. Source


Li X.,Xian Jiaotong University | Yang B.,Xian Jiaotong University | Zhang Y.,Northwest Research Institute of Chemical Industry
Journal of Process Control | Year: 2013

Both nonlinear and linear dynamic characteristics of the low temperature methanation reactor with recycle loop are analyzed for the process safe operation and effective control. Aspen Dynamics tool is adopted to get transient behaviors of the reactor under step changes of the inlet temperature and CO mole fraction. A double-input-multi-output linearized system based on the nonlinear dynamic model is developed for further insight into the process stability, response rapidity and controllability. Similar responses are obtained in the nonlinear and linear models for commendable mutual authenticating. The presence of material recycle because of the unconverted reactants, together with the thermal recycle for energy saving, renders a more sensitive stability of the system, where thermal feedback has the major effect, but the existing of mass feedback may weaken this effect when considerable heat is recycled. Moreover, the transfer function of the linear model indicates that the integral term is necessary for the reactor variables control, and the proposed control strategy using a High Selector module in Aspen Dynamics can successfully maintain the hot spot temperature within the reactor by considering the migration of the peak temperature under the two disturbances. © 2013 Elsevier Ltd. All rights reserved. Source

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