Radiation-induced polymerization of ethylene in a pilot plant. I. Bulk process

Radiation-induced bulk polymerization of ethylene was carried out with use of a pilot plant with a 10 liter reactor at pressures of 225–400 kg/cm², temperatures of 30–95°C, ethylene feed rates of 5–28 kg/hr, and dose rate of 3.8 × 10⁵ rad/hr. Characteristics of the process are mild polymerization conditions and capability of producing medium density polyethylene in powder form. The spacetime yield and molecular weight of polymer were in the range of 3.5 to 13.1 g/liter hr and 2.2 × 10⁴ to 14 × 10⁴, respectively. The space-time yield increased with mean residence time and 2.4 powders of pressure, and decreased with temperature. Molecular weight changed similarly with the reaction conditions. These results were consistent with those of the bench plant experiment and the scale effect was small. Polymer deposit to the reactor wall limited a period of continuous operation of the plant. The amount of deposited polymer was increased with the square of reaction time. The rate of polymer deposit was proportional to polymer concentration and to the cube of pressure. The polymer deposit cannot be solved in the bulk process.     

Radiation-induced polymerization of ethylene in a pilot plant. II. Development of wet-wall process

Radiation-induced polymerization of ethylene using tert-butyl alcohol aqueous solution as a medium was carried out in a pilot plant with 10 liter reactor at pressures of 100 to 400 kg/cm², ethylene feed rates of 1.2 to 11.8 kg/hr, medium feed rates of 0 to 100 liter/hr, dose rates of 0.6 × 10⁵ to 1.4 × 10⁵ rad/hr, and at room temperature. The space-time yield and molecular weight of polymer were in the range of 1.2 to 16.7 g/liter hr and 6 × 10³ to 2 × 10⁵, respectively. The space-time yield and molecular weight increased with pressure and mean residence time. The space-time yield was the maximum at an ethylene molar fraction of 0.5. The produced polymer was continuously taken out from the high-pressure system as a slurry. The amount of deposited polymer to the reactor wall was markedly decreased, and five full days continuous operation was successfully performed with the space-time yield of 13.5 g/liter hr.     

Radiation-induced polymerization of ethylene in pilot plant. IV. Kinetic analysis

The kinetics of the radiation-induced polymerization of ethylene in a flow system using tert-butyl alcohol aqueous solution as a medium were studied. The polymerization was carried out in a large-scale pilot plant with a 50-liter central source-type reactor at various mean residence times and does rates under constant pressure of 300 kg/cm², temperature of 30°C, and ethylene molar fraction of ca. 0.4. The reaction mixture in the reactor was back-mixed flow from the residual polymer concentration in the reactor. The results of the polymerization were analyzed by kinetic treatment based on a reaction mechanism with both first-and second-order terminations for the propagating radical. The apparent rate constants, except for that of second-order termination (k_t2), were consistent with those determined by small-scale batch experiments. The k_t2 is 20 to 40 times larger than that in the batch experiments. The k_t2 increases with decrease in mean residence time and with agitation, probably because of mobility of the propagating radical.     

Radiation-induced polymerization of ethylene in pilot plant. V. Molecular weight distribution of polyethylene

The molecular weight distribution of the polyethylene produced by radiation in a large-scale pilot plant at pressures of 105–395 kg/cm² and temperatures of 30–80°C was determined by gel permeation chromatography and discussed in connection with the polymerization conditions. The bimodal molecular weight distribution was observed in most of polymers. The number-average molecular weight at two peaks are 10⁴, and 10⁵, respectively. The fraction of the peak at higher molecular weight increased with pressure and mean residence time, and with decreasing dose rate and temperature. The distribution was unimodal in the early stage of the operation and became bimodal, remaining unchanged in the later stage. The distribution also changed from bimodal to unimodal with rising temperature. These results were consistent with those in static batch experiments and well explained by the polymerization scheme assuming two physical states to be different in polymer mobility.     

Radiation-induced emulsion polymerization of vinyl acetate in a pilot plant reactor I. Recycle flow reactor

A number of successful radiation polymerization of vinyl acetate in emulsion have been carried out in a modular stainless steel flow pilot plant. In a recycle mode, the system was utilized for extremely accurate kinetic measurements and experimental verification of model restrictions such as plug flow, lack of post irradiation effects and differential reactor behavior. Experimental conditions were explored to minimize contaminant, primarily oxygen, inhibition, and the tendency for this formulation, essentially an adhesive, to build up on the reactor walls. Industrial scaleup of such a prototype system appears attractive.     

新乙烯回收技术扩大中试装置工艺路线

介绍了中试装置的布置、工艺路线及特点，并简要总结了工程建设过程中的经验。     

Radiation-induced emulsion ploymerization of vinyl acetate in a pilot plant reactor II. Kinetics

The recycle flow reactor pilot plant, described in Part I of this series, has been used to study some kinetic and other features of the emulsion polymerization of vinyl acetate. In particular, the dependence of the rate on the emulsifier concentration was determined and found to be 0.38 ± 0.09. Separate batch experiments were in reasonable agreement as 0.29 ± 0.10. The effects of temperature, dose rate, and agitation rate were also determined and were in agreement with most of the literature values.     

乙烯工艺阻聚剂在选择与使用过程中应注意的问题

阐述了乙烯工艺阻聚剂的选择与使用和乙烯装置长周期稳定运转的关系，从10个方面对乙烯工艺阻聚剂在选择与使用过程中应注意的问题进行了讨论。     

Catalyst fragmentation during propylene polymerization. III: Bulk polymerization process simulation

Fragmentation of support/catalyst particles during propylene bulk polymerization is analyzed by means of a mathematical model including energy and mass balances, with chemical reaction. The rupture phenomenon is specifically considered by the model and analyzed as it proceeds along time. Model predictions concerning the effects of fragmentation on polymerization are discussed. The influence of mass-transfer resistances at the macroparticle and microparticle level, as well as the microparticle nucleus-size effects over the polymerization process, are analyzed. Macroparticle mass-transfer resistance affects both the rate of fragmentation and temperature excursions. Microparticle nucleus-size exerts a strong influence over the whole polymerization process. A small micronucleus-size produces both a delay in the fragmentation process and a greater value of she final catalyst yield. The effects of major critical parameters are evaluated via model simulation, and the results are discussed. The analysis shows that fragmentation depends on the combined effect of the parameters studied. Modeling of the process considering all parameters simultaneously is the proper way of predicting the fragmentation sequence for a given support/catalyst particle. Crystallinity of the produced polymer affects the rate of fragmentation, either increasing or decreasing the rupture rate depending on macroparticle porosity and compactness. Heat transfer conditions in the liquid-phase system make the temperature runaway problem easy to predict and control, in spite of high polymer yields. The design of “tailor-made” support/catalyst macroparticles in accordance with catalytic activity is necessary in order to obtain high yields and controlled process temperatures.     

Radiation-induced polymerization. I. A pyrotechnic binder

In the past, binder systems had to be limited to systems where the catalytically initiated polymerization exotherm was low. With radiation-initiated polymerization, this is not a problem, and the number of monomers which can now be investigated is unlimited. Based upon the styrene–benzoyl peroxide system, addition of peroxide sensitizers significantly decrease the radiation dose required for 100% conversion.     

Emulsion polymerization of ethylene. III. Factors affecting the stability of polyethylene latexes

A semiquantitative method for assessing the amount of visible solid matter in polyethylene latexes is described. As judged by this method and by the presence of particles larger than 50 μ, the stability of the latexes was related to (1) the type and concentration of post-emulsifier added to the latex, (2) the average size of the polymer particles, and (3) the concentration of solids. Generally, the appearance was better when the latexes had a low (30%) concentration of solids, a large (800 A.) average particle diameter, and enough post-emulsifier to cover most of the polymer surface. Specific samples, however, having a high (36%) concentration of solids and a small (300 A.) average particle diameter also showed good storage stability. According to tests on selected latexes, good resistance to coagulation by mechanical shear was obtained only if the surface of the polymer was completely covered with emulsifier. When polyethoxylated alkylphenols were used as post-emulsifiers, an inverse relation appeared to exist between latex stability and average number of ethylene oxide units per emulsifier molecule. Moreover, the addition of each ethylene oxide group increased the apparent area of the emulsifier molecule by about 4 A.²     

乙烯装置节油流程的开发

根据石油烃类裂解反应机理并分析乙烯联合装置工艺流程,找出乙烯联合装置生产成本和综合能耗最主要的影响因素--裂解原料.考虑将乙烯联合装置副产的丙烷、抽余碳四、碳五馏分、芳烃抽余油等替代.石脑油原料直接或加工处理后返回裂解炉生产乙烯,由此开发出乙烯节油流程.对于公称能力1.000 Mt/a乙烯联合装置来说,石脑油裂解原料消耗由常规流程3.317Mt/a减少到节油流程2.918Mt/a约12.03%左右;经济分析中的开始盈余年份由常规流程8.33年提前到节油流程6.14年约26.29%以上.     

PET recycling: Evaluation of the solid state polymerization process

Many studies have been carried out to make bottle‐to‐bottle recycling feasible. One of the difficulties found is the decrease in the polymer's molar mass, which damages the injection blow molding process. A method usually employed to increase the molar mass of virgin PET consists of solid‐state polymerization (SSP). In this work, we studied the SSP process applied to post‐consumer recycled PET by analyzing the inherent viscosity and amount of carboxylic end groups, and the results of dynamic flow rheometry. Although the results show that the recycling process decreases polymer molar mass, and this indicates degradative processes, SSP was successful in increasing molar mass in post‐consumer recycled PET. This made feasible bottle‐to‐bottle recycling. In addition, the parallel plate rheometry technique was powerful in assessing the degradative process and, therefore, that the SSP process was successful. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

气相法聚乙烯工艺技术进展

介绍了国内外气相聚乙烯装置及工艺概况、气相工艺技术进展,并对我国气相聚乙烯的发展提出了建议.     

Polymerization of ethylene induced by fractured metallic oxides. III. Factors affecting the polymerization

Mechanochemical polymerization of ethylene was found to be induced by fracture of γ-alumina under quite low pressure and room temperature. The factors to control the polymerization yield, for example, calcination temperature of the alumina, spin concentration after ball milling, milling time, and changes of acidity before and after the fracture, were investigated in order to know the polymerization mechanism. It was found that the polymerization yield did correlate not with the spin concentration responsible to paramagnetic species produced by the fracture, but the calcination temperature of the γ-alumina and the milling time. The resultant polymeric material on the fractured alumina was extracted alumina was extracted with solvents, and the fraction extracted with petroleum ether was characterized using GC and GC mass spectrometer. The results indicated that odd-numbered linear hydrocarbons were produced, although the major products of this polymerization were even-numbered. It is concluded from the accumulated experimental results that a carbonium ion mechanism rather than radical mechanism is probable for the mechanochemical polymerization induced by fracture of γ-alumina.     

乙烯、苯气相烷基化合成乙苯中间试验

在上海石油化工研究院开发的分子筛催化剂和联合化学反应工程研究所华东化工学院分所小试过程开发的基础上，建立了年产３００ｔ乙苯的中试装置，进行了由乙烯、苯气相烷基化合成乙苯的中试研究，为工业生产提供了设计依据。     

Radiation-induced emulsion polymerization of tetrafluoroethylene

The radiation-induced emulsion polymerization of tetrafluoroethylene was carried out with the use of ammonium perfluorooctanoate as an emulsifier at an initial pressure of ca. 30–35 Kg/cm². The polymerization rate was shown to be proportinal to about the 0.8 power of the dose rate in the range of 2 × 10⁴ to 10⁵ R/hr and to be almost independent of emulsifier concentration. The molecular weight of the polymer lies in the range of 10⁴ to 10⁵, increases with reaction time at the initial stage, and decreases with emulsifier concentration, but is independent of the dose rate from 2 × 10⁴ to 6 × 10⁴ R/hr. If the emulsifier is not used, a polymer with a molecular weight as high as 1.8 × 10⁶ to 2 × 10⁷ is obtained. Apparently, the emulsifier and its radiolysis products act as chain transfer agents. Postirradiation polymerization was found to take place with the formation of products with increased molecular weight.     

Low-pressure polymerization of ethylene. II

This paper presents the kinetic study of polymerization of ethylene with VOCl₃ and aluminum alkyls such as Et₃Al and Et₂AlCl. The effect of various parameters like the [Al]/[V] ratio, catalyst concentration, reaction time, temperature, solvents, and additives on rate of the reaction, yield, and molecular weight is reported. Each of these parameters has a remarkable effect on the yield and the rate of polymerization for both catalyst systems. Triethylamine is found to increase the catalyst efficiency and the rate. It is also observed that aliphatic hydrocarbons acted as a better polymerization medium than did the aromatic ones.     

前脱乙烷流程乙烯装置的凝液汽提工艺研究

在百万吨级前脱乙烷流程的乙烯装置裂解气压缩机工艺系统中进行了凝液汽提工艺的研究。模拟计算了凝液汽提塔在裂解气压缩机第五段出口时裂解气压缩、分离和制冷系统的变化情况,考察了该塔塔压的变化对这些系统的影响。研究结果表明,应用凝液汽提塔可降低脱乙烷塔塔底温度13℃以上,当凝液汽提塔塔压与裂解气压缩机第四段吸入口压力平衡时,综合能耗最低。建议在新建前脱乙烷流程的乙烯装置时应用凝液汽提塔,并将它设置在裂解气压缩机第五段出口。     

乙醇脱水制乙烯水资源循环利用研究

乙醇脱水制乙烯工艺废水蒸气中含有多种组分,其中催化剂粉末(w)≤0.2%、乙醇(w)≤1.5%、有机酸(w)≤0.5%、醇类(除乙醇)(w)≤0.8%、乙烯(w)≥48.5%;温度高达200℃。将废水蒸气冷却至105~110℃除去高浓度污泥后,将气相组分冷却至常温,再通过汽提除去易挥发组分,然后进行均质调节、机械过滤、IC厌氧反应器厌氧处理、生物滤池好氧曝气处理、PAM絮凝过滤后,作为中水循环利用。