A systematic approach to the study of multicomponent polymerization kinetics: butyl acrylate/methyl methacrylate/vinyl acetate. III. Emulsion homopolymerization and copolymerization in a pilot plant reactor

A systematic study of the terpolymerization of butyl acrylate/methyl methacrylate/vinyl acetate (BA/MMA/VAc) is being conducted. In this third stage of the study,

1 Parts 1 and 2: Dubé, M. A. & Penlidis, A., Polymer, 36 (1995) 587. Dubé, M. A. & Penlidis, A., Macromol. Chem. Phys., 196 (1995) 1101.

emulsion homopolymerizations and copolymerizations of the monomers comprising the BA/MMA/VAc system were performed in a 5 litre stainless steel pilot plant reactor, mainly for troubleshooting purposes and as a precursor to the detailed terpolymerization experiments to follow. First, a search for a stable emulsion recipe was conducted. At the same time, experimental procedures were established for the 5 litre pilot plant reactor along with product characterization techniques. Finally, selective emulsion homopolymerizations and copolymerizations were run for each of the three monomers and each combination of the three monomers, respectively. The polymers produced were characterized for conversion, composition, molecular weight and particle size. Although the emphasis of the experiments was to establish recipes, techniques, and procedures for emulsions terpolymerization, several useful observations were made regarding the kinetics even from these troubleshooting experiments.     

醋酸锌/炭小球催化剂的制备及其催化合成醋酸乙烯性能

以炭小球(SAC)为载体,采用过量浸渍法制备了不同醋酸锌负载量的醋酸锌/炭小球催化剂,在常压固定床反应器上,考察了醋酸锌负载量、反应温度、乙炔和醋酸摩尔比、空速等因素对乙炔合成醋酸乙烯的影响。采用SEM,BET,XRD等表征手段研究了催化剂活性降低的机理。研究表明,活性组分的流失和反应过程中形成的少量积炭是催化剂活性下降的2个重要原因。当催化剂中醋酸锌负载量(质量分数)为32.05%,常压,反应温度220℃,C2H2/HAc摩尔比为3∶1,乙炔体积空速为500 h-1,反应110 h后,醋酸的单程转化率为24.20%,醋酸乙烯选择性为98.50%,醋酸锌/炭小球催化剂催化合成醋酸乙烯的生产能力可达2.95 g/(mL.d),比高比表面活性炭催化剂的生产能力高35.32%,且该催化剂具有良好的催化活性、醋酸乙烯选择性和反应稳定性。     

乙烯气相法和乙炔气相法合成醋酸乙烯的催化剂的研究进展

合成醋酸乙烯的工艺主要有乙烯气相法和乙炔气相法两种工艺.乙烯气相法普遍采用的催化剂为Pd-Au/SiO2,它的缺点是成本高、寿命短、易失活;乙炔气相法采用最广泛的是醋酸锌/活性炭催化剂,具有寿命短、活性低等方面的缺点.概述了乙烯气相法和乙炔气相法生产醋酸乙烯所需催化剂的现状,指出了主要催化剂存在的缺点,并提出了解决措施...     

活性炭负载醋酸锌催化剂真空干燥的特性

通过真空干燥实验研究了供热温度、真空度、料层厚度等因素对醋酸锌-活性炭催化剂干燥规律的影响。实验结果表明:醋酸锌-活性炭催化剂采用真空干燥可以实现快速低温干燥;催化剂的干燥只有降速干燥阶段,而没有常速干燥阶段;供热温度的提高有助于提高干燥速率,但温度超过80℃时催化剂出现轻微粉化;真空度越高,干燥速率特别是初始干燥速率越快;料层厚度的增加,使干燥时间延长,但设备的干燥强度有所提高。正交实验得出,在多因素条件下,温度对干燥强度的影响最大,其次是真空度和料层厚度。     

Probing the reaction kinetics of vinyl acetate free radical polymerization via living free radical polymerization (MADIX)

Living free radical polymerization technology (macromolecular design via the interchange of xanthates (MADIX)) was applied to give accesses to chain length and conversion dependent termination rate coefficients of vinyl acetate (VAc) at 80 °C using the MADIX agent 2-ethoxythiocarbonylsulfanyl-propionic acid methyl ester (EPAME). The kinetic data were verified and probed by simulations using the PREDICI^® modelling package. The reversible addition-fragmentation transfer (RAFT) chain length dependent termination (CLD-T) methodology can be applied using a monomer reaction order of unity, since VAc displays significantly lower monomer reaction orders than those observed in acrylate systems (ω(VAc, 80 °C)=1.17±0.05). The observed monomer reaction order for VAc is assigned to chain length dependent termination and a low presence of transfer reactions. The α value for the chain length regime of log(i)=1.25−3.25 (in the often employed expression ) reads 0.09±0.05 at low monomer to polymer conversion (10%) and increases significantly towards larger conversions (α=0.55±0.05 at 80%). Concomitantly with a lesser amount of midchain radicals, the chain length dependence of k_t is significantly less pronounced in the VAc system than in the corresponding acrylate systems under identical reaction conditions. The RAFT(MADIX)-CLD-T technique also allows for mapping of k_t as a function of conversion at constant chain lengths. Similar to observations made earlier with methyl acrylate, the decrease of k_t with conversion is more pronounced at increased chain lengths, with a strong decrease in k_t exceeding two logarithmic units from 10 to 80% conversion at chain lengths exceeding 1800.     

LHQ-11催化剂在Unipol工艺上的中试研究

茂金属聚乙烯催化剂在Unipol气相法中试装置上进行了聚合评价试验。对催化剂活性、氢调敏感性、共聚性能、运行稳定性以及产品性能分析表明,LHQ-11催化剂的催化活性及其他综合性能与国外对比催化剂相当。     

Microwave heating of cottonseed: A pilot plant study

Two cottonseed samples (50 kg) were exposed to microwaves at 45 KW and 2450 MHz for 4 min in an air temperature of 94°C. The final temperature of the seed was 76°C, and the treatment caused a 20% reduction in seed moisture. Examination of the seed immediately after microwave heating (MWH) indicated no differences in the total or soluble protein content of the meal or the content, quality or color of the oil as compared with unheated seed. There was some reduction in the quality of the oil from unheated seed during storage, but only minimal reduction in the quality of the oil from the MWH samples. Protein quality deteriorated in all samples; however, the deterioration was reduced in the microwave-heated seed.     

抗冲级苯乙烯-马来酸酐共聚树脂的本体半连续中试研究

在原有二元SMA中试装置上进行了抗冲级SMA的本体半连续中试研究 ,考察了补加速率、搅拌转速、添加少量溶剂等因素对中试反应及产品性能的影响 ,试验结果表明现有设备虽然在传热能力上尚欠不足 ,但通过调整聚合工艺 ,可以制得与国外同类产品性能相当的抗冲级SMA产品     

Activated carbon‐filled cellulose acetate hollow‐fiber membrane for cell immobilization and phenol degradation

The activated carbon‐filled cellulose acetate (CA) hollow‐fiber membranes were prepared by using phase‐inverse technique and subsequently characterized by scanning electronic microscopy (SEM), atomic force microscopy (AFM), dynamic mechanical analysis (DMA), thermal mechanical analysis (TMA), and tensile analysis. The SEM observation demonstrated that the activated carbon‐filled CA hollow‐fiber membranes possess four‐layer structure, which consists of an external skin dense layer, an external void layer, a central sponge layer, and an internal skin dense layer, whereas the pure CA hollow‐fiber membranes lack the macrovoid layer. As the measurement of AFM, the roughness of both internal and external surface of activated carbon‐filled fibers is much higher than that of pure CA fiber, respectively. Higher Young's modulus and storage modulus of filled membranes indicate that the activated carbon particles were homogeneously dispersed in the polymeric matrix. To investigate the feasibility of the newly developed hollow‐fiber membranes for cell immobilization cells and to evaluate the inhibitory effect of phenol on immobilized cells, Pseudomonas putida ATCC 17484 was chosen to be immobilized on both pure CA and activated carbon‐filled hollow‐fiber membranes. Batch experiments for phenol biodegradation were carried out for both free suspension and immobilized cells at the initial concentration of 1500 mg/L phenol. In the case of free suspension, neither cell growth nor phenol degradation occurred to any measurable extent up to 35 h. We found that both pure CA fiber and activated carbon‐filled fiber immobilization systems can completely degrade the phenol. However, the biodegradation rate of activated carbon‐filled fiber system was higher than that of pure CA fiber system. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 695–707, 2000     

Laboratory‐ and pilot plant‐scale study on the dehydration of cyclohexane by pervaporation

In this work, pervaporation is applied for the dehydration of industrial cyclohexane, used as a solvent and reaction medium in the manufacture of synthetic rubbers. Working with initial concentrations of water in cyclohexane within the range of 0.090–0.110 kg m^?3, an experimental study was performed (i) in the laboratory, using a radial cell with a membrane area of 0.0178 m²; and (ii) in a pilot plant located at the industrial site, with a plate‐and‐frame membrane module and a total membrane area of 3 m 2 . In both cases, the same pervaporation membrane, with a preferential flux of water, was used. The mass transfer coefficient was determined, together with its dependence on the hydrodynamic regime. The higher hydraulic resistance of the plate‐and‐frame module generated a pressure decrease that limited the feed velocity, thus increasing the mass transfer resistance of the pervaporation process in comparison with the bench‐scale system. Copyright © 2005 Society of Chemical Industry     

Use of a liquid chemical waste to produce a clay–carbon adsorbent

The feasibility of producing an adsorbent from an alkaline aqueous tarry industrial waste has been investigated in this study. The inherent disadvantages of producing a solid carbonaceous material from a waste with its organic content in a dissolved state were overcome by neutralising the waste liquor to pH<2 in the presence of fuller's earth, filtering and producing a solid cake more suitable for thermal treatment. Optimisation of this procedure, followed by ZnCl₂ activation, produced clay–carbon adsorbents with surface areas of up to 225 m² g⁻¹ capable of adsorbing 28% of phenol and 35% of 4-nitrophenol from 10 mM aqueous solution. The potential of this procedure in a beneficial waste reduction and re-use context are highlighted. © 1998 SCI     

Polymerization of vinyl acetate using visible radiation and a dye-reducing agent sensitizer: 1. Pre-initiation and initiation reactions involving ethyl eosin and ascorbic acid

The ethyl eosin/ascorbic acid photosensitized polymerization of vinyl acetate in aqueous methanol using visible radiation has been shown to occur by a mechanism in which polymerization occurs after an induction period during which the dye colour fades completely. During this period the dye is excited by incident radiation and reacts with the reducing agent to form free radical species. These react with dissolved oxygen to produce hydrogen peroxide. It is shown that the polymerization of vinyl acetate is initiated by products of the reaction between ascorbic acid and hydrogen peroxide.     

Steam-activated carbons from a bituminous coal in a continuous multistage fluidized bed pilot plant

A vertical three-stage fluidized bed pilot plant, with downcomers, was designed and built in order to study the continuous process of the production of activated carbons from a high-volatile bituminous coal from the Puertollano basin (Spain), by steam activation. The pilot plant can operate with a production of up to 40 kg per day. Very good activated carbons were produced at the selected operating conditions. The effect of the following operating conditions on the reactivity and adsorption characteristics of the activated carbons was analyzed: (1) carbonization conditions (one- and two-step activation), (2) activation temperature (800–850 °C), and (3) steam gas velocity (1.5–3 times the minimum fluidization velocity). Carbonization conditions considerably affect the reactivity of the chars obtained; the faster the carbonization process, the higher the reactivity. Nevertheless, the effect of this variable on the development of porosity is not very relevant, and consequently the direct activation process is an attractive alternative to the two-step (carbonization and activation) process. On the other hand, both temperature and steam flow rate (affecting the reaction rate) have a marked effect on the development of porosity.     

磷酸、氯化锌活化亚麻屑制备活性炭过程中的行为对比

以亚麻屑为原料,采用磷酸和氯化锌进行了对比活化实验,探讨了浸渍比、活化温度对活性炭的吸附性能、得率和比表面积的影响。结果表明,在浸渍比为300∶1,500℃下活化60 m in,均能得到吸附性能较好的活性炭,其中碘值是氯化锌法高于磷酸法,亚甲基蓝吸附则是磷酸法高于氯化锌法,说明在活化过程中磷酸和氯化锌对活性炭的影响不尽相同,孔隙结构存在差别。     

CO2 capture from dry flue gas by vacuum swing adsorption: A pilot plant study

The capture and concentration of CO₂ from a dry flue gas by vacuum swing adsorption (VSA) has been experimentally demonstrated in a pilot plant. The pilot plant has the provision for using two coupled columns that are each packed with approximately 41 kg of Zeochem zeolite 13X. Breakthrough experiments were first carried out by perturbing a N₂ saturated bed with 15% CO₂ and 85% N₂ feed, which is representative of a dry flue gas from coal‐fired power plants. The breakthrough results showed long plateaus in temperature profiles confirming a near adiabatic behavior. In the process study, a basic four‐step vacuum swing adsorption (VSA) cycle comprising the following steps: pressurization with feed, adsorption, forward blowdown, and reverse evacuation was investigated first. In the absence of any coupling among the steps, a single bed was used. With this cycle configuration, CO₂ was concentrated to 95.9 ± 1% with a recovery of 86.4 ± 5.6%. To improve the process performance, a four‐step cycle with light product pressurization (LPP) using two beds was investigated. This cycle was able to achieve 94.8 ± 1% purity and 89.7 ± 5.6% recovery. The Department of Energy requirements are 95% purity and 90% recovery. The proposed underlying physics of performance improvement of the four‐step cycle with LPP has also been experimentally validated. The pilot plant results were then used for detailed validation of a one‐dimensional, nonisothermal, and nonisobaric model. Both transient profiles of various measured variables and cyclic steady state performance results were compared with the model predictions, and they were in good agreement. The energy consumptions in the pilot plant experiments were 339–583 ± 36.7 kWh tonne^?1 CO₂ captured and they were significantly different from the theoretical power consumptions obtained from isentropic compression calculations. The productivities were 0.87–1.4 ± 0.07 tonne CO₂ m^?3 adsorbent day^?1. The results from our pilot plant were also compared with available results from other pilot plant studies on CO₂ capture from flue gas. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1830–1842, 2014     

Biotransformation of (+)‐ and (−)‐bornyl acetate using the plant parasitic fungus Glomerella cingulata as a biocatalyst

The microbial transformations of (+)‐ and (?)‐bornyl acetate were investigated using the plant parasitic fungus, Glomerella cingulata. As a result, (+)‐ and (?)‐bornyl acetate were converted to (+)‐ and (?)‐5‐exo‐hydroxybornyl acetate, (+)‐ and (?)‐5‐oxobornyl acetate and (+)‐ and (?)‐borneol respectively. The structures of the metabolic products were determined by spectroscopic data. © 2001 Society of Chemical Industry     

西部地区兴建大型LDPE装置可行性分析

从经济性、技术性和市场3个方面分析了西部地区兴建大型低密度聚乙烯（LDPE）装置的可行性，指出在西部地区兴建大型LDPE装置，可以提高中西部地区LDPE的自给率，缓解我国LDPE专用料的缺乏，同时可享受西部大开发的相关政策；通过对投资、生产费用及产品销售价格等方面的比较，指出建设LDPE装置与线型低密度聚乙烯装置相比具有相当的竞争力，并建议对兴建LDPE装置采用管试法生产工艺。