Polymerization of olefins through heterogeneous catalysis. XIV. The influence of temperature in the solution copolymerization of ethylene

The influence of temperature variation on the kinetics and the polymer properties in the homo- and copolymerization of ethylene in a solution reactor is discussed. The Polymerization is conducted in a semibatch mode at 320 Psig total reactor pressure for 10 min polymerization time. Temperature variations in the range 145–200°C in both home-and copolymerization of ethylene with 1-octene shows that the highest catalyst yield was obtained at temperature of 165–175°C. At the optimal temperature, a high initial maximum in the rate of ethylene consumption is attained in a few seconds followed by a relatively slow decay when compared with polymerization conducted at higher temperatures. Polymerization at temperatures ≥ 185°C resulted in a lower peak in the consumption rate of ethylene accompanied by a rapid decay with time. In the case of ethylene/1-Octene copolymerization, a rather low comonomer incorporation level is obtained at the conditions employed; the 1-octene incorporated was only 0.2–0.7 mol %. Higher M_w values, of about 350,000 at 145°C, are obtained in homopolymerization in comparison to M_w values obtained in copolymerization, of about 195,000 at the same temperature. Over the temperature range of 145–200°C, both M_w and M_n values vary by about 40%. © 1993 John Wiley & Sons, Inc.     

Polymerization of olefins through heterogeneous catalysis. XVI. Design and control of a laboratory stirred bed copolymerization reactor

A novel lab-scale stirred bed gas phase reactor system has been designed and constructed for investigating the kinetic behaviour of olefin copolymerization reactions using heterogeneous catalysts. The system, equipped for basic temperature and pressure control, also includes an on-line composition control system which maintains close control of reactor composition for gaseous and liquid monomers as well as for hydrogen. With this apparatus, it is now possible to investigate the fundamental kinetic features of the catalyst system with high precision. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 373–382, 1997     

Polymerization of olefins through heterogeneous catalysis. XVIII. A kinetic explanation for unusual effects

The development of a detailed kinetic model describing some of the unusual effects observed in catalyzed olefin polymerization is presented. Based on the method of moments, the model describes the rate effects of hydrogen and comonomers, as well as the ability of certain systems to incorporate long chain branches via internal and/or terminal double bond polymerization. Examples are provided demonstrating the model's ability to predict rates and degrees of polymerization with ethylene, propylene, and 1-hexene monomers. In the case of propylene, multiple insertion mechanisms are modeled and compared with experimental sequence length and end group data. In other examples the model is used to simulate an oscillating metallocene catalyst and a metallocene catalyst capable of branch addition via terminal double bond polymerization. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1053–1080, 1997     

Polymerization of olefins through heterogeneous catalysis XI: Gas phase sequential polymerization kinetics

A unique series of ethylene and propylene sequential polymerization experiments have been carried out in a stirred bed gas phase reactor using unsupported Stauffer AA catalyst (TiCl₃· $\frac{1}{3}$AlCl₃). Several interesting kinetic results were observed. It was found that propylene causes rate enhancement for a subsequent ethylene polymerization but that ethylene causes a rate reduction for a subsequent propylene polymerization. Furthermore, the rate enhancement/reduction effect increases with the duration of the preceding polymerization. Chemical/kinetic effects were found to be the likely causes of both the rate enhancements and the rate reductions observed during sequential polymerization. It was also shown that enhanced monomer sorption caused by the presence of a more soluble component, such as a heavier comonomer, does contribute to rate enhancement during simultaneous copolymerizations, but is not a factor for sequential polymerizations. © 1993 John Wiley & Sons, Inc.     

Polymerization of olefins through heterogeneous catalysis X: Modeling of particle growth and morphology

The development of a detailed model describing particle growth in olefin copolymerization systems is presented. The Multigrain Model considers in detail monomer sorption, mass transfer, and changing porosity within the growing particle, as well as heat and mass transfer across the external film of the particle. The model predicts catalyst performance, including polymerization rates and particle morphology, in different reactor media without parameter adjustment. Internal void fractions are calculated through an examination of the relative growth rates within the growing particle. The model is used to examine the effects of mass transfer limitations, prepolymerization, and nonuniform metal distribution on the particle growth process. Model predictions of morphology show the same trends as observed experimentally.     

Polymerization of olefins through heterogeneous catalysis. II. Kinetics of gas phase propylene polymerization with Ziegler–Natta catalysts

Propylene was polymerized in gas phase over a \documentclass{article}\pagestyle{empty}\begin{document}${\rm TiCl}_3 \cdot \frac{1}{3}{\rm AlCl}_3$\end{document} (Stauffer Type AA) Catalyst with AlEt₂Cl cocatalyst both with and without H₂ present. The effects of polymerization temperature, monomer concentration, catalyst composition, and hydrogen were investigated. The experiments were carried out at operating conditions approaching industrial practice.     

Polymerization of olefins through heterogeneous catalysis,I. Low pressure propylene polymerization in slurry with Ziegler–Natta catalyst

Propylene was polymerized in slurry over a TiCl₃·? AICI₃ (Stauffer Type AA) catalyst with Al—Et₂Cl cocatalyst at 60 psig pressure both with and without H₂ present. The effects of polymerization temperature, catalyst poisons, and type of slurry liquid were investigated, with particular emphasis on the yield, tacticity, and MWD of the resulting polymer. The highest yields and isotactic content were obtained with decane–heptane mixtures as a slurry liquid, while slurry liquids in which polypropylene was most soluble gave the narrowest MWD.     

Polymerization of olefins through heterogeneous catalysis. III. Polymer particle modelling with an analysis of intraparticle heat and mass transfer effects

Propylene and ethylene polymerization in liquid and gas media are described by a multigrain particle model. Intraparticle heat and mass transfer effects are investigated for a range of catalyst activities. For slurry polymerization, intraparticle mass transfer effects may be significant at both the macroparticle and microparticle level; however, for normal gas phase polymerization, microparticle mass transfer effects appear more likely to be important. Intraparticle temperature gradients would appear to be negligible under most normal operating conditions.     

Polymerization of olefins through heterogeneous catalysis. VI. Effect of particle heat and mass transfer on polymerization behavior and polymer properties

The multigrain model for polymerization of olefins over solid catalysts is used to predict kinetic behavior, molecular weights, and polydispersities. The effects of intraparticle and external boundary layer transport resistance on the kinetic behavior and polymer properties are explored. Means for the experimental detection of intraparticle diffusion resistance are suggested. The importance of catalyst physical properties, such as the porosity, and the catalyst loading is illustrated through simulation. Finally, the hypotheses of diffusion resistance and site heterogeneity as explanations for the broad molecular weight distributions of olefin polymers are critically evaluated, and molecular weight distribution control in industrial catalysts is discussed.     

Polymerization of olefins through heterogeneous catalysis. IX. Experimental study of propylene polymerization over a high activity MgCl2-supported Ti catalyst

Results from an experimental study of propylene polymerization in heptane diluent over a high activity Mg-supported Ti catalyst are presented. The study provides an examination of the effect of operating conditions on polymerization rate, product melt index, and powder bulk density. Among the findings are that product bulk density decreases with increasing operating temperature and decreasing operating pressure while prepolymerization increases the bulk density. The results support the hypothesis that polymer morphology is closely linked to mass transfer limitations within the growing polymer particle during the early stages of polymerization.     

Polymerization of olefins through heterogeneous catalysis—V. Gas-liquid mass transfer limitations in liquid slurry reactors

Many processes for polymerization of olefins employ laboratory, pilot plant, or full-scale liquid-phase polymerization reactors with monomer introduced as a gas. Criteria for the presence of gas-liquid mass transfer resistance in these systems are determined in terms of observed reaction rate or loading of a heterogeneous catalyst of given intrinsic activity. The effects of variables such as reactor size and configuration, temperature, and soluble polymer are also examined. The equilibrium monomer concentrations of ethylene in hexane and propylene in heptane are calculated through a modified Benedict-Webb-Rubin equation, and some calculations for ethylene-propylene mixtures are tabulated. The general methodology for predicting gas-liquid mass transfer resistance is readily extendible to copolymerization systems.     

Polymerization of olefins through heterogeneous catalysis. XVII. Experimental study and model interpretation of some aspects of olefin polymerization over a TiCl4/MgCl2 catalyst

Using a high-activity MgCl₂-supported TiCl₄ catalyst, kinetic studies of ethylene and propylene polymerization are conducted in a semi-batch gas phase stirred-bed reactor system. Based on the experimental observations obtained from this study and others in the literature, simple kinetic mechanisms are proposed to explain the data. This model considers both the site formation from the interaction of catalyst and cocatalyst as well as the participation of monomers during site activation. By using this model together with parameters estimated from various sources, some aspects of kinetic behavior have been successfully predicted. These include the rate enhancement introduced by α-olefins, the effect of the Al/Ti ratio on kinetic features such as catalyst activity and decay rate, as well as the different reaction orders observed for various monomers. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1037–1052, 1997     

乙烯和环烯烃共聚用有机金属催化剂

配位催化共聚是制备环烯烃共聚物的主要方法,目前商品化的环烯烃共聚物主要由乙烯与降冰片烯或者四环十二碳烯共聚得到。共聚单体及其含量是决定环烯烃共聚物性能的关键因素,而决定共聚单体含量的最核心因素是催化剂。本文从催化剂结构的角度出发,综述了乙烯和降冰片烯/四环十二碳烯共聚用有机金属催化剂,从双茂有机金属催化剂、单茂有机金属催化剂、非茂有机金属催化剂、后过渡金属催化剂等部分进行论述,同时论述了催化剂结构及关键聚合工艺（如温度、压力、单体浓度等）对催化活性及共聚单体插入量的重要影响。此外,由于乙烯与四环十二碳烯共聚活性低,未来针对该共聚反应的研究会继续进行。合成更多新结构的配体、开发更高活性的催化剂、构建更经济有效的反应体系将会是新的研究重点。     

Polymerization of olefines through heterogeneous catalysis IV. Modeling of heat and mass transfer resistance in the polymer particle boundary layer

Propylene and ethylene polymerization in liquid and gas media are described by a multigrain particle model. External boundary layer heat and mass transfer effects are investigated for various catalysts and operating conditions. For high-activity catalysts used in slurry, external film mass transfer effects may be significant. For gas-phase polymerization of propylene or ethylene, the model predicts significant particle overheating at short times, which may explain the particle sticking and agglomeration problems sometimes observed in industrial reactors.     

Polymerization of olefins with bulky substituents. 1. Homo- and copolymerization of 3-(1-adamantyl)propene

The use of bulky substituents like adamantane has been shown in the past to influence the glass transition temperatures of polymers significantly. In this paper the synthesis and homopolymerization of the monomer 3-(1-adamantyl) propene is described, as well as the copolymerization of this monomer with ethene, propene, 1-pentene, 4-methyl-1-pentene, 1-hexene and 1-octene. The resultant copolymers proved to be largely insoluble in organic solvents. It was also demonstrated that the presence of the bulky methyladamantyl side group influenced the glass transition temperatures of the copolymers in comparison with the corresponding homopolymers.     

The electronic structure effect in heterogeneous catalysis

Using a combination of density functional theory calculations and X-ray emission and absorption spectroscopy for nitrogen on Cu and Ni surfaces, a detailed picture is given of the chemisorption bond. It is suggested that the adsorption bond strength and hence the activity of transition metal surfaces as catalysts for chemical reactions can be related to certain characteristics of the surface electronic structure.