Download or read book Kinetic Investigation of Different Supported Catalysts for the Polymerization of Propylene Under Industrially Relevant Conditions written by Joana Kettner and published by Cuvillier. This book was released on 2019-05-14 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt: Scope of the work is the kinetic investigation of two fourth generation Ziegler-Natta catalysts as well as a supported metallocene catalyst for the polymerization of propylene under industrially relevant conditions and the development of simplified phenomenological kinetic models describing the polymerizations. Therein, the influence of different reaction conditions (temperature, pressure, hydrogen concentration) and, in particular, the effect of prepolymerization on catalyst kinetics as well as on polymer characteristics are studied. The Ziegler-Natta catalysts were investigated under gas-phase conditions in a 5 l horizontal stirred tank reactor operating in semi-batch mode. Both catalysts showed a similar kinetic behavior as well as hydrogen response at the different reaction conditions. Applying a prepolymerization led to an increase in activity at higher reaction temperatures as well as an improved polymer morphology. The impact of prepolymerization is catalyst specific and depends on the catalyst activity reached at main polymerization temperature. The supported metallocene catalyst was studied under bulk conditions in liquid propylene using a special 250 ml reaction calorimeter. A focus was set on procedure development (in-situ and external prepolymerization) with the target of defined prepolymerization conditions and early access to the kinetic profile. Final kinetic measurements were carried out using the developed external prepolymerization procedure. Based on the experimental studies, simplified phenomenological kinetic models are developed for each catalyst type enabling the quantitative description of the polymerization reactions at the different reaction conditions including the effect of prepolymerization. Main hypothesis for the mathematical description of the prepolymerization effect is that particle overheating at the beginning of the polymerization is the major reason for lower activities obtained when no prepolymerization is applied. For particle

Download or read book Introduction to Industrial Polypropylene written by Dennis B. Malpass and published by John Wiley & Sons. This book was released on 2012-07-02 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt: This introductory text is an important resource for new engineers, chemists, students, and chemical industry personnel to understand the technical aspects of polypropylene which is the 2nd largest synthetics polymer in manufactured output. The book considers the following topics: What are the principal types of polypropylene and how do they differ? What catalysts are used to produce polypropylene and how do they function? What is the role of cocatalysts and how have they evolved over the years? How are industrial polypropylene catalysts tested and the resultant polymer evaluated? What processes are used in the manufacture of polypropylene? What are the biopolymer alternatives to polypropylene? What companies are the major industrial manufacturers of polypropylene? What is the environmental fate of polypropylene?

Download or read book Introduction to Industrial Polyethylene written by Dennis B. Malpass and published by John Wiley & Sons. This book was released on 2010-06-28 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt: Demystifies the largest volume manmade synthetic polymer by distillingthe fundamentals of what polyethylene is, how it's made and processed,and what happens to it after its useful life is over. Endorsement for Introduction to Industrial Polyethylene "I found this to be a straightforward, easy-to-read, and useful introductory text on polyethylene, which will be helpful for chemists, engineers, and students who need to learn more about this complex topic. The author is a senior polyethylene specialist and I believe we can all benefit from his distillation of knowledge and insight to quickly grasp the key learnings." —R.E. King III; Ciba Corporation (part of the BASF group) Jargon used in industrial polyethylene technology can often be bewildering to newcomers. Introduction to Industrial Polyethylene educates readers on terminology commonly used in the industry and demystifies the chemistry of catalysts and cocatalysts employed in the manufacture of polyethylene. This concise primer reviews the history of polyethylene and introduces basic features and nomenclatures for this versatile polymer. Catalysts and cocatalysts crucial to the production of polyethylene are discussed in the first few chapters. Latter chapters provide an introduction to the processes used to manufacture polyethylene and discuss matters related to downstream applications of polyethylene such as rheology, additives, environmental issues, etc. Providing industrial chemists and engineers a valuable reference tool that covers fundamental features of polyethylene technology, Introduction to Industrial Polyethylene: Identifies the fundamental types of polyethylene and how they differ. Lists markets, key fabrication methods, and the major producers of polyethylene. Provides biodegradable alternatives to polyethylene. Describes the processes used in the manufacture of polyethylene. Includes a thorough glossary, providing definitions of acronyms and abbreviations and also defines terms commonly used in discussions of production and properties of polyethylene. Concludes with the future of industrial polyethylene.

Download or read book Characterization of the Zr polymeryl Species Present During Ethylene and Propylene Polymerizations by Homogeneous Zirconocene Catalysts written by and published by . This book was released on 2008 with total page 428 pages. Available in PDF, EPUB and Kindle. Book excerpt: A detailed investigation of Zr-polymeryl intermediates, present during ethylene and propylene polymerization by metallocene and non-metallocene catalysts, is presented. In this regard, the potential use of bromine as a quenching agent to give polymers with brominated end groups is investigated. Using NMR spectroscopy, these groups can be identified as primary or secondary and quantified, thus providing information on the nature of the Zr-polymeryl linkage(s) and their relative concentration(s). Bromine quenching was examined for ethylene polymerization by Cp2ZrMe2/B(C6F5)3, and for propylene polymerization by Cp2ZrMe2/B(C6F5)3, (indenyl)2ZrMe2/B(C6F5)3, and rac-{C2H4(1-indenyl)2}ZrMe2/B(C6F5)3. Polymers with primary alkyl bromide end groups were obtained. In the case of propylene polymerization by [ONNO]Zr(CH2C6H5)2/MAO/2,6-di-tbutylphenol, both primary and secondary alkyl bromide end groups were detected. Primary alkyl bromide end groups result from the cleavage by bromine of primary Zr-CH2~polymeryl linkages while secondary alkyl bromides are the result of the cleavage by bromine of secondary Zr-CH(Me)CH2~polymeryl linkages. The concentration of Zr-CH2~polymeryl intermediates was found to be low, suggesting that the catalyst deactivates during the polymerization. A second objective of this research is to investigate the formation of Cp2Zr+-allyl complexes as these species are proposed to arise during the polymerization and deactivate the catalyst. Compounds of type [Cp2ZrMe]+ were found to react with vinylidene compounds of type CH2=C(Me)R, (R = CH2CHMe2 and CH2CH(Me)C3H7), to form methane and Cp2Zr+-allyl complexes. The reaction of Cp2ZrMe2/[Ph3C][B(C6F5)4] with CH2=C(Me)CH2CHMe2 involves the unprecedented [Cp2Zr(Me)(CH2CMeCH2CHMe2)]+ intermediate, detected by low temperature one- and two-dimensional NMR spectroscopy. The observation of this intermediate represents the first direct experimental evidence for a d0 metal-alkyl-olefin complex. The dynamic behavior and the kinetics of formation of Cp2Zr+-allyl complexes were also investigated by NMR spectroscopy. In situ propylene polymerization studies indicate that Cp2Zr+-allyl polymeryl intermediates form under catalytic conditions when either Cp2ZrMe2/B(C6F5)3 or Cp2ZrMe2/[Ph3C][B(C6F5)4] are used. Formation of Zr-allyl species occurs in the early stages of the polymerization process, even before the [Cp2ZrMe]+ catalyst is completely consumed, by recoordination of the polypropylene-containing vinylidene end groups, which are the normal products of chain transfer reactions via -H elimination, to the active catalyst.

Download or read book Optimization of a Tool to Study the Start up of the Gas Phase Olefin Polymerization written by Estevan Tioni and published by . This book was released on 2011 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The early stages (from less than 1s to few minutes) of catalytic olefin polymerization are still fairly understood even if they are nowadays recognized to be crucial for the determination of the morphology of the polymer particle, the optimization of the whole catalyst performance and the thermal stability of the process. In this work we will present how we studied and optimized a specially conceived packed bed reactor to perform gas phase catalytic olefin polymerizations as short as 0.1s under industrially relevant conditions. The possibility to measure the reactor temperature and to recover unaltered the polymer particles allows to take a complete picture of the catalyst behavior at the reaction start-up. The study will be restrained to ethylene polymerization with silica supported metallocenes and special attention will be given to the relation between heat transfer from the growing particle and catalyst performance. It will be seen how particle temperature evolution can be followed indirectly by measuring the gas phase temperature .In the second part of this work different metallocene complexes will be used to study the influence of process conditions, catalyst preparation method and support properties on the evolution of reaction rate, and polymer MWD during the first reaction seconds. Special attention will be given to the active site evolution during the transient phase and it will be shown that temperature excursions can be responsible for a local variation in active site behavior thus altering the properties of the formed polymer. The last section will be dedicated to the study of the peculiar crystallization behavior of the polymer chains in an evolving inorganic support. It will be shown how the melting and crystallization temperatures of the polymers can be used as “sensors” to measure the degree of fragmentation of the support particle. The results obtained in this work allow to gain a deeper understanding of the key parameters for the polymerization start-up and can be used as input for single particle models thus allowing to reduce the gap actually present between real catalyst behavior and model predictions.

Download or read book Olefin Polymerization written by Walter Kaminsky and published by Wiley-VCH. This book was released on 2006-08-18 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: With an enormous velocity, olefin polymerization has expanded to one of the most significant fields in polymers since the first industrial use about 50 years ago. In 2005, 100 million tons of polyolefins were produced - the biggest part was catalyzed by metallorganic compounds. The Hamburg Macromolecular Symposium 2005 with the title "Olefin Polymerization" involved topics such as new catalysts and cocatalysts, kinetics, mechanism and polymer reaction engineering, synthesis of special polymers, and characterization of polyolefins. The conference combined scientists from different disciplines to discuss latest research results of polymers and to offer each other the possibility of cooperation. This is reflected in this volume, which contains invited lectures and selected posters presented at the symposium.

Download or read book Polypropylene Handbook written by József Karger-Kocsis and published by Springer. This book was released on 2019-03-18 with total page 648 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book extensively reviews Polypropylene (PP), the second most widely produced thermoplastic material, having been produced for over 60 years. Its synthesis, processing and application are still accompanied by vigorous R&D developments because the properties of PP are at the borderline between those of commodity and engineering thermoplastics. Readers are introduced to various tacticities and polymorphs of PP, and their effects on structural properties. Further, the book addresses the control of optical properties using nucleants, provides strategies for overcoming the limited cold/impact resistance of PP, examines in detail the effects of recycling, and presents guidelines for the property modification of PPs through foaming, filling and reinforcing with respect to target applications. Special attention is paid to descriptions and models of properties as a function of morphological variables. Last but not least, the book suggests potential practical applications of PP-based systems, especially in the packaging, appliances, building/construction, textile and automotive sectors. Each chapter, written by internationally respected scientists, reflects the current state-of-art in the respective field and offers a vital source of information for students, researchers and engineers interested in the morphology, properties, testing and modeling of PP and PP-based systems. The content is indispensable to the appropriate application of PPs and related composites.

Download or read book Effect of Condensable Materials During the Gas Phase Polymerization of Ethylene on Supported Catalysts written by Fabiana Nascimento de Andrade and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fluidized bed reactors (FBR) are the only commercially viable technology for the production of polyethylene in the gas phase since the polymerization is highly exothermic and the FBR is the only type of gas phase reactor that offers adequate possibilities of heat transfer. The highly exothermic nature of this polymerization effectively poses many problems for gas phase operation and can limit the production of a certain process. However, in recent years the fluidized bed processes have been improved with new technologies. In particular, the addition of inert (usually liquefied) hydrocarbons allows one to increase the amount of heat removed from the reactor. These compounds increase the heat capacity of the gas phase and, if injected in liquid form, also evaporate and thus absorb even more heat from the reaction medium efficiently. This is known as a condensed mode operation. In it, one uses compounds that can be liquefied in the recycle condenser, and which are called Induced Condensing Agents (ICA). The use of ICA is extremely important from an industrial point of view. The injection of ICA can have many different physical effects at the level of the growing polymer particles. For instance, adding these compounds can cause changes in solubility and other physical properties, which can facilitate the transport of ethylene and hydrogen to the active sites of the catalysts. It is thus very important that the physical phenomena related to the sorption equilibrium of the monomer(s) and other species from the gas phase to the polymer phase, and their diffusion on the polymer matrix at the active sites should be accounted for. In addition to having an effect on the kinetics, these phenomena can also impact the structure of the polymer molecules and consequently qualify the characteristics of the polymer. Identifying the behavior of these phenomena under process conditions and control variables of the hydrogen/ethylene ratio and the comonomer/ethylene ratio with ICA are central objectives of this study. A series of ethylene homo- and co-polymerizations in the gas phase were carried out using a commercial Ziegler-Natta catalyst in the presence of ICA (propane, n-pentane, and n-hexane). We investigated the effect of temperatures, the partial pressure of ICA, hydrogen, and comonomers on the behavior of the polymerization. It was found that adding ICA significantly increased the reaction rate and average molecular weights at a given temperature. It was also unexpectedly observed that increasing the reactor temperature in the presence of an ICA actually led to a decrease in the overall reaction rate. These results were attributed to the socalled cosolubility effect. In reactions in the presence of different hydrogen concentrations, for an ICA/C2 ratio much larger than the H2/C2 ratio, the effect of ICA on ethylene solubility can counteract the decrease in average molecular weight caused by the presence of hydrogen. The impact of ICA on the rates of copolymerization reactions is more pronounced in the initial stages, losing strength due to the effect of the comonomer. Finally, an evaluation of the kinetics of crystallization under isothermal conditions for mixtures of different ICA:HDPE concentrations showed that the crystallization time is significantly higher for systems rich in ICA than for dry polymer.

Download or read book Nanostructured Catalysts written by Susannah L. Scott and published by Springer Science & Business Media. This book was released on 2008-04-06 with total page 341 pages. Available in PDF, EPUB and Kindle. Book excerpt: With the recent advent of nanotechnology, research and development in the area of nanostructured materials has gained unprecedented prominence. Novel materials with potentially exciting new applications are being discovered at a much higher rate than ever before. Innovative tools to fabricate, manipulate, characterize and evaluate such materials are being developed and expanded. To keep pace with this extremely rapid growth, it is necessary to take a breath from time to time, to critically assess the current knowledge and provide thoughts for future developments. This book represents one of these moments, as a number of prominent scientists in nanostructured materials join forces to provide insightful reviews of their areas of expertise, thus offering an overall picture of the state-- the art of the field. Nanostructured materials designate an increasing number of materials with designed shapes, surfaces, structures, pore systems, etc. Nanostructured materials with modified surfaces include those whose surfaces have been altered via such techniques as grafting and tethering of organic or organometallic species, or through various deposition procedures including electro, electroless and vapor deposition, or simple adsorption. These materials find important applications in catalysis, separation and environmental remediation. Materials with patterned surfaces, which are essential for the optoelectronics industry, constitute another important class of surface-modified nanostructured materials. Other materials are considered nanostructured because of their composition and internal organization.

Download or read book An Advanced Stopped flow Reactor for the Study of Olefin Polymerization written by Yashmin Rafante Blazzio and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Given the undeniable relevance of polyolefin production, it is of great interest to understand the keyphenomena determining the quality of the polymerization process. lndustrial scale polymerization reactions could be metaphorically compared to the launching of a space rocket, in which the success of the entire process is highly dependent on the mastery of the initial moments. This so-called 'nascent phase' of the polymerization (10-1 to 102 s) is crucial in ensuring a satisfactory operation and properties of the final polymer. lt is then that the catalyst activation takes place, the particle morphology is defined and the system is in its highest potential for mass transfer and heat transfer limitations.Studying such short time-frames is challenging for a number of reasons (that we will see throughout this work) and requires specially adapted tools. Previous works from our research group have shown how the stopped-flow technique is a promising method to study aspects related to heat transfer and morphology evolution at early stages in gas-phase. lt is mainly for this reason that the focus of the current project was on the improvement of such tools. The novel reactor developed in this work was especially designed to tackle some of the limitations encountered with the previous versions, mainly aspects related to poor heat evacuation, lack of robustness and imprecision in experimental measurements.The first part of this PhD describes all steps taken until successful optimization of the hardware component of the novel stopped-flow reactor. The new set-up was a product of our innovative approach towards the reactor geometry (annular) and the tailored execution from a specialized engineering firm. Several improvements were achieved, such as the optimization of the reactor dimensions, the automated control of all functions and a wider range of operation conditions. Moreover, the capacity was highly improved by the possibility of injecting several gases simultaneously, as well as components that are liquid at room temperature. The new tool allows to perform polymerization reactions as short as 3s in gas phase, in reaction conditions that are representative of heat and mass transfer phenomena present in industrial scales.ln the second part of this work, we have developed a software component for the novel reactor, which consisted of a reactor model and state-observer. This tool was developed to estimate the dynamic polymerization rates from the temperature measurements and overcome the one-point character of such experiments (which provide no real information on the catalyst kinetics). For this purpose, a simplified one-dimensional model at the macromolecular level was developed and validated with experimental data.At last, with hardware and software components at hand, we have demonstrated the usefulness of the new tool in specific case studies with different silica supported metallocene catalysts. ln the first case study, we evaluated the impact of the pore structure of the support on the catalyst kinetics, polymer properties and particle morphology at short reaction times. On the second case study, we investigated the effect of various experimental conditions (reaction time, comonomer and hydrogen content) on the behavior of two different catalyst families. From both studies, the estimated reaction rates at early stages (

Download or read book Comprehensive Inorganic Chemistry II written by and published by Newnes. This book was released on 2013-07-23 with total page 7694 pages. Available in PDF, EPUB and Kindle. Book excerpt: Comprehensive Inorganic Chemistry II, Nine Volume Set reviews and examines topics of relevance to today’s inorganic chemists. Covering more interdisciplinary and high impact areas, Comprehensive Inorganic Chemistry II includes biological inorganic chemistry, solid state chemistry, materials chemistry, and nanoscience. The work is designed to follow on, with a different viewpoint and format, from our 1973 work, Comprehensive Inorganic Chemistry, edited by Bailar, Emeléus, Nyholm, and Trotman-Dickenson, which has received over 2,000 citations. The new work will also complement other recent Elsevier works in this area, Comprehensive Coordination Chemistry and Comprehensive Organometallic Chemistry, to form a trio of works covering the whole of modern inorganic chemistry. Chapters are designed to provide a valuable, long-standing scientific resource for both advanced students new to an area and researchers who need further background or answers to a particular problem on the elements, their compounds, or applications. Chapters are written by teams of leading experts, under the guidance of the Volume Editors and the Editors-in-Chief. The articles are written at a level that allows undergraduate students to understand the material, while providing active researchers with a ready reference resource for information in the field. The chapters will not provide basic data on the elements, which is available from many sources (and the original work), but instead concentrate on applications of the elements and their compounds. Provides a comprehensive review which serves to put many advances in perspective and allows the reader to make connections to related fields, such as: biological inorganic chemistry, materials chemistry, solid state chemistry and nanoscience Inorganic chemistry is rapidly developing, which brings about the need for a reference resource such as this that summarise recent developments and simultaneously provide background information Forms the new definitive source for researchers interested in elements and their applications; completely replacing the highly cited first edition, which published in 1973

Download or read book Alkene Polymerization Reactions with Transition Metal Catalysts written by Yury Kissin and published by Elsevier. This book was released on 2008-03-10 with total page 495 pages. Available in PDF, EPUB and Kindle. Book excerpt: During the past 30 years, the field of alkene polymerization over transition metal catalysts underwent several major changes: 1. The list of commercial heterogeneous Ziegler-Natta catalysts for the synthesis of polyethylene and stereoregular polyolefins was completely renewed affording an unprecedented degree of control over the polymer structure. 2. Research devoted to metallocene and other soluble transition-metal catalysis has vastly expanded and has shifted toward complexes of transition metals with multidentate ligands. 3. Recent developments in gel permeation chromatography, temperature-rising fractionation, and crystallization fractionation provided the first reliable information about differences between various active centers in transition-metal catalysts. 4. A rapid development of high-resolution 13C NMR spectroscopy resulted in greatly expanded understanding of the chemical and steric features of polyolefins and alkene copolymers. These developments require a new review of all aspects of alkene polymerization reactions with transition-metal catalysts. The first chapter in the book is an introductory text for researchers who are entering the field. It describes the basic principles of polymerization reactions with transition-metal catalysts, the types of catalysts, and commercially manufactured polyolefins. The next chapter addresses the principal issue of alkene polymerization catalysis: the existence of catalyst systems with single and multiple types of active centers. The subsequent chapters are devoted to chemistry and stereochemistry of elemental reaction steps, structures of catalyst precursors and reactions leading to the formation of active centers, kinetics of polymerization reactions, and their mechanisms. The book describes the latest commercial polymerization catalysts for the synthesis of polyethylenes and polypropylene The book provides a detailed description of the multi-center nature of commercial Ziegler-Natta catalysts. The book devotes specialized chapters to the most important aspects of transition metal polymerization catalysts: the reactions leading to the formation of active centers, the chemistry and stereochemistry of elemental polymerization steps, reaction kinetics, and the polymerization mechanism. The book contains an introductory chapter for researchers who are entering the field of polymerization catalysis. It describes the basic principles of polymerization reactions with transition-metal catalysts and the types of commercially manufactured polyolefins and copolymers The book contains over 2000 references, the most recent up to end of 2006.

Download or read book Impact of Physical Properties of Silica on the Reaction Kinetics of Silica Supported Metallocenes and Polyethylene Morphology written by Muhammad Ahsan Bashir and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polyolefins account for more than half of the world's plastic production and about 80% of these polyolefins are commercially produced with heterogeneous olefin polymerization catalysts such as Phillips, Ziegler-Natta and metallocenes. Trouble-free plant operation due to low fouling of the reactor or other plant equipment, relatively stable catalytic activity, good polymer morphology and high polymer bulk densities can be achieved by employing heterogeneous olefin polymerization catalysts. On the other hand, heterogenization of the olefin polymerization catalysts lead to drastic reduction in their activities and broadening of the polymer molar mass distribution which is undesirable in some cases because it can influence the processability and mechanical properties of the polyolefin grade. Various explanations have been proposed in the open literature to explain these effects of catalyst immobilization which mainly include existence of diffusion resistance to (co)-monomer(s) transport at the active sites during polymerization and the change of the active site(s) behavior due to immobilization leading to multiple site types on the final supported catalyst. Nevertheless, both of these explanations have a connection with the physical properties (e.g., particle size, surface area, pore volume, pore diameter etc.) of the support because the support can impact the nature of the final active species formed on it, dispersion of the active species throughout the support particles and, last but not the least, the intraparticle diffusion of (co)-monomer(s) during polymerization. Metallocenes are considered as single-site catalysts and any changes in the nature of the active site(s) upon their immobilization on a support or during the course of polymerization due to mass transfer resistance can be detected from the broadening of polyolefin molar mass distribution. Therefore, the present work is an attempt to study the effects of physical properties of silica supported metallocenes on their ethylene polymerization kinetics as well as on the morphology of the produced polyethylene. For this purpose, the surface chemistry of the used commercial silica supports was fixed by dehyroxylating all of them at 600 °C, whereas, the final metal loadings of the supported catalysts were nearly kept constant by preparing them under identical conditions. Furthermore, slurry and gas phase polymerization protocols along with the used aluminum alkyl scavenger (which can also induce chemical effects on the catalytic behavior of supported metallocenes) were also fixed by testing different polymerization protocols and scavengers. Such systematic study has allowed us to attribute the observed differences in the reaction kinetics of the supported metallocenes, explicitly, to the differences in the physical parameters of the silica supports and, consequently, to the existence of diffusion resistance to (co) monomer(s) transport at the active site(s) during the course of polymerization.

Download or read book Catalytic Olefin Polymerization written by T. Keii and published by Elsevier. This book was released on 1990-09-12 with total page 573 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent development of a new generation of Ziegler-Natta Catalysts using either magnesium dichloride as carrier or methylaluminoxane as cocatalyst has markedly stimulated the research activity in the field of olefin polymerization. These discoveries have not only yielded economical processes for polyolefin production but also opened the way to a new generation of novel polymers. Moreover, the nature of active species is being clarified well by the effort to simplify catalyst systems. The present volume includes 38 papers from the 31 lectures and 18 posters presented at the symposium on `Recent Developments in Olefin Polymerization Catalysts', which covered the following topics: Overview of super-active homogeneous and heterogeneous catalysts, kinetic profile of olefin polymerization including copolymerization, characterization of catalysts and polymers, methods for the determination of active center concentration, role of Lewis bases on the catalysts isospecificity, polymerization mechanisms, and synthetic pathways for functionalized polyolefins. The contents are well balanced between fundamental research and application as well as between homogeneous and heterogeneous catalyst systems.

Download or read book Supported Aqueous phase Catalysis for Atom Transfer Radical Polymerization written by Ravi Aggarwal and published by . This book was released on 2010 with total page 276 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atom transfer radical polymerization (ATRP) which utilizes transition metal based catalysts is a versatile methodology for the synthesis of a wide spectrum of polymers with controlled architectures. However, high concentrations of soluble catalyst required in an ATRP process makes the final polymer colored and toxic. Thus, the catalyst removal/reduction/recycling remains a challenge in the field of ATRP. Supported catalysts on insoluble solids such as silica gel, polystyrene beads, etc. have been used in ATRP to facilitate the catalyst recovery and recycling. However, the ability of the supported catalysts to mediate a polymerization is substantially reduced due to their reduced mobility and leaching problems. In this thesis, we report a series of novel and recyclable physisorbed CuBr2/N, N, N', N'' -pentamethyldiethylene-triamine supported catalytic systems operating in conjunction with hydration. Supported aqueous-phase catalysis (SAPC) for ATRP was evaluated for different inorganic (Na-clay, silica and zeolite) and organic (polysaccharides) supports. The hydrated physisorbed supported catalysts were used for the polymerization of benzyl methacrylate and methyl methacrylate using an activator generated electron transfer ATRP process. The catalyst was effectively retained on the surface of supports through hydration as was verified by UV-Vis measurements. The supported catalyst was easily removed from the polymerization by simple filtration process affording a colorless polymer solution. The polymerizations produced high conversion and colorless polymers with moderately narrow polydispersity indices (PDI). The catalyst maintained high activity during the recycling experiments. We also investigated the kinetic and mechanistic behavior of these solid supported polymerization systems. Based on split kinetics experiments and UV-Vis studies it was believed that the activation and deactivation processes took place at the diffused hydrated interface between the solid support and organic phase. The branched (stars and graft) polymers were also synthesized using Na-clay supported catalyst. The produced polymers had narrow PDI and good initiator efficiencies. The functionality of the star polymers was confirmed using 1H NMR and dilute solution properties. The synthesis of graft-copolymer was confirmed by 1H NMR and atomic force microscopy. This thesis demonstrates the successful use of SAPC for ATRP to produce contamination free linear and branched polymers with moderately narrow PDI and high recycling efficiency.

Download or read book Controlled Radical Polymerization written by and published by . This book was released on 2015 with total page 428 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reversible deactivation radical polymerization (RDRP), also known as controlled radical polymerization (CRP), has been a significant area of polymer research for more than 20 years, allowing the facile synthesis of complex macromolecules previously unattainable by conventional free radical polymerization (FRP). However, industrial adoption of RDRP has been minimal largely due to the significant economic barrier to commercialization, with complex synthesis of the mediating agents required and the necessary post polymerization processing to recover the mediating agent. In an effort to overcome this obstacle to industrial adoption, the mediating agent concentration can be significantly reduced, such as the copper level in activator regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP), or the mediating agent can be incorporated into the polymer as in nitroxide-mediated polymerization (NMP), where no post polymerization processing is required other than removal of residual monomer. This thesis presents a study of these two chemistries towards industrially relevant conditions. To build upon recent developments of continuous ARGET ATRP, a systematic batch study is conducted to pursue decreased copper levels in the generation of short chain acrylic and methacrylic polymers of interest to the coatings industry. The limitations to reducing copper levels are understood with the development of a kinetic model, with the improved understanding of the ARGET ATRP system suggesting that a reduction in copper loading must be accompanied by an increase in reducing agent loading in order to maintain an appreciable polymerization rate. Alternatively, NMP does not require a reduction in mediating nitroxide level as it reversibly terminates the polymer chain end, and may present a smaller barrier to commercialization. Indeed, certain nitroxides are currently produced at pilot scale. However, limited research has been conducted into continuous operation which is commonly used in industry to improve productivity. A batch NMP study at elevated temperatures demonstrates the effectiveness of a novel alkoxyamine to mediate the polymerization of styrene and butyl acrylate under industrially relevant conditions. A kinetic study is developed to understand the novel system, and the polymerization is implemented in a continuous stirred-tank reactor (CSTR), the first demonstration of NMP in an existing industrial process.

Download or read book Index to Theses with Abstracts Accepted for Higher Degrees by the Universities of Great Britain and Ireland and the Council for National Academic Awards written by and published by . This book was released on 2005 with total page 364 pages. Available in PDF, EPUB and Kindle. Book excerpt: