Download or read book Synthesis of Chromium Guanidinate Complexes and Their Activity in Ethylene Oligomerization polymerization written by Steven Horvath and published by . This book was released on 2010 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis of Chromium Guanidinate Complexes and Their Activity in Ethylene Oligomerization polymerization written by Steven Horvath and published by . This book was released on 2010 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis Characterization and Catalytic Activity of Chromium Complexes written by Joanna Gurnham and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: There has been a growing demand for specific linear alpha olefins in the polyethylene industry in order to control polymer rheology. This growing demand thereby increases the need for highly active and selective ethylene oligomerization catalysts. Chromium-based catalysts continue to be of high interest for this application due to this metal's versatility in both selective and non selective ethylene oligomerization. Ligand design is an important consideration in oligomerization chemistry: the ability of the ligand to stabilize low valent chromium and to support a two-electron redox process will allow the catalytic systems to follow the selective ring expansion mechanism for oligomerization. Chelating aminophosphane based ligands, previously studied by our group, have been shown to support both tri- and tetramerization of ethylene. We have explored modifications of one of the NP arms by replacing with a different coordinating group in an attempt to further stabilize the monovalent state of chromium and increase selectivity. Other ligands explored in this work are pyrrole based ligands, which have shown high activity and selectivity towards ethylene oligomerization. One example of this is the commercial Chevron-Phillips system. Recently, the co-polymerization of CO2 with epoxides has been studied as an environmentally friendly route to convert CO2 into biodegradable polymers. The first successful catalytic system to achieve these results consisted of a diethyl-zinc complex. More recently, aluminum, chromium, cadmium and cobalt have been studied as polycarbonate catalysts. To date, the only reported chromium catalysts for CO2-epoxide copolymerization are Cr-salen and Cr-porphyrin complexes, studied by Darrensbourg and Holmes, respectively. We were particularly interested in finding new chromium-based complexes able to catalyze epoxide/CO2 copolymerization by using molecules with the nitrogen donor motif embedded in different functions such as neutral pyridines with anionic pendants, pyrroles with either imine or amine pendants, or a combination of these.

Download or read book Organometallic Reactions and Polymerization written by Kohtaro Osakada and published by Springer. This book was released on 2014-07-15 with total page 307 pages. Available in PDF, EPUB and Kindle. Book excerpt: This compilation provides advanced graduate students and researchers with a structured overview of olefin polymerization. Divided into eight chapters written by international experts, this book covers polymerization using various organotransition-metal catalysts, including early and late transition metal complexes, new trends in olefin oligomerization and related reactions. All authors address the historic and scientific backgrounds of the field as well as current research progress and potential for further research. The complete book is designed to present eight independent lectures and, because all authors are well versed in organometallic chemistry, each is based on a profound understanding of the reactions and structures of organotransition metal complexes. This book is an ideal accompaniment for researchers taking courses in olefin polymerization and also serves as a valuable resource for teachers and lecturers of chemistry when planning and researching material for advanced lecture courses.

Download or read book Synthesis of Transition Metal Complexes and Their Application for Ethylene Oligomerization and Polymerization written by Shaofeng Liu and published by . This book was released on 2011 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis of Chromium III Carboxylate Complexes and Their Use in Ziegler natta Polymerization written by Mougang Djanteng Soume Berline Beatrice and published by . This book was released on 2009 with total page 380 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis of New Transition Metal Complexes and Applications for the Catalytic Ethylene Oligomerization and or Polymerization written by Suyun Jie and published by . This book was released on 2008 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polyolefins represent about half the market of the synthesized polymeric materials. The catalytic oligomerization of ethylene is currently the primary source of linear [alpha]-olefins which are extensively used for the preparation of synthetic lubricants, detergent intermediates, surfactants, plasticizers and as comonomers to synthesize linear low-density polyethylene (LLDPE). This work deals with the synthesis of 2-imino-1,10-phenanthroline and 2-imino-9-phenyl-1,10-phenanthroline tridentate ligand and of their iron, cobalt and nickel complexes of which some are very active in the catalytic ethylene oligomerization. Stereoelectronic parameters influencing the catalytic properties have been examined in detail. Furthermore, mono- and dinuclear cobalt complexes with phosphino- and phosphinito-oxazoline ligands have been prepared in the course of this thesis. They have shown moderate catalytic activity in the presence of MAO or AlEtCl2 as cocatalyst.

Download or read book Synthesis of Chromium III Acetate and Chloroacetate Complexes and Their Application in Olefin Polymerization written by Saw Hong Tan and published by . This book was released on 2007 with total page 274 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Challenge of Selectivity in Ethylene Oligomerization written by Indira Thapa and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Bis pyrazolyl Chromium III Nickel II and Palladium II Complexes as Ethylene Oligomerization and Polymerization Catalysts written by Nangamso Alicia Miti and published by . This book was released on 2008 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Ethylene Polymerization Over Supported Organochromium Catalysts written by Shi-Liang Fu and published by . This book was released on 1990 with total page 434 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Organometallic Catalysis for Controlled Olefin Polymerization and Oligomerization written by Kyung-Sun Son and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: My Ph. D. work primarily involves the synthesis of ethylene-based oligomers and ethylene-styrene copolymers using organometallic catalysis. Chapter 1 reviews selective ethylene oligomerization that produces 1-hexene and 1-octene, with particular emphasis on the chromium-based catalytic systems and the mechanism by which they operate. Its application to the preparation of value-added chemicals is also covered. Chapter 2 and Chapter 3 present investigations on selective ethylene oligomerization with a Cr(PNP)Cl3/MAO catalyst system (PNP = Ph2PN(iPr)PPh2) in the presence of dialkyl zinc as an effective strategy for the co-generation of 1-octene and functionalized ethylene oligomers. Transmetallation with ZnMe2 during Cr-catalyzed ethylene tetramerization generated end-labeled 1-alkenes in Cn> 10 along with 1-octene, while that with ZnEt2 or ZnBu2 produced a mixture of end-labeled linear alkanes and 1-alkenes in Cn> 10 as well as 1-octene. Labeling studies with D2O provided a mechanistic test for metallacycle intermediates. Mechanistic proposals are presented to explain the formation of end-labeled products in the presence of various types of zinc alkyls. Chapter 4 and Chapter 5 examine a series of titanocenes [CpTiCl3, CpTiCl2TEMPO, CpNTiCl3, CpNTiCl2TEMPO, where Cp = C5H5, CpN = C5H4CH2CH2N(CH3)2, and TEMPO = 2,2,6,6-tetramethylpiperidine-N-oxyl] for styrene homopolymerization and ethylene-styrene (ES) copolymerization at 70 °C and 120 °C to determine the influence of the pendant amine group and the hydroxylaminato ligand on comonomer incorporation and distribution. Titanocenes bearing the pendant amine ligand were active for ES copolymerization, whereas complexes lacking the pendant group afforded only mixtures of homopolymers, revealing the critical role of the pendant amine donor on the copolymerization behavior. At 120 °C, the titanocene complexes with the amine group generated high molecular weight ES copolymers along with an atactic polystyrene (aPS) byproduct. The molecular weight of the ES copolymers produced by a coordination mechanism was found to coincide with that of the aPS produced by a radical polymerization mechanism. A method to separate these two components was developed by the addition of a catalytic chain-transfer agent, cobalt tetraphenylporphyrin, successfully decreasing the molecular weight of the radically-produced aPS and offering expedient separation of the ES copolymer from the aPS. Chapter 6 describes a series of new mono-, bi-, and trimetallic complexes based on the dinucleating ligand, N, N'-bis[2-(diphenylphosphino)phenyl] formamidine (PNNP), which provides two binding sites suitable for accommodating Pd, Ni, Co, Fe, and Cu. Definitive evidence for the structures of all complexes were given by X-ray crystal structures. The synthesis, characterization and crystal structure of each complex are discussed.

Download or read book Study of the Factors Affecting the Selectivity of Catalytic Ethylene Oligomerization written by Khalid Albahily and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the past decade, advances in ethylene oligomerization have witnessed explosive growth of interest from both commercial and academic standpoint, with chromium metal invariably being the metal of preference. A common feature in this literature was the extended long debate regarding the mechanism, metal oxidation states responsible for selectivity and the role of the ligand. This thesis work embarked on the isolation and characterization of new active intermediates called "single component catalysts" (or self activating) to address two important questions: (1) how the catalyst precursors re-arrange upon activation and (2) the real oxidation state of the activated species. Four different ligands systems have been examined for this purpose. The first part is a study on the NPIIIN ligand which can be described as a dynamic and non-spectator ligand. Upon aluminum alkyl activation, a series of single component chromium catalysts for selective ethylene oligomerization and polymerization have been isolated, fully characterized and tested. New selective single component chromium(I) catalysts have also been isolated and tested positively for ethylene trimerization. The second part includes a new series of chromium complexes based on the NPVN ligand. This ligands enabled to obtain the first polymer-free extremely active catalytic system. In both NPN ligand systems, a new activation pathway was discovered by using vinyl Grignard reagent [(CH2=CH)MgCl] as activator and/or reducing agent. The third part explores new modified pyrrole-chromium complexes which were found to be highly active and selective ethylene trimerization catalysts. This part was a continuation of previous work from our lab to complete the mechanistic picture of this highly successful pyrrole-chromium catalyst independently commercialized by Phillips-Chevron and Mitsubishi. Interestingly upon aluminum alkyl treatment, the first example of a Schrock-type chromium ethylidene complex has been isolated and characterized and found to be a potent catalyst for selective ethylene trimerization. Finally, the other ligands introduced in this thesis are new systems called pyridine-SNS and Si-SNS that introduce some modification to the known commercial SNS catalyst (Sasol technology). The introduction of a pyridine ring or a silyl unit in the ligand scaffold has allowed to understand the mechanism of action of this remarkable system.

Download or read book Towards Selective Ethylene Tetramerization written by Yacoob Shaikh and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: There is an increasing trend towards advancing the understanding and development of ethylene oligomerization catalysts, both in academia and industry. The metal of choice in this chemistry is invariably chromium, which has shown great versatility in selective trimerization/tetramerization, non-selective oligomerization and polymerization of ethylene. While much success has been achieved in ethylene trimerization, the same con not be said about tetramerization catalysis. Aminophosphine based ligands have demonstrated their ability towards selective 1-octene production, however, the popular PNP catalyst is able to achieve only 70% selectivity. In order to explore the possibility of developing and enhancing the selectivity of chromium based ethylene tetramerization catalyst, this thesis work was undertaken. The ligand systems we chose for our work were bidentate aminophosphine based (PN(CH2)nNP), which has yielded interesting selective oligomerization. Subtle modifications were found to result in drastic changes in selectivity, from tetramerization (PN(CH2)3NP) to trimerization (PN(CH2)2NP). We managed to successfully develop the first truly selective (over 90%) 1-octene catalyst with polymer-free behavior. Further modifications on the ligand framework, where one atom of Si was used to link the two NP units, resulted in non-selective oligomerization, in which case we determined that the oxidation-state of chromium is a key player. We explored other modifications on our selective ligands in which one of the arms on the bidentate ligand was replaced with a base-donor amine, phosphine or pyridine, and resulted in interesting selectivity changes. The final modification that we tested was a novel N(CH2)2P ligand and found it to be a highly active, non-selective oligomerization catalyst.

Download or read book Amine bis phenolate Complexes of Chromium for Carbon Dioxide cyclohexene Oxide Copolymerization and Group I and II Complexes for the Ring Opening Polymerization of Rac lactide written by Katalin Devaine-Pressing and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Finding novel methods for polymer synthesis has been of particular interest as of late from both a chemical and commercial standpoint. This focus stems from the recognized need for biodegradable and biocompatible polymers, originating from renewable resources, and is a legitimate endeavor by society to ease the burden imposed on the environment. Society's conscience also recognizes the great need to utilize the carbon dioxide that is released in the atmosphere and it continues to make noble efforts in order not to contribute further to the greenhouse effect caused by greenhouse gases such as carbon dioxide. Therefore, the use of carbon dioxide as a starting material and the incorporation of it in the product of a chemical synthesis are currently developing research areas. Accordingly, combining the aim of environmentally friendly polycarbonate synthesis with incorporation of carbon dioxide in the polymer chain was the goal of the research conducted in the first part of this thesis. Additionally, biodegradable and biocompatible polylactide from lactide, originating from renewable feedstocks, was produced by biocompatible complexes in the second part. Polycarbonate synthesis was carried out in the presence of novel chromium(III) catalysts which were synthesized via salt metathesis reactions from tetradentate tripodal amine-bis(phenol) ligands. The complexes were characterized by MALDI-TOF mass spectrometry, UV-Vis and IR spectroscopy, magnetic susceptibility measurement and elemental analysis. The catalyst precursors selectively produced polycarbonates from epoxides and carbon dioxide with high yields and moderate molecular weights. Mechanistic studies revealed a first order dependence on catalyst concentration and that ring opening of the epoxide was initiated by a nucleophilic species originating either from the complex or from an externally added nucleophile. Biocompatible magnesium-, lithium-, sodium-, potassium- and calcium complexes of an amino-bis(phenolato) ligand were also prepared and characterized for the synthesis of polylactide, a biodegradable and biocompatible polymer. The magnesium and the sodium complexes in particular showed high catalytic activity and good control over the reaction. The complexes were active even under relatively low catalyst loading (0.1 - 0.2 mol%) and produced polymers of high purity as revealed by NMR, DSC and TGA.

Download or read book Oligomerization and Polymerization of Ethylene by Phenoxy imine Titanium Catalysts written by Astrid Cordier and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: 1-hexene is one of the most important olefin used as comonomer for the production of value-added polyethylenes (HDPE, LLDPE). In the field of selective ethylene trimerization employing titanium-based catalysts, specific single tridentate phenoxy-imine complexes (SFI) display the highest activity and 1-hexene selectivity upon activation with methylaluminoxane (MAO). However, ethylene polymerization is an unavoidable side reaction affecting both 1-hexene selectivity and process operations. Although being a major drawback, the causes of polymerization remain a grey area since few studies were dedicated to its deciphering. To handle this challenge , an original “polymer-to-catalyst” strategy was implemented. An extensive temperature study (26-80°C) revealed that the highest 1-hexene activity is reached between 30 °C and 40 °C while polymer production is prominent above 50 °C. Polyethylenes obtained were analyzed by SEC, NMR DSC, and advanced segregation techniques (CEF, SIST, rheology). Molar masses above 10^5 g mol-1 were identified along with a 1-hexene content below 1 mol %. An increase of dispersity (Ɖ > 2) with temperature was ascribed to an evolution from single to multi-site polymerization catalysis. Kinetic studies proved that polymer is continuously produced even at short reaction time, for any reaction temperature. Other parameters (addition of 1-hexene, hydrogen and use of trimethylaluminum) were found to impair the trimerization selectivity and/or activity of the system. Nevertheless, it was possible to lower the selectivity in polyethylene by premixing the complex with MAO. After analyzing the possible routes for the polymerization catalyst formation, the hypotheses of temperature and MAO-induced complex alterations were considered. Regarding the latter, a molecular ligand-free Ziegler-Natta catalyst, modeled using TiCl4/MAO, and the synthesized (FI)Ti(III)Cl2 activated by MAO could not explain polymer production in the SFI system. Formation of a polymerization species upon thermal alteration of the SFI complex was evidenced. This [O-,N,O-]-type species displays common features regarding catalytic response to 1-hexene compared to the polymerization catalyst in the SFI system although it could not reach the same catalytic performances. The formation of a bis(phenoxy-imine) complex (FI)2TiCl2 was evidenced in this thesis and is a promising avenue worth exploring. Eventually, although the exact species has not yet been identified, this work enabled to guide the focus of further investigations on activation process and complex rearrangement by ligand mobility.

Download or read book Design Synthesis and Characterization of New Ligands and Activators for the Oligomerization of Ethylene by Iron Complexes written by Adrien Boudier and published by . This book was released on 2012 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis describes the development of new catalytic systems based upon iron complexes and their reactivity toward ethylene. First, we focused our interest on the synthesis of iron(III) precursors chelated by monoanionic ligand. Those complexes were obtained either by reaction of the monoanionic ligand with FeCl3 or through oxidation of the iron(II) complex. The second reaction led to binuclear complexes. Then, another aim of the thesis was to design new well-defined cocatalysts for the activation of iron complexes. The study of the reaction between an alcohol and the trimethylaluminum allowed us to reach this aim. Aluminum complexes adopted either a binuclear framework or a trinuclear one, depending on the nature of alcohol reagent. Besides this work, new iron(II) and nickel(II) complexes chelated by imino-imidazole ligands bearing a pendant donor function L were synthesized. All complexes have been evaluated for the oligomerization of ethylene in the presence of EtAlCl2 or MAO as cocatalyst. Only nickel complexes were active toward ethylene transformation.