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 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 The Selective Oligomerization of Ethylene with Metal organic Frameworks written by Eric Daniel Metzger and published by . This book was released on 2018 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: The benefits of heterogeneous catalysis for industry and the society at large cannot be overstated, with approximately 90% of all industrial catalysis being performed with heterogeneous catalysts. Despite the undeniable operational advantages of heterogeneous catalysts, several large volume industrial processes involved in the production of commodity chemicals remain impenetrable to solid catalysts. Among them are the selective dimerization of ethylene and the selective trimerization of ethylene, which require fine steric and electronic tuning to optimize the production of the desired olefin. In this thesis, I describe the development of new heterogeneous catalysts to address the lack of activity and selectivity found among heterogeneous catalysts for selective ethylene oligomerizations, with an emphasis on developing new metal-organic framework (MOF) catalysts for the selective dimerization of ethylene to 1-butene. The ability to tune the catalytically active site of a solid at the molecular level places MOFs in prime position to answer challenges in heterogeneous catalysis that no other class of solids has been able to address. Chapter 2 of this thesis describes the development of Ni-MFU-4/, a nickel-substituted MOF with excellent activity and selectivity for the dimerization of ethylene to 1-butene. Although the active sites in the MOF are designed to mimic homogeneous Nitrispyrazolylborate dimerization catalysts, the selectivity observed for the solid catalyst is considerably higher than that of the homogeneous system, highlighting the importance of active site isolation in the porous solid. Chapter 3 details a combination of studies utilizing isotopic labeling and mechanistic probes to demonstrate that Ni-MFU-4/ dimerizes ethylene via the Cossee-Arlman mechanism. Chapter 4 reports the preparation of Ni-CFA-1, a related heterogeneous ethylene dimerization catalyst that is far more synthetically accessible than Ni- MFU-4/. Lastly, chapter 5 relays initial results towards the development of MOF-based ethylene trimerization catalysts.

Download or read book Computational Design and Analysis of Molecular Ethylene Oligomerization Catalysts written by Doo Hyun Kwon and published by . This book was released on 2019 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt: Linear alpha olefins (LAOs) are key petrochemical precursors for the synthesis of larger polymers, detergents, plasticizers, and lubricants. Most catalytic ethylene oligomerization processes generate a wide distribution of LAO carbon chain lengths. A major ongoing industrial challenge is to develop homogeneous catalysts that result in selective and tunable ethylene oligomerization to 1-hexene and 1-octene alkenes. Quantum mechanical calculations coupled with rapidly advancing technology have enabled the ability to calculate small molecule systems with high accuracy. Employing computational models to advance from empirical to quantitative prediction of product selectivities has become an active area of exploration. In this work, we demonstrate the development and use of a density-functional theory (DFT) transition-state model that provides highly accurate quantitative prediction of phosphinoamidine (P,N) Cr catalysts for controllable selective ethylene trimerization and tetramerization. This model identified a new family of highly selective catalysts that through computational-based ligand design results in a predictable shift from 1-hexene selectivity to 1-octene. Subsequent experimental ligand synthesis and catalyst testing verified the quantitative computational predictions. DFT calculations also provide key insights to factors controlling catalytic activity and present important design criteria for the development of active Cr-based ethylene oligomerization systems. Non-selective ethylene transformations, referred to as full range processes, provide access to a range of LAOs (C4-C20) that are used to produce polyethylene, surfactants, and other commercial products. During full-range oligomerizations, undesired byproducts degrade the purity of LAOs mostly consisting of branched oligomers. Computational mechanistic investigations reveal the origin of linear versus branched selectivity in Fe-catalyzed ethylene oligomerization reactions.

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 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 Kinetic Studies of Selective Ethylene Oligomerization Processes of Chromium Based Catalyst Systems written by Anina Tonia Wöhl and published by . This book was released on 2009 with total page 111 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Selective Oligomerization of Ethylene Using Chromium Diphosphine Catalysts and the Synthesis and Reactivity of Group 7 Carbonyl Derivatives Relevant to Synthesis Gas Conversion written by Paul Richard Elowe and published by . This book was released on 2009 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book 27th European Symposium on Computer Aided Process Engineering written by and published by Elsevier. This book was released on 2017-09-21 with total page 3064 pages. Available in PDF, EPUB and Kindle. Book excerpt: 27th European Symposium on Computer Aided Process Engineering, Volume 40 contains the papers presented at the 27th European Society of Computer-Aided Process Engineering (ESCAPE) event held in Barcelona, October 1-5, 2017. It is a valuable resource for chemical engineers, chemical process engineers, researchers in industry and academia, students, and consultants for chemical industries. Presents findings and discussions from the 27th European Society of Computer-Aided Process Engineering (ESCAPE) event

Download or read book Development of Tantalum Phenoxy imine Compounds for Selective Ethylene Oligomerization written by Iva Rreza and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Zeolites and Related Materials Trends Targets and Challenges SET written by Antoine Gedeon and published by Elsevier. This book was released on 2008-08-19 with total page 1423 pages. Available in PDF, EPUB and Kindle. Book excerpt: The present book "Zeolites and Related Materials: Trends, Targets and Challenges" reports the communications that have been presented at the 4th International FEZA (Federation of European Zeolite Associations) Conference in Paris, September 3-6, 2008. It gives an excellent overview of the present state of the art of ordered nanoporous solids including zeolites as well as synthetic layered materials (clays), nanosized molecular sieves, ordered mesoporous solids, metal-organic-framework compounds (MOFs), carbons, etc. with emphasis on the synthesis, comprehensive characterization and advanced applications. The significant research activities in this domain are due to the outstanding properties of those nanoporous materials that concentrate the collaborative efforts of researchers from material science, chemistry, physical chemistry and physics.The understanding and development of the unique properties of porous materials relies on a unique blend of multidisciplinary knowledge covering material science, with the implication of organic and colloid chemistry, to prepare micro- and mesoporous materials; surface and adsorption sciences sustained by theory and modelling to understand the peculiar behaviour of molecules in confined systems; special branches of catalysis, physics, chemical engineering and life science to design novel applications. This book summarizes the developments in the area of nanoporous solids at the dawn of the 21st century, useful for both students/young researchers entering the field of nanoporous materials, as well as for senior scientists Also summarizes the new family of porous compounds, e.g. MOF's and ordered porous carbon The present state-of-the-art and prospects of nanoporous solids for advanced applications is discussed

Download or read book The Role of Aluminate in the Activation of Catalytic Systems for Ethylene Oligomerization written by Ahmed Alzamly and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The reaction mechanisms followed by ethylene polymerization and selective oligomerization (tri- and tetramerization) are conceptually very different, being a non-redox chain growth and a redox metallacycle ring expansion pathway respectively. With chromium being the metal of choice, metal oxidation states and the variation of ancillary ligand able to support specific metal oxidation states responsible for selective trimerization, tetramerization or nonselective oligomerization/polymerization were varied. In this research project we have explored a broad range of novel pyridine containing modified PN ligand scaffolds with the aim of probing the role of the pyridine donor substituent in stabilizing lower oxidation states and ultimately affecting the selectivity of the ethylene in the catalytic cycle. In this study, pyridine PNP pincer ligands in conjunction with chromium salts and alkylaluminium activators have been explored. Their catalytic activities toward ethylene oligomerization were rationalized through the isolation of different chromium-aluminate intermediates in different oxidation states during the catalytic reaction. Moreover, we explored other pyridine modification of NNP type ligand. Its anionic ligand shows a rare example of a Cr(II) hydride cluster which shows a high activity as a nonselective ethylene oligomerization catalyst. Finally, a cyclic PNPN type ligand was explored. The ligand enabled the isolation of a mix-valent Cr(I)/Cr(II) species which was found to be inactive toward ethylene oligomerization due to its geometric constraint.

Download or read book Oligomerization of Chemical and Biological Compounds written by Claire Lesieur and published by BoD – Books on Demand. This book was released on 2014-06-18 with total page 454 pages. Available in PDF, EPUB and Kindle. Book excerpt: Many thanks to the authors for high quality chapters and to the referees for helping improve the manuscripts. The book is interdisciplinary, it covers fields from organic chemistry to mathematics, and raises different aspects of oligomerization. It is a great source of information as every chapter introduces general knowledge and deep details. Mixing communities is to instigate novel ideas and hopefully help looking at oligomerization with new eyes.

Download or read book Catalysis for Clean Energy and Environmental Sustainability written by K. K. Pant and published by Springer Nature. This book was released on 2021-05-13 with total page 933 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is part of a two-volume work that offers a unique blend of information on realistic evaluations of catalyst-based synthesis processes using green chemistry principles and the environmental sustainability applications of such processes for biomass conversion, refining, and petrochemical production. The volumes provide a comprehensive resource of state-of-the-art technologies and green chemistry methodologies from researchers, academics, and chemical and manufacturing industrial scientists. The work will be of interest to professors, researchers, and practitioners in clean energy catalysis, green chemistry, chemical engineering and manufacturing, and environmental sustainability. This volume focuses on the potentials, recent advances, and future prospects of catalysis for biomass conversion and value-added chemicals production via green catalytic routes. Readers are presented with a mechanistic framework assessing the development of product selective catalytic processes for biomass and biomass-derived feedstock conversion. The book offers a unique combination of contributions from experts working on both lab-scale and industrial catalytic processes and provides insight into the use of various catalytic materials (e.g., mineral acids, heteropolyacid, metal catalysts, zeolites, metal oxides) for clean energy production and environmental sustainability.

Download or read book Iron and Cobalt Catalysts written by Wilson D. Shafer and published by MDPI. This book was released on 2020-06-23 with total page 414 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the turn of the last century when the field of catalysis was born, iron and cobalt have been key players in numerous catalysis processes. These metals, due to their ability to activate CO and CH, haev a major economic impact worldwide. Several industrial processes and synthetic routes use these metals: biomass-to-liquids (BTL), coal-to-liquids (CTL), natural gas-to-liquids (GTL), water-gas-shift, alcohol synthesis, alcohol steam reforming, polymerization processes, cross-coupling reactions, and photocatalyst activated reactions. A vast number of materials are produced from these processes, including oil, lubricants, waxes, diesel and jet fuels, hydrogen (e.g., fuel cell applications), gasoline, rubbers, plastics, alcohols, pharmaceuticals, agrochemicals, feed-stock chemicals, and other alternative materials. However, given the true complexities of the variables involved in these processes, many key mechanistic issues are still not fully defined or understood. This Special Issue of Catalysis will be a collaborative effort to combine current catalysis research on these metals from experimental and theoretical perspectives on both heterogeneous and homogeneous catalysts. We welcome contributions from the catalysis community on catalyst characterization, kinetics, reaction mechanism, reactor development, theoretical modeling, and surface science.

Download or read book Catalytic and Process Study of the Selective Hydrogenation of Acetylene and 1 3 Butadiene written by Ruijun Hou and published by Springer. This book was released on 2017-01-05 with total page 151 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis offers novel methods for catalyst and process design for the selective hydrogenation of acetylene and 1,3-butadiene. The author predicts the properties of supported Pd–Ni bimetallic catalysts using density functional theory (DFT) calculations and temperature-programmed desorption (TPD). The excellent correlation between model surfaces and supported catalysts demonstrates the feasibility of designing effective bimetallic catalysts for selective hydrogenation reactions. The author also proposes a method for designing non-precious metal catalysts to replace precious metals. She modifies the process of selective hydrogenation of acetylene by coupling the selective adsorption to the selective hydrogenation in the liquid phase, as a result of which the ethylene selectivity is greatly improved and heat transfer is greatly enhanced. Lastly, by analyzing the mechanism of liquid-phase hydrogenation, the author proposes a multi-stage slurry bed reactor for industrial applications.“/p>

Download or read book Sustainable Strategies for the Upgrading of Natural Gas Fundamentals Challenges and Opportunities written by E.G. Derouane and published by Springer Science & Business Media. This book was released on 2006-06-15 with total page 433 pages. Available in PDF, EPUB and Kindle. Book excerpt: Energy and feedstock materials for the chemical industry are in increasing demand and, with constraints related to the availability and use of oil, the energy and chemical industry is undergoing considerable changes. In recent years, major restructuring has occurred in the oil, petrochemical, and chemical industry, with increasing attention devoted to the use of natural gas, methane in particular, as a chemical feedstock rather than just as a fuel. The conversion of remote natural gas into liquid fuels or other transportable chemicals is a challenge to industrial catalysis. Few processes exist so far with the major ones involving the conversion of natural gas to synthesis gas by steam reforming, CO2 reforming, or partial oxidation, followed by the syntheses of methanol, hydrocarbons (Fischer-Tropsch synthesis), or ammonia. In this book, a comprehensive overview of the field of processing natural gas is given, through a series of chapters written by leading scientists and engineers in the field. New developments are discussed and current work relevant to the area is shown by a series of recent works by researchers working in this and related fields.