[PDF] Development Of Molecular Transition Metal Catalysts For The Reverse Water Gas Shift Reaction And The Selective Transformation Of Carbon Dioxide And Hydrogen To Formic Acid Esters And Methanol eBook

Author : Christopher Panaritis
Publisher :
Page : pages
File Size : 35,14 MB
Release : 2021
Category :
ISBN :

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The continued release of fossil-fuel derived carbon dioxide (CO2) emissions into our atmosphere led humanity into a climate and ecological crisis. Converting CO2 into valuable chemicals and fuels will replace and diminish the need for fossil fuel-derived products. Through the use of a catalyst, CO2 can be transformed into a commodity chemical by the reverse water gas shift (RWGS) reaction, where CO2 reacts with renewable hydrogen (H2) to form carbon monoxide (CO). CO then acts as the source molecule in the Fischer-Tropsch (FT) synthesis to form a range of hydrocarbons to manufacture chemicals and fuels. While the FT synthesis is a mature process, the conversion of CO2 into CO has yet to be made commercially available due to the constraints associated with high reaction temperature and catalytic stability. Noble metal ruthenium (Ru) has been widely used for the RWGS reaction due to its high catalytic activity, however, several constraints hinder its practical use, associated with its high cost and its susceptibility to deactivation. The doping or bimetallic use of non-noble metals iron (Fe) and cobalt (Co) is an attractive option to lower material cost and tailor the selectivity of the CO2 conversion towards the RWGS reaction without compromising catalytic activity. Furthermore, employing nanostructured catalysts as nanoparticles is a viable solution to further lower the amount of metal used and utilize the highly active surface area of the catalyst. Dispersing nanoparticles on ionically conductive supports/solid electrolytes which contain species like O2−, H+, Na+, and K+, provide an approach to further enhance the reaction. This phenomenon is referred to as metal-support interaction (MSI), allowing for the ions to back spillover from the support and onto the catalyst surface. An in-situ approach referred to as Non-Faradaic Modification of catalytic activity (NEMCA), also known as electrochemical promotion of catalysis (EPOC) is used to in-situ control the movement of ionic species from the solid electrolyte to and away from the catalyst. Both the MSI and EPOC phenomena have been shown to be functionally equivalent, meaning the ionic species act to alter the work function of the catalyst by forming an effective neutral double layer on the surface, which in turn alters the binding energy of the reactant and intermediate species to promote the reaction. The main objective of this work is to develop a catalyst that is highly active and selective to the RWGS reaction at low temperatures (

Author : L. Brandsma
Publisher : Springer Science & Business Media
Page : 349 pages
File Size : 39,59 MB
Release : 2012-12-06
Category : Science
ISBN : 3642603289

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Homogeneous catalysis is an important strategy for the synthesis of high-valued chemicals. L. Brandsma has carefully selected and checked the experimental procedures illustrating the catalytic use of copper, nickel, and palladium compounds in organic synthesis. All procedures are on a preparative scale, make economic use of solvents and catalysts, avoid toxic substances and have high yields.

Author :
Publisher : Elsevier
Page : 270 pages
File Size : 22,41 MB
Release : 2024-09-18
Category : Science
ISBN : 0443140049

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Earth-Abundant Transition Metal Catalyzed Reactions, Volume 74 in the Advances in Catalysis series, highlights new advances in the field, with this new volume presenting interesting chapters. Each chapter is written by an international board of authors. Chapters in this new release include in Chiral Iron Complexes for Asymmetric Catalysis, Recent advances in Ni-catalyzed Functionalization of Strong C-O and C-H Bonds, Low-valent Molecular Cobalt Complexes for Reductive Chemistry, Iron-catalyzed group-transfer reactions with hypervalent iodine reagents, and Iron Porphyrins for Mediating Atom Efficient C–C Bond Formations. Provides the authority and expertise of leading contributors from an international board of authors Presents the latest release in Advances in Catalysis serials Updated release includes the latest information in the field

Author : Jennifer Wood Eddy
Publisher :
Page : 230 pages
File Size : 42,55 MB
Release : 2017
Category :
ISBN : 9780355255737

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Formic acid has been proposed as a hydrogen storage medium; however, this necessitates efficient and selective catalysts for the dehydrogenation of formic acid to produce H2 and CO2. Consequently, we have developed palladium based complexes supported by chelating bis-N-heterocyclic carbene (NHC) ligands and probed the activity of such complexes for the dehydrogenation of formic acid. The formic acid dehydrogenation properties of [(MDCMes)Pd(MeCN)2](PF6)2 in MeCN with triethylamine additive were monitored using water displacement and gas chromatography to show a 1:1 ratio of CO2:H2 production with no detection of CO, and a modest turnover frequency (TOF, 325 h-1) and turnover number (TON, 185). The [(MDCMes)Pd(MeCN)2](PF6)2 catalyst was used under relatively mild conditions and is the first example of a homogenous palladium catalyst with any reasonable activity for formic acid dehydrogenation. The original catalyst motif was modified by changing either the NHC wingtip substituents or the coordinating ligands. This family of complexes was characterized by NMR spectroscopy, elemental analysis, and X-ray crystallography, and studied for formic acid dehydrogenation. The modified complexes were found to be less active than the parent catalyst. ☐ From these initial studies, a mechanism was proposed and probed using several kinetic studies, including Eyring and Arrhenius analyses. These studies supported the proposed mechanism and suggested that the opening of a coordination site on palladium for subsequent b-hydride elimination was the rate determining step of H2 liberation. Based on the proposed mechanism, the reaction system with [(MDCMes)Pd(MeCN)2](PF6)2 as catalyst was further optimized by changing the base from triethylamine to Hünig’s base. The initial TOF for the reaction with Hünig’s base was determined to be 414 h-1 and the total TON was increased to 353. Additionally, formic acid could be added up to 18 times with catalytic activity. ☐ The 4e–/4H+ reduction of oxygen to water is an important reaction that takes place at the cathode of fuel cells; therefore, catalysts that are selective for this reaction are highly desired. The calix[4]phyrin is a tetrapyrrole macrocycle that exhibits unique properties due to the incorporation of two sp3 hybridized meso carbons. We wished to explore these unique macrocycles and corresponding metal complexes with the goal of applications to catalysis, in particular the oxygen reduction reaction (ORR). The freebase calix[4]phyrin was synthesized by modifying a streamlined procedure for tetrapyrrole macrocycle synthesis previously utilized in our laboratory for the related phlorin macrocycle. The freebase calix[4]phyrin macrocycle was then metalated to give the corresponding zinc, copper, nickel and cobalt complexes. These metal complexes were characterized using a variety of methods, including X-ray crystallography, UV-vis spectroscopy, differential pulse voltammetry and cyclic voltammetry. ☐ The cobalt calix[4]phyrin was studied as a catalyst for the ORR, both heterogeneously and homogeneously. The homogeneous ORR was monitored using UV-vis spectroscopy, and cobalt calix[4]phyrin was found to catalyze the reduction of O2 to give approximately 50% water production (n = 3). A series of kinetic studies were also performed by varying the concentration of each species in solution, and from these studies a mechanism was proposed. The ORR with cobalt calix[4]phyrin was studied heterogeneously using rotating ring-disk electrode electrochemistry. By using Koutecky-Levich analysis, cobalt calix[4]phyrin was found to reduce O2 with 2.9 electron equivalents transferred under electrochemical conditions, which corresponds to ~50% water production. This selectivity for water production is promising for a monomeric cobalt complex. Initial attempts were made to further optimize the cobalt calix[4]phyrin using a hangman scaffold, however these modifications did not increase the selectivity as compared to the parent compound.

Author : Suyash Singh
Publisher :
Page : 0 pages
File Size : 45,29 MB
Release : 2014
Category :
ISBN :

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Over the past century, heterogeneous catalysis has played a central role in the development of efficient chemical processes for the conversion of fossil resources to fuels and chemicals, and identification of new, sustainable routes to upgrade renewable carbon sources that minimize the ecological footprint. More recently, unprecedented advances in electronic structure theory and related computational methods have provided a major thrust to the efforts that utilize density function theory (DFT) calculations for developing fundamental atomic-level understanding of these processes, and subsequently designing new and improved catalysts. In this dissertation, a combined theoretical and experimental approach is presented to study the reaction mechanisms for the catalytic conversion of formic acid (FA) and propylene oxide on transition metals. An iterative methodology comprising of DFT calculations, reaction kinetics measurements, and mean-field microkinetic modeling is employed to determine the nature of active sites on supported catalysts, explain the experimentally observed trends, and obtain predictions for the surface environment under reaction conditions. A detailed analysis of the DFT derived thermochemistry and kinetics parameters over a wide range of transition metal surfaces is performed to identify the key reactivity descriptors for FA decomposition on transition metal catalysts, and develop semi-empirical linear correlations that are then used to develop a microkinetic modeling based framework for the identification and design of improved (active and selective) bimetallic alloy catalysts. Finally, the possible utilization and applications of these methods and ideas in other key chemical transformations are proposed, and suggestions for future work are included.

Author : Chastity Li
Publisher :
Page : 0 pages
File Size : 21,48 MB
Release : 2023
Category :
ISBN :

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Renewable hydrocarbon liquid fuels are needed to displace fossil-based liquid fuels from hard to abate sectors such as aviation and heavy shipping. The most advanced existing renewable liquid fuel options rely on biomass pathways that are limited by photosynthetic efficiency and compete with food production for arable land. There is a critical need for scalable synthetic methods that produce liquid fuels from H2O and CO2 emissions. Existing synthetic pathways for liquid fuel generation start with syngas, a gas mixture containing H2 and CO, which can be converted to short chain alcohols via gas fermentation or to various length hydrocarbons through Fischer-Tropsch. There are various upscaling methods that can turn these products into fuels suitable for hard-to-abate sectors. However, syngas is currently produced from coal or natural gas via steam reforming. Reverse water-gas shift (RWGS), which thermochemically converts CO2 and H2 into CO and H2O, provides the critical link between renewable power and liquid fuels by generating syngas from CO2 and electrochemically derived H2. Current RWGS technologies use Ni-based catalysts that must be operated at very high (> 900 °C) temperatures to minimize the production of methane through the competing Sabatier reaction. Operating at these high temperatures requires specialized and expensive reactor materials and complicates heat integration with downstream syngas-to-liquids conversions. My work has developed transition metal-free, alkali carbonate-based RWGS catalysts for renewable liquid fuel generation at intermediate temperatures ≤750 °C. These catalysts consist of an alkali carbonate salt dispersed on a mesoporous support material. Because it lacks a transition metal, the catalyst has very little affinity for the RWGS product CO, which precludes its further reduction to methane. The catalysts were evaluated in a custom-built flow reactor suitable for operating at temperatures up to 525 °C and pressures up to 10 bar. Experimental results demonstrate high, equilibrium-limited conversion of CO2 to CO with nearly 100% selectivity. The catalysts were also stable in the presence of 50 ppm H2S impurity for more than 40 hours, which poisons typical transition metal-based catalysts. Based on these results, a larger set of dispersed carbonate catalysts were evaluated in high-throughput-experimentation over an expanded range of temperatures up to 750 °C and pressures up to 30 bar. The catalysts were stable over the course of 200+ hours of continuous operation at industrially relevant space velocities > 24,000 h−1. Stable catalyst performance in the presence of methane and propane was also demonstrated, which is important for integration with Fischer-Tropsch syngas-to-liquids processing because recycle-loops are expected to have significant short hydrocarbon content. Additional screening was used to explore broader catalyst loading and preparation techniques. Dispersed carbonate catalysts are highly active, selective, and low-cost RWGS catalysts. Their robust performance in the presence of common gas impurities makes them suitable for combination with downstream liquid fuel production pathways involving recycle loops. Catalyst preparation is very simple, and the scalable manufacture of these catalysts has been validated by industrial collaborators. This catalyst technology has the potential to simplify and accelerate the deployment of syngas-based renewable liquid fuel production to meet the ongoing demand for liquid fuels. The work presented in this dissertation provides an overview of the evaluation and development of these catalysts. In the first chapter, an overview of existing sustainable liquid fuel is provided and the pros and cons of each method is discussed. It explains why dispersed carbonate are a good target for catalysts of RWGS based on some of the previous work done with them. Chapter 2 discusses the significant development in terms of hardware and software required to make a lab-scale flow reactor in order to evaluate these catalysts. The reactor was designed to access industrially relevant conditions while maintaining strict safe operating procedures as well as software controls. Discussion about why certain decisions were made and a brief tutorial is provided to assist future users in operating the system. Chapter 3 discusses the preliminary but promising results obtained from evaluating the dispersed carbonate catalysts in the lab-scale reactor. Key results are discussed and catalyst performance is benchmarked against a transition-metal based catalyst which was highly-active for RWGS. The stable behavior of the dispersed-carbonate catalyst in the presence of H2S impurity is a key result that differentiates it from transition-metal based ones. Finally, Chapter 4 discusses ongoing work to validate the performance of the catalyst for industrial application. The use of high-throughput experimentation is highlighted to provide a large volume of results and allow for rapid screening of potential catalyst formulations. The performance of catalysts prepared at the lab scale is compared against that of catalysts prepared by commercial catalyst manufacturers. Additional metrics for study are identified for the goal of a pilot-scale validation experiment.

Author : Charles See Ho Yeung
Publisher :
Page : 1182 pages
File Size : 29,19 MB
Release : 2011
Category :
ISBN : 9780494780626

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Transition metal catalysis is a powerful tool for the construction of biologically active and pharmaceutically relevant architectures. With the challenge of continually depleting resources that this generation of scientists faces, it is becoming increasingly important to develop sustainable technologies for organic synthesis that utilize abundant and renewable feedstocks while minimizing byproduct formation and shortening the length of synthetic sequences by removing unnecessary protecting group manipulations and functionalizations. To this end, we have developed four new methods that transform inexpensive starting materials to valuable products. This dissertation covers the following key areas: 1) activation of CO2 for a mild and functional group tolerant synthesis of carboxylic acids, 2) oxidative twofold C--H bond activations as a strategy toward biaryls, 3) migratory O- to N-rearrangements in pyridines and related heterocycles for the preparation of N-alkylated heterocycles, and 4) asymmetric hydrogenations of cyclic imines and enamines en route to chiral 1,2- and 1,3-diamines and macrocyclic peptides.

Author : Luke S. Hutchings-Goetz
Publisher :
Page : 0 pages
File Size : 46,56 MB
Release : 2021
Category : Asymmetric synthesis
ISBN :

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The catalytic asymmetric a-functionalization of carbonyl moieties is an important challenge in organic chemistry. While numerous methods have been developed to tackle this challenge, there are few strategies for the direct a-functionalization of acyclic esters. The Snaddon group has developed methodology which accomplishes this sought-after bond formation through the combination of stereo defined C1-ammonium enolates with transition metal electrophiles. The discussion here includes the development and expansion of this reaction to include electron-withdrawing electrophiles and indole acetic acid ester nucleophiles. Furthermore, recent efforts within our laboratory have targeted the development of a one-pot protocol for the preparation of synthetically challenging chiral homoallylic amines. This method involves the previously disclosed asymmetric a-functionalization of esters followed by an in-situ amide formation and oxidative rearrangement. The final portion discussed here is the successful application of this streamlined protocol for the synthesis of enantioenriched homoallylic amines for the synthesis of stereocomplex strychnos indole alkaloid natural products.