[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 : 49,85 MB
Release : 2021
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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 : National Academies of Sciences, Engineering, and Medicine
Publisher : National Academies Press
Page : 257 pages
File Size : 34,17 MB
Release : 2019-02-22
Category : Science
ISBN : 0309483360

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In the quest to mitigate the buildup of greenhouse gases in Earth's atmosphere, researchers and policymakers have increasingly turned their attention to techniques for capturing greenhouse gases such as carbon dioxide and methane, either from the locations where they are emitted or directly from the atmosphere. Once captured, these gases can be stored or put to use. While both carbon storage and carbon utilization have costs, utilization offers the opportunity to recover some of the cost and even generate economic value. While current carbon utilization projects operate at a relatively small scale, some estimates suggest the market for waste carbon-derived products could grow to hundreds of billions of dollars within a few decades, utilizing several thousand teragrams of waste carbon gases per year. Gaseous Carbon Waste Streams Utilization: Status and Research Needs assesses research and development needs relevant to understanding and improving the commercial viability of waste carbon utilization technologies and defines a research agenda to address key challenges. The report is intended to help inform decision making surrounding the development and deployment of waste carbon utilization technologies under a variety of circumstances, whether motivated by a goal to improve processes for making carbon-based products, to generate revenue, or to achieve environmental goals.

Author : P.A. Chaloner
Publisher : Springer Science & Business Media
Page : 293 pages
File Size : 23,97 MB
Release : 2013-11-11
Category : Science
ISBN : 9401717915

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Homogeneous hydrogenation is one of the most thoroughly studied fields of homogeneous catalysis. The results of these studies have proved to be most important for an understanding of the underlying principles of the activation of small molecules by transition metal complexes. During the past three decades homogeneous hydrogenation has found widespread application in organic chemistry, including the production of important pharmaceuticals, especially where a sophisticated degree of selectivity is required. This volume presents a general account of the main principles and applications of homogeneous hydrogenation by transition metal complexes. Special attention is devoted to the mechanisms by which these processes occur, and the role of the recently discovered complexes of molecular hydrogen is described. Sources of hydrogen, other than H2, are also considered (transfer hydrogenation). The latest achievements in highly stereoselective hydrogenations have made possible many new applications in organic synthesis. These applications are documented by giving details of the reduction of important unsaturated substrates (alkenes, alkynes, aldehydes and ketones, nitrocompounds, etc.). Hydrogenation in biphasic and phase transfer catalyzed systems is also described. Finally, a discussion of the biochemical routes of H2 activation highlights the similarities and differences in performing hydrogenation in both natural and synthetic systems. For researchers working in the fields of homogeneous catalysis, especially in areas such as pharmaceuticals, plastics and fine chemicals.

Author : Yuichiro Himeda
Publisher : John Wiley & Sons
Page : 322 pages
File Size : 45,53 MB
Release : 2021-06-28
Category : Technology & Engineering
ISBN : 3527346635

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A guide to the effective catalysts and latest advances in CO2 conversion in chemicals and fuels Carbon dioxide hydrogenation is one of the most promising and economic techniques to utilize CO2 emissions to produce value-added chemicals. With contributions from an international team of experts on the topic, CO2 Hydrogenation Catalysis offers a comprehensive review of the most recent developments in the catalytic hydrogenation of carbon dioxide to formic acid/formate, methanol, methane, and C2+ products. The book explores the electroreduction of carbon dioxide and contains an overview on hydrogen production from formic acid and methanol. With a practical review of the advances and challenges in future CO2 hydrogenation research, the book provides an important guide for researchers in academia and industry working in the field of catalysis, organometallic chemistry, green and sustainable chemistry, as well as energy conversion and storage. This important book: Offers a unique review of effective catalysts and the latest advances in CO2 conversion Explores how to utilize CO2 emissions to produce value-added chemicals and fuels such as methanol, olefins, gasoline, aromatics Includes the latest research in homogeneous and heterogeneous catalysis as well as electrocatalysis Highlights advances and challenges for future investigation Written for chemists, catalytic chemists, electrochemists, chemists in industry, and chemical engineers, CO2 Hydrogenation Catalysis offers a comprehensive resource to understanding how CO2 emissions can create value-added chemicals.

Author : Jennifer Wood Eddy
Publisher :
Page : 230 pages
File Size : 11,80 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 : Chastity Li
Publisher :
Page : 0 pages
File Size : 42,57 MB
Release : 2023
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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 : Chenlu Xie
Publisher :
Page : 90 pages
File Size : 21,67 MB
Release : 2018
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The subject of this dissertation focuses on the design and synthesis of new catalysts with well-defined structures and superior performance to meet the new challenges in heterogenous catalysis. The past decade has witness the development of nanoscience as well as the inorganic catalysts for industrial applications, however there are still fundamental challenges and practical need for catalysis. Specifically, it is desirable to have the ability to selectivity produce complex molecules from simple components. Another great challenge faced by the modern industry is being environmentally friendly, and going for a carbon neutral economy would require using CO2 as feedstock to produce valuable products. The work herein focuses on the design and synthesis of inorganic nanocrystal catalysts that address these challenges by achieving selective and sequential chemical reactions and conversion of CO2 to valuable products. Chapter 1 introduces the development of heterogenous catalysis and the colloidal synthesis of metal nanoparticles catalysts with well-controlled structure. Tremendous efforts have been devoted to understanding the nucleation and growth process in the colloidal synthesis and developing new methods to produce metal nanoparticles with controlled sizes, shapes, composition. These well-defined catalytic system shows promising catalytic performance, which can be modulated by their structure (size, shape, compositions and the metal-oxide interfaces). The chapters hereafter explore the synthesis of new catalysts with controlled structures for catalysis. Chapter 2 presents the design and synthesis of a three dimensional (3D) nanostructured catalysts CeO2-Pt@mSiO2 with dual metal-oxide interfaces to study the tandem hydroformylation reaction in gas phase, where CO and H2 produced by methanol decomposition (catalyzed by CeO2-Pt interface) were reacted with ethylene to selectively yield propyl aldehyde (catalyzed by Pt-SiO2 interface). With the stable core-shell architecture and well-defined metal-oxide interfaces, the origin of the high propyl aldehyde selectivity over ethane, the dominant byproduct in conventional hydroformylation, was revealed by in-depth mechanism study and attributed to the synergybetween the two sequential reactions and the altered elementary reaction steps of the tandem reaction compared to the single-step reaction. The effective production of aldehyde through the tandem hydroformylation was also observed on other light olefin system, such as propylene and 1-butene. Chapter 3 expands the strategy of tandem catalysis into conversion of CO2 with hydrogen to value-added C2-C4 hydrocarbons, which is a major pursuit in clean energy research. Another well-defined 3D catalyst CeO2–Pt@mSiO2–Co was designed and synthesized, and CO2 was converted to C2-C4 hydrocarbons with 60% selectivity on this catalyst via reverse water gas shift reaction and subsequent Fischer–Tropsch process. In addition, the catalysts is stable and shows no obvious deactivation over 40 h. The successful production of C2−C4 hydrocarbons via a tandem process on a rationally designed, structurally well-defined catalyst demonstrates the power of sophisticated structure control in designing nanostructured catalysts for multiple-step chemical conversions. Chapter 4 turns to electrochemistry and apply the precision in catalyst structural design to the development of electrocatalysts for CO2 reduction. Herein, atomic ordering of bimetallic nanoparticles were synthetically tuned, from disordered alloy to ordered intermetallic, and it showed that this atomic level control over nanocrystal catalysts could give significant performance benefits in electrochemical CO2 reduction to CO. Atomic-level structural investigations revealed the atomic gold layers over the intermetallic core to be sufficient for enhanced catalytic behavior, which is further supported by DFT analysis.

Author : Wenjia Wang
Publisher :
Page : pages
File Size : 47,15 MB
Release : 2019
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The catalytic CO2 hydrogenation to C2+ higher hydrocarbons has attracted increasing attention due to both environmental and sustainability concerns. Past efforts have focused on modifying Fe-based catalysts and promoters with or without support. Cu-based catalyst is well known for its activity in water-gas shift (WGS) as well as reverse water-gas shift (RWGS) reaction and does not lead to CO2 methanation compared with other metals such as Co, Ni and Ru. Potassium (K) has been known as an effective promoter for CO and CO2 hydrogenation to olefin-rich higher hydrocarbons over Fe-based catalysts. Thus, this work aims at clarifying the effect of combining Fe and Cu, and influence of addition of K promoter on the activity and product selectivity towards C2+ hydrocarbons from CO2 hydrogenation, and developing a fundamental understanding on the structure and properties that affect the catalytic performance. The Fe-Cu bimetallic catalysts with various compositions, with or without K promoter, were prepared and examined in CO2 hydrogenation at relatively mild reaction conditions (573 K and 1.1 MPa).The combination of Fe and Cu led to a synergistic promotion of CO2 conversion and C2+ hydrocarbon formation rate when the Cu/(Fe + Cu) atomic ratio was 0.17 for -Al2O3 supported Fe-Cu catalysts. XRD results and high resolution TEM images demonstrate the presence of the metallic and alloy phases in the reduced Fe-Cu(0.17) catalysts. The strong interaction between Fe and Cu was observed from H2-TPR profiles. The complementary roles of each metal component in the bimetallic catalysts led to the well-dispersed metals in the alloy particles. The combination of Fe and Cu promoted the adsorption towards moderately and strongly adsorbed H2 (Type III + IV). The increased amount of moderately and strongly adsorbed H2 appears to correlate to the observed synergetic effect on C2+ hydrocarbon promotion. FT-IR results showed that adsorbed CO was enhanced in Fe-Cu bimetallic catalysts. Existence of formate and formic acid species in Fe-Cu bimetallic catalysts also proved the CO2 direct hydrogenation to C2+ hydrocarbons. The in situ XAS results showed that Fe peaks in both Fe and Fe-Cu catalysts were similar to that of Fe3O4, but Fe-Cu catalyst was more reducible to Fe0.The addition of K into Fe-Cu bimetallic catalysts led to a strong promotion of CO2 conversion and C2+ hydrocarbon formation rate. K is proved to be an effective promoter for Fe-Cu for enhancing C2+ hydrocarbon formation, which leads to promotion of C-C chain growth and light olefin yield, as well as suppression of CH4. K promoted Fe-Cu catalyst enhanced the adsorption towards all types of adsorbed CO2 (Type I, II, III and IV). The increased amount of moderately and strongly adsorbed CO2 appears to correlate to the observed synergetic effect on C5+ hydrocarbon promotion. Kinetic study demonstrated that CO were formed as a primary product from CO2 hydrogenation (reverse water-gas shift reaction; RWGS) and the produced CO was then hydrogenated to hydrocarbons (FTS). Direct hydrogenation on Fe catalyst was suggested but the contribution of such route would be relatively small. Light olefins and paraffins (C2 - C4) would form simultaneously from hydrogenation, but some of these olefins could be further hydrogenated to paraffins.

Author : Eduardo Valle (Researcher in chemical engineering)
Publisher :
Page : pages
File Size : 15,41 MB
Release : 2021
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ISBN :

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In attempts to address the threats of climate change, countries are making efforts to mitigate their emissions of greenhouse gases like carbon dioxide (CO2). The transition from economies driven by energy and chemicals derived from fossil fuel feedstocks to cleaner alternative fuels and technologies are met with great challenges. In the field of fuel and chemical production specifically, the transformation of carbon monoxide (CO) and CO2, produced through alternative technologies, to value added chemical products require catalysts that are active, selective, and stable. Current research efforts have focused on heavy characterization of catalysts in attempts of establishing a structure-activity correlation to help design and engineer the catalyst of the future. This thesis will focus on the design and characterization of two supported transition metal phosphide (TMP) catalysts, molybdenum phosphide (MoP) and ruthenium phosphide (RuP), and a bimetallic nickel iron (NiFe) catalyst. The first TMP, MoP, was specifically designed and optimized for the higher alcohol synthesis (HAS) reaction from synthesis gas (syngas) (CO/H2). Higher alcohols are defined as an alcohol group containing two or more carbon atoms., like ethanol. Through a systematic design approach, the optimal amount of potassium (K) promoter, P and Mo was determined and synthesized on three different supports: amorphous silica (SiO2), ordered silica (SBA-15), and mesoporous carbon (C). The different combinations led to contrasting catalytic performance with respect the HAS activity. The second TMP, RuP, was designed and optimized for the methanol synthesis (MS) reaction. Ru catalysts are known as Fischer-Tropsch synthesis (FTS) catalysts as they selectively produce hydrocarbons. This study was able to change the intrinsic catalytic nature of Ru through addition of P. Catalytic results showed that the presence of P transformed the Ru FTS catalyst to a MS catalyst. The NiFe catalyst was tested for the ethane dehydrogenation reaction, in which the essential feedstock chemical ethylene is produced. This catalyst was tested for direct ethane dehydrogenation, in which only ethane is fed to the reactor along with H2 to mitigate coking, and oxidative ethane dehydrogenation, where CO2 is fed to promote the reacting and mitigate coking. The catalysts were also synthesized on two different supports, SiO2 and C, to quantify support effects. The overall goal of these studies was to determine the influence that addition of promoters, like K, phosphides, and secondary metals have on catalytic properties and how we might use that to design catalysts with improved activity, selectivity, and stability.