Download or read book Developing Catalytic Pathways for the Valorization of Biomass based Platform Molecules Via Electrochemical Reduction and Oxidation Reactions written by Stephen R. Kubota and published by . This book was released on 2018 with total page 173 pages. Available in PDF, EPUB and Kindle. Book excerpt: There is a tremendous global reliance on fossil fuels for the production of a vast amount of products including fuels, plastics, and pharmaceuticals. Dependence on fossil fuels has negative long-term implications due to the finite nature of fossil fuels, as well as environmental impacts from increased atmospheric CO2 levels. Therefore, a renewable and environmentally friendly alternative to fossil fuels is highly desirable. Lignocellulosic biomass, the most abundant form of organic carbon on Earth, provides a highly promising alternative to fossil fuels due to its renewable and environmentally friendly nature. A considerable amount of research has been devoted to converting lignocellulosic biomass into useful products, and many strategies to synthesized biomass-derived alternatives to fossil fuel products have already been demonstrated. The work presented herein describes various electrochemical routes to convert lignocellulosic biomass-derived platform molecules into value added products to replace fossil fuel-derived products via reduction and oxidation reactions. Electrochemical biomass conversion reactions have various advantages over traditional biomass conversion techniques. For example, electrochemical conversions can be performed at ambient temperatures and pressures, the need for stoichiometric amounts of chemical oxidants and reductants are eliminated, water can be used as the oxygen or hydrogen source for oxidation and reduction reactions, and electrochemical reactions are always composed of a simultaneous reduction and oxidation reaction. This means that two valuable products can simultaneously be produced (e.g. simultaneous biomass oxidation and reduction reactions or biomass oxidation and H2 evolution). The strategies reported herein highlight the promising future of electrochemical biomass conversion.

Download or read book Reaction Pathways and Mechanisms in Thermocatalytic Biomass Conversion II written by Marcel Schlaf and published by Springer. This book was released on 2015-10-30 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt: Volume II presents the latest advances in catalytic hydrodeoxygenation and other transformations of some cellulosic platform chemicals to high value-added products. It presents the theoretical evaluation of the energetics and catalytic species involved in potential pathways of catalyzed carbohydrate conversion, pathways leading to the formation of humin-based by-products, and thermal pathways in deriving chemicals from lignin pyrolysis and hydrodeoxygenation. Catalytic gasification of biomass under extreme thermal conditions as an extension of pyrolysis is also discussed. Marcel Schlaf, PhD, is a Professor at the Department of Chemistry, University of Guelph, Canada. Z. Conrad Zhang, PhD, is a Professor at the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, China.

Download or read book Catalytic Processes for The Valorisation of Biomass Derived Molecules written by Francesco Mauriello and published by MDPI. This book was released on 2019-11-22 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the last decades, inedible lignocellulosic biomasses have attracted significant attention for being abundant resources that are not in competition with agricultural land or food production and, therefore, can be used as starting renewable material for the production of a wide variety of platform chemicals. The three main components of lignocellulosic biomasses are cellulose, hemicellulose and lignin, complex biopolymers that can be converted into a pool of platform molecules including sugars, polyols, alchols, ketons, ethers, acids and aromatics. Various technologies have been explored for their one-pot conversion into chemicals, fuels and materials. However, in order to develop new catalytic processes for the selective production of desired products, a complete understanding of the molecular aspects of the basic chemistry and reactivity of biomass derived molecules is still crucial. This Special Issue reports on recent progress and advances in the catalytic valorization of cellulose, hemicellulose and lignin model molecules promoted by novel heterogeneous systems for the production of energy, fuels and chemicals.

Download or read book Biomass Valorization written by Davide Ravelli and published by John Wiley & Sons. This book was released on 2021-05-24 with total page 434 pages. Available in PDF, EPUB and Kindle. Book excerpt: Explore the potential of biomass-based chemicals with this comprehensive new reference from leading voices in the field With the depletion of fossil raw materials a readily ascertainable inevitability, the exploitation of biomass-based renewable derivatives becomes ever more practical and realistic. In Biomass Valorization: Sustainable Methods for the Production of Chemicals, accomplished researchers and authors Davide Ravelli and Chiara Samori deliver a thorough compilation of state-of-the-art techniques and most advanced strategies used to convert biomass into useful building blocks and commodity chemicals. Each chapter in this collection of insightful papers begins by detailing the core components of the described technology, along with a fulsome description of its advantages and limitations, before moving on to a discussion of recent advancements in the field. The discussions are grouped by the processed biomass, such as terrestrial biomass, aquatic biomass, and biomass-deriving waste. Readers will also benefit from the inclusion of: A thorough introduction to the role of biomass in the production of chemicals An exploration of biomass processing via acid, base and metal catalysis, as well as biocatalysis A practical discussion of biomass processing via pyrolysis and thermochemical-biological hybrid processes A concise treatment of biomass processing assisted by ultrasound and via electrochemical, photochemical and mechanochemical means Perfect for chemical engineers, catalytic chemists, biotechnologists, and polymer chemists, Biomass Valorization: Sustainable Methods for the Production of Chemicals will also earn a place in the libraries of environmental chemists and professionals working with organometallics and natural products chemists.

Download or read book Nano Bio Catalysis in Lignocellulosic Biomass Valorization written by Rafael Luque and published by Frontiers Media SA. This book was released on 2019-03-01 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt: The valorization of lignocellulosic biomass, in the form of forest and agricultural wastes, industrial processing side-streams, and dedicated energy crops, toward chemicals, fuels and added-value products has become a major research area with increasing exploitation potential. The efficient and tailored depolymerization of biomass or its primary structural components (hemicellulose, cellulose, and lignin) to platform chemicals, i.e., sugars, phenolics, furans, ketones, organic acids, etc. is highly dependent on the development of novel or modified chemo- and bio-catalytic processes that take into account the peculiarities and recalcitrance of biomass as feedstock, compared for example to petroleum fractions. The present Research Topic in Frontiers in Chemistry, Section of Green and Sustainable Chemistry, entitled “Nano-(bio)catalysis in lignocellulosic biomass valorization” aims to further contribute to the momentum of research and development in the (bio)catalytic conversion of biomass, by featuring original research papers as well as two review papers, authored and reviewed by experts in the field. The Research Topic addresses various representative reactions and processes in biomass valorization, highlighting the importance of developing novel, efficient and stable nano-(bio)catalysts with tailored properties according to the nature of the reactant/feedstock and the targeted products.

Download or read book Aqueous phase Catalytic Conversions of Renewable Feedstocks for Sustainable Biorefineries written by Georgios Papadogianakis and published by Frontiers Media SA. This book was released on 2024-08-23 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt: Today, there is growing interest in aqueous-phase catalytic conversions for the valorization of renewable biomass-based feedstocks for biorefineries to produce, in a sustainable way, biofuels, chemicals, power, energy, materials, pharmaceuticals and food. This is because of the highly polar nature of water which makes it an ideal medium to convert polar biomass-based lignocellulose (cellulose, hemicellulose, lignin), with high oxygen content, and their upgraded products such as hydrophilic carbohydrates, platform chemicals and their derivatives. Another reason which makes water the solvent of choice is that water itself is involved either as a reagent or as a byproduct even in large amounts in typical conversions for the valorization of biomass. The obtained intermediates further react in the aqueous medium, often without any separation and purification, to manufacture more valuable products. This results in substantial energy savings, lower emissions and economic benefits. Furthermore, water could act as a catalyst in conversions of biomass-based feedstocks such as in liquefaction reactions under subcritical conditions. Moreover, novel types of catalytic reactivity have been observed in the aqueous solvent, not only with water-soluble transition metal catalytic complexes, but also with conventional heterogeneous catalysts and catalytic nanoparticles in a broad spectrum of different reactions such as, inter alia, aldol condensations and hydrogenation reactions. For example, in the aqueous-phase hydrogenation of the biomass-based key platform chemical levulinic acid into γ-valerolactone and beyond, employing heterogeneous catalysts and nanoparticles the presence of water has a beneficial effect and accelerates the reaction rates, whereas in organic solvents much lower activities were observed. This promotional effect of water in the hydrogenation of levulinic acid was proved by many experimental and theoretical studies using a broad spectrum of different types of catalytic systems.

Download or read book Reaction Pathways and Mechanisms in Thermocatalytic Biomass Conversion I written by Marcel Schlaf and published by Springer. This book was released on 2015-09-25 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt: Volume I mainly focuses on the current understanding of the reaction pathways and mechanisms involved in several important catalytic conversions of cellulose and carbohydrates. It starts with nanoscale illustrations of biomass structures and describes various reactions including cellulose depolymerization to sugars, catalytic aldose-ketose isomerization and dehydration, selective oxidation, hydrogenolysis of cellulose and sugars, and the conversion of short carbohydrates. The specificity and function of different catalysts and reaction media in relation to the catalytic performances for these reactions are discussed with significant mechanistic details. Marcel Schlaf, PhD, is a Professor at the Department of Chemistry, University of Guelph, Canada. Z. Conrad Zhang, PhD, is a Professor at the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, China.

Download or read book A Study on Catalytic Conversion of Non Food Biomass into Chemicals written by Mizuho Yabushita and published by Springer. This book was released on 2016-01-13 with total page 171 pages. Available in PDF, EPUB and Kindle. Book excerpt: The topic of this thesis is catalytic conversion of non-food, abundant, and renewable biomass such as cellulose and chitin to chemicals. In biorefinery, chemical transformation of polymers to valuable compounds has attracted worldwide interest for building sustainable societies. First, the current situation of this hot research area has been summarized well in the general introduction of the thesis, which helps readers to become familiar with this topic. Next, the author explains high-yielding production of glucose from cellulose by using an alkali-activated carbon as a catalyst, resulting in a yield of glucose as high as 88%, which is one of the highest yields ever reported. The characterization of carbon materials has indicated that weak acid sites on the catalyst promote the reaction, which is markedly different from reported catalytic systems that require strong acids. In addition, the first catalytic transformation of chitin with retention of N-acetyl groups has been developed. The combination of mechanocatalytic hydrolysis and thermal solvolysis enables the production of N-acetylated monomers in good yields of up to 70%. The catalytic systems demonstrated in this thesis are unique in the fields of both chemistry and chemical engineering, and their high efficiencies can contribute to green and sustainable chemistry in the future. Meanwhile, mechanistic studies based on characterization, thermodynamics, kinetics, and model reactions have also been performed to reveal the roles of catalysts during the reactions. The results will be helpful for readers to design and develop new catalysts and reaction systems.

Download or read book Coupling Chemical and Biological Catalysis to Produce Biorenewable Chemicals written by and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent advances in metabolic engineering have allowed for the production of a wide array of molecules via biocatalytic routes. The high selectivity of biocatalysis to remove functionality from biomass can be used to produce platform molecules that are suitable for subsequent upgrading over heterogeneous catalysts. Accordingly, the more robust continuous processing allowed by chemical catalysis could be leveraged to upgrade biologically-derived platform molecules to produce direct or functional replacements for petroleum products. This thesis discusses our progress in developing processes that utilize a combination of chemical and biological catalysis, and using the perspective of heterogeneous chemical catalysis we identify and address challenges associated with bridging the gap between the two catalytic approaches. Chapter 3 and Chapter 4 focus on the development of new chemistry that utilizes bio-catalytically-derived platform molecules to yield high-value biorenewable chemicals. In Chapter 3 we show that furylglycolic acid (FA), a pseudo-aromatic hydroxy-acid suitable for co-polymerization with lactic acid, can be produced from glucose via enzymatically derived cortalcerone using a combination of Brønsted and Lewis acid catalysts. Cortalcerone is first converted to furylglyoxal hydrate (FH) over a Brønsted acid site, and FH is subsequently converted to FA over a Lewis acid site. In Chapter 4, Triacetic acid lactone is demonstrated to be a versatile biorenewable molecule with potential as a platform chemical for the production of commercially valuable bifunctional chemical intermediates and end products, such as sorbic acid. In Chapter 8 we extend this chemistry to the upgrading of 4-hydroxycoumarin to produce high-value pharmaceutical building blocks. Chapter 5 demonstrates that supported Ni, Pt, and Pd catalysts used for liquid phase hydrogenation are inhibited by the biogenic impurities present in biologically-derived feedstocks used to produce high-value chemicals. This inhibition is addressed in Chapter 6, where we show that microenvironments formed around catalytic active sites mitigate catalyst deactivation by biogenic impurities present during production of biorenewable chemicals from biologically-derived species. Finally, in Chapter 7, we use transition state theory as applied to thermodynamically non-ideal systems to explore the origins of the improved stability and activity that we observed in Chapter 6. We conclude with a discussion of future directions.

Download or read book Catalytic Upgrading of Biologically derived Chemicals Via Ring opening Reactions written by Zachary James Brentzel and published by . This book was released on 2017 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt: Research efforts on renewable and sustainable products from biologically-derived sources have shifted directions from the production of fuels to the production of chemicals. The motivation for switching the focus to renewable commodity or high value chemicals stems from the favorable process economics. Renewable and sustainable processes to synthesize chemicals are more economically feasible than those to produce fuels. This dissertation discusses strategies to synthesize biorenewable chemicals from both microbially-derived and lignocellulosic biomass-derived platform chemicals. A significant fraction of lignocellulosic biomass-derived platform chemicals and microbial metabolites are cyclic molecules with heteroatoms. A fraction of the resulting target products are linear, and the reactants need to be selectively ring-opened. We discuss routes, processes, and mechanisms for the upgrading and ring-opening of microbially-derived and lignocellulosic biomass-derived platform chemicals. Chapters 3 and 4 focus on a process for the production of chemicals from microbially-derived triacetic acid lactone (TAL). The first stage in the upgrading of TAL is hydrogenation of the C=C bonds in the ring. Prior work has demonstrated that residual amino acids and vitamins from fermentation media carried through to the hydrogenation are detrimental to catalyst stability. In Chapter 3, we document the degree to which representative amino acids and vitamins inhibit Pt, Pd, and Ni for a probe reaction, cyclohexene hydrogenation. Chapter 4 covers a new chemical pathway to upgrade lactones synthesized from TAL. This project characterizes the vapor phase selectivity for the ring-opening esterification of TAL-derived [delta]-hexalactone (DHL) and biomass-derived [gamma]-valerolactone (GVL) using oxide catalysts. Chapters 5 through 8 detail the process development, technoeconomics, reaction mechanism, and catalyst studies for the production of 1,5-pentanediol (1,5-PD) from biomass-derived furfural. Chapter 5 presents the overview of the process to synthesize 1,5-PD from tetrahydrofurfuryl alcohol (THFA) and includes initial technoeconomic analyses. This chapter also details the reaction network and describes the enhanced reactivity of the new intermediate, 2-hydroxytetrahydropyran (2-HY-THP). Chapter 6 expands upon the process development and provides more in-depth technoeconomic analyses that includes the initial furfural to THFA hydrogenation step. The processes considered in both Chapter 5 and 6 use a noble metal catalyst, Ru, for the hydrogenation of 2-HY-THP to 1,5-PD. In Chapters 7 and 8, we investigate the the feasibility of using an earth abundant metal, Ni, for the hydrogenation. Chapter 7 includes work focused on elucidating the role of oxophilic metals on their enhancement in the hydrogenation rates of carbonyl groups. After determining that Mo and Re provide the greatest degree of promotion, probe reactions studies, extensive catalyst characterization, and density functional theory calculations were performed on the NiMo system. Chapter 8 studies the role of support, oxophilic promoter, and organic functional group of the leaching rate and stability of Ni catalysts.

Download or read book Mechanism Based Design of Green Oxidation Catalysts written by and published by . This book was released on 2015 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: In modern era of scarce resources, developing chemical processes that can eventually generate useful materials and fuels from readily available, simple, cheap, renewable starting materials is of paramount importance. Small molecules, such as dioxygen, dinitrogen, water, or carbon dioxide, can be viewed as ideal sources of oxygen, nitrogen, or carbon atoms in synthetic applications. Living organisms perfected the art of utilizing small molecules in biosynthesis and in generating energy; photosynthesis, which couples carbohydrate synthesis from carbon dioxide with photocatalytic water splitting, is but one impressive example of possible catalytic processes. Small molecule activation in synthetic systems remains challenging, and current efforts are focused on developing catalytic reactions that can convert small molecules into useful building blocks for generating more complicated organic molecules, including fuels. Modeling nature is attractive in many respects, including the possibility to use non-toxic, earth-abundant metals in catalysis. Specific systems investigated in our work include biomimetic catalytic oxidations with dioxygen, hydrogen peroxide, and related oxygen atom donors. More recently, a new direction was been also pursued in the group, fixation of carbon dioxide with transition metal complexes. Mechanistic understanding of biomimetic metal-catalyzed oxidations is critical for the design of functional models of metalloenzymes, and ultimately for the rational synthesis of useful, selective and efficient oxidation catalysts utilizing dioxygen and hydrogen peroxide as terminal oxidants. All iron oxidases and oxygenases (both mononuclear and dinuclear) utilize metal-centered intermediates as reactive species in selective substrate oxidation. In contrast, free radical pathways (Fenton chemistry) are common for traditional inorganic iron compounds, producing hydroxyl radicals as very active, non-selective oxidants. Recent developments, however, changed this situation. Growing families of synthetic iron complexes that resemble active sites of metalloenzymes produce metal-based intermediates (rather than hydroxyl radicals) in reactions with oxygen donors. These complexes are very promising for selective oxygen and peroxide activation. In order to understand the mechanisms of metal-based small molecule activation, kinetically competent metal-oxygen intermediates must be identified. One of the grand challenges identified by the Department of Energy workshop "Catalysis for Energy" is understanding mechanisms and dynamics of catalyzed reactions. The research summarized herein focuses on detailed characterization of the formation and reactivity of various iron-peroxo- and iron-oxo intermediates that are involved in catalysis. Rates of rapid reactions were studied at low temperatures by a specialized technique termed cryogenic stopped-flow spectrophotometry. These measurements identified reaction conditions which favor the formation of catalytically competent oxidants. Chemical structures of reactive complexes was determined, and new, efficient catalysts for hydrocarbon oxidation were synthesized. Importantly, these catalysts are selective, they promote oxidation of hydrocarbons at a specific site. The catalysts are also efficient and robust, hundreds of cycles of substrate oxidation occur within minutes at room temperature. Furthermore, they enable utilization of environmentally friendly oxidants, such as hydrogen peroxide, which produces water as the only byproduct. Mechanistic insights uncovered the role of various acid-containing additives in catalytic oxidations. Proton delivery to the active catalytic sites facilitated oxidations, similarly to the catalytic pathways in metal-containing enzymes. Under certain conditions, two metals in one complex can act in concert, modeling the reactivity of a bacterial enzyme which converts methane into methanol. In related studies, a family of nickel complexes that react with carbon ...

Download or read book Catalytic Conversion of Bio derived Platform Molecules Into Useful Chemicals Via Selective Oxidation written by Leandro Ardemani and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fundamental Reaction Kinetics Studies of Acid catalyzed Biomass Conversion Reactions Into Chemicals and Fuels written by Max A. Mellmer and published by . This book was released on 2016 with total page 169 pages. Available in PDF, EPUB and Kindle. Book excerpt: The transition to a sustainable source of chemicals and energy is being driven by political, economic, and environmental concerns associated with petroleum-derived feedstocks. In this context, the conversion of biomass into platform molecules and fuels has received increasing interest. Acid catalysis is pervasive in biomass conversion processes, and recently, it has been shown that organic solvents are beneficial in the chemical conversion of biomass. This dissertation discusses strategies in utilizing nonaqueous solvents for the efficient upgrading of biomass to platform molecules using both homogeneous and heterogeneous acid catalysts, and based on reaction kinetics studies, we outline fundamental principles in understanding solvation effects in acid-catalyzed reactions. Chapter 3, Chapter 4, and Chapter 5 focus on the upgrading of biomass-derived molecules to yield platform chemicals. In Chapter 3, we show that high yields of hydroxymethylfurfural from glucose can be achieved using biomass-derived solvents and a combination of solid Lewis and Brønsted acids. In Chapter 4, the production of furfural from xylose, arabinose, and ribose was studied using H-Beta zeolite in [gamma]-valerolactone. We show in Chapter 5 that furfuryl alcohol is hydrolyzed to levulinic acid in high yields using H-ZSM-5 zeolite as the catalyst in tetrahydrofuran-water solvent systems. In Chapter 6 and Chapter 7, we use polar aprotic solvents to upgrade constituent fractions of biomass. We show in Chapter 6 that cellulose and corn stover can be converted with high yield to levulinic acid using Amberlyst 70 and [gamma]-valerolactone. Chapter 7 outlines a processing strategy using [gamma]-valerolactone for the simultaneous conversion of hemicellulose and cellulose in a single reactor to produce furfural and levulinic acid. Chapter 8, Chapter 9, and Chapter 10 report reaction kinetics studies providing insights into solvation effects in acid-catalyzed reactions using polar aprotic solvents. In Chapter 8, we studied the reaction kinetics of the dehydration of xylose into furfural using nonaqueous solvents. We show in Chapter 9 that polar aprotic solvents also enhance the kinetics of biomass hydrolysis reactions. Finally, in Chapter 10, we dissect solvation effects into initial and transition state contributions using experimental and computational methodologies. This dissertation is concluded with a discussion of future directions.

Download or read book Acid catalyzed Reactions for the Production of Platform Chemicals from Cellulosic Biomass in Liquid Phase Systems written by and published by . This book was released on 2014 with total page 522 pages. Available in PDF, EPUB and Kindle. Book excerpt: Acid catalysts are used in many applications focused on biomass conversion. Liquid phase processing serves as one of the primary routes to produce platform chemicals from cellulosic biomass. The fundamental challenge with producing products by acid catalyzed reactions is that undesired carbonaceous species (i.e. humins) form by both parallel and series reactions, which limit the selectivity to desired products. The goal of this research is to study the fundamental acid-catalyzed chemistry to produce biomass-derived platform chemicals in liquid phase systems. We use an integrated approach that includes: (1) understanding the fundamental chemistry and reaction pathways through kinetic studies with homogeneous acid catalysts and (2) elucidating the relationship between the properties of solid acid catalysts and their correlation with activity and selectivity of acid catalyzed reactions. We have developed kinetic models for the aqueous phase production of furfural and hydroxymethylfurfural (HMF) from xylose and glucose respectively using homogeneous catalysts. The dehydration chemistry to form these furanic derivatives from carbohydrates is distinguished by a relatively high activation energy step (ca. 120-160 kJ/mol). Undesired humins also form, which typically have lower activation barriers (i.e. 50-70 kJ/mol). Product selectivity can be tuned by altering the Brønsted to Lewis acid site ratio of the acid catalysts. Lewis acid sites decrease furfural and HMF selectivity, as they mainly catalyze the formation of isomerization byproducts and humins. Brønsted acid sites catalyze the dehydration step to produce furfural and HMF. These findings are true for both heterogeneous and homogeneous catalysts. Accordingly, in our studies with solid acid metal(IV) phosphate catalysts, we show that zirconium phosphate with a P/Zr molar ratio of 2 is favorable for levulinic acid production from glucose due to its inherently high surface area and enhanced Brønsted acidity. We have also discovered that HMF can selectively be produced from cellulose under mild reaction conditions in polar aprotic solvents (i.e. tetrahydrofuran) without the presence of water. This pathway goes through a levoglucosan intermediate. The turnover frequency for cellulose conversion increases as the water content in the solvent decreases, with conversion rates in tetrahydrofuran being more than twenty times higher than those in water.

Download or read book Developing Methods to Inform Catalyst Design for the Electrochemical Oxidation of Methane and Alcohols written by Michael James Boyd and published by . This book was released on 2021 with total page 107 pages. Available in PDF, EPUB and Kindle. Book excerpt: As the production of natural gas and agricultural biomass/energy crops increases, new efficient and sustainable technologies will be required to convert these feedstock molecules into the same fuels and chemical we get from conventional petroleum today. Electrochemistry is a possible tool for the conversion of these species that can be coupled to renewable electricity. The discovery and development of selective and active electrocatalysts is one of the primary challenges in utilizing natural gas and biomass resources. But first there is a lack of fundamental understanding in (1) the reaction mechanism and (2) how operating conditions such as potential, electrolyte pH, mass transport, and time affect the the activity and selectivity of catalysts. To this end platinum was used as a model system to study electrochemical methane oxidation at room temperature and pressure. The experimental results on platinum combined with density functional theory calculations show that methane is first thermally activated at Pt (211) like step sites, then the resulting methyl intermediate is electrochemically oxidized to CO* which is in equilibrium with the final product CO2. The equilibrium can be shifted to favor complete oxidation by adjusting the applied electrochemical potential, specifically at potentials below 0.5 V vs. RHE CO* is the most thermodynamically stable species along the reaction pathway whereas above 0.5 V vs. RHE CO2 is now the most stable species. Important to note however is that since the kinetics for methane activation are very slow (barrier of ~0.95 eV) the platinum surface must be free of other adsorbed species, namely protons or hydroxides. Based on reaction mechanism for electrochemical methane oxidation on platinum it is unlikely that partial oxidation of methane on metallic electrodes well occur. For this reason we probed the activity of several transition metal oxide materials with the hope that they may be active for methane oxidation. Unfortunately our initial results suggest no significant methane oxidation occurs on these materials. In the case of biomass oxidation 1st row transition metal oxides have recently been shown to be quite selective in the conversion of alcohols to their corresponding carboxylic acids. Benzyl alcohol was used as a model molecule to study the reaction mechanism for alcohol oxidation on Ni(OH)2 electrodes as a function of potential and electrolyte pH. It was found that the active phase for alcohol oxidation is the metal oxy-hydroxide. The activity and selectivity were found to be heavily dependent on the electrolyte pH. Under strong alkaline conditions (> pH 13) high current densities and complete oxidation of benzyl alcohol to benzoate was favored whereas at more moderately alkaline conditions low current densities and partial oxidation to benzaldehyde was favored. Based on these results we hypothesize that a significant concentration of OH- in solution is required to activated the intermediate product benzaldehyde. The activity of several novel Ni materials was also probed for benzyl alcohol oxidation. Ni-doped nitrided carbons which have single atom nickel active sites were found to be selective for partial oxidation, however further optimization of the catalyst synthesis is required to increase the activity to compete with the bulk Ni(OH)2 electrodes. In conclusion, this dissertation presents a variety of experimental work focused on identifying the reaction mechanism for several oxidation reactions and provides key understanding that can be used towards the development of new electrocatalysts for the oxidation of hydrocarbons and alcohols.

Download or read book Lignin Valorization written by Gregg T. Beckham and published by Royal Society of Chemistry. This book was released on 2018-03-29 with total page 544 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Chapters will specifically focus on the production of fuels and chemicals from lignin."--Page [4] of cover.

Download or read book Handbook of Biomass Valorization for Industrial Applications written by Shahid ul-Islam and published by John Wiley & Sons. This book was released on 2022-01-05 with total page 555 pages. Available in PDF, EPUB and Kindle. Book excerpt: HANDBOOK of BIOMASS VALORIZATION for INDUSTRIAL APPLICATIONS The handbook provides a comprehensive view of cutting-edge research on biomass valorization, from advanced fabrication methodologies through useful derived materials, to current and potential application sectors. Industrial sectors, such as food, textiles, petrochemicals and pharmaceuticals, generate massive amounts of waste each year, the disposal of which has become a major issue worldwide. As a result, implementing a circular economy that employs sustainable practices in waste management is critical for any industry. Moreover, fossil fuels, which are the primary sources of fuel in the transportation sector, are also being rapidly depleted at an alarming rate. Therefore, to combat these global issues without increasing our carbon footprint, we must look for renewable resources to produce chemicals and biomaterials. In that context, agricultural waste materials are gaining popularity as cost-effective and abundantly available alternatives to fossil resources for the production of a variety of value-added products, including renewable fuels, fuel components, and fuel additives. Handbook of Biomass Valorization for Industrial Applications investigates current and emerging feedstocks, as well as provides in-depth technical information on advanced catalytic processes and technologies that enable the development of all possible alternative energy sources. The 22 chapters of this book comprehensively cover the valorization of agricultural wastes and their various uses in value-added applications like energy, biofuels, fertilizers, and wastewater treatment. Audience The book is intended for a very broad audience working in the fields of materials sciences, chemical engineering, nanotechnology, energy, environment, chemistry, etc. This book will be an invaluable reference source for the libraries in universities and industrial institutions, government and independent institutes, individual research groups, and scientists working in the field of valorization of biomass.