Download or read book Formaldehyde Yields from Methanol Electrochemical Oxidation on Platinum and Supported Catalysts written by Christina L. Childers and published by . This book was released on 1999 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Methanol Oxidation Over Copper and Silver Monometallic and Bimetallic Supported Catalysts written by Luter Leke and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The partial oxidation of methanol to formaldehyde with air as oxidant has been studied with supported monometallic and bimetallic catalysts of copper and silver over a range of temperature and contact times. This was done to investigate the influence the bimetallics could possibly have on either the reaction pathways and/or the product(s) selectivity of the oxidation of methanol. Characterisation of these catalysts was performed by nitrogen adsorption and porosity measurements, XRD, and IR spectroscopy of adsorbed methanol and of adsorbed CO. These results indicated no crystalline phases of the loaded metals to be present. CO adsorption showed the presence of small cluster metal atoms on the surface of the catalysts. The reduction peaks from TPR also revealed the presence of partially oxidised and dispersed metal atoms. Infra-red studies of methanol adsorbed on these sample catalysts revealed the presence of intermediate methoxy and formate species which are believed to be formed in the course of the reactions. Results showed the monometallic copper and silver catalyst to be more active than the bimetallics. Although formaldehyde selectivities and yields were generally low, they were highest for the bimetallics supported on the silica catalyst than the monometalics and alumina supported samples. Copper-silver interaction in the bimetallic was proposed to enhance the reduction of the silver that enhanced the selectivity to formaldehyde. In particular under conditions, low conversions of methanol saw highest selectivities to formaldehyde. There was also a pronounced effect of the supports on product distribution and activities with the alumina based samples being more active than the silica supported ones, with the product distributions on the alumina supported significantly showing high yields of DME while the silica showed high yield for methyl formate with COx and CH4 detected in small quantities on all the catalysts within the parameters investigated.
Download or read book Fuel Cell Catalysis written by Andrzej Wieckowski and published by John Wiley & Sons. This book was released on 2009-04-01 with total page 722 pages. Available in PDF, EPUB and Kindle. Book excerpt: Wiley Series on Electrocatalysis and Electrochemistry Fuel Cell Catalysis A Surface Science Approach A Core reference on fuel cell catalysis Fuel cells represent an important alternative energy source and a very active area of research. Fuel Cell Catalysis brings together world leaders in this field, providing a unique combination of state-of-the-art theory and computational and experimental methods. With an emphasis on understanding fuel cell catalysis at the molecular level, this text covers fundamental principles, future challenges, and important current research themes. Fuel Cell Catalysis: Provides a molecular-level description of catalysis for low-temperature polymer-electrolyte membrane fuel cells, including both hydrogen-oxygen cells and direct alcohol cells Examines catalysis issues of both anode and cathode such as oxygen reduction, alcohol oxidation, and CO tolerance Features a timely and forward-looking approach through emphasis on novel aspects such as computation and bio-inspiration Reviews the use and potential of surface-sensitive techniques like vibrational spectroscopy (IR, Raman, nonlinear spectroscopy, laser), scanning tunneling microscopy, X-ray scattering, NMR, electrochemical techniques, and more Reviews the use and potential of such modern computational techniques as DFT, ab initio MD, kinetic Monte Carlo simulations, and more Surveys important trends in reactivity and structure sensitivity, nanoparticles, "dynamic" catalysis, electrocatalysis vs. gas-phase catalysis, new experimental techniques, and nontraditional catalysts This cutting-edge collection offers a core reference for electrochemists, electrocatalysis researchers, surface and physical chemists, chemical and automotive engineers, and researchers in academia, research institutes, and industry.
Download or read book Polymer Electrolyte Membrane and Direct Methanol Fuel Cell Technology written by Christoph Hartnig and published by Elsevier. This book was released on 2012-03-19 with total page 437 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polymer electrolyte membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs) technology are promising forms of low-temperature electrochemical power conversion technologies that operate on hydrogen and methanol respectively. Featuring high electrical efficiency and low operational emissions, they have attracted intense worldwide commercialization research and development efforts. These R&D efforts include a major drive towards improving materials performance, fuel cell operation and durability. In situ characterization is essential to improving performance and extending operational lifetime through providing information necessary to understand how fuel cell materials perform under operational loads.This two volume set reviews the fundamentals, performance, and in situ characterization of PEMFCs and DMFCs. Volume 1 covers the fundamental science and engineering of these low temperature fuel cells, focusing on understanding and improving performance and operation. Part one reviews systems fundamentals, ranging from fuels and fuel processing, to the development of membrane and catalyst materials and technology, and gas diffusion media and flowfields, as well as life cycle aspects and modelling approaches. Part two details performance issues relevant to fuel cell operation and durability, such as catalyst ageing, materials degradation and durability testing, and goes on to review advanced transport simulation approaches, degradation modelling and experimental monitoring techniques.With its international team of expert contributors, Polymer electrolyte membrane and direct methanol fuel cell technology Volumes 1 & 2 is an invaluable reference for low temperature fuel cell designers and manufacturers, as well as materials science and electrochemistry researchers and academics. - Covers the fundamental science and engineering of polymer electrolyte membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs), focusing on understanding and improving performance and operation - Reviews systems fundamentals, ranging from fuels and fuel processing, to the development of membrane and catalyst materials and technology, and gas diffusion media and flowfields, as well as life cycle aspects and modelling approaches - Details performance issues relevant to fuel cell operation and durability, such as catalyst ageing, materials degradation and durability testing, and reviews advanced transport simulation approaches, degradation modelling and experimental monitoring techniques
Download or read book Design Construction and Research Application of a Differential Electrochemical Mass Spectrometer DEMS written by Sean James Ashton and published by Springer Science & Business Media. This book was released on 2012-07-11 with total page 234 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sean Ashton's doctoral thesis, which he finished at the Technical University in Munich, describes the challenge of constructing a Differential Electrochemical Mass Spectrometer instrument (DEMS). DEMS combines an electrochemical cell with mass spectrometry via a membrane interface, allowing gaseous and volatile electrochemical reaction species to be monitored online. The thesis carefully introduces the fuel cell electrocatalyst development concerns before reviewing the pertinent literature on DEMS. This is followed by the presentation and discussion of the new extended design, including a thorough characterization of the instrument. The capabilities of the new setup are demonstrated in two research studies: The methanol oxidation reaction on Pt and PtRu catalysts, and the electrochemical corrosion of fuel cell catalyst supports. Despite both topics having long since been studied, new insights can be obtained through careful investigations with the new DEMS instrument that are of great, general interest. The thesis and the instrument thus show the way for future investigations in the field.
Download or read book Partial Oxidation of Methanol to Formaldehyde Over Sb Mo Oxide Catalysts written by Rafael Alfredo Díaz Real and published by . This book was released on 1991 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The kinetics of the vapor phase air oxidation of methanol to formaldehyde over molybdenum oxide catalysts, antimony oxide catalyst, and their mixtures (both supported and unsupported), at atmospheric pressure and different operating conditions, have been studied in a fixed-bed integral reactor heated by a fluidized sand bath. The effect of various process variables, namely the process temperature (T), the ratio of catalysts to feed flow rate or space time (W/F), and the ratio of methanol fed to air (R), on conversion and yield have been determined. A screening study at varying operating conditions was performed to determine the optimum composition of a Sb$\sb2\rm O\sb4$-MoO$\sb3$ mixture. On the basis of this study a catalyst containing 67% $\rm Sb\sb2O\sb4$-33% MoO$\sb3$ was selected for the detailed kinetic study of oxidation of methanol to formaldehyde. The operating conditions studied were as follows: temperature in the range 623 to 698 K, space times from 5 to 50 $\rm g\sb{cat}/mol\sb{CH\sb3OH}h\sp{-1},$ and methanol to air ratios in the range 0.04 to 0.10 mol$\rm\sb{CH\sb3OH}h\sp{-1}/mol\sb{air}h\sp{-1}.$ This catalyst proved to be highly active and selective to formaldehyde formation. Yields up to $\sim$100% were obtained. Best operating conditions found were obtained at a space time of 27.5 for a methanol/air ratio of 0.06 and a temperature of 698 K. The rate equation for the oxidation of methanol to formaldehyde was derived on the basis of a two-stage redox mechanism$$\eqalign{\rm CH\sb3OH\sb{(g)} + S\sb{ox}\ {\buildrel{k\sb1}\over{\to}}\ &\rm HCHO\sb{(g)} + H\sb2O\sb{(g)} + S\sb{red}\cr\rm O\sb{2\sb{(g)}} + &\rm S\sb{red}\ {\buildrel{k\sb2}\over{\to}}\ S\sb{ox}\cr}$$where S$\rm\sb{ox}$ represents an active site of lattice oxygen and S$\rm\sb{red}$ represents a reduced site of lattice oxygen. The rate equation for the temperature of 648 to 698 K which correlated the data was$$\rm r = {k\sb1P\sb{M}\over 1+{k\sb1P\sb{M}\over 2k\sb2P\sb{O\sb2}}}$$where k$\sb1$ and k$\sb2$ are the temperature dependent rate constants of steps one and two. The equations relating k$\sb1$ and k$\sb2$ with temperature were$$\eqalign{&\rm ln\ k\sb1 = -6.4039-{6.9153\times10\sp3\over T}\cr&\rm ln\ k\sb2 = -3.0154 + {1.8809\times10\sp3\over T}\cr}$$ Several spectroscopic and analytical techniques, viz, electron spin resonance (ESR), x-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM), and adsorption studies were used to characterize the catalysts. The surface are of the catalyst used in the kinetic study was 6.1 m$\sp2$/g as determined by the BET method. A preliminary study of the Sb-Mo oxide mixture (load of $\sim$5 wt%) supported on Y zeolite was also carried out. Maximum yield obtained was comparable to that obtained with pure MoO$\sb3.$ A new catalyst has been developed that gave nearly 100% conversion and 100% yield. The industrial potential of this catalyst is very promising.
Download or read book Carbon Composite Catalysts written by Mohammad Jawaid and published by Springer Nature. This book was released on 2022-06-04 with total page 425 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides an overview of the fundamentals and recent advances in the field of carbon composite catalysts, including graphene, carbon nanotubes, mesoporous carbons, graphitic carbon nitrides, and related composites. Special focus is placed on their controllable preparation and applications in the gas phase, liquid phase, electrochemical, and photocatalytic reactions, as well as defect and surface chemistry-related catalytic activities of carbon materials. Some perspectives are highlighted on the development of more efficient carbonaceous catalysts featuring high stability, low cost, optimized structures, and enhanced performance, which are the key factors to accelerate the designed preparation and commercialization of carbon composite catalysts. The book will also present the latest studies of carbon-based composite catalysts for clean energy change and storage, nature protection, and essential industrial production and storage and include the key challenges and future opportunities in this exciting field.
Download or read book Current Trends and Future Developments on Bio Membranes written by Angelo Basile and published by Elsevier. This book was released on 2020-03-20 with total page 336 pages. Available in PDF, EPUB and Kindle. Book excerpt: Membrane Systems for Hydrogen Production offers an overview of advanced technologies in the field of both catalysts and membrane technologies for hydrogen productions and energy saving. Catalysts play an irreplaceable role in chemical engineering for carrying out reaction at industrial level. Membrane processes are today well-recognized technologies in many fields, such as water and wastewater treatment, gas separation and purification, etc. This book relates these two fields and their role in electrochemical hydrogen production by presenting 5 specific chapters where the catalysts are compared to the membrane technology. The purpose of this book is to provide an overview on recently developed catalysts which work in combination with membrane operations for energy savings. This combination provides an example of strategies for engineering development and process intensification of interest for both industrial and developing countries. - Provides an overview of the interconnections between membrane technology and catalysts related to the electrochemical hydrogen production - Provides a comprehensive review of advanced research on the catalysts used in electrochemical processes and the use of related membrane processes - Addresses the key issues to introduce considerable process intensification in the hydrogen production
Download or read book Understanding the Effect of Modifying Elements in Supported Vanadia Bilayered Catalysts for Methanol Oxidation to Formaldehyde written by William Collins Vining and published by . This book was released on 2011 with total page 330 pages. Available in PDF, EPUB and Kindle. Book excerpt: The field of heterogeneous catalysis has long been interested in understanding the role of site structure on reactivity and selectivity for the rational design of catalysts. Vanadia is of particular interest because of its potential to be highly active and selective for a variety of reactions, such as oxidative dehydrogenation of alkanes to alkenes, or the oxidation of n-butane to maleic anhydride. When supported, vanadia can exist in several environments depending on its surface coverage. At the lowest loadings, below 2 V/nm2, the vanadium exists predominantly in well dispersed, tetrahedral structures with 3 V-O-support bonds and 1 V=O bond. At higher loadings, above 2 V/nm2, V-O-V bonds form on the surface, and at loadings above 7 V/nm2, the vanadia begins to form 3 dimensional domains of V2O5. Methanol oxidation rates over catalysts with varying vanadia loadings have shown no significant effect of the V surface density on the formaldehyde formation rate. However, significant differences in the formaldehyde production rates are observed for different supports. Changing the support from silica to titania or zirconia, will result in increases in the production of formaldehyde from methanol by over an order of magnitude for similar vanadia surface coverages. These differences in rate are observed even though the reaction mechanism is believed to be the same regardless of the support. The mechanism is thought to proceed as follows. First methanol dissociatively adsorbs across a V-O-support bond, producing V-OCH3 and M-OH (M = Si, Ti, Zr, Ce) in a quasi-equilibrated step. Next a surface oxygen abstracts hydrogen from the methoxy group in the rate determining step, and formaldehyde desorbs. The final steps are fast and involve the production of H2O from neighboring hydroxyls and the reoxidation of the catalyst by gas-phase oxygen. When vanadia is supported on bulk TiO2, ZrO2, or CeO2, the support surface area is relatively small (2̃00 m2/g at its highest), and the bulk support causes side reactions which make it difficult to understand the role of the vanadia. Furthermore, by using a bulk support, only the vanadia surface coverage can be varied, such that the effect of different V structures can be elucidated, but not that of V-O-M bonds. Therefore, high surface area silica with a variable coverage of two-dimensional TiO2, ZrO2, and CeO2 layers are used to support isolated vanadate structures to vary the quantity of vanadia bound to the modifying layer. These bilayered catalysts can be used to determine the effect of the V-O-support bonds on the formaldehyde production rate. Three mesoporous silica supports, MCM-48 (1550 m2/g), MCM-41 (1353 m2/g), and SBA-15 (700 m2/g) were used as the high surface area silica. Ti was grafted to the MCM-48 surface using Ti(OiPr)4 and a maximum surface coverage of 2.8 Ti/nm2 was obtained after 3 graftings. The grafting of zirconium was performed using Zr-2-methyl-2-butoxide on MCM-41, and a maximum loading of 2.1 Zr/nm2 was achieved after 3 graftings. The final modifying element, cerium, was grafted onto SBA-15 using Ce(OtBu)4 for a maximum surface coverage of 0.9 Ce nm-2. After treating the MOx/SiO2 (M = Ti, Zr, Ce) samples in air to remove any organic ligands, OV(OiPr)3 was grafted onto the MOx/SiO2 (M = Ti, Zr, Ce) support to achieve the desired V surface coverage of approx. 0.7 V/nm2. The resulting catalysts contain amorphous two-dimensional layers of TiO2, ZrO2, or CeO2 with V existing in a pseudo-tetrahedral structure on the surface. As the surface density of the modifying element layer increases, the quantity of vanadia bound to TiO2, ZrO2, or CeO2 increases. For the VOx/ZrO2/SiO2 catalysts, the fraction of vanadia bound to the zirconia layer was able to be quantified and determined to be 35% of all V for a Zr surface density of 2.8 Zr nm-2. Even for small quantities of modifying elements (0.2 M nm-2), the apparent rate constant for formaldehyde production on VOx/MO2/SiO2 (M = Ti, Zr, Ce) is an order of magnitude higher than for VOx/SiO2 catalysts at the same V surface density. Regardless of the modifying element used, the increase in apparent rate constant is comparable for all catalysts. As the modifying element surface density is increased, the apparent rate constant also increases, which is a result of an increasing fraction of V bound to the MOx layer. Each of these bilayered catalysts can be described using a two-site model of VOx/SiO2 and VOx/MO2 (M = Ti, Zr, Ce) with the latter being responsible for the increased apparent rate constant. This higher activity for the VOx/MO2 site is due to a lower apparent activation energy. For VOx/SiO2, the apparent activation energy is 23 kcal mol-1, but is approximately 17 kcal mol-1 for VOx/MO2 sites. The apparent activation energy can be expressed as the sum of the heat of methanol adsorption and the activation energy for H-abstraction. My results indicate that the lower apparent activation energy observed for the bilayered catalysts is a result of a decrease in the activation energy for H-abstraction. This lower energy pathway occurs because the MOx layer can abstract H from surface methoxy groups. For VOx/SiO2, however, the vanadyl oxygen abstracts H in a higher energy step.
Download or read book Characterization of Novel Catalysts for Methanol Oxidation and Oxygen Reduction in Direct Methanol Fuel Cells written by Hwangchan Yoo and published by . This book was released on 2001 with total page 388 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Comparison of the Catalytic and Electrolytic Oxidation of Methanol and Formaldehyde on Platinum written by Ying Chech Chiu and published by . This book was released on 1965 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fuel Cells written by B. Viswanathan and published by CRC Press. This book was released on 2007 with total page 512 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The book is a comprehensive reference book, explaining concepts and their applications. The interdisciplinary approach that draws on and clarifies the most recent research trends, makes this book interesting to everyone who is concerned with energy demands and fuel cells."--Jacket.
Download or read book Methanol Oxidation on Transition Elements Oxides written by Abdulmohsen Alshehri and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Methanol oxidation to formaldehyde is one of the most important industries in our lives; the reaction occurs on catalyst surface in heterogeneous catalysis. Iron molybdate is the current selective catalyst. However, molybdenum volatilises during methanol oxidation and leaving the catalyst with a low molybdenum ratio, which deactivates the catalyst, a 2.2 Mo: 1Fe iron molybdate catalyst was used instead the stoichiometric catalyst, while yield of formaldehyde cannot be 100%. The goal of this study is to find more selective and more productive catalyst than iron molybdate catalyst, the first step is to find another transition element as selective as molybdenum, because molybdenum is the selective part, and iron is the active part, the resulting iron molybdate catalyst is a selective catalyst to formaldehyde near molybdenum and active near iron. Experimentally, catalysts were prepared using co-precipitation method, however, some doped catalysts were papered by incipient wetness impregnation, also sol-immobilization was used to prepare nano-gold particles on the surfaces of few supports. Catalysts characterizations were carried out within several techniques for the surface analysis (XPS) and bulk analysis (XRD), also the surface area was measured by BET equipment. Raman too was used in this study, while micro-reactor was the reactor to determine selectivity and activity of each catalyst. When molybdenum replaced by vanadium, the catalyst yielded 100% formaldehyde at 200 oC; moreover, tungsten was selective. Likewise, iron was replaced by other active metals such as manganese, copper and bismuth, which are active. Nano-gold improved activity when doped on molybdenum oxide and iron molybdate supports.
Download or read book The Partial Oxidation of Methanol to Formaldehyde Over Molybdenum containing Catalysts written by Tsong-Jen Yang and published by . This book was released on 1982 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Partial Oxidation of Methanol to Formaldehyde Over Molybdenum tin Oxide Catalysts written by Rowaida George Zoumot and published by . This book was released on 1992 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The vapor phase air oxidation of methanol to formaldehyde was investigated over molybdenum oxide, tin oxide and their mixtures in an integral flow reactor at atmospheric pressure between temperature of 513 and 573 K, a space time of 10-40 hr g-cat/g-mol methanol and a molar ratio of 0.04-0.1 mol CH3OH/mol air. Experiments were done under such conditions that the effects of internal and external heat and mass transfer effects were negligible. The effects of several process variables, temperature, space time and methanol/air ratio on the conversion of methanol and the selectivity of the catalyst for formaldehyde production were determined. The results indicated that the impact of the process variables on the conversion, selectivity and yield of formaldehyde were in the following decreasing order T > W/F > R. A screening study indicated the optimum catalyst composition to be 50% SnO2 and 50% MoO3, while conversion increased with temperature and W/F selectivity decreased. This catalyst proved to be highly active and selective to formaldehyde production. Selectivity and yield of up to about 100% were obtained at 100% conversion at a temperature of 553 K, a space time (W/F) of 40 g-cat/g-mol methanol per hour and a molar ratio (R) of 0.04 mol CH3 OH/mol air. The rate expression r=k1P2M 1+k1P2M2k 2PO2 was deduced assuming a steady-state involving two-stage irreversible oxidation-reduction process. It represented the experimental data satisfactorily. Arrhenius plots of the two rate constants gave activation energies of 31.7 and 18.1 kcal/g-mol.
Download or read book Sustainable Hydrogen Production written by Ibrahim Dincer and published by Elsevier. This book was released on 2016-08-05 with total page 494 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sustainable Hydrogen Production provides readers with an introduction to the processes and technologies used in major hydrogen production methods. This book serves as a unique source for information on advanced hydrogen generation systems and applications (including integrated systems, hybrid systems, and multigeneration systems with hydrogen production). Advanced and clean technologies are linked to environmental impact issues, and methods for sustainable development are thoroughly discussed. With Earth's fast-growing populations, we face the challenge of rapidly rising energy needs. To balance these we must explore more sustainable methods of energy production. Hydrogen is one key sustainable method because of its versatility. It is a constituent of a large palette of essential materials, chemicals, and fuels. It is a source of power and a source of heat. Because of this versatility, the demand for hydrogen is sure to increase as we aim to explore more sustainable methods of energy. Furthermore, Sustainable Hydrogen Production provides methodologies, models, and analysis techniques to help achieve better use of resources, efficiency, cost-effectiveness, and sustainability. The book is intellectually rich and interesting as well as practical. The fundamental methods of hydrogen production are categorized based on type of energy source: electrical, thermal, photonic, and biochemical. Where appropriate, historical context is introduced. Thermodynamic concepts, illustrative examples, and case studies are used to solve concrete power engineering problems. - Addresses the fundamentals of hydrogen production using electrical, thermal, photonic, and biochemical energies - Presents new models, methods, and parameters for performance assessment - Provides historical background where appropriate - Outlines key connections between hydrogen production methods and environmental impact/sustainable development - Provides illustrative examples, case studies, and study problems within each chapter
Download or read book The Oxidation of Methanol with Air Over Oxide Catalysts written by Wesley Rasmus Peterson and published by . This book was released on 1929 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt:
