Download or read book Methanol Oxidation Over Copper and Silver Monometallic and Bimetallic Supported Catalysts written by and published by . This book was released on 2015 with total page 366 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 Methanol Oxidation Over Palladium and Silver Catalysts written by James Maximuck and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Direct methanol fuel cells (DMFCs) are a viable replacement for batteries because methanols high energy density and ability to be stored easily at room temperature makes it feasible as an energy source in small, portable electronic devices. However, experimental setbacks with poor efficiency and low power density have slowed progress towards industrial use of DMFCs. In attempts to find the ideal metallic catalyst for methanol oxidation, experimental data has revealed that palladium catalysts oxidize alcohols more efficiently than silver catalysts, but silver oxidizes aldehydes (a potential intermediate in alcohol oxidation) much more efficiently than palladium does. Using computational methods in conjunction with density functional theory (DFT), we have analyzed the binding sites and energies of all of the intermediates of alcohol oxidation on both palladium and silver catalysts in an electrochemical environment in order to elucidate the reaction pathway. Our results have reinforced that although palladium is more active because adsorbates bind more strongly to the palladium surface, carbon monoxide poisoning has a more significant effect on palladium than silver. Bimetallic catalysts of different compositions of silver and palladium were analyzed, and the results show that doping in silver to a palladium surface decreases the strength of carbon monoxide binding to the surface while maintaining similar favorable binding energies to a pure palladium surface for other intermediates. This may explain the experimentally measured high activity of palladium-silver alloys for methanol oxidation relative to that of the pure metals.

Download or read book The Kinetics of Methanol Oxidation on a Supported Silver Catalyst written by David Alan Robb and published by . This book was released on 1973 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Selective Oxidation of Hydrocarbons Using Supported Gold Silver Copper and Bimetallic Catalysts written by Yi-Jun Xu and published by . This book was released on 2006 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Partial Oxidation of Methanol Over Supported Copper Catalysts written by Reza Torbati Rajaie and published by . This book was released on 2000 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Model Studies of Methanol Selective Oxidation Over Copper Catalysts written by Ling Zhou and published by . This book was released on 2005 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Surface Organometallic Chemistry Molecular Approaches to Surface Catalysis written by Jean-Marie Basset and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 340 pages. Available in PDF, EPUB and Kindle. Book excerpt: Surface organometallic chemistry is a new field bringing together researchers from organometallic, inorganic, and surface chemistry and catalysis. Topics ranging from reaction mechanisms to catalyst preparation are considered from a molecular basis, according to which the "active site" on a catalyst surface has a supra-molecular character. This. the first book on the subject, is the outcome of a NATO Workshop held in Le Rouret. France, in May. 1986. It is our hope that the following chapters and the concluding summary of recommendations for research may help to provide a definition of surface organometallic chemistry. Besides catalysis. the central theme of the Workshop, four main topics are considered: 1) Reactions of organometallics with surfaces of metal oxides, metals. and zeolites; 2) Molecular models of surfaces, metal oxides, and metals; 3) Molecular approaches to the mechanisms of surface reactions; 4) Synthesis and modification of zeolites and related microporous solids. Most surface organometallic chemistry has been carried out on amorphous high-surf ace-area metal oxides such as silica. alumina. magnesia, and titania. The first chapter. contributed by KNOZINGER. gives a short summary of the structure and reactivity of metal oxide surfaces. Most of our understanding of these surfaces is based on acid base and redox chemistry; this chemistry has developed from X-ray and spectroscopic data, and much has been inferred from the structures and reactivities of adsorbed organic probe molecules. There are major opportunities for extending this understanding by use of well-defined (single crystal) oxide surfaces and organometallic probe molecules.

Download or read book An Investigation Into the Structure and Activity of Monometallic and Bimetallic Copper and Gold Catalysts for Propene Oxidation written by Charlotte Louise Bracey and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: CuAu/SiO2 catalysts were prepared in a number of ways, the main route being incipient wetness impregnation, but other methods, like deposition precipitation and high dispersion, were also used. Bimetallic and monometallic catalysts were prepared for this investigation and most were characterised by various techniques such as XRD, SEM, TPR, BET, UV visible and TEM. Theoretical and characterisation studies of CuAu catalysts have generated considerable interest. However, little research has been carried out on their catalytic activity. Therefore, propene oxidation was chosen as the principal reaction, as it was previously examined by Chimentao and group.1 This study showed that the reduction of the catalysts in H2/Ar was fundamental to alloy formation. The most active catalyst was made by a sequential procedure that deposited the copper onto the silica support by high dispersion, followed by depositing gold onto the support by deposition precipitation. The catalyst was then treated by a Sinfelt thermal treatment which involved a reduction in H2/Ar at 315oC for 2h followed by a high temperature calcination at 676oC in air for 15h. Propene oxidation was performed in the presence of hydrogen and a propene conversion of 10% was observed at 320oC, with a selectivity towards acrolein (90%) and some carbon dioxide (10%). The purpose of this study was to obtain an understanding of the nature of these CuAu/SiO2 catalysts and to determine if there were any relationship towards their activity for propene oxidation.

Download or read book Monometallic and Bimetallic Catalysis for C1 C4 Alkane and Propylene Total Oxidation written by Garam Lee and published by . This book was released on 2017 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this work, we used small alkanes (methane, ethane, propane, and isobutene), as probe molecules for larger alkanes, and propylene, as a representative of alkene, in total oxidation. The catalytic activity of seven monometallic (Pt, Pd, Rh, Ag, Ni, Cu, and Co/Al2O3) and three compositions (1:3, 3:1, and 1:10) of Ag-Pd/Al2O3 bimetallic catalysts is evaluated for the total oxidation of C1-C4 alkanes in the temperature range of 280-400 °C. In oxygen rich conditions (equivalence ratio of 0.5), volcano-type dependences of the turnover frequency (TOF) on the C and O binding energy are observed for all small alkanes tested; Pt/Al2O3 is the most active among monometallic catalysts, and 1:3 Ag-Pd bimetallic exhibits superior activity compare to the most active Pt/Al2O3 catalyst in the oxidation of ethane and higher alkanes, while Pt shows superior activity in methane oxidation. For fuel rich conditions (equivalence ratio of 2), volcano-type relation of the TOF on the C and O binding energy for methane is different from C2-C4 alkanes; among monometallic catalysts, Pd/Al2O3 is the most active in methane oxidation, while Pt/Al2O3 is the most active in C2-C4 alkane oxidation. We also show that in propane oxidation over Pt/Al2O3, Pd/Al2O3, and Ag- Pd/Al2O3, there are three distinct kinetic regimes in which the TOF is (1) first order, (2) negative order, and (3) zero order with respect to oxygen concentration. Hysteresis with respect to oxygen concentration is also observed. ☐ In order to understand the reaction order shift in methane oxidation under different reaction conditions, the kinetics of methane oxidation over Pt/Al2O3, Pd/Al2O3, and Ag-Pd/Al2O3 is investigated as a function of O2/CH4 ratio at 340 ̊C. We show that as the oxygen fraction increases from low values, three distinct kinetic regimes exist that are (1) nearly first order, (2) negative order, and (3) zero order with respect to the oxygen concentration. At O2/CH4

Download or read book Performance of Ceria Supported Monometallic and Bimetallic Single atom Catalysts in Carbon Monoxide Oxidation written by Nicholas A. Pantelis and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Research into atomically-dispersed metal catalysts on metal-oxide supports like ceria and alumina has grown significantly due to these catalysts' increased performance relative to bulk, nanoparticle, and sub-nanometer metal catalysts. Atomically dispersed, single atom catalysts have been shown to increase the specific activity of metal catalysts on metal-oxide supports. This study mainly focuses on difference in kinetic behavior of single-atom palladium, platinum, and nickel adatoms supported on ceria support during the oxidation of carbon monoxide. The relationship between metal weight-loading on a ceria support, reactor temperature, and reaction order was described. Bimetallic single atom catalysts of palladium and platinum on ceria were studied to compare to monometallic systems in terms of activity. Catalysts were characterized using ICP and CO-DRIFTS analysis, and a differential packed-bed reactor was used carry out the oxidation reaction; the effluent stream was analyzed using a GC to determine reaction kinetics. It was determined that CO binds most strongly to Pt, followed by Pd, and then Ni. The transition from single atom to sub-nanometer nanoparticles or nanoparticles shows a decrease in specific activity with increasing weight loading. At relatively larger weight loadings, for each metal, the order in CO transitions from above 1 to 0 (or slightly negative), while the order in O2 transitions from slightly negative or 0 to above 1. Pd, Pt, and Ni, at similar nominal weight loadings, have similar activities in different temperature ranges; this observation shows CO poisons the metal site but does not explain why at low weight loadings the order in CO increases above 1. Binding energies between metals and ceria as well as metal and CO may explain this observation. Bimetallic Pd/Pt catalysts seem to show apparent synergy due to the fact that the activation energy decreases well below the activation energy of monometallic systems of Pd and Pt.

Download or read book Synthesis Characterization and Catalytic Activity of Silica Supported Bimetallic Copper Catalysts for Organic Oxidation Reactions and the Study of Benzylation of Triketones written by Nuwan Dileepa De Silva and published by . This book was released on 2013 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: The dissertation describes research work on development of bimetallic heterogeneous catalysts for oxidation of organic compounds. Binuclear metal complexes are an interesting class of compounds due to their catalytic activity. The approach involves anchoring a triketone ligand to Cab-O-Sil via a linker. Specifically, silica gel was allowed to react with p-chloromethylphenyltrimethoxysilane followed by coupling with deprotonated triketone compounds. The viability of this approach was verified by performing the benzylation reaction of triketones with benzyl halides under basic conditions. The benzylation of 2,4,6-heptanetrione and 1,5-diphenyl-1,3,5-pentanetrione is achieved with benzyl bromide using n-tetrabutylammonium fluoride as base. These benzylation reaction conditions were used to attach the triketones to the surface-attached linker. Once the ligand is attached to the silica gel, the catalyst is formed by coordinating two copper(II) ions from solution to the deprotonated triketone. The coordination of copper(II) ions to the triketone was monitored using UV-vis spectroscopy. The modified silica gel is characterized by diffuse reflectance infrared Fourier spectroscopy (DRIFTS), and thermal gravimetric analysis (TGA) at the different stages of catalyst formation. All techniques indicated significant attachment of linker and triketone to the support. The oxidation of 3,5-di-tert-butyl catechol (DTBC) and benzyl alcohol was carried out under aerobic conditions using these catalysts. The kinetics of the DTBC oxidation and benzyl alcohol oxidation was studied using bimetallic and monometallic catalytic systems. The copper complexes of the triketone ligands were also evaluated as catalysts for the oxidation of DTBC. New bimetallic metal complexes with triketone ligands having a benzyl group were synthesized and characterized by high resolution mass spectroscopy and IR spectroscopy. In addition to a detailed description of the synthesis and characterization of new triketone compounds, and the heterogeneous catalyst systems, a comparison of the kinetics of the oxidation of DTBC using these catalysts will be discussed.

Download or read book Nanocatalysis written by Vanesa Calvino-Casilda and published by CRC Press. This book was released on 2019-02-14 with total page 241 pages. Available in PDF, EPUB and Kindle. Book excerpt: Synthesis and design of new nanocatalysts is an important area of research that aims to introduce multiple types of useful applications in a greener market. The necessity of nanostructuring the active sites has emerged as the key point in a successful design of the catalysts. The book covers the progress in this research area done in the last ten years. It includes the classification of catalysts and structure of active sites at the nanoscale. The book covers examples to present the concept, evolution of nanocatalysts from the perspective of chemistry of materials and their applications.

Download or read book Selective Oxidation of Hybrocarbons Using Supported Gold Silver Copper and Bimetallic Catalysts written by Yi-Jun Xu and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Direct Anodic Oxidation of Methanol on Supported Platinum ruthenium Catalyst in Aqueous Cesium Carbornate written by Bruce Robert Rauhe and published by . This book was released on 1992 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Partial Oxidation Reactions on Supported Silver Monolith Catalyst written by Zhilei Wang and published by . This book was released on 1996 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Catalysts for Alcohol fuelled Direct Oxidation Fuel Cells written by Zhen-Xing Liang and published by Royal Society of Chemistry. This book was released on 2012 with total page 265 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents a state-of-the-art review on recent advances in nanocatalysts and electrocatalysis in DOFCs.