scholarly journals Ag-Based Catalysts in Heterogeneous Selective Oxidation of Alcohols: A Review

Catalysts ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 447 ◽  
Author(s):  
Viktoriia V. Torbina ◽  
Andrei A. Vodyankin ◽  
Sergey Ten ◽  
Grigory V. Mamontov ◽  
Mikhail A. Salaev ◽  
...  
Keyword(s):  
Heterogeneous Catalysts ◽  
Active Component ◽  
Ambient Air ◽  
Sustainable Technologies ◽  
Oxidation Of Methanol ◽  
Catalyst Composition ◽  
Oxidation Of Alcohols ◽  
Metal Support ◽  
Allyl Alcohols ◽  
Conversion Of Alcohols

Alcohols (bioalcohols) is a class of chemicals that are used as a feedstock for the manufacturing of a large number of valuable intermediates in industrially important processes. Currently, sustainable technologies for selective conversion of alcohols utilize “green” oxidants, mainly, ambient air or oxygen. Due to the high affinity of oxygen towards silver, the latter serves as an active component of supported heterogeneous catalysts. In this review, we consider Ag-based catalysts that participate in gas- or liquid-phase oxidation of alcohols. Oxidation of methanol, ethanol, ethylene glycol, propylene glycol, glycerol, benzyl and allyl alcohols is mostly considered. A particular attention is paid to selective photooxidation of alcohols over Ag-based catalysts. We discuss the catalyst composition in terms of (1) the state of the active component, (2) the nature of the substrate, (3) support nature, and (4) the strength of the metal–support interactions.

scholarly journals Enhancement of oxidation of dimethyl ether through application of zirconia matrix for immobilization of noble metal catalytic nanoparticles

2020 ◽  
Vol 24 (11-12) ◽  
pp. 3173-3183
Author(s):  
Iwona A. Rutkowska ◽  
Jakub P. Sek ◽  
Piotr Zelenay ◽  
Pawel J. Kulesza
Keyword(s):  
Dimethyl Ether ◽  
Cyclic Voltammetric ◽  
Oh Groups ◽  
Onset Potential ◽  
Oxidation Of Methanol ◽  
Catalytic Nanoparticles ◽  
Catalytic Sites ◽  
Metal Support ◽  
Current Densities ◽  
Metal Support Interactions

Abstract Electrocatalytic activity of Pt and bimetallic PtRu nanoparticles (both Vulcan supported and unsupported) toward electrooxidation of dimethyl ether (DME), a potential small organic molecule fuel, in an acid medium (0.5 mol dm−3 H2SO4) has been significantly enhanced by dispersing them over a thin film of zirconia (ZrO2). The enhancement effects concern increases of the DME electrocatalytic current densities recorded under both cyclic voltammetric and chronoamperometric conditions. Similar effects have been observed for the oxidation of methanol. Regarding the dissimilar DME electrooxidation mechanisms at Pt and PtRu catalytic centers, the activating capabilities of zirconia seem to originate from the high population of reactive –OH groups favoring mobility of protons and the capability of inducing the oxidative removal of poisoning (CO-type) intermediates both at platinum and ruthenium catalytic sites. In the presence of the zirconia matrix, the onset potential for the oxidation of DME (particularly at PtRu) is shifted more than 50 mV toward less positive potentials. Mutual metal-support interactions are also postulated.

scholarly journals Aplicação de óxidos mistos de molibdênio, vanádio, tungstênio e cobre como catalisadores na produção do ácido acrílico

2020 ◽  
Author(s):  
◽  
W. M. Fantim
Keyword(s):  
Block Copolymer ◽  
Acrylic Acid ◽  
Hydrothermal Treatment ◽  
Crystalline Phase ◽  
Heterogeneous Catalysts ◽  
Raw Material ◽  
Oxide Content ◽  
Propene Oxidation ◽  
Synthesis Conditions ◽  
Catalyst Composition

Acrylic acid is a product with several applications in the chemical industry, the main one is the production of sodium polyacrylate, a superabsorbent material used in the toiletries manufacture. Currently acrylic acid is obtained from propene oxidation using heterogeneous Mo/Bi and Mo/V oxide-based catalysts. In this process, propene is first oxidized to acrolein, which is then oxidized to acrylic acid. Although this is already a consolidated process, propylene comes from petrochemical sources and thus there is a concern to search for alternative routes to the use of this raw material and one of the possibilities is to synthesize acrolein from glycerol dehydration using specific catalysts. For the project, heterogeneous catalysts were prepared to obtain the acrylic acid, first evaluated in the oxidation of acrolein and later in the glycerol oxideshydration. Three types of samples were synthesized with different compositions B1- Mo12V4,8W2,4Cu2,2Si8,4; B2-Mo12V2W0,5Si6,2 and B3-Mo12V2,7Si6,2) by four preparation methods, namely by evaporation, evaporation followed by hydrothermal treatment, hydrothermal treatment (TH) and using a block copolymer. For the last two methods a more detailed study was performed to determine the best synthesis conditions (Phase I), and it was found that the total dissolution of the reagents in the mixture before TH resulted in samples with higher crystallinity and less active phase loss in the liquid and the use of a cold dissolved block copolymer contributed to an increase in pore volume. In the second stage, the materials synthesized by the four proposed methods were characterized and evaluated in reactor in acrylic acid production. The samples B1 showed different crystalline phase formation depending on the preparation method used, and in samples B2 and B3 the main phase was identified as a-MoO3, regardless of the method used. The samples synthesized by evaporation followed by TH showed the highest selectivity for acrylic acid formation from acrolein for the same catalyst composition, which may be related to the higher vanadium oxide content present in samples identified by FRX and the formation of the crystalline phase V0.35Mo4,65O14. The best performance was observed in sample B1-EV+TH with selectivity of 50.59% and 3.61% for acrylic acid in the processes from acrolein and glycerol, respectively

scholarly journals COMBINATORIAL SYNTHESIS AND REACTIVITY SCREENING OF ELECTRO-OXIDATION CATALYST GRADIENTS

2003 ◽  
Vol 804 ◽  
Author(s):  
Shrisudersan Jayaraman ◽  
Andrew C. Hillier
Keyword(s):  
Heterogeneous Catalysts ◽  
Surface Composition ◽  
Hydrogen Oxidation ◽  
Oxidation Catalyst ◽  
Composition Gradient ◽  
Polymer Gel ◽  
Hydrogen Oxidation Reaction ◽  
Catalyst Composition ◽  
Composition Space ◽  
Combinatorial Methods

ABSTRACTCombinatorial methods represent an appealing experimental method for the discovery of heterogeneous catalysts. One can efficiently identify candidate materials or sample vast regions of composition space using a combination of dense catalyst libraries and high-throughput reactivity screening techniques. This is particularly appealing for the discovery of novel catalysts for low temperature fuel cells where multi-component systems have shown improved performance. For example, the poison tolerance of typical anode catalysts can be improved by the addition of oxophilic components such as ruthenium, molybdenum, tin or osmium. Consequently, a vast composition space must be sampled in order to identify catalyst compositions or regions of composition space with greater activity. Combinatorial methods represent a practical means to speed-up the catalyst discovery process. In this manuscript, we demonstrate a novel method for combinatorial catalyst discovery based upon the synthesis and reactivity mapping of catalyst composition gradients. Samples consisting of uniform variations in surface composition of metals catalysts (Pt-M1 and Pt-M1−M2, where M1, M2 = Ru, Mo, Sn or Os) are fabricated using a gel-transfer technique. A concentration gradient of source metal ions is produced in a swollen polymer gel and then transferred onto a surface by electrodeposition to create a continuous composition gradient. An in situ reactivity-mapping tool based on the scanning electrochemical microscope is used to interrogate these catalyst gradients for the hydrogen oxidation reaction in the presence of adsorbed carbon monoxide.

Growth of graphite nanofibers from the decomposition of CO/H2 over silica-supported iron–nickel particles

1999 ◽  
Vol 14 (7) ◽  
pp. 2912-2921 ◽  
Author(s):  
P. E. Anderson ◽  
N. M. Rodriguez
Keyword(s):  
Amorphous Carbon ◽  
Iron Content ◽  
Degree Of Crystallinity ◽  
High Iron Content ◽  
Temperature Programmed Oxidation ◽  
Nickel Iron ◽  
Graphite Nanofibers ◽  
Catalyst Composition ◽  
Metal Support Interaction ◽  
Metal Support

Extremely fine, tubular graphite nanofibers of varying geometries and degrees of crystallinity were produced by the decomposition of CO and hydrogen over various compositions of nickel–iron particles supported on silica. High-resolution transmission electron microscopy coupled with temperature programmed oxidation studies revealed that, as the iron content of the catalyst was increased, the bimetallic particles precipitated a chainlike graphitic fibrous structure in a stepwise mechanism. The high-iron-content system Fe–Ni (8:2) yielded a small amount of these chainlike graphite fibers that were extremely resilient to oxidation, suggesting a highly crystalline structure. When the catalyst particles consisted of a nickel–iron mixture, Fe–Ni (5:5), there was a decrease in the degree of crystallinity of the fibers (78% graphite) and a corresponding increase in the amount of amorphous carbon precipitated (22% amorphous) within the structure. The high-nickel catalyst Fe–Ni (2:8) generated the largest amount of the tubular nanofiber product. It was significant that there was an increase in the amorphous carbon content (58%) precipitated as opposed to graphitic carbon (42%) in the structures. In some cases, amorphous carbon was deposited inside the graphite core of the nanofibers. The influence of the catalyst composition and nature of the metal-support interaction are key factors in the continuing development of graphite nanofibers possessing desired structures for potential uses in a variety of applications.

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