New Data on the Ability of Alumina–Platinum Systems to Catalyze the Methane Aromatization Reaction under Nonoxidizing Conditions

The state and size of the metal on the surface of aluminum oxide and the acidic properties of the support depending on the concentration of supported platinum were studied in this work. The effect of the Pt content of the alumina–platinum catalyst on the activation (chemisorption) of methane was investigated, and the composition of hydrocarbon fragments formed in this case was calculated. The sample most active in a reaction of the joint conversion of methane with n-pentane, which was performed for the production of aromatic hydrocarbons under nonoxidizing conditions, was established. The effect of the temperature of n-pentane supply to the reaction atmosphere was studied for the 0.6%Pt/Al₂O₃ catalyst. The degree of enrichment of the resulting aromatic hydrocarbons and the quantity of incorporated methane activated on the catalyst surface were determined with the use of isotope mass spectrometry.     

Methane Direct Conversion on Mo/ZSM-5 Catalysts Modified by Pd and Ru

The effect of addition of Ru and Pd to Mo/HZSM-5 catalysts used in the dehydroaromatiza-tion of methane was investigated. Catalytic tests and temperature-programmed oxidation results showed that Pd-based catalysts were more selective to naphthalene and suffered strong deactivation. The presence of Ru improved the activity and stability, with a decrease in the carbonaceous deposit probably because of a mechanism of protection of the Mo2C surface.     

Copper-Containing Catalysts Based on Cerium–Zirconium Oxide Supports in Ethanol Conversion Reaction According to In Situ IR Spectroscopic Data

Kinetics and Catalysis - Copper-containing catalysts based on CeO2–ZrO2 solid solutions were prepared by the Pecini method and studied using a set of physicochemical methods. It was found...     

Modified Ceria-Zirconia Fluorite-Like Catalysts for the Combustion of Methane

For dispersed ceria-zirconia-based solid solutions prepared via the polymerized complex method and annealed at 700℃, effects of bulk doping by Ca, Mn, Co, Bi or Nb cations and surface modification by Mn and Pt on their structural features, surface/bulk oxygen reactivity and catalytic activity in methane combustion are considered. With up to 20 mol% doping, a structural type of homogeneous solid solutions of anion-deficient fluorite with disordered anion vacancies is formed. Doping by transition metal cations or Pt increases the mobility and reactivity of the surface/bulk oxygen. A broad variation in specific rates of methane combustion for the studied systems was observed, suggesting structural sensitivity of this reaction. In general, there is no universal relationship between the oxygen mobility, the reactivity and the catalytic activity in methane combustion, which is explained by the factor of specific methane activation on surface active sites. For the Pt-promoted samples, Pt efficiency in methane activation depends on the Pt-support interaction, and the most favorable ones being mixed Pt/MnOx and Pt/NbOx clusters on the surface of the supports that exhibit high lattice oxygen mobilities.     

Complete Oxidation of Methane Alumina Modified with Calcium, over Palladium Supported on Lanthanum, and Cerium Ions

The activity and thermal stability of Pd/Al2O3 and Pd/（Al2O3＋MOx） （M=Ca, La, Ce） palladium catalysts in the reaction of complete oxidation of methane are presented in this study. The catalyst supports were prepared by sol-gel method and they were dried either conventionally or with supercritical carbon dioxide. Then they were impregnated with palladium nitrate solution. The catalysts with unmodified alumina had a high surface area. The activity and thermal stability of the aluminasupported catalyst was also very high. The introduction of calcium, lanthanum, or cerium oxide into alumina support caused a decrease of the surface area in the way dependent on the support precursor drying method. These modifiers decreased the activity of palladium catalysts, and they required higher temperatures for the complete oxidation of methane than unmodified Pd/Al2O3. The improvement of the palladium activity by lanthanum and cerium support modifier was observed only at low temperatures of the reaction.     

Complete Oxidation of Methane over Palladium Supported on Alumina Modified with Calcium,Lanthanum,and Cerium Ions

The activity and thermal stability of Pd/Al_2O_3 and Pd/(Al_2O_3 MO_x)(M=Ca,La,Ce) palladium catalysts in the reaction of complete oxidation of methane are presented in this study.The catalyst supports were prepared by sol-gel method and they were dried either conventionally or with supercritical carbon dioxide.Then they were impregnated with palladium nitrate solution.The catalysts with unmodified alumina had a high surface area.The activity and thermal stability of the alumina- supported catalyst was also very high.The introduction of calcium,lanthanum,or cerium oxide into alumina support caused a decrease of the surface area in the way dependent on the support precursor drying method.These modifiers decreased the activity of palladium catalysts,and they required higher temperatures for the complete oxidation of methane than unmodified Pd/Al_2O_3.The improvement of the palladium activity by lanthanum and cerium support modifier was observed only at low temperatures of the reaction.     

The Dehydrogenation of Propane on Platinum–Tin Glass-Fiber Woven Catalysts

The reaction of propane dehydrogenation on platinum–tin catalysts supported onto different woven carriers (an aluminoborosilicate and two silica materials) was studied. It was found that the catalyst was rapidly deactivated by carbon deposits formed, and the rate of this reaction increased with the specific surface area of the glass-fiber woven material and the Pt content. It was established that the Pt: Sn ratio in surface platinum particles was about 6, and it increased to 39 after the reaction; this fact is indicative of a Sn loss, which led to an increase in the conversion of feed into carbon deposits that deactivated the catalyst. A mixture of propane and 5–10 vol % H₂ should be used for the stabilization of the catalytic system; in this case, the negative effect of hydrogen on the yield of propylene was minimal. On the catalyst supported onto a silica carrier under optimum conditions (550°C; propane space velocity, 480 h^–1), which correspond to minimum selectivity for the formation of carbon deposits, the yield of propylene was ~18%. The test glass-fiber woven catalyst was inferior to granulated platinum–tin catalysts in terms of catalytic activity; therefore, its use in the reaction of propane dehydrogenation is inexpedient.     

Effects of Alkali Element Doping and Synthesis Conditions on the Genesis of the Phase Composition of Alumina–Chromium Catalysts

Kinetics and Catalysis - The influence of modifying additives and synthesis conditions on the genesis of the phase composition of alumina–chromium catalysts was studied by differential...     

Effect of the Structure and Size Factor on the Catalytic Properties of Cobalt–Zirconium Oxide Nanoparticles in Deep Oxidation of Methane

We have used X-ray phase analysis, transmission electron microscopy, and temperature-programmed reduction to study cobalt–zirconium catalysts. The most active samples are characterized by higher dispersity of both the support (L = 12-13 nm) and the active component (L 3 nm); modification of the zirconium dioxide with yttrium oxide increases the thermal stability of the catalysts. We have shown that the activity of the catalysts is determined by both the strength of oxygen–catalyst binding and the acidic properties of the catalyst surface.     

Mixed Platinum–Nickel Catalysts of Oxygen Reduction

Russian Journal of Electrochemistry - A mixed catalyst based on platinum and nickel oxide was obtained as a result of the synthesis and subsequent alkaline hydrolysis of thin polymer films of...     

Electrochemical Hydrogenation of α-Arylvinylphosphonic Acids on Platinum and Palladium Modified with Adatoms

A general characteristic of cathodic reduction of -phenylvinylphosphonic acid and its methyl- and chloro-parasubstituted derivatives on Pt/Pt, Pd/Pt, and Pd/Pt modified with Cd and Cu adatoms, is given. At effective pressures of about 10³–10⁴ Pa the processes occur at high rates and at some potentials are limited by the reactant diffusion from the bulk solution. In the presence of Cd and Cu adatoms two reduction waves (presumably, single-electron) may be isolated, i.e. the hampering by adatoms is more pronounced for a second successive stage of the process. At low effective hydrogen pressures the hydrogenation rate is higher on Pd electrodes, which possess a larger sorption capacity. Potential intervals where the reduction of substituted reactants may be complicated by destruction, are found. It is shown that -phenylvinylphosphonic acid undergoes a complete reduction with a current efficiency of 100% in both hydrochloric- and sulfuric-acid solutions. Conditions where the reduction of -(4-chlorophenyl)vinylphosphonic acid proceeds largely without destruction are found. Prospects for use of electrochemical reduction as a preparative method of a selective production of -arylethylphosphonic acids are considered.     

Study on Bifunctionality of Mo/HZSM-5 Catalysts for Methane Dehydro-Aromatization under Non-oxidative Condition

The optimum Mo/[H~+] ratio per unit cell of the active precursors in Mo/HZSM-5 catalysts for methane dehydro-aromatization, measured by 1H MAS NMR, was found to be about 1 when adjusting the acid sites by altering either the SiO2/Al2O3 ratios or the Mo loading. This implies that a concerted interaction between the Mo species and the Bronsted acid sites probably features the bifunctionality of the Mo/HZSM-5 catalyst. On the other hand, it was found that the driving force for Mo species to move into the HSZM-5 zeolite channels and the interaction between the Mo species and the Bronsted acid sites are closely and proportionably related with the amount of Bronsted acid sites per unit cell.     

Voltammetric Study and Detection of Methane on Nickel Hydroxide–Modified Nickel Electrode

Abstract

The nickel hydroxide–modified nickel (NMN) electrode was prepared by cyclic voltammetry. The modified electrode exhibited better catalytic effect toward electrochemical oxidation of methane in 1.0 mol · L^?1 NaOH solution. The catalytic activation of nickel hydroxide on the nickel electrode surface was investigated in different supporting electrolyte solutions by the cyclic voltammetry method in detail, and the related electrochemical oxidation of methane at the NMN electrode was first proposed by amperometric i‐t curve method under the experiment conditions. The results indicated that in the 1.0 mol · L^?1 NaOH solution, the anodic peak current increased with the increased concentration of methane.     

Nanostructured Catalysts of Methanol Electrooxidation Based on Platinum–Ruthenium–Palladium and Platinum–Ruthenium–Iridium Alloys Derived from Coordination Compounds

Russian Journal of Coordination Chemistry - Activities of the synthesized trimetallic catalysts PtRuPd/C and PtRuIr/C supported on highly dispersed carbon soot from solutions of coordination...     

A Study of the Electrochemical Characteristics of Single-Chamber Solid Oxide Fuel Cells Based on Platinum and Strontium-Doped Lanthanum Manganite Electrodes and Fed with a Methane–Air Mixture

Kinetics and Catalysis - The properties of single-chamber solid oxide fuel cells (SC SOFCs) composed of an electrolyte based on yttria-stabilized zirconia (YSZ), a platinum anode, and a...     

Microcalorimetric Adsorption of Alumina Oxide Catalysts for Combination of Ethylbenzene dehydrogenation and carbon Dioxide Shift-reaction

Styrene (STY) is now produced industrially in fairly large quantities by the dehydrogenation of ethylbenzene (EB) using promoted iron oxide catalyst with superheated steam. In this case, small amount of carbon dioxide formed as a by-product was known to inhibit the catalytic activity of commercial catalyst. Recently, there have been some reports which carbon dioxide showed positive effects to promote catalytic activities on the reaction over several catalysts. In this study, we attempted to …     

Influence of Method of Introduction of Cu- and Zn-Based Modifiers on the Properties of Chromia–Alumina Catalysts

Three methods of introduction of modifiers based on Cu and Zn compounds into the CrO_x/Al₂O₃ catalysts for dehydrogenation of light paraffin hydrocarbons are considered: Introduction from sol, introduction using successive impregnation technique and introduction of modifiers by impregnation along with precursor of chromium oxide. The obtained samples are studied by a complex of physical-chemical methods (XRD, UV-Vis spectroscopy, temperature-programmed reduction with hydrogen (TPR-H₂), X-ray fluorescent (XRF) spectrometry, low-temperature N₂ sorption). The catalytic properties of the samples are studied in kinetic mode in isobutane dehydrogenation. Cu- and Zn-modifiers are shown to influence on the peculiarities of reduction of Cr⁶⁺ and, hence, specify the state of active surface of CrO_x/Al₂O₃ catalysts formed in the reductive reaction medium. Not only do the states of modifiers influence on the initial activity of the catalyst, but also on its activity after oxidative regeneration. Introduction of modifiers by successive impregnation method results in formation of copper and zinc aluminates or defective spinels on the Al₂O₃ surface. When the active component is introduced, the modified surface of the support promotes formation and stabilization of Cr⁶⁺ sites that can undergo reversible reduction–oxidation and provide high activity and selectivity towards formation of isobutylene (>98%).