Pattern of the Activity of (0.5–15)%CoO/CeO2 Catalysts in Carbon Monoxide Oxidation with Oxygen in Excess Hydrogen

Kinetics and Catalysis - Samples of (0.5–15)%CoO/CeO2, Co3O4, and CeO2 have been studied in the oxidation of CO to CO2 in a CO+O2+H2 mixture in a range of 40–340°C. The highest...     

The Effect of the Copper Oxide Content and Support Structure in (0.5−15%)СuО/ZrO<Subscript>2</Subscript> Catalysts on Their Activity in the CO Oxidation Reaction with Oxygen in an Excess of Hydrogen

The dependence of the activity of СuO/ZrO₂ catalysts in the CO oxidation reaction with oxygen in the presence of an excess of hydrogen and adsorption of СО over them on the CuO content (0.5 to 15%) and the structure of the support ZrO₂, monoclinic (М), tetragonal (Т), or mixed (М + Т) has been studied. It has been found that the activity of CuO/ZrO₂ is associated with the adsorption capacity of the samples for СО at 20°С. Thus, 5%CuO/ZrO₂(Т + М) and 5% CuO/ZrO₂(Т) samples, which exhibit the maximum activity (the СО conversion over them is 80–85% at 160°С), also possess a high chemisorption capacity towards CO (~2.2 × 10²⁰ molecules/g). At the same time, CuO/ZrO₂(М) samples with the CuO contents of 1 and 5% do not chemisorb СО and are inactive in the reaction at 160°С. The СО conversion over them does not exceed 32–36% at 250°С. On the basis of the data obtained by X-ray phase analysis, temperature-programmed reduction with Н₂, temperature-programmed СО desorption, and electron paramagnetic resonance, a conclusion has been made that at low temperatures СО oxidation proceeds over Cu_nO_m clusters that are located on ZrO₂(Т) crystallites. With the increase in the copper oxide content from 0.5 to 5%, the activity of the clusters increases, while the reaction temperature decreases. CuO_m oxo complexes and particles of the СuO phase do not exhibit catalytic activity. The reasons for the low activity of the CuO/ZrO₂(М) samples with the CuO contents of 1 and 5% in the СО oxidation and adsorption processes are discussed. The mechanism of the low-temperature СО oxidation with oxygen in an excess of hydrogen over a 5% CuO/ZrO₂(Т + М) catalyst is considered.     

Homogeneous and Polymer-Supported Catalysts in the Oxidation of α-Pinene with Oxygen

The catalytic activities of nitrogen-containing cobalt complexes, polymer (AN-251 anion exchanger)-supported cobalt complex, and a polymer–salt composition containing molybdenum salt and nonionogenic water-soluble polymers were compared in the oxidation of -pinene.     

Chemical Reactions and Kinetics of the Carbon Monoxide Coupling in the Presence of Hydrogen

The chemical reactions and kinetics of the catalytic coupling reaction of carbon monoxide to diethyl oxalate were studied in the presence of hydrogen over a supported palladium catalyst in the gaseous phase at the typical coupling reaction conditions. The experiments were performed in a continuous flow fixed-bed reactor. The results indicated that hydrogen only reacts with ethyl nitrite to form ethanol, and kinetic studies revealed that the rate-determining step is the surface reaction of adsorbed hydrogen and the ethoxy radical (EtO-). A kinetic model is proposed and a comparison of the observed and calculated conversions showed that the rate expressions are of rather high confidence.     

Effect of Catalyst Pretreatment on the Oxidation of Carbon Monoxide over Gold Catalysts Supported on Double Oxides

ＥｆｅｃｔｏｆＣａｔａｌｙｓｔＰｒｅｔｒｅａｔｍｅｎｔｏｎｔｈｅＯｘｉｄａｔｉｏｎｏｆＣａｒｂｏｎＭｏｎｏｘｉｄｅｏｖｅｒＧｏｌｄＣａｔａｌｙｓｔｓＳｕｐｐｏｒｔｅｄｏｎＤｏｕｂｌｅＯｘｉｄｅｓＨＡＯＺｈｅｎｇｐｉｎｇＡＮＬｉｄｕｎ１）ＷＡＮＧＨｏｎ...     

Synthesis and Activity of Nanodispersed SnO2–CeO2 Catalyst in the Oxidation Reactions of Carbon Monoxide and Methane

Kinetics and Catalysis - Nanodispersed SnO2–CeO2 catalysts for the oxidation of CO and СН4 were synthesized by coprecipitation in a water–isopropanol solution followed by...     

Influence of Sulfation on the Catalytic Activity of Ni-ZrO2 for NO Reduction with Propane in Excess Oxygen

Selective catalytic reduction （SCR） of nitric oxide with propane in excess oxygen was investigated on Ni-ZrO2 （NZ） and sulfated Ni-ZrO2 （SNZ）, prepared by coprecipitation from a mixture of nickel nitrate-zirconium oxychloride followed by modifying with （NH4）2SO4. It was found that sulfated Ni-ZrO2 catalyst showed higher activity for the SCR of NO with propane than that of Ni-ZrO2. The structural and surface properties of catalysts were studied by XRD, BET, SEM and FT-IR of pyridine adsorption. The experimental results indicated that the modification of （NH4）2SO4 resulted in the generation of strong BrOnsted and Lewis acid sites and promoted the dispersion of the Ni species, which could lead to higher NO conversion and propane efficiency in NO reduction.     

Activity of Supported Binary Indium–Cobalt Oxide Catalysts in Reduction of Nitrogen(I,II) Oxides with Carbon Monoxide

Russian Journal of Applied Chemistry - Supported binary indium–cobalt oxide catalysts showed high activity in joint reduction of nitrogen(I, II) oxides with carbon monoxide. Their activity is...     

In Situ X-Ray Absorption Spectroscopy Studies of Carbon Monoxide Oxidation in the Presence of Nanocomposite Cu–Fe–Al Oxide Catalysts

Kinetics and Catalysis - Nanocomposite Fe–Al and Cu–Fe–Al oxide catalysts are studied in the CO oxidation reaction. It is shown that the introduction of copper leads to a more...     

Activity Enhancement of Vanadium Catalysts with Ultrasonic Preparation Process for the Oxidation of Sulfur Dioxide

The effect of ultrasonic cavitations on the activity of vanadium catalysts at low temperatures for the oxidation of sulfur dioxide, in which refined carbonized mother liquor had been added, was investigated.Twenty minutes were needed to produce obvious cavitations when the catalyst raw material was treated in the 50 W ultrasonic generator. However, only 10 minutes would be needed in a 150 W ultrasonic generator.The higher the temperature of the wet material, the less time was needed to produce cavitations, and the optimal temperature was 60℃. The water content in the wet material mainly affected the quantity of cavitations. Ls-8 catalyst was prepared using ultrasonic. Its activity for conversion of SO2 reached to 52.5% at 410℃ and 4.2% at 350℃. The differential thermal analyses indicate that both endothermic peaks and exothermic peaks noticeably shifted forward compared with Ls catalyst prepared without ultrasonic, and SEM results show a uniform uore size distribution for Ls-8 catalvst.     

Influence of Pretreatment on the Interaction of Oxygen with Silver and the Catalytic Activity of Ag／SiO2 Catalysts for CO Selective Oxidation in H2

The interactions of oxygen with pre~reduced silver catalysts as well as their catalytic propertiesfor CO selective oxidation in H2 after oxygen pre-treatment are studied in this paper. It is found that the pretreatment exerts a strong influence on the activity and selectivity of the silver catalyst. A drop in activity and selectivity is observed after treating a pre-reduced catalyst with oxygen at low temperatures,whereas a converse result is obtained after an oxidizing treatment at high temperatures (T≥350℃). O2-TPD results show that surface oxygen species adsorbs on silver surface after the oxygen treatment at low temperatures. However, penetration of oxygen into the silver is enhanced by a high temperature treatment, meanwhile the surface oxygen species disappear. No other silver species except metallic silver are observed on all the catalysts by XRD, and the size of silver particle is not changed after the treatment with oxygen at low temperatures. The surface oxygen species formed by oxygen treatment can also be removed by hydrogen reduction. The strongly-adsorbed surface oxygen species prohibit the adsorption and diffusion of oxygen species in reaction gas on the surface of silver catalyst, causing the decrease in CO oxidation activity, in other words, it is important to obtain a clean silver surface for increasing the catalyst activity in CO removal from H2-rich feed gas. The differences in activity and selectivity due to the oxygen pretreatment at different temperatures axe discussed in terms of the changes in the surface/subsurface oxygen species of the silver particles.     

Factors Governing the Activity of α-MnO2 Catalysts in the Oxygen Evolution Reaction: Conductivity versus Exposed Surface Area of Cryptomelane

Cryptomelane (α-(K)MnO₂) powders were synthesized by different methods leading to only slight differences in their bulk crystal structure and chemical composition, while the BET surface area and the crystallite size differed significantly. Their performance in the oxygen evolution reaction (OER) covered a wide range and their sequence of increasing activity differed when electrocatalysis in alkaline electrolyte and chemical water oxidation using Ce⁴⁺ were compared. The decisive factors that explain this difference were identified in the catalysts’ microstructure. Chemical water oxidation activity is substantially governed by the exposed surface area, while the electrocatalytic activity is determined largely by the electric conductivity, which was found to correlate with the particle morphology in terms of needle length and aspect ratio in this sample series. This correlation is rather explained by an improved conductivity due to longer needles than by structure sensitivity as was supported by reference experiments using H₂O₂ decomposition and carbon black as additive. The most active catalyst R-cryptomelane reached a current density of 10 mA cm⁻² at a potential 1.73 V without, and at 1.71 V in the presence of carbon black. The improvement was significantly higher for the catalyst with lower initial activity. However, the materials showed a disappointing catalytic stability during alkaline electrochemical OER, whereas the crystal structure was found to be stable at working conditions.     

Selective Oxidation of CO in Excess H2 over Ru/Al2O3 Catalysts Modified with Metal Oxide

The Ru/Al_2O_3 catalysts modified with metal oxide(K_2O and La_2O_3)were prepared via incipient wetness impregnation method from RuCl_3·nH_2O mixed with nitrate loading on Al_2O3 support. The activity of catalysts was evaluated under simulative conditions for the preferential oxidation of CO (CO-PROX)from the hydrogen-rich gas streams produced by reforming gas,and the performances of catalysts were investigated by XRD and TPR.The results showed that the activity temperature of the modified catalysts Ru-K_2O/Al_2O3 and Ru-La_2O_3/Al_2O_3 were lowered approximately 30℃compared with pure Ru/Al_2O_3,and the activity temperature range was widened.The conversion of CO on Ru-K_2O/Al_2O_3 and Ru-La_2O_3/Al_2O_3 was above 99% at 140-160℃,suitable to remove CO in a hydrogen-rich gas and the selectivity of Ru-La_2O_3/Al_2O_3 was higher than that of Ru-K_2O/Al_2O_3 in the active temperature range. Slight methanation reaction was detected at 220℃and above.     

Trapping of the Dichlorocarbene Intermediate in the Reaction of α-Cyanobenzyl carbanion with Carbon Tetrachloride

Sincein1966KornblumlaandRus,ell,bindependentlyprovidedmechanisticdetailsabouttheSRNIpathwayforthespecificreactionstheyinvestigated,theSingle-ElectronTransfer(SET)chemistryhasresultedinamostexcitingtimeinthehistoryoforganicchemistry.EvidencethatsomenucleophilicsubstitutionswithalkylhandesoccurbySETmechanismhasattractedmuchattentiontothestudyoftherelationshipbetweenSNZandSETpathways.SeveralauthorshavespggestedthatSETandSNZaretwoextremesofahybridmodelforsubstitutionreactions2.Polyhalog…     

LaMn1 – xFexO3 (x = 0–1) Perovskites in Methane and Carbon Monoxide Oxidation Reactions

Kinetics and Catalysis - The LaMn1 – xFexO3 (х = 0–1) perovskites were prepared by the Pechini route and characterized by X-ray diffraction analysis, HR TEM, XPS, and BET. Their...     

Understanding the Activity of Co-N4−xCx in Atomic Metal Catalysts for Oxygen Reduction Catalysis

Atomic metal catalysis (AMC) provides an effective way to enhance activity for the oxygen reduction reaction (ORR). Cobalt anchored on nitrogen-doped carbon materials have been extensively reported. The carbon-hosted Co-N₄ structure was widely considered as the active site; however, it is very rare to investigate the activity of Co partially coordinated with N, for example, Co-N_4−xC_x. Herein, the activity of Co-N_4−xC_x with tunable coordination environment is investigated as the active sites for ORR catalysis. The defect (di-vacancies) on carbon is essential for the formation of Co-N_4−xC_x. N species play two important roles in promoting the intrinsic activity of atomic metal catalyst: N coordinated with Co to manipulate the reactivity by modification of electronic distribution and N helped to trap more Co to increase the number of active sites.     

Plasma-catalytic Selective Reduction of NO with C2H4 in the Presence of Excess Oxygen

This paper reports observations of significant synergistic effects between dielectric barrier discharge (DBD) plasmas and Cu-ZSM-5 catalysts for C2H4 selective reduction of NOx at 250℃ in the presence of excess oxygen by using a one-stage plasma-over-catalyst (POC) reactor. With the reactant gas mixture of 530 ppm NO, 650ppm C2H4, 5.8% 02 in N2and GHSV = 12000h^-1, the pure catalytic, pure plasma-induced (discharges over fused silica pellets) and plasma-catalytic (in the POC reactor) NOx conversion are 39%, 1.5% and 79%, respectively. The in-situ optical emission spectra of the reactive systems imply some short-lived active species formed from plasma-induced and plasma-catalytic processes may be responsible to the observed synergistic effects in this one-stage POC system.     

The Effect of Preliminary Treatment on the Catalytic Activity of Cobalt–Silica Gel Catalysts in the Complete Oxidation of Methane

The effect of temperature in multiple oxidative–reductive treatments on the activity of cobalt–silica gel catalysts in the complete oxidation of methane is studied. A decrease in the temperature of oxidative–reductive treatments from 500°C to 300°C results in an irreversible decrease in the activity of samples prepared by the impregnation of SiO₂with cobalt nitrate. A sample prepared from cobalt acetate and calcined at 500°C shows a lower activity, which was close to the activity of samples prepared from nitrates and calcined at 300°C.     

Oxidation of Oxalic Acid in the Ozone–Chloride–Ion Reaction System in an Aqueous Solution

Russian Journal of Physical Chemistry A - It is shown that the rate of oxidation of oxalic acid H2C2O4 during the ozonation of its solutions grows considerably if sodium chloride is added to the...     

Reaction of Phenylethyne with 2,4-Pentanedione in the Presence of Manganese(Ⅲ) Acetate and Oxygen

WerecentlyrePOrtedmanganese(III)acetate-mediatedoxidatheftee-ndtalCycliZaionofalkeneswith1,3-diones[l-3],o-ketoeSters[4,51andaretoacetamjdesI6]inthepresenceofmolecularoxygenthatyteldedl,2-dioxan-3-olsingoodytelds.Asindlarreachonwasinveedgaedonalkynes,whichgaverisetonovelheterOCyliccomPOundsHereinwedescribetheresu1tS(Schemel)WhenthereachonofDhenVethVne(l)with2,4-pentanedione(2)wncAnedoutinthepresenceacetyl-2-methyl-5-phenylfuran(5)(Tablel,entryl),ThestructUralassigIUnentSarebasedonthe…