Catalytic carbon monoxide oxidation over CuO/CeO2 composite catalysts

Summary CeO₂ nanoparticles were prepared by thermal decomposition of cerous nitrate and then used as supports for CuO/CeO₂ catalysts prepared via the impregnation method. The samples were characterized by XRD, HRTEM, H₂-TPR and XPS. The catalytic properties of the catalysts for low-temperature CO oxidation were studied by using a microreactor-GC system.     

Study on the carburizing character of iron catalysts by Temperature Programmed Surface reaction of carburization?

Summary The promotion effect of potassium has been studied with the method of Temperature Programmed Surface Carburization (TPSC) technique and H₂-TPR. The process of carburization on the catalyst surface was enhanced by addition of potassium was added, so that the probability for the generated alkenes species to be further hydrogenated was increased. As a result, the percentage of the alkenes from C2 to C4 in the products was increased.     

Preparation and activity measurement of some low pressure methanol synthesis catalysts

Summary In the present study, twenty four catalysts for low pressure methanol synthesis were prepared according to a pre-designed research program consisting of three stages. In each stage, applying the experimental design techniques, a number of catalysts were synthesized by the co-precipitation method, using different proportions of metal salts solutions. The activities of the catalysts were determined applying a laboratory scale continuous packed bed reactor. It was noted that the calcinations temperature, ageing time and molar ratio of metal nitrates to precipitant, had the highest effects on the activity of the catalysts.     

Catalytic oxidation of phenol in aqueous media over CuZSM-12 zeolite?

Summary The catalytic oxidation of phenol over CuZSM-12 (SAR = 200) has been studied using a semi-batch slurry reactor at temperatures of 110; 120 and 130^oC, and acidic neutral and basic pH. At 130^oC, the phenol undergoes total conversion to carbon dioxide and water in 1.5 h. The kinetic parameters were evaluated using a modified homogeneous-heterogeneous model for the experimental data. Using this modified model, the activation energy for the catalytic oxidation process was ca. 90 kJ mol^-1.     

Characterization of CuO/Al2O3 catalysts used in the oxidation of phenol solutions

Two CuO/Al₂O₃ catalysts were synthesized at different calcination temperatures and used for the oxidation of phenol solutions. Deactivation is due to leaching of the active phase and deposition of carbonaceous material.This revised version was published online in December 2005 with corrections to the Cover Date.     

WO3/TiO2 catalysts: Morphological and structural properties

Titania-supported tungsten oxide catalysts with different W loadings up to 9 wt. % and calcined at different temperatures have been prepared and characterized. It is found that W hinders the initial sintering of anatase, providing thermal stability. The interaction of W with TiO₂ and the amount of hydroxy groups present on the surface can limit diffusion, thus reducing the sintering rate.     

Kinetics of gas oil catalytic cracking

Summary In the present work catalytic cracking of gas oils has been studied in a standard MAT reactor. The cracking product distribution was measured at four different temperatures. Based on the experimental results, a 4-lump kinetic model was applied. Kinetic constants were estimated using the sequential step optimization method. Simulation results have shown to be in a good agreement with experimental data. An isothermal pseudo steady-state model for fixed bed MAT reactor is proposed.     

High-temperature XRD studies of the phase transformations in a MnOx/Al2O3 catalyst for deep oxidation of hydrocarbons

Omsk Branch of Boreskov Institute of Catalysis     

Selective catalytic oxidation of NO with O2 over Ce-doped MnOx/TiO2 catalysts

A series of Ce-doped MnOx/TiO2 catalysts were prepared by impregnation method and used for catalytic oxidation of NO in the presence of excess O2. The sample with the Ce doping concentration of Ce/Mn=1/3 and calcined at 300°C shows a superior activity for NO oxidation to NO2. On Ce(1)Mn(3)Ti catalyst, 58% NO conversion was obtained at 200°C and 85% NO conversion at 250°C with a GHSV of 41000 h-1, which was much higher than that over MnOx/TiO2 catalyst (48% at 250°C). Characterization results implied that the higher activity of Ce(1)Mn(3)Ti could be attributed to the enrichment of well-dispersed MnOx on the surface and the abundance of Mn3+ and Ti3+ species. The addition of Ce into MnOx/TiO2 could improve oxygen storage capacity and facilitate oxygen mobility of the catalyst as shown by PL and ESR, so that its activity for NO oxidation could be enhanced. The effect of H2O and SO2 on the catalyst activity was also investigated.     

Investigation of the HDS kinetics of dibenzotiophene and its derivatives in real gas oil ??

Summary The hydrodesulfurization (HDS) of dibenzothiophene (DBT), 4-methyl-dibenzothiophene (4 M-DBT), 4,6-dimethyldibenzothiophene (4,6 DM-DBT) and 4,6-diethyldibenzothiophene (4,6 DE-DBT) as real gas oil components on NiMo/Al₂O₃ catalyst was investigated. On the basis of the first order rate constants of HDS of the individual sulfur compounds calculated by both integral and differential evaluations the reactivities of the investigated compounds decreased in the order DBT >> 4 M-DBT > 4,6 DE-DBT ? 4,6 DM-DBT. Additionally, results showed that product inhibition during HDS does not take place.     

A facile synthetic route for the preparation of the Au/Mox/Al2O3 catalysts towards CO oxidation

Summary A new facile single-step synthetic route is reported for the preparation of Au/MO_x/Al₂O₃ catalysts. The preparation method has the merit of facility but leads to not only the simultaneous load of both gold source and MO_x precursor on Al₂O₃ support, but also the formation of Au/MO_x/Al₂O₃ with high gold loading ratio, high dispersion and high activity for CO oxidation.     

A molecular route towards silica supported zirconium catalysts active for the mild oxidation of olefins with H2O2

A series of Zr based catalysts were synthesized using tetraneopentylzirconium as precursor complex and a silica partially dehydroxylated. Modifications of the Zr coordination sphere of the anchored complex, (SiO)ZrNp₃ (Np = neopentyl), by hydrolysis or hydrogenolysis lead to catalysts showing unexpected activity for the expoxidation of cyclohexene and hydroxylation of phenol with H₂O₂.     

Comparative laboratory steam-cracking of different raw materials

Summary Steam cracking of several gasoline and gas oil samples was carried out under different conditions and the results are reported. Some of sample feedstocks were previously cracked in a commercial plant so the laboratory and commercial results could be compared. It was found that the laboratory reactor was more sensitive to the changes of the composition of the raw materials.     

Enhancement of distillate selectivity in Fischer-Tropsch synthesis by using iron and cobalt catalysts in a novel dual-bed reactor ?

Summary An integrated process for producing liquid fuels from synthesis gas via a two-stage Fischer-Tropsch (FT) reaction is disclosed. An iron catalyst was used in the first bed of a fixed-bed reactor followed by a ruthenium promoted cobalt catalyst in the second bed. The activity and selectivity of the dual-bed system were assessed and compared with those using catalysts in a single bed system, separately. The methane selectivity in the dual-bed reactor was about 11% less compared to that of the single-bed system. The C₅⁺ selectivity for the dual-bed reactor was 19.7% higher than that of the single-bed system.     

Studies of adsorption-desorption processes in SO2 oxidation on the active component of vanadium catalysts

Diffusion and solubility coefficients of O₂, SO₂ and SO₃ in the active component of vanadium catalysts have been determined by a high-speed relaxation method. Processes of their dissolution are shown to be quasi-equilibrium with respect to catalytic reactions.

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O₂, SO₂ SO₃ ,

     

Investigation of H2S oxidation by oxygen on oxide catalysts in sulfur condensation conditions

H₂S oxidation with oxygen has been studied on three industrial oxide catalysts (Fe−Cr−Zn, Cu−Cr−Al, V−Ti−Al). Thermodynamically possible changes in the composition of the catalysts have been evaluated. Regularities determining deep or partial oxidation of H₂S have been found. Deep oxidation is connected to the presence of active oxygen on the catalyst surface; its removal results in a decrease of activity and increase of the sulfur selectivity. Oscillations caused by periodic adsorption-desorption of sulfur on the catalyst surface have been observed on the most active V−Ti−Al catalysts in oxygen excess.     

Molecular structure and reactivity of titania-supported transition metal oxide catalysts synthesized by equilibrium deposition filtration for the oxidative dehydrogenation of ethane

The molecular structure and catalytic performance of (MoO_x)_n/TiO₂, (WO_x)_n/TiO₂ and (VO_x)_n/TiO₂ catalysts (synthesized by the equilibrium–deposition–filtration/EDF method) for oxidative dehydrogenation (ODH) of ethane were studied by in situ Raman spectroscopy at 430 °C and catalytic measurements in the temperature range of 420–480 °C. The extent of association within the deposited oxometallic phase followed the sequence (VO_x)_n/TiO₂ >> (MoO_x)_n/TiO₂ > (WO_x)_n/TiO₂; a concurrent trend in reduction susceptibility was evidenced by exploiting the relative normalized Raman band intensities while monitoring the response of the vibrational properties of the catalytic samples under reactive (C₂H₆/O₂/He) and reducing (C₂H₆/He) conditions by in situ Raman spectroscopy. The catalyst reactivity tracks the corresponding trend in reduction susceptibility as evidenced by the in situ Raman spectra. Selective reaction pathways are favored at high coverage whilst combustion routes are activated at low coverages due to the involvement of carrier lattice oxygen sites. The observed apparent reaction rates and activation energies are discussed in relation to various structural and reactivity aspects.     

Highly active Mo-V-Te-Nb-O catalysts obtained by eliminating surface Te0 for selective oxidation of propane to acrylic acid

Different methods were used to eliminate the negative effect of surface Te⁰ in Mo-V-Te-Nb-O catalysts. The characterization and catalytic results showed that the best catalytic performance was obtained on the catalyst prepared by addition of HNO₃, and the excellent catalytic behavior could be attributed to the elimination of surface Te⁰ and the optimum synergetic effect between the M1 and M2 phases.     

Surface and catalytic properties of Cu/Zn mixed oxide catalysts

Copper catalysts supported on zinc oxide, with different loading (1–20 wt.% CuO), were prepared by impregnation of the basic zinc carbonate with a water solution of copper nitrate. The impregnated samples were dried at 120°C and calcined at 400–700°C. The surface and catalytic properties of CuO loaded on ZnO were determined by N₂ adsorption measurements conducted at −196°C and CO oxidation by O₂ at 150–300°C, respectively. The results obtained revealed that the surface and catalytic properties of different solids were dependent upon CuO content and calcination temperature. The specific surface areas of various adsorbents decreased monotonically as a function of both calcination temperature and extent of loading. However, the activation energy of sintering, ΔE_S, was found to increase by increasing the amount of CuO present. On the other hand, the CO oxidation activity on various catalysts was found to increase progressively by increasing the calcination temperature from 400 to 500°C, then decreased by increasing the temperature from 500 to 700°C. The augmentation of CuO content from 1 to 5 wt.% resulted in an increase in the CO oxidation activity, which decreased by increasing the extent of loading above this limit.     

Performance of pyrophyllite and halloysite clays in the catalytic degradation of polystyrene

Summary The performance of pyrophyllite and halloysite clays in the degradation of polystyrene (PS) was investigated. The degradation was carried out in a semi-batch reactor with a mixture of polystyrene and catalysts at 400-450^oC. The catalysts showed good catalytic activity for the degradation of PS with high selectivity to aromatics liquids. Styrene is the major product, and ethylbenzene is the second most abundant one in the liquid product. The catalytic degradation showed much less production of styrene dimers and higher selectivity to ethylbenzene than the thermal degradation did. High degradation temperature favored the production of styrene monomer, but it decreased the ethylbenzene production.