Catalytic combustion of ethyl acetate on supported copper oxide catalysts

Total oxidation of ethyl acetate on supported copper oxide catalysts was investigated. The catalysts have been prepared by wet impregnation method and characterized by XRD, TEM and XPS. Among the catalysts with the supports of TiO2, CeO2/TiO2 and CeO2-ZrO2/TiO2, CeO2-ZrO2 solid solutions doped TiO2 supported catalyst gives the highest catalytic activity. Catalyst with the composition of 5 wt.% CuO/10 wt.% CeO2-ZrO2-TiO2 shows the total oxidation of ethyl acetate at about 270 degrees C with the 100% CO2 selectivity. The characterization studies of supported copper oxide catalysts showed that the highly dispersed CuO is one of the active phase which contacts intimately with the support, the action of the interface between the components was not be ignored.     

Sorption of carbon dioxide in cation exchanged Y type zeolites: Sorption isotherms and state of sorbed molecule

The sorption of carbon dioxide in a series of Y type zeolites exchanged with La³⁺, Ca²⁺, NH₄⁺ and mixtures of these cations, is studied in the range 273–423 K. The results are discussed in terms of cation specificity and contribution of quadrupole moment to the sorption energetics. Equilibrium sorption capacity followed the sequence Na-Y > La(32)-Y > … > La(92)-Y for La³⁺ exchanged zeolites and Na-Y > Ca(85)-Y > … H(85)-Y > La(60)H(25)-Y > La(60) Ca(25)-Y for other zeolites. At comparatively lower pressures and higher temperatures Ca(85)-Y was found to have highest sorption capacity, indicating predominently the effect of cationic charge over that of cation density on the CO₂ sorption at low coverage. The decrease in sorption capacity CO₂ was 70% as compared to only 10% in case of nitrogen sorption from NaY to La(92)-Y.The sorption data yielded linear Dubinin plots, however, the saturation capacities obtained from these plots, were found to be higher as compared to those obtained experimentally. Both the Koble—Corrigan and Sips equation gave linear plots up to a pressure of 300 Torr. The number of active centres for CO₂ sorption, estimated from Koble-Corrigan exponent ‘n’ decreased with the increase in temperature and the degree of exchange.The sorption data fitted the statistical isotherm models derived from Langmuir and Volmer equation for ideal systems. The linear plots of ln K_L and In K_v against coverage were obtained in case of NaY and H(85)-Y indicating the applicability of both the localized and mobile sorption without interaction. In case of Ca(85)-Y and La³⁺ exchanged zeolites both the ln K_L and In K_v did not yield linear plots against coverage indicating neither localized nor mobile model with or without molecule—molecule interaction, could represent the sorption data.     

催化剂对乙醇催化燃烧法制备碳纳米纤维的影响

分别以硝酸铁、硝酸钴、硝酸镍以及氯化铁、氯化钴、氯化镍作为催化剂先体，利用乙醇催化燃烧法制备了碳纳米纤维。利用扫描电子显微术、透射电子显微术和X射线能量分散谱术对样品进行了表征。讨论了不同种类的催化剂先体对产物形貌和生长机制的影响。     

Kinetic models of combustion of kerosene and its components

Modern investigations on creation of kinetic models of combustion of hydrocarbons entering into the composition of kerosene and kerosene as a whole have been analyzed. Certain recommendations on application of these models to calculation of actual gasdynamic flows have been given. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 6, pp. 14–25, November–December, 2005.     

Catalytic combustion of chlorobenzene over Mn-Ce-La-O mixed oxide catalysts

A series of Mn(x)-CeLa mixed oxide catalysts with different compositions prepared by sol-gel method were tested for the catalytic combustion of chlorobenzene (CB), as a model of chlorinated aromatics. Mn(x)-CeLa catalysts with the ratios of Mn/(Mn + Ce + La) in the range from 0.69 to 0.8 were found to possess high catalytic activity in the catalytic combustion of CB. The stability and deactivation of Mn(x)-CeLa catalysts were studied by other assistant experiments. Mn(x)-CeLa catalysts can deactivate below 330 °C, due to the strong adsorption of Cl species produced during the decomposition of CB. Nevertheless, the increase in oxygen concentration can enhance the resistance to Cl poisoning through the reaction of surface oxygen species with residual chlorine. At 350 °C, high activity, good selectivity and desired stability were observed over Mn(x)-CeLa catalysts.     

The use of natural Kazakhstan zeolites for the development of gas purification catalysts

The results of investigation of catalysts based on natural zeolite in comparison with synthetic ZSM-5 zeolite used in reduction of nitrogen oxides and conversion of carbon monoxide are presented. It was found that rearrangement of the crystal structure of natural zeolite begins upon heating it above 500 °C in air. The structure of natural zeolite has been improved by introduction of various modifiers and selection of thermal regime of samples training. It has been shown that developed compositions of press-mass for preparation of carriers for gas purification catalysts in the form of granules and tablets satisfy the requirements on ductility and mechanical strength. The efficiency of synthesized granular and block Cu–Ce, Cu–Ni–Cr, Ti–V, Ti–VW, and TiO₂–V₂O₅ catalysts based on natural and synthetic zeolites was determined in conversion of CO and nitrogen oxides. The results of X-ray structure analysis of clinoptilolite of the Republic of Kazakhstan deposits—Chankanai and Taizhuzgen—are represented in comparison with synthetic ZSM-5 zeolite. The paper also comprises data about their thermal stability, ductility, and strength of compositions on their base. Metals particles morphology and dispersity are studied by the method of electronic microscopy. These particles were used as active components of synthesized catalysts.     

Synthesis and characterization of supported polysugar-stabilized palladium nanoparticle catalysts for enhanced hydrodechlorination of trichloroethylene

Palladium (Pd) nanoparticle catalysts were successfully synthesized within an aqueous phase using sodium carboxymethyl cellulose (CMC) as a capping ligand which offers a green alternative to conventional nanoparticle synthesis techniques. The CMC-stabilized Pd nanoparticles were subsequently dispersed within support materials using the incipient wetness impregnation technique for utilization in heterogeneous catalyst systems. The unsupported and supported (both calcined and uncalcined) Pd nanoparticle catalysts were characterized using transmission electron microscopy, energy dispersive x-ray spectrometry, x-ray diffraction, and Brunauer-Emmett-Teller surface area measurement and their catalytic activity toward the hydrodechlorination of trichloroethylene (TCE) in aqueous media was examined using homogeneous and heterogeneous catalyst systems, respectively. The unsupported Pd nanoparticles showed considerable activity toward the degradation of TCE, as demonstrated by the reaction kinetics. Although the supported Pd nanoparticle catalysts had a lower catalytic activity than the unsupported particles that were homogeneously dispersed in the aqueous solutions, the supported catalysts retained sufficient activity toward the degradation of TCE. In addition, the use of the hydrophilic Al(2)O(3) support material induced a mass transfer resistance to TCE that affected the initial hydrodechlorination rate. This paper demonstrates that supported Pd catalysts can be applied to the heterogeneous catalytic hydrodechlorination of TCE.     

Derivative dilatometric study of natural zeolites

This study concerns the expansion-shrinkage behavior of the following zeolites: natrolite, thomsonite, scolecite, heulandite, clinoptilolite, and stilbite. The analytical method used was derivative dilatometry. The use of dilatometric measurement provides a clearer representation of metaphase formation during the thermal dehydration of a zeolite. The dehydration of the minerals in the natrolite group can be described as expansive, whereas the dehydration of heulandite, clinoptilolite, and stilbite is characterized by contracting reactions. This contrasting behavior seems to be consistent with the varying qualities of the water bonding in the zeolite lattice.     

Experimental study of Cu(+)-Na(+) exchanged glass waveguides

Optical waveguides have been obtained by field-assisted Cu(+)-Na(+) exchanged on glass. The refractive index profiles of the waveguides are determined by means of the prism-coupling technique and Chiang's method [J. Lightwave Technol. LT-3, 385 (1985)], and they correlate with the index profile calculated as a function of the glass composition. The composition profile is examined with the aid of a scanning electron microscopy with energy-dispersive x-ray analysis, and the diffusion process is explained by the one-dimensional diffusion equation.     

Simultaneous soot combustion and nitrogen oxides storage on potassium-promoted hydrotalcite-based CoMgAlO catalysts

A series of potassium-promoted hydrotalcite-based CoMgAlO mixed oxide catalysts used for simultaneous soot combustion and nitrogen oxides storage were prepared by impregnation method. The techniques of TG/DTA, XRD, H2-TPR and in situ DRIFTS were employed for catalyst characterization. Over the catalyst containing 7.5% or 10% K, the soot ignition temperature (Ti=260 degrees C) and total removal temperature (Tf=390 degrees C) are decreased by 180 degrees C and 273 degrees C, respectively, as compared with the uncatalyzed reaction. The results of kinetic calculation show that the presence of K-promoted catalysts decreases the activation energy of soot combustion from 207kJ/mol to about 160kJ/mol. When 400ppm NO is introduced, lower characteristic temperatures or higher reaction rate for soot oxidation is achieved. Simultaneously, relatively larger nitrogen oxides storage capacity is obtained. It is revealed by H2-TPR that the addition of K increases the amount of active Co sites and the mobility of bulk lattice oxygen due to the low melting point of K-containing compounds, the low valence of K+ and the strong interaction between K and Mg(Al). For nitrogen oxides storage, different routes via chelating bidentate nitrates, monodentate nitrates and ionic nitrates are confirmed by in situ DRIFTS over the CoMgAlO catalysts with potassium loadings of 0, 1.5 and 7.5%, respectively.     

Amorphous silica alumina debris in zeolites and zeolitic-type clusters in amorphous silica-alumina catalysts

The dealumination of amorphous silica-alumina catalysts suggests that the acid active phase is formed of AlO₄ and SiO₄ chains or rings. Such species might be compared to amorphous silica-alumina debris in steamed zeolites.     

An XPS study of cation-exchanged Y-type zeolites

A study of Na-, Li-, and Cs-exchanged Y-type zeolites using conventional MgKα and high-energy monochromatic AgLα radiation is described. The use of an electron flood gun for charge neutralization in the potential range 0–10 V has revealed both physical and chemical instability of certain samples. Certain ions (e.g., sodium in the Na-exchanged samples) are mobilized by higher-energy (above 6 V) electron bombardment and migrate to the surface region, where they can be reduced to the metal state.     

VOCs催化燃烧整体式催化剂的研究进展

催化燃烧是实现挥发性有机物(VOCs)高效燃烧的一种处理技术,对整体式催化剂的组成以及载体的分类和特点进行了阐述,比较了整体式催化剂和粒状催化剂的特点,重点论述了整体式催化剂的种类,包括贵金属、钙钛矿型和六铝酸盐等几种主要类型整体式催化剂,以及近年来VOCs催化燃烧整体式催化剂的国内外研究近况,并指出了整体式催化剂今后的研究方向。