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A set of Y-type zeolites with Si/Al atomic ratios between 7–45 were studied as catalysts in the aminocyclization reaction between acrolein and ammonia to produce pyridine and 3-picoline. The catalytic activity tests at 360 °C revealed that the acrolein conversion increased in the order Z45 < ZY34 < ZY7 < ZY17, in agreement with the increase of the total acidity per gram of catalyst. In all cases, pyridine bases and cracking products (acetaldehyde and formaldehyde) were detected in the outflow from the reactor. The total yield of pyridines was inversely proportional to the total acidity for the catalysts, which presented large surface areas and micro- and mesoporosity. The selectivity towards 3-picoline was favored when using catalysts with a Brønsted/Lewis acid sites ratio close to 1. The formation of pyridine occurred more selectively over Lewis acid sites than Brønsted acid sites. The deactivation tests showed that the time on stream of the catalysts depended on the textural properties of zeolites, i.e., large pore volume and large BET area, as evidenced by the deactivation rate constants and the characterization of the spent catalysts. The physicochemical properties of the catalysts were determined by XRD, UV-vis, and Raman spectroscopies, infrared spectroscopy with adsorbed pyridine, N2 physisorption, and SEM-EDXS. After the reaction, the spent catalysts were characterized by XRD, Raman spectroscopy, TGA, and SEM-EDXS, indicating that the uniform deposition of polyaromatic species on the catalyst surface and within the porous system resulted in the loss of activity. [ABSTRACT FROM AUTHOR]

In this paper, it is reported the fabrication of a new dense ceramic‐molten carbonate membrane used for the selective separation of carbon dioxide (CO2) and oxygen (O2) at elevated temperatures (850‐950°C). First, it was chemically synthesized a fluorite/perovskite ceramic oxide with mixed ionic‐electronic conduction properties and general formula Ce0.9Pr0.1O2‐δ/Pr0.6Sr0.4Fe0.5Co0.5O3‐δ (CP‐PSFC, 60:40 wt%) by the citrate‐ethylene‐diamine‐tetra acetic acid (EDTA) route. Then, a disk‐shaped porous ceramic support partially sintered was infiltrated with a ternary mixture of molten salts of Li2CO3/Na2CO3/K2CO3 composition. The permeation measurements at high temperatures suggest a concurrent separation of both species CO2 and O2. The system exhibits high permeance of CO2 and O2 by rising to maximum values of 2.17 × 10−7 and 0.69 × 10−7 mol m−2 s−1 Pa−1, respectively at 950°C. Moreover, the possibility of modulating the permeate CO2:O2 ratio is envisaged by changing the fluorite to perovskite proportion in the membrane composition. The stability performance of the obtained membrane was studied under a long‐term permeation test. It exhibits a remarkable thermal and chemical stability during 110 h at 875°C. This way, it corroborated the proposed new ceramic phase's excellent properties for the fabrication of supported ceramic‐molten carbonate membranes. [ABSTRACT FROM AUTHOR]

Glycerol dehydration to acrolein was studied with three catalysts using zeolite-Y. This zeolite in its protonic form (HY), with La (LaY) and Pd with La (Pd/LaY), was characterized by X-ray diffraction (XRD), Fourier-transform-infrared spectroscopy (FTIR) with pyridine, BET, Scanning Electron Microscope (SEM)-Energy-Dispersive Spectroscopy X-ray (EDS) and the catalytic activity tests were carried out under H2 atmosphere. It was found that La ions exchanged in the zeolite-Y resulted in the improvement of both glycerol conversion and yield to acrolein, also a relatively constant glycerol conversion was achieved up to three hours, due to the presence of Pd on the catalyst and H2 in the feed. The comparison of the calculated and experimental yields obtained from the catalytic tests of the Pd/LaY catalyst indicates a greater activity for the reaction to acrolein than for the reaction to acetol. The calculated equilibrium yields of the dehydration reaction from glycerol to acrolein, acetol, ethanal, methanol, and water and the experimental yields of a Pd/LaY catalyst were compared. Thermodynamically, a complete conversion of glycerol can be achieved since the general system remains exothermic and promotes the path to acetol below 480 K. Above this temperature the system consumes energy and favors the production of acrolein, reaching its maximum concentration at 600 K. [ABSTRACT FROM AUTHOR]

This study shows the development of a combustion promoter for the oil-refining process called fluid catalytic cracking (FCC). The investigation of a catalyst prepared for the combustion of CO composed of 0.05 wt% Pt supported on SiO2–Al2O3–0.5 wt% W microspheres with high mechanical resistance, promoted with tungsten oxides (WOx) that can inhibit the sintering of Pt, is reported. The addition of WOx in SiO2–Al2O3 inhibited the decrease in the specific area when calcined from 550 °C to 950 °C. SiO2–Al2O3 support in the form of calcined microspheres with average diameters between 70–105 µm were produced by spray drying, using two atomization discs with vanes of different geometry: a straight rectangular blade disc (DAR) and a curved rectangular vanes disc (DAC). The DAR disk produced whole microspheres, while the DAC had hollow and broken microspheres. The microspheres were characterized by XRD, SEM, optical microscopy, N2 physisorption (BET area) and fracture resistance tests. The Pt catalysts were evaluated by TPR, H2 chemisorption and CO combustion. The catalyst of 0.05 wt% Pt/SiO2–Al2O3–0.5 wt% turned out to be the most stable. A thermal stabilization effect was observed at contents lower than 1 wt% W that allowed it to inhibit the sintering of the Pt catalyst. [ABSTRACT FROM AUTHOR]

The addition of Pt (0.1 wt%Pt) to the 2 wt%Ag/Al2O3-WOx catalyst improved the C3H8– Selective Catalytic Reduction (SCR) of NO assisted by H2 and widened the range of the operation window. During H2–C3H8–SCR of NO, the bimetallic Pt–Ag catalyst showed two maxima in conversion: 80% (at 130 °C) and 91% (between 260 and 350 °C). This PtAg bimetallic catalyst showed that it could combine the catalytic properties of Pt at low temperature, with the properties of Ag/Al2O3 at high temperature. These PtAg catalysts were composed of Ag+, Agnδ+ clusters, and PtAg nanoparticles. The catalysts were characterized by Temperature Programmed Reduction (TPR), Ultraviolet Visible Spectroscopy (UV-Vis), Scanning Electron Microscopy (SEM)/ Energy Dispersed X-ray Spectroscopy (EDS), x-ray Diffraction (XRD) and N2 physisorption. The PtAg bimetallic catalysts were able to chemisorb H2. The dispersion of Pt in the bimetallic catalysts was the largest for the catalyst with the lowest Pt/Ag atomic ratio. Through SEM, mainly spherical clusters smaller than 10 nm were observed in the PtAg catalyst. There were about 32% of particles with size equal or below 10 nm. The PtAg bimetallic catalysts produced NO2 in the intermediate temperature range as well as some N2O. The yield to N2O was proportional to the Pt/Ag atomic ratio and reached 8.5% N2O. WOx stabilizes Al2O3 at temperatures ≥650 °C, and also stabilizes Pt when it is reduced in H2 at high temperature (800 °C). [ABSTRACT FROM AUTHOR]

Abstract: An earlier structural model for binary silicate melts and glasses is extended to MF–BeF2 (M=Li, K) systems. The evaluation of the thermodynamic properties as well as the phase diagrams for the binary LiF–BeF2 system and the integral enthalpy of mixing of the KF–BeF2 system are carried out with this model. This thermodynamic model is based on the assumption that each alkali fluoride produces the depolymerization of BeF2 network with a characteristic free energy change. A least squares optimization program permits all available thermodynamic and phase diagram data to be optimized simultaneously. In this manner, data for these binary systems have been analysed and represented with a small number of parameters. The model predicts the chain-length distribution of polymeric ions, even though these are not explicitly treated as structural units of the model. The calculated fluoride polyanion chain-length distribution for the LiF–BeF2 system is in quantitative agreement with the predictions reported in the literature. [Copyright &y& Elsevier]

Abstract: A thermodynamic study on the TiO2–Bi2O3 system was carried out using differential thermal analysis (DTA) and X-Ray diffraction (XRD) techniques covering the composition range from 65 to 90mol% Bi2O3. From the XRD results the only two intermediate compounds in the Bi2O3 rich region were Bi4Ti3O12 and Bi12TiO20. The Bi4Ti3O12 phase presents the well known plate-like morphology. The experimentally determined phase transition temperatures with DTA technique were compared with thermodynamic calculated results and good agreement was obtained. The DTA results also showed that the limit of the peritectic reaction between liquid and Bi4Ti3O12 occurs approximately at 90mol% Bi2O3. The phase diagram of the TiO2–Bi2O3 system was calculated using a quasichemical model for the liquid phase. The thermodynamic properties of the intermediate compounds were estimated from the data of TiO2 and Bi2O3 pure solids. In this manner, data for this binary system have been analysed and represented with a small adjustable parameter for the liquid phase. [Copyright &y& Elsevier]

Abstract: An earlier structural model for binary silicate melts and glasses is extended to zinc chloride–alkali metal chloride systems. The evaluation of the available thermodynamic and phase diagrams data for the MCl–ZnCl2 (M=Li, Na, K) binary systems have been carried out using the structural model for the liquid phase. This thermodynamic model is based on the assumption that each alkali chloride produces the depolymerization of ZnCl2 network with a characteristic free-energy change. A least-squares optimization program permits all available thermodynamic and phase diagram data to be optimized simultaneously. In this manner, data for these binary systems have been analysed and represented with a small number of parameters. [ABSTRACT FROM AUTHOR]