The Experts below are selected from a list of 2685 Experts worldwide ranked by ideXlab platform
V Solinas - One of the best experts on this subject based on the ideXlab platform.
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acid base properties of zirconium cerium and Lanthanum Oxides by calorimetric and catalytic investigation
Topics in Catalysis, 2002Co-Authors: Maria Giorgia Cutrufello, Italo Ferino, Roberto Monaci, Elisabetta Rombi, V SolinasAbstract:The combined use of calorimetric and catalytic methods for the investigation of the acid-base properties of oxide systems is discussed with reference to the authors' work on pure and doped zirconia samples, ceria-zirconia and ceria-lanthana solid solutions. Adsorption microcalorimetry of ammonia and carbon dioxide had been used to characterize the samples, whose chemical and thermal history was taken into account. The catalytic behavior of these samples in the conversion of 4-methylpentan-2-ol, route to 4-methylpent-1-ene (starting product for the manufacture of polymers of superior technological properties), had also been studied. On the basis of the calorimetric data, a rationale for interpreting the data for the transformation of 4-methylpentan-2-ol is formulated, which takes into account the role of the concentration and strength of the sites in governing the competition among the various mechanisms for dehydration and dehydrogenation.
Jianghan Shen - One of the best experts on this subject based on the ideXlab platform.
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promotion effect of cerium and Lanthanum Oxides on ni sba 15 catalyst for ammonia decomposition
Catalysis Today, 2008Co-Authors: Hua Wang, Jianghan ShenAbstract:Abstract CeNi/SBA-15 and LaNi/SBA-15 catalysts were prepared by deposition–precipitation (DP) method and characterized by N2 physical adsorption, XRD, H2-TPR, H2-chemisorption and TEM. Their catalytic performances in the ammonia decomposition reaction were tested and compared with Ni/SBA-15 catalyst. Addition of cerium and Lanthanum Oxides to the Ni/SBA-15 catalyst caused some decrease of BET surface area and pore volume of the catalysts, but led to a promotion effect to their catalytic activity which was closely related to the ratio of Ce (La)/Ni. The highest conversion of ammonia could be obtained when the Ce (La)/Ni ratio was around 0.3. The promotion effect is more evident on CeNi/SBA-15(0.3) than on LaNi/SBA-15(0.3) catalyst under identical reaction conditions. The CeNi/SBA-15 and LaNi/SBA-15 catalysts show smaller nickel particle size and easier reducibility in comparison with the Ni/SBA-15 catalysts.
Aiguo Li - One of the best experts on this subject based on the ideXlab platform.
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fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride
ACS Applied Materials & Interfaces, 2012Co-Authors: Chuanyong Jing, Yuying Huang, Aiguo LiAbstract:Coexisting arsenic (As) and fluoride (F) in groundwater poses severe health risks worldwide. Highly efficient simultaneous removal of As and F is therefore of great urgency and high priority. The purpose of this study was to fabricate a novel. composite adsorbent and explore the mechanism for concurrent removal of As(V) and F at the molecular level. This bifunctional adsorbent with titanium and Lanthanum Oxides impregnated on granular activated carbon (TLAC) exhibits a pronounced As(V) and F adsorption capacity over commercially available iron- and aluminum-based adsorbents for synthetic and real contaminated groundwater samples. Synchrotron-based X-ray microfluorescence analysis demonstrates, that and Ti were homogeneously distributed on TLAC. Extended X-ray absorption fine structure spectroscopic results suggest that As(V) formed bidentate binuclear surface complex as evidenced by an averaged Ti-As bond distance of 3.34 angstrom in the presence of F. Adsorption tests and Fourier transform infrared spectroscopy analysis indicate that F was selectively adsorbed on Lanthanum Oxides. The surface configurations constrained with the spectroscopic results were formulated in the charge distribution multisite complexation model to describe the competitive adsorption behaviors of As(V) and F. The results of this study indicate that TLAC could be used as an effective adsorbent for simultaneous removal of As(V) and F.
Marco Daturi - One of the best experts on this subject based on the ideXlab platform.
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Lanthanum Oxides for the selective synthesis of phytosterol esters correlation between catalytic and acid base properties
Journal of Catalysis, 2007Co-Authors: Sabine Valange, A Beauchaud, J Barrault, Z Gabelica, Marco DaturiAbstract:The selective synthesis of phytosterol esters from natural sterols and methyl esters was investigated on new grounds by a chemical process using basic solids that are reusable, active, and more selective than the currently used homogeneous catalysts (e.g., alkali hydrOxides, carbonates). Various Lanthanum Oxides with different synthesis procedures and varying specific surface areas were tested. The catalytic performance of the new solids and, more specifically, the ability of La2O3 Oxides in increasing phytosterol ester selectivity, was correlated with their acido-basic properties, which were fully characterized by infrared spectroscopy. All La2O3 Oxides involved surface carbonate species with different structural states and strengths, as revealed by propyne adsorption. The selectivity to phytosterol ester varied from 90 to 96%, confirming that the side reaction of dehydration of β-sitosterol was strongly inhibited. The phytosterol ester yield could reach 89% and was related to the basic strength of the carbonate species. The lower the carbonate basicity, the higher the phytosterol ester yield. Moreover, IR spectra of catalysts diluted in KBr powder showed that the higher the intensity of unidentate carbonate bands, the higher the yield. It was concluded that the synthesis of phytosterol esters from fatty methyl esters and sitosterols in the presence of La2O3 catalysts requires ionic carbonate species of medium basic strength.
Bert M Weckhuysen - One of the best experts on this subject based on the ideXlab platform.
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selective oxidation of methanol to hydrogen over gold catalysts promoted by alkaline earth metal and Lanthanum Oxides
Chemsuschem, 2009Co-Authors: Bart P C Hereijgers, Bert M WeckhuysenAbstract:A series of alumina-supported gold catalysts was investigated for the CO-free production of hydrogen by partial oxidation of methanol. The addition of alkaline-earth metal oxide promoters resulted in a significant improvement of the catalytic performance. The methanol conversion was ca. 85 % with all studied catalyst materials, however, the selectivity for hydrogen increased from 15 % to 51 % when going from the unpromoted to a BaO-promoted catalyst. The formation of the undesired byproducts CO, methane, and dimethyl ether was considerably reduced as well. The observed trend in catalyst performance follows the trend in increasing basicity of the studied promoter elements, indicating a chemical effect of the promoter material. Superior catalytic performance, in terms of H(2) and CO selectivity, was obtained with a Au/La(2)O(3) catalyst. At 300 degrees C the hydrogen selectivity reached 80 % with only 2 % CO formation, and the catalyst displayed a stable performance over at least 24 h on-stream. Furthermore, the formation of CO was found to be independent of the oxygen concentration in the feed. The commercial Lanthanum oxide used in this study had a low specific surface area, which led to the formation of relative large gold particles. Therefore, the catalytic activity could be enhanced by decreasing the gold particle size through deposition on Lanthanum oxide supported on high-surface-area alumina.
