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21.
Calcined Mg-Al hydrotalcites (Mg/Al=3) can be used as an efficient catalyst in the selective O-methylation of phenol and catechol and N-monomethylation of aniline employing dimethylcarbonate (DMC) as a methylating agent in vapor phase at 275°C. 相似文献
22.
S.J. Kamkar A.M. Wissink V. Sankaran A. Jameson 《Journal of computational physics》2011,230(16):6271-6298
We develop locally normalized feature-detection methods to guide the adaptive mesh refinement (AMR) process for Cartesian grid systems to improve the resolution of vortical features in aerodynamic wakes. The methods include: the Q-criterion [1], the λ2 method [2], the λci method [3], and the λ+ method [4]. Specific attention is given to automate the feature identification process by applying a local normalization based upon the shear-strain rate so that they can be applied to a wide range of flow-fields without the need for user intervention. To validate the methods, we assess tagging efficiency and accuracy using a series of static vortex-dominated flow-fields, and use the methods to drive the AMR process for several theoretical and practical simulations. We demonstrate that the adaptive solutions provide comparable accuracy to solutions obtained on uniformly refined meshes at a fraction of the computational cost. Overall, the normalized feature detection methods are shown to be effective in driving the AMR process in an automated and efficient manner. 相似文献
23.
S. Sugunan K. Sreejarani C.S. Deepa H. Suja 《Reaction Kinetics and Catalysis Letters》2000,71(2):307-311
A comparitive study of the acid-base properties and physico-chemical characteristics of pure SnO2, sulfated SnO2 and sulfated binary oxides of Sn and Pr was done. The data were correlated with the catalytic activity of the oxides towards benzoylation of toluene. 相似文献
24.
Al-pillared, Fe-pillared and mixed Fe-Al pillared systems have been prepared and characterized using EDX and XRD analyses,
surface area pore volume and acidity measurements. Mixed systems are found to be superior to single oxide pillared systems
in terms of acidity and aniline methylation activity.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
25.
26.
J.D. Eshelby (1957, 1959) has calculated the deformation field associated with an ellipsoidal inclusion in a state of homogeneous strain within an infinite matrix. Since most real precipitates occur with facets, the strain within such an inclusion is not uniform. Thus, plate precipitates of θ′ in Al-Cu and η in Al-Au have coherent broad faces with mismatches of 1.34 and 4.95 % respect- ively and semicoherent or disordered interfaces at the edges with residual mismatches of about ?4.3 and ?1.00% normal to the broad faces. The deformation field in the matrix around such precipitates has been calculated using Kelvin's (1848) result for the stress field due to a point force. The calculations show the existence of high stresses near the edges of the precipitates where they have an appreciable misfit. Unlike the case of an ellipsoidal inclusion, the stress fields of these precipitates have dilatational components which can affect the diffusion of solute atoms to them and, thus, the kinetics of interface migration. The behavior of alloys containing these precipitates indicates that the moduli of the precipitates are somewhat greater than those of the matrices. The present calculations, based on the assumption that the two moduli are the same, underestimate the actual deformation field in the matrix. In real systems, therefore, the effects of the deformation field on misfit dislocation nucleation and kinetics of interface migration are likely to be somewhat greater in general. 相似文献
27.
Richmonds C Witzke M Bartling B Lee SW Wainright J Liu CC Sankaran RM 《Journal of the American Chemical Society》2011,133(44):17582-17585
Electrochemical reactions are normally initiated in solution by metal electrodes such as Pt, which are expensive and limited in supply. In this Communication, we demonstrate that an atmospheric-pressure microplasma can act as a gaseous, metal-free electrode to mediate electron-transfer reactions in aqueous solutions. Ferricyanide is reduced to ferrocyanide by plasma electrons, and the reduction rate is found to depend on discharge current. The ability to initiate and control electrochemical reactions at the plasma-liquid interface opens a new direction for electrochemistry based on interactions between gas-phase electrons and ionic solutions. 相似文献
28.
29.
Summary Molybdena modified pure as well as sulfated ceria systems have been studied with a view to investigate their structure, surface
acidic properties and catalytic behavior for cyclohexanol decomposition reaction. The characteristics of the modified systems
were obtained from XRD measurements and acid structural properties from Temperature Programmed Desorption (TPD) of ammonia. 相似文献
30.
Spinel systems with the composition of Cu1−xZnxCr2O4 [x = 0 CCr, x = 0.25 CZCr-1, x = 0.5 CZCr-2, x = 0.75 CZCr-3 and x = 1 ZCr] were prepared by homogeneous co-precipitation
method and were characterized by X-ray diffraction (XRD) and FT-IR spectroscopy. Elemental analysis was done by EDX, and surface
area measurements by the BET method. The redox behavior of these catalysts in cyclohexane oxidation at 243 K using TBHP as
oxidant was examined. Cyclohexanone was the major product over all catalysts with some cyclohexanol. 69.2% selectivity to
cyclohexanol and cyclohexanone at 23% conversion of cyclohexane was realized over zinc chromite spinels in 10 h. 相似文献