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71.
72.
Vilas H Rane Sopan T Chaudhari Vasant R Choudhary 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2006,81(2):208-215
Rare earth (viz. La, Ce, Sm, Nd and Yb) promoted CaO catalysts have been investigated, comparing their surface properties (viz. surface area and basicity/base strength distribution) and catalytic activity/selectivity in the oxidative coupling of methane at different reaction conditions (temperatures, 650–800 °C, CH4/O2 ratios, 2.0–8.0 and space velocity, 51 360 cm3 g?1 h?1). The surface properties and catalytic activity/selectivity are strongly influenced by the rare earth promoter and its concentration. Apart from the Sm‐promoted CaO catalyst, both the total and strong basic sites (measured in terms of CO2 chemisorbed at 50° and 500 °C respectively) are decreased due to the promotion of CaO by rare earth metals (viz. La, Ce, Nd and Yb). The catalytic activity/selectivity is strongly influenced by the temperature, particularly below ?700 °C, whereas at higher temperature no further effect is seen. The La2O3? CaO, Nd2O3? CaO and Yb2O3? CaO catalysts showed high activity and selectivity, and also their results are comparable. Among the catalysts, Nd‐promoted CaO (with Nd/Ca = 0.05) showed the best performance (19.5% CH4 conversion with 70.8% C2+ selectivity) in the oxidative coupling of methane. A close relationship between the surface density of total and strong basic sites (measured in terms of CO2 chemisorbed at 50° and 500 °C respectively) and the C2+ selectivity and/or C2+ yield has been observed. Copyright © 2005 Society of Chemical Industry 相似文献
73.
An analytical technique is presented to compute the weight distribution of a linear block code by performing a Fourier analysis involving certain matrices obtained from the code trellis. The proposed method is general, easy to implement, and can be used without having to traverse the trellis or carry out tedious analytical work. The introduced technique can be used as a flexible analytical tool to capture the weight structure of the code with application to problems involving analysis and/or design 相似文献
74.
The kinetics of hydroformylation of 1-decene using homogenous HRh(CO)(PPh3)3 catalyst has been reported in the temperature range of 50–70 °C. The effect of catalyst,P
H
2,P
CO, and 1-decene concentration on the rate of hydroformylation has been studied. Based on the analysis of initial rate data, a rate equation has been proposed and kinetic parameters evaluated. The activation energy was found to be 11.76 kcal/mol. A molecular level approach to kinetic modelling has also been illustrated. The rate equation derived assuming oxidative addition of H2 as a rate determining step, has been found to represent the data satisfactorily. The rate parameters for the mechanistic model have been evaluated for the data at 60 °C.NCL Communication No. 5735. 相似文献
75.
R Viswanathan S N Yedave S T Bendre S M Kanetkar S M Chaudhari S B Ogale 《Bulletin of Materials Science》1991,14(2):435-441
Ion beam and thermally-induced interface reactions between highT
c superconducting thin film of Y1Ba2Cu3O7−x
and metal overlayer of Ag are studied with a view to control the interfacial property of contact resistance. The interface
reaction is induced by 100 keV Ar+ ion beam with different ion dose values ranging from 5 × 1013 to 3×1014 ions/cm2. The YBaCuO film-metal interface is characterized by using the small angle XRD to study the structural properties of the
interfacial phases. The electrical property of the interface, specifically contact resistance, has been investigated for different
dose values and thermal treatments. Three-probe vs four-probe configuration has been adopted to measure the contact resistance. 相似文献
76.
77.
S. R. Sawant D. N. Bhosale N. D. Chaudhari P. P. Bakare 《Journal of Materials Science: Materials in Electronics》2002,13(5):277-283
Compositions of Ni0.32Zn0.68-2xLixFe2+xO4 with x=0.0, 0.025, 0.050, 0.075, 0.100, 0.125, 0.150, 0.175, 0.200 were prepared by oxalate precursors. The Ms–T curves resemble type R. The magnetic moment (nB) values were found to increase with increase of Li1+ content up to x=0.175, and thereafter it decreased. The former explained on the basis of the exchange interactions, whereas the decrease of nB is related to the migration of Ni to tetrahedral (A) sites. There is a decrease in Yafet–Kittle (Y–K) angles at octahedral (B) sites, suggesting that lithium does not favor Hc canting. Actually, Li1+ tends to reduce canting, resulting in the increase of nB coercive force (Hc) and remanance ratio (R) variations have been related to increase of anisotropy constant (Kl) with increasing Li1+ content. The values of R are comparable with the theoretical value, 0.87, which is probably due to the very high density of the samples. Thermal variations of Hc and R reveal that neither parameter changes rapidly with increasing temperature, indicating that the material contains multi-domain (MD) grains in predominance. These results are also supported by a.c. susceptibility studies. The values of wall susceptibility are higher than those of rotational susceptibility, suggesting that the susceptibility is contributed mainly by the domain wall motion. 相似文献
78.
Business process transformation defines a new level of business optimization that manifests as a range of industry-specific initiatives that bring processes, people, and information together to optimize efficiency. This new optimization level is possible because the Web has assumed the role of a common infrastructure. To examine how BPT can optimize an organization's processes, we describe a corporate initiative that was developed within IBM's supply chain organization to transform the import compliance process that supports the company's global logistics. The initiative sought to give IBM greater awareness of regulatory compliance exceptions - information critical to the corporation and its importing partners. 相似文献
79.
In recent years laser processing has attracted much attention in view of its potential use in basic solid-state and material
science research as well as in new processing technologies. The dominant feature of laser processing being the deposition
of large amounts of energy (a few J/cm2) over very short time scales (a few tens of nanoseconds), it leads to melting of surface layers of solid followed by rapid
resolidification. In this article, a few basic consequences of such laser-induced phenomena in silicon are reviewed. 相似文献
80.
Vikas G. Sadvilkar Srinivas D. Samant Vilas G. Gaikar 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,62(4):405-410
The Claisen–Schmidt condensation of benzaldehydes with acetophenones was carried out in an aqueous medium using sodium butylmonoglycolsulfate (NaBMGS) and sodium salts of aromatic sulfonic acids as hydrotropes. Substantial enhancement in the rate of the reaction was obtained, along with the easy recovery of the product. Recycling of the hydrotrope solutions has been tested without any loss in the rate of the reaction. 相似文献