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91.
92.
A highly enantioselective synthesis of 3-amino-2-oxindoles by direct Mannich reaction between acetylacetone and N-carbamoyl isatin ketimine has been described herein. Corresponding chiral adducts were obtained in high yields (up to 98%) and with excellent enantioselectivities (up to?>99% ee) by very low (1?mol%) catalyst loading of 2-adamantyl substituted bifunctional cinchona-squaramide. 相似文献
93.
The eutectic mixture of octacosane (C28)–heptadecane (C17) as core material was successfully encapsulated with an acrylic-based polymer (polymethylmethacrylate; PMMA) as shell material through emulsion polymerization. The polymeric reaction occurred around the core material was characterized by FTIR spectroscopy analysis. The polarized optical microscopy, scanning electron microscopy and particle size distribution investigations showed that the most of the prepared capsules had almost spherical shape with non-unimodal size distribution in micro-nano range. The differential scanning calorimetry analysis results exhibited that the capsules including highest amount of the eutectic PCM had a melting temperature of about 21°C and a latent heat capacity of about 98 J/g. The high thermal durability of the prepared capsules was confirmed by thermogravimetric analysis. The thermal cycling test designated that the synthesized capsules had good long-term usage latent heat thermal energy storage (LHTES) performance and chemical stability. Furthermore; the fabricated capsules with (1: 2) shell/core ratio had a reasonable thermal conductivity. It can be drawn a conclusion from all results that the prepared capsules especially PMMA/(C28–C17) (1: 2) product is a hopeful PCM that can be evaluated for low-temperature LHTES applications. 相似文献
94.
A single-phase Zn-0·25 wt. % Cd alloy was prepared with the mean grain sized¯ 1m. Superplastic characteristics (A
max=320% andm
max>0·4) were established at room temperature at the strain rates.10–4s–1. Because of the absence of any second phase particles the fine-grained structure was not stable and an intense grain coarsening was observed both during the long-term ageing and during straining at room temperature. The increasing temperature accelerated this grain coarsening and suppressed the superplastic behaviour. Nevertheless, the stress relaxation tests suggested that the superplastic behaviour might be expected at higher temperatures in coarser grained specimens, too, but at substantially lower strain rates. 相似文献
95.
The 3,5‐bis(5‐carboxy‐6‐azauracil‐1‐yl)aniline ( 7 ) and 1,3,5‐tris(5‐carboxy‐6‐azauracil‐1‐yl)benzene ( 10 ) were prepared from 3‐amino‐5‐nitroacetanilide ( 1 ) via intermediates 2–6 . A series of other substituted 6‐azauracil derivatives 9, 11‐14 were also prepared. 相似文献
96.
A novel method has been developed for determining the surface acidity of white, as well as deeply colored porous solids. The method, which was tested on Al2O3, SiO2–MgO–Al2O3 and Fe2O3 catalysts, is based on the adsorption of pyridine or benzylamine on acidic sites and subsequent displacement of the adsorbed bases by n-butylamine. A linear correlation was found between the concentration of acidic sites on Al2O3 and Fe2O3 catalysts and their activity in the dehydration oftert-butyl alcohol.
, . , Al2O3, SiO2–MgO–Al2O3 Fe2O3, -. Al2O3 Fe2O3 - .相似文献
97.
M. Ziólek 《Reaction Kinetics and Catalysis Letters》1983,23(3-4):371-374
The X-ray and IR studies of faujasite-type zeolites after sulfur dioxide adsorption showed that in the case of X-type zeolites a partial destruction of the zeolite lattice occurred. The modified X-type zeolites have smaller resistance to the SO2 treatment. No influence of sulfur dioxide on the structure of Y-type zeolites was observed.
- , , , . .相似文献
98.
99.
A unified theory for the kinetic analysis of solid state reactions under any thermal pathway 总被引:1,自引:0,他引:1
Criado J. M. Pérez-Maqueda L. A. Gotor F. J. Málek J. Koga N. 《Journal of Thermal Analysis and Calorimetry》2003,72(3):901-906
The Ozawa concept of generalized time has been used for developing master plots for the different kinetic models describing
solid state reactions. These plots can be indistinctly used for analysing isothermal or non-isothermal experimental data.
It is demonstrated that it is not possible to discriminate the kinetic model from a single non-isothermal curve without a
previous knowledge of the activation energy. However, it has been shown that the ln [(da/dt)/f(a)] data taken from a set of DTG curves obtained at different heating rates lie on a single straight line when represented
as a function of 1/T only if the kinetic model really obeyed by the reaction is considered. Moreover, the true values of E and A are obtained from the slope and the intercept of this straight line.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
100.
Two series of compounds have been synthesized: 1,2-bis(4′-butoxybenzeneazobenzene-4)ethanes and 1,2-bis(4′-butoxybenzeneazoxybenzene-4)ethanes. The effects of lateral substituents (CH3, Cl, CN) on temperature are tested as well as the molar enthalpies and entropies of their phase transitions determined. The application of those compounds as liquid-crystalline stationary phases in gas chromatography is suggested. 相似文献