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71.
72.
Densities and sound velocities of binary mixtures of cyclohexanone, 2-butanone, 1,4-dioxane and 1,2-dimethoxyethane were measured
at 298.15 K and also the densities at 303.15 K. Excess volumes were determined from densities. Isentropic compressibilities
were determined from densities and sound velocities, and excess thermal expansion factors were determined from excess volumes
of two temperatures. Excess isothermal compressibilities and excess isochoric heat capacities were then estimated using excess
isobaric heat capacities previously reported. Excess volumes and excess isentropic and isothermal compressibilities were negative
except for cyclohexanone+1,4-dioxane system.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
73.
Chenmou Zheng Xinmin Zhang Shan He Qun Fu Deming Lei 《Journal of solid state chemistry》2003,170(2):221-226
V2O3 nanopowder with spherical particles was prepared by reducing pyrolysis of the precursor, (NH4)5[(VO)6(CO3)4(OH)9]·10H2O, in H2 atmosphere. The thermolysis process of the precursor in a H2 flow was investigated by thermogravimetric analysis and differential thermal analysis. The results indicate that pure V2O3 forms at 620°C and crystallizes at 730°C. The effects of various reductive pyrolysis conditions on compositions of V2O3 products were studied. Scanning electron micrographs show that the particles of the V2O3 powder obtained at 650°C for 1 h are spherical about 30 nm in size with more homogeneous distribution. Experiments show that nanopowder has larger adsorption capacity to gases and is more easily reoxidized by air at room temperature than micropowder. Differential scanning calorimetry experiment indicates that the temperature of phase transition of nano-V2O3 powder is −119.5°C on cooling or −99.2°C on heating. The transition heats are −12.55 J g−1 on cooling and 11.42 J g−1 on heating, respectively. 相似文献
74.
Thermal decomposition of Bi(SCN)3, Cd(SCN)2, Pb(SCN)2 and Cu(SCN)2 has been studied. The thermal analysis curves and the diffraction patterns of the solid intermediate and final products of the pyrolysis are presented. The gaseous products of the decomposition (SO2 and CO2) were detected and quantitatively determined. Thermal, X-ray and chemical analyses have been used to establish the nature of the reactions occurring at each stage in the decomposition.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
75.
A model for the dynamics of isothermal absorption of a binary mixture of an organic substance, soluble in water, and water
vapor in a fixed bed of activated carbon was proposed. It includes the equations of material balance and the Myers—Prausnitz
model for equilibrium adsorption. The possibility of formation of the condensed phase during the adsorption of an organic
substance on moist activated carbon was shown.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1491–1495, August, 1998. 相似文献
76.
Fini P. Castagnolo M. Catucci L. Cosma P. Agostiano A. 《Journal of Thermal Analysis and Calorimetry》2003,73(2):653-659
Equilibrium constants and standard molar enthalpies of reaction were determined by titration calorimetry for the reaction
of 1-butanol with 2-hydroxypropyl-b-cyclodextrin (HP-b-CD) in aqueous solution at different concentrations of NaCl (0-1.9
M). The standard molar free energy and entropy changes associated to the complexation were calculated from the corresponding
equilibrium constants, K, and standard enthalpies determined experimentally. In NaCl solutions the inclusion complexes ButOH/HP-b-CD are more stable
than in water and their stability increases at increasing NaCl concentration; otherwise, the standard molar enthalpy associated
to the formation of the complexes does not change with the increasing of salt concentration. The dependence of K on NaCl concentration were used to evaluate the number of water molecules displaced from the hydration shells of HP-b-CD
and ButOH in forming complexes.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
77.
Gregor Trimmel Rita Badheka Florence Babonneau Jerome Latournerie Phillip Dempsey Djamila Bahloul-Houlier Julien Parmentier Gian Domenico Soraru 《Journal of Sol-Gel Science and Technology》2003,26(1-3):279-283
The sol-gel method was used to prepare two different starting gels containing SiCH3-groups for the preparation of SiOC ceramics. To understand the role of Si—H bonds in the incorporation of carbon into the SiOC network, gels prepared from a 1:2 mixture of triethoxysilane and methyldiethoxysilane (THDH2) and solely methyltriethoxysilane (TMe) were investigated. Thermogravimetric analysis coupled with mass spectroscopy (TG-MS) in inert atmosphere was performed to attain an insight into the decomposition reactions involved during gel-glass transformation. Samples calcined at different temperatures up to 1000°C were characterized by 29Si and 13C magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. The presence of SiH groups in the starting gel allows an efficient conversion of Si—CH3 groups into CSi4 sites at lower temperatures. As a result, despite a much lower amount of carbon in the starting THDH2 gel (C/Si = 0.33) compared to the TMe gel (C/Si = 1), the amount of carbon inserted into the SiOC network of both glasses is equivalent, but the TMe sample contains the 10 fold amount of free carbon. 相似文献
78.
炉前煤低温干馏工艺中的挥发分除尘 总被引:3,自引:1,他引:3
为了寻求优化的炉前煤低温干馏工艺中的挥发分除尘方案,在使用400目金属滤网对间歇式粉煤固体热载体热解装置挥发分除尘研究的基础上,将颗粒床过滤器用于该过程的除尘研究。热态除尘实验表明,颗粒床的使用有效地降低了滤网的过滤负荷。选用2mm石英砂和φ5mm×2mm瓷环作为滤料,通过对比实验发现,两种滤料除尘效率均在90%以上;随着过滤操作的进行,由于颗粒床内粉尘的沉积使其过滤效率有所提高,而对气、液收率的影响很小。结果表明,颗粒床与滤网结合可作为粉煤炉前低温干馏工艺中可供选择的挥发分除尘方案。 相似文献
79.
纤维素热裂解反应机理及中间产物生成过程模拟研究 总被引:4,自引:3,他引:4
基于改进的B-S机理模型,通过求解物料内部和气相空间两段反应过程,对纤维素热裂解过程中一些化合物(活性纤维素、左旋葡聚糖(LG)、乙醇醛、丙酮醇等组分)的生成和演变情况进行了模拟。结果发现,自由水的脱除过程使物料前期升温速率发生了下降,并未影响热解期间温度分布以及反应过程。热裂解过程中,由于一次反应的强烈吸热,物料在长时间内局限于中温范围,其内部各组分质量浓度分布的区别主要体现出一次反应竞争能力的强弱。物料厚度的增加使热裂解时间延长,并加剧物料内部的二次分解。左旋葡聚糖和其竞争产物乙醇醛的生成出现一个大量生成、快速逃逸的过程,相比于左旋葡聚糖,乙醇醛质量浓度的积累具有更快的速度,体现出较高温度下的竞争优势。对于小尺寸反应物,挥发分二次反应主要发生在气相空间,随着气相停留时间的增加,其二次分解的程度提高,该效果随辐射源温度的提高而加剧。相比于LG产率随反应时间的快速下降趋势,高温下生物油产率的降低略显缓和,其变化主要是组分分布的改变,即从大分子结构降解为小分子结构。 相似文献
80.
Zinc sulfide (ZnS) thin films have been deposited on Si (1 0 0) substrate using ultrasonic spray pyrolysis. X-ray diffraction (XRD) analysis revealed that the films are (0 0 2) preferentially oriented with c-axis-oriented wurtzite structure. The crystallinity has been found to improve with film thickness in the 180–6000 nm range. Film structure has been analyzed by XRD, scanning electron microscope, FTIR, and Raman spectroscopies, while the stoichiometry has been verified by energy-dispersive spectroscopy and particle-induced X-ray emission techniques. Electrical properties of the grown films were characterized by current–voltage and capacitance–voltage measurements where, the films show better conducting behavior at higher thickness. 相似文献