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61.
Powders based on plant raw materials have low storage stability due to their sorption and thermal properties and generate problems during processing. Therefore, there is a need to find carrier agents to improve their storage life as well as methods to evaluate their properties during storage. Water adsorption isotherms and thermal characteristics of the pumpkin powder with various inulin additions were investigated in order to develop state diagrams. Differential scanning calorimetry (DSC) was used to obtained glass transition lines, freezing curves and maximal-freeze-concentration conditions. The glass transition lines were developed using the Gordon–Taylor model. Freezing data were modeled employing the Clausius–Clapeyron equation and its development–Chen model. The glass transition temperature of anhydrous material (Tgs) and characteristic glass transition temperature of maximum-freeze-concentration (Tg′) increased with growing inulin additions. Sorption isotherms of the powders were determined at 25 °C by the static-gravimetric method and the experimental data was modeled with four different mathematical models. The Peleg model was the most adequate to describe the sorption data of the pumpkin–inulin powders. Guggenheim-Anderson-de Boer (GAB) monolayer capacity decreased with increasing inulin concentration in the sample. 相似文献
62.
63.
The electrochemical behavior of a nickel electrode with limited volume (LVE) electrodeposited as a thin layer on gold has
been studied. The influence of the gold matrix on the electrochemical Ni electrode behavior has been considered. The electrosorption
and oxidation of carbon monoxide on the Ni surface and its influence on hydrogen sorption has also been demonstrated.
Received: 21 May 1997 / Accepted: 9 June 1997 相似文献
64.
B. G. Ershov A. F. Seliverstov N. L. Sukhov G. L. Bykov 《Russian Chemical Bulletin》1992,41(10):1805-1809
The sorption of Cu2+ ions by chitin and chitosan from aqueous solutions has been investigated, as well as the molecular structure of the complexes formed. The static exchange capacities have been determined, equal to 3.5 and 0.25 mmole/g for chitosan and chitin, respectively, and the partition coefficients (5000 and 70 g/ml). It has been shown that in complex formation a bond with the amino group is formed as the result of the substitution of a proton in the latter. The EPR spectra of these complexes have been obtained and their radiospectroscopic parameters determined (g
= 2.334,g
= 2.054,A = 0.0156 cm–1, andB = 0.0028 cm–1 for chitin, andg
= 2.231,g
= 2.048,A = 0.0192 cm–1, andB = 0.0025 cm–1 for chitosan). For chitosan the ligands are two nitrogen atoms of the amino groups and two oxygen atoms of the hydroxyl groups in the position C3 of adjacent glucosamine rings; for chitin, the oxygen atoms of the acetyl groups take part in addition in the complex formation. The analysis of the radiospectroscopic parameters and their comparison with published data lead to the conclusion that the Cu2+ complex with chitosan has a tetragonal symmetry, while the complex with chitin most probably has an octahedral structure.Institute of Physical Chemistry, Russian Academy of Sciences, 117915 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2305–2311, October, 1992. 相似文献
65.
L. G. Gordeeva J. Mrowiec-Bialon A. B. Jarzebski A. I. Lachowski J. J. Malinowski Yu. I. Aristov 《Reaction Kinetics and Catalysis Letters》1999,66(1):113-120
This paper presents sorption properties of CaCl2/SiO2 composites synthesized by a sol-gel approach. Desorption isobars measured at T=30–140°C and vapor pressure 12.8–81.0 mbar
clearly show a correlation between the sorbents pore structure and their sorption properties. The sample adsorptivities are
found to exceed 1.2 kg H2O/kg adsorbent (or 20–25 mol H2O/mol of the salt). That is markedly higher than any reported before for silica-based materials. This results in a high energy
storage capacity reaching 3,400 kJ/kg of dry sorbent, as confirmed by direct calorimetric measurements. The isosteric desorption
heat is found to decrease from 67±5 kJ/mol to 46±5 kJ/mol with increase in the surface coverage. 相似文献
66.
Ivana Brekalo David E. Deliz Leonard J. Barbour Michael D. Ward Tomislav Fri
i K. Travis Holman 《Angewandte Chemie (International ed. in English)》2020,59(5):1997-2002
Guanidinium organosulfonates (GSs) are a large and well‐explored archetypal family of hydrogen‐bonded organic host frameworks that have, over the past 25 years, been regarded as nonporous. Reported here is the only example to date of a conventionally microporous GS host phase, namely guanidinium 1,4‐benzenedisulfonate ( p ‐G2BDS ). p ‐G2BDS is obtained from its acetone solvate, AcMe@ G2BDS , by single‐crystal‐to‐single‐crystal (SC‐SC) desolvation, and exhibits a Type I low‐temperature/pressure N2 sorption isotherm (SABET=408.7(2) m2 g?1, 77 K). SC‐SC sorption of N2, CO2, Xe, and AcMe by p ‐G2BDS is explored under various conditions and X‐ray diffraction provides a measurement of the high‐pressure, room temperature Xe and CO2 sorption isotherms. Though p ‐G2BDS is formally metastable relative to the “collapsed”, nonporous polymorph, np ‐G2BDS , a sample of p ‐G2BDS survived for almost two decades under ambient conditions. np ‐G2BDS reverts to zCO2@ p ‐G2BDS or yXe@ p ‐G2BDS (y,z=variable) when pressure of CO2 or Xe, respectively, is applied. 相似文献
67.
本文针对气体透过薄膜的传质过程,基于动态吸附、扩散传递的概念,根据Langmuir界面动态吸附理论,研究了存在定向传递时表面吸附量与平衡吸附量的差异,从而将膜相传质分为吸附、内部扩散和脱附三个动态过程.讨论了界面吸附、脱附与扩散对传质阻力的不同影响,建立了薄膜传质的串联阻力模型. 相似文献
68.
69.
Ken-Ichi Okamoto Nozomu Tanihara Hitoshi Watanabe Kazuhiro Tanaka Hidetoshi Kita Asumaru Nakamura Yoshihiro Kusuki Kanji Nakagawa 《Journal of Polymer Science.Polymer Physics》1992,30(11):1223-1231
Sorption and diffusion of water vapor are investigated gravimetrically for polyimide films. The activity dependence of the solubility and diffusion coefficients, S and D, respectively, is classified under four types: (1) constant S and D type, (2) dual-mode sorption and transport type, (3) dual-mode type followed by a deviation due to a plasticization effect at high vapor activity, and (4) constant S and D type followed by a deviation due to water cluster formation at high activity. For the dual-mode type, the Henry's law component is much larger than the Langmuir component except at low activity, and therefore deviation in behavior from the first type is small. S is larger for polyimides with higher content of polar groups such as carbonyl, carboxyl, and sulfonyl. D is larger for polyimides with a higher fraction of free space, with some exceptions. The polyimide from 3,3′,4,4′-biphenyltetracarboxylic dianhydride and dimethyl-3,7-diaminodibenzothiophene-5, 5-dioxide belongs to the third type and displays both large S and large D. The polyimide from 2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride and 4,4′-oxydianiline belongs to the fourth type, and has the largest D but rather small S because of the hydrophobic C(CF3)2 groups. © 1992 John Wiley & Sons, Inc. 相似文献
70.
The temperature dependence of gas sorption and transport properties is examined for two polyimide isomers. The permeabilities and solubilities of five gases in these materials are reported over an extensive temperature range from 35 to 325°C. Also, the activation energies for permeation, the heats of sorption, and the activation energies for diffusion obtained for both polyimides are compared and correlated with physical properties of the polymers and penetrants. The influence of temperature on the selective properties of these membrane materials is discussed for three gas separations; He/N2, CO2/CH4, and O2/N2. Thorough analysis of these data provides insight into the influence of the subtle difference in chain structure of the two isomers. The performance of the 6FDA-6Fp DA as a separation membrane at high temperatures suggests that it is an outstanding candidate for use in novel elevated temperature applications. ©1995 John Wiley & Sons, Inc. 相似文献