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1.
V. Yu. Gus’kov F. Kh. Kudasheva G. B. Bogolyuk 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2013,87(5):879-881
The dependence of the specific retention volumes of sorbates on their concentration in the gas phase is investigated. It is shown that the slope tangent of the dependence is related to the second coefficient of the virial expansion of adsorption isotherm. It is established that the free energy of sorbate-sorbate interactions on the surface of porous polymer sorbents is constant for all investigated molecules. An equation for calculating retention volumes at different sorbate concentrations is proposed. 相似文献
2.
A. V. Konstantinov R. V. Shafigulin M. M. Il’in V. A. Davankov A. V. Bulanova P. P. Purygin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2013,87(6):1039-1042
The results from chromatographic analysis of biologically active isatin derivatives on hyper-crosslinked polystyrene (HCLPS) and silica gel modified by octadecyl groups (SilC18) are presented. The constants of distribution of sorbates between a mobile phase and the investigated sorbents (K x ) and the changes in the standard differential molar Gibbs energies of adsorption $(\Delta _a \bar G^\circ )$ are calculated, along with the chromatographic retention-physicochemical property of sorbate dependences. It is found that the equations describing these dependences have high forecasting ability with respect to the values of retention factors of the investigated sorbates. 相似文献
3.
S. N. Yashkin 《Russian Chemical Bulletin》2010,59(11):2026-2038
The thermodynamic characteristics of adsorption of adamantane molecules and its alkyl derivatives, as well as some mono- and
bicyclic hydrocarbons C10H
n
, were studied by equilibrium gas liquid chromatography on a column packed with the stationary liquid phase squalane under
the conditions of infinitely low concentrations of the sorbate in the gas phase. The influence of specific features of the
molecular structure of sorbates on the regularities of their retention on the column with squalane was shown. For the first
time we obtained the limiting activity coefficients and excess thermodynamic functions of mixing, which made it possible to
study in detail the thermodynamics of dissolution of cage molecules in the nonpolar liquid bulk. The changes in the molar
isobaric heat capacity of sorbates during adsorption were determined by the chromatographic method. For reference compounds,
these values agree well with the results of direct calorimetric measurements of the change in the molar standard isobaric
heat capacity during vaporization. 相似文献
4.
Nonideal interactions of the sorbate and the carrier gas and adsorption of the sorbate on the adsorbent surface in capillary gas-solid chromatography were studied. Chromatographic retention was found to be largely determined by adsorption processes. With respect to the retention coefficients (capacity factors) of a sorbate (k) with different carrier gases (P1 and P2), the correlation relationshipk(P2) =A·k(P1) +B (A, B are parameters of the equation) is closely obeyed. The advantages of carbon dioxide as the carrier gas were analyzed; the use of carbon dioxide allows the efficiency of the column to be enhanced.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 627–633, March, 1996. 相似文献
5.
水介质中氢键吸附与疏水吸附协同作用的研究 总被引:7,自引:0,他引:7
研究了丙烯酸型树脂(D152)在水、乙醇和正己烷中对苯胺、N-甲基苯胺和N,N-二甲基苯胺的吸附行为.在水中D152树脂对3种吸附质的吸附亲合性随N上甲基数的增加而增大,说明疏水作用是主要的吸附机理,但其吸附焓己超出范德华力的范围而在氢键的键能范围内,故氢键吸附也同时在起作用.在正己烷中,D152树脂对3种吸附质的吸附亲合性随N上甲基数的增加而减小,与水中呈相反的趋势,说明氢键作用是主要的吸附机理.在乙醇中,D152树脂对3种吸附质均无吸附,因为疏水作用和氢键作用均受到的乙醇抑制.在水中,吸附质与树脂间的氢键作用同样受到水的抑制,但氢键吸附却依然存在,说明水介质中氢键吸附和疏水吸附可能存在一种协同作用.在热力学上对水介质中氢键吸附和疏水吸附的协同作用给于合理的解释. 相似文献
6.
The adsorption of CO2 on a number of activated carbons, thermal carbon black, and oxide materials at 195 K was studied using static and dynamic
techniques. The landing surface areas ω(CO2) ≈ 0.19 nm2 on thermal carbon black and the absolute values of sorption for P/P
0 < 0.4 were determined. The density of adsorbed CO2 in the micropore volume was estimated at ρ(CO2) = 0.91 g/cm3. It was demonstrated that the previously found effect of a weakening of the sorption interaction of nitrogen molecules with
thin-walled materials (which manifested itself in an analysis of sorption isotherms by a comparative method) was pronounced
to a lesser degree for the sorption of CO2. At the same time, the presence of supermicropores in activated carbon samples resulted in overestimated values of surface
areas. A dynamic method was proposed to measure the spectra of CO2 desorption at 195–260 K using a SORBI-MS system for evaluating the binding energy of sorbate molecules with the surface. 相似文献
7.
I. B. Obot N. O. Obi-Egbedi E. E. Ebenso A. S. Afolabi E. E Oguzie 《Research on Chemical Intermediates》2013,39(5):1927-1948
2-(6-Methylpyridin-2-yl)oxazolo[5,4-f][1,10]phenanthroline (MOP) was synthesized and characterized by elemental analysis and Fourier-transform infrared (FT-IR), 1H nuclear magnetic resonance (NMR), and 13C NMR spectra. MOP was evaluated as a corrosion inhibitor for carbon steel in 0.5 M H2SO4 solution using the standard gravimetric technique at 303–333 K. Quantum chemical calculations and molecular dynamic (MD) simulations were applied to analyze the experimental data and elucidate the adsorption behavior and inhibition mechanism of MOP. Results obtained show that MOP is an efficient inhibitor for mild steel in H2SO4 solution. The inhibition efficiency was found to increase with increase in MOP concentration but decreased with temperature. Activation parameters and Gibbs free energy for the adsorption process using statistical physics were calculated and discussed. The adsorption of MOP was found to involve both physical and chemical adsorption mechanisms. Density functional theory (DFT) calculations suggest that nitrogen and oxygen atoms present in the MOP structure were the active reaction sites for the inhibitor adsorption on mild steel surface via donor–acceptor interactions between the lone pairs on nitrogen and oxygen atoms together with the π-electrons of the heterocyclic and the vacant d-orbital of iron atoms. The adsorption of MOP on Fe (1 1 0) surface was parallel to the surface so as to maximize contact, as shown in the MD simulations. The experiments together with DFT and MD simulations provide further insight into the mechanism of interaction between MOP and mild steel. 相似文献
8.
Vinh-Thang H Huang Q Eić M Trong-On D Kaliaguine S 《Langmuir : the ACS journal of surfaces and colloids》2005,21(11):5094-5101
In our recent studies (Vinh-Thang, H.; Huang, Q.; Eic, M.; Trong-On, D.; Kaliaguine, S. Langmuir 2005, 21, 2051-2057; Vinh-Thang, H.; Huang, Q.; Eic, M.; Trong-On, D.; Kaliaguine, S. Stud. Surf. Sci. Catal. 2005, in press), a series of synthesized SBA-15 materials were characterized using nitrogen adsorption/desorption isotherms at 77 K and SEM images. In the present paper, four of them (MMS-1-RT, MMS-1-60, MMS-1-80, and MMS-5-80) were further investigated with regard to their equilibrium characteristics using n-heptane and toluene as sorbates by the standard gravimetric technique. SBA-15 materials proved to have a broad pore size distribution within the micropore/small-mesopore range in the walls of their main mesoporous channels. The adsorption capacities for toluene were found to be higher than for n-heptane. The isosteric heats of adsorption, estimated by the Clausius-Clapeyron equation, are also higher for toluene compared to n-heptane. They were found to depend on framework microporosity of the relevant SBA-15 samples. The isosteric heats of adsorption for all sorbates decrease with increased loading and approach the heats of evaporation of the respective sorbate. The adsorption capacities of SBA-15 samples are significantly higher than those of silicalite, i.e., the MFI zeolite silica analogue. In contrast to that, the isosteric heats of adsorption in the mesopore channels of SBA-15 were found to be much smaller. This result also suggests that SBA-15 can potentially be a good candidate for separation of C(7) hydrocarbons. 相似文献
9.
S. N. Lanin E. B. Pashkova N. V. Kovaleva K. S. Lanina 《Russian Chemical Bulletin》2009,58(4):729-732
Adsorption of light and heavy water (H2O and D2O) on porous hypercross-linked polystyrene MN-272 was studied by gas chromatography. For the estimation of the properties
of this polymer surface, n-alkanes (C6—C9), C6
6, and polar compounds (CHCl3, MeNO2, MeCN, Me2CO, EtCOOCH3, Et2O) were used as test adsorbates. The contributions of energies of dispersion and specific (donor-acceptor) intermolecular
interactions to the total energy of adsorption were determined on the basis of experimental data on the retention of the sorbates.
The electron-donor and electron-acceptor characteristics of the hypercross-linked polystyrene MN-272 surface were estimated.
Hypercross-linked polystyrene MN-272 was found to be a weakly specific adsorbent with predomination of electron-donating properties.
The adsorption isotherms of H2O and D2O were measured on this polymer at 50, 60, and 70 °C. The dependences of the isosteric heats of adsorption on the amount adsorbed
were determined. The contribution of the energy of specific interactions to the total energy of adsorption for all polar adsorbates
(except for acetone, light and heavy water) does not exceed 20%. Adsorption of H2O on hypercross -linked polystyrene MN-272 is slightly weaker than that of D 2O. 相似文献
10.
Mikhail Borisover 《Adsorption》2013,19(2-4):241-250
The effect of organic sorbates on the water associated with naturally occurring sorbents is of significant interest since it probes the hydration of a sorbate-specific microenvironment and its role in a compound partitioning between various environmental compartments. This effect was described in a thermodynamically strict way by converting the sorption isotherms of organic vapors on variously hydrated sorbents into the derivatives relating the change in the amount of water associated with a sorbent to the change in the amount of an organic sorbate. Further, these derivatives were analyzed by means of the Linear Free Energy Relationship (LFER). The analysis included the sorption data for various organic vapors on such environmentally important sorbents as quartz, metal oxides, calcite, clay minerals and humic acid. From the LFER analysis it followed that (i) organic sorbate polarizability contributions from n- and π-electrons resulted in driving water into the sorbent phase; (ii) the increasing volume of the organic compounds involved expelling water molecules; (iii) the increasing hydrogen-bond acidity and basicity of organic sorbates resulted in expelling water from inorganic surfaces but in enhancing hydration of the humic phase. In contrast to inorganic surfaces, when sorbed on strongly hydrated humic acid, the majority of organic sorbates containing oxygen, nitrogen or sulfur atoms drive water into the sorbent phase. Several molecules of water may need to be cosorbed by a humic sorbent for each sorbed molecule of an organic compound thus supporting the possibility of the concomitant participation of a number of water molecules in organic sorbate–humic matter interactions. 相似文献
11.
We evaluated the ability of CO2 adsorption in functionalized activated carbons granular and monolithic type, obtained by chemical activation of African palm stone with H3PO4 and CaCl2. We made a comparison between two methods of incorporation of nitrogen groups: the impregnation method with NH4OH solution and NH3 gasification. The materials were texturally characterized by N2 adsorption at 77 K, the isotherms shows obtaining microporous materials with surface areas between 545–1425 m2?g?1 and pore volumes between 0.22 to 0.53 cm3?g?1. It was established that with the methodologies used for functionalization is increased content of nitrogen groups, was achieved a higher proportion of such groups when carrying out the process in liquid phase with NH4OH. The incorporation of nitrogen groups in the material generates an increase of up to 65 % in the CO2 adsorption capacity of the MCa2 (Monolith prepared with CaCl2 solution at 2 %) sample. Was reached a maximum adsorption capacity of 344 mgCO2?g?1 in the MCa2FAL (sample MCa2 functionalized with NH4OH solution) sample. 相似文献
12.
Seul-Yi Lee Hye-Min Yoo Kyong Yop Rhee Soo-Jin Park 《Research on Chemical Intermediates》2014,40(7):2535-2542
Ordered nanoporous carbons (ONCs) were prepared using a soft-templating method. To improve the CO2 adsorption efficiency, ONCs were chemically activated to obtain high specific surface area and micro-/mesopore volume with different KOH amounts (i.e., 0, 1, 2, 3, and 4) as an activating agent. The prepared nanoporous carbons (NCs) materials were analyzed by low-angle X-ray diffraction for confirmation of synthesized ONCs structures. The structural properties of the NCs materials were analyzed by high-angle X-ray diffraction. The textural properties of the NCs materials were examined using the N2/77 K adsorption isotherms according to the Brunauer–Emmett–Teller equation. The CO2 adsorption capacity was measured by CO2 isothermal adsorption at 298 K/1 bar. From the results, the NCs activated with KOH showed that the increasing specific surface areas and total pore volumes resulted in the enhancement of CO2 adsorption capacity. 相似文献
13.
Diana P. Vargas L. Giraldo J. C. Moreno-Piraján 《Journal of Thermal Analysis and Calorimetry》2014,117(3):1299-1309
Given the great interest in the CO2 removal and decreasing their impact on the environment, in this work, a calorimetric study of CO2 adsorption on different activated carbons was performed. For this purpose, we used two methodologies for the determination heat of CO2 adsorption: determination of CO2 isotherms at different temperatures and adsorption calorimetry. The heats determined by these two techniques were compared. In this regard, carbonaceous materials of granular and monolithic types were prepared, characterized, and functionalized for carbon dioxide adsorption. As precursor material, African palm stones that were activated with H3PO4 and CaCl2 at different concentrations was used. The obtained materials were functionalized in gas phase with NH3 and liquid phase with NH4OH, with the intention to incorporate the surface basic groups (amines or nitrogen groups) and subsequently were studied for CO2 adsorption at 273 K and atmospheric pressure. For characterization of these materials, the following techniques are used: N2 adsorption at 77 K and immersion calorimetry in different solvents. The experimental results show the obtaining of micropores and mesoporous (moderately) materials, with surface area between 430 and 1,425 m2 g?1 and pore volumes between 0.17 and 0.53 cm3 g?1. It was determined that there is a difference between the heats of CO2 adsorption obtained by the techniques employed. This deviation between the values corresponds to the methodological difference between the two experiments. In this work, we obtained a maximum adsorption capacity of CO2, which is greater than 334 mg CO2 g?1 at 273 K and 1 bar in carbon materials with moderate surface area and pores volume. 相似文献
14.
15.
L. N. Obolenskaya G. M. Kuz’micheva E. V. Savinkina N. V. Sadovskaya A. V. Zhilkina N. A. Prokudina V. V. Chernyshev 《Russian Chemical Bulletin》2012,61(11):2049-2055
The nanosized anatase modification of titanium dioxide was prepared from two forms of solvated titanyl sulfate (TiOSO4·2H2O and TiOSO4·xH2SO4·yH2O) at different initial concentrations of the reagent under different conditions of the hydrolysis and coagulation. The sample characteristics (the sizes of aggregates, microparticles, nanoparticles, and coherent scattering regions, the specific surface area, the nano- and ultrananopore volumes) were deter-mined by scanning electron microscopy, small-angle and wide-angle X-ray diffraction, and physical adsorption of nitrogen at ?196 °C. The relationship between these characteristics and the conditions of the sample preparation was established. The optimal processing conditions were found for the synthesis of samples with a high practical yield of the anatase-type phase. 相似文献
16.
Effective adsorption of CO2 at low partial pressures is required for many technical processes, such as gas purification or CO2 removal in closed loop environmental control systems. Since the concentration of CO2 in such applications is rather low, a high adsorption capacity is a required property for the adsorbent. Silica aerogels possessing an open pore structure, a high porosity and a high surface area, have a great potential for utilisation as CO2 adsorbents. Nonetheless in order to reach high adsorption capacities, silica aerogels should be functionalised, for instance by amino functionalisation. In this work, two different functionalisation methods were applied for the generation of amino functionalised aerogels: co-condensation during the sol-gel process and post-treatment of the gel. The co-condensation functionalisation allows the introduction of up to 1.44 wt.% nitrogen into the aerogel structure with minor reductions in surface area, leading however only to minor increases in the adsorption capacity at low partial pressures. The post functionalisation of the gel causes a greater loss in surface area, but the CO2 adsorption capacity increases, due to the introduction of higher amounts of amino groups into the aerogel structure (up to 5.2 wt.% nitrogen). Respectively, 0.523 mmol CO2/g aerogel could be adsorbed at 250 Pa. This value is comparable with the adsorption capacity at this pressure of a standard commercially available adsorbent, Zeolite 13X. 相似文献
17.
The adsorption of NO molecules on the perfect and defective (110) surfaces of SnO2 was studied with first-principles methods at the density-functional theory level. It was found that NO mainly interacts via
the nitrogen atom with the bridging oxygens of the stoichiometric surface while the coordinatively unsaturated surface Sn
atoms are less reactive. On the oxygen-deficient surface, NO is preferentially adsorbed at the vacancy positions, with the
nitrogen atom close to the former surface oxygen site. Regardless of the adsorption site, the unpaired electron is located
mainly on the NO molecule and only partly on surface Sn atoms. The results for the SnO2 surface are compared to literature results on the isostructural TiO2 rutile (110) surface.
Dedicated to Professor Karl Jug on the occasion of his 65th birthday 相似文献
18.
In this work, pore structure evolution of Ormosils containing TBT (Tetrabutyl titanate) has been characterized by means of mercury porosimetry, nitrogen adsorption and helium pycnometry. These ormosils have been prepared by the sol-gel method by the reaction of TEOS (tetraethoxysilane), PDMS (polydimethylsiloxane, silanol terminated) and TBT under acid-catalyzed conditions. The addition of TiO2 increases the volume and specific surface of secondary micropores and at the same time decreases the corresponding volumes of mesopores and macropores. The presence of TiO2 gives also a continuous decreasing in the pore connectivity being 9.7 for the ormosil without TiO2 and 4.4 for that of the higher concentration of TiO2. However, the pore length shows a significant decrease with the first addition of TiO2 changing from 9.1 to 2.2 at the higher TiO2 concentration. Pore volumes show a decrease as the TiO2 concentration is increased in the ormosil. On the other hand, density increases and porosity decreases with the TiO2 concentration. These results are in accordance with the presence of TiO2 nanoparticles in the ormosil and the size of such nanoparticles increases with the TiO2 concentration. Fractal constant has a low value, close to 2, for all different samples meaning that these ormosils can be considered as low surface roughness materials. 相似文献
19.
A. A. Pribylov S. Z. Muminov I. A. Kalinnikova L. G. Shekhovtsova O. K. Krasil’nikova 《Russian Chemical Bulletin》2013,62(10):2102-2108
Equilibrium adsorption of nitrogen, carbon dioxide, and argon was examined on the sodium and pyridinium forms of montmorillonite and on the hydrogen form of bentonite. The measurements were carried out at 303, 343, 373, and 400 K over pressure ranges of 0.1–90 MPa (Ar and N2) and 0.1–6 MPa (CO2). The amount of nitrogen vapor adsorbed was determined at 77 K and pressures from 0 to 0.1 MPa. The porous structure parameters of the studied samples were determined using adsorption isotherms of nitrogen, argon, and carbon dioxide vapors. At elevated temperatures and pressures >10 MPa, Ar and N2 adsorption processes on the Na-form of montmorillonite and Ar adsorption on bentonite are activated, since the amounts of the gases adsorbed and adsorption volumes increase with temperature. No activated adsorption is observed for carbon dioxide adsorption on these adsorbents. A comparison of the excess adsorption isotherms of gases on the Py-form of montmorillonite and H-form of bentonite shows that adsorption in micropores predominates for the Py-form of montmorillonite, whereas for the Na-form of bentonite and H-form of bentonite adsorption occurs mainly in meso- and macropores. 相似文献
20.
Characterization of rice husks and the products of its thermal degradation in air or nitrogen atmosphere 总被引:2,自引:0,他引:2
S. D. Genieva S. Ch. Turmanova A. S. Dimitrova L. T. Vlaev 《Journal of Thermal Analysis and Calorimetry》2008,93(2):387-396
Rice husk is a by-product of rice milling process and are a major waste product of the agricultural industry. They have now
become a great source as a raw biomass material for manufacturing value-added silicon composite products, including silicon
carbide, silicon nitride, silicon tetrachloride, pure silicon, zeolite, fillers of rubber and plastic composites, adsorbent
and support of catalysts. The bulk and true densities of raw rice husk with different moisture and sizes were determined.
The rice husk was subjected to pyrolysis in fluidized-bed reactor in air or nitrogen atmosphere.
The products obtained were characterized by thermogravimetric and X-ray powder analysis, IR-spectroscopy, scanning electron
microscopy and nitrogen adsorption at 77 K. The specific surface area of the products is comparable with this of γ-Al2O3. The kinetics of H2SeO3 adsorption out of aqueous solutions at 298 K was studied. The adsorption capacity of white rice husks ash was found to be
higher than that of black rice husk ash and the adsorption kinetics obeyed the second order kinetic equation. 相似文献