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1.
The simulation of the absorption of CO2 molecules by the (H2O)10 cluster is performed by the molecular dynamics method using the modified TIP4P model of water. The detailed structure of (CO2)i(H2O)10 clusters (0≤i≤11) is analyzed by the statistic geometry method based on the construction of the Voronoi polyhedra. The obtained distributions of the geometric elements of polyhedra indicate the significant changes in the structure of a cluster after the absorption of one CO2 molecule. Only polyhedra characterizing the structure of unstable water clusters that absorbed six or seven CO2 molecules demonstrate a nonsphericity close to the ideal tetrahedron. Linear CO2 molecule tends to be oriented in a cluster so that the average angle formed by this molecule and permanent dipole moments of water molecules would be equal to about 30°.__________Translated from Kolloidnyi Zhurnal, Vol. 67, No. 3, 2005, pp. 315–321.Original Russian Text Copyright © 2005 by Galashev, Rakhmanova, Chukanov. 相似文献
2.
Autocorrelation functions of translational and angular velocities of H2O and CO2 molecules in (CO2)i(H2O)10 clusters that are generated by the molecular dynamics method, as well as their frequency spectra, are calculated. Self-diffusion coefficients of molecules in clusters are determined. The IR spectra thus obtained and frequency-dependent dielectric permittivity of the clusters indicate the enhancement of absorption of Earth’ thermal radiation by these aggregates with an increase in the number of CO2 molecules in the aggregates. Dielectric losses also increase with the i number.__________Translated from Kolloidnyi Zhurnal, Vol. 67, No. 3, 2005, pp. 322–327.Original Russian Text Copyright © 2005 by Galashev, Rakhmanova, Chukanov. 相似文献
3.
Jhulimar M. Celedonio Jong Hyun Park Young Soo Ko 《Research on Chemical Intermediates》2016,42(1):141-154
The stability of amine-functionalized silica sorbents prepared through the incipient wetness technique with primary, secondary, and tertiary amino organosilanes was investigated. The prepared sorbents were exposed to different gaseous streams including CO2/N2, dry CO2/air with varying concentration, and humid CO2/air mixtures to demonstrate the effect of the gas conditions on the CO2 adsorption capacity and the stability of the different amine structures. The primary and secondary amine-functionalized adsorbents exhibited CO2 sorption capacity, while tertiary amine adsorbent hardly adsorbed any CO2. The secondary amine adsorbent showed better stability than the primary amine sorbent in all the gas conditions, especially dry conditions. Deactivation species were evaluated using FT-IR spectra, and the presence of urea was confirmed to be the main deactivation product of the primary amine adsorbent under dry condition. Furthermore, it was found that the CO2 concentration can affect the CO2 sorption capacity as well as the extent of degradation of sorbents. 相似文献
4.
V. A. Neves M. V. Costa J. D. Senra L. C. S. Aguiar L. F. B. Malta 《Journal of Thermal Analysis and Calorimetry》2017,130(2):689-694
Cu/Al layered double hydroxide (LDH) can be used as a catalyst for important processes such as cross-coupling reactions. This property may be improved by adding palladium by either impregnation or intercalation. Therefore, the LDH matrix and its composites with Pd0 or [PdCl4]2? have been prepared. By powder X-ray diffraction, FT-infrared spectroscopy, thermogravimetric and elemental analysis it was determined the LDH formula Cu4Al2(OH)12CO3.4H2O, with malachite as the second phase. The LDH thermal decomposition occurs between 120 and 600 °C, having as intermediates the double oxi-hydroxide and the mixed oxide phases. At 800 °C the residue is composed of CuO and CuAl2O4. The composites were obtained employing [PdCl4]2? and Pd2(dba)3 as precursors, and the solvent choice for this process was shown to be of significant importance: the materials obtained using DMF had Pd impregnated in the surface, while the usage of water promoted the intercalation of [PdCl4]2? in the LDH matrix. The thermogravimetric analysis was able to distinguish the mode of supporting palladium between the composites being a reliable characterization for such task. 相似文献
5.
Andres Trikkel Merli Keelmann Tiit Kaljuvee Rein Kuusik 《Journal of Thermal Analysis and Calorimetry》2010,99(3):763-769
In the present research, CO2 and SO2 binding ability of different oil shale ashes and the effect of pre-treatment (grinding, preceding calcination) of these ashes
on their binding properties and kinetics was studied using thermogravimetric, SEM, X-ray, and energy dispersive X-ray analysis
methods. It was shown that at 700 °C, 0.03–0.28 mmol of CO2 or 0.16–0.47 mmol of SO2 was bound by 100 mg of ash in 30 min. Pre-treatment conditions influenced remarkably binding parameters. Grinding decreased
CO2 binding capacities, but enhanced SO2 binding in the case of fluidized bed ashes. Grinding of pulverized firing ashes increased binding parameters with both gases.
Calcination at higher temperatures decreased binding parameters of both types of ashes with both gases studied. Clarification
of this phenomenon was given. Kinetic analysis of the binding process was carried out, mechanism of the reactions and respective
kinetic constants were determined. It was shown that the binding process with both gases was controlled by diffusion. Activation
energies in the temperature interval of 500–700 °C for CO2 binding with circulating fluidized bed combustion ashes were in the range of 48–82 kJ mol−1, for SO2 binding 43–107 kJ mol−1. The effect of pre-treatment on the kinetic parameters was estimated. 相似文献
6.
Alberto Santos Mohamed Ajbary Abdelhak Kherbeche Manuel Piñero N. De la Rosa-Fox Luis Esquivias 《Journal of Sol-Gel Science and Technology》2008,45(3):291-297
The increasingly evident impact of anthropogenic CO2 emissions on climate change and associated environmental effects is stimulating the search for viable methods to remove this
gas. One of the most promising strategies is the long-term storage of CO2 in inert, insoluble and thermodynamically-stable materials. This strategy mimics the natural reactions that transform silicates
into carbonates regulating the cycle of CO2 on the surface of the Earth, operating on a geological time-scale. Consequently, the aim is to accelerate these reactions
to be applicable on the timescale of human lives. We present the various technologies developed or proposed to date, based
on this particular approach. The principal limiting factor is that high pressures and temperatures are required to produce
appropriate materials capable of CO2 sequestration and storage. Nevertheless, the synthetic materials known as aerogels can be modified in shape, size and chemical
functionality so as to catalyse the process of CO2 elimination through silicates (of Ca or Mg), considerably reducing the reaction time and working at atmospheric pressure
and temperature. 相似文献
7.
8.
Processes proceeding during the mechanochemical activation of alkali metal metasilicates M2SiO3 (where M is Li, Na, K) are studied in the air and in an atmosphere of carbon dioxide. At the initial stage of activation in a centrifugal planetary mill in an atmosphere of carbon dioxide, the main portion of supplied mechanical energy is expended for grinding and the mechanosorption of CO2 occurs in the regime of cleavage, i.e., on the freshly formed surfaces of particles. As the time of activation increases, the specific surface area becomes constant, which, however, does not substantially affect the rate of interaction between carbon dioxide and silicates. The absorption of CO2 occurs in the regime of friction on the active sites of already formed surfaces and is accompanied by the tribodiffusion of gas molecules into structurally disordered layers of particles. With identical amounts of supplied energy, the CO2/M2SiO3 molar ratio in the samples activated in the medium of carbon dioxide increases in the Li < Na < K series. The main product of mechanically induced interactions between Li2SiO3 and CO2 is the X-ray amorphous carbonate-silicate phase. In the case of sodium and potassium metasilicates, the reaction of mechanochemical substitution occurs to form corresponding carbonates, hydrocarbonates, and amorphous silica. It is shown that the character of mechanochemical interaction between M2SiO3 and CO2 depends on the change in the Gibbs energy of the transformation of silicate into corresponding carbonate, as well as on the melting temperature and the hygroscopicity of silicate. 相似文献
9.
As a base-promoted Kolbe–Schmitt carboxylation reaction, the mechanism of synthesis of salicylic acid derivatives from phenols with CO2 in the industry is still unclear, even up to now. In this paper, synthesis of 3,6-dichloro salicylic acid (3,6-DCSA) from 2,5-dichloro phenoxide and CO2 was investigated in the presence of K2CO3. We show the reaction can proceed by itself, but it goes at a slower rate as well as a lower yield, compared to the case with the addition of K2CO3. However, the yield of 3,6-DCSA is only minorly affected by the size of K2CO3, which cannot be explained from the view of catalytic effect. Therefore, K2CO3 may on one hand act as a catalyst for the activation of CO2 so that the reaction can be accelerated, while on the other hand, it also acts as a co-reactant in deprotonating the phenol formed by the side reaction to phenoxide, which is further converted to salicylate. 相似文献
10.
At present, carbon dioxide is considered the largest contributor among greenhouse gases. This review covers the current state
of problem of carbon dioxide emissions from industrial and combustion processes, the principle of photocatalysis, existing
literature related to photocatalytic CO2 reduction over TiO2 based catalysts and the effects of important parameters on the process performance including light wavelength and intensity,
type of reductant, metal-modified surface, temperature and pressure.
Presented at the 34th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 21–25 May
2007. 相似文献
11.
Yu. V. Kokunov Yu. E. Gorbunova V. V. Kovalev 《Russian Journal of Inorganic Chemistry》2008,53(12):1885-1892
Coordination polymers [AgCF3CO2(2,3-Et2Pyz)](I)(2,3-Et2Pyz-C8H12N2) and [AgCF3CO2(Bpeta)] (II) (Bpeta is 4′4-bipyridylethane, C12H12N2) are synthesized. Their structures are determined. The crystals of compound I are monoclinic, space group P2(1)/n, a = 7.185(1), b = 14.754(1), c = 12.317(1)Å, β = 97.09(1)°, V = 1295.7(2) Å3, ρcalcd = 1.831 g/cm3, Z = 4. Structure I consists of infinite chains of doubled polymeric chains joined by silver carboxylate dimers [[Ag2(CF3CO2)2(Et2Pyz)2]∞. The coordination polyhedron of Ag+ is a distorted tetrahedron. The crystals of compound II are orthorhombic, space group Pbca, a = 13.555(3), b = 13.991(3), c = 16.449(3) Å, V = 3119.5(11) Å3, ρcalcd = 1.725 g/cm3, Z = 8. Doubled polymeric chains with the Ag…Ag bond (3.16 Å) are also formed in structure II. Supramolecular layers are formed in the structure due to the weak π-π-stacking interaction between the aromatic groups of chains. The CF3CO 2 ? anion is weakly bound to Ag+ (Ag-Oavg 2.790 Å). 相似文献
12.
Zh. A. Kochkarov M. V. Khubaeva Z. L. Khakulov 《Russian Journal of Inorganic Chemistry》2011,56(5):783-786
This is the first study of the NaBO2-Na2CO3-Na2MoO4-Na2WO4 quaternary system by differential thermal analysis. Na2[MoO4(x)WO4(1 − x)] solid solutions in the quaternary system are found to not decompose. 相似文献
13.
Adsorption of CO2, N2, CH4 and H2 on triamine-grafted pore-expanded MCM-41 mesoporous silica (TRI-PE-MCM-41) was investigated at room temperature in a wide
range of pressure (up to 25 bar) using gravimetric measurements. The material was found to exhibit high affinity toward CO2 in comparison to the other species over the whole range of pressure. Column-breakthrough dynamic measurements of CO2-containing mixtures showed very high selectivity toward CO2 over N2, CH4 and H2 at CO2 concentrations within the range of 5 to 50%. These conditions are suitable for effective removal of CO2 at room temperature from syngas, flue gas and biogas using temperature swing (TS) or temperature-pressure swing (TPS) regeneration
mode. Moreover, TRI-PE-MCM-41 was found to be highly stable over hundreds of adsorption-desorption cycles using TPS as regeneration
mode. 相似文献
14.
Jens Soentgen 《Foundations of Chemistry》2010,12(2):137-148
I will trace the little known prehistory and parts of the better known history of CO2 by investigating some of the names it has been given from Antiquity to the present day. In Antiquity, the words pneuma or
spiritus letalis designated both a supernatural force and an exhalation that emanated from certain caves. We will see how
CO2 gradually came to be regarded as something natural, a gas and then substance. 相似文献
15.
The grand canonical ensemble Monte Carlo method has been used to study adsorption of carbon dioxide, methane, and their mixtures with different compositions in slitlike carbon pores at a temperature of 318 K and pressures below 60 atm. The data obtained have been used to show the effect of fixed amounts of pre-adsorbed water (19, 37, and 70 vol %) on the adsorption capacity and selectivity of carbon micro- and mesopores. The presence of water reduces the adsorption capacity throughout the studied pressure range upon adsorption of gaseous mixtures containing less than 50% CO2, as well as in narrow micropores (with widths of 8?12 Å). Upon adsorption of mixtures with CO2 contents higher than 50%, the adsorption capacity of pores with low water contents appears, in some region of the isotherm, to be higher than that in dry pores. In the case of wide pores (16 and 20 Å), this region is located at low and moderate pressures, while for mesopores it is located at high pressures. The analysis of the calculated data has shown that the molecular mechanism of the influence of preadsorbed water on the adsorption capacity is based on the competition between the volume accessible for adsorption (decreases the capacity) and the strength of the interaction between carbon dioxide molecules and water molecules (increases the capacity). Therewith, the larger the surface area of the water–gas contact, the stronger the H2O–CO2 interactions. 相似文献
16.
Ying Tang Feiqin Chang Rui Zhou Bo Shen Qitong Cheng 《Russian Journal of Applied Chemistry》2016,89(12):2066-2071
Biodiesel containing almost no glycerol has been produced by coupling reaction carried out over K2CO3 supported by calcium oxide as solid base catalysts. The solid base catalysts synthesized by wet impregnation exhibit an exceedingly high activity in biodiesel production. It was found that the reaction time required for the highest yield of biodiesel, 99.2%, can be shortened to 30 min over K2CO3/Al2O3 under the optimum reaction conditions: 8: 1: 1 molar ratio of methanol/DMC/oil, 30 wt % K2CO3/Al2O3 catalyst, and 65°C reaction temperature. Solid basic catalysts examined in the study were characterized by BET surface area, XRD, CO2-TPD, and SEM techniques. The strong interaction between K2CO3 and the support yields a new basic active site, which can be probably responsible for the high activity of K2CO3/Al2O3. 相似文献
17.
A.V. Vasil'ev A.P. Rudenko S.A. Aristov G.K. Fukin 《Russian Journal of Organic Chemistry》2005,41(8):1169-1174
Oxidation of unsymmetrically sunstituted 1,3-diarylpropynones in a system trifluoroacetic acid-dichloromethane-lead(IV) oxide proceeds through intermediate formation of cation radicals and occurs regio- and stereoselectively affording E-1,1,2,2-tetraaroylethenes. The highest yield of these compounds was obtained from 1,3-diarylpropynones containing electron-donor methoxy and methyl groups in the aromatic ring conjugated with the triple bond. 相似文献
18.
19.
Tomasz Chmielniak Marek Sciazko Grzegorz Tomaszewicz Martyna Tomaszewicz 《Journal of Thermal Analysis and Calorimetry》2014,117(3):1479-1488
Carbon dioxide was considered as a co-gasifying agent in a coal gasification reactor. The work presented herein describes the simulation results for the process and the experimental data on coal char gasification with CO2 addition as the rate-controlling step for the entire process. To study the potentially beneficial effect of the introduction of CO2 into the gasification system, several simulations were conducted using the commercial process simulation software ChemCAD 6.3®. The results of a Gibbs equilibrium reactor were evaluated. The Boudouard reaction is a critical path for the development of this process, and the kinetics were studied experimentally. Four chars derived from the pyrolysis of Polish coals of different origins were selected for the experiments. The kinetic characteristics of this system were examined using a custom-designed pressurized fixed-bed reactor. To determine the effect of pressure on the gasification rate, several preliminary studies on the gasification of coal chars were performed isothermally at the temperature of 950 °C and pressures of 1, 10, and 20 bars. In contrast to the thermodynamic calculations, the experimental data revealed that increasing the CO2 pressure leads to a higher reaction rate for medium-rank coal chars and low-rank lignite coal char, resulting in higher efficiency for carbon monoxide production. The pressure influences the reactivity more strongly when varied from 1 to 10 bars; a further increase in pressure affects the rate almost insignificantly. The observed behavior representing the changes in carbon conversion degree during gasification is satisfactorily described by the grain model. 相似文献
20.
P. Yu. Savechenkov A. V. Vasil’ev A. P. Rudenko 《Russian Journal of Organic Chemistry》2004,40(9):1279-1283
Regio- and stereoselective oxidative dimerization of alkyl 3-arylpropynoates in the system CF3CO2H-CH2Cl2-PbO2 (1–30 h, 0–20°C) leads to dialkyl (E)-2,3-bis(arylcarbonyl)-2-butene-1,4-dioates with trans arrangement of the substituents at the double bond.Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 9, 2004, pp. 1329–1333.Original Russian Text Copyright © 2004 by Savechenkov, Vasilev, Rudenko.For communication XI, see [1]. 相似文献