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1.
The results of several MC SCF calculations on CH 4, C 2H 4 and C 2H 6 with minimun bases of Slater type AO's are reported. The computing method is a quadratically convergent process. Better final energies are obtained if localized MO's are used. 相似文献
2.
An experimental study on the conversion of NO in the NO/N 2, NO/O 2/N 2, NO/C 2H 4/N 2 and NO/C 2H 4/O 2/N 2 systems has been carried out using dielectric barrier discharge (DBD) plasmas at atmospheric pressure. In the NO/N 2 system, NO decomposition to N 2 and O 2 is the dominating reaction; NO conversion to NO 2 is less significant. O 2 produced from NO decomposition was detected by an on-line mass spectrometer. With the increase of NO initial concentration, the concentration of O 2 produced decreases at 298 K, but slightly increases at 523 K. In the NO/O 2/N 2 system, NO is mainly oxidized to NO 2, but NO conversion becomes very low at 523 K and over 1.6% of O 2. In the NO/C 2H 4/N 2 system, NO is reduced to N 2 with about the same NO conversion as that in the NO/N 2 system but without NO 2 formation. In the NO/C 2H 4/O 2/N 2 system, the oxidation of NO to NO 2 is dramatically promoted. At 523 K, with the increase of the energy density, NO conversion increases rapidly first, and then almost stabilizes at 93–91% of NO conversion with 61–55% of NO 2 selectivity in the energy density range of 317–550 J L −1. It finally decreases gradually at high energy density. A negligible amount of N 2O is formed in the above four systems. Of the four systems studied, NO conversion and NO 2 selectivity of the NO/C 2H 4/O 2/N 2 system are the highest, and NO/O 2/C 2H 4/N 2 system has the lowest electrical energy consumption per NO molecule converted. 相似文献
3.
The high-pressure limiting rate constants of the reactions between H or D atoms and three isotopic ethylenes have been measured in the temperature range 206–461 K. Practically no isotope effects due to the differences between the ethylenes could be observed. This result does not agree with the prediction recently made by the activated complex theory. 相似文献
4.
High pressure vapour-liquid equilibrium data for the C 2H 6 + N 2, C 2H 4 + N 2, C 3H 8 + N 2, and C 3H 6 + N 2 systems are presented. The data are obtained isothermally in the range from 200 K to 290 K. For each point of data, temperature, pressure and liquid and vapour phase mole fractions are measured.Values for the vapour phase mole fractions are calculated from the obtained pressure, temperature and liquid phase mole fractions. The calculated values are compared with the experimental results, and it is found that the average mean deviation between calculated and experimental mole fractions is less than 0.009 for the systems considered in this work. 相似文献
5.
We report the surface-enhanced Raman spectra of ethylene and acetylene adsorbed on colloidal silver particles formed by gas aggregation and isolated at low temperatures in solid adsorbate/argon matrices. The spectra of both molecules exhibit modes which are normally Raman-forbidden. Excitation with several visible laser frequencies indicated that the degree of enhancement increased towards the blue. 相似文献
6.
The adsorption of C 2H 4 on W(100) has been studied by ultraviolet photoelectron spectroscopy with hν = 21.22 eV. The spectrum measured after in initial saturation exposure at 80 K exhibits structure which correlates well with energy levels recently calculated by Demuth and Eastman (DE) for sp 3 rehybridized C 2H 4. Dehydrogenation of the adsorbate, either by subsequent heating to 295 K or direct adsorption at 295 K, yields a spectrum which correlates with DE's calculation for sp 2 rehybridized C 2H 2. These results suggest that C 2H 4 and C 2H 2 may be distorted from their planar and linear structures respectively and that the CC bonds on these molecules are stretched by adsorption on W(100). Qualitative arguments suggest that the bonding site for both melecules is directly over a W atom and that the Dewar—Chatt model for πd bonding in organometallic compounds is applicable. 相似文献
7.
Ohne Zusammenfassung 相似文献
8.
Experimental differential cross sections for 40 keV electrons scattered by C 2H 2, C 2H 4 and C 2H 6 molecules were measured using the gas electron diffraction method in the range of the scattering variable s from s = 1 A ?1 to s = 30 A ?1. The differential cross sections for neon were also measured and compared with calculated differential cross sections to calibrate the diffractograph. Experimental differential cross sections show significant deviations with respect to theoretical differential cross sections calculated from the Debye-Ehrenfest model, mainly in the range of small scattering angles. The observed differences are connected to chemical binding effects. From the experimental data, an estimation of the binding energy was carried out. The deduced values: ?0.58 ± 0.20 au for C 2H 2, ?0.94 ± 0.30 au for C 2H 4 and ?1.23 ± 0.40 au for C 2H 6 are in agreement with those obtained by thermochemical methods. 相似文献
9.
Ce-Al2O3 catalysts prepared by co-precipitation are investigated both in NO oxidation by O2 and in selective catalytic reduction of NO by C2H2(C 2 H 2-SCR).It is found that C2H2-SCR is initiated and controlled by NO oxidation to NO 2 over Al2O3.Ce loading on Al2O3 is almost inactive for NO oxidation below 350 C,since NO2 strongly adsorbs on cerium oxide,leading to the active sites being blocked,which was characterized by temperature-programmed desorption of NO and NO 2 and Fourier transform infrared spectroscopy after NO+O 2 coadsorption over the samples.However,in the case of C2H2-SCR,Ce loading on Al 2 O 3 significantly improves the reaction by accelerating the NO oxidation step in the temperature range of 250-450 C,since the nitrate species produced by NO 2 adsorption is an active intermediate required by C2H 2-SCR. 相似文献
10.
C 2(a 3π u) disappearance rate constants of 1.44, 0.96, 0.0296, 0.0130 and < 10 ?6(x10 ?10cm 3s ?1) are reported for reactions with C 2H 4, C 2H 2, O 2, C 2H 6, and CH 4, respectively at 298 K. C 2(a 3π u) fragments are generated by multiphoton ArF excimer laser photodissociation at C 2H 2, and monitored by dye laser induced fluorescence. Arguments are presented which favor chemical reactions over the C 2(a 3π u) → (X 1σ +g) quenching channel. C 2 + C 2H 2 represents the one possible exception to the reactive channel. 相似文献
11.
Calculations with an extended polarized basis set and Møller-Plesset perturbation theory including triple substitution correlation corrections in the fourth-order treatment indicate that singlet ethylidene (CH 3CH:) is not a local minimum on the C 2H 4 potential energy surface. Rearrangement to ethylene occurs without actuation. Barriers for hydrogen scrambling and for 1,1-hydrogen elimination are estimated. 相似文献
12.
LnCl 3 (Ln=Nd, Gd) reacts with C 5H 9C 5H 4Na (or K 2C 8H 8) in THF (C 5H 9C 5H 4 = cyclopentylcyclopentadienyl) in the ratio of 1 : to give (C 5H 9C 5H 4)LnCl 2(THF) n (orC 8H 8)LnCl 2(THF) n], which further reacts with K 2C 8H 8 (or C 5H 9C 5H 4Na) in THF to form the litle complexes. If Ln=Nd the complex (C 8H 8)Nd(C 5H 9C 5H 4)(THF) 2 (a) was obtained: when Ln=Gd the 1 : 1 complex [(C 8H 8)Gd(C %H 9)(THF)][(C 8H 8)Gd(C 5H 9H 4)(THF) 2] (b) was obtained in crystalline form. The crystal structure analysis shows that in (C8H8)Ln(C5H9C5H4)(THF)2 (Ln=Nd or Gd), the Cyclopentylcyclopentadieny (η5), cyclooctatetraenyl (η8) and two oxygen atoms from THF are coordinated to Nd3+ (or Gd3+) with coordination number 10. The centroid of the cyclopentadienyl ring (Cp′) in C5H9C5H4 group, cyclooctatetraenyl centroid (COTL) and two oxygens (THF) form a twisted tetrahedron around Nd3+ (or Gd3+). In (C8H8)Gd(C5H9C5H4)(THF), the cyclopentyl-cyclopentadienyl (η5), cyclooctatetraenyl (η8) and one oxygen atom are coordinated to Gd3+ with the coordination number of 9 and Cp′, COT and oxygen atom form a triangular plane around Gd3+, which is almost in the plane (dev. -0.0144 Å). 相似文献
13.
Zur Trennung von H2, O2, N2, NO, CO, N2O, CO2, C2H6, C2H4, C2H2, NO2(N2O4) und Feuchtigkeit
Ohne Zusammenfassung 相似文献
14.
Potential energy surfaces of the reaction of SiH 2 and C 2H 2 (and C 2D 2) have been calculated by means of ab initio molecular orbital theory at the QCISD/6-311G++(2df, 2p)//MP2/6-31G(d, p) level with corrections for the triple excitations to the QCISD energies. The barrier heights for the two reaction channels of the adduct, thus calculated, were further utilized for the dynamical calculation of the rate constants in the framework of quantum statistical Rice-Ramsperger-Kassel theory. Contributions of the rate constants of the various pathways to the total rate constant ( KT) for the disappearance of the reactants are critically examined and compared with experiment. The pressure dependence of KT(C 2H 2) is primarily due to the formation of silirene. KT(C 2D 2) is consistently higher than KT(C 2H 2). The standard heat of formation of silirene is predicted to be 72.1 ± 3 kcal/mol. Rearrangement of silirene to vinylsilylene requires an activation energy smaller than that to silylacetylene. 相似文献
15.
We report a new synthesis and characterization of Ir(C 2H 4) 2(C 5H 7O 2) [(acetylacetonato)-bis(η 2-ethene)iridium(I)], prepared from (NH 4) 3IrCl 6 · H 2O in a yield of about 45%. The compound has been characterized by X-ray diffraction crystallography, infrared, Raman, and NMR spectroscopies and calculations at the level of density functional theory. Ir(C 2H 4) 2(C 5H 7O 2) is isostructural with Rh(C 2H 4) 2(C 5H 7O 2), but there is a substantial difference in the ethylene binding energies, with Ir-ethylene having a stronger interaction than Rh-ethylene; two ethylenes are bound to Ir with a binding energy of 94 kcal/mol and to Rh with a binding energy of 70 kcal/mol. 相似文献
16.
In this work, we studied the catalytic activity of LaMnO 3 and (La 0.8A 0.2)MnO 3 (A = Sr, K) perovskite catalysts for oxidation of NO and C 10H 22 and selective reduction of NO by C 10H 22. The catalytic performances of these perovskites were compared with that of a 2 wt% Pt/SiO 2 catalyst. The La site substitution increased the catalytic properties for NO or C 10H 22 oxidation compared with the non-substituted LaMnO 3 sample. For the most efficient perovskite catalyst, (La 0.8Sr 0.2)MnO 3, the results showed the presence of two temperature domains for NO adsorption: (1) a domain corresponding to weakly adsorbed NO, desorbing at temperatures lower than 270 ℃ and (2) a second domain corresponding to NO adsorbed on the surface as nitrate species, desorbing at temperatures higher than 330 ℃. For the Sr-substituted perovskite, the maximum NO 2 yield of 80% was observed in the intermediate temperature domain (around 285 ℃). In the reactant mixture of NO/C 10H 22/O 2/H 2O/He, (La 0.8Sr 0.2)MnO 3 perovskite showed better performance than the 2 wt% Pt/SiO 2 catalyst: NO 2 yields reaching 50% and 36% at 290 and 370 ℃, respectively. This activity improvement was found to be because of atomic scale interactions between the A and B active sites, Sr 2+ cation and Mn 4+/Mn 3+ redox couple. Thus, (La 0.8Sr 0.2)MnO 3 perovskite could be an alternative free noble metal catalyst for exhaust gas after treatment. 相似文献
17.
High-resolution infrared studies of isotopic ethylenes below 2000 cm ?1 have been commenced with a Nicolet FTIR spectrometer. Accurate vibration and rotation parameters for the v12 fundamentals of C 2H 4 and C 2D 4 are determined from spectra recorded with 0.05 cm ?1 resolution. Excellent band contour simulations confirm that these bands are unperturbed throughout their range. 相似文献
18.
C 4H 4+ reacts with pyridine (C 5H 5N) via the channels of proton transfer, charge transfer and condensation with H-elimination. The condensation reaction is of general interest in terms of basic chemistry and is the focus of the present study. By means of theoretical calculations and Fourier transform mass spectrometer experiments using deuterated pyridine and substituted pyridines, the structure of the product ion and the reaction pathways are investigated. From the experimental results we find that the H atom that is eliminated can originate from either pyridine or C 4H 4+. The experiments show that elimination of an H atom from C 4H 4+ is preferred and that there is an observable kinetic isotope effect. By replacing H atoms with methyl groups in ortho positions of pyridine, the experimental results also suggest possible steric blocking to the condensation. Based on the experimental observations and results of theoretical calculations of several possible structures of intermediates, transition states, and final product ions, a possible reaction scheme for the condensation-H-elimination is discussed. 相似文献
19.
When the products of the reaction between F atoms produced in a microwave discharge and C 2H 4 are frozen in a large excess of argon at 14 K, new infrared absorptions appear which can be assigned to the 2-fluoroethyl radical. Studies of the dependence of the product distribution on the F-atom concentration have confirmed that the stabilization of C 2H 4F 2 plays only a minor role under the sampling conditions typical of these experiments. Isotopic substitution experiments have demonstrated that the steric configuration about the CH bond is randomized as a result of the F-atom reaction. Upon irradiation of the sample with the full light of a medium-pressure mercury arc, absorptions of vinyl fluoride and acetylene and of the acetylene—HF complex grow in intensity, while those of FCD 2CH 2 and of FCH 2CD 2 diminish in intensity and those of FCH 2CH 2 a nd of FCH 2CD 2 are unchanged. The F-atom reactions and photolysis processes which occur in these experiments are discussed, and a tunnelling mechanism is proposed to explain the isotopic selectivity in the 2-fluoroethyl photodecomposition. The vibrational spectrum of FCH 2CH 2 is compared with that derived in a recent ab initio calculation. 相似文献
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