时间分辨红外发射光谱研究C2H3+NO反应体系

The elementary reaction of C2H3＋ NO has been reported for the first time in this paper.C2H3 radical was produced by laser photolysis of vinyl bromide at 248 nm. Vibrationally excited reaction products H2CO,NCO and HCN were observed. Two exothermic reaction channels leading to HCN＋ H2CO and CH3＋ NCO are identified.     

NO reduction with C3H8 on Co/Al2O3 catalyst. effect of O2 concentration

The selective catalytic reduction (SCR) of NO by propane in excess oxygen-containing gas mixture was studied on Co/Al₂O₃ catalyst. The oxygen concentration is very important for the reaction. The NO conversion to N₂ without oxygen is 3% at 800 K and when the O₂ concentration is raised up to 8% the NO conversion reaches its maximum value of 60% at 800 K. Characterization results by TPR and UV-Vis spectroscopy show that in the catalyst, species strongly interacting with tetrahedral and octahedral Co²⁺ ions in the support are present. This revised version was published online in June 2006 with corrections to the Cover Date.     

A Gaussian-2 ab initio study of [C2H5S] ions: III. H2 and CH4 eliminations from CH3CHSH and CH3SCH2

Gaussian-2 ab initio calculations were performed to examine the six modes of unimolecular dissociation of cis-CH₃CHSH⁺ (1⁺), trans-CH₃CHSH⁺ (2⁺), and CH₃SCH₂⁺ (3⁺): 1⁺→CH₃⁺+trans-HCSH (1); 1⁺→CH₃+trans-HCSH⁺ (2); 1⁺→CH₄+HCS⁺ (3); 1⁺→H₂+c-CH₂CHS⁺ (4); 2⁺→H₂+CH₃CS⁺ (5); and 3⁺→H₂+c-CH₂CHS⁺ (6). Reactions (1) and (2) have endothermicities of 584 and 496 kJ mol⁻¹, respectively. Loss of CH₄ from 1⁺ (reaction (3)) proceeds through proton transfer from the S atom to the methyl group, followed by cleavage of the C–C bond. The reaction pathway has an energy barrier of 292 kJ mol⁻¹ and a transition state with a wide spectrum of nonclassical structures. Reaction (4) has a critical energy of 296 kJ mol⁻¹ and it also proceeds through the same proton transfer step as reaction (3), followed by elimination of H_2. Formation of CH₃CS⁺ from 2⁺ (reaction (5)) by loss of H₂ proceeds through protonation of the methine (CH) group, followed by dissociation of the H₂ moiety. Its energy barrier is 276 kJ mol⁻¹. On both the MP2/6-31G* and QCISD/6-31G* potential-energy surfaces, the H₂ 1,1-elimination from 3⁺ (reaction (6)) proceeds via a nonclassical intermediate resembling c-CH₃SCH₂⁺ and has a critical energy of 269 kJ mol⁻¹.     

丙烷在Ce-Fe/Al2O3/cordierite上选择性催化还原NO

利用凝胶溶胶法和浸渍法制备了Ce-Fe/Al₂O₃/cordierite催化剂,实验研究了其催化丙烷选择性还原NO的特性。结果表明,当铈的负载量从1%增加至5%时,Ce-Fe/Al₂O₃/cordierite的C₃H₈-SCR性能先增强后减弱,3.5Ce-Fe/Al₂O₃/cordierite具有最佳的脱硝性能,在有氧条件下,600℃时可实现96.5%的脱硝效率。Ce的加入能够提升Fe/Al₂O₃/cordierite催化剂的抗硫性能。烟气中通入0.02%的SO₂后,3.5Ce-Fe/Al₂O₃/cordierite催化丙烷还原NO的转化率始终维持在93%,而没有经过Ce修饰的Fe/Al₂O₃/cordierite的NO转化率从88%下降为80%左右。利用XRD、N₂吸附-脱附、SEM、H₂-TPR、吡啶吸附红外光谱等手段研究了催化剂的物理化学性质。结果表明,加入助剂铈能与Fe形成了固溶体,增加催化剂表面Lewis酸浓度和氧化还原能力,从而提高了催化丙烷还原NO的性能。过多的铈引入会减少Fe₂O₃结晶体的形成,不利于在C₃H₈-SCR反应中形成NO₂/NO₃^-物种,从而导致NO还原效率下降。     

Reaction of C2HCl2＋O2： Combined TR-FTIR Spectroscopy and Electronic Structure

The product channels and mechanisms of the C2HC12＋O2 reaction are investigated by step-scan time-resolved Fourier transform infrared emission spectroscopy and the G3MP2// B3LYP/6-311G（d,p） level of electronic structure calculations. Vibrationally excited products of HCI, CO, and CO2 are observed in the IR emission spectra and the product vibrational state distribution are determined which shows that HCI and CO are vibrationally excited with the nascent average vibrational energy estimated to be 59.8 and 51.8 kJ/mol respectively. In combination with the G3MP2//B3LYP/6-311G（d,p） calculations, the reaction mechanisms have been characterized and the energetically favorable reaction pathways have been suggested.     

Co/Fe/Al2O3/cordierite催化C3H6选择性还原NO的实验研究

采用溶胶凝胶法和浸渍法制备了负载于蜂窝陶瓷上的Co/Fe/Al₂O₃/cordierite催化剂,在陶瓷管流动反应器上对其催化C₃H₆选择性还原NO的性能进行了测试。结果表明,该催化剂表现出最优脱硝性能,在模拟烟气条件下,当反应温度为550 ℃时可实现97%的脱硝效率。Co的引入可显著增强Fe/Al₂O₃/cordierite催化剂抗SO₂和H₂O的能力。在模拟烟气中同时引入0.02% SO₂和3% H₂O后,1.5Co/Fe/Al₂O₃/cordierite的脱硝性能受影响甚微,当反应温度高于500 ℃时1.5Co/Fe/Al₂O₃/cordierite催化C₃H₆还原NO的效率均可达到90%以上;相比之下,未经Co修饰的催化剂Fe/Al₂O₃/cordierite脱硝性能受到了严重的抑制,在整个反应温度区间（200-700 ℃）内,其催化C₃H₆还原NO的效率最高不足50%。XRD和SEM表征结果表明,经过适量的Co修饰后的1.5Co/Fe/Al₂O₃/cordierite表面变得更疏松,且形成了以钴铁和钴铝双金属氧化物为主要成分的球状晶粒。H₂-TPR结果表明,相比于Fe/Al₂O₃/cordierite,1.5Co/Fe/Al₂O₃/cordierite有更好的低温还原性能。Py-FTIR结果表明,Co的引入可使催化剂表面的Lewis酸明显增加,且生成了Brønsted酸。N₂吸附-脱附表征结果表明,Co可增大催化剂的比表面积。     

Ni_(x)Cu_(y)-B_(24)N_(28)催化CO_(2)氧化C_(3)H_(8)速控步骤的反应机理研究北大核心CSCD

采用密度泛函理论(DFT)研究了C_(3)H_(8)和CO_(2)在Ni_(x)Cu_(y)-B_(24)N_(28)(x+y=4,x=1、2、3、4)表面吸附及速控步骤反应机理.计算了C_(3)H_(8)、CO_(2)和相应中间体在Ni_(x)Cu_(y)-B_(24)N_(28)表面的吸附能以及6条可能路径下的反应热和活化能.计算结果表明,C_(3)H_(8)和CO_(2)在Ni_(x)Cu_(y)-B_(24)N_(28)表面是物理吸附,C_(3)H_(8)+CO_(2)→CH_(3)CHCH_(3)+OCOH是最有利的路径,其在不同催化剂表面的活化能顺序是NiCu_(3)-B_(24)N_(28)(1.42 eV)、Ni_(2)Cu_(2)-B_(24)N_(28)(1.57 eV)、Ni_(3)Cu-B_(24)N_(28)(1.62 eV)、Ni_(4)-B_(24)N_(28)(1.75 eV).由此可知,在Ni_(x)Cu_(y)-B_(24)N_(28)催化CO_(2)氧化C_(3)H_(8)的体系中,Cu含量直接影响其催化活性,即NiCu_(3)-B_(24)N_(28)用于催化CO_(2)氧化C_(3)H_(8)有一定优势.     

Exploring the lowest energy triplet potential energy surface for cyclic C4H4 isomers with the complete basis set ab initio method. Is the transformation of triafulvene into cyclobutadiene possible in their excited states?

High level computational studies were performed with the aim being to explore the possibility of converting the experimentally available triafulvene into the hard-to-detect cyclobutadiene. The method is based on the simple approach used to excite triafulvene into the triplet state, and then through various reaction channels, come to the aromatic triplet cyclobutadiene. Triplet cyclobutadiene is only a few kcal/mol higher in energy than singlet cyclobutadiene and should be easily relaxed into the latter. Several reaction pathways that include only a concerted mechanism, as well as reaction pathways that include the radical formation–recombination were also explored. Some possible approaches for experimentally obtaining the singlet or triplet cyclobutadiene were suggested.     

The role of surface species on the SCR of NO by C3H6 under lean-burn conditions over platinum catalyst

The nature of the surface species on Pt/Al₂O₃ for the SCR of NO by C₃H₆ under excess oxygen has been investigated. An experiment consisting of three steps shows that there are at least three types of surface species occurring on the catalyst surface. However, a reactivity test and an investigation of surface species after adding a second metal (Fe, Sn, Co, Cr or W) to Pt/Al₂O₃ indicate that only (C_lH_mO_n)_HT species play an important role in NO reduction at a low operating temperature. This revised version was published online in June 2006 with corrections to the Cover Date.     

H3PO→H2POH异构化反应的LMO研究

The localized molecular orbital (LMO) theory is used to study the reaction mechanism of the isomerization reaction: H_3PO→H_2POH. The energy transition state (TS) of the reaction is also obtained by Powell's mehtod using 6-31G basis set. The resluts show that the lone pair electrons of oxygen atom play an forortant role in this reaction.     

Catalytic properties of LnSrCoO4 (Ln = La, Sm) in the oxidation of CO and C3H8

Perovskite-like LnSrCoO₄(Ln=La, Sm) mixed oxides of K₂NiF₄ structure were synthesized by the polyglycol gel method and used successfully for CO and C₃H₈ oxidation for the first time. The structure was characterized by means of XRD, TEM, BET, O₂-TPD and CO₂-TPD, respectively. An oxidation mechanism over LnSrCoO₄is proposed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Dipole polarizability pseudospectra and C6 dispersion coefficients for H2–H2

Pseudostate decomposition of static dipole polarizabilities for ground state H₂⁺ from a Givens-Householder diagonalization of the excitation operator (

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H" height="17" width="20">₀−E₀) over an N-term basis of appropriate symmetry allows for a rapidly convergent evaluation of C₆ dispersion coefficients for H₂⁺–H₂⁺. 27-term pseudospectra of hypergeneralized James functions with a 30-term GGJ⁺ unperturbed wavefunction with an optimized scale factor δ=0.918 at R=2₀ give C₆ and γ₆ values that are accurate to no less than nine significant figures.     

Vapour-liquid equilibrium data for the systems C2H6 + N2, C2H4 + N2, C3H8 + N2, and C3H6 + N2

High pressure vapour-liquid equilibrium data for the C₂H₆ + N₂, C₂H₄ + N₂, C₃H₈ + N₂, and C₃H₆ + N₂ 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.     

Photocatalytic Synthesis of Hydrocarbon Oxygenates from C2H6 and CO2 over Pd-MoO3/SiO2 Catalyst

Pd-MoO3/SiO2 catalyst has been prepared using the method of incipient wetness impregnation. The photo absorbing behaviors and chemisorbing properties of the catalyst have been characterized by UV-vis spectra and TPD-MS experiments. The results indicated that metal Pd loaded on MoOe/SiO2 has a significant effect on the photo absorbing performance of MoO3/SiO2, and an obvious blue shift of the absorption edge is produced. Under UV irradiation, the chemisorption state of CO2 undergoes decomposing process to form CO at 481 K, and a two-site adsorption state of ethane can be formed at around 496 K. Photo-oxidation of ethane using carbon dioxide can mainly produce propanal, ethanol and acetaldehyde in the temperature range of 353-423 K. The presence of metal Pd improves the catalytic activity remarkably.     

Theoretical investigation on the reaction of N2O and CO catalyzed by Fe(C6H6)

The reaction of N₂O with CO, catalyzed by Fe⁺(C₆H₆) and producing N₂ and CO₂, has been investigated at the UB3LYP/6-311+G(d) level. The computation results revealed that the reaction of Fe⁺(C₆H₆), N₂O and CO, is an O-atom abstraction mechanism. For the reaction channels, the geometries and the vibrational frequencies of all species have been calculated and the frequency modes analysis also have been given to elucidate the reaction mechanism. On the basis for geometry optimizations, the thermodynamic data of these reactions channels have been calculated using the statistical theory at 295.15 K and pressure of 0.35 Torr. Using Eyring transition state theory with Wigner correction, the activation thermodynamic data, rate constant and frequency factors for the these reaction channels also have been given. The results showed that CO and N₂O do not react without catalyst and Fe⁺(C₆H₆) can excellently mediate the reaction of N₂O and CO.     

The Catalytic Dehydrogenation of c2h6 to c2h4 under non-Oxidative Conditions over the 6cr/g-al2o3Catalyst

In the present paper, the catalytic dehydrogenation of C₂H₆ to C₂H₄ under non-oxidative conditions was investigated in a fixed-bed micro-reactor under ambient pressure at 823 - 923 K. The 6Cr/g-Al₂O₃ catalyst was found to be the best catalyst among the g-Al₂O₃, SiO₂, MCM41, MgO and Si-2 supported chromium oxide catalysts. The features of the 6Cr/g-Al₂O₃ catalyst for the reaction could be listed as follows: (1) At 823 - 923 K, the C₂H₄ selectivity of 92.5-78.6% at a C₂H₆ conversion of 9.5-29.8% could be obtained. (2) The catalyst had the good regeneration performance, i.e., could be regenerated by air repeatedly. (3) The main products were C₂H₄, CH₄, H₂ and coke. No carbon oxides were identified.     

Measurement and interpretation of the integrated infrared intensities of C2H2 and C2D2

The absolute IR intensities of acetylene and perdeuterio acetylene have been measured using the Wilson-Wells-Penner-Weber method. The intensity data have been analyzed in terms of dipole moment derivatives, bond charge parameters and atomic polar tensors. The experimentally determined intensity parameters have been compared with the corresponding values obtained from ab initio calculations.     

Die Trennung von Ar und O2 sowie CH4, C2H6, C3H8 und C4H10

Ohne Zusammenfassung     

Semiempirical molecular dynamics studies of C60/C70 fullerene oxides: C60O, C60O2 and C70O

The spectral analysis indicates that all isomers of C₆₀O, C₇₀O and C₆₀O₂ have an epoxide-like structure (an oxygen atom bridging across a C–C bond). According to the geometrical structure analysis, there are two isomers of fullerene monoxide C₆₀O (the 5,6 bond and the 6,6 bond), eight isomers of fullerene monoxide C₇₀O and eight isomers of fullerene dioxide C₆₀O₂. In order to simulate the real reaction conditions at 300 K, the calculation of the different isomers of C₆₀O, C₆₀O₂ and C₇₀O fullerene oxides was carried out using the semiempirical molecular dynamics method with two different approaches: (a) consideration of the geometries and thermodynamic stabilities, and (b) consideration of the ozonolysis mechanism. According to the semiempirical molecular dynamic calculation analysis, the probable product of this ozonolysis reaction is C₆₀O with oxygen bridging over the 6–6 bond (C_2v). The most probable product in this reaction contains oxygen bridging across in the upper part of C₇₀ (6–6 bond in C₇₀O-2 or C₇₀O-4) an epoxide-like structure. C₆₀O₂-1, C₆₀O₂-3 and C₆₀O₂-5 are the most probable products for the fullerene dioxides. All of these reaction products are consistent with the experimental results. It is confirmed that the calculation results with the semiempirical molecular dynamics method are close to the experimental work. The semiempirical molecular dynamics method can offer both the reaction temperature effect by molecular dynamics and electronic structure, dipole moment by quantum chemistry calculation.     

夹心化合物Ni(C5H5)2的Xα研究

用Xα方法计算了Ni(C5H5)2的电子能级与归一化电荷,讨论了夹心化合物成键的特点,并用过渡态方法分析Ni(C5H5)2的光电子能谱及紫外可见吸收光谱,结果与实验相符。