有场和无场下高价乙炔阳离子的理论研究

使用(U)B3LYP方法,选用6-311++G(d,p)基组,研究了在无场和不同外加电场强度下高价乙炔阳离子[C2H2n+(n = 2, 3 4)]的结构、稳定性以及去质子化解离反应。我们的研究表明,在无场下,C2H22+和C2H23+是稳定的,但是C2H24+并不稳定,而是自发解离生成两个C+和两个H+,C2H24+的这种解离归因于库仑爆炸。当外加电场强度达到0.06 a.u.时,C2H22+自发解离生成C2H+ + H+,而对于C2H23+,当外加电场仅仅为0.0075 a.u.时,就自发解离生成C2H2+ + H+,C2H22+和C2H23+在场中的这种自发解离可以归结为场致解离。此外,使用(U)B3LYP方法计算了在无场和有场下由C2H2电离生成C2H22+、C2H23+和C2H24+的绝热电离能和垂直电离能。     

羰基铁催化乙炔羰化合成丙烯酸甲酯的研究

通过对羰基金属催化乙炔羰基化反应的研究,发现羰基铁具有合成丙烯酸甲酯的催化活性.并分别考察了五羰基铁的用量、CO与C2H2的摩尔比、温度、初始压力等因素对反应的影响,进而,对Fe(CO)5催化反应的活性物种进行了推测.结果表明,以甲醇为溶剂,在140℃,CO压力为4.2 MPa、n(Fe(CO)5)/n(C2H2)=0.26条件下,单一的Fe(CO)5能够催化乙炔羰化,丙烯酸甲酯的选择性可达97%.其中,n(CO)/n(C2H2)值越高,产物丙烯酸甲酯的选择性越高.     

Towards Structural‐Functional Mimics of Acetylene Hydratase: Reversible Activation of Acetylene using a Biomimetic Tungsten Complex

The synthesis and characterization of a biomimetic system that can reversibly bind acetylene (ethyne) is reported. The system has been designed to mimic catalytic intermediates of the tungstoenzyme acetylene hydratase. The thiophenyloxazoline ligand S‐Phoz (2‐(4′,4′‐dimethyloxazolin‐2′‐yl)thiophenolate) is used to generate a bioinspired donor environment around the W center, facilitating the stabilization of W–acetylene adducts. The featured complexes [W(C₂H₂)(CO)(S‐Phoz)₂] ( 2 ) and [WO(C₂H₂)(S‐Phoz)₂] ( 3 ) are extremely rare from a synthetic and structural point of view as very little is known about W–C₂H₂ adducts. Upon exposure to visible light, 3 can release C₂H₂ from its coordination sphere to yield the 14‐electron species [WO(S‐Phoz)₂] ( 4 ). Under light‐exclusion 4 re‐activates C₂H₂ making this the first fully characterized system for the reversible activation of acetylene.     

Tin-sulfur based catalysts for acetylene hydrochlorination

In the present work, tin-sulfur based catalysts were prepared using Na₂SO₃ and (CH₃SO₃)₂Sn and were tested in acetylene hydrochlorination. Based on the analysis of experiments results, the acetylene conversion of (CH₃SO₃)₂Sn/S@AC is still over 90%after a 50 h reaction, at the reaction conditions of T = 200 ^oC, V_HCl/V_C2H2 = 1.1:1.0 and C₂H₂-GSHV = 15 h^–1. According to the results of X-ray photoelectron spectroscopy (XPS), HCl adsorption experiments, and acetylene temperature programmed desorption (C₂H₂-TPD), it is reasonable to conclude that the interaction between Sn and S not only can retard the oxidation of Sn²⁺ in catalysts but also strengthen the reactant adsorption capacity of tin-based catalysts. Furthermore, results obtained from nitrogen adsorption/desorption and XPS proved that the CH₃SO₃- can effectively decrease the coke deposition of (CH₃SO₃)₂Sn/AC and thus prolong the lifetime of (CH₃SO₃)₂Sn/AC.     

MoP催化剂上乙炔选择性催化加氢

通过高温还原法制得磷化钼(MoP)催化剂,采用X射线衍射和原位x射线光电子能谱对其进行了表征,并考察其催化乙炔选择性加氢性能.结果表明,在650℃经H2还原制得的催化剂中形成了大量的低价态物种MoP,但仍含有大量的高价态Mo和P物种,该催化剂具有加氢活性中心和缺电子中心双重功能,在乙炔选择性加氢反应中,乙炔转化率超过9...     

Methane coupling in microwave plasma under atmospheric pressure

Methane coupling in microwave plasma under atmospheric pressure has been investigated.The effects of molar ratio n(CH4)/n(H2),flow rate and microwave power on the reaction have been studied.(1)With the decrease of n(CH4)/n(H2)ratio,methane conversion,C2 hydrocarbon yield,energy yield and space-time yield of acetylene increased,but the yield of carbon deposit decreased.(2)With the increase of microwave power,energy yield of acetylene decreased,but space-time yield of acetylene increased.(3)With the increase of flow rate,energy yield and space-time yield of acetylene increased first and then decreased.Finally,under the reaction conditions of CH4 flow rate of 700 mL/min,n(CH4)/n(H2)ratio of 1/4 and microwave power of 400 W,the energy yield and space-time yield of acetylene could reach 0.337 mmol/kJ and 12.3 mol/(s m3),respectively.The reaction mechanism of methane coupling in microwave plasma has been investigated based on the thermodynamics of chemical reaction.Interestingly,the acetylene yield of methane coupling in microwave plasma was much higher than the maximum thermodynamic yield of acetylene.This phenomenon was tentatively explained from non-expansion work in the microwave plasma system.     

High-resolution overtone spectra of molecular complexes

A high-resolution spectrum of the acetylene–water complex has been recorded in the overtone range. Two bands of C₂H₂–D₂O were analysed, corresponding to the overtone excitations of either the acetylene or the water units. The vibrational shifts and the upper states rotational constants were retrieved, demonstrating that the geometry of the complex is only slightly modified by the excitation. A larger linewidth was observed for the 2CH band than for the 2OD?+?DOD band, probably due to the direct coupling of the 2CH excitation with the dissociation coordinate.     

The 2CH excitation band in C2H2–N2O and 2CH+torsion combination bands in C2H2–N2O and C2H2–CO2

A preliminary analysis of the 2CH excitation band in C₂H₂–N₂O in the 1.5 µm range (K. Didriche, C. Lauzin, P. Macko, M. Herman and W.J. Lafferty, Chem. Phys. Letters 469, 35 (2009).), only considering 117 low J-, and K_a - vibration-rotation lines, is significantly extended thanks to the analysis of new spectra including very regular series of lines with J/K_a up to 31/15. 1271 b-type lines were assigned. Perturbations are briefly discussed. The rotational temperature in the experiments is estimated to be 20?K and the upper state mean half-time is 1.6?ns for non perturbed levels. The previous analyses of the 2CH + torsion band in C₂H₂–N₂O and in C₂H₂–CO₂ (C. Lauzin, K. Didriche, T. Földes and M. Herman, Mol. Phys. 109, 2105 (2011).), are also extended to include 286 and 234 lines, respectively, also correcting for calibration errors. New rotational constants are obtained using a rigid rotor Hamiltonian by simultaneously fitting the ground, 2CH and 2CH + torsion states in C₂H₂–N₂O, and the latter state, only, in C₂H₂–CO₂.     

The Effect of Cluster Size on the Intra-Cluster Ionic Polymerization Process

Polyaromatic hydrocarbons (PAHs) are widespread in the interstellar medium (ISM). The abundance and relevance of PAHs call for a clear understanding of their formation mechanisms, which, to date, have not been completely deciphered. Of particular interest is the formation of benzene, the basic building block of PAHs. It has been shown that the ionization of neutral clusters can lead to an intra-cluster ionic polymerization process that results in molecular growth. Ab-initio molecular dynamics (AIMD) studies in clusters consisting of 3–6 units of acetylene modeling ionization events under ISM conditions have shown maximum aggregation of three acetylene molecules forming bonded C₆H₆⁺ species; the larger the number of acetylene molecules, the higher the production of C₆H₆⁺. These results lead to the question of whether clusters larger than those studied thus far promote aggregation beyond three acetylene units and whether larger clusters can result in higher C₆H₆⁺ production. In this study, we report results from AIMD simulations modeling the ionization of 10 and 20 acetylene clusters. The simulations show aggregation of up to four acetylene units producing bonded C₈H₈⁺. Interestingly, C₈H₈⁺ bicyclic species were identified, setting a precedent for their astrochemical identification. Comparable reactivity rates were shown with 10 and 20 acetylene clusters.