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1.
H2CO和NO2反应机理的密度泛函理论计算研究 总被引：2，自引：2，他引：2
用密度泛函理论方法在UB3LYP/ 6-311++G(d,p)并包含零点能水平上计算得到了H2CO和NO2反应的势能面.在势能面上找到了由H2CO和NO2反应生成HCO和trans-HONO的两条反应通道.直接H迁移反应通道的势垒只有90.54 kJ*mol-1,是主要的反应通道,其TST速率是7.9 cm3*mol-1*s-1,与文献值相符;另一条通道是H2CO异构化为trans-HCOH,然后C位H迁移,最后生成的HOC分子异构化为HCO,这条通道反应势垒高达348.03 kJ*mol-1,是一条次要反应通道. 相似文献
2.
Dr. Ojus Mohan Shambhawi Shambhawi Prof. Rong Xu Prof. Alexei A. Lapkin Prof. Samir H. Mushrif 《ChemCatChem》2021,13(10):2420-2433
A multiscale analysis combining density functional theory (DFT) and microkinetic modeling is performed to resolve the uncertainties in CO2 methanation reaction mechanism and kinetics on popular Ni and Ru catalysts. The most debated issues are the activation routes of CO2 and CO (hydrogenation or direct dissociation) and whether the reaction proceeds with or without forming a CO* intermediate. We investigated a comprehensive reaction network of 46 elementary reactions, involving multiple CO2, CO activation routes and side reactions using a benchmarked DFT functional. Our study shows that the dominant pathway at 550 K and 10 atm includes direct dissociation of CO2* to CO* on both Ni and Ru surfaces. On Ru, CO* undergoes hydrogenation to form COH* that further dissociates to C*, whereas on Ni, HCO* is formed that gives CH* upon dissociation. The rate determining steps on Ni and Ru are HCO* dissociation to CH* and O* and CH3* hydrogenation to CH4, respectively. We further find that selectivity of the reaction on Ni is higher than that on Ru, whereas activity of Ru is higher. 相似文献
3.
Sakari Tuokko Prof. Dr. Petri M. Pihko Dr. Karoliina Honkala 《Angewandte Chemie (International ed. in English)》2016,55(5):1670-1674
The chemoselective hydrogenation of acrolein on Pt(111) and Pd(111) surfaces is investigated employing density functional theory calculations. The computed potential energy surfaces together with the analysis of reaction mechanisms demonstrate that steric effects are an important factor that governs chemoselectivity. The reactions at the C=O functionality require more space than the reactions at the C=C functionality. Therefore the formation of allyl alcohol is more favorable at low coverage, while the reduction of the C=C bond and the formation of propanal becomes kinetically more favorable at higher coverage. The elementary reaction steps are found to follow different reaction mechanisms, which are identified according to terminology typically used in organometallic catalysis. The transition state scaling (TSS) relationship is demonstrated and the origin of multiple TSS lines is linked to variation of an internal electronic structure of a carbon skeleton. 相似文献
4.
A mononuclear Mn(I) pincer complex [Mn(Ph2PCH2SiMe2)2NH(CO)2Br] was disclosed to catalyze the pinacolborane (HBpin)-based CO2 hydroboration reaction. Density functional calculations were conducted to reveal the reaction mechanism. The calculations showed that the reaction mechanism could be divided into four stages: (1) the addition of HBpin to the unsaturated catalyst C1 ; (2) the reduction of CO2 to HCOOBpin; (3) the reduction of HCOOBpin to HCHO; (4) the reduction of HCHO to CH3OBpin. The activation of HBpin is the ligand-assisted addition of HBpin to the unsaturated Mn(I)-N complex C1 generated by the elimination of HBr from the Mn(I) pincer catalyst. The sequential substrate reductions share a common mechanism, and every hydroboration commences with the nucleophilic attack of the Mn(I)-H to the electron-deficient carbon centers. The hydride transfer from Mn(I) to HCOOBpin was found to be the rate-limiting step for the whole catalytic reaction, with a total barrier of 27.0 kcal/mol, which fits well with the experimental observations at 90 °C. The reactivity trend of CO2, HCOOBpin, HCHO, and CH3OBpin was analyzed through both thermodynamic and kinetic analysis, in the following order, namely HCHO>CO2>HCOOBpin≫CH3OBpin. Importantly, the very high barrier for the reduction of CH3OBpin to form CH4 reconciles with the fact that methane was not observed in this catalytic reaction. 相似文献
5.
Sambath Baskaran Prof. Cong-Qiao Xu Ya-Fei Jiang Yang-Gang Wang Prof. Dr. Jun Li 《Chemphyschem》2021,22(4):378-385
Single-atom catalysts (SACs) have attracted extensive attention owing to their high catalytic activity. The development of efficient SACs is crucial for applications in heterogeneous catalysis. In this article, the geometric configuration, electronic structure, stabilitiy and catalytic performance of phosphorene (Pn) supported single metal atoms (M=Ru, Rh, Pd, Ir, Pt, and Au) have been systematically investigated using density functional theory calculations and ab initio molecular dynamics simulations. The single atoms are found to occupy the hollow site of phosphorene. Among the catalysts studied, Ru-decorated phosphorene is determined to be a potential catalyst by evaluating adsorption energies of gaseous molecules. Various mechanisms including the Eley-Rideal (ER), Langmuir-Hinshelwood (LH) and trimolecular Eley-Rideal (TER) mechanisms are considered to validate the most favourable reaction pathway. Our results reveal that Ru−Pn exhibits outstanding catalytic activity toward CO oxidation reaction via TER mechanism with the corresponding rate-determining energy barrier of 0.44 eV, making it a very promising SAC for CO oxidation under mild conditions. Overall, this work may provide a new avenue for the design and fabrication of two-dimensional materials supported SACs for low-temperature CO oxidation. 相似文献
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Yuya Hu Dr. Zhihong Wei Anna Frey Dr. Christoph Kubis Chang-Yue Ren Dr. Anke Spannenberg Dr. Haijun Jiao Dr. Thomas Werner 《ChemSusChem》2021,14(1):363-372
A series of hydroxy-functionalized phosphonium salts were studied as bifunctional catalysts for the conversion of CO2 with epoxides under mild and solvent-free conditions. The reaction in the presence of a phenol-based phosphonium iodide proceeded via a first order rection kinetic with respect to the substrate. Notably, in contrast to the aliphatic analogue, the phenol-based catalyst showed no product inhibition. The temperature dependence of the reaction rate was investigated, and the activation energy for the model reaction was determined from an Arrhenius-plot (Ea=39.6 kJ mol−1). The substrate scope was also evaluated. Under the optimized reaction conditions, 20 terminal epoxides were converted at room temperature to the corresponding cyclic carbonates, which were isolated in yields up to 99 %. The reaction is easily scalable and was performed on a scale up to 50 g substrate. Moreover, this method was applied in the synthesis of the antitussive agent dropropizine starting from epichlorohydrin and phenylpiperazine. Furthermore, DFT calculations were performed to rationalize the mechanism and the high efficiency of the phenol-based phosphonium iodide catalyst. The calculation confirmed the activation of the epoxide via hydrogen bonding for the iodide salt, which facilitates the ring-opening step. Notably, the effective Gibbs energy barrier regarding this step is 97 kJ mol−1 for the bromide and 72 kJ mol−1 for the iodide salt, which explains the difference in activity. 相似文献
10.
Hsueh‐Chien Li Jeng‐Da Chai Ming‐Kang Tsai 《International journal of quantum chemistry》2014,114(12):805-812
In this study, 12 bound complexes were selected to construct a database for testing 15 dispersion‐improved exchange‐correlation (XC) functionals, including hybrid generalized gradient approximation (GGA), modified using the Grimme's pairwise strategy, and double hybrid XC functionals, for specifically characterizing the CO2 binding by alcoholamines. Bound complexes were selected based on the characteristics of their hydrogen bonds, dispersion, and electrostatic (particularly between the positive charge of CO2 and the lone pair of N of alcoholamines) interactions. The extrapolated binding energy from the aug‐cc‐pVTZ (ATZ) to aug‐cc‐pVQZ (AQZ) basis set at the CCSD(T)/CBS(MP2+DZ) level was used as the reference for the XC functional comparison. M06‐2X produced the optimal agreement if the optimized geometries at MP2/ATZ level were chosen for all the test bound complexes. However, M06‐L, ωB97X, and ωB97, and were preferred if the corresponding density functional theory (DFT) optimized geometries were adapted for the benchmark. Simple bimolecular reaction between CO2 and monoethanolamine simulated using polarizable continuum solvation model confirmed that ωB97, ωB97X, and ωB97XD qualitatively reproduced the energetics of MP2 level. The inconsistent performance of the tested XC functionals, observed when using MP2 or DFT optimized geometries, raised concerns regarding using the single‐point ab initio correction combined with DFT optimized geometry, particularly for determining the nucleophilic attack by alcoholamines to CO2. © 2014 Wiley Periodicals, Inc. 相似文献
11.
Dr. Kang Liu Ganghai Ni Tao Luo Prof. Junwei Fu Hongmei Li Prof. Min Liu Prof. Zhang Lin 《Chemphyschem》2023,24(19):e202300050
Single-atom M−N2 (M=Fe, Co, Ni) catalysts exhibit high activity for CO2 reduction reaction (CO2RR). However, the CO2RR mechanism and the origin of activity at the single-atom sites remain unclear, which hinders the development of single-atom M−N2 catalysts. Here, using density functional theory calculations, we reveal intermediates-induced CO2RR activity at the single-atom M−N2 sites. At the M−N2 sites, the asymmetric *O*CO configuration tends to split into *CO and *OH intermediates. Intermediates become part of the active moiety to form M−(CO)N2 or M-(OH)N2 sites, which optimizes the adsorption of intermediates on the M sites. The maximum free energy differences along the optimal CO2RR pathway are 0.30, 0.54, and 0.28 eV for Fe−(OH)N2, Co−(CO)N2, and Ni−(OH)N2 sites respectively, which is lower than those of Fe−N2 (1.03 eV), Co−N2 (1.24 eV) and Ni−N2 (0.73 eV) sites. The intermediate modification can shift the d-band center of the spin-up (minority) state downward by regulating the charge distribution at the M sites, leading to less charge being accepted by the intermediates from the M sites. This work provides new insights into the understanding of the activity of single-atom M−N2 sites. 相似文献
12.
Density Functional Study on the Reaction Mechanism for the Reaction of Ni^＋ with Ethane 总被引：1，自引：0，他引：1
The mechanism of the reaction of Ni^ (^2D) with ethane in the gas-phase was studied by using density functional theory.Both the B3LYP and BLYP functionals with standard all-electron basis sets are used to give the detailed information of the potential energy surface (PES) of [Ni,C2,H6]^ . The mechanisms forming the products CH4 and H2 in the reaction of Ni^ with ethane are proposed.The reductive eliminations of CH4 and H2 are typical addition-elimination reactions.Each of the two reactions consists of two elementary steps:C-C or C-H bond activations to form inserted species followed by isomerizations to from product-like intermediate.The rate determining steps for the elimination reactions of forming CH4 and H2 are the isomerization of the inserted species rather than C-C or C-H bond activations .The elimination reaction of forming H2 was found to be thermodynamically favored compared to that of CH4. 相似文献
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为更清晰地揭示M＋与SCO基元反应的机理, 采用密度泛函B3LYP方法, 在6-311＋＋G**基组水平上研究了Cu＋＋SCO和Zn＋＋SCO反应体系. 对反应势能面上各驻点的几何构型进行了全优化, 用频率分析方法和内禀反应坐标(IRC)方法对过渡态进行了验证. 在Cu＋与SCO的反应中, 对影响反应机理和反应速率的势能面交叉现象进行了讨论, 运用Hammond假设和Yoshizawa等的内禀反应坐标垂直激发的计算方法找到了势能面交叉点. 计算结果表明, C—S和C—O键的活化都是通过插入消去机理, 但C—S键的活化在能量上更占优势. 计算确认了标题反应的主通道, 所有的计算结果与实验吻合. 相似文献
14.
Green systems able to capture or fix CO2 are becoming more important specially to reduce environmental impacts. In this work, the mechanism of insertion of CO2 into styrene oxide (STYO) both in the absence and presence of the catalyst 1‐butyl‐3‐methyl‐imidazolium bromide (BMIm Br) was investigated through calculations based on density functional theory in the ωB97X‐D level. Two different routes were considered and it was shown they are energetically available and compete against each other. For both routes, the rate‐determinant step is the ring opening of STYO resulting from the nucleophilic attack of the Br? on the C atom from STYO and is associated mainly to the participation of the cation and the anion from the catalyst in the reaction. Reactive indices and noncovalent interaction analysis were used as a tool to investigate this reason. This work allowed a better comprehension of the underlying mechanism and the supplied data provide valuable support for the design of new more efficient ionic liquid catalyst. © 2015 Wiley Periodicals, Inc. 相似文献
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Dr. Hai‐Zhu Yu Xue‐Jiao Tian Dr. Xiang Lin Prof. Guo‐Hua Hu Prof. Zhi‐Min Dang 《化学:亚洲杂志》2014,9(12):3472-3481
The thiolate‐catalyzed Tishchenko reaction has shown high chemoselectivity for the formation of double aromatic‐substituted esters. In the present study, the detailed reaction mechanism and, in particular, the origin of the observed high chemoselectivity, have been studied with DFT calculations. The catalytic cycle mainly consisted of three steps: 1,2‐addition, hydride transfer, and acyl transfer steps. The calculation results reproduce the experimental observations that 4‐chlorobenzaldehyde acts as the hydrogen donor (carbonyl part in the ester product), while 2‐methoxybenzaldehyde acts as the hydrogen acceptor (alcohol part in the product). The two main factors are responsible for such chemoselectivity: 1) in the rate‐determining hydride transfer step, the para‐chloride substituent facilitates the hydride‐donating process by weakening the steric hindrance, and 2) the ortho‐methoxy substituent facilitates the hydride‐accepting process by stabilizing the magnesium center (by compensating for the electron deficiency). 相似文献
16.
采用密度泛函理论B3LYP方法研究了金团簇阴离子 和 催化CO氧化反应的详细机理. 计算结果表明, O2分子比CO分子更容易吸附到金团簇上. 第二分子CO能有效降低较强O—O键断裂所需能量. CO氧化反应过程需要两个CO分子协同进行. 和 催化CO氧化反应均通过碳酸根中间体进行, 活化能分别为0.607 和0.658 eV. 和 都能在常温下有效催化CO氧化反应. 这些结果与以前的实验和理论研究一致. 相似文献
17.
应用密度泛函理论研究了反应通道(a)C2H3+NO→CH3+NCO和(b)C2H3+NO→OH+C2H2N的反应机理.在B3LYP/6-31G(d)水平上优化了反应物、中间体、过滤态、产物的几何构型,通过频率分析确定了11个中间体和10个过渡态.所有的反应物、中间体、过渡态、产物都在CCSD/6-311++G(d,p)水平上进行了单点能较正.并讨论了反应的异构化过程.计算结果表明10是能量最低的中间体,比反应物的能量低308 479kJ/mol;过渡态1/3,2/5,3/4,4/8比反应物的能量高,其中3/4是能量最高的过渡态,比反应物的能量高91 894kJ/mol.通道(a)和(b)的理论放热值分别为111 059和96 619kJ/mol. 相似文献
18.
D-苯丙氨酸与Cu＋(1S0, 3d10)气相反应理论研究 总被引：1，自引：0，他引：1
用量子化学密度泛函(DFT)方法研究D-苯丙氨酸与一价基态金属阳离子Cu＋在气相中反应的机理. 在B3LYP/6-31G*水平上, 优化了反应包含的4个反应通道的反应物、中间体、过渡态和产物的几何构型, 并采用B3LYP/DZVP, B3LYP/[6-311＋G**(C,H,O)＋Lanl2dz(Cu)], B3LYP/6-311＋G**, MP2/6-311＋G** 等方法对各驻点进行了单点能计算. 通过对计算结果的分析, 获得了其单重态反应势能面的一般轮廓、各驻点几何构型优化参数, 明确了其反应机理. 相似文献
19.
He Bian Honghong Zhang Ling Pei Qian Wang Fang Wang Yun Zhang Jinshe Chen 《International journal of quantum chemistry》2020,120(8):e26146
Density functional theory was adopted in this work to reveal the reaction mechanism of CH2SH with HO2. Reaction rate constants were computed from 200 to 2000 K using the transition state theory combined with Wigner and Eckart tunneling correction. Moreover, localized orbital locator, atoms in molecules and Mayer bond order analyses were used to study the essence of chemical bonding evolution. Eleven singlet paths and three triplet ones are located on the potential surface (PES). The results show that the main products on the singlet PES are 1CH2S and H2O2, whereas on the triplet PES they are CH3SH + 3O2, which are coincident with the similar reaction of CH3S and HO2. This conclusion is also supported by rate constant calculation results. Interestingly, all the possible paths are involved in the hydrogen transfer. The results have provided underlying insights to the analogous reactions and further experimental studies. 相似文献
20.
为研究镍掺杂对铁基催化剂上二氧化碳加氢生成C_1和C_2烃类产物的影响,应用密度泛函理论进行了相关计算.在Fe(110)和Ni-Fe(110)表面上, CH~*物种是最有利的生成CH_4和C_2H_4的C_1物种(CH_x~*),其最可能的生成路径为CO_2→HCOO~*→HCO~*→CH~*.尽管CO_2直接解离为CO~*在动力学上相较于加氢生成HCOO~*和COOH~*是较为有利的,但CO~*进一步加氢生成HCO~*在能量上是不利的,其倾向于逆向解离回到CO~*. CH~*物种可以通过三步加氢反应生成CH_4或者经C—C耦合及两步加氢生成C_2H_4.在Fe(110)表面上,对甲烷和乙烯产物选择性起决定作用的基元反应能垒之间差异仅为0.10 eV,因此两者选择性相近.在将Ni原子引入Fe(110)表面后,生成甲烷与乙烯的选择性差异变大,导致乙烯的选择性提高.计算结果表明,添加少量金属Ni能够促进CO_2转化为CH~*,及两个CH~*物种发生C—C耦合和进一步加氢转化为乙烯. 相似文献