The direct synthesis of C2 hydrocarbons （ethylene, acetylene and ethane） from methane is one of the most important task in C1 chemistry. Higher conversion of methane and selectivity to C2 hydrocarbons can be real-iz...The direct synthesis of C2 hydrocarbons （ethylene, acetylene and ethane） from methane is one of the most important task in C1 chemistry. Higher conversion of methane and selectivity to C2 hydrocarbons can be real-ized through plasma reaction. In order to explore the reaction process and mechanism, the possible reaction paths （1）—（4） were proposed on coupling reaction of methane through plasma and studied theoretically using semi-PM3 method [PM3 is parameterization method of modified neglect of diatomic overlap （MNDO）] including determining the transition state, calculating the activation energy and thermodynamic state functions and analyzing the bond or-der and intrinsic reaction coordinate. The reaction heat results indicate that the reactions （2） and （4） are exothermic, while reactions of （1） and （3） are endothermic. The activation energy results show that activation energy for reac-tions （1） and （2） was much lower than that of reaction paths （3） and （4）. Therefore, paths （1） and （2） is the favorable reaction path energetically. More interestingly by comparing the intrinsic reaction coordinated （IRC） of the reaction paths （1） and （2）, it is found that the variations of bond lengths in reaction path （1） has a crucial effect on the poten-tial energy, while in reaction path （2）, the adjustment of the system geometry also contributes to the whole potential energy of the system.展开更多
The mercury sulfidation experiments were conducted in the pH range from 1 to 13.The results show that Hg(Ⅱ) reacted with equimolar S(Ⅱ) has the lowest remained Hg(Ⅱ) concentration(9.7 μg/L) at pH 1.0 and the highe...The mercury sulfidation experiments were conducted in the pH range from 1 to 13.The results show that Hg(Ⅱ) reacted with equimolar S(Ⅱ) has the lowest remained Hg(Ⅱ) concentration(9.7 μg/L) at pH 1.0 and the highest remained concentration(940.8 μg/L) at pH 13.0.Meanwhile,the changes of pH values were monitored exactly,which reveal that solution pH values change when mixing the same pH value solutions of HgCl2 and Na2S.In order to explain the phenomena and determine the reaction paths of Hg(Ⅱ) reacting with S(Ⅱ) in the solution,the concerned thermodynamics was studied.Species of S(Ⅱ)-H2O system and Hg(Ⅱ)-H2O system at different pH values were calculated,and then the species distribution diagrams of S(Ⅱ)-H2O system,Hg(Ⅱ)-H2O system and Hg(Ⅱ)-Cl--OH--H2O system were drawn.Combining the experimental data and thermodynamic calculation,the mechanism of Hg(Ⅱ) reacting with S(Ⅱ) was deduced.The results indicate that different species of S(Ⅱ) and Hg(Ⅱ) have the diverse reaction paths to form HgS precipitate at different pH values and the standard Gibbs free energies change(△r GmΘ)of those equations are also calculated,which can provide a guidance for mercury-containing wastewater treatment with Na2S.展开更多
On-surface Ullmann coupling has been intensely utilized for the tailor-made fabrication of conjugated frameworks towards molecular electronics, however, reaction mechanisms are still limitedly understood. Herein, we p...On-surface Ullmann coupling has been intensely utilized for the tailor-made fabrication of conjugated frameworks towards molecular electronics, however, reaction mechanisms are still limitedly understood. Herein, we provide a comprehensive elucidation of the surface Ullmann coupling of 2,7-dibromopyrene (Br2Py) on Ag(111) by scanning tunnelling microscopy (STM), X-ray photoelectron spectroscopy (XPS) and density function theory (DFT), and reveal that the Ullmann reaction path is unique regardless of predesigned assembled structures. By manipulating deposition conditions, diverse assembled architectures have been constructed for Br2Py on Ag(111), including the ladder phase, parallel arrangement, hexagonal patterns from monomers or Kagome lattices based on organometallic (OM) dimers. Intriguingly, stepwise annealing leads to an identical reaction diagram for the surface Ullmann coupling from individual assembled structures convergent into the brick-wall-pattern OM dimers first, which is deemed to be a stable phase, and then into elongated OM chains in order and eventually long-range polymers with direct C-C coupling. While the reaction mechanism is demonstrated to be dominated by the metal coordinated and halogen bonding motifs, interestingly, it has also been revealed that surface adatoms and dissociated Br atoms play a crucial role in coupling reactions. In contrast to previous reports demonstrating the manipulation of Ullmann reactions by preassembled strategy, herein, weak intermolecular interaction in assembled nanostructures is immediately suppressed by strong covalent bonding during reactions. Importantly, our report proposes essential insights on fundamental understanding of surface Ullmann coupling towards high-yield surface synthesis.展开更多
It is a key step for reducing waste generation in chemical processes to design op-timal reaction paths. In this paper, methods of waste minimization for reaction path synthesis problems are proposed to realize eco-ind...It is a key step for reducing waste generation in chemical processes to design op-timal reaction paths. In this paper, methods of waste minimization for reaction path synthesis problems are proposed to realize eco-industrial production mode with minimum waste emission. A new conception of simple stoichiometric reaction is presented for reaction path synthesis problem. All simple stoichiometric reactions can be obtained by mathematical transformation for atom matrix of a reaction system. Based on the conception, a two-tier optimization method for complex reaction path synthesis problems is addressed. The first step is to determine the eco-nomic optimal overall reactions, and the second step to decompose each overall reaction into several sub-reactions and find out the best thermodynamic feasible reaction path. Further, a method of reaction path synthesis with waste closed-cycle is proposed based on simple stoichiometric reactions for achieving zero waste emission to poly-generation problem of multi-products. Case studies show that the proposed methods can efficiently solve practical re-action path synthesis problems.展开更多
Bifurcation of potential energy surfaces(PES) along the reaction paths (RPS) has stimu-lated great interest of some chemists. It was first discovered by Dewar et al. intheir study on the decyclization of cyclobutene, ...Bifurcation of potential energy surfaces(PES) along the reaction paths (RPS) has stimu-lated great interest of some chemists. It was first discovered by Dewar et al. intheir study on the decyclization of cyclobutene, and that the Wood-Hoffmann rule lost展开更多
The dynamical properties on reaction path （IRC） in internal coordinates have been obtained, which in. clude ω<sub>K</sub> （frequencies orthogonal to IRC）, L<sub>K</sub> （vibrational modes...The dynamical properties on reaction path （IRC） in internal coordinates have been obtained, which in. clude ω<sub>K</sub> （frequencies orthogonal to IRC）, L<sub>K</sub> （vibrational modes）, B<sub>KF</sub> （coupling constants between the IRC and vibra tions orthogonal to it）, B<sub>KL</sub> （coupling constants between every two vibrations orthogonal to IRC）. A set of theory of teac. tion path in molecular internal coordinates has been also constructed. The dynamical properties, including ω<sub>K</sub>, B<sub>KF</sub> B<sub>KL</sub> of the reaction H<sup>1</sup>O<sup>2</sup>H<sup>3</sup>+H<sup>4</sup>→H<sup>1</sup>O<sup>2</sup>+H<sup>3</sup>H<sup>4</sup> have been calculated, which explicitly explain the interaction, chang ing trend and contribution of each chemical bond （including bond angle） in the reaction.展开更多
A vector-fiber bundle structure of the reaction path Hamiltonian, which has been introduced by Miller, Handy and Adams, is explored with respect to molecular vibrations orthogonal to the reaction path. The symmetry of...A vector-fiber bundle structure of the reaction path Hamiltonian, which has been introduced by Miller, Handy and Adams, is explored with respect to molecular vibrations orthogonal to the reaction path. The symmetry of the fiber bundle is characterized by the real orthogonal group O(3N- 7) for the dynamical system with N atoms. Under the action of group O(3N- 7). the kinetic energy of the reaction path Hamiltonian is left invariant. Furthermore , the invariant behaviour of the Hamiltonian vector fields is investigated.展开更多
The two possible reaction paths of producing ethane on coupling reaction of methane through plasma were theoretically investigated by B3LYP and MP2 methods with 6-311G* respectively and further compared with the previ...The two possible reaction paths of producing ethane on coupling reaction of methane through plasma were theoretically investigated by B3LYP and MP2 methods with 6-311G* respectively and further compared with the previous results calculated from B3LYP/6-31G*. The new investigated results consistently confirmed the previous conclusion. And the influences of the calculation methods and basis sets on the calculated results were also dis-cussed.展开更多
基金Supported by the National Natural Science Foundation of China (No.20606023).
文摘The direct synthesis of C2 hydrocarbons （ethylene, acetylene and ethane） from methane is one of the most important task in C1 chemistry. Higher conversion of methane and selectivity to C2 hydrocarbons can be real-ized through plasma reaction. In order to explore the reaction process and mechanism, the possible reaction paths （1）—（4） were proposed on coupling reaction of methane through plasma and studied theoretically using semi-PM3 method [PM3 is parameterization method of modified neglect of diatomic overlap （MNDO）] including determining the transition state, calculating the activation energy and thermodynamic state functions and analyzing the bond or-der and intrinsic reaction coordinate. The reaction heat results indicate that the reactions （2） and （4） are exothermic, while reactions of （1） and （3） are endothermic. The activation energy results show that activation energy for reac-tions （1） and （2） was much lower than that of reaction paths （3） and （4）. Therefore, paths （1） and （2） is the favorable reaction path energetically. More interestingly by comparing the intrinsic reaction coordinated （IRC） of the reaction paths （1） and （2）, it is found that the variations of bond lengths in reaction path （1） has a crucial effect on the poten-tial energy, while in reaction path （2）, the adjustment of the system geometry also contributes to the whole potential energy of the system.
基金Project(50925417) supported by China National Funds for Distinguished Young ScientistsProject(50830301) supported by the Key Project of the National Natural Science Foundation of China+2 种基金Project(308019) supported by the Key Science and Technical Project of Ministry of Science and Technology of ChinaProject(2007BAC25B01) supported by the National Key Project of Science and Technical Supporting Programs Funded by Ministry of Science and Technology of China during the 11th Five-Year PlanProject(08JJ3020) supported by the Natural Science Foundation of Hunan Province, China
文摘The mercury sulfidation experiments were conducted in the pH range from 1 to 13.The results show that Hg(Ⅱ) reacted with equimolar S(Ⅱ) has the lowest remained Hg(Ⅱ) concentration(9.7 μg/L) at pH 1.0 and the highest remained concentration(940.8 μg/L) at pH 13.0.Meanwhile,the changes of pH values were monitored exactly,which reveal that solution pH values change when mixing the same pH value solutions of HgCl2 and Na2S.In order to explain the phenomena and determine the reaction paths of Hg(Ⅱ) reacting with S(Ⅱ) in the solution,the concerned thermodynamics was studied.Species of S(Ⅱ)-H2O system and Hg(Ⅱ)-H2O system at different pH values were calculated,and then the species distribution diagrams of S(Ⅱ)-H2O system,Hg(Ⅱ)-H2O system and Hg(Ⅱ)-Cl--OH--H2O system were drawn.Combining the experimental data and thermodynamic calculation,the mechanism of Hg(Ⅱ) reacting with S(Ⅱ) was deduced.The results indicate that different species of S(Ⅱ) and Hg(Ⅱ) have the diverse reaction paths to form HgS precipitate at different pH values and the standard Gibbs free energies change(△r GmΘ)of those equations are also calculated,which can provide a guidance for mercury-containing wastewater treatment with Na2S.
基金Fruitful discussions with Dr.Qitang Fan are greatly appreciated.This work was financially supported by National Natural Science Foundation of China(Nos.11874380,11874427,and U1732267)the National Key Research and Development Program of China(No.2016YFA040130201)the Hundred Talents Program of Chinese Academy of Sciences.
文摘On-surface Ullmann coupling has been intensely utilized for the tailor-made fabrication of conjugated frameworks towards molecular electronics, however, reaction mechanisms are still limitedly understood. Herein, we provide a comprehensive elucidation of the surface Ullmann coupling of 2,7-dibromopyrene (Br2Py) on Ag(111) by scanning tunnelling microscopy (STM), X-ray photoelectron spectroscopy (XPS) and density function theory (DFT), and reveal that the Ullmann reaction path is unique regardless of predesigned assembled structures. By manipulating deposition conditions, diverse assembled architectures have been constructed for Br2Py on Ag(111), including the ladder phase, parallel arrangement, hexagonal patterns from monomers or Kagome lattices based on organometallic (OM) dimers. Intriguingly, stepwise annealing leads to an identical reaction diagram for the surface Ullmann coupling from individual assembled structures convergent into the brick-wall-pattern OM dimers first, which is deemed to be a stable phase, and then into elongated OM chains in order and eventually long-range polymers with direct C-C coupling. While the reaction mechanism is demonstrated to be dominated by the metal coordinated and halogen bonding motifs, interestingly, it has also been revealed that surface adatoms and dissociated Br atoms play a crucial role in coupling reactions. In contrast to previous reports demonstrating the manipulation of Ullmann reactions by preassembled strategy, herein, weak intermolecular interaction in assembled nanostructures is immediately suppressed by strong covalent bonding during reactions. Importantly, our report proposes essential insights on fundamental understanding of surface Ullmann coupling towards high-yield surface synthesis.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 29836140).
文摘It is a key step for reducing waste generation in chemical processes to design op-timal reaction paths. In this paper, methods of waste minimization for reaction path synthesis problems are proposed to realize eco-industrial production mode with minimum waste emission. A new conception of simple stoichiometric reaction is presented for reaction path synthesis problem. All simple stoichiometric reactions can be obtained by mathematical transformation for atom matrix of a reaction system. Based on the conception, a two-tier optimization method for complex reaction path synthesis problems is addressed. The first step is to determine the eco-nomic optimal overall reactions, and the second step to decompose each overall reaction into several sub-reactions and find out the best thermodynamic feasible reaction path. Further, a method of reaction path synthesis with waste closed-cycle is proposed based on simple stoichiometric reactions for achieving zero waste emission to poly-generation problem of multi-products. Case studies show that the proposed methods can efficiently solve practical re-action path synthesis problems.
文摘Bifurcation of potential energy surfaces(PES) along the reaction paths (RPS) has stimu-lated great interest of some chemists. It was first discovered by Dewar et al. intheir study on the decyclization of cyclobutene, and that the Wood-Hoffmann rule lost
基金Project supported by the National Natural Science Foundation of China (Grant No.29773007).
文摘The dynamical properties on reaction path （IRC） in internal coordinates have been obtained, which in. clude ω<sub>K</sub> （frequencies orthogonal to IRC）, L<sub>K</sub> （vibrational modes）, B<sub>KF</sub> （coupling constants between the IRC and vibra tions orthogonal to it）, B<sub>KL</sub> （coupling constants between every two vibrations orthogonal to IRC）. A set of theory of teac. tion path in molecular internal coordinates has been also constructed. The dynamical properties, including ω<sub>K</sub>, B<sub>KF</sub> B<sub>KL</sub> of the reaction H<sup>1</sup>O<sup>2</sup>H<sup>3</sup>+H<sup>4</sup>→H<sup>1</sup>O<sup>2</sup>+H<sup>3</sup>H<sup>4</sup> have been calculated, which explicitly explain the interaction, chang ing trend and contribution of each chemical bond （including bond angle） in the reaction.
基金Project supported by the National Natural Science Foundation of Chain.
文摘A vector-fiber bundle structure of the reaction path Hamiltonian, which has been introduced by Miller, Handy and Adams, is explored with respect to molecular vibrations orthogonal to the reaction path. The symmetry of the fiber bundle is characterized by the real orthogonal group O(3N- 7) for the dynamical system with N atoms. Under the action of group O(3N- 7). the kinetic energy of the reaction path Hamiltonian is left invariant. Furthermore , the invariant behaviour of the Hamiltonian vector fields is investigated.
基金Project supported by the Natural Science Foundation of Tianjin Education Commission (No. 20020902) and the Youth Fund Project of Tianjin Nor-mal University (No. 52LE31).
文摘The two possible reaction paths of producing ethane on coupling reaction of methane through plasma were theoretically investigated by B3LYP and MP2 methods with 6-311G* respectively and further compared with the previous results calculated from B3LYP/6-31G*. The new investigated results consistently confirmed the previous conclusion. And the influences of the calculation methods and basis sets on the calculated results were also dis-cussed.
