Theoretical Study On The Degradation Of Methyl Ethyl Sulfite And Hydrogen Evolution Mechanism By The Design Based On The High Selectivity Of Gas-phase Negative Ions

The research theme of today's international chemical companies is green chemistry,which aims at the rational use of resources and energy to achieve sustainable development and requires the entire development and utilization process to be environmentally friendly,therefore,energy conservation and environmental protection are important elements in the development of the chemical industry.Gas-phase negative ion reaction is a very important part of chemical products and plays an important role in exploring the mechanism of synthesis of new green and efficient chemical products,which is a key area of research in chemical science and technology.In recent years,the use of small-molecule gas-phase negative ions to probe the physicochemical properties of various compounds has become a hot research topic.In this paper,high-level theoretical calculations are carried out based on the first nature principle using transition state theory and other fundamental theories,in which the specific gas-phase negative ions selected are NH₂^-and Al₂O_X^-.The full text is mainly divided into five chapters:Chapter 1 illustrates the essence of quantum chemistry by introducing the development and background of quantum chemical calculations,briefly introduces the three major theories of valence bond theory,molecular orbital theory and ligand field theory,as well as the progress and status of the corresponding theories,and summarizes the mechanism of gas-phase negative ion reactions.Chapter 2 gives a general description of the fundamental theories of quantum chemistry,and introduces in detail the calculation methods and quantum chemistry calculation software related to this paper.In the third chapter the MM\QM method was used to study the reaction of multi-component imino anions with methylethylsulfite.In the QM study,the B3LYP method was also compared with the Bhandhlyp method,and the following conclusions were drawn:(1)With different ratios of reactants,the number of molecules of the products changes,the most significant of which is that there is a significant correlation between the amount of NH₃ produced and the ratio of the reaction.At the same ratio,the number of molecules will slowly increase as the reaction ratio increases.In comparison,the number of molecules does not change regularly at different ratios.(2)The reaction is a multi-channel and multi-step reaction system,and the reaction system is relatively complex.Channel 1 is the best reaction channel,and the products are P1(CH₃CH₂OH+NSO^-+CH₂OH),P2(CH₃OSO^-+CH₃CHO+NH₃),P3(CH₃OSO₂^-+NH₃+C₂H₄),the energy of each stagnation point of the potential energy surface is lower than that of the reactant,and it has strong reactivity,which is consistent with the experimental results.(3)Channel 2 is second only to channel 1 due to the existence of a transition state with higher energy than the reactants.P4(CH₃OSO₂^-+NH₂CH₂CH₃)and P5(CH₂O+SO₂+NH₃+C₂H₅^-)are both the products of path 1 and path 2,but the higher potential barrier of path 2prevents the reaction from proceeding,so P4 is easier to detect than P5.In Chapter 4 in order to better understand the structure and accompanying reactivity of anion clusters,this paper explores the reactivity of the anion Al₂O_X^-(x=2?5)of small molecule aluminum oxide clusters based on the MM\QM method,where Al₂O_X^-represents an increase in the degree of cluster oxidation.Therefore,this paper compares the structures of aluminum-oxygen clusters calculated at 9 different theoretical levels.The results show that:(1)The most stable structure of aluminum-oxygen cluster anions arises from the rhombic geometry,which is similar to Al₂O₂.(2)The more O atoms bonded to Al atoms,the better the structural stability.For anions with the same degree of oxidation,the stability of the symmetric structure is higher than that of the asymmetric counterpart.(3)In the proposed DFT-D method,the M05-2X,M06-2X and?B97X-D functions are comparable to MP2 levels in studying the properties of anion clusters including structure,frequency and energy.(4)In aqueous solution,H₂O has a stronger effect on anions with more oxygen atoms,where asymmetric anions become more dominant over symmetric anions.In Chapter 5 the M06-2X method of DFT-D is used to investigate the mechanism of C-H bond activation of methane by Sc Al₂O₂,which establishes an important theoretical support for the application of Sc Al₂O₂ materials for hydrogen evolution.Conclusions:(1)Overall the duplex state is the main channel of the reaction,and the energy of the duplex state is not only lower than that of the reactants but also lower than that of the quadruplet state according to the analysis of the reaction potential energy surface(2)The duplex and quadruplet states have crossover points at the early stage of the reaction,and there is an orbital drill-through effect when spin flip occurs.(3)Sc Al₂O₂ clusters have H₂ formation by activating methane,but the geometric structure is unstable,but experimentally,the product can be obtained by the introduction of external conditions such as temperature and pressure,and the presence of hydrogen can be detected.(4)Sc plays a key catalytic role in the C-H bond activation of methane,and the hydrogen evolution of the material is achieved through progressive hydrogen transfer.