| The acetylene and hydrogen chloride are the main raw materials for the preparation of vinyl chloride monomers,meanwhile,ionic liquids,as a new reaction medium,can inhibit carbon deposit,improve the reaction selectivity,improve the stability of the catalyst and metal catalyst dispersion,stop the reunion of the metal in the acetylene hydrochlorination system,and enhance the activity of the catalysts greatly.So the ionic liquids have been more and more widely used in the study of acetylene hydrochlorination system.Since the reactant gas diffuses in the ionic liquids firstly and then reacts with the active site of the catalyst.however,the study of the interaction mechanism between ionic liquids and reaction gas without the influence of catalyst in acetylene hydrochlorination is still not very clear.In some existing studies,most of them summarized the dissolution rules of some gases through experimental data,and only a few of them used molecular dynamics method or quantum chemical calculation method to study.In this paper,the dissolution mechanism of gas molecules in ionic liquids is simulated by the method of Density Functional Theory（DFT）,to establish the dissolved mechanism model of acetylene and hydrogen chloride in ionic liquids at the micro level,which can not only fulfill the certain theoretical foundation for the mechanism research of subsequent gas molecules dissolved in ionic liquids,but also perfect the system of acetylene hydrochlorination with a certain degree of guidance.In this paper,the COSMO-RS model is used to calculate the macroscopic physicochemical properties of acetylene and hydrogen chloride in ionic liquids,and the Henry coefficient and solvation free energy data of acetylene and hydrogen chloride are obtained at different temperatures in the six ionic liquids([Bmim]+[Cl]-,[N4444]+[ME2PO4]-)described below,which indicated that the dissolution trend of acetylene in ionic liquids was similar to that of hydrogen chloride to some extent,and is speculated that the hydrogen atoms in acetylene have acidity.At the same time,the spontaneity of the gas dissolution process at the test temperature and the difficulty after the temperature rise were illustrated by the data of solvation free energy.At the micro level,the mechanism of acetylene or hydrogen chloride in ionic liquids was calculated by DFT.The calculation data of the action sites,action distance,bond property（AIM analysis）,bond energy,bond energy decomposition and charge transfer of acetylene or hydrogen chloride in ionic liquids were studied,and the following conclusions were obtained:1)The interaction between anions and cations in ionic liquids is mainly maintained by multi-site hydrogen bonding.2)The acetylene mainly interacts with anion in the form of hydrogen bond when it interacts with ionic liquids,and the action site is chlorine atom or oxygen atom with strong electronegative in anion.At the same time,acetylene will form aπ-πaccumulation with cations with circular structure.3)The hydrogen chloride will form the double covalent bond structure of Cl-H-Cl or the covalent bond and hydrogen bond structure of O-H???Cl with the anions in ionic liquids system.4)When acetylene or hydrogen chloride interacts with the ionic liquids,the gas molecules will form a competitive relationship with the cation,and weaken each other’s interaction with anions.Meanwhile,it can be concluded that the weakening effect of the cation has a greater impact on the hydrogen chloride by comparing the optimized structure of acetylene or hydrogen chloride with the anion alone.5)The Hirshfeld charge transfer of the key atoms in acetylene or hydrogen chloride and ionic liquids systems is well correlated with the macroscopic dissolution Henry coefficient.The structure of both acetylene and hydrogen chloride in ionic liquids system was analyzed and calculated from the microscopic level:1)The acetylene and hydrogen chloride will form a functional structure of Cl-H-Cl???H（C2H2）with anions in[Bmim]+[Cl]-.2)The hydrogen atoms of hydrogen chloride interact with[Cl]-to form hydrogen bonds,while[Cl]-will form a hydrogen bond structure of Cl-H???Cl???H（C2H2）with hydrogen atom in acetylene in[N4444]+[Cl]-.3)The oxygen atom of the ionic liquids form a covalent bond with the hydrogen atoms of hydrogen chloride,the chlorine atom of hydrogen chloride will change from covalent bond to hydrogen bond with the original hydrogen atom of hydrogen chloride,and finally form the structure of O-H???Cl,while acetylene forms the hydrogen bond of O???H（C2H2）with another oxygen atom of ionic liquids in[Bmim]+[CH3COO]-,[Bmim]+[ME2PO4]-,[N4444]+[CH3COO]-or[N4444]+[ME2PO4]-.4)The acetylene and hydrogen chloride act differently when they enter the ionic liquid system as the first and second acting gas.When the gas enters the system as the first gas,it acts on the system with more energy than when it enters the system as the second gas.But the sum of the bond energy of acetylene and hydrogen chloride with the ionic liquids is basically same whatever the gas enters the system as the first gas or the second gas.Which indicates that the competition between the two kinds of gases is a stock competition,and that the same gas as the first acting gas will have a stronger force than the same gas as the second acting gas.In this paper,the mechanism model of acetylene and hydrogen chloride in ionic liquids was established at the molecular microscopic level via DFT calculation,it fills a certain vacancy in the research of interaction between acetylene and hydrogen chloride reaction gas and ionic liquid for the subsequent acetylene hydrochlorination reaction.In addition,theoretical calculation will also play a very important role in the chemical microscopic simulation in the future. |
PDF Full Text Request