Study Of Ru-based Ionic Liquids For Acetylene Hydrochlorination In Liquid Phase

Mercury catalyst is used for acetylene hydrochlorination in industrial production of vinyl chloride in China,which may cause serious pollution and threat to the environment and human beings.And other solid phase non mercury catalysts such as Au and Pt are hindered because of their high cost and inactivation from carbon deposition.On the contrary,the liquid phase has the advantages of uniform temperature and excellent mass transfer.Therefore,it is urgent to find a perfect reaction medium.As a kind of nonvolatile medium with wide liquid path,ionic liquids have attracted more and more attention for acetylene hydrochlorination in gas-liquid phase.In this paper,a ionic liquid was prepared by using ruthenium（Ru）component and organic hydrochloride,and its catalytic performance for acetylene hydrochlorination was evaluated.The effects of types of cations and corresponding catalytic reaction conditions on the catalytic performance were investigated.The experimental results showed that[Hnmpo]Cl-xRuCl₃IL（x=0.0075mol·L-1）possessed 89.6%acetylene conversion at the reaction conditions of 170℃,50 h^-1acetylene space velocity,and V（HCl）:V（C₂H₂）=1.15.Furthermore,the conversion of acetylene did not decrease within 140 h of reaction.The ionic liquid was characterized by TGA,FTIR,ESI-MS,ICP-OES,and XPS characterization.With theoretical calculations it was confirmed that the ionic liquid could inhibit the formation of carbon deposition to avoid deactivation and had strong thermal stability under the above reaction conditions.In addition,Ru（Ⅲ）is the main active component in the ionic liquid,and the content of its high valence component affects the catalytic performance to a great extent.In order to further improve the catalytic stability,the ionic liquid was compounded with Sn（Ⅱ）.At the optimal reaction conditions consistent with the above,xRuCl₃-ySnCl₂/[Hnmpo]Cl IL(x=0.0075mol·L^-1,y=0.0225mol·L^-1)was screened out which had the preferable initial catalytic activity.The life test showed that the conversion of acetylene and the selectivity of vinyl chloride remained above 96.0%and 99.6%respectively within 700 h without downward trend,showing a strong stability.Combined with UV-Vis,ICP-OES,XPS characterization and theoretical calculation,it was found that the introduction of SnCl₂provided new Cl atom coordination for Ru,enhancing the adsorption and activation ability of ionic liquid catalyst for HCl.The valence state of Ru species was stabilized and the reduction deactivation caused by excessive C₂H₂was prevented.Therefore,the bimetallic ionic liquid had excellent catalytic performance and stability.According to the DFT calculation,the mechanism of cyclic catalytic reaction was proposed.