Study Of Supported Ionic Liquid Ru-based Catalysts For Acetylene Hydrochlorination

The calcium carbide acetylene-based method is the dominant way to produce vinyl chloride monomer（VCM）at present in China.The industrial catalyst for the acetylene-based method is HgCl₂/C,which is toxic and volatile,resulting in severe damage to both the human health and the environment.Therefore,it is it is urgent to explore the environmentally benign acetylene hydrochlorination process based on novel efficient nonmercury catalysts for the sustainable development of the polyvinyl chloride（PVC）industry.Firstly,supported ionic liquid catalysts Ru@TPPB/AC were prepared via the wetness impregnation technique using RuCl₃ precursor and tetraphenylphosphonium bromide ionic liquid,and then the obtained catalysts were assessed the catalytic activity for acetylene hydrochlorination.The results indicated that the addition of TPPB significantly improved the catalytic performance of Ru-based catalyst.The acetylene conversion of the optimal 1%Ru@15%TPPB/AC catalyst was maintained at99.7%at 48 h and the selectivity to VCM was also 99.7%(T=170°C,GHSV_C2H2=360h^-1,and V_HCl/V_C2H2=1.15).Characterized by CO pulse chemisorption,TEM,XPS and TGA,among other methods,it is indicated that TPPB IL could effectively improve the dispersion of Ru species,suppress the reduction of active Ru species,and inhibit the coke deposition during the acetylene hydrochlorination reaction.Based on the study of Ru@TPPB/AC catalyst,we further broadened the range of the ionic liquids with similar structure to TPPB used in catalyst preparation and synthesized a series of supported ionic liquid catalyst as Ru@IL/AC by the same method as before.Catalytic activity tests results showed that the activity of Ru-based catalysts was greatly improved after the addition of quaternary phosphonium ionic liquids.Combining the experiments,catalyst characterizations with density functional theory（DFT）calculations,we proposed a possible catalytic mechanism.The reason for enhanced catalytic performance of Ru@IL/AC catalysts is that ionic liquids possess strong adsorption and activation ability for reactant HCl,which ensures C₂H₂to react with HCl timely,thus reducing the amount of coke deposition caused by the polymerization of activated C₂H₂ and intermediate chlorovinyl.Besides,the addition of ionic liquid strengthens the desorption capacity of VCM,which can also effectively reduce the coke deposition result from the polymerization of product.Finally,we performed the long-term stability test using 0.1%Ru@15%TPPB/AC catalyst with a high activity and a low Ru loading in 800 h,demonstrating its potential value in the industrial production of PVC mercury-free catalysts.