Study Of Ru-based Catalyst With High Stability For Acetylene Hydrochlorination

The energy structure in China determines that the preparation of vinyl chloride by acetylene hydrochlorination reaction will be still the mainstream process for PVC production.At present,traditional mercury catalysts are used in industry.Mercury chloride is volatile and causes serious environmental pollution,endangering human health.The global ecology is being destroyed gradually,and environmental problems need to be solved urgently.Therefore,it is urgent to develop green,efficience and alternative mercury-free catalysts.This paper focuses on developing a Ru-based catalyst with high stability.First,betaine hydrochloride was selected as the Lewis base introduced into the preparation of ruthenium-based catalysts.Lewis acids（metals or metal ions）and Lewis bases（ligands）usually form thermodynamically inert adducts.It can stabilize the valence of the central metal.Through activity evaluation,the reaction activity and stability of the ruthenium catalyst after the introduction of betaine hydrochloride have been significantly improved.Characterization found that in the catalyst of ruthenium-betaine hydrochloride composite catalytic system,the metal active sites have good dispersion.Betaine hydrochloride and ruthenium trichloride form a Lewis acid-base pair,which protects the ruthenium species and reduces ruthenium species reduced during the reaction process,while also inhibiting the formation of coke deposits.Then,single-atom catalysis was introduced into the acetylene hydrochlorination reaction.A novel anchoring strategy was proposed for the ruthenium-based catalyst,and ruthenium-based catalysts with atomical dispersion were successfully prepared and applied to acetylene hydrochlorination.Experimental results show that the Ru N_x/SAC-APS single atom ruthenium catalysts exhibit excellent reactivity.Through ACTEM,XAFS and other characterization methods,it was verified that ruthenium exist as single atoms,and the coordination environment of the single atom of ruthenium is anchored on the surface of the catalyst through the interaction between Ru-N.The single-atom ruthenium catalyst not only achieves the highest metal atom utilization rate in theory,but also has better stability than the ruthenium catalyst prepared by the traditional impregnation method.Acetylene conversion of the single atom catalyst was 96.9%with the metal loading of 0.2 wt%under the reaction conditions of T=170°C,GHSV（C₂H₂）=180 h^-1,V（HCl）:V（C₂H₂）=1.15:1.After 600 hours of activity evaluation,the acetylene conversion remained 96.0%,and the catalyst deactivation rate was 0.015×10^-3 h^-1.The ruthenium single atom catalyst still maintained atomical dispersion after reaction,and only a small amount of ruthenium clusters appeared,which greatly reduces the deactivation phenomenon caused by the aggregation of metal active sites.