Study On The Catalytic Performance Of Ruthenium Complexe Catalytsts For Acetylene Hydrochlorination

As we all know,polyvinyl chloride?PVC?has a wide range of applications in daily production and life,and the common methods for the synthesize of vinyl chloride monomer?VCM?are ethylene oxychlorination and acetylene hydrochlorination.Ethylene oxychlorination that consumes large amounts of fossil energy is adopted in the western countries rich in oil reserves.Because of the special energy structure of“rich coal,poor oil,little gas”,the commonly adopted method for industrial production of VCM in China is acetylene hydrochlorination.In the industrialproductionofVCMbyacetylenehydrochlorination,activated-carbon-supported HgCl₂ is often used as the catalyst,which causes serious environmental pollution because of its easy sublimation and the further circulation into the atmospher.In 2013,the United Nations reached the Minamata Convention,which requires that the amount of mercury consumed per unit of PVC production by2020 to be reduced by 50%of that in the year 2010,and that the process with mercury as the catalyst in 2025 will be eliminated.Therefore,it is urgent to develop an economical and environment-friendly mercury-free catalyst,which exhibits the advantages of higher catalytic activity and stability.In this paper,starting from the modification of activated carbon carrier,we investigated the effects of surface groups and solvents on the preparation of ruthenium complex catalysts,and assessed the catalytic performance of the complex catalysts for acetylene hydrochlorination.Compared with the Ru/AC catalysts prepared with RuCl₃ as precursor,the ruthenium complex catalysts have potential for industrial application.This article focuses on the following three parts:?1?Ru-based catalysts were prepared with activated carbon?AC?and acid-modified AC supported tetrapropylammonium perruthenate?TPAP?respectively.The results indicated that the TPAP/AC-HCl catalyst exhibited the best performance with the conversion falling from 95.9%to 90.8%in 48 hours'reaction under the conditions of 180 ^oC,a GHSV?C₂H₂?of 180 h^-1,and the feed ratio V_HCl/V_C2H2 of 1.15.The analysis and characterization results of BET,FT-IR,XRD,TGA,XPS and H₂-TPR showed that the substitution of RuCl₃ precursor with high valent TPAP species led to more ruthenium oxides active species in the catalysts;the acidification treatment of carrier in TPAP/AC catalyst can produce an enhanced interaction between the active species and the modified functional groups on the carrier,and it was beneficial to inhibit the carbon deposition and sintering of ruthenium species in the reaction process,greatly increased the adsorption ability of reactants,and further increased the amount of dominating active species in the catalysts,thus improving the catalytic performance.?2?Ru-based catalysts were prepared with AC and acid-modified AC as supports,ruthenium acetylacetonate?R-O-Ru?as the active component,ethanol and acetone as solvents and investigated the effects of dispersion solvent on the catalytic performance of the catalysts.The activity test results revealed that the?R-O-Ru?_E/AC-HNO₃ catalyst exhibited the best performance with the conversion falling from 95.2%to 86.5%in 48 hours'reaction under the conditions of 180 ^oC,a GHSV?C₂H₂?of 180 h^-1,and the feed ratio V_HCl/V_C2H2 of 1.15.The analysis and characterization results of BET,TG,XPS,TGA and TPD showed that the substitution of RuCl₃ precursor with R-O-Ru species led to more ruthenium oxides active species in the catalysts;activated carbon modified by acid,especially by nitric acid,can enhance the interaction between Ru species and the modified functional groups on the carrier.When ethanol is used as solvent,the adsorption capacity of the catalyst to the reactants can be further improved,and then the catalytic activity can be improved.?3?Ru-based catalysts were prepared in ethanol solution with AC and acid-modified AC as supports and tris-?triphenylphosphine?ruthenium dichloride??-P-Ru?as Ru precursor.The test results revealed that the?-P-Ru/AC-HNO₃catalyst shows superior catalytic performance with the conversion falling from 97.2%to 87.0%in 48 hours'reaction under the conditions of 180 ^oC,a GHSV?C₂H₂?of 180h^-1,and the feed ratio V_HCl/V_C2H2 of 1.15.The analysis and characterization results of BET,TG,XPS,ICP-AES and TPD showed that the substitution of inorganic RuCl₃precursor by organic?-P-Ru complex species in the catalysts resulted in more active species and tends to confine them in the micro-pores;the modification of carbon support by nitric acid in?-P-Ru catalyst may produce an interaction between the functional groups on modified support and Ru species,which is favorable to anchor and then reduce the loss of active species during the reaction,further increase the amount of dominating Ru species,and greatly improve the reactants adsorption ability on the catalysts,thus enhancing the performance of the resultant catalysts.