Study On Supported Cu-based Catalysts For Ethane Oxychlorination To Vinyl Chloride

Vinyl chloride?VCM?is a very important and basic chemical raw material.At present,there are three production methods of VCM:acetylene method,ethylene oxychlorination and ethane oxychlorination method.Compared with acetylene process and ethylene oxychlorination,ethane oxychlorination method has the advantages of cheaper cost and less pollution in the production process.However,the most important problem to realize the industrialization of ethane oxychlorination is to develop excellent catalyst with long life and high thermal stability.Therefore,supported Cu-based catalysts were prepared,in which with perovskite compounds of high-temperature resistance as promoter,with copper chloride as active component and with ?-Al₂O₃ as supporter.The synergistic effect between the perovskite promoter and the active component copper chloride and the performance of the catalysts were studied.At the same time,the effect of potassium ion modification on physical and chemical properties of catalysts were also investigated.The catalysts were characterized by means of XRD,BET,H2-TPR,XPS,TG-DSC,SEM,O2-TPD and C2H6-TPD etc.to investigate the relationship between the phase compositions,structure,surface species,redox properties and the catalytic performance.The main experimental results and discussion are as follows:?1?CuCl₂-?-Al₂O₃ and single,double perovskite compounds were prepared by impregnation method and sol-gel method,respectively,then single and double perovskite supported copper based catalysts were prepared by mechanical mixing method.The catalytic performance for ethane oxychlorination reaction of double perovskite supported Cu-based series catalysts La₂BCoO₆-CuCl₂-?-Al₂O₃?B = Fe?Al and Mn?and the corresponding single perovskite supported Cu-based series catalysts LaBO3-CuCl₂-?-Al₂O₃?B = Fe?Co?Al and Mn?were investigated in detail.Catalytic activity test results showed that the ethane conversion and the selectivity to vinyl chloride of double perovskite supported Cu-based series catalysts are superior to the corresponding single perovskite supported Cu-based series catalysts.In the double perovskite structure,the octahedral construct of B atoms is arranged alternately by B'06 and B"06,B' and B" ions are separated by oxygen into B'-O-B"structure with super exchange interaction,and the 180 degree super exchange interaction of B'-O-B" structure plays an important role in the double perovskite structure,so that the double perovskite supported Cu-based catalysts exhibit excellent catalytic performance.?2?Catalysts La₂MnCoO₆-CuCl₂-?-Al₂O₃,La₂FeCoO₆-CuCl₂-?-Al₂O₃ and La₂AlCoO₆-CuCl₂-?-Al₂O₃ were prepared by mechanical mixing method.The catalytic activity test showed that the C2H6 conversion of the above three catalysts were 98%,97%and 100%respectively,the selectivity to C2H3Cl were about 38%,47%and 44%,respectively.By comparison,the activity of La₂AlCoO₆-CuCl₂-?-Al₂O₃ catalyst was better than that of catalysts La₂MnCoO₆-CuCl₂-?-Al₂O₃ and La₂FeCoO₆-CuCl₂-?-Al₂O₃.?3?In order to study the synergistic effect between double perovskite promoter and active component CuCl₂,the catalytic performance of ?-Al₂O₃,CuCl₂,CuCl₂-?-Al₂O₃,La₂-AlCoO₆,La₂AlCoO₆-?-Al₂O₃ and La₂AlCoO₆-CuCl₂-?-Al₂O₃ catalysts was compared and analysed,it can be found that La₂AlCoO₆-CuCl₂?y-Al₂O₃ catalyst shows a superior catalytic performance for ethane oxychlorination with the C2H6 conversion of 100%and the C2H3Cl selectivity to 43.8.%.The superior catalytic performance of La₂AlCoO₆-CuCl₂-?-Al₂O₃ catalyst can be attributed to the abundant surface adsorbed oxygen species on the surface of catalyst and the synergistic effect between La₂AlCoO₆ promoter and active component CuCl₂,which reduces the reduction activation energy of Cu2+?Cu+ reduction process efficiently,and the Cu2+ species in La₂AlCoO₆-CuCl₂-?-Al₂O₃ catalyst are easier to be reduced,thus improves the catalytic performance of ethane oxychlorination.?4?La₂AlCoO₆-CuCl₂-?-Al₂O₃ catalyst is modified by potassium ion.Different content K modified perovskite supported Cu-based catalysts La₂-xKxAlCoO₆-CuCl₂-?-Al₂O₃?x=0.1,0.2,0.3,0.4,0.5?were prepared by mechanical mixing method.It is found that when x = 0.4,the weight percent of perovskite-type oxides in the CuCl₂-?-Al₂O₃ is 30%,the catalyst La1.6K0.4AlCoO₆-CuCl₂-?-Al₂O₃ possesses best C2H6 conversion of 100%and the C2H3Cl selectivity to 58%.The conversion of C2H6 and selectivity to C2H3Cl nearly maintain steady during the 40 h time-on-stream and no deactivation of catalyst was detected.The conversion of C2H6 and selectivity to C2H3Cl had little change,it is obvious that La1.6K0.4AlCoO₆-CuCl₂-?-Al₂O₃ catalyst not only has excellent catalytic activity,but also has good stability.