Preparation Of Metal-organic Framework Materials And Their Application For Acetylene Hydrochlorination

PVC is a very important chemical raw material.It is one of the most widely used products in the world.Preparation of polyvinyl chloride(PVC)from vinyl chloride monomer(VCM),ethane method,ethylene method and acetylene method are the main methods to produce VCM.Due to the"deficient oil,lean gas,rich coal"energy structure.So the acetylene method is the main method to synthesize vinyl chloride.At present,HgCl₂/AC catalyst is mainly used in industry.Due to the high volatility and toxicity of mercury,it is of great harm to human safety and environment.The shortage of mercury resources limits its application in practical production,so the substitution of mercury catalyst needs to be solved urgently.In order to solve this problem,a new type of green environmental protection mercury-free catalyst was studied in this paper.The chemical and physical properties of mercury-free catalysts were analyzed by XRD,BET,XPS,SEM and other characterization methods.And The catalytic mechanism was discussed.The details are as follows:(1)Metal-organic frame porous materials(MOFs)are a kind of coordination polymers with porous and ultra-high specific surface area.Bi is a heavy metal element in the P region.The outermost free orbit of Bi³⁺has a high affinity to the O and N donor atoms of organic ligands and can form stable complexes.In this paper,Bi-MOFs(BOFs)was prepared by hydrothermal method.In the post-treatment process,the products were washed with water and solvent respectively,roasted at different low temperatures.The catalyst is prepared for catalytic chlorination of acetylene.The results showed that the catalyst had the best catalytic performance and the yield of vinyl chloride was 15.8%when the calcination temperature was 200?and the catalyst was activated by hydrogen chloride for 2 h.(2)Under the conditions of hydrothermal synthesis,the catalytic performance of the catalyst is improved by changing the type of mineralization agent added,The results show that the catalytic performance of the catalyst is improved.Because NaOH is changed into KOH,Ba(OH)₂ and(C₆H₅)₄BNa₄.And,when(C₆H₅)₄BNa₄ was added,the catalytic performance was the best,and the yield of vinyl chloride was18%.(3)In order to improve the catalytic performance of BOF catalyst,BOF composite catalyst was prepared.The results show that the BOF composite catalyst greatly improves the initial activity of the catalyst,but decreases the stability due to the acceleration of carbon deposition rate.Through the analysis of the deactivation reason of the catalyst,it can be seen that the relative content of C increases after the reaction,which indicates that the catalyst produces carbon deposition in the process of acetylene hydrochlorination and covers the active site.After deactivation,Cl element appeared in the catalyst,which may be due to the strong adsorption of C₂H₃Cl or HCl on the surface of the catalyst,resulting in incomplete desorption.With the progress of the reaction,the undesorption C₂H₃Cl or HCl gradually accumulated and occupied the surface active site of the catalyst.In addition,thermogravimetric analysis shows that the serious carbon deposition of the catalyst after the reaction covers the active site of the catalyst,which is another reason for the deactivation of the catalyst.(4)The performance of acetylene hydrochlorination of porous carbon materials prepared by high temperature calcination with BOFs as precursor is similar to that of the porous carbon materials prepared by grinding method,and is obviously higher than that of the catalysts prepared in the previous part of this paper.The highest initial activity is 85%of that of industrial mercury.The characterization analysis showed that Bi was the main active component of the catalyst.The reason of catalyst deactivation was also analyzed:the Bi monoquity component decreased greatly,and the specific surface area decreased greatly.