Bi-based Catalyst Prepared By One Pot Method And Its Catalytic Activity For Acetylene Hydrochlorination

Polyvinyl chloride?PVC?,which is one of the most widely used general plastics in the world,is mainly manufactured by vinyl chloride monomer?VCM?.There are two major production technologies,including ethylene method and acetylene method,to produce vinyl chloride monomer.Bsaed on the energy structure of poor storage in petroleum and gas versus rich storage in coal,the acetylene method is dominating production route of VCM in China.For the reaction,carbon-supported mercuric chloride catalyst?HgCl₂/AC?was selected as catalyst,however,the volatilization of mercuric chloride during the reaction not only have a severely negetive impact on the lifetime of the catalyst,but aslo would cause seriously environmental pollution problem and do harm to human health.Therefore,to develop a nontoxic,environmentally friendly non-mercuric catalyst is essential to the vinyl chloride industry.In present,domestic and foreign researchers have done lots of research and made some achievements.In order to improve the catalytic activity and stability of catalyst,the researchers change the interaction between active component and carrier by adding additive or modifying the supports.Nevertheless,there are few reports to preparation method of mercury-free catalyst.It was reported in the literature that the preparation method of catalyst have great importance to improve performance.Thus,in this paper,we take “one pot method” and use activated carbon as support to prepare non-noble metal Bi-based catalyst,and the preparation methods and conditions were studied systematically.In the same conditions,the catalytic performance of catalysts was prepared by one pot method and incipient-wetness impregnation method was compared,the relationship between the morphology of catalyst and catalytic performance was investigated,and the effect of different treatment reagents on catalytic performance of Bi-based catalysts for acetylene hydrochlorination was studied.Corresponding characterization?XRD?SEM?TEM?TG?ICP?EDS?were employed to analyzing the effect of preparation method on catalytic activity of Bi-based catalysts,and the deactivation reason of Bi-based catalysts prepared by one pot method was discussed.Mainly experiment contents and the corresponding results are as follows:?1?The Bi-based catalysts prepared by two methods,one pot method and incipient-wetness impregnation method,their catalytic performance were tested at 160°C,feed volume ratio V?HCl?/V?C₂H₂?=1.25,GHSV=120 h-1.Compared with incipient-wetness impregnation method,catalytic performance of catalyst prepared by one pot method is higher,acetylene conversion was about 64.86%,VCM selectivity was about 96.23%,and the acetylene conversion still reaches 46.78% after 12 h reaction.Characterization results show that the catalysts prepared by one pot method Bi existence form is BiOCl and have microspheres morphology,this would provide higher specific surface area and increase the number of surface active sites of the catalyst.Meanwhile,the catalysts have higher Bi content and stronger coke resistance.So,it can significantly improve the catalytic activity.In addition,the catalytic performance of Bi/AC catalysts prepared by one pot method is better when the content of Bi is 25% and the carrier is coal-based activated carbon.?2?The Bi-based catalysts were prepared by one pot method,the effect of HCl,CH3 OH,H2O,EG and CH3CH2 OH as reaction solvents on catalytic performance was investigated,their catalytic performance were tested at 160°C,feed volume ratio V?HCl?/V?C₂H₂?=1.25,GHSV=120 h-1.The catalytic activity order is: EG > H2 O > CH3 OH > HCl > CH3CH2 OH.Besides,the reaction conditions?temperature,time and pH?of one pot method have a great influence on catalytic performance.Combining evaluation performance find that the optimal conditions of Bi/AC catalyst prepared by one pot method are reaction temperature=160oC,time=2 h,pH=2.0,acetylene conversion is about 77 %,vinyl chloride selectivity is about 90 % at the moment.Characterization results show that the BiOCl displays well-crystal structure and microspherical morphology under the optimal preparation conditions,and the carbon deposition is one of the main reasons for the catalyst deactivation.?3?The Bi-based catalysts prepared by one pot method under reaction temperature=160oC,time=2 h,pH=2.0 are processed by H3PO4,CH3 COOH,HNO3,Citric Acid?CA?,PEG6000,Urea so,and their catalytic performance were tested at 160°C,feed volume ratio V?HCl?/V?C₂H₂?=1.25,GHSV=120 h-1.The results show that,compared with the untreated catalyst,the catalytic performance for acetylene hydrochlorination are enhanced inordinately after processing,the stability order is: Urea > HNO3 > CH3 COOH > CA > PEG6000 > H3PO4.It is found that the urea concentrations have some influences on catalytic performance,and higher or lower concentration is detrimental to acetylene hydrochlorination.The catalyst treated with 10% Urea have the best catalytic performance,the acetylene conversion was about 82%,VCM selectivity was about 91%,and the acetylene conversion still reaches 70% after 13 h reaction,the stability of catalyst was obviously improved.Characterization results show that the specific surface area and total pore volume are increased,particle size of BiOCl is decreased,dispersity of metal Bi improved and the activity centers of catalyst surface are enhanced after catalyst treatment.At the same time,it could decrease carbon depositions and active ingredient Bi loss,enhancing the catalytic performance of the Bi-based catalysts.