Study On Catalyst Prepared By Chitosan For Acetylene Hydrochlorination

Nowadays,there are three processes for producing vinyl chloride（VCM）in the world:ethane,ethylene oxychloride and acetylene.China is rich in coal,less oil and less gas,which makes the synthesis of VCM by acetylene method have broad prospects in China.However,the production of VCM by acetylene method will use toxic mercury-based catalyst,which will cause great harm to the environment and human body.Therefore,the development of low cost and high performance mercury-free catalyst is the industry demand of calcium carbide PVC.Carbon-based catalysts have attracted extensive attention in acetylene hydrochlorination because of their excellent physical and chemical properties.At the same time,there are some problems such as expensive raw materials and complex preparation process.Therefore,this thesis explores a green and cheap raw material chitosan,and explores the performance of nitrogen-doped carbon catalysts,Cu-N-C catalysts,and Fe-N-C catalysts based on chitosan in acetylene hydrochlorination and their effects on the reaction were investigated.This thesis mainly has the following three aspects:（1）Preparation of nitrogen-doped carbon materials based on chitosan for acetylene hydrochlorination.In this study,a nitrogen-doped carbon catalyst for acetylene hydrochlorination was prepared using a simple strategy of direct calcination of chitosan.The total nitrogen content in Chi800-H catalyst was5.88%,including pyridinic nitrogen,pyrrolic nitrogen and graphitic nitrogen.Due to the presence of pyridinic nitrogen and pyrrolic nitrogen active centers,the acetylene conversion of Chi800-H catalyst can reach 91%at 220℃,but its stability is unsatisfactory.In order to improve its stability,Echi800-H catalyst was prepared by using zinc chloride pore expansion on the catalyst.The specific surface area of the catalyst can reach 1299.08 m²/g after pore expansion.Echi800-H showed 94%acetylene conversion and good stability for up to 60 h at 220℃.（2）Study on the performance of Cu-N-C catalyst derived from chitosan for acetylene hydrochlorination.In this thesis,Chitosan and CuCl₂·2H₂O were used as raw materials to prepare Cu-N-C catalysts.The catalytic properties of Cu-N-C catalysts in acetylene hydrochlorination were investigated.The Cu-N-C catalyst exhibits 83%acetylene conversion at 180℃and considering a GHSV（C₂H₂）of 90 h-¹.The excellent performance of the catalyst is attributed to the formation of Cu-N,and the synergistic effect of Cu and N is the main reason for the improvement of catalytic performance.The Cu-N-C catalyst has less carbon deposition in the hydrochlorination of acetylene,and can operate stably for 80 h.（3）Chitosan derived low-cost Fe-N-C nitrogen-carbon catalyst for hydrochlorination of acetylene.In this thesis,using chitosan and FeCl₃·6H₂O as raw materials,Fe-N-C catalyst was prepared for hydrochlorination of acetylene by a simple and convenient method.Fe-N-C catalyst exhibits good catalytic performance,acetylene conversion can reach 91%at 180℃and considering a GHSV（C₂H₂）of 36 h-¹,and stable operation for 40 h.The good performance of Fe-N-C catalyst is attributed to the synergistic effect of high pyrrole nitrogen content and iron nitrogen doping.The deactivation of the catalyst is due to the reduction of active site due to the formation of carbon during the reaction.