Structure Activity Relationship Between Preparation Of C_xN_y Catalyst Based On N-Containing Polymer And Hydrochlorination Of Acetylene

Due to its unique physical and chemical properties,polyvinyl chloride(PVC)products are widely used in our production and life,and the production of PVC is inseparable from vinyl chloride(VCM).Therefore,the production of vinyl chloride is of great significance.At present,vinyl chloride is mainly produced by acetylene hydrochlorination,ethylene process and ethane process.As China's resources present a state of more coal,less oil and less gas,acetylene method is mainly used in China's industrial production to prepare vinyl chloride,which accounts for more than 70%of its production capacity,and has formed a mature production process.Hg Cl₂catalyst is widely used in the preparation of vinyl chloride by acetylene method,and Hg Cl₂is volatile and highly toxic.Therefore,we are now facing not only the environmental pollution caused by mercury chloride volatilization,but also the shortage of mercury resources caused by the extensive use of mercury resources.Therefore,it is very important to develop a green mercury free catalyst for the production of PVC by acetylene process in China.At present,the research of substituting mercuric chloride catalysts is mainly divided into noble metal,non noble metal and non-metal catalysts.Among many alternative catalysts,nitrogen doped carbon catalyst has the advantages of low cost,simple preparation process,environmental protection,no pollution and good catalytic effect.Therefore,in this paper,CN_yprecursors were synthesized by a series ofpolymerizationreactions,includingparaformaldehyde,1,3,5-triethylbenzene and p-Phenylenediamine as carbon and nitrogen sources,and then prepared with cheap and readily available polyurethane foam sealant as precursors,and then prepared by nitrogen atmosphere and calcination at different temperatures.At the same time,the structure-activity relationship between the catalyst and acetylene hydrochlorination was characterized by diffraction of X-ray(XRD),X-ray photoelectron spectroscopy(XPS),physical adsorption and Thermal Gravimetric Analyzer(TG),and the deactivation mechanism of the catalyst was studied.The results show that the activity of the catalyst is the highest,the acetylene conversion is as high as 89.8%,and the selectivity of vinyl chloride is more than 99%.Only polyurethane foam sealant is the precursor catalyst,and the conversion rate is only 25.6%.Through characterization,it was found that the activity of the catalyst was related to the specific surface area,pore volume and pyrrole nitrogen content,and the carbon atom bound with pyrrole nitrogen atom was its active site.In a certain temperature range,the increase of calcination temperature can make the catalyst produce a large specific surface area and pore volume,and also increase the doping amount of n elements.Pyridine nitrogen also changes to pyrrole nitrogen to a certain extent,and the carbon deposition will be produced by prolonging the calcination time.The main reason for catalyst deactivation is carbon deposition.The preparation of N-doped carbon was also studied by ball milling and mechanical stirring.It was found that the catalytic effect of J-10%C₃N₄/AC/HNO₃catalyst prepared by using mechanical stirring method with 10%carbon nitride loading was the best,and its conversion rate could reach 50%without deactivation for 10 hours.