Boron Nitride Catalyst To Produce Vinyl Chloride From Acetylene And 1,2-Dichloroethane

Polyvinyl chloride?PVC?is one of the world's largest plastic raw materials,and its output is second only to polyethylene?PE?and polypropylene?PP?.PVC products are widely used in medical supplies,building materials,product packaging,electrical products and clothing products.In recent years,China's economy has been growing rapidly.People's demand has gradually increased,and the demand for PVC has also increased.At present,there are mainly three ways to prepare vinyl chloride monomer in industry,namely acetylene method,ethylene method and ethane method.Due to the natural conditions of more coal and less gas in China,acetylene method is mainly used in the production direction of vinyl chloride.With the further decline of oil prices in recent years,the combination of acetylene method and ethane method,namely the method of preparing vinyl chloride by direct catalytic conversion of acetylene and dichloroethane,that has gradually become the focus of researchers.Compared with acetylene method and ethane method,this method has the advantages of higher atomic economy and lower energy consumption.In order to solve the problems of high price of noble metal catalysts,poor catalytic activity and stability of non-noble metals,metal-free catalysts have become the main research direction of vinyl chloride preparation.This article mainly explores the reaction of metal-free catalysts for the preparation of vinyl chloride with acetylene and ethylene dichloride from the three aspects of catalyst carrier treatment,preparation of activated carbon-supported boron-doped carbon nitride catalyst and porous boron nitride catalyst using boron source.The physical and chemical properties of the catalyst were analyzed using nitrogen physical adsorption desorption?BET?,X-ray photoelectron spectroscopy?XPS?and other characterization methods.First of all,a variety of activated carbon-supported carbon nitride catalysts were prepared by treating coconut shell activated carbon and coal-based activated carbon in three ways:acid treatment,high temperature treatment,and no treatment,using urea as a precursor,and treated activated carbon as a carrier.After evaluating the micro-reaction device for preparing vinyl chloride using acetylene and ethylene dichloride,the catalyst found that the g-C₃N₄/YAC-2 catalyst prepared with coconut shell activated carbon treated with nitric acid had the highest reaction activity,and the highest acetylene conversion rate of the catalyst reached 83%,and the g-C₃N₄/YAC-3 catalyst prepared using high-temperature activated carbon has the lowest reactivity.The reason is that the surface area,pore volume and pore diameter of activated carbon treated with nitric acid are larger than those without activated carbon.It is conducive to the diffusion of the reactants inside the catalyst pores,and the surface of the catalyst prepared by the activated carbon treated with nitric acid has more defects,which is conducive to the acetylene hydrochlorination reaction step.In this paper,the performance of activated carbon-supported boron-doped carbon nitride catalysts prepared with boron compounds in the catalytic conversion of acetylene and dichloroethane to vinyl chloride was investigated.Through experiments,it is found that the catalyst prepared by using boric acid precursor is better than the catalyst prepared by sodium tetraphenylborate as the precursor,but the activity are both reduced compared to the g-C₃N₄/AC catalyst,because when the boron precursor doped,the pores of the prepared catalyst are blocked by boron species,which further reduces the mass transfer efficiency of the reactants in the catalyst.resulting in a decrease in reaction activity.That is why the activity of the catalyst decreases.In order to improve the activity of the catalyst for the acetylene hydrochlorination step in the reaction of acetylene and dichloroethane,a catalyst with more boron content needs to be prepared to increase the Lewis acid of the catalyst.Therefore,a variety of porous boron nitrides were prepared using boric acid and melamine After the evaluation test,the B₂N₃-1 catalyst has the highest acetylene conversion rate was 86%.It can be found that the catalyst can improve the conversion rate of the acetylene hydrochlorination step in the reaction,and the catalyst also has a high space-time yield indicates that the active site density of the catalyst is significantly higher than that of the supported catalyst.