Preparation Of Heteroatom N Modified Multiporous Carbon Materials And Catalytic Hydrochlorination Of Acetylene

In the traditional coal（chlor-alkali）industry,acetylene hydrochlorination is a very important reaction in the production of polyvinyl chloride polymer materials.At present,due to the volatility and high toxicity of mercuric chloride catalysts used in the reaction industry,it is urgent to develop mercury-free catalysts,and green non-metal catalysts are one of the best substitutes for mercury catalysts.In order to overcome the problems of uniform surface charge distribution,stable structure and low catalytic activity of commercial activated carbon（AC）,a series of C-N nonmetal catalysts were synthesized by heat treatment of precursors containing nitrogen,and the effects of nitrogen doping,defect sites,specific surface area,highly electronegative atoms,rich functional groups containingπat active sites and multistage pore structure on the hydrochlorination of acetylene were studied.（1）Firstly,non-metallic hollow carbon nanospheres（PACP-T）with multistage pore structure were synthesized using aniline and pyrrole as raw materials by self-template method.Compared with the reference AC catalyst（55%）,the conversion of acetylene under the action of PACP-800 catalyst is 84%,and the catalytic performance is obviously improved.Modification of carbon materials by heteroatoms is beneficial to the construction of active sites,which can further change the structure of the materials and make the active sites disperse atomically.In addition,characterization and DFT calculations show that pyridinic N⁺O^-is probably the most effective site for the catalytic activity of the catalyst,and its excellent activity derives from the highly electronegative heteroatoms and the rich functional groups containingπ（C=C,N=N,aromatic ring,and pyridinic N⁺O^-）,which promote the rapid reaction of the reactants and inhibit the carbon deposition on the surface,thus promoting the continuous exposure of the active sites.The activity and stability of the optimized PACP-800 catalyst were improved significantly,which promoted its potential industrial application.（2）Based on the idea that rich nitrogen content and multistage pore structure help to improve catalytic activity,we further improved the stability of non-metallic catalysts by increasing nitrogen content in feedstock and introducing template to control the synthesis of multistage pore structure carbon materials.Using silica sol as template,phenol,melamine and formaldehyde as C source and N source respectively,melamine-phenolic-formaldehyde（MPF）resin rich in pyridinic N and pyrrolic N and porous C-N material rich in defective sites were synthesized by in-situ heat treatment.Compared with the reference AC catalyst（55%）,the acetylene conversion of 86%can be reached over MPF-800 catalyst,and the catalytic performance is obviously improved.In addition,the long-term stability of the catalyst showed that the conversion of C₂H₂remained at 70%,the inactivation rate was 0.08%h^-1,and the selectivity of vinyl chloride was higher than99%after 200 h reaction.The results of characterization analysis and theoretical calculation show that the carbon-nitrogen materials with abundant multistage pores and local C-N active sites were constructed by the incorporation of heteratomic groups.Due to the high electronegativity of the defective sites and the synergistic interaction between pyridine N and the functional groups containingπ（C=C,triazine ring,etc.）,the acetylene and hydrogen chloride molecules are balanced and activated.In addition,the strong interaction between heteroatom sites and metal species also makes MPF-800 a good metal catalyst carrier,which solves the problem of AC catalytic acetylene hydrochlorination.（3）From the perspective of waste utilization and cost reduction to further improve the economy of non-metallic catalysts,nitrogen-doped carbon catalysts were successfully prepared by using the waste peanut meal（PM）as precursor in the process of peanut oil extraction by a simple carbonization process and used for catalytic acetylene hydrochlorination.Firstly,the PMC catalysts synthesized from biomass were studied by changing a single variable.The morphology of PMC and PMC-1D-500 was analyzed by SEM,and it was found that PMC was composed of relatively smooth block structure.After activation,PMC-1D-500 had abundant pore structure,which proved the importance of activator to pore formation.XPS analysis showed that a large number ofπ-containing functional groups（C=O,O=C-O and phenol-C-OH）and small molecular structures of nitrogen species in the catalysts enhanced the adsorption and activation of acetylene and hydrogen chloride.In addition,the long-term stability test of the catalyst showed that after 100 h of reaction,the conversion rate of C₂H₂ was still 91%,the inactivation rate was 0.06%h^-1,and the selectivity of vinyl chloride was always higher than 99%.