Novel Catalytic Pathways For The Production Of Vinyl Chloride Monomer And Analysis Of The Structure-activity Relationship

Based on the development of the green catalytic process,this paper develops two green catalytic pathways for the production of vinyl chloride monomer using activated carbon-supported carbon nitride as the catalyst for the disadvantages of current methods for the production of vinyl chloride monomer.The structural changes of activated carbon-supported carbon nitride during the synthesis process were studied,and the influences of the structural changes on the activity for dehydrochloriantion of 1,2-DCE and direct conversion of dichloroethane and acetylene were also studied.Combined with various characterization techniques and theoretical calculation methods,the structure-activity relationship of activated carbon supported carbon nitride in these reactions was proposed.In addition,from the perspective of environmentally friendly and sustainability,the synthesis of the Au/C catalyst,which is currently the most likely alternative to the acetylene hydrochlorination mercury-based catalyst,has been improved.A synthesis method for a more environmentally friendly Au/C catalyst has been developed.The content of this paper mainly includes the following three parts.1: Supported Structure-Controlled Graphitic Carbon Nitride Catalyst for Dehydrochlorination of 1,2-DichloroethanePyrolysis of dichloroethane is an important reaction for the production of vinyl chloride monomer.The high operating temperature and the low efficiency are,however,nuisances for this process.In this manuscript,a supported structure-controlled graphitic carbon nitride is reported as a highly efficient catalyst for dehydrochlorination of 1,2-dichloroethane(1,2-DCE).The results indicate that the “defects” of the active component,i.e.,the chain terminations of the carbon nitride,which tend to form at low synthesis temperature of the catalyst,show high catalytic activities for the dehydrochlorination of 1,2-dichloroethane,while for the high degree of polymerizations of the carbon nitride,which tend to build at high synthesis temperature,relatively low activities for the reaction can be found.These findings highlight the role of the “defects”,i.e.,chain terminations,of the material for the reaction and also provide a strategy for the selective synthesis of highly active N-doped carbon catalysts for this reaction.2: Direct Conversion of Acetylene and 1,2-Dichloroethane to Vinyl Chloride Monomer over a Supported Carbon Nitride Catalyst: Tunable Activity Controlled by the Synthesis TemperatureA carbon supported carbon nitride is reported here as a catalyst for the direct conversion of acetylene and 1,2-dichloroethane(EDC)to vinyl chloride monomer(VCM).We demonstrate that increasing the synthesis temperature of the carbon nitride material leads to a catalyst with higher catalytic activity towards VCM production.The catalysts were characterized by acetylene temperature-programmed desorption,X-ray photoelectron spectroscopy,high-resolution TEM,Electron Energy Loss Spectroscopy(EELs)and computational methods,showing that the improved activity for the catalysts can be ascribed to both the higher proportion of pyridinic N and the more positive lowest unoccupied molecular orbital(LUMO)of the catalyst,resulting from the increased degree of polymerization of carbon nitride.These findings highlight the role of polymerization conditions in increasing the catalytic activity of carbon nitride catalysts and provide a strategy for the selective synthesis of highly active carbon nitride catalysts for the one-step synthesis of VCM from acetylene and EDC.3: A Facile Synthesis of Highly Active Single Site Au/C Catalysts for Acetylene HydrochlorinationTraditional methods for the preparation of single-site Au/C catalysts for acetylene hydrochlorination typically require harsh solvents in order to stabilize oxidised gold species.Herein,we report a simple and effective method to produce atomically dispersed Au/C catalysts using low polarity solvents with low boiling points such as acetone,in contrast to the previously used aggressive acidic and oxidizing solvents such as aqua regia.When tested for the acetylene hydrochlorination reaction,these new catalysts perform comparably in terms of conversion and stability for acetylene hydrochlorination,whilst still maintaining high selectivity to the vinyl chloride monomer.Using a combination of X-ray absorption spectroscopy,X-ray diffraction and high angle annular dark field scanning transmission electron microscopy,we show that these catalysts consist of atomically dispersed cationic Au species,despite being prepared in the absence of highly oxidising acidic solvents.This provides a facile strategy to produce highly active Au/C catalysts for the production of VCM in addition to facilitating further studies concerning the activity of single site Au/C catalysts.