Performance And Valence Adjustment Of Copper-Based Catalyst In Acetylene Hydrochlorination

Polyvinyl chloride（PVC）is China’s first and the world’s second largest general-purpose resin synthesis material,which is used in various industries,and its synthetic monomer is vinyl chloride（VCM）.Due to our unique energy structure,over 80%of the production capacity of vinyl chloride is synthesized using the calcium carbide acetylene method.However,the industrial catalyst（Hg Cl₂）of this existing production process is easily lost in the reaction,leading to environmental pollution and human health hazards.At the same time,under the constraints of the Minamata Convention and the"dual carbon goals",the industry needs a new type of catalyst that is green,environmentally friendly,efficient,and cost-effective to replace traditional catalysts.Compared to the expensive price of precious metal catalysts,non precious metal catalysts have great price advantage,but the activity of non-precious metal catalysts is still far from the conditions for industrial applications.Copper-based catalysts are considered to be the most suitable non-precious metal catalysts for acetylene hydrochlorination reaction,but there are still problems such as low catalytic activity and easy deactivation of the active component in the reaction.In this thesis,both aspects are considered in order to improve the performance of Cu-based catalysts for acetylene hydrochlorination as well as to protect the Cu valence state.This thesis conducts the following two parts of research:（1）Cu-NH₄Cl,Cu-2,2’-bpy and Cu-EDA complexes were loaded onto AC by a simple impregnation method,and then Cu-based catalysts containing Cu-N structures were prepared by calcination.The successful loading of Cu-NH₄Cl,Cu-2,2’-bpy and Cu-EDA complexes on AC was demonstrated by FTIR and XPS,and the generation of Cu-N structures as well as the observed change of Cu⁺content in the catalysts.The results of the evaluation experiments showed that the 5%Cu-NH₄Cl/AC 300℃catalyst was more active than 5%Cu/AC.The increase in activity of the 5%Cu-NH₄Cl/AC 300℃catalyst was caused by the increase in Cu-Nx bond content as well as the increase in Cu⁺content,which in turn enhanced the adsorption capacity of the 5%Cu-NH₄Cl/AC 300℃catalyst to the feed gas,thus enhance the catalyst activity.In contrast,the lower activity of 5%Cu-2,2’-bpy/AC catalyst and 5%Cu-EDA/AC catalyst than 5%Cu/AC was due to the decrease in specific surface area and change in pore structure of 5%Cu-2,2’-bpy/AC catalyst and 5%Cu-EDA/AC catalyst.（2）The initial activity of CuO-TiO₂ catalyst at 300℃was 9.7%when Cu was loaded onto different oxide supports through alkaline precipitation method at a reaction temperature of T=180℃,acetylene space velocity of 90 h^-1,and feed volume ratio of V（HCl/C₂H₂）=1.15.The activity of CuO-TiO₂ catalyst decreases with the increase of calcination temperature.By XRD analysis as the calcination temperature increases the carrier crystalline shape starts to transform,which is not conducive to the increase of acetylene conversion of the catalyst.Meanwhile,the comparison by XPS analysis proved that the oxygen vacancies in the TiO₂ carrier could regulate the valence state of Cu,but the acetylene conversion of the catalyst was very low.Therefore,in order to improve the acetylene conversion of the catalyst,the initial acetylene conversion of CuO/10%（AC-TiO₂）300℃catalyst was measured to be 23.73%by doping activated carbon into the carrier TiO₂ by ball milling method.The successful doping of activated carbon onto the TiO₂ carrier was demonstrated by characterization means.Also doping of the oxide carrier with uncharacteristic carbon can increase the catalyst activity,where the catalyst Cu/（SUC-TiO₂）（1:1）has the best activity with an initial acetylene conversion of 29.8%.