Carbon Surface Chemical Regulation Investigations on Non-mercury Catalysts of Acetylene Hydrochlorination

Author:Wang Bai Lin

Supervisor:li xiao nian zhao jia


Degree Year:2019





The interface properties of carbon materials have important theoretical and practical significance for the design and development of catalysts.Gold-and non-metallic catalysts supported on carbon-based materials are widely used in many catalytic reactions.However,the complex oxygen-containing and nitrogen-containing functional groups on the surface of carbon materials which limit understanding of the physical and chemical properties of different functional groups on the carbon surface,and also hinder the study of the reaction mechanism of carbon-based catalysts in heterogeneous reaction.In addition,the green preparation process,stable chemical state and low cost cationic non-mercury catalysts are important directions for the sustainable development of catalysts.In the production of vinyl chloride by acetylene hydrochlorination,non-mercury catalysts are considered as the most promising substitutes for mercury-based catalyst.Therefore the design and development of non-mercury catalysts have important research significance.In this dissertation,the activation of gold-based catalysts,the regulation of the surface chemical properties of carbon carriers and the reaction mechanism of nitrogen-doped carbon catalysts were studied.Firstly,the activation mechanism of gold catalysts.Serious environmental pollution and ecological hazards can be produced during the preparation of gold-based catalysts with aqua regia as solvent.The gold catalyst prepared by water has poor catalytic performance due to its poor metal dispersion and unstable active species.In this dissertation,a greener preparation technology with organic aqua regia was used to activate gold catalysts prepared with water.The activated gold catalyst explored efficient catalytic performance.This dissertation reveals that sulfur and nitrogen species in organic aqua regia could oxidize and anchor cationic gold species during activation.Secondly,the regulation of surface chemical properties of carbon carriers.The industrialized development of gold-based catalysts is constrained by their high cost of preparation.In this dissertation,the single-atom gold catalysts were successfully prepared by introducing carbonyl groups on the surface of the support through the strong interaction between carbonyl groups and gold species(-318.1 kJ·mol-1),which reduced the high preparation cost of gold catalysts.At the same time,we found that the functional groups on the carbon surface could be selectively regulated by introducing sulfur species in the above research process.Detailed experiments and characterization results show that introduction of sulfur species occupied the pyridinic nitrogen formation site on carbon surface,inhibited the conversion of pyrrolic N to pyridinic N,thereby,successfully prepared carbon-based materials with a single functional species.Thirdly,the reaction mechanism of nitrogen-doped carbon catalysts was studied.In this dissertation,the reaction mechanism of nitrogen-doped carbon catalysts was systematically studied on carbon-based materials with different functional groups.The active sites and reaction mechanism in the reaction process were also revealed.The results show that the reaction mechanism depends on the form of functional groups.When there is only one functional group on the surface of carbon materials(pyrrolic-or pyridinic N),the reaction follows the Eley–Rideal(ER).However,mixed nitrogen functional groups are presented on the carbon surface,the reaction follows the Langmuir-Hinshelwood(L-H)mechanism,and with the reaction gradually deactivated,the reaction mechanism changes from L-H mechanism to E-R mechanism with pyrrolic N as the active site.In summary,the selective regulation of carbon surface functional groups has a significant impact on the design and application of catalytic active sites.Reasonable regulation and understanding the chemical properties of different functional groups on carbon surface are of great theoretical significance for further optimization and development of carbon-based catalysts.