Electrocatalytic Selective Oxidation Of C-H Bonds Of Methane And Para-xylene

Methane is one of the most abundant fossil energy sources in nature.In recent years,a large amount of shale gas and combustible ice have been proved.However,methane is gaseous at normal temperature and pressure,dfficult to liquefy,and difficult to store and transport.At present,it is mainly used as primary energy for direct combustion,and the chemical value of CH4 as a natural resource has not been utilized.Methanol is an important bulk chemical raw material that can be used to prepare a variety of chemicals with high energy density and easy storage and transportation.At present,industrial methane to methanol is mainly prepared by syngas,that is,the methane C-H bond is completely broken into a synthesis gas(CO,H2)by a high temperature process,and then CH3OH is produced by CO and H2 through a high pressure process.The synthesis gas produces methanol,which is not only complicated and expensive,but also has high energy consumption in the gasification process,and the economy needs to be improved.In theory,the electrochemical synthesis method can directly convert CH4 into important chemicals such as CH3OH and HCOOH under normal temperature and pressure.In addition,compared with the traditional method,the electrochemical process is easy to control,and the electric energy required for the reaction can be taken from the wind energy and the solar energy in situ,and the equipment is simple and convenient for field production.This paper mainly studies the reaction of methane electrocatalytic conversion to methanol at normal temperature and pressure.The reaction is carried out in a mobile phase gas diffusion electrode reactor designed by ourselves.The gas diffusion electrode reactor can effectively ensure the gas-liquid-solid(CH4-catalyst-electrolyte)three-phase system is fully contacted,and overcomes the difficulty that the conventional electrocatalytic reactor is difficult to contact the catalytic electrode because the CH4 is insoluble in the electrolyte.During the CH4 anodic conversion experiments,the production of methanol was found to be related to the presence of OH-and Cl-in the electrolyte by changing the electrolyte.It was found that iron-containing catalysts such as Fe2O3,Na3Fe3(PO4)3 and FeNC have good catalytic activity for electrocatalytic conversion of CH4.When Na3Fe3(PO4)3 is used as catalyst,the single-pass conversion of methane at normal temperature and pressure reaches 0.25%,the selectivity of methanol reached 33%.A nano-sized Au-Pd/CNT catalyst was synthesized,and the single-pass conversion of methane reached 0.32%and the selectivity of methanol reached 36%at normal temperature and pressure.During the CH4 cathodic conversion experiment,when V2O5/CMK-3-N was used as the catalyst,the single-pass conversion of methane reached 0.23%and the selectivity of methanol reached 45%at normal temperature and pressure,and no CO2 was produced during the reaction.CMK-3-N(nitrogern-doped mesoporous carbon)in V2O5/CMK-3-N can effectively increase methanol production,and V2O5 in V2O5/CMK-3-N can inhibit methanol peroxidation to form formic acid.It was confirmed that the addition of a low concentration of H2O2 to the electrolyte during CH4 cathodic conversion facilitated methanol production.In addition,we also use a titanium-based metal oxide as an anode for electrocatalytic oxidation of p-xylene in a conventional glass double electrolytic cell,as an exploration of electrocatalytic C-H bond activation,and also provide a scientific basis for the catalyst design of methane C-H activation.