The Research Of Oxidation Of Low-Concentration Methane To Methanol On Ni/BiOCl Catalysts

At present,with the development of global industrialization,energy and environmental problems are becoming increasingly prominent.As a kind of clean energy with abundant reserves,methane has attracted people’s attention.However,due to the limitation of fossil energy exploitation and transportation conditions,a large number of low-concentration methane will be produced,resulting in resource waste and environmental pollution.Therefore,it is of great significance and broad application prospect to develop a green and efficient catalytic system for catalytic oxidation of low concentration methane to methanol.However,methane molecules are difficult to activate and intermediates and methanol products are easy to be over-oxidized,which makes the core of this research to develop high-performance catalysts.In the field of partial oxidation of methane,nickel metal catalyst stands out in the catalytic oxidation of methane to methanol because of its excellent C-H bond breaking ability and easy migration of surface substances.In this paper,a series of Ni/BiOCl catalysts were prepared by means of hydrothermal synthesis.Then,different amounts of nickel were loaded on the BiOCl support by impregnation method,which made the surface lattice of the support shrink and produce oxygen vacancy.The physicochemical properties of the catalyst were characterized by TEM,XRD,ICP-AES,EPR,Raman,TG-DTG,FTIR,XPS and other characterization methods.The results show that Ni loading can elongate the metal-oxygen bond on the nano-layer BiOCl support,and increase the oxygen vacancy content from 6.52%to 28.08%.The methanol yield increased to 39.07 μmol/(gcat·h),indicating that the methanol yield was closely related to the concentration of oxygen vacancy on the catalyst surface.The morphology of the support has an important impact on the performance of the catalyst.In order to furher improve the performance of the catalyst,based on the previous study of nano-lamellar catalyst,the paper synthesized the nano-flower-like BiOCl support by hydrothermal synthesis,and carried out in-depth exploration.When Ni is loaded on the nano-flower-like BiOCl,the surface of the nano-flower-like BiOCl is mainly exposed to(010)crystal surface,and Ni atoms enter the wider surface lattice to induce oxygen vacancy content to further increase to 34.29%,thus showing better catalytic activity.The methanol yield of 74.05 μmol/(gcat·h)was achieved.In addition,the catalytic mechanism of partial oxidation of low concentration methane to methanol in gas phase was revealed by using the characterization technique In situ DRIFT.The catalytic activity of Ni/BiOCl to produce methanol from methane with low concentration is positively correlated with the concentration of oxygen vacancy in the catalyst.The activated oxygen adsorbed by oxygen vacancy in the catalyst preferentially activates methane molecules adsorbed by nearby metal atoms,thus producing isolated hydroxyl,which then reacts with methyl adsorbed by nearby metal to form methanol molecules.