Preparation Of Supported Iridium-based Catalyst And Study On Its Catalytic Combustion Performance Of Low-concentration Methan

Natural gas has become a highly promising clean energy source due to its abundant reserves,high calorific value,and other advantages.Methane,as the main component of natural gas,has a greenhouse effect 28 to 34 times that of CO₂.A large amount of low concentration methane（<0.75%）,which is difficult to enrich and reuse in the processes of natural gas vehicle exhaust purification,exhaust gas,and oilfield associated gas treatment,is usually directly discharged into the atmosphere,causing huge waste of hidden energy and serious greenhouse effect.The high structural symmetry of non-polar methane molecules makes it difficult to activate C-H bonds under mild conditions.Catalytic combustion,as an efficient and environmentally friendly low concentration methane purification technology,can effectively avoid the environmental pollution caused by direct high-temperature combustion of methane,and is of great significance for the treatment of mine gas and industrial waste gas.Ir O₂has great potential for application in low-temperature catalytic combustion of methane due to its efficient dissociation of C-H bonds in CH₄.The regulation of metal metal oxide interface interaction is an important way to develop efficient nano catalysts.This paper investigates the structure activity relationship of iridium based catalysts in methane catalytic combustion through the synthesis of supported single metal iridium catalysts and their bimetallic iridium platinum catalyst systems,providing theoretical guidance for the design and preparation of efficient iridium based catalysts.The main contents of the research are as follows:1.Ir/TiO₂catalysts were prepared using TiO₂nanocrystals with different morphologies preferentially exposed to（101）,（100）,and（001）crystal planes as carriers.It was found that the methane catalytic combustion performance of different Ir/TiO₂catalysts was significantly dependent on the TiO₂crystal planes.Firstly,TiO₂nanocrystals with main exposed crystal planes of（100）,（101）,and（001）were prepared,and the noble metal iridium was loaded onto the TiO₂carrier through wet impregnation to synthesize three types of supported Ir/TiO₂catalysts.Then,the methane combustion performance of the obtained catalyst was tested.The test results showed that the Ir/TiO₂catalyst subjected to reduction treatment at different temperatures exhibited the optimal methane catalytic combustion activity at 400°C,and Ir/TiO₂（100）-400>Ir/TiO₂（101）-400>Ir/TiO₂（001）-400.The research results indicate that the methane catalytic combustion activity of Ir/TiO2 is closely related to the surface Ir0 concentration and defect oxygen vacancies dependent on the TiO₂crystal surface.Ir-TiO₂（100）catalyst has a higher surface Ir⁰concentration,generates more defect oxygen vacancies,and has good redox ability,greatly promoting the activation of methane,thereby improving its methane catalytic combustion performance.Ir-TiO₂（100）catalyst has generates more defect oxygen vacancies,and has good redox ability,greatly promoting the activation of methane,thereby improving its methane catalytic combustion performance.2.Supported bimetallic catalysts with different Ir:Pt ratios were synthesized by impregnation method using commercial titanium dioxide as the carrier,including Ir Pt_0.25/TiO₂,Ir Pt_0.5/TiO₂,Ir Pt₁/TiO₂,and Ir/TiO₂,Pt/TiO₂catalysts.Then,the methane catalytic combustion performance of the obtained catalyst was evaluated.The research results show that Ir Pt_0.5/TiO₂has excellent methane catalytic combustion activity compared to other catalysts,and the methane conversion efficiency reaches100%at 325°C.Meanwhile,Ir Pt_0.5/TiO₂exhibits excellent thermal stability at 350°C for up to 200 hours,and exhibits excellent sulfur resistance on the surface at 320°C and 350°C for up to 30 hours.The characterization of the system combined with DFT theoretical calculations revealed that the addition of Pt components to Ir catalysts induced the formation and stability of electron rich Ir species through strong electron interactions between Ir Pt.The electron rich Ir structure has more defect oxygen vacancies and better oxidation-reduction ability,greatly promoting the adsorption and activation of O₂,while effectively suppressing the adsorption of SO₂on the catalyst surface,resulting in better low-temperature methane catalytic activity and excellent sulfur resistance of the Ir Pt_0.5/TiO₂catalyst.