Study On Catalytic Methane Gas Sensor With Cobalt Oxide Loaded

With the development of society,the whole globe has been facing more and more serious environmental problems and the shortage of fossil energy.Natural gas used as fuel possesses various advantages,such as abundant reserves,low cost,small pollution,etc,and it is widely used in production and life.While bringing convenience to people,the combustible and explosive nature of natural gas brings security problems in the use and transportation.In recent years,the safety accidents caused by gas leakage threaten people's life and property.The main component of natural gas is methane,so it is important to develop sensitive and reliable methane gas sensors.At present,catalytic combustion type of methane sensor is the most widely used methane sensor,and its core is the catalyst sensitive material with high catalytic activity.It is very important to prepare methane sensor and discuss its application in methane detection.In this thesis,cerium oxide,zirconium oxide,aluminum oxide as the support,a series of catalysts were prepared by impregnation method loaded with different amount of cobalt oxide,and the effects of the amount of cobalt oxide loaded,support and operating temperature on the properties of catalytic combustion was studied.On the basis of the catalyst research,the research of sensors is carried out.The main conclusions are as follows:The amount of cobalt oxide loaded and support type have significant influence on the performance of catalyst.Co-Ce catalysts showed better catalytic activity of methane,and its catalytic efficiency increased first and then decreased with the increase of cobalt oxide loaded.In the long working period,the thermal stability of the catalyst was poor because of the easy sintering of the catalyst.BET,XRD,H₂-TPR characterization results showed that the Co-Ce catalysts had small specific surface area,large grain size,but the reduction temperature of surface oxygen species was far lower than the Co-Zr and Co-Al catalysts.XPS characterization results showed that there were interaction between cobalt oxide and cerium oxide,promoting the conversion of Co²⁺to Co³⁺,increasing the content of Co³⁺on the surface of catalyst,and Co³⁺was more easily reduced than Co²⁺.Interaction also increased the content of lattice oxygen of the catalyst,and lattice oxygen was an important participant in the reaction.The catalytic activity of Co-Zr and Co-Al catalysts were relatively low,but they showed good thermal stability.The results showed that the reduction temperatures of surface oxygen species of Co-Zr and Co-Al catalysts was higher than the Co-Ce catalysts,they were harder to reduce.The effect of high temperature on the surface oxygen species was small,so the thermal stability was better.There were also interaction between cobalt oxide and supports,increasing the surface Co³⁺content and lattice oxygen content of catalysts.The methane sensors had good linearity,stability,repeatability and selectivity.Among them,30Co-Ce and 30Co-Zr sensors had large response to methane and were more sensitive to methane.30Co-Zr sensor also had high response to carbon monoxide,CO-TPR characterization showed that 30Co-Zr catalyst for carbon monoxide had good reducibility,hence Co-Zr catalyst also has the feasibility of the application in carbon monoxide sensors.