Investigation On Hydrogen Catalytic Combustion Performance At Low Temperature Based On Modified Pt/ZSM-5/Cordierite

The depletion of fossil energy and the prominent environmental problems such as the greenhouse effect promote the transformation of global energy economy.Hydrogen is clean and has high energy density,which make it a key energy for the transformation of society to a low carbon economy.Comparing two main application forms of hydrogen,the low temperature hydrogen catalytic combustion technology is more safe and controllable than the traditional flame combustion,so it becomes the key technology to realize hydrogen economy.The most effective catalyst for hydrogen catalytic combustion is Pt,but the high price of Pt limits its wide application in industry,which hinders the popularization of hydrogen energy in the future society.Therefore,it is urgent to reduce the cost of noble metal based hydrogen catalyst.The most direct way to reduce catalyst cost is to use less or no noble metal.However,in view of the fact that the catalytic performance of Pt active component is irreplaceable,what’s more,it is impossible to ignite hydrogen combustion at room temperature without noble metals within the current technical scope.Thus,the main objective of this paper is to maintain better catalyst activity and stability with less noble metals.In order to achieve this goal,this paper mainly focuses on two aspects,on the one hand,the research trying to study the catalytic performance of hydrogen at low temperature by changing the support;on the other hand,we focus on introducing non noble metal elements to modify the Pt active components.In the aspect of support,molecular sieve with large specific surface area and good hydrothermal stability was used as the carrier of active component.Combined with cordierite matrix which has high mechanical strength and high thermal conductivity.We observed the low temperature hydrogen catalytic performance of such combined catalysts considering various properties of molecular sieves.As for active components,several common transition metals were introduced to modify the properties of Pt,and their hydrogen catalytic performance at low temperature was discussed.The main research work of this paper is as follows:（1）In order to monitoring the real-time hydrogen conversion at different temperatures,a low-temperature hydrogen catalytic performance test platform was built.Moreover,we have mastered the appropriate preparation and coating methods of catalyst,explored the best proportion of materials,and ensured that the catalytic coating is firm and does not fall off.In a word,we have prepared better catalyst by relatively simple and traditional means.（2）Pt/ZSM-5/cordierite,Pt/Al₂O₃/cordierite,Pt/Ti O₂/cordierite and Pt/Si O₂/cordierite catalysts were prepared,according to performance test and characterization analysis,it is found that the well-developed pore structure and large specific surface area of ZSM-5 are beneficial to the adsorption and dispersion of active Pt,more channels are also conducive to the adsorption of hydrogen and oxygen,which makes the catalyst show better catalytic performance.（3）It was found that the Pt/ZSM-5/cordierite catalyst with 0.05g/L Pt loading could ignite the reaction at room temperature.Whiling the same catalyst with 0.01g/L Pt loading can not realize room temperature ignition,therefore,many improvements were carried out in order to improve the activity of the catalyst with this ultra-low noble metal loading.（4）Taking the catalysts supported on different types of molecular sieves as the research object,it is found that these zeolites with different pore structure have little effect on the low temperature hydrogen catalytic combustion,all catalyst performed well.Moreover,the performance of monolithic catalyst with zeolite as coating carrier is related to the acidity of zeolite.Lastly,the introduction of K⁺,Na⁺and other cations in zeolite can improve the performance of catalyst to a certain extent.（5）The Pt-M（M=Ce,Co,Fe,Cu,Mn）/ZSM-5/cordierite catalyst modified by different transition metals was prepared and compared.The results showed that Pt-Cu/ZSM-5/cordierite had the best performance.At the ultra-low Pt loading of 0.01g/L,the Cu modified catalyst could converse 10%H₂ at 58.5℃in 2.5vol%hydrogen air gas mixture atmosphere and achieve completely H₂convertion at 100℃,and the catalyst activation energy is as low as 44k J/mol.（6）The first-order kinetic model of hydrogen global catalytic reaction was used to describe the kinetic behavior of non noble metal modified catalyst.It was found that the model could simulate the catalytic kinetic reaction accurately,and the fitted Arrhenius curve had a high correlation with the measured data.In the research,we have a clear mathematical description of the catalytic reaction behavior to guide the design of related catalysts.