The Research On Catalytic Oxidation Of Low-concentration Methane By Cu-based Zeolite

Huge amounts of low-concentration methane have been produced by natural resources such as natural gas,shale gas,and coalbed methane.Due to its low energy density,the utilization rate of low-concentration methane was low.And the treatment method of direct emission will aggravate the greenhouse effect.Therefore,how to use these low-concentration methane was still a hot and difficult research topic in the world.Among the many ways of methane conversion and utilization,methanol is an ideal conversion product because of its cleanliness,economy,convenience of storage and transportation,and excellent hydrogen carrier.In this paper,the direct oxidation of low-concentration methane to methanol was studied systematically in the reaction system of O₂ and H₂O with metal-supported H-MOR（mordenite）zeolite as a catalyst under atmospheric pressure.The main research contents and conclusions are as follows:Firstly,the monometallic Cu-MOR catalyst was prepared.The Cu_0.50-MOR showed good catalytic activity for the catalytic oxidation of low-concentration methane to methanol in the gas phase,and the methanol yield was 57.54μmol·g^-1·h^-1.It was confirmed that the main form of Cu in the catalyst was copper bivalent.After three cycles,the activity of the catalyst decreased significantly from 57.54 to 32.50μmol·g^-1·h^-1.The results of electron microscope showed that the structure collapse and metal sintering agglomeration of the catalyst were serious after three cycles.Later,to improve the anti-sintering force capability of the catalyst,the Cu Zn-MOR catalysts were prepared through the co-impregnation method.The effect of Zn on the reaction oxidation of low-concentration methane to methanol was systematically investigated.The experimental results showed that the catalytic activity of the bimetallic Cu_0.50Zn_0.35-MOR was best and the methanol yield was 71.35μmol·g^-1·h^-1.After three cycles of test experiments,the Cu_0.50Zn_0.35-MOR catalyst still showed good catalytic activity,indicating that the catalyst has good hydrothermal stability.In addition,the performance test results indicated that the main activity in the catalyst was derived from Cu.XRD,N₂-physisorption,SEM,TEM,and EDX mapping proved that the introduction of Zn enhanced the dispersion of Cu on the MOR carrier and prevented the agglomeration and sintering of Cu sites.H₂-TPR,²⁷Al MAS NMR,XPS,DR UV-Vis,and CH₄-TPD showed that there was electron transfer interaction between Cu and Zn,which changed the amount of octahedral coordination extra framework aluminum（EFAl）and thus affected the distribution of Cu on the H-MOR framework.These findings also provide feasible guidelines for future structural optimization of Cu-based catalysts for low concentration methane direct oxidation to methanol reactions.Figure 30 Table 8 Reference 115...