Preparation, Characterization And Performance Of MgO-doped Mesoporous Ni/MAS-24 Catalysts In CH₄/CO₂ Reforming Reaction

With the burnout of coal and crude oil reserves,the requirement of obtain energy is increasing,especially for the countries having no technology to replace the energy generation;meanwhile,the emission of greenhouse gas from burning fossil fuels makes the trend of global warming intensifies gradually.Therefore,the development and utilization of environmentally-friendly new energy has become one of the most important challenges for the scientific and industrial community.Hydrogen energy is favored by the characteristics of high efficiency and clean,and the natural gas（CH₄）possess the advantages of large reserves,high H/C ratio,less CO₂ generated from methane combustion,which makes it an excellent raw material for the production of hydrogen.In the conversion and utilization of natural gas,the CO₂ reforming of CH₄ has attracted a wide range of research interests due to its reduction and effective utilization of greenhouse gases（CH₄ and CO₂）.In our work,mesoporous alumino-silicate（MAS-24）material with microporous ZSM-5 structure was synthesized from ZSM-5 nano-clusters and used as support of catalyst for CO₂/CH₄ reforming reaction,which possessed strong acidity,large specific surface areas and high hydrothermal stability.A series of 0-12 wt%MgO-10wt%Ni/MAS-24 were prepared via the sol-gel method and characterized by X-ray diffraction（XRD）,N₂ adsorption analysis（BET）,Fourier transform IR（FT-IR）,temperature-programmed reduction of H₂（H₂-TPR）,temperature-programmed desorption of CO₂（CO₂-TPD）,UV-Vis diffuse reflection spectroscopy（UV-DRS）,thermo-gravimetric/differential scanning calorimetry（TG/DSC）and high resolution transmission electron microscope（HRTEM）techniques.In the meantime,the effects of different MgO loadings and different reaction temperatures on the catalytic performance in catalyst performance of CO₂/CH₄ reforming were studied in detail.The catalytic performance of catalysts for CO₂ reforming of CH₄ was evaluated under the operating conditions of 700 oC,1 atm,CH₄/CO₂ = 1,GHSV = 24 L·gcat-1·h-1.The results indicated that the 9wt%MgO-10Ni/MAS-24 exhibited the best catalytic activity and stability,the conversion of CH₄ and CO₂ on the catalyst reached the maximum,which was 79% and 93%,respectively.The investigation in catalytic stability of 9wt%MgO-10Ni/MAS-24 for 60 h indicated that the conversion of CH₄ and CO₂ maintained 93% and 99%,respectively,the selectivity of H₂ and CO for100% at 800 oC within 30 h although the conversion of CH₄ decreased to 83% in the later 30 h due to the high dispersion of Ni active particles via synergistic action between MgO and NiO nano-particles as well as the effect of catalyst surface,which would prevent Ni0 active particles from aggregating and formation of coke on sites during the CH₄/CO₂ reforming reaction.