制备方法对 Ni-Al2O3催化剂在 CO2-CH4重整反应中 催化性能的影响

为提高镍基催化剂的干法重整活性,采用溶液燃烧法、等体积浸渍法、胶体磨循环浸渍法和水热-沉积法制备了SCM、IMP、T310和HTP四种催化剂,在800 ℃考察了其在CO₂-CH₄重整反应中的催化性能,并结合ICP-AES、N₂吸附-脱附、XRD、H₂-TPR和TEM等表征手段对催化剂进行分析。结果表明,水热-沉积法和胶体磨循环浸渍法制备的催化剂比表面积较大,分别为190.83和182.21 m²/g,可为反应提供较多的接触面积,进而提高催化剂的初始活性(HTP试样CH₄和CO₂初始转化率相对较高,分别达85.15%和90.84%);而溶液燃烧法和等体积浸渍法制备的催化剂具有较多的NiAl₂O₄尖晶石,其还原峰面积占总还原峰面积90%以上,还原后可获得更多晶粒粒径更小的稳定活性组分Ni(SCM和IMP试样稳定性更好,反应50 h后活性超过HTP和T310试样,100 h后CH₄转化率方降至50%以下)。因此,决定催化剂稳定活性的更重要的因素应该是活性组分Ni晶粒粒径的大小及其抗烧结能力的强弱。

Effect of preparation methods on the catalytic performance of Ni-Al2 O3 for CO2-CH4 reforming

To investigate the catalytic performance of nickel-based catalysts for carbon dioxide reforming of methane, four samples, SCM, IMP, T310 and HTP, with same contents of Ni were prepared by solution combustion method, incipient-wetness impregnation method, colloid mill circulating impregnation method and hydrothermal-precipitation method. The catalytic performance was tested at 800 ℃. The samples were characterized with ICP-AES, N₂ absorption-desorption method, XRD, H₂-TPR and TEM techniques. It was shown that the preparation methods had significant effects on the catalytic performance. The HTP and T310 samples had larger specific surface area, 190.83 m²/g and 182.21 m²/g respectively, which could provide more active sites and improve the activity (the initial conversion of CH₄ and CO₂ of HTP was up to 85.15% and 90.84%). The reduction peak area of NiAl₂O₄ of the catalysts prepared by solution combustion method and incipient-wetness impregnation method was higher than 90% of the total reduction area, indicating that these catalysts had more small Ni size particles and better stability after reduction (the conversion of CH₄ for SCM and IMP was higher than that of HTP and T310 after 50 h experiment, and was up to 50% after 100 h reaction). Hence, the mojor reason for improving the activity and stability of catalyst would be the size of Ni particles and its resistance to sintering.