制备方法对 Ni-Al2 O3催化剂在 CO2-CH4重整反应中催化性能的影响

摘要

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NiAl2 O4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。%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.