采用水解–沉积法,在不同焙烧温度下制备了cat-500、cat-600、cat-700和cat-800系列NiO/γ-Al2O3催化剂.XRD和H2-TPR分析表明,焙烧温度高于700℃,活性组分与载体具有强烈的金属-载体相互作用(SMSI),具体表现为活性组分前驱体以尖晶石NiAl2O4的形式存在.反应后催化剂的XRD、TG-DTG、TPH等表征结果表明,cat-700和cat-800试样的Ni晶粒尺寸分别为9.8和8.7 nm,小于cat-500和cat-600试样(分别为15.7和13.6 nm),分散性更好;且催化剂表面积炭为丝状碳,其不会导致催化剂失活,但大量积累会引起床层压降升高,影响催化剂的反应性能.cat-800试样110 h寿命试验表明,高温焙烧制备的Ni基催化剂活性和稳定性均较高,CO2转化率达95%左右,失活速率仅为0.0536%/h.
A series of NiO/γ-Al2O3 catalysts for CH4/CO2 reforming were prepared by altering calcination tem-perature using hydrolysis-deposition method, and recorded as cat-500, cat-600, cat-700, and cat-800 according to the calcination temperature. XRD and H2-TPR results showed that there was a strong metal-support interaction (SMSI) in the form of NiAl2O4 spinel in the prepared catalyst when the calcination temperature was as high as 700℃ . Results of XRD, TG-DTG and TPH for the spent catalysts showed that the Ni grain size of cat-700 and cat-800 catalysts was 9.8 nm and 8.7 nm, respectively, lower than that of cat-500 and cat-600 catalysts (15.7 nm and 13.6 nm, respectively), indicating well dispersion of Ni grain. The deposited carbon during reaction was assigned to filamentous one, massive accumulation of which would increase bed pressure drop and decrease catalyst performance. Long term stability test demonstrated that the conversion of CO2 over cat-800 catalyst was up to 95% and kept stable in 110 h.
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