Methane dry reforming on Ni/Ce_(0.75)Zr_(0.25)O_2-MgAl_2O_4 and Ni/Ce_(0.75)Zr_(0.25)O_2-γ-alumina: Effects of support composition and water addition

摘要

Nickel catalysts (10wt.%) supported on MgAl_2O_4 and γ-Al_2O_3 were prepared by the wet impregnation method and promoted with various contents of Ce_(0.75)Zr_(0.25)O_(2). X-ray diffraction (XRD), BET surface area, scanning electron microscopy (SEM), thermal gravi-metric analysis (TGA), H_2-temperature programmed reduction (TPR) and CO_2-temperature programmed desorption fTPD) were employed to observe the characteristics of the prepared catalysts. Ni/y-Al_2O_3 and Ni/Ce_(0.75)Zr_(0.25)O_2 (5wt.%)-MgAl_2O_4 showed better activity in CO_2 methane reforming with 75.7(0.93) and 75.4(0.82) CH_4 conversions (and H_2/ CO ratio). H_2O was added to feed in the range of H_2O/(CH_4 + CO_2): 0.1-0.5 to suppress reverse water gas shift (RWGS) effect and adjusting H_2/CO ratio. The CH_4 conversions (and H_2/CO) increased to 81(1.1) with 0.5 water/carbon mole ratio in Ni/Y-Al_2O_3 and 85(1.2) with 0.2 water/carbon mole ratio in Ni/Ce_(0.75)Zr_(0.25)O_2 (5wt.%)-MgAl_2O_4. The stability of Ni/ Ce/Ce_(0.75)Zr_(0.25)O_2 (5wt.%)-MgAl_2O_4 in the presence and absence of water was investigated. Coke formation and amount in used catalysts were examined by SEM and TGA, respec-tively. The results showed that the amount of carbon was suppressed and negligible coke formation (less than 3%) was observed in the presence of 0.2 water/carbon mole ratio over Ni/Ce_(0.75)Zr_(0.25)O_2 (5wt.%)-MgAl_2O_4 catalyst.