Alkaline earth metal oxide modification of Ni/Al2O3 for hydrogen production from the partial oxidation and reforming of dimethyl ether

Abstract

The modification of Ni/Al2O3 catalyst by alkaline earth metal oxides including MgO, CaO, SrO and BaO was investigated for hydrogen production from the partial oxidation and reforming of dimethyl ether. MgO modification of the Ni/Al2O3 catalyst enhanced the formation of NiAl2O4. There was only one reduction peak from 700 to 950 °C, which is usually ascribed to the reduction of NiAl2O4. The Ni-containing species which are easily reduced at low temperature were removed. When the MgO modified Ni/Al2O3 was reduced at 750 °C in the performance evaluation, a small amount of Ni was produced from NiAl2O4 to give small and active Ni sites, resulting in better catalytic reforming performance than for the unmodified Ni/Al2O3. The H2 yield of 88% and CO selectivity of 86% was obtained at 800 °C when MgO modified Ni/Al2O3 was adopted as a reforming catalyst, which was combined with 0.5 wt% Pt/Al2O3 to form a dual bed catalysts. The other metal (Ca, Sr, Ba) oxide modification of Ni/Al2O3 catalyst, however, did not enhance the formation of NiAl2O4 as well as MgO, and there were still certain amounts of low temperature reducible NiO species, resulting in a worse catalytic performance than the unmodified Ni/Al2O3. The variation of the amount of MgO modification had no obvious effect on the formation of NiAl2O4. However, the peak reduction temperature of 7.5 wt% MgO modified Ni/Al2O3 in H2-TPR patterns was a little lower than that of 5.0 or 10.0 wt% MgO modified Ni/Al2O3, resulting in a little better catalytic performance by giving more active Ni sites reduced from NiAl2O4 at 750 °C.