Effect of calcination temperature on stability and activity of Ni/MgAl2O4 catalyst for steam reforming of methane at high pressure condition

In this study, the effect of calcination temperature on the physico-chemical properties of Ni/MgAl2O4 as well as on the activity and stability of the catalyst for steam reforming of methane has been investigated. The catalyst calcination temperature was varied from 350 °C to 1000 °C while the reactor pressure was varied from 1 to 10 bar at 600 °C. An increase in calcination temperature resulted in a decrease in the nickel crystallite size and the degree of reduction. The decrease in nickel crystallite size from 12.2 nm to 8.8 nm on increasing the calcination temperature from 350 °C to 1000 °C was attributed to formation of solid solution of nickel oxide with the support and anchoring effect which prevented the sintering of nickel particles. Apart from changes in catalyst properties such as BET surface area, nickel crystallite size and reducibility of the catalyst, formation of NiAl2O4 was also confirmed by UV-vis spectroscopy. Activity results showed that the turnover frequency decreased with metal dispersion, suggesting that, for this catalyst, steam reforming of methane is a structure sensitive reaction. The conversion and stability were affected by the total pressure. With an increase in pressure the catalysts calcined at 650 °C and lower temperatures deactivated. The conversion and stability were the highest for the catalyst calcined at 850 °C.