Influence of the alumina origin on the reducibility of NiO catalyst

Abstract

In order to determine the influence of the origin of alumina support on the reducibility of the NiO-Al2O3 catalyst four model systems were prepared, by impregnation of gibbsite, boehmite, γ-Al 2O3 and α-Al2O3 with nickel nitrate solution. Prior to reduction (400°C, hydrogen flow) the prepared model catalyst samples were calcined at 400°C, 900°C and 1000°C for 24 hours. It was noticed that the sample prepared on α-Al 2O3 can be easily reduced, thanks to weak interaction between the catalyst components. Samples prepared on gibbste, boehmite and γ-Al2O3, previously calcined at 400°C are more difficult to reduce, due to stronger interaction between NiO and catalyst support. Samples calcined at 900°C and 1000°C can be reduced only after prolonged reduction time (eight hours), as evidenced by gravimetric method. However, this thermal effect was not strong enough to be observed by DTA and DSC. High resistance of these samples against reduction is explained by intensive nickel spinel, NiAl2O4, formation.