Propane oxidative dehydrogenation over unpromoted and Nb promoted NiO loaded calcium-hydroxyapatite catalysts

Abstract

Nickel loaded calcium-hydroxyapatite (xNi/CaHAp) and niobium promoted xNi/CaHAp catalysts were synthesized and characterised by X-ray, FTIR, U.V-visible-NIR spectroscopies and temperature programmed reduction (H2-TPR). X-ray diffraction patterns of xNi/CaHAp showed that for nickel loadings above 5 wt.% Ni, diffraction lines belonging to bulk NiO start to appear. The average size of those nickel oxide particles is equal to 16, 23, and 35 nm for x = 10, 15 and 20 Wt.%, respectively. U.V-visible and TPR showed that the loaded nickel is hosted by octahedral and pseudo-octahedral sites.

Calcium-hydroxyapatite loaded with different amounts of nickel and niobium promoted xNi/CaHAp catalysts were tested in oxidative dehydrogenation propane (ODH). The best performance was achieved with a nickel loading of x = 10%. The corresponding stationary conversion of propane is equal to 22% with a propylene yield of 13%.

Addition of niobium to xNi/CaHAp decreases the global conversion but enhances the propylene selective and the stability of the catalyst with time on stream. The best results were obtained with 0.15 wt.% Nb. The propylene yield at stead state reaches 14% at 425°C.