Inactive aluminate spinels as precursors for design of CPO and reforming catalysts

We here illustrate the potential of inactive Ni- and Ni-Co aluminate spinels prepared at high temperatures (1393 K) as precursors for the design of catalysts for partial oxidation (CPO) and steam methane reforming (SMR). By exposing the aluminate spinel to hydrogen atmosphere at 1073 K for 2h, the inactive spinel was restructured to an active catalyst with excellent initial stability (20-40 h). The hydrogen treatment enabled the growth of supported nano-sized (15-25 nm) metal particles. Methane conversion during CPO over unreduced NiAl2O4 did not exceed the empty reactor conversion (6% at 1073 K) and the unreduced NiAl2O4 catalyst showed no activity in SMR at 973 K furnace temperature and 1 atm. Thus, the reduction with H-2 was critical for obtaining an active phase capable of activating methane and catalysing the CPO and SMR reactions. Once activated by high temperature reduction, close to equilibrium yields were obtained over the in situ reduced catalysts. Estimates of activation energies in SMR over reduced NiAl2O4 were in accordance with our expectations (about 110 kJ/mol). The catalysts were characterized by H-2-chemisorption, N-2-sorption, XPS, XRD, STEM/EDS and TPx. (C) 2010 Elsevier B.V. All rights reserved.