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 2 h, 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 H2 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 H2-chemisorption, N2-sorption, XPS, XRD, STEM/EDS and TPx.
Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (54 K)Download as PowerPoint slideResearch highlights▶ Ni and Ni–Co aluminate spinels as catalyst precursors. ▶ Catalysts for partial oxidation and steam methane reforming. ▶ Hydrogen treatment at high temperature enables growth of nano-sized metal particles. ▶ Ni aluminate spinels does not activate methane at temperatures below 900 K.
Journal: Applied Catalysis A: General - Volume 383, Issues 1–2, 31 July 2010, Pages 119–127