Dual-site Pd/perovskite monolithic catalysts for methane catalytic combustion

Novel monolithic catalysts for the high-temperature combustion of methane have been developed with a dual-site nature, to combine low and high temperature activity within a single system and widen its operating range. Such catalysts are based on strongly interacting Pd and LaMnO3 active phases supported onto La/gamma-alumina and applied as a thick washcoat on ceramic honeycombs. Optimization of the preparation procedure and catalyst characterization were performed with respect to the effects of Pd deposition method, catalyst activation strategy, and thermal history in comparison with previously developed catalysts based only on supported perovskite. Extensive methane combustion tests (steady state and transient) were run under both isothermal and autothermal lean premixed conditions in order to study intrinsic oxidation activity, light-off behavior, and real life performance in the middle to high temperature range. Experimental evidence is presented for improved activity, stability, and durability of the catalytic system, and for a self-regenerative behavior of Pd active sites through reversible interaction with perovskite lattice. Implications of novel combined catalyst functionalities are addressed with respect to operation of a fully catalytic burner.