NO selective reduction by hydrogen on potassium titanate supported palladium catalyst

Potassium titanate (K2O-6TiO(2)) nanowires were successfully prepared by alkali treatment of TiO2 (79% anatase, 21% rutile) under autogenous pressure in a Teflon-lined autoclave at 200 degrees C. After further modification with 1 wt.% Pd by wet impregnation, the calcined and pre-reduced Pd/K2O-6TiO(2) catalyst was applied for selective reduction of NOx by H-2 (H-2-SCR) under lean conditions, together with Pd/Al2O3 and Pd/TiO2 as reference. The reference catalysts exhibited maximum NO conversion of about 50-60% at 100-130 degrees C, but with low N-2 selectivity. The N-2 selectivity on Pd/K2O-6TiO(2) was considerably high, reaching 80% at maximum, with only 11% conversion of the admixed hydrogen reductant. In situ DRIFT spectroscopy revealed surface-fixed nitrates and Pd-bound NO, but no NHx ad-species. It is concluded, that the beneficial effect of the K2O-6TiO(2) support is due mainly to a stabilization of high Pd dispersion with enhanced concentration of Pd-0-NO intermediates, and due to support alkalinity, that enhances nitrate fixation. (C) 2008 Elsevier B.V. All rights reserved.