NO selective reduction by hydrogen on potassium titanate supported palladium catalyst

Potassium titanate (K2O–6TiO2) nanowires were successfully prepared by alkali treatment of TiO2 (79% anatase, 21% rutile) under autogenous pressure in a Teflon-lined autoclave at 200 °C. After further modification with 1 wt.% Pd by wet impregnation, the calcined and pre-reduced Pd/K2O–6TiO2 catalyst was applied for selective reduction of NOx by H2 (H2–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 °C, but with low N2 selectivity. The N2 selectivity on Pd/K2O–6TiO2 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–6TiO2 support is due mainly to a stabilization of high Pd dispersion with enhanced concentration of Pd0–NO intermediates, and due to support alkalinity, that enhances nitrate fixation.