Fuel reforming over Ni-based catalysts coupled with selective catalytic reduction of NOx

Abstract

La 2 O 2 CO 3 , CeO 2 , ZrO 2 , and Al 2 O 3 supported Ni catalysts were prepared by an impregnation method and employed for reforming of n -dodecane to simultaneously produce low molecular weight hydrocarbons (HCs) and H 2 . These reforming products served as reductants and promoters for the selective catalytic reduction (SCR) of NO x over Ag/Al 2 O 3 . N 2 adsorption-desorption, X-Ray powder diffraction, H 2 temperature programmed reduction, and thermogravimetric analysis were performed for Ni-based catalysts. It was shown that an increase in the redox performance of Ni-based catalysts enhanced the H 2 production from fuel reforming but decreased the amount of HCs available for further SCR reaction. The temperature window for NO x removal using the coupled system shifted to lower temperatures at the expense of the NO x conversion. An optimal ratio of H 2 /HCs was achieved using a Ni/ZrO 2 +Ag/Al 2 O 3 dual catalyst system, which exhibited high activity for NO x conversion at typical diesel exhaust temperatures. Studies on the durability and performance of this Ni/ZrO 2 +Ag/Al 2 O 3 coupled system were also performed, and the results showed that the lifetime of the reforming catalyst may limit the system and requires further improvement. Small molecular weight hydrocarbons and H 2 produced from on-board fuel reforming over Ni-based catalysts were used as reductants in the selective catalytic reduction of NO x over Ag/Al 2 O 3 catalysts at typical diesel exhaust temperatures.