Efficient in-situ regeneration method of the catalytic activity of aged TWC

Abstract

The expansion of durability of deactivated "three-way" catalysts (TWCs) used in gasoline-driven cars by applying efficient, economically viable and environmentally friendly methods for the in situ regeneration of their performance to acceptable levels was investigated. New experimental results on the use of a weak oxalic acid washing solution as a means of an efficient regeneration method of a severely aged (83,000 km mileage) commercial TWC are presented. Oxalic acid is shown to be the most efficient extracting agent of phosphorus, a severe poison of TWCs, among acetic acid, citric acid, NTA and EDTA investigated. X-ray diffraction studies provided strong evidence that washing of the aged TWC results in the removal of CePO4, AlPO4 and (Mg,Ca,Zn)3(PO4)2 type phosphates leading to a significant increase of BET area and pore volume, as well as of CO and NO conversions (catalytic activity tests). The latter is strongly related with the increase in the number of active catalytic sites, as illustrated by in situ DRIFTS studies, after opening closed pores and uncovering additional catalyst surface. © 2007 Springer Science+Business Media, LLC.