The Impregnation Technics Of Automotive Exhaust Control Pd/CZ/Al₂O₃ Catalyst

Comparing with Pt and Rh, Pd is more abundant in resource, cheaper and better at light-off performance among the three kinds of rare-mental active components of TWC catalyst, and the Pd-only catalyst is playing more and more important role in the automotive emission control materals.This paper investigated the impregnation technics of Pd/CZ/Al₂O₃ catalyst, optimized the technics parameters and provided data for the further study of Pd-only catalyst.The paper prepared the Pd/CZ/Al₂O₃ catalyst by impregnation method. The effect of Pd precursor concentration, the number of single-dipping, Pd addition order and calcining sequence on the three-way catalytic activity and dynamic oxygen storage capacity of the catalysts were studied and analysed combining with XRD, BET, TPR and noble metals dispersion.The results of Pd precursor concentration and the number of single-dipping show that: There is not a monotony increase or decrease by degrees of Pd precursor concentration or the single-dipping number versus the three-way catalytic activity, but they have optimized values. Noble metal dispersion shows that Pd dispersion is elevated at that value, the active sites is increased and the agglomeration of Pd particle is prevented.The results of Pd addition order and calcining sequence indicate that: Pd/CZ interaction has an advantage over the conversion of CO while Pd/Al₂O₃ interaction has an advantage over the conversion of HC and NO. TPR result shows that the interaction mode between Pd and carrier is affected by Pd addition order and calcined sequence before aging and the distribution of Pd over the catalysts keeps consistent after aged.