Pd/SSZ-39 for low temperature NOx adsorber in the presence of CO and C2H4: Effects of hydrothermal aging and feed composition

Pd/SSZ-39 catalyst shows high performance for NO and C 2 H 4 adsorption even after hydrothermal aging at 850 °C. • Pd 2+ ions in Pd/SSZ-39 serve as active sites for both C 2 H 4 and NO adsorption. • In the co-existence of NO and C 2 H 4 , Pd/SSZ-39 preferentially adsorb NO while also retaining the ability to C 2 H 4 adsorption. In this work, Pd/SSZ-39 zeolite catalyst (an AEI-type) was studied as a passive NO x adsorber (PNA) and hydrocarbon trap aiming for cold-start emission control in diesel vehicles. The fresh and hydrothermally aged Pd/SSZ-39 were characterized by XRD, 27 Al NMR, H 2 -TPR, NO x -TPD and DRIFTS of CO adsorption to investigate the changes of zeolite structure and Pd species. The catalytic performance of fresh and hydrothermally aged catalyst in low temperature NO and C 2 H 4 adsorption were evaluated. Moreover, systematic PNA experiments under various conditions were conducted to study the NO and C 2 H 4 adsorption, as well as oxidation of C 2 H 4 and CO on Pd/SSZ-39. Moreover, the interaction of NO with CO or C 2 H 4 were studied by in situ DRIFTS experiments. Results demonstrate that Pd 2+ ions in Pd/SSZ-39 serve as the active sits for both C 2 H 4 and NO adsorption. In the gaseous mixtures of NO and C 2 H 4 , Pd 2+ ions in Pd/SSZ-39 tend to preferentially adsorb NO rather than C 2 H 4 . Both C 2 H 4 and CO act as a reducing component which enhances the NO adsorption and shifts the NO desorption to higher temperatures. Download: Download high-res image (237KB) Download: Download full-size image