Mechanistic insight in the propylene derived distinct NO uptake and release behaviors on Pd/SSZ-13 for low-temperature NO adsorption
Huawang Zhao, Xiaoyin Chen, Alexander J. Hill, Guohua Jing, Yongdan Li, Johannes W. Schwank
Abstract
Pd/SSZ-13 catalysts were investigated for the simultaneous storage of NO and C3H6 at 100 °C. The effects of the state of Pd species on co-adsorption and release were studied under simulated exhaust conditions. The catalysts were characterized by NH3-TPD, XRD, and TEM for Pd2+ and PdO species. NO adsorption/release behavior is impacted by the nature of reactants and the NO storage capacity at 100 °C was enhanced by simultaneous NO + C3H6 adsorption. DRIFTs results showed that Pd2+ provides the adsorption sites for NO + C3H6 to form Pd2+(NO)(C3H6), which alleviates the inhibition effect of H2O on NO adsorption on Pd ions. Different release behaviors, which are discussed in light of the chemistry of NO and C3H6 adsorption and effect of intermediate CO, depend on whether NO was adsorbed alone or together with C3H6. The mechanistic pathways during different stages of NO + C3H6 co-adoption and release are proposed.