NOx adsorption with CO and C2H4 on Pd/SSZ-13: Experiments and modeling

A transient monolith model containing microkinetic schemes for NO uptake and release over Pd/SSZ-13 without and with reductants CO or C2H4 is presented. The scheme involves three cationic Pd species (Z(-)[PdOH](+), Z(-)[Pd(2+)Z(-), Z(-)Pd(+)) as the active sites during uptake of NO, CO and C2H4, and their desorption and conversion at higher temperature. Kinetic parameters are estimated through a combination of density functional theory (DFT) estimates and a fit of uptake, desorption and conversion data. The tuned model is validated at different uptake temperatures, ramp rates, and flowrates. A "degree of uptake control" parameter is defined that helps to identify the step(s) that are uptake controlling. The model helps to interpret the data features and is used to identify operating conditions to meet application-relevant performance metrics, including NO trapping efficiency and NO release temperature. The model demonstrates higher NO uptake on Pd/SSZ-13 compared to Pd/ZSM-5.