Response surface study of the performance of lean NOx storage catalysts as a function of reaction conditions and catalyst composition

NOx storage and reduction (NSR) catalysts containing Pt, Ba and Fe were studied as a function of reaction conditions and catalyst composition using response surface methodology combined with high-throughput experimentation. The concentrations of the reactant gases and the reactor temperature were varied to probe their effect on catalyst performance, as quantified by lean NOx storage and N2O production. An empirical model relating the catalyst performance to five reaction condition variables and three metal weight loading variables has also been developed. It was found that the temperature and the concentrations of the reducing agents, i.e. carbon monoxide and ethylene, had the strongest effect on the lean NOx storage. It was also found that the Pt and Ba weight loadings had a much greater effect than Fe weight loadings on the performance of NSR catalysts. This model provides insight about the factors controlling the NOx conversion by NSR catalysts and also predicts the optimum catalyst composition for given reaction conditions and vice versa. As an additional study, the relationship between sulfur poisoning, nitrous oxide production, and exotherm generation was also explored.