The first non-precious metal passive NOx adsorber for cold-start applications

Abstract

Co-SSZ-13 served as a non-PM passive NOx adsorber (PNA) was adopted for the first time, to the best of our knowledge, as a promising alternative to platinum-based NOx adsorbers. This Co-based catalyst has a NOx storage capacity of 27.3 μmol/gcat, which is 77% of that of Pd-SSZ-13. NOx is desorbed above 250 °C, which is appropriate for use downstream of the NH3-SCR catalyst. NO adsorption on Co-SSZ-13 resulted in the formation of dinitrosyl species, which are further converted into NO+ on the zeolite framework and nitrate species on Co2+. The strong interaction between Co2+ and NO is responsible for the high NOx storage capacity. In addition, conversion among the adsorbed species increases the NO desorption temperatures, which is important for the correct operation of PNA.