An Assessment of Zeolite Framework Effect for Low-Temperature NOX Adsorbers

Pd-promoted zeolites (Y, ZSM-5, FER, SSZ-13) were prepared and characterized to analyze their properties as low-temperature NOx adsorbers. The samples investigated by BET XRD in situ FT-IR spectroscopy of CO NO adsorption probe the Pd sites nature adsorbed species. adsorption/desorption performances at low temperatures examined microreactor measurements upon NO/O2 followed TPD presence water carbon dioxide. It was enlightened that: (i) zeolite framework influences dispersion: smaller cage, higher dispersion, irrespective Si/Al ratio. Accordingly, following dispersion order has been observed, inversely cage size: Pd/SSZ-13 > Pd/ZSM-5 ~ Pd/FER >> Pd/Y; (ii) is present isolated Pdn+ species PdOx particles; (iii) governs storage capacity: capacity; (iv) adsorbs mainly form nitrosyls nitrates; (v) desorption occurs both a temperature below 200 °C high-temperature range (near 350 °C).