Enhancement of NOx adsorption performance on zeolite via a facile modification strategy

Abstract

Adsorption is a promising technology for simultaneously capturing nitrogen oxides (NO_x) from flue gases and recycling NO₂ as a profitable chemical, for which a robust and efficient adsorbent provides the key step for success in practical applications. This work reports the enhancement of NO_x adsorption performances with less cost of desorption energy on Cu-ZSM-5 zeolites prepared by a facile and rapid (690 s) modification method, the incipient-wetness impregnation coupled with microwave drying (IM). In comparisons to H-ZSM-5, Na-ZSM-5 and conventionally liquid-phase ion-exchanged counterparts under sub-1000 ppm NO_x feed concentrations and room temperature, the IM sample renders a record NO_x adsorption capacity (q_t,NOx) of 0.878 mmol/g from dry gas stream on zeolites, and an applicable q_t,NOx of 0.1 mmol/g from wet gas stream with a proper copper loading (2.1 wt%). The temperature programmed desorption of NO_x on the optimal IM sample saturated with NO_x from wet gas stream exhibit primary peak temperature lower than reported Cu-ZSM-5 and significant NO₂ proportion (72.6 %) in desorbed NO_x. Deeper insights into advantageous NO_x oxidative adsorption over the properly-loaded Cu-ZSM-5 in terms of diverse adsorbate states and competitiveness towards H₂O were gained, showing IM method a promising sorbent improvement strategy for practical use.

Keywords: Adsorption; Desorption; Incipient-wetness impregnation; Nitrogen oxides; Zeolite.