(521f) Simple Preparation Method of K2CO3-Promoted Hydrotalcite-like Compounds for NOx Adsorption at Low Temperature

Lean-burn engines operate at higher air-to-fuel ratios than stoichiometric ratio to reduce the fuel consumption and CO₂ emissions. Vehicle pollutants including carbon monoxide (CO), hydrocarbons, and nitrogen oxides (NO_x) can be simultaneously removed by three-way catalysts (TWC), however, the catalytic activity for NO_x reduction significantly decreases in the lean-burn condition that the oxygen concentration increases and exhaust gases temperature decreases. Among various NO_x removal systems replacing TWC, lean NO_x trap (LNT) that is based on the adsorption concept is considered a promising technology. In this system, NO is oxidized, and then stored on the adsorbent during lean condition. For successful application of LNT, it is necessary to develop NOx adsorbents with high adsorption performance.

Since the NO_x storage ability is strongly related to the basicity of storage materials, the incorporation of alkali metal is a powerful strategy for improving NO_x adsorption performance. In this study, we prepared K₂CO₃-promoted hydrotalcite-like compounds for NO_x adsorbent in a facile method. While the conventional method includes a step for synthesizing hydrotalcite-like compounds and additional step for introducing K₂CO₃, these two procedures could be achieved simultaneously through hydrothermal treatment. The NO_x adsorbents developed in this study presented excellent performance compared with previous works, and the role of K₂CO₃ on NOx adsorption was investigated based on the X-ray photoelectron spectroscopy (XPS) and in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS).