Effect of preparation methods on NOx removal ability by sorption in Pt–ZrO2–Al2O3 Original Research Article

Heterogeneous porous materials of Pt–ZrO2–Al2O3 are prepared via three different procedures based on impregnation and/or ammonia precipitation to examine their ability for NOx removal by sorption. In case a sample was prepared via ammonia precipitation, the sample exhibited both a larger BET surface area and a higher NO removal ability than a sample prepared only via impregnation. The experimental results indicate that a high-temperature calcination is essential to remove residual Cl from Pt–ZrO2–Al2O3 prepared from H2PtCl6 in order to provide more active NOx sorption sites. This suggestion was supported by the experimental results: (1) the sample prepared using H2PtCl6 as a Pt source should be calcined at a higher temperature after the Pt source was added in order to exhibit a higher sorption ability, and (2) the use of Cl-free Pt sources enhanced the NOx sorption capacity even after calcination at a lower temperature.