Kaolin-derived ZSM-5 zeolite encapsulated with ultra-low loading of Pt catalysts for synergetic hydrocarbon adsorption/oxidation application

Abstract

The regulations for emissions from internal combustion engine vehicles were becoming increasingly stringent, necessitating the development of cost-effective, high-performance purification materials. In this study, a HCs trap of kaolin-based ZSM-5 zeolite encapsulated ultra-low loading of Pt, with dual functions of adsorption and oxidation, was synthesized by a ligand-assisted hydrothermal method (Pt_0.1@ZSM-5). The results of the corresponding adsorption-oxidation test demonstrated that the degradation efficiency of Pt_0.1@ZSM-5 on propene reached 89.6 %, which could effectively reduce propene emission during cold-start period. More importantly, the degradation efficiency of Pt_0.1@ZSM-5 on propene reached 67.9 % at the low temperature stage of 60 °C–160 °C. The primary reason for this was that the Pt_0.1@ZSM-5 sample demonstrated exceptional catalytic activity with regard to propene oxidation, exhibiting a T₉₀ of 192 °C. The confinement effect of zeolite resulted in the Pt_0.1@ZSM-5 exhibiting a smaller nanoparticle size, an abundance of acidic sites, and a higher ratio of adsorbed oxygen. These properties contributed to the effective deep oxidation of propene. Furthermore, the degradation efficiency of propene was sustained at a high level (around 95 %) throughout the course of five adsorption-oxidation cycle tests. This study presented a novel approach for the functionalization and utilization of kaolin and provides guidance for its application in exhaust emissions during the cold-start period.