Hydrophobic Modification of ZSM-5-Encapsulated Uniform Pt Nanoparticles for Catalytic Oxidation of Volatile Organic Compounds

Zeolite-supported noble-metal catalysts are considered to be one of the most promising materials to achieve complete oxidation of volatile organic compounds (VOCs). However, noble metals tend to agglomerate under synthesis/reaction conditions and are easily poisoned by halogen compounds, resulting in reduced catalytic activity and stability. Herein, Pt nanoparticles (∼2 nm) encapsulated in ZSM-5 catalysts (Pt/Z-En) with a series of Si/Al molar ratios were prepared by a one-pot synthesis strategy using tetraammineplatinum nitrate as the metal precursor, and their catalytic performance for oxidation of VOCs was explored. The characterizations showed that the Pt–zeolite interaction and metal dispersion were significantly enhanced after encapsulation in zeolite. In the VOC (toluene as a model reactant) oxidation experiment, Pt/Z-En possessed higher catalytic activity compared with catalysts prepared by the impregnation method (Pt/Z-Im). In addition, hydrophobic modification by increasing the Si/Al molar ratio facilitated the adsorption of toluene and restricted the adsorption of halogen compounds (1,2-dichloroethane) on the catalyst, which further promoted catalytic activity and stability. The Pt/Z-200-En catalyst with a Si/Al molar ratio of 200 gave the optimum catalytic performance, with a toluene conversion of 98% at a temperature as low as 214 °C with long-term stability.