Acidity-modulated Pt speciation in Zeolite Y governing room-temperature HCHO oxidation

Title : Acidity-modulated Pt speciation in Zeolite Y governing room-temperature HCHO oxidation

Abstract:

Organic compounds (VOCs), particularly formaldehyde (HCHO), require efficient low-temperature abatement. Pt supported on zeolites has emerged as a promising catalyst for this reaction, however, how the intrinsic acidity of zeolite modulates the Pt active sites to govern the reaction pathway remains insufficiently understood. Herein, Pt-incorporated zeolite Y (Pt/Y) catalysts with a tuneable SiO₂/Al₂O₃ ratio (SAR) were designed to systematically regulate the distribution of Brønsted and Lewis acid sites and their interactions with Pt species. This tailored acidic environment stabilizes distinct Pt species anchored on ion-exchange sites (Brønsted acid sites) and octahedrally coordinated extra-framework aluminum (Lewis acid sites), thereby governing the local coordination, dispersion, and electronic state of Pt. In Pt/Y_2.6, Pt is predominantly stabilized in an oxidized form (Pt^δ+), where excess OH groups preferentially favor C-H bond activation, leading to the accumulation of oxygenated intermediates. In contrast, Pt/Y₃₀ with its predominant Lewis acidity promotes the formation of smaller, more highly dispersed metallic Pt⁰ species. Owing to their electron-rich character, these metallic Pt⁰ sites exhibit a strong ability to activate molecular oxygen (O₂) and generate reactive oxidative species (O^*), thereby facilitating coupled C-H and C-O bond activation and enhancing deep oxidation. As a result, the Pt/Y₃₀ catalyst achieved 99.9% HCHO conversion at a high WHSV of 600,000 cm³ h^-1 g_cat^-1, along with a mass-specific rate of 183.9 μmol s^-1 g_metal^-1, and maintained high stability over 40 h of continuous reaction, effectively suppressing deposition-induced deactivation. This study reveals a clear structure-function relationship driven by the synergistic effects of acid-site distribution and Pt coordination on bond-selective oxidation behavior, offering a rational basis for designing advanced zeolite-supported catalysts for VOC removal.

Biography:

Ammara Ayub is a chemical engineer and Ph.D. student at the University of Science and Technology (UST), South Korea. She received her bachelor’s degree in Chemical Engineering from the University of Engineering and Technology (UET), Pakistan, and her master’s degree in Energy and Environmental Engineering. Since 2023, she has been working as a researcher at the Korea Institute of Science and Technology (KIST). Her research focuses on heterogeneous catalysis, environmental catalysis, and zeolite-supported noble metal catalysts for low-temperature formaldehyde and VOC oxidation. She has experience in catalyst synthesis, catalytic activity evaluation, and advanced characterization techniques, including XPS, H₂-TPR, NH₃-TPD, CO-FTIR/DRIFTS, XANES, and EXAFS. Her work aims to develop efficient catalytic materials for environmental and energy-related applications.