Platinum Sintering on H‐ZSM‐5 Followed by Chemometrics of CO Adsorption and 2D Pressure‐Jump IR Spectroscopy of Adsorbed Species

Abstract

Zwei Welten: 2D‐IR‐Drucksprung‐Spektroskopie von adsorbiertem CO lieferte Informationen über die Umgebung und Lage von Platin‐Nanopartikeln auf Zeolith‐Trägern und das Verhalten der Pt‐Atome nach thermischer Behandlung (Aktivierung, katalytische Reaktion, Sinterung). In den Mesoporen und auf der äußeren Oberfläche des Trägers werden unterschiedliche Arten von Sintermechanismen beobachtet (siehe Bild; HF/LF=Hoch‐ bzw. Tieffrequenz).

Achieving Atomic Dispersion of Highly Loaded Transition Metals in Small‐Pore Zeolite SSZ‐13: High‐Capacity and High‐Efficiency Low‐Temperature CO and Passive NOx Adsorbers

“…EXAFS is not sensitive to the minority phases (<10 %) and HAADF‐STEM imaging is a local technique. In prior studies on Pt‐ and Pd‐loaded (0.4–1 wt %) ZSM‐5, the IR spectra of room temperature adsorbed CO always indicated the presence of Pt and Pd nanoparticles as a consequence of metal agglomeration …”

“…Today, there is a great interest to produce small‐pore zeolites loaded with atomically dispersed Pt and Pd at levels higher than 0.3 wt %. However, methods of loading transition metals ionically into SSZ‐13 at practically relevant levels (>1 wt %) are not known . Molliner et al.…”

“…The PNA performance of the thus prepared Pd/zeolite materials was satisfactory and comparable to the best state‐of‐the‐art literature but the Pd was underutilized, that is, NO/Pd≪1 (Figure S1, see Supporting Information Methods on page 3 for experimental setup and conditions). The discussion regarding why H‐forms of zeolite are not effective at producing higher loading of atomically dispersed species and how we found the right method (we call this method “modified ion exchange”) to make such materials is provided in the Supporting Information “Methods” section (pages 1–2).…”

Pt/Zeolite Catalysts for Soot Oxidation: Influence of Hydrothermal Aging

“…23 In this study, by combination of the CO titration and TEM results, it is also observed that 48%~56% of the Pt species in PtUSY exist in the form of "inner" particles (Please refer to the Supporting Information for details), which will be restricted to the micropore diameter and have small particle sizes (< 1 nm). 28 After the hydrothermal ageing, metallic Pt peaks arise on all the XRD patterns of the catalysts ( Fig. S1).…”

“…[16][17][18][19][20] Furthermore, the supported Pt particles may experience significant sintering and hereby deactivation during thermal ageing, especially in an oxidizing atmosphere like the automobile exhaust. 6,22,[25][26][27][28] However, the hydrothermal stability of Pt/zeolites as catalysts for soot oxidation has not been specifically studied so far. 22,23 Therefore, it is necessary to examine the durability of Pt/zeolites as soot oxidation catalysts to fully evaluate their application potential.…”