New Insights into the Nature of Co‐components and Their Impact on Pd Structure: X‐ray Absorption Studies on Toluene Acetoxylation Catalysts

Abstract

Co-components are a powerful tool to tune the performance of catalysts, but their nature and their impact on the catalysts is often controversially discussed. In this study X-ray absorption spectroscopy (XAS) was employed to elucidate the nature of co-components and their impact on the catalytic reaction. In anatase-supported Pd-based catalysts for the gas-phase acetoxylation of toluene, less noble co-components (e.g., Mn, Co, and Sb) spread over the support in their oxidic form and changed their valence state on stream. Incorporated atoms such as C or a small part of the Sb affect the electronic structure of Pd. For the noble Au, only a weak interaction with the support and Pd was observed during time on stream. Only XAS at the K-edges together with investigations of the Pd L-edge for a better understanding of the electronic structure, supplemented by STEM for elemental mapping, allow such detailed insights.

Bimetallic Catalysts Containing Gold and Palladium for Environmentally Important Reactions

“…After testing these two series of catalysts, one concluded that 10% Pd and 8% Sb on TiO 2 (anatase) was the right combination and hence this was used as a model catalyst in the next runs. Besides Sb, the influence of various other co-components (e.g., Au, Mn, Co) was also investigated and characterized by X-ray absorption spectroscopy (XAS) in order to elucidate the nature of co-components and their impact on the catalytic activity/selectivity [81]. It was observed that Mn and Co oxides spread on the support TiO 2 surface while Au forms separate small metal (Au) nanoparticles besides Pd particles and exhibits a different influence on the catalytic performance.…”

Nature of surface carbon species and pathways of their formation in the heterogeneously catalysed acetoxylation of toluene

“…As a consequence, Sb incorporation promotes growth of Pd par-ticles. 15 The atomic ratio of Pd to Sb in these particles is around 5. Unfortunately, this catalyst was found to undergo deactivation during the course of reaction after several hours of operation.…”

Effects of composition and heat treatment on manganese–bismuth magnets

“…The XANES can be used to identify the chemical species from oxidation states of the absorbing atoms. Synchrotron XANES has been employed for structural investigation of a variety of nanoparticles including iron oxides [11], zinc ferrite [12] and toluene acetoxylation catalysts [13]. The only report involving MnBi was to study the effect of Cu doping [14].…”