Chemical imaging of catalytic solids with synchrotron radiation

Abstract

Heterogeneous catalysis is a term normally used to describe a group of catalytic processes, yet it could equally be employed to describe the catalytic solid itself. A better understanding of the chemical and structural variation within such materials is thus a pre-requisite for the rationalising of structure-function relationships and ultimately to the design of new, more sustainable catalytic processes. The past 20 years has witnessed marked improvements in technologies required for analytical measurements at synchrotron sources, including higher photon brightness, nano-focusing, rapid, high resolution data acquisition and in the handling of large volumes of data. It is now possible to image materials using the entire synchrotron radiative profile, thus heralding a new era of in situ/operando measurements of catalytic solids. In this tutorial review we discuss the recent work in this exciting new research area and finally conclude with a future outlook on what will be possible/challenging to measure in the not-too-distant future.

Binder Effects in SiO2‐ and Al2O3‐Bound Zeolite ZSM‐5‐Based Extrudates as Studied by Microspectroscopy

“…20, 21 Given the recent enhancements in chemical imaging methods,22, 23 such as single‐molecule and confocal fluorescence microscopy,21, 24–27 UV/Vis microspectroscopy,28, 29 IR and Raman microscopy,30–32 transmission soft and hard X‐ray microscopy,33–36 X‐ray diffraction computed tomography37 and focused‐ion‐beam scanning electron microscopy,38 coupled with the improved control of these commercial catalysts for modern‐day processes,39 the time is ripe for a shift in academic focus towards understanding these more complex multi‐component and hierarchically structured catalyst materials.…”

Large Ferrierite Crystals as Models for Catalyst Deactivation during Skeletal Isomerisation of Oleic Acid: Evidence for Pore Mouth Catalysis

“…Various micro-spectroscopym ethods, [22] including scanning transmission X-ray microscopy, [23] coherent anti-Stokes Raman micro-spectroscopy, [24] confocal fluorescencem icroscopy, [25,26] UV/Vis/NIR micro-spectroscopy [27] and IR micro-spectroscopy, [28][29][30] have been used extensively in recent years to study the spatiotemporal formation of hydrocarbons in the crystals of various zeolites and zeotypes,i ncluding ones with MFI, CHA, FER and BEA topologies. [31][32][33][34][35][36] This multi-technique approach has also been successfully applied to the study of spatiotemporal heterogeneities in for example, individual fluid catalytic cracking catalyst particles of different age, [37] or catalyst powderb efore/after steaming.…”

Active Site Elucidation in Heterogeneous Catalysis via In Situ X-Ray Spectroscopies

“…When operated in its conventional photons in-/photons-out mode, XAS is also a bulk-averaging method, although some surface sensitivity is possible in total electron yield mode. [56][57][58] There are many detailed articles and reviews on the application of XAS to heterogeneous catalysis [59][60][61][62][63] and photochemistry, [64][65][66] hence only illustrative examples on the breadth of systems/materials, and wealth of information on reaction mechanisms, available by time-resolved XAS approaches are provided.…”