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Abstract

Powder X-ray diffraction (XRD) is one of the most basic tools for catalyst characterization. It delivers information about phases and particle sizes in normal use of the data. This information is often used in attempts to rationalize the function of catalytic materials. Information about constitu-tion and the operational state of the active material in a catalyst can be obtained with much less extrapolation if the powder X-ray diffraction data are acquired under reaction conditions and the method is extended from XRD to in situ powder diffraction analysis (IPDA). The contribution describes the type of information available, highlights some physical principles of diffraction needed to evaluate the data and describes how nanostructural information about active material can be derived from such experiments. It also gives hints about instrumentation and evaluates the current literature for strategies and systems studied. A main conclusion is that IPDA is a very useful tool for basic catalyst characterization that is augmented in its power enormously when combined with other in situ techniques elucidating structure at different length scales than XRD.