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Within a fluid catalytic cracking (FCC) unit, a mixture of catalyst particles that consist of either zeolite Y (FCC-Y) or ZSM-5 (FCC-ZSM-5) is used in order to boost the propylene yield when processing crude oil fractions. Mixtures of differently aged FCC-Y and FCC-ZSM-5 particles circulating in the FCC unit, the so-called equilibrium catalyst (Ecat), are routinely studied to monitor the overall efficiency of the FCC process. In this study, the age of individual catalyst particles is evaluated based upon photographs after selective staining with substituted styrene molecules. The observed color changes are linked to physical properties, such as the micropore volume and catalytic cracking activity data. Furthermore, it has been possible to determine the relative amount of FCC-Y and FCC-ZSM-5 in an artificial series of physical mixtures as well as in an Ecat sample with unknown composition. As a result, a new practical tool is introduced in the field of zeolite catalysis to evaluate FCC catalyst performances on the basis of photo-spectroscopic measurements with an off-the-shelf digital single lens reflex (DSLR) photo-camera with a macro lens. The results also demonstrate that there is an interesting time and cost trade-off between single catalyst particle studies, as performed with e.g. UV-vis, synchrotron-based IR and fluorescence micro-spectroscopy, and many catalyst particle photo-spectroscopy studies, making use of a relatively simple DSLR photo-camera. The latter approach offers clear prospects for the quality control of e.g. FCC catalyst manufacturing plants.

Straightforward analysis of chemical processes on the nanoscale is difficult, as the measurement volume is linked to a discrete number of molecules, ruling out any ensemble averaging over rotation and diffusion processes. Raman spectroscopy is sufficiently selective for monitoring chemical changes, but is not sufficiently sensitive to be applied directly. Surface‐enhanced Raman spectroscopy (SERS) can be applied for studying reaction kinetics, but adds additional variability in the signal as the enhancement factor is not the same for every location. A novel chemometric method described here separates reaction kinetics from short‐term variability, based on the lack of fit in a principal‐component analysis. We show that it is possible to study effects that occur on different time scales independently without data reduction using the photocatalytic reduction of p‐nitrothiophenol as a showcase system. Using this approach a better description of the nanoscale reaction kinetics becomes available, while the short‐term variations can be examined separately to examine reorientation and/or diffusion effects. It may even be possible to identify reaction intermediates through this approach. With only a limited number of reactive molecules in the studied volume, an intermediate on a SERS hot spot may temporarily dominate the spectrum. Now such events can be easily separated from the bulk conversion process by making use of this chemometric method.