In situ and operando study of catalysts during high-temperature high-pressure catalysis in a fixed-bed plug flow reactor with x-ray absorption spectroscopy.

This article focuses on the development and validation of a high-temperature high-pressure catalysis-x-ray absorption spectroscopy (HTHP Catalysis-XAS) system designed for in situ/operando characterization of catalysts during catalytic reactions under harsh conditions. The system employs thin quartz or beryllium tubes as reactors to enable X-ray absorption spectroscopy (XAS), including X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), at temperatures up to 550 °C and pressures up to 60 bars. Demonstrations using ruthenium (Ru) and cobalt (Co) catalysts during Fischer–Tropsch synthesis and related reactions revealed structural changes in the catalysts under HTHP conditions that were not observable under lower pressure or ex situ conditions, highlighting the importance of operando characterization for understanding authentic catalyst structures. The article provides detailed descriptions of the reactor design, sealing methods, and safety considerations to facilitate reproducibility by the catalysis research community.