A new cell for in situ X-ray diffraction studies of catalysts and other materials under reactive gas atmospheres

A novel cell for in situ X-ray diffraction (XRD) has been designed and built. It allows the study of samples in flowing or static reactive gas environments at atmospheric pressure and at temperatures up to 1273 K. The sample is supported on a quartz-glass frit between two hemispherical heaters. The reactant gas mixture passes through the powder sample and is analysed on exit by quadrupole mass spectrometry and/or gas chromatography. Since all the reactants pass through the sample, the arrangement is particularly suitable for the study of catalysts. This instrument geometry also ensures that all the diffracting sample is in the same environment and gives high diffracted intensity, allowing the system to be used with a standard X-ray source and detector. A thermocouple placed in the sample provides an accurate measure of sample temperature; the temperature distribution across the sample is very uniform. Three examples of the use of the high-temperature cell for in situ X-ray diffraction (XRD) are presented. These give some idea of the scope of experiments that can be performed in the apparatus. Two of the examples involve studies of catalysts in various gases, the other follows the course of a solid-state reaction.