• catalytic gas/solid and liquid/solid reactions;
  • high-energy X-rays;
  • X-ray diffraction;
  • hydrogen storage;
  • high pressure;
  • high temperature

A high-pressure–high-temperature gas-loading system (GLS) is described for combined operando X-ray diffraction and mass spectrometry investigations during catalysed gas/solid or liquid/solid reactions. The pressure cell consists of a single-crystal sapphire tube which serves as both high-pressure container and reaction cell, with up to 6 mm inner diameter. The system can operate in two different configurations, under either static high pressure or dynamic pressurized flow. The transportable reaction cell can be filled under inert atmosphere inside a glove box, enabling studies with oxygen-sensitive compounds to be conducted. The five main benefits of this system can be summarized as follows: (i) the temperature, pressure and gas-flow ranges of 298–1273 K, 10−3 mbar–200 bar (0.1–2 × 107 Pa) and 0–1 l min−1, respectively, (ii) the combination of different gases, (iii) the flexibility of the cell design, (iv) the full rotation of the pressurized cell, and (v) the combination of X-ray diffraction and mass spectrometry as analytical tools. These key points open new possibilities for studying the evolution of catalysts or compounds from a fundamental point of view as well as for industrial applications, in both cases in operando conditions.