Ultra-high vacuum compatible reactor for model catalyst study of ammonia synthesis at ambient pressure

Abstract

A high sensitivity reactor was developed to study slow reactions, such as ammonia synthesis over low surface area model catalysts at 1 bar and up to 550 °C. The reactor is connected to an ultra-high vacuum system with a transferable sample design, which allows for cleaning, preparation, and spectroscopic characterization of samples before and after the reaction without exposure to any contaminated environment, such as air. A quasi-closed small volume (250 µl) quartz glass reaction cell is integrated through a capillary with a quartz glass sniffer tube connected to a mass spectrometer. The capillary reduces the 1 bar pressure in the cell to 10−7 mbar in the sniffer tube and mass spectrometer chamber. A quartz fiber-guided laser is used to heat up the sample, and the temperature can be regulated by the proportional–integral–derivative controlled laser power output for fast reaction kinetics research. Proof of principle ammonia synthesis experiments in this reactor at 1 bar, 350–500 °C on Fe(111) single crystal and mass-selected Ru clusters supported on CeO2 thin film yield kinetic parameters that agree very well to those reported in the literature.