High-pressure flow reactor designed for an ultrahigh vacuum analysis system

Abstract

A novel high-pressure flow reactor designed to operate with real powder catalysts at pressures up to 10 bar and temperatures up to 400 °C is described. The gas flow is regulated by mass flow controllers, and the temperature is adjusted by a proportional integral derivative control. Using a heatable capillary along with strong differential pumping allows the gas composition to be monitored on-line. The high-pressure volume is kept small in order to ensure rapid evacuation after the reaction. All parts of the system exposed to gas pressure and temperature are made of metal or ceramic. The reactor is attached to an ultra-high-vacuum system equipped with x-ray photoelectron spectroscopy and secondary ion mass spectrometry for surface and reaction studies. The performance of the system is demonstrated by CO-hydrogenation experiments with promoted Pd/SiO2 catalysts.

Study of Water Adsorption on Organics Crystal Surfaces Using a Modified X-ray Photoelectron Spectroscopy Instrument

“…One of the foremost reasons for the incompatibility of XPS, likewise other surface techniques, with high gas pressures is the attenuation of the signal by inelastic collisions with gas-phase molecules at pressures above ultrahigh vacuum conditions. Also, there exists a “pressure gap” between the modeling of the kinetics of adsorption and catalytic reactions under high vacuum and those experienced at high pressure conditions; − normally pressures of at least a few Torr but frequently higher (∼1 atm) are required for activation or sufficient reaction rates to be observed. , This gap has been bridged in recent years by using differentially pumped stages in the analysis chamber, ,,− allowing operating pressures above 5 Torr. However, such systems cannot inherently be used to investigate surface effects or chemical states “activated” at vapor pressures relevant for samples exposed to ambient conditions, particularly organic solids.…”