High-Temperature Isotopic Exchange Between Water Vapor and Hydrogen Gas in an Alumina-Supported Platinum Catalyst Bed

The deuterium exchange reaction between water vapor and hydrogen gas is studied at 1 atm total pressure and temperatures from 150 to 250°C using a commercially available platinum-impregnated alumina catalyst. Below a water vapor pressure of 190 Torr, two reaction processes, an external mass transfer of hydrogen and an adsorption of water vapor on the surface of the catalyst, are involved in the rate limiting transfer step. Above 190 Torr, external mass transfer of hydrogen governs the reaction rate. An activation energy of 1.5 ± 0.6 kJ/mol is obtained for this transfer step.