Adsorption Assisted Desorption of NH3 on γ-Alumina Studied with Positron Emission Profiling.

Evidence for adsorption assisted desorption of 13NH3 in the presence of gas phase ammonia on γ-alumina is presented. Due to lateral interactions with physisorbed ammonia, the adsorption enthalpy of ammonia on γ-alumina was measured to be -11 ± 1kJ/mol, using a 13NH3/14NH3 isotopic exchange method. This adsorption/desorption exchange was monitored with positron emission profiling. Infrared spectroscopy showed ammonia to exchange preferentially on the Lewis acid sites of alumina. [ABSTRACT FROM AUTHOR]