Temperature Programmed Al2O3 Desorption Spectroscopy of N2H4 Decomposition on Al2O3-Supported Ir Catalyst.

摘要

At room temperature the steady-state decomposition of N2H4 over an alumina-supported Ir catalyst was found to yield NH3 and N2 while at temperatures above 800 K the products were N2 and H2. Following exposure of the catalyst surface to N2H4 the adsorbed species were studied by the temperature programmed desorption technique at a heating rate of 2 K/s. The desorption products included N2, NH3 and H2 originating from different binding states. For the more strongly bound nitrogen (N2(beta 2)) the kinetics of desorption following exposure to N2H4 are of first-order with a desorption rate constant of 30,000,000 exp(-26,800/RT)/s. Adsorption of oxygen on the iridium catalyst was found to decrease the nitrogen binding energy and increase the nitrogen coverage. The surface coverage of all absorbed species was found to be significantly smaller on catalysts that had been used in pulse mode fuel thrusters. The differences observed were correlated with the loss in metal surface area of the catalyst. However, no differences in the binding energies of the various adspecies were detectable between fresh catalyst and used catalyst. (Author)