KINETICS OF AMMONIA DECOMPOSITION ON VANADIUM NITRIDE

At high temperatures, above 750 K, the kinetics of ammonia decomposition on vanadium nitride can be described by two irreversible steps, the adsorption of ammonia and the desorption of dinitrogen. There is no partial pressure dependence on nitrogen or hydrogen. This is the same mechanism as that first found on tungsten and will be called the Tamaru mechanism, after its discoverer. First-order and second-order kinetic models fit the data equally well. However, calculation of the preexponential factors give better agreement for the second-order model. Rate parameters for VN are in between those found for Pt and Fe, providing another example where the catalytic properties of an early transition metal carbide or nitride resemble those of a Group VIII metal. © 1992.