X-Ray Photoelectron Spectroscopy and Temperature-Programmed Desorption Studies of Nitrided Molybdena-Alumina Catalyst

Abstract

The dynamics of a monomer-monomer and a monomer-dimer surface catalytic reaction is investigated. From the mean-field solution, finite systems eventually 'poison' at an exponential rate to a fully occupied, non-reactive state. For the monomer-monomer process, this poisoning is driven by concentration fluctuations of a diffusive nature, leading to poisoning times which vary as a power of the linear system size L. A comparison of the Monte Carlo simulations with the mean-field result suggests that the upper critical dimension for the monomer-monomer model is d, = 2. For the monomer-dimer process, there is an effective potential that needs to be surmounted by fluctuations, leading to poisoning times which grow at least as fast as eL. This gives rise to an apparent reactive steady state.

Surface Properties and Active Sites of Nitrided Mo/Al2O3 Catalysts for the Hydrodenitrogenation of Carbazole

“…Additionally, phosphorus-doped tungsten oxynitride has been prepared from heteropolyanion precursors [48]. Attention has been directed to a number of different areas, including (1) the preparation of bimetallic nitride catalysts, such as Co, Ce, Ti, and Zr-doped Mo nitrides with higher HDN activities than the pure c-Mo 2 N catalyst [42,[49][50][51][52]; (2) the specific reactivity of nitrogen compounds, such as indole [26,31], pyridine [30,[32][33][34], quinoline [24] and carbazole [25,28,29], on Mo 2 N and promoted Mo 2 N/Al 2 O 3 catalysts for C-N hydrogenolysis; (3) the activities of bulk molybdenum nitride and nitrided Mo/Al 2 O 3 in comparison to sulfided catalysts for HDN [28,53] (in the latter case, nitrides are more active), although molybdenum sulfide and sulfided NiMo/c-Al 2 O 3 catalysts were more active than the corresponding nitride for the HDN and HDS of coal-derived naphtha [17] and the light gas and heavy gas oils [54], respectively, at higher temperatures ([598 K)); (4) the kinetics of the Mo 2 N/Al 2 O 3 catalyst for HDN [22,55,56] including the competitive reaction with HDS and the effects of additives and catalyst deactivation [22,54,57]; and (5) the active surface sites on Mo 2 N/Al 2 O 3 catalysts which have been studied using XPS [55,[58][59][60], NMR [61,62], the temperature-programmed desorption(TPD)/temperature-programmed surface reaction with hydrogen (TPSR) [58,[63][64][65]…”