丙烷氧化脱氢制丙烯催化剂研究进展

综述了丙烷氧化脱氢(ODH)制丙烯催化剂研制表征方面的最新成果,论述了催化剂各组分的作用、催化剂表面的活性氧物种性质和催化反应机理,评价了各种催化体系的丙烷ODH反应性能,提出了该研究领域今后的发展方向。     

Oxidation of NH3 on polycrystalline copper and Cu(1 1 0): a combined FT-IRAS and kinetics investigation

The kinetics of the reaction of oxidation of ammonia on polycrystalline copper, has been investigated, in a re-circulating reactor, and correlated to a characterisation of the catalyst surface at different extent of conversions.

The rapid formation of a nitride or oxynitride phase and its reactivity have been demonstrated. Under oxidising conditions, P_NH3=P_O2, and up to 650 K, dinitrogen is the only product of the reaction; N₂O being formed when T or P_O2 increases further. The correlation of these kinetics results to an in situ characterisation of the same reaction at RT by Fourier-transformed infrared reflection-absorption spectroscopy (FT-IRAS), on a well defined Cu(1 1 0) surface, led to the following conclusion: two reaction pathways contribute to the conversion of ammonia: (i) its decomposition on copper; (ii) the reaction between ammonia molecules and oxygen adsorbed from the gas phase. The major adsorbed species is oxygen; intermediate species are NH₂, NH and possibly HNO formed when the oxygen surface concentration is sufficient. Increasing the pressure of oxygen induces, at high T, the formation of nitrous oxide; N₂O results from an oxidation of the surface copper nitride or from the interaction of two surface HNO intermediates.