Kinetic investigation of the NO reduction by H_2 over noble metal based catalysts

摘要

This paper reports a kinetic investigation of the overall reduction of NO by H_2 over supported palladium based catalysts.Drastic changes in the kinetic features of Pd were found after deposition on reducible LaCoO_3 materials in comparison with alumina.Peculiar interactions between palladium and LaCoO_3 build up during a pre-activation thermal treatment in H_2 at high temperature which completely modify the kinetic behaviour of Pd.In such a case,a classical Langmuir-Hinshelwood mechanism,previously proposed on Pd/Al_2O_3,is unable to model steady-state rate measurements on pre-reduced Pd/LaCoO_3.A bi-functional mechanism involving anionic vacancies at the vicinity of palladium particles leads to a better agreement.