Study Of Metal-Support Interactions In Model Nanocatalysts: Anchoring Of Pt Metallic Nanoparticles On Alumina Support

Catalyst deactivation or the loss over time of activity and/or selectivity of a catalyst is of great concern in developing industrial catalyst; a fast catalyst that deactivates rapidly during the catalytic reaction is of little commercial value. Thus, understanding catalyst deactivation and more importantly developing strategies to suppress catalyst deactivation are of great importance. One of the intrinsic mechanisms of catalyst deactivation is sintering: the loss of active centers due to growth of the catalytic phases. For supported metal catalysts, there are three principal mechanisms of metal crystallite growth: 1) crystallite migration, 2) atomic migration, and 3) vapor transport. Regardless of the specific mechanisms sintering processes, in general, are kinetically slow but detrimentally irreversible or difficult to be reversed. Thus, one of the strategies in developing nanostructured catalysts is to prevent or significantly slow down the sintering of metal nanoparticles during the catalytic processes. Many parameters affect the growth of metal nanoparticles during the catalytic reaction: temperature, atmosphere, size of nanoparticles, metal type, surface area and tortuosity of the support, promoters and impurities, texture and porosity of the support, etc. A typical example of catalyst deactivation by sintering is the growth of noble metal nanoparticles in the three-way catalyst during the high temperature reaction in the automobile exhaust.