Understanding the Overcoated Catalyst Using in Situ Synchrotron X-Ray Techniques

Abstract

Carbonaceous feeds, such as oil, gas, and coal, can be catalytically converted to useful products. Many of these reactions are conducted under harsh conditions, where the metal catalysts will rapidly sinter and lose activity. Overcoating is a methodology which preserves catalyst integrity under reaction conditions by depositing protective layers around the catalysts. Recently, we show that overcoating the metal nanoparticles with alumina using atomic layer deposition (ALD) will reduce the sintering and coking while the lifetime and reactivity of catalyst increase dramatically compared to the catalyst without ALD overcoating. It is believed that nano-sized pore (less than 2 nm) was formed during the calcination of ALD overlayer at high temperature. However, the mechanism of pore formation is still poorly understood due to the limited characterization technique.Understanding the mechanism of the pore formation and further controlling the pore size are crucial for the development of the ALD overcoated catalyst. Recently, we demonstrated that small angle X-ray scattering (SAXS) can be used to characterize these ALD overcoated catalysts. From SAXS analysis, the thermal treatment resulted in the formation of ~ 3.5 nm pores. Moreover, the evolution of pore size was monitored by in situ SAXS technique. The pore size increases with increasing annealing temperature. In this proposal, we aim to investigate the mechanism of pore formation during the calcination using in situ SAXS as well as wide angle X-ray scattering, to understand how the ramping rate, gas used, nature of supports and overcoated materials affect the formation of the pore.