Characteristics of particle size distribution functions of a supported metal catalyst during sintering

Abstract

It has been recognized for years that to arrive at an identification of the mechanism of thermal sintering of catalysts one requires detailed characterization of the metal particle size distribution (PSD) function during sintering. The purpose of this paper is to report the analysis performed on the existing PSDs and to show that the results provide further evidence that sintering at temperatures of 700/sup 0/C and below takes place by particle migrations and that during 800/sup 0/C sintering the atomic migration mechanism becomes operative. The analyses reported here are mainly concerned with fitting the existing PSDs to log-normal distribution functions (LNDF), and observing the behavior of the standard deviations of the PSD functions related to sintering time, sintering temperature, and the geometric mean average particle size. The results indicate that: (1) Nickel particles on a silica support follow a LNDF both in the as-reduced condition and after sintering at temperatures up to 800/sup 0/C; and (2) The values of the standard deviation of the particle size distribution functions increase with sintering temperature. The time-dependent increase of the standard deviation observed at the highest sintering temperature is a possible indicator of a change in sintering mechanism.