In situanomalous small-angle X-ray scattering from metal particles in supported-metal catalysts. II. Results

Abstract

Information about the metal phase in a supported-metal catalyst can be obtained using anomalous small-angle X-ray scattering (ASAXS). The difference between the scattering profiles for SAXS at two different wavelengths near the metal's absorption edge is essentially the scattering of the metal alone. Novelin situASAXS measurements are made on mordenite impregnated with platinum metal while the temperature and composition of gas in the sample cell are changed. Measurements are made 62 times during treatment of the catalyst. The metal particles are assumed to be randomly distributed spheres withN(R)dR= number of spheres with radii betweenRandR+ dR. It is found thatN(R) is always a monotonically decreasing function ofR, and that the average value ofR, obtained fromN(R), decreases by a factor of two over the time (approximately 6 h) for which the system is observed.