Microstructural Evolution of γ-Alumina-Supported Rh upon Aging in Air
作者： Zara Weng-Sieh , Ronald Gronsky , Alexis T. Bell
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摘要: Abstract Microstructural changes in alumina-supported rhodium catalystsduring aging air at high temperatures were investigated usinga combination of high-resolution transmission electronmicroscopy, X-ray photoelectron spectroscopy (XPS), and X-raydiffraction. Both constituents, particles support, undergostructural during thermal aging. With increasing agingtemperature time, the support transforms from γ- toα-alumina, phase change is accelerated by thepresence rhodium. The rhodium, present initially as10-A-diameter metal particles, undergoes oxidation with theformation a variety oxide phases, depending on thetemperature which has occurred. At 500°C, highlydispersed, raft-like structures are observed. Continued atthis temperature results coarsening these toform three-dimensional high-temperature,high-pressure (HT, HP) orthorhombic Rh 2 O 3 . 850°C, causes severe coalescence HT, HP while 1000°C, RhO observed together large Ahigh binding energy (near 309 eV) using XPSfollowing all treatments may be attributed to eitherthe or 4+
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