Abstract
The surface region of a commercial hydrodesulphurization (HDS) catalyst (Harshaw, HT-400) was chemically analyzed, prior to and following hydrogen sulphide exposure, by X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), scanning electron microscopy (SEM) and scanning Auger microscopy (SAM). XPS analysis of this sulphided catalyst indicated nearly total molybdenum conversion to the sulphide state. The surface composition of the catalyst was determined semi-guantitatively by XPS and AES. Surface and bulk chemical analysis agreed guite well for cobalt, aluminum and oxygen. The surface molybdenum level was nearly 3 times larger than expected indicating preferential surface siting. Several Auger point analyses (0.2 pm spot) revealed that molybdenum, cobalt and sulphur are not uniformly dispersed on the catalyst. SAM maps verified that sulphur is locally concentrated in areas on the surface enriched in molybdenum and cobalt.
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