Evaluation of Claus Catalysts Using a Combination of Scanning Electron Microscopy and Electron Spectroscopy for Chemical Analysis

The Claus reaction is widely used to convert H₂S from natural gas and refinery to elemental sulfur. The results of SEM and ESCA studies of the morphology and chemical analysis of the fresh and spent Claus catalysts before and after regeneration were presented. The spent catalyst contained several distinct phases, indicating some contaminants. Also, the SEM micrographs showed coke lay-down on the surface which affects catalyst efficiency. EDS x-ray analysis showed the presence of carbon, iron, and sulfur in alumina inanity. The elemental sulfur segregated towards the interior bulk, while carbon was found mostly near the surface. Iron deposition was also found near the surface of the spent catalyst. ESCA analysis showed that coke was a major contaminant and some of the sulfur were present in the sulfate form in addition to elemental sulfur. Examination of the regenerated catalyst showed removal of all contaminants by chemical treatment and nearly 90% by air-oxidation. The selective removal of contaminants resulted from a combination of chemical treatment followed by calcinations at 350°C. Adjusting acid concentration and temperature condition made it possible to extract contaminants from catalyst surface. However, the oxidative burn-off regeneration treatment did not remove iron oxide contaminant from the surface.