Phosphorus promoted WS2/Al2O3 catalysts studied by transmission electron microscopy

A series of WS₂/Al₂O₃ catalysts containing a varied amount of phosphorus (0.0,2.5 and 6.0 wt% P₂O₅), sulfided at two different temperatures (873 and 1073 K), were studied by means of high-resolution transmission electron microscopy (HRTEM). The stacking of (002) layers in the WS₂-2H crystallites of the rag structure increases with the addition of phosphorus, whereas its length is kept almost constant. At high sulfidation temperatures phosphorus shows a stabilizing effect on the catalysts by retarding the stacking growth of WS₂ crystallites. Additionally, an aluminum phosphate crystalline phase is identified in the phosphorus promoted catalysts.