Efficient hydrodesulfurization catalysts based on Keggin polyoxometalates

• HDS pre-catalysts prepared via polyoxometalate (POM) route retain the POM structure and acidity.
• The structure and acidity lost upon sulfidation to form HDS active phase(s).
• HDS activity increases in the series of supports: SiO2 < TiO2 < γ-Al2O3.
• POM-based CoMo catalyst more active and selective in thiophene HDS than industrial counterpart.

Bulk and supported hydrodesulfurization catalysts based on Mo and W and containing Co or Ni as promoters and phosphorus as a modifier are prepared through the polyoxometalate route using Keggin type phosphomolybdates and phosphotungstates and tested in the HDS of thiophene at 350–400 °C and 1 bar pressure. The corresponding oxidic pre-catalysts retain intact Keggin structure of the parent polyoxometalates and possess Brønsted and Lewis acidity. In the course of sulfidation, the oxidic pre-catalysts transform into an active sulfidic phase with the loss of Keggin structure and catalyst acidity. Catalyst activity increases in the order of supports: SiO2 < TiO2 < γ-Al2O3. CoMoP/γ-Al2O3 catalyst prepared through the polyoxometalate route shows higher HDS activity and butene selectivity than industrial catalyst of comparable composition. The results indicate that polyoxometalate catalyst preparation route can be considered a performance enhancement methodology for HDS catalysis.

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