Study on sulfur deactivation of catalysts for DMDS oxidation

- 0.3Pt10Cu/AlSi20 catalyst is active, selective and durable in DMDS oxidation.
- Less than 20% of silica is able to improve catalyst resistance against sulfur.
- PtO is the most optimal form of platinum in Pt-Cu catalyst for DMDS oxidation.

In the present research, an industrially aged Pt/Al2O3 catalyst was used as a basis for the study on the sulfur deactivation and the development of more resistant catalytic materials. The catalytic activities of both industrially and laboratory-aged materials in DMDS oxidation were studied in addition to characterization by XRD, XPS, FESEM, TEM and N2 adsorption. The industrial ageing induced a phase change from γ-Al2O3 towards θ-Al2O3, formation of aluminum sulfates and an increase in Pt particle size as well as a change in the oxidation state of Pt to a higher state. These changes caused an increase of 30 °C in the light-off temperature for DMDS oxidation. Accelerated ageing in the presence of SO2 and H2O vapor at 400 °C for 5 h decreased the activity of the Pt/Al2O3 at the same level than for the industrially aged catalyst even though smaller sulfur content and no sintering of γ-Al2O3 were observed. Pt sintering (10-20 nm) in both cases was observed. The XPS results confirmed the formation of new sulfate phases and the interaction between sulfur and the active phase as well as the support of the catalyst undergone accelerated ageing. After the accelerated ageing of copper-based catalysts, the 0.3Pt10Cu/Al2O3ǀ0.8SiO2ǀ0.2 catalyst showed an interesting resistance towards sulfur deactivation, as it was expected.

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