Vanadium oxide-porous phosphate heterostructure catalysts for the selective oxidation of H2S to sulphur

Vanadium oxide–containing mesoporous materials, based on a surfactant expanded zirconium phosphate with silica galleries into the interlayer space, named porous phosphate heterostructure (PPH), were prepared by using TEOS and vanadium oxytripropoxide in n-propanol as sources of Si and V, respectively; with different Si/V molar ratios of 1, 2, 5 and 25; and calcining at 550 °C for 6 h. Using this method, vanadium can be partially incorporated to the structure of the gallery, but the surface area strongly decreases and the appearance of V2O5 crystallites increases when increasing the vanadium content. The catalysts were characterized by XRD, XPS, TEM, and Raman, and tested in the selective catalytic oxidation of H2S using a fixed bed reactor, at atmospheric pressure, at 180–260 °C. The catalysts with high contents of vanadium are very active at 200 °C, showing H2S conversions of 85–99%, with a high selectivity to elemental sulphur and with a low formation of SO2. Accordingly V2O5 crystallites can be proposed as active and selective although the catalytic behavior is related to the number of accessible V-sites in the surface of the catalyst.

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