Development of heterogeneous catalysts for the conversion of H₂S to value-added products

Physico-chemical and redox properties were characterised using ICP-OES, N₂ physisorption, XRD, Raman, FESEM, TEM, EDS and H₂-TPR. Catalytic testing under 500 ppm H₂S, 200 °C, a GHSV of 500,000 h⁻¹, and an O₂:H₂S ratio of 3 showed that both H₂S conversion and SO₂ selectivity increased with vanadium loading. At 20 wt.% vanadium loading, SO₂ selectivity reached 93% for 20V–Al₂O₃, 67% for 20V–Y–TiO₂R, and 33% for 20V–CeO₂.These results emphasise the importance of support type, metal loading, and dopant effects.

To further enhance redox behaviour and selectivity, nanostructured supports and active phases were synthesised via hydrothermal methods. This method enabled precise morphology control, producing vanadia nanorods (VNRs) with diameters ranging 19.7– 80.0 nm, and ceria nanorods (CeNRs) ranging 35– 54 nm. Nanostructured catalysts were prepared using physical mixing to preserve morphology and structural integrity.

Catalysts such as 10VNR–Al₂O₃, 20VNR–CeO₂, and 20VNR–CeNR demonstrated SO₂ selectivity exceeding 80%, even under CO₂-rich conditions and reduced GHSV of 250,000 h⁻¹, confirming their superior stability, adaptability, and structural robustness compared to conventional counterparts. In parallel, a Response Surface Methodology (RSM) combined with a Central Composite Design (CCD) was used to model the influence of operational parameters and determine the optimal conditions for SO₂ yield. 10V-Al2O3 was utilised as a model catalyst.

A second-order polynomial regression model identified temperature as the most influential factor, while H₂S concentration had a negligible impact within the studied range. Optimal yields (>84%) were achieved at 260–280 °C and GHSV between 100,000 and 130,000 h⁻¹. In summary, this thesis demonstrates that ceria-based materials, especially those with enhanced surface area and oxygen mobility, are highly suitable for H₂S abatement via selective oxidation at low temperatures.

The integrated experimental–statistical approach adopted provides both mechanistic insight and process design guidance for the development of scalable, efficient, and robust desulfurization technologies.<br><br><i>Thesis is embargoed until 31 December 2031.</i><br>