Catalytic H₂S Conversion and SO₂ Production over Iron Oxide and Iron Oxide/γ-Al₂O₃ in Liquid Sulfur

Abstract

A stirred-glass autoclave containing liquid sulfur and solid iron oxide catalyst was used to study low-tonnage sulfur recovery from H2S-containing gas streams. The objectives were to test the feasibility of using both liquid sulfur as a reaction medium and iron oxide as a direct oxidation catalyst for prolonged H2S conversion. Using a 1.60% H2S and 0.80% O2 (balance N2) feed gas, fresh iron oxide acted primarily as a scavenger for bulk H2S removal from the inlet gas stream. Following the scavenging phase, the steady-state iron oxide/sulfide was able to maintain low catalytic activity (30% conversion). The steady-state catalyst did, however, have a strong ability to generate significant amounts of SO2 in the presence of inlet feed O2. Data showed that this SO2 production resulted from the oxidation of the liquid sulfur over the steady-state iron oxide/sulfide. The rate of SO2 formation was shown to be directly proportional to the concentration of O2 in the inlet feed gas. Although H2S conversions over steady-state iron oxide/sulfide ended up being lower than expected, the ability to strictly control the amount of SO2 generated from the system was advantageous. By incorporating γ-Al2O3 into a liquid sulfur reactor containing steady-state iron oxide/sulfide, the dual-catalyst system achieved 97% conversion of the H2S to elemental sulfur.