Direct Reduction of Sulfur Dioxide to Elemental Sulfur with Hydrogen over Sn−Zr-Based Catalysts

Abstract

We conducted the SO 2 reduction with H 2 over Sn-Zr-based catalysts for the direct sulfur recovery process. The reaction temperature was varied from 250 to 550°C while using SnO 2 -only, ZrO 2 -only, and SnO 2 -ZrO 2 (Sn/Zr ) 2/1) catalysts. The highest reactivity was obtained using the SnO 2 -ZrO 2 (Sn/Zr ) 2/1) catalyst at 550°C, for which the SO 2 conversion and sulfur selectivity were 98 and 55%, respectively. Also, the following mechanistic pathway was suggested: (1) The elemental sulfur is produced by the direct conversion of SO 2 according to the redox mechanism (SO 2 + 2H 2 f S + 2H 2 O). (2) The produced sulfur is partially converted into H 2 S with the hydrogenation (H 2 + S f H 2 S). (3) Finally, the Claus reaction proceeds through Lewis and Brönsted acidic sites (SO 2 + 2H 2 S f 3S + 2H 2 O). It was estimated that the lattice oxygen vacancies might be active sites for the redox mechanism and the Lewis and Brönsted acidic sites might be related to the pathway of the Claus reaction.

Major Advances and Challenges in Heterogeneous Catalysis for Environmental Applications: A Review

“…Sulphur recovery in these processes can also be achieved as reported by [99], who also proposed the removal pathway, i.e. elemental sulphur is created by the direct conversion of SO 2 , so the created sulphur is partially transformed into H 2 S with the hydrogenation, and the Claus reaction proceeds through the acidic sites.…”

“…Using this method, it is possible to simultaneously recover potentially toxic metals and utilize them as an efficient and valuable catalysts in environmental applications. [99] or WO x [100], can be used in the desulphurization of gases and oils. Moreover, various catalyst-supporters including γ-Al 2 O 3 , permutite, silica gel, and activated carbon were evaluated and tested as a means of enhancing catalytic activity of metal oxides [98].…”

Ni2P Nanoparticles Embedded in Mesoporous SiO2 for Catalytic Hydrogenation of SO2 to Elemental S

“…15 Han et al reported the synthesis and performance of a SnO 2 -ZrO 2 catalyst, which achieved SO 2 conversion of 98% and sulfur selectivity of 55% at 550 °C (SO 2 /H 2 mole ratio is 1/2; GHSV = 10,000/h). 16 These catalytic SO 2 reduction processes lead to the formation of elemental sulfur as the main target product and toxic H 2 S as the undesired byproduct (Tables S2 and S3). It is worthwhile to mention here that before the step of SO 2 reduction, these above catalysts need to go through a presulfide step to get the metal sulfide (MeS) as the active phase.…”

Reduction in Natural Gas Consumption in Sulfur Recovery Units through Kinetic Simulation Using a Detailed Reaction Mechanism

“…Several innovative technologies have been proposed for H 2 S utilization to produce hydrogen and syngas along with sulfur. These include a recently proposed AG2S technology, the simultaneous recovery of sulfur and syngas from acid gas, the enhanced production of hydrogen from acid gas by process modifications and by chemical and photochemical methods, and the catalytic conversion of SO 2 to sulfur using carbon beds and Sn–Zr-based catalysts . However, the Claus process remains the most widely used method for sulfur production.…”