Sulfur Evolution Reaction during Reduction of SO₂ with CO over Carbon Materials

Abstract

To develop a new method to recover elemental sulfur from the desulfurization process, a study on the sulfur evolution mechanism during the reduction of SO2 with CO over carbon was carried out. Thermodynamic equilibrium calculations showed that the elemental sulfur, as well as CO2, is the primary product of SO2 reduction with a CO/SO2 ratio of 2. Carbonyl sulfide (COS), instead of elemental sulfur, became the primary S-containing product with a CO/SO2 ratio of 3. Moreover, it decomposed to CO and elemental sulfur at temperatures above 500 °C. Experimental results showed that during the CO–SO2 reaction over carbon materials, COS was formed as a byproduct in the gaseous phase and elemental sulfur was generated following a COS intermediate mechanism. In the solid phase, SO2 reacted with the carbon surface to form oxidized S-containing compounds and these compounds were reduced by CO. COS did not reduce the oxidized S-containing compounds but combined with the carbon matrix to form reductive compounds. The abundant pore structure of the carbon surface was beneficial for SO2 reduction, as it enhanced the generation of oxidized S-containing compounds. Moreover, high Fe2O3 content improved the reactivity due to the formation of metallic sulfides.

NOx Adsorption Mechanism of Coal-Based Activated Carbon Modified with Trace Potassium: In Situ DRIFTS and DFT Study

“…Thus, SO 2 would be adsorbed onto the surface of carbon-based materials and transform into sulfates. The sulfates occupy the active NO x evolution sites, which can inhibit the adsorption process to some extent, as the binding ability between the SO 2 molecules and the carbon framework is stronger …”

“…The sulfates occupy the active NO x evolution sites, which can inhibit the adsorption process to some extent, as the binding ability between the SO 2 molecules and the carbon framework is stronger. 46…”

Enhanced activity and sulfur resistance of Cu- and Fe-modified activated carbon for the reduction of NO by CO from regeneration gas

“…COS is formed by the reaction between elemental sulfur (S) and CO (S-CO reaction), 57 and S is produced by the reaction of SO 2 and CO (SO 2 -CO reaction). 58 These two side reactions will consume the adsorbed CO. AC-Fe-H has the highest amount of COS, followed by AC-H and AC-Cu-H, indicating that the formation of COS tends to occur on the oxygen-containing functional groups. Fe sites promote the formation of COS, and Cu sites inhibit the formation of COS. AC-Fe-H exhibits high activity under an SO 2 atmosphere with a large amount of COS formed, indicating that the S-CO reaction on AC-Fe-H consumes S and weakens the deposition of S, which will be analyzed in the following characterization.…”

Roles of the Comproportionation Reaction in SO2 Reduction Using Methane for the Flexible Recovery of Elemental Sulfur or Sulfides

“…Nonferrous smelting industries, which use sulfide ores, are now major sources of SO 2 , typically containing 1–10 wt % sulfur. , Although a portion of SO 2 can be converted to produce sulfuric acid (H 2 SO 4 ), this low-value product is challenging to store and transport due to its bulkiness. In addition, some SO 2 is scrubbed into wastewater, forming hard-to-recycle waste acids or salts, leading to resource wastage and pollution. , In contrast, adsorbing and regenerating SO 2 into highly concentrated or liquid SO 2 has become an established sulfur recovery method using ionic liquids, deep eutectic solvents, organic amines, and Na 2 SO 3 . − Moreover, reducing highly concentrated SO 2 to S 8 can not only eliminate pollution concerns but also yield valuable sulfur resources for industrial applications and energy storage. − …”