Investigation of Catalytic Reduction of Sulfur Dioxide with Carbon Monoxide over Zirconium Dioxide Catalyst for Selective Sulfur Recovery

Abstract

In this work, a ZrO2 catalyst was used to reduce SO2 using CO for the direct sulfur recovery process (DSRP), and a mechanistic investigation was performed. ZrO2 catalyst was prepared by a precipitation method. It was supposed that ZrO2 catalysts exhibit high activity in the SO2 reduction by CO at relatively high temperature because of their Lewis acidic sites and Brönsted acidic sites. In addition, the following mechanistic pathway could be suggested: (1) In the first step initialized by the redox mechanism, the ZrO2 catalyst was reduced by CO and then sulfate groups, which have the effect of improving the Lewis acidic sites and Brönsted acidic sites, were formed on the surface. (2) In the second step, elemental sulfur was produced by the movement of lattice oxygen between SO2 and the lattice oxygen vacancies of the ZrO2 catalyst having redox catalytic properties. (3) In the third step, COS was formed by the reaction of S + CO → COS. (4) In the fourth step, SO2 and COS were adsorbed and reacted on the surface of the ZrO2 catalyst having Lewis acidic and Brönsted acidic sites, and then the abundant amount of elemental sulfur was produced. Consequently, we would like to suggest the mechanistic pathway corresponding to the modified COS intermediate mechanism involving the redox mechanism.

Recovery of elemental sulphur via selective catalytic reduction of SO 2 over sulphided CoMo/γ-Al 2 O 3 catalysts

“…More specifically, the SO 2 is adsorbed by the catalyst support c-Al 2 O 3 while one molecule of CO reacts with a lattice sulphur atom in the active Co-Mo-S phases to produce one molecule of COS (intermediate) and leave behind a lattice sulphur vacancy on the surface of catalyst. The COS then reacts with SO 2 adsorbed on the catalyst surface, which has a lattice sulphur vacancy [24,25]. This means that COS plays an important role in SO 2 reduction.…”

“…It is speculated that COS was initially formed via the reaction between CO and lattice sulphur atoms on the surface of the catalyst (to create lattice sulphur vacancy) rather than the direct reaction between CO and SO 2 . It is known that COS is a more reactive reducing agent than CO in terms of the reduction of SO 2 to elemental sulphur [24,25]. Therefore, when temperature is below 350°C, the rate of COS formation is faster than that of COS-SO 2 reaction, which subsequently results in more COS being detected in gas product because not all the total COS formed can be COS-SO 2 consumed (COS-SO 2 reaction step is rate determining step).…”

Selective catalytic reduction of sulfur dioxide by carbon monoxide over iron oxide supported on activated carbon

“…Regarding mixed oxides, for ZrO 2 and perovskite LaCoO 3 catalyst, 95% conversion of SO 2 was achieved at 500 • C, which was higher than that over the Fe 2 O 3 /AC catalyst we employed in the present work. 1,19 Over the Fe 2 O 3 -only catalyst, SO 2 conversion was less than 20%, even at 450 • C. Therefore, Fe 2 O 3 /AC is thought to be one of the best catalysts for the catalytic reduction of SO 2 with CH 4 to elemental sulfur.…”

“…Sulfur dioxide is a toxic and corrosive sulfur compound that damages health, corrodes equipment, generates acid rain, and pollutes and acidifies the soil. 1,2 As recent environmental concern enforces more strict regulations of the emission of SO x , the treatment of SO 2 in flue gas has attracted increasing attention. Numerous flue gas desulfurization processes have been commercialized, and most of them are throwaway types in which alkaline materials react with SO 2 to form alkaline metal sulfate that is often stockpiled.…”

Highly Regioselective Oxybromination in an Aqueous System Using SBA‐15 Supported Sulfated Zirconia Catalyst

“…However, much less studies have been done on SZ as an oxidation catalyst. Recently, SZ is shown to give catalytic activity in the oxidation of CO 22 and selective methane bromination. 23 But when interacting with molecular oxygen, SZ is known to activate O 2 by electron-transfer to form superoxide.…”