A solid thermal and fast synthesis of MgAl-hydrotalcite nanosheets and their applications in the catalytic elimination of carbonyl sulfide and hydrogen sulfide

Abstract

A variety of MgAl-layered double hydrotalcites (MA-LDHs-x) with different Mg/Al molar ratios (1 : 3–5 : 1) were prepared by a novel solid-thermal approach. The obtained MA-LDH-x catalysts were characterized by various techniques. These results confirm the successful preparation of MA-LDHs-x with a high degree of crystallinity, large BET surface areas, and unique nanosheet structures with controllable hexagonal morphology. In addition, MA-LDHs-x possess tunable OH⁻ group contents, which could be correlated with the molar ratio of Mg/Al. As a result, the MA-LDH-x catalysts exhibited better catalytic performance in carbonyl sulfide (COS) hydrolysis (COS conversion: 100% at 130 °C for MA-LDHs-3 : 1 vs. 38% at 130 °C for commercial Fe₂O₃) and H₂S selective oxidation (H₂S conversion: 100% at 150 °C for MA-LDHs-3 : 1 vs. 41% at 150 °C for commercial Fe₂O₃) than commercial desulfurization catalysts. Superior activities found in MA-LDH-x catalysts were attributed to their controllable 2D nanosheet structures, and the unique structural characteristics enhance the mass transfer of guest molecules. Notably, the exposed OH⁻ base sites of MA-LDHs-x efficiently activate the acid COS and H₂S, which facilitate the COS hydrolysis to H₂S, and the selective H₂S oxidation to elemental sulfur.