Behavior of pyrite as sulfur carrier for chemical looping decomposition of H2S into H2 and S

• Chemical looping decomposition of H 2 S enables the recovery of both H 2 and S. • Pyrite as a low-cost sulfur carrier with FeS 2 as active phase was first proposed. • Thermodynamic analysis, experiments and phase characterizations were conducted. • Property, temperature effect, stability and reaction mechanism were evaluated. • The presence of Al 2 O 3 and SiO 2 in pyrite enhance the stability of sulfur carrier. Direct decomposition of hydrogen sulfide into hydrogen and sulfur (H 2 S → S + H 2 ) enables production of clean H 2 with sulfur recovery. However, the reaction has the thermodynamics limit. Chemical looping decomposition of H 2 S is a novel technology using metal sulfides as sulfur carriers, which can break the thermodynamic limit and realize efficient conversion of H 2 S for H 2 and S production. Pyrite as a low-cost sulfur carrier was first proposed and its reaction behavior for chemical looping decomposition of H 2 S was evaluated. Thermodynamic analysis, experiments and phase characterizations (XRD, SEM-EDS and PSD) were conducted with key issues to be identified as: decomposition and sulfidation behavior of pyrite, effects of temperature, stability and reaction mechanism. The pyrite decomposition followed random nucleation with subsequent growth model ( G ( α ) = − I n ( 1 − α ) ) , with an activation energy of 67.556 KJ∙mol⁻¹. The pyrite as a sulfur carrier exhibited desirable stability during chemical looping cycles. The presence of Al 2 O 3 and SiO 2 in pyrite played a significant impact in the stability of the sulfur carrier by dispersing active substance and developing uniform porous structures within the solid particles. The work provided theoretical support basis for the rational design of highly-efficient sulfur carrier and enhancement of reaction process.