(159c) Convert Hydrogen Sulfide to Hydrogen By Iron Sulfide Via a Novel Thermo-Catalytic Sulfur Capture Process | AIChE

(159c) Convert Hydrogen Sulfide to Hydrogen By Iron Sulfide Via a Novel Thermo-Catalytic Sulfur Capture Process


Chen, Y. Y. - Presenter, The Ohio State University
Nadgouda, S., The Ohio State University
Qin, L., The Ohio State University
Fan, L. S., The Ohio State University
Hydrogen sulfide (H2S) is a by-product of natural gas sweetening and crude oil desulphurization, and it is a potent pollutant in environment, human health and many industrial activities. The use of liquid solvent absorption along with Claus process that convert H2S to H2O is the current commercial process. However, such process requires special solvents for selective H2S absorption and a large input of energy and several process units to convert H2S to H2O and sulfur. As hydrogen (H2) is one of the most extensively used chemical intermediates in industry and an option of clean energy, its global demand keeps on rising. An advanced H2S processing technology that can convert H2S to H2 and elemental sulfur is therefore highly desired.

In this work, we adopt the concept of chemical looping and develop a thermo-catalytic sulfur capture (TCSC) process in a simple two-step manner: sulfidation and regeneration. In the sulfidation step, iron sulfide (FeSx) reacts with H2S to produce H2 while it is converted to a higher sulfidation state (FeSy, x<y) by capturing sulfur. The captured sulfur is then released by passing an inert gas like nitrogen (N2) at a higher temperature than the sulfidation reactor in the regeneration step, where FeSx is regenerated. Therefore, the net result is production of H2 and sulfur from H2S. The application of this technology reduces the number of processing units drastically as compared to the existing methods, and also produces H2 which improves the heating value of the gas stream. However, the reaction kinetics of pure FeSx with H2S were found to be slow, and methodologies to improve its reactivity becomes key to the success of this process. First-principles density functional theory (DFT) simulations were performed to unravel the reaction mechanism of H2S on FeSx. DFT simulations further pointed out that using molybdenum (Mo) as a dopant can modify the surface electronic structure significantly, and hence lower the energy barrier of the rate-limiting step substantially. The simulation results were validated in fixed bed experiments by comparing the H2S conversion between FeSx and Mo-doped FeSx under the same operating conditions, where Mo-doped FeSx indeed shows superior reactivity. Findings from this study would pave a way for further improvement of H2S separation technology.