Interaction mechanism between CO and H2S over CuFe2O4 oxygen carrier during chemical-looping combustion: A DFT study

During the chemical-looping combustion process, CO as an important part of syngas and H2S as a common sulfur compound inevitably coexist in the fuel. Based on the density functional theory and periodic structure model, the interaction mechanism between CO and H2S over the O-defective CuFe2O4 surface was comprehensively investigated. The results show that the adsorption energies of adsorbates on the O-defective surface are in the order of S* (-205.42 kJ/mol) > HS* (-191.37 kJ/mol) > CO (-44.88 kJ/mol) > H2S* (-28.97 kJ/mol). CO adsorption over the O-defective surface is dominant as compared to H2S adsorption. The adsorption energies of CO in the presence of H2S, HS* and S* are -73.21, -255.98 and -105.35 kJ/mol, respectively. The adsorption strength of CO over the O-defective surface was enhanced in the presence of HS* or S*. The presence of CO* will greatly limit the H2S dehydrogenation process, especially for the second dehydrogenation step. The energy barriers of CO oxidation with the participation of H2S*, HS* and S* are 69.66, 51.42 and 14.19 kJ/mol, respectively. COS may be produced form the reaction between CO and S* with an energy barrier of 27.13 kJ/mol, following the Eley-Rideal reaction mechanism. CuFe2O4 oxygen carrier exhibits good anti-sulfur ability because the reaction of CuFe2O4 with CO and H2S kinetically prefers the CO oxidation pathway rather than the COS formation pathway.

Automated summary

The interaction mechanism between CO and H2S over the O-defective CuFe2O4 surface during chemical-looping combustion process was investigated. The results show that CO adsorption is dominant compared to H2S adsorption, and the presence of CO* limits the H2S dehydrogenation process. CuFe2O4 oxygen carrier exhibits good anti-sulfur ability.