| Fe2O3is widely used as a dry desulfurization sorbent to remove sulfur species from syngas. However, its stability and regeneration are poor. The deeply understanding of the interaction between H2S and the desulfurizer, the regeneration of desulfurizer in the O2atmosphere, and the influence of doping metal into desulfurization sorbent on the desulfurization are crucial to improve the property of the desulfurizer.In this study, the desulfurization gas-solid model is constructed, and then he desulfurization mechanism between Fe2O3and H2S is obtained by using the density functional theory (DFT) calculations. Subsquently, based on the model of doping desulfurizer, the influence of doping the second metal on the dissociation of H2S is investigated. Furthermore, the atom vacancy on the desulfurizer surface can effect the desulfurization, which has been studied based on the model of the vacancy surface. In addition, the regeneration machnism of the surfurized α—Fe2O3surface in the O2atmosphere is obtained based on the constructed gas-solid model. The thermodynamics and dynamic mechanisms of catalytic conversion and desulfurization are illuminated at the electrons-molecular level. Main conclusions of this study are as follows: 1. For the desulfurization between H2S and the Fe2O3desulfurizer, there are mainly two paths, the formation of H2and H2O, respectively. The study of dynamic demonstrates that:two paths are competitive. During the desulfurization, Fe2O3plays two parts. On one hand, the Fe2O3plays a role of catalyst in the dissociation process of H2S leading to the formation of H2. On the other hand, in the forming H2O path, it mainly acts as one reactant participating in the reaction. Two H atoms seizure the surface O atom on the Fe2O3desulfurizer surface, and S atom fills into the O vacancy site simultaneously.2. During the desulfurization, the two paths lead to two surfirized surfaces formed. In the forming H2path, S atom adsorbed at the top site of surface Fe atom which is called as "S-adsorbed surface"; while in the H2O path, the surface O atom is suffered from the substitution by S atom and leading to the degrade of desulfurizer which is called as "S-contained surface"3. The processes of H2S decomposing into S/2H are the common experiencing steps during the desulfurization, no matter which products of H2and H2O are generated. The formation of "S-contained surface" surface leads to the increment of the energy barrier for the H2S dissociation on desulfurization sorbent surface, which is not beneficial to the desurfurization. What’s more, the calucation results show that doping Co, Cu and Zn metals respectively into the Fe2O3desulfurization sorbent could reduce the energy barrier of H2S dissociation, which is benifical to the desulfurization.4. The presences of atom vacancy on the surface always play an important role in the desulfuration. The activation energy of H2S dissociation on the Fe vacancy surface is lower than that on the perfact surface, which is beneficial to the desulfurization. However, the presence of O vacancy leads to the disappearance of metal active site on the surface, which is bad for the desulfurization.5. O2Not only can regenerate the desulfurizer, but also can repair the O vacancy on the surface. Two competitive regeneration paths exist on each sulfurized surface. And both the rate-determining steps are the dissociation of O2. Therefore, any methods which could result in the dissociation of O2dissociate easy are beneficial to the regeneration. Moreover, the reparation of O vacancy on the surface is easy under the O2atmospherre, which is beneficial to the propertities of the desulfurizer. |
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