Title : Formation of Fe(III)-S and electron-deficient effect iron-based catalysts and its promotion for DBT hydrodesulfurization
Nowadays, production of ultra clean fuels is required because of the restricted governmental regulations that all over the world so as to protect human health and environment. The S and N compounds are the major environmental pollutants in crude oil, and the hydrogenation process is the primary removal method. The development of novel active phase HDS catalysts to replace the expensive and low-reserve conventional active phases, such as precious metals and cobalt molybdenum, to counteract the current state of cheaper oil production price. In the previous work, iron sulfide dispersed on a support surface with zinc as promoters have been verified for superior desulfurization effects. However, there is still a certain gap compared to the hydrogenation catalyst of the conventional active component. Electronic structure tuning is an effective strategy to activate transition metals. In this study, silica-promoted γ-Al2O3-supported Fe-based hydrodesulfurization catalysts of Fe species with electron loss were successfully prepared by transferring electrons from Fe to Si. The characterization results showed that the Fe-based hydrodesulfurization catalyst with the addition of silica modulated the structure and properties of the active metal, which not only improved the degree of sulfidation of the active metal but also promoted the generation of Fe(III)-S. The hydrodesulfurization rate of dibenzothiophene showed a remarkable rise from 38.4 to 83.2% at 673 K. Importantly, the formation of Fe(III)-S greatly stretched the bond length of Fe-S bonds, exhibiting an increase of approximately 21%, this facilitating the generation of coordinatively unsaturated active site. Finally, the HDS reaction performance of the Fe-based hydrodesulfurization catalysts was mainly influenced by the Fe(III)-S/Fe(II)-S ratio, with the most significant enhancement in the direct desulfurization reaction path. The results of this study provide a promising approach for the design and development of environmentally friendly and economical Fe-based catalysts in the field of clean fuels.
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