Abstract
Hydrodesulfurization (HDS) is a widely used process currently employed in petroleum refineries to eliminate organosulfur compounds in fuels. The current hydrotreating process struggles to remove organosulfur compounds with a steric hindrance due to the electronic nature of the current catalysts employed. In this work, the effects of adding chelating ligands such as ethylenediaminetetraacetic acid (EDTA), citric acid (CA) and acetic acid (AA) to rhodium (Rh) and active molybdenum (Mo) species for dibenzothiophene (DBT) HDS catalytic activity was evaluated. HDS activities followed the order of RhMo/ɣ-Al2O3 (88%) > RhMo-AA/ɣ-Al2O3 (73%) > RhMo-CA/ɣ-Al2O3 (72%) > RhMo-EDTA/ɣ-Al2O3 (68%). The observed trend was attributed to the different chelating ligands with varying electronic properties, thus influencing the metal–support interaction and the favorable reduction of the Mo species. RhMo/ɣ-Al2O3 offered the highest HDS activity due to its (i) lower metal–support interaction energy, as observed from the RhMo/ɣ-Al2O3 band gap of 3.779 eV and the slight shift toward the lower BE of Mo 3d, (ii) increased Mo-O-Mo species (NMo-O-Mo ~1.975) and (iii) better sulfidation of Rh and MoO in RhMo/ɣ-Al2O3 compared to the chelated catalysts. The obtained data provides that HDS catalytic activity was mainly driven by the structural nature of the RhMo-based catalyst, which influences the formation of more active sites that can enhance the HDS activity.
Highlights
Deleterious refractory organosulfur compounds in fuel oils have contributed to SOx emissions [1,2]
The scientific novelty of the research is to arrive at a fundamental understanding of the nature of the sulfur tolerance of the supported Rh-Mo catalysts, and to offer clarification of the synergetic effect of chelating ligands such as ethylenediaminetetraacetic acid (EDTA), citric acid (CA) and acetic acid (AA) on the individual metal, the Rh and the Mo components in the catalytic hydrodesulfurization of DBT
The analysis results, including the detailed binding energies and the sulfidation degree of the Mo species obtained by the deconvolution, are shown in Table S1, and the different phase compositions of the catalysts are calculated from the area of the deconvoluted peaks
Summary
Deleterious refractory organosulfur compounds in fuel oils have contributed to SOx emissions [1,2]. The scientific novelty of the research is to arrive at a fundamental understanding of the nature of the sulfur tolerance of the supported Rh-Mo catalysts (chelated and unchelated RhMoS/G-Al2O3), and to offer clarification of the synergetic effect of chelating ligands such as ethylenediaminetetraacetic acid (EDTA), citric acid (CA) and acetic acid (AA) on the individual metal, the Rh and the Mo components in the catalytic hydrodesulfurization of DBT. (4) The observed catalytic results were ascribed to the introduction of different ligands, increasing the metal–support interaction and increasing the e-charge transfer from the valance band Rh 4d orbital to the conduction band of the Mo species This led to the excessive weakening of the Mo-S bond by inhibiting the absorption of sulfur (S) compound (DBT) on the active sites, leading to a reduced activity.
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