Contents lists available at ScienceDirect Fuel Processing Technology journal homepage: www.elsevier.com/locate/fuproc Research article MoWFe based catalysts to the oxidative desulfurization of refractory dibenzothiophene compounds: Fe promoting the catalytic performance Marco A. Alvarez-Amparán ⁎ , Diego Guillén-Aguilar, Luis Cedeño-Caero ⁎ UNICAT, Departamento de Ingeniería Química, Facultad de Química, Universidad Nacional Autónoma de México, Ciudad de México 04510, Mexico ARTICLE INFO Keywords: Oxidative desulfurization Molybdenum-tungsten-iron based catalysts Ultra-low sulfur levels Advanced-catalysts for oxidative desulfurization Sulfur removal ABSTRACT The oxidative desulfurization (ODS) process is a potential technology to complement the actual hydro- desulfurization process to reach the ultra-low sulfur level in diesel fuels. In this work, oxides of MoWFe based catalysts (totally calcined and partially reduced) were prepared and tested in the ODS process to study the promoting effect of Fe species on the catalytic activity and the interactions between Mo, W and Fe. γ-Al 2 O 3 was used as catalytic support and H 2 O 2 as oxidant agent. The catalysts were characterized by temperature pro- grammed reduction (TPR), scanning electron microscopy (SEM-EDX), X-ray diffraction (XRD) and N 2 -physi- sorption. The characterization results shown a synergetic effect between Mo and W that improve the catalytic activity. Also, it was observed a promoting effect of Fe on W and Mo species improving the distribution of high- interaction Mo species and low-interaction W species which enhanced the ODS activity. The catalytic activity of MoWFe catalysts was higher than monometallic and bimetallic catalysts. It was reached the complete oxidation of DBT, 4-MDBT and 4,6-DMDBT in a simplified ODS system and a removal of 98% of sulfur compounds in a three-phase extraction-oxidation system. 1. Introduction Several technologies to remove sulfur from oil distillates have been studied to complement the conventional hydrodesulfurization (HDS), such as: adsorption [1], extraction [2], biodesulfurization [3], de- sulfurization using ionic liquids [4] and oxidative desulfurization [5,6]. Oxidative desulfurization (ODS) has great potential to complement the HDS process to reach the ultra-low sulfur levels in middle distillates (< 10 ppm S) because of ODS can remove the refractory sulfur com- pounds such as DBT and their alkylated derivatives (4-MDBT and 4,6- DMDBT) using an oxidant agent and a catalyst [7–9]. The ODS process can be performed in one or two steps. One step ODS process consists of the oxidation of sulfur compounds into the diesel fraction. In the two- step ODS process the sulfur compounds are firstly extracted to an ex- traction solvent and then the sulfur compounds are oxidized to the corresponding sulfone into the extraction solvent [10–12]. Two-step ODS process is also named extraction-oxidation process (EO), which is more efficient when this one is carried out in one equipment since thermodynamic equilibrium improve the ODS performance [13–16]. Heterogeneous ODS process has the advantage of allowing catalyst reuse due to the easier separation from the reaction system than homogeneous ODS process [10,11]. Heterogeneous catalysts to ODS process mainly have transition metals as active phases and oxides, mixed oxides or structured materials (TiO 2 , Al 2 O 3 , MgO, SiO 2 , Al 2 O 3 - MgO, Al 2 O 3 -SiO 2 , Al 2 O 3 -TiO 2 , activated carbons, zeolites or molecular sieves) are used as supports. Mo, Ti, V, W, Cu or Fe based catalysts have been tested in the ODS process with and without promoting elements [5,12,17,18]. Among these active phases Mo and W based catalysts have shown better catalytic activity than other metals [5,10–12,18] and it has been shown that the interaction between Mo and W improved the catalytic activity [19,20]. Fe as an additive or promoting element on ODS catalysts has shown adequate performance since Fe easily change its oxidation state due to its ability to donate or accept electrons in the valence band [19,21–24]. Although, it is important to mention that the effect of promoter elements on ODS catalysts has not always been ad- dressed or correctly discussed. Also, it is known that metal oxides in- teraction promotes particular structural and electrical characteristics such as, Lewis acidity or reduction capacity [13,19,20,25]. In this sense, it would be appropriate to know if the interaction between highly-active transition metals and promoter elements with redox characteristics (such as Fe) will improve the catalytic performance in the ODS process. In this research, we propose to evaluate the catalytic performance of a new MoWFe based catalyst in the ODS process and the interaction of the supported species. We propose the EO configuration in one step using H 2 O 2 as oxidant agent and acetonitrile (MeCN) as extraction https://doi.org/10.1016/j.fuproc.2019.106233 Received 21 August 2019; Received in revised form 30 September 2019; Accepted 2 October 2019 ⁎ Corresponding authors. E-mail addresses: marco.alvarez.amparan@outlook.com, ing_amparan@hotmail.com (M.A. Alvarez-Amparán), caero@unam.mx (L. Cedeño-Caero). Fuel Processing Technology 198 (2020) 106233 0378-3820/ © 2019 Elsevier B.V. All rights reserved. T