Construction of bifunctional 3-D ordered mesoporous catalyst for oxidative desulfurization

A Novel Ternary Catalyst PW4@MOF-808@SBA-15 for Deep Extraction Oxidation Desulfurization of Model Diesel

In this work, a novel heterogeneous catalyst consisting of peroxophosphotungstate, microporous MOF-808, and mesoporous SBA-15 was synthesized, characterized, and used to remove sulfides from model fuel. The prepared material, PW4@MOF-808@SBA-15, exhibits excellent catalytic activity with a desulfurization efficiency of 99.8% in 60 min for multicomponent simulated fuel, and the desulfurization rate can reach more than 90% after ten consecutive cycles. The excellent catalytic activity and reusability are attributed to the hierarchically porous hybrid material MOF-808@SBA-15, which can effectively encapsulate PW4 and provide a site for the oxidation of sulfides.

Electronic Phosphide-Support Interactions in Carbon-Supported Molybdenum Phosphide Catalysts Derived from Metal-Organic Frameworks

Interfacial interaction in carbon-supported catalysts can offer geometric, electronic, and compositional effects that can be utilized to regulate catalytically active sites, while this is far from being systematically investigated in carbon-supported phosphide catalysts. Here, we proposed a novel concept of electronic phosphide-support interaction (EPSI), which was confirmed by using molybdenum phosphide (MoP) supported on nitrogen-phosphorus codoped carbon (NPC) as a model catalyst (MoP@NPC). Such a strong EPSI could not only stabilize MoP in a low-oxidation state under environmental conditions but also regulate its electronic structure, leading to reduced dissociation energy of the oxygen-containing intermediates and enhancing the catalytic activity for oxidative desulfurization. The removal of dibenzothiophene over the MoP@NPC was as high as 100% with a turnover frequency (TOF) value of 0.0027 s-1, which was 33 times higher than that of MoP without EPSI. This work will open new avenues for the development of high-performance supported phosphide catalysts.

Studying the mechanism and kinetics of fuel desulfurization using CexOy/NiOx piezo-catalysts as a new low-temperature method

In order to advance desulfurization technology, a new method for excellent oxidative desulfurization of fuel at room temperature will be of paramount importance. As a novel desulfurization method, we developed piezo-catalysts that do not require adding any oxidants and can be performed at room temperature. A microwave method was used to prepare CeO₂/Ce₂O₃/NiO_x nanocomposites. Model and real fuel desulfurization rates were examined as a function of synthesis parameters, such as microwave power and time, and operation conditions, such as pH and ultrasonic power. The results showed that CeO₂/Ce₂O₃/NiO_x nanocomposites demonstrated outstanding piezo-desulfurization at room temperature for both model and real fuels. Furthermore, CeO₂/Ce₂O₃/NiO_x nanocomposites exhibited remarkable reusability, maintaining 79% of their piezo-catalytic activity even after 17 repetitions for desulfurization of real fuel. An investigation of the mechanism of sulfur oxidation revealed that superoxide radicals and holes played a major role. Additionally, the kinetic study revealed that sulfur removal by piezo-catalyst follows a second-order reaction kinetic model.

Combined Heterogeneous Catalyst Based on Titanium Oxide for Highly Efficient Oxidative Desulfurization of Model Fuels

In this work, new heterogeneous Mo-containing catalysts based on sulfonic titanium dioxide were developed for the oxidation of sulfur-containing model feed. The synergistic effect of molybdenum and sulfonic group modifiers allows for enhancing catalytic activity in dibenzothiophene oxidative transformation, and a strong interaction between support and active component for thus obtained catalysts provides increased stability for leaching. For the selected optimal conditions, the Mo/TiO₂-SO₃H catalyst exhibited 100% DBT conversion for 10 min (1 wt % catalyst, molar ratio of H₂O₂:DBT, 2:1; 80 °C). Complete oxidation of DBT in the presence of the synthesized catalyst is achieved when using a stoichiometric amount of oxidizing agent, which indicates its high selectivity. The enhanced stability for metal leaching was proved in recycling tests, where the catalyst was operated for seven oxidation cycles without regeneration with retainable activity in DBT-containing model feed oxidation with hydrogen peroxide under mild reaction conditions. In 30 min of the reaction (H₂O₂:S = 2:1 (mol), 0.5% catalyst, 5 mL of acetonitrile, 80 °C), it was possible to reduce the content of sulfur compounds in the diesel fraction by 88% (from 5600 to 600 ppm).

Influence of Water on Noncatalytic Oxidative Desulfurization of High-Sulfur Straight-Run Oil Fractions

The noncatalytic oxidative desulfurization process of straight-run kerosene and diesel fractions with high sulfur contents due to their treatment with air without using expensive catalysts and strong oxidants is considered. The research was carried out in a periodic mode in a bubble-type reactor with a volume of 1 × 10^-3 m³ under the following conditions: 180-200 °C; 2.5-3.0 MPa; the process lasted for 20-30 min; the air/raw material ratio was 1.6-2.2 m³/min per 1 m³ of raw material. The process can be used to obtain industrial jet fuels and diesel fuel components with good lubricating properties. The possibility and expediency of carrying out the process in the presence of water have been studied. The ratio of water/raw materials (vol.) varied from 0:1 to 2:1. It was proven that the water presence in the reaction medium has a positive effect on the studied process and decreases the oxidation intensity of hydrocarbon medium by 2-4 times. This is due to both the slowing of oxidation reactions by water during peroxide decomposition and chain growth and branching and the partial change in chemical oxidation with the formation of phenols and/or tertiary alcohols, which are inhibitors of oxidation reactions. On the other hand, water has almost no effect on the removal degree of sulfur compounds.

Scale-up reactivation of spent S-Zorb adsorbents for gasoline desulfurization

Reactivating and recycling spent S-Zorb adsorbents reduce fresh adsorbents consumption and hazardous wastes emissions. Though the spent adsorbents have been successfully reactivated in the laboratory, a pilot-scale practice is indispensable before the industrial production. Herein, the reactivation of spent adsorbents was performed at laboratory (1.0 L), middle (10 L) and pilot (3000 L) scale, respectively. The inert Zn₂SiO₄ and ZnS over the spent adsorbents are recovered to active ZnO, and the NiS is transformed into NiO. There is almost no amplification effect in pore structure and acidity of the reactivated adsorbents, while NiO particle size reduces slightly with the reactivation scales. The computational fluid dynamic simulation indicates that enhanced contact between spent adsorbents and acid/alkaline reagents at larger scale account for the smaller NiO particle. It provides more hydrogenolysis centers for CS bonds breakage after reduction, increasing initial desulfurization activity. More importantly, the adsorbent reactivated at pilot scale exhibits comparable activity to the fresh one in gasoline desulfurization. The sulfur content in the outlet decreases to less than 10 μg g^-1 from 1 h of reaction. Thus, the reactivation of spent S-Zorb adsorbents is successfully scaled up to the pilot scale, accelerating industrial practice in recycling the spent adsorbents.

Enhancing the biodesulphurization capacity of Rhodococcus sp. FUM94 in a biphasic system through optimization of operational factors

The biodesulfurization activity of bacteria through the 4S pathway in aqueous-oil emulsions is affected by various operational factors. These factors also demonstrate interacting effects that influence the potential for field applications of biodesulfurization technology and can solely be deciphered through multi-variable experiments. In this study, the effects of the influential factors and their interactions on the desulfurizing activity of a newly identified desulfurizing bacterium, Rhodococcus sp, FUM94 were quantitatively investigated. The capacity improvement achieved through optimized values obtained in this study is significant due to its simple implementation to large scale processes. This is the most simple and the most cost-effective way to scale-up a biodesulfurization process.Using response surface methodology (RSM). Optimum values of the factors were identified with the objective of maximizing biodesulfurization activity. Results revealed that the desulfurization activity of the biocatalyst increased from 0.323 ± 0.072 to 46.57 ± 4.556 mmol 2-Hydroxybiphenyl (kg dry cell weight)^-1 h^-1 at the optimized conditions of 6 h reaction time, 2 g.L^-1 biocatalyst concentration, 0.54 mM (100 ppm) dibenzothiophene (DBT) concentration (sulfur source), and 25% oil phase fraction. Desirability analysis proved that the selected conditions are the most desirable combination of factors (desirability value = 0.896) to achieve the highest biodesulfurization activity of the biocatalyst. A comparison between the biodesulfurization capacity achieved in this study and the capacities reported in similar studies published in the past two decades revealed that biodesulfurization under optimized operational conditions outperforms previously proposed techniques.

Catalytic decomposition of dibenzothiophene sulfone over K-based Oxides supported on alumina

A series of K-based oxides catalysts supported on aluminium oxide (γ-Al2O3) with different surface area were synthesized by impregnation method and investigated in decomposition of sulfones from oxidized diesel fuel....

Roles of the structural defects and the combined acidity of H3PW12O40/Zr-MCM-41 catalysts in ultralow sulfur diesel production

This work contributes to the production of ultralow-sulfur diesel using phosphotungstic acid immobilized on Zr-MCM-41 catalysts containing structural defects and combined acidity.

A new phase transfer nanocatalyst NiFe2O4-PEG for removal of dibenzothiophene by an ultrasound assisted oxidative process: kinetics, thermodynamic study and experimental design

In this study, NiFe₂O₄–PEG, an effective nanocatalyst was synthesized via a hydrothermal method using different PEG concentrations and synthesis times. The synthesized nanocatalyst was used in the ultrasound assisted oxidative desulfurization (UAOD) of model fuels (e.g. n-hexane and dibenzothiophene (DBT)) for the first time. The nanocatalyst was then characterized by XRD, FTIR, BET, SEM, VSM and TEM analyses. In addition, central composite design was used to evaluate the effective variables on the UAOD process. The optimal values of effective factors such as catalyst dose, oxidant amount, irradiation time and ultrasonic power to maximize of the percentage of sulfur removal were 0.149 g, 15 mL, 11.96 min, and 70 MHz, respectively. Moreover, the kinetic aspects of the oxidation reaction of DBT in the UAOD process were investigated using a pseudo-first-order model. Furthermore, using the Arrhenius equation, an activation energy of 35.86 kJ mol⁻¹ was obtained. Additionally, thermodynamic analysis showed that the oxidation reaction of DBT was endothermic with a positive Gibbs free of energy, indicating the non-spontaneity of oxidation of DBT in the UAOD process. Moreover, the conversion rate of DBT has increased from 57% at 35 °C to 85% at 65 °C.

In this study, NiFe₂O₄–PEG, an effective nanocatalyst was synthesized via a hydrothermal method using different PEG concentrations and synthesis times.

Synthesis and characterization of AFe2O4 (A: Ni, Co, Mg)-silica nanocomposites and their application for the removal of dibenzothiophene (DBT) by an adsorption process: kinetics, isotherms and experimental design

The kinetics, equilibrium, and statistical aspects of the sulfur removal process from hydrocarbon fuels by AFe₂O₄–silica nanocomposites (A: Ni, Mg, and Co) have been investigated in the present study. Nanocomposites were prepared via the auto-combustion sol–gel method and then employed in the adsorptive desulfurization (ADS) process. Next, the prepared samples were characterized by different analytical methods including XRD, SEM, TEM, FT-IR, TGA, and BET. The contributions of conventional parameters including adsorbent dosage and contact time were then studied by central composite design (CCD) under response surface methodology (RSM). Based on the statistical investigations, optimum conditions for ADS were an adsorbent dosage of 7.82 g per 50 ml of the model fuel and a contact time of 32 min. The adsorption amounts reached 38.6 mg g⁻¹ for DBT. The quadratic model was applied for the analysis of variance. Based on the experimental data, the pseudo-first-order (PFO) model could explain the adsorption kinetics of the compounds. Furthermore, the Langmuir isotherm demonstrated considerable agreement with the experimental equilibrium data. According to the results, the NiFe₂O₄–SiO₂ nanocomposite showed the best performance compared to other compounds. The sulfur removal efficiency increased from 63 to 94% upon increasing the NiFe₂O₄–SiO₂ dosage from 3 to 9 g per 50 ml of the model fuel.

Among the methods for adsorptive desulfurization (ADS) represents a promising alternative method of removing sulfur by adsorption.

A facile sol–gel method based on urea–SnCl2 deep eutectic solvents for the synthesis of SnO2/SiO2 with high oxidation desulfurization activity

The n%-SnO2/SiO2 (n = 2, 4, 6) supported catalyst was prepared by the sol–gel and calcination method. Compared with the traditional impregnation method, the catalyst prepared by sol–gel method has higher oxidative desulfurization activity.

Efficient and reusable ordered mesoporous WOx/SnO2 catalyst for oxidative desulfurization of dibenzothiophene

The oxidative desulfurization (ODS) of organic sulfur compounds over tungsten oxide supported on highly ordered mesoporous SnO₂ (WO_x/meso-SnO₂) was investigated. A series of WO_x/meso-SnO₂ with WO_x contents from 10 wt% to 30 wt%, were prepared by conventional wet impregnation. The physico-chemical properties of the WO_x/meso-SnO₂ catalysts were characterized by X-ray diffraction (XRD), N₂ adsorption–desorption isotherms, electron microscopy, Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, and the temperature-programmed reduction of hydrogen (H₂-TPR). The characterization results indicated that these catalysts possessed mesoporous structures with uniform pores, high specific surface areas, and well-dispersed polyoxotungstate species on the surface of meso-SnO₂ support. The ODS performances were evaluated in a biphasic system (model oil/acetonitrile, S_initial = 2000 ppm), using H₂O₂ as an oxidant, and acetonitrile as an extractant. Dibenzothiophene (DBT) in the model oil was removed completely within 60 min at 50 °C using 20 wt% WO_x/meso-SnO₂ catalyst. Additionally, the effect of reaction temperature, H₂O₂/DBT molar ratio, amount of catalyst and different sulfur-containing substrates on the catalytic performances were also investigated in detail. More importantly, the 20 wt% WO_x/meso-SnO₂ catalyst exhibited 100% surfur-removal efficiency without any regeneration process, even after six times recycling.

The highly ordered mesoporous WO_x/meso-SnO₂ showed excellent catalytic activity and reusability in removing dibenzothiophene (DBT).

A hierarchical ZSM-22/PHTS composite material and its hydro-isomerization performance in hydro-upgrading of gasoline

The ZSM-22/PHTS (ZP) composite material assembled from a ZSM-22 zeolite crystal displayed a mesoporous structure. The CoMo/ZPA120 catalyst presented a good balance between HDS activity (95.2%) and lower ΔRON (−1.1).