Preparation of HPW@UiO-66 catalyst with defects and its application in oxidative desulfurization
Introduction
The standards for the sulfur content of oil-derived fuels in various countries are becoming more and more stringent. Recently, the standard of sulfur content less than 10 µg/g has been suggested by United States Environmental Protection Agency [1], [2]. However, the oil-derived fuels still contain abundant sulfur compounds, including “highly reactive sulfur compounds”, such as hydrogen sulfide, mercaptans and thioethers, and “refractory sulfur compounds”, such as benzothiophene (BT), dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). Therefore, deep desulfurization is extremely important to produce oil-derived fuels with ultralow sulfur content [3], [4], [5]. Oxidative desulfurization (ODS) is an environmentally friendly desulfurization technology that can effectively convert refractory sulfur compounds into sulfoxides or sulfones under mild conditions and then remove these species by extraction or adsorption due to their strong polarity [6], [7]. Hence, ODS has usually been employed for the ultradeep desulfurization of oil-derived fuels [8], [9], [10], and an active catalyst has been usually used to accelerate ODS process.
Keggin-type phosphotungstic acid (H3PW12O40, HPW) is a kind of heteropoly acid catalyst with the advantages of a stable structure, a simple preparation method, minimal environmental impact and a high catalytic activity for the desulfurization of oil-derived fuels [11]. However, the small specific surface area and low recovery rate of HPW limit its application [12]. To solve this problem, researchers prepared the catalysts with various heteropoly acids loading on molecular sieves and metal organic framework (MOF) materials, which possessed a large surface area [13], [14].
MOFs are three-dimensional network structures composed of metal atoms and organic ligands. Due to their large specific surface area and adjustable performance, MOFs are widely used in chemical sensing, catalysis and adsorption [15], [16], [17]. It was found that by introducing defects into the MOF, the material had a larger specific surface area and a higher pore volume [18], [19]. Meanwhile, the crystallinity of the material was increased and the crystal morphology was adjusted [20], [21]. Further, the properties of the material were optimized, such as catalytic properties, adsorption properties and electron conductivity [22], [23], [24]. Currently, the most common method for synthesizing MOF with defects is to add a small amount of monocarboxylic acid during the synthesis. The monocarboxylic acid and the ligand compete for the coordination with metal atom, which will affect the equilibrium reaction of the formation of the MOF skeleton, slow down the crystallization rate and form MOF with defects. UiO-66 is a typical MOF material and is composed of Zr ions and terephthalic acid [25], [26], [27]. With the advantage of a large specific surface area, UiO-66 is helpful to employ when loading with various heteropolyacids. Additionally, defects also can be introduced into UiO-66 to optimize its catalytic properties.
In this work, to improve the dispersion of HPW, UiO-66 was utilized as a carrier. A series of catalysts including defected and defect-free HPW@UiO-66 catalysts were prepared by hydrothermal synthesis. The morphology, structure and properties of the catalysts were analyzed by FT-IR, ICP-OES, XRD, SEM, TG and BET. The ODS performance and the recovery of the catalysts were further investigated.
Section snippets
Materials
Benzothiophene (BT), dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) were obtained from McLean Technology Co., Ltd, Shanghai, China. Phosphotungstic acid (HPW), terephthalic acid, N,N-dimethylformamide (DMF), n-octane, acetonitrile, hydrochloric acid (HCl, 37 wt%), hydrogen peroxide (30 wt%), benzoic acid, methanol and anhydrous ethanol were provided by Kelon Chemical Reagent Company, Chengdu, China. Zirconium chloride (ZrCl4) was purchased from Aladdin Ltd., Shanghai, China.
Effect of HPW loading on the catalyst
To determine the effect of HPW, the structure and morphology of the catalysts were characterized by FT-IR, ICP-OES, XRD and SEM.
In Fig. 1, the peak in the range of 1500–1660 cm−1 belonged to CO in the carboxylate. The peak in the range of 1450–1500 cm−1 was ascribed to the aromatic CC of the organic linker. Meanwhile, the C-O peak in the range of 1250–1450 cm−1 corresponded to the C-OH group of the carboxylic acid in the molecule [28], [29], [30]. Evidently, all of the UiO-66-D and HPW@UiO-66-D
Effect of HPW loading on the removal of DBT
The oxidative desulfurization experiment was carried out under the same reaction conditions. The desulfurization efficiencies of HPW@UiO-66-D with different HPW loadings are shown in Fig. 9. The order of the ability of the catalysts to remove DBT was: 0.5-HPW@UiO-66-D > 1.0-HPW@UiO-66-D > 1.5-HPW@UiO-66-D > 2.0-HPW@UiO-66-D > UiO-66-D. The addition of HPW had a significant improvement in the desulfurization performance of the catalysts. As shown in Table 1, the actual HPW loading of
Conclusion
In summary, a series of HPW@UiO-66 catalysts with defects were successfully prepared by hydrothermal synthesis. From the analyses of the structure, morphology and properties of the catalysts, 0.5-HPW@UiO-66 with defects (0.5-HPW@UiO-66-D) presented the advantages of a regular morphology, good thermal stability, high dispersion of HPW, high specific surface area, and good recycling performance, which were beneficial for oxidative desulfurization to obtain ultraclean fuel. Under the optimal
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgement
This work was supported by the Applied Basic Research Programs of Sichuan Province’s Science and Technology Commission Foundation, China [grant numbers: 2016JY0176].
References (38)
- et al.
A discussion on China’s vehicle fuel policy: Based on the development route optimization of refining industry
Energy Policy
(2018) - et al.
Copper nanoparticles advance electron mobility of graphene-like boron nitride for enhanced aerobic oxidative desulfurization
Chem. Eng. J.
(2016) - et al.
Deep oxidative desulfurization of fuels by superbase-derived Lewis acidic ionic liquids
Chem. Eng. J.
(2017) - et al.
Synthesis of phosphotungstic acid-supported bimodal mesoporous silica-based catalyst for defluorination of aqueous perfluorooctanoic acid under vacuum UV irradiation
Chem. Eng. J.
(2018) - et al.
Support enhanced α-pinene isomerization over HPW/SBA-15
Appl. Catal. B: Environ.
(2017) - et al.
Template method for a hybrid catalyst material POM@MOF-199 anchored on MCM-41: Highly oxidative desulfurization of DBT under molecular oxygen
Fuel
(2016) - et al.
Conversion of levulinic acid into chemicals: Synthesis of biomass derived levulinate esters over Zr-containing MOFs
Chem. Eng. Sci.
(2015) - et al.
Highly efficient adsorption of benzothiophene from model fuel on a metal-organic framework modified with dodeca-tungstophosphoric acid
Chem. Eng. J.
(2019) - et al.
Ionic liquid entrapped UiO-66: Efficient adsorbent for Gd3+ capture from water
Chem. Eng. J.
(2019) - et al.
Adsorption behavior of metal–organic frameworks for methylene blue from aqueous solution
Microporous Mesoporous Mater.
(2014)
Nanosize Zr-metal organic framework (UiO-66) for hydrogen and carbon dioxide storage
Chem. Eng. J.
Defect creation in metal-organic frameworks for rapid and controllable decontamination of roxarsone from aqueous solution
J. Hazard. Mater.
Polyoxometalates confined in the mesoporous cages of metal-organic framework MIL-100(Fe): Efficient heterogeneous catalysts for esterification and acetalization reactions
Chem. Eng. J.
Phosphotungstic acid encapsulated in metal-organic framework UiO-66: An effective catalyst for the selective oxidation of cyclopentene to glutaraldehyde
Micropor. Mesopor. Mater.
A metal-organic framework for oxidative desulfurization: UIO-66(Zr) as a catalyst
Fuel
Co supported on N-doped carbon, derived from bimetallic azolate framework-6: A highly effective oxidative desulfurization catalyst
J. Mater. Chem. A
Oxidative Desulfurization of Hydrocarbon Fuels
Catal. Rev.
Synthesis of mesoporous WO 3 /TiO 2 catalyst and its excellent catalytic performance for the oxidation of dibenzothiophene
New J. Chem.
Combined Extraction–Oxidation System for Oxidative Desulfurization (ODS) of a Model Fuel
Energy Fuels
Cited by (71)
Three-layer coated composite materials PMoV<inf>2</inf>@UiO-66-X@mSiO<inf>2</inf>: Efficient oxidative desulfurization catalysts
2024, Journal of Industrial and Engineering ChemistryA deep-insight into the relation between structure of graphene oxide-based interfacial catalyst and fuel oil desulfurization performance in Pickering emulsion
2024, Separation and Purification TechnologyHierarchically porous amino-functionalized nanoMOF network anchored phosphomolybdic acid for oxidative desulfurization and shaping application
2024, Journal of Colloid and Interface Science