Three-Dimensional Graphene Oxide Covalently Functionalized with Dawson-Type Polyoxotungstates for Oxidative Desulfurization of Model Fuels

Abstract

Graphene oxide (GO) with three-dimensional network structure (3D GO) was used as a support, and the monovacant Dawson polyoxotungstate K10[α-P2W17O61]·20H2O (P2W17) modified with silane coupling agent was covalently immobilized on 3D GO to prepare a novel heterogeneous catalyst P2W17/3D GO. Characterizations of the supported catalyst by FT-IR, UV–vis, XPS, SEM, and TEM confirmed that P2W17 was immobilized on 3D GO successfully and well dispersed. The as-prepared catalyst P2W17/3D GO exhibited high catalytic performance in the oxidative desulfurization (ODS) system of model fuels containing dibenzothiophene (DBT) or tetrahydrothiophene (THT) using H2O2 as the oxidant. 3D GO exhibits a certain carrier effect due to its three-dimensional network structure, the strong adsorption of thiophene compounds through π–π and S−π interactions, and the acid–base interactions with 3D GO, which make the ODS performance of P2W17/3D GO much higher than that of P2W17/2D GO as well as the homogeneous catalyst EPO-P2W17. Various reaction conditions were investigated, and complete oxidative removal of DBT (500 ppm) and THT (5000 ppm) was achieved at 120 and 30 min under the optimum conditions, respectively. Kinetics studies were conducted to better understand the oxidation reactions, and the catalytic oxidation of DBT and THT can both be well described by the pseudo-first-order model. Moreover, the supported catalyst P2W17/3D GO showed excellent durability even after 5 times recycling due to covalent immobilization, which makes it a promising prospect for industrial application.

Defective silicotungstic acid-loaded magnetic floral N-doped carbon microspheres for ultra-fast oxidative desulfurization of high sulfur liquid fuels

“…According to Fig. 9, and in line with previous studies, 23,65,75 the desulfurization efficiencies of the catalysts fell in the following order: DBT > 4,6-DMDBT > BT. This is precisely because the electrophilic assault of reactive oxygen species on sulfur atoms, which is strongly related to the electron density of sulfur atoms in thiophenic compounds, essentially drives the oxidation of these thiophenic compounds.…”

“…4e), the binding energies of the W4f 7/2 and W4f 5/2 doublet states were observed at 35.6 eV and 37.7 eV, respectively, confirming that tungsten in the SiW 12 existed in a fully oxidized state. 65 Additionally, the loss feature of WO 3 in SiW 12 was found as a small peak at 41.2 eV. The peak associated with the Si–O–W bond in SiW 12 occurred at a binding energy of 102.1 eV according to the Si 2p high-resolution XPS spectra shown in Fig.…”

“…Additionally, by employing the W atom as the active site, the turnover frequency (TOF) of γ-Fe 2 O 3 @NC@SiW 12 -300 was determined to be 110.07 h −1 (see formula (3) of ESI†), which is higher compared to most earlier literature reports. 65,68,69 A good catalytic activity of γ-Fe 2 O 3 @NC@SiW 12 -300 in the presence of H 2 O 2 can thus easily be inferred from the comparatively high kinetic constant ( k = 0.235 min −1 ), low activation energy ( E a = 38.79 kJ mol −1 ), and high TOF (110.07 h −1 ).…”

“…Additionally, by employing the W atom as the active site, the turnover frequency (TOF) of γ-Fe 2 O 3 @NC@SiW 12 -300 was determined to be 110.07 h −1 (see formula (3) of ESI †), which is higher compared to most earlier literature reports. 65,68,69 A good catalytic activity of γ-Fe 2 O 3 @NC@SiW 12 -300 in the…”

Latest progress in covalently modified polyoxometalates-based molecular assemblies and advanced materials

“…Covalent immobilization increased the bonding strength between POMs and MNPs, especially during the separation and rinsing steps of material preparation. Jiao and co-workers covalently immobilized Dawson POMs on glycyl methacrylate (PGMA)/SiO2 and graphene oxide with three-dimensional network structure (3D GO) [109,110] . Under mild conditions, 100% desulfurization of tetrahydrothiophene (THT) was reached within 60 min with P2W17-PGMA/SiO2-NaHCO3 as catalyst, and only tetrahydrothiophene oxide (THTO) was generated in the whole oxidation process.…”