As the world’s largest oil producer, Saudi Arabia is keenly interested in
desulfurization techniques. Here is an article from King
Saud University that landed in my inbox, thanks to a Google® Scholar
alert.
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Research Article | Open Access
Volume 2020 |Article ID 3894804 | 11 pages |
https://doi.org/10.1155/2020/3894804
Ionothermal
Synthesis of Metal Oxide-Based Nanocatalysts and Their Application towards the
Oxidative Desulfurization of Dibenzothiophene
Bader Alenazi, Ali Alsalme , Saad G. Alshammari, Rais Khan , and
Mohammed Rafiq H. Siddiqui
Department of Chemistry, College of Science, King Saud University, Saudi Arabia
Abstract
Herein, different types of metal-containing ionic liquid (IL) complexes and
various metal oxide-based nanocatalysts have been successfully prepared (from
ionic liquids) and applied for the oxidative desulfurization (ODS) of dibenzothiophene
(DBT). The ILs complexes are comprised of N,N′-dialkylimidazolium salts of the
type [RMIM-Cl]2[MCln], where [RMIM+] = 1 alkyl-3-methylimidazolium and
M = Mn(II)/Fe(II)/Ni(II)/Co(II). These complexes were prepared using an easy
synthetic route by refluxing the methanolic solutions of imidazolium chloride
and metal chlorides under facile conditions. The as-prepared complexes were
further used as precursors during the ionothermal and chemical synthesis of
various metal oxide-based nanocatalysts. The resulting ILs salts and metal
oxides NPs have been characterized by FT-IR, TGA, XRD, SEM, and TEM analysis.
The results indicate that thermal and chemical treatment of ILs based precursor
has produced different phases of metal oxide NPs. The calcination produced
α-Fe2O3, Mn3O4, and Co3O4, NPs, whereas the chemical treatment of the ILs salts
have led to the production of Fe3O4, Mn2O3, and α-Co(OH)2. All the as-prepared
salts and metal oxide-based nanocatalysts were used as catalysts towards ODS of
dibenzothiophene. The oxidation of dibenzothiophene was performed at
atmospheric conditions using hydrogen peroxide as the oxygen donor. Among
various catalysts, the thermally obtained metal oxide NPs such as α-Fe2O3,
Mn3O4, and Co3O4, have demonstrated relatively superior catalytic activities
compared to the other materials. For example, among these nanocatalysts,
α-Fe2O3 has exhibited a maximum conversion (∼99%) of dibenzothiophene (DBT) to
dibenzothiophene sulfone (DBTO2).
1. Introduction
The increasing demand for petroleum products has led to a significant
enhancement in the environmental pollution, due to the emission of poisonous
gases during combustion [1]. This has led to the formulations of stringent
regulations for fuel specifications, which has tremendously increased the
demand of deep desulfurization of transportation fuels. Particularly, the
presence of sulfur-containing compounds, such as sulfides, disulfides, and
thiophenes in transportation fuels, which typically produce SOx, is a major
cause of air contamination [2]. To limit the emission of hazardous sulfur
compounds, several countries have legislated stringent environmental
regulations and strongly promoted the desulfurization of fuels (“S-free” fuels
(S content <10 4="" 6="" 8="" active="" activity="" also="" and="" are="" aromatic="" automobiles="" benzothiophene="" besides="" br="" by="" catalysts="" catalytic="" causes="" compounds="" conditions="" contents="" conventional="" converters.="" cost="" damage="" deep="" demand="" desulfurization="" dibenzothiophene="" diesel="" difficult="" dimethyl="" disulfides="" due="" efficiently="" excessive="" fuel="" hds="" high="" highly="" hindrance="" however="" hydrodesulfurization="" in="" including="" increase="" irreversible="" is="" large="" leading="" lifetime="" like="" metal="" of="" performed="" ppm="" presence="" present="" pressure="" process="" proportion="" reduction="" remove="" removed="" removes="" require="" several="" significant="" steric="" sulfides="" sulfur="" technique="" temperature="" the="" their="" these="" thiols="" to="" typically="" under="" used="" using="" usually="" various="" which="">
To overcome this, several deep desulfurization techniques have been developed,
including extraction, oxidation, photooxidation, bioprocess, adsorption, and
extraction by ionic liquids [10–12]. Among these techniques, oxidative
desulfurization (ODS) effectively removes the aromatic sulfur compounds from
fuels under mild condition and thus has gained significant prominence [13]. During
the ODS, sulfur compounds are converted into their corresponding sulfones which
are generally extracted using polar solvents. So far, several oxidants have
been used during this process, such as, hydrogen peroxide (H2O2), organic
peroxides, molecular oxygen, and ozone [12, 14]. Out of these oxidants, H2O2
has been found to be more effective and produces only water as a side product
[15]. The ODS can be performed by several methods which include solvent
extraction, photocatalytic oxidation, microwave catalytic oxidation, and so on
[16–18]. Apart from this, several other methods are being intensively studied
to improve the current HDS technology by developing more effective catalysts
and other materials used in this process [19].
In this regard, ionic liquid- (IL-) assisted ODS has also been used extensively
due to the high efficiency of IL in the removal of sulfur compounds [20]. So
far, ILs have demonstrated great potential in ODS due to their remarkable
properties such as, good thermal stability, extremely low volatility, enhanced
solubility, excellent ionic conductivity, and wide liquid temperature range
[21]. Moreover, they can be used effectively both as catalysts and extractants
(solvents) to replace volatile organic compounds which are flammable, hazardous,
and are threat to the environment [22, 23]. Currently, the process of catalytic
ODS, in which ILs are applied as both homogeneous and/or heterogeneous
catalysts have received greater attention when compared to the extraction of
sulfur compounds with ILs [24]. Particularly, the trend of applying supported
ILs as heterogeneous catalysts has become more popular, as being a solid
catalyst it can offer greater advantage. For instance, IL-based solid catalysts
demonstrate superior chemical properties such as, increased active sites and
enhanced dispersion, and they are also easy to separate from the reaction
mixture [25].
Recently, in several studies, metallic or metal oxide nanoparticles (NPs)
together with ILs have been applied either as support or active catalyst for
the catalytic conversion of sulfur compounds [26]. These IL-based nanocatalysts
exhibit both homogeneous and heterogeneous catalytic properties, which not only
facilitate rapid and selective chemical transformations but also offer enhanced
yield and easy separation and recovery of catalysts [27]. In several studies,
ILs have demonstrated excellent potential for the synthesis of various
inorganic metal and metal oxide NPs [28]. Particularly, the thermal synthesis
of nanomaterials using ILs (ionothermal synthesis) has received considerable
attention of researchers. However, the ionothermal synthesis of metallic or
metal oxide NPs has been rarely studied. In our previous study, we have
demonstrated the ionothermal synthesis of NiO NPs using N,N′-dialkylimidazolium
salts of the type [RMIM-Cl]2[MCln], where [RMIM+] = 1-alkyl-3-
methylimidazolium and M = Ni(II) ionic liquid [29]. The as-prepared IL was used
a precursor, which was calcined at 500°C for several hours to produce Ni NPs.
The study has revealed the significant effect of IL on the shape and morphology
of resultant NPs Scheme 1.
For further continuation of our previous work, in this study, we demonstrate
the preparation of transition metal-containing IL-based complexes. The
as-prepared complexes were used as precursors for the synthesis of different
metal oxide NPs including Manganese (Mn), Iron (Fe), Cobalt (Co), and Nickel
(Ni) NPs using thermal and chemical treatment methods. The IL-based precursors
are made up imidazolium and N,N′-dialkylimidazolium salts of the type
[RMIM-Cl]2[MCln], where [RMIM+] = 1-alkyl-3-methylimidazolium and M = Mn(II),
Fe(II), Ni(II), and Co(II). The resultant complexes and metal oxide NPs have
been characterized by powder X-ray diffraction, scanning electron microscopy
(SEM), and transmission electron microscopy (TEM). Both the IL-based precursors
and resultant NPs have been tested for their catalytic activity towards the
oxidative desulfurization of dibenzothiophene (DBT).
Free full text source: https://www.hindawi.com/journals/jchem/2020/3894804/
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According to Wikipedia, King Saud University (https://ksu.edu.sa/en/ ) is a public
university in Riyadh, Saudi Arabia, founded in 1957 by King Saud bin Abdulaziz
as Riyadh University, as the first university in the Kingdom of Saudi Arabia.
The university was created to meet the shortage of skilled workers in Saudi
Arabia. It was renamed King Saud University in 1982.
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University Bader Alenazi, one of the authors of the article
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Bader Alenazi
Ali Alsalme
King Saud University, Chemistry,
Post-Doc
Catalysts
Kingdom of Saudi Arabia
Papers
α-Pinene isomerisation over heteropoly acid catalysts in the gas-phase
Applied Catalysis A-general, 2010
Solid acid catalysts based on H 3PW 12O 40 heteropoly acid: Acid and catalytic
properties at a gas–solid interface
Journal of Catalysis, 2010
Solid acid catalysts prepared by supporting 15 wt%H3PW12O40 heteropoly acid
(HPA) on TiO2, ZrO2 a... more
Heteropoly acids as catalysts for liquid-phase esterification and
transesterification
Applied Catalysis A-general, 2008
Esterification of hexanoic acid and transesterification of ethyl propanoate and
ethyl hexanoate w... more
source: http://king-saud.academia.edu/AliAlsalme
Saad G. Alshammari
Saad G. Alshammari's research while affiliated with King Saud University and
other places
Publications (4)
Scheme 1: Schematic representation of the preparation of...
Ionothermal Synthesis of Metal Oxide-Based Nanocatalysts and Their Application
towards the Oxidative Desulfurization of Dibenzothiophene
Article
Mar 2020
Bader Alenazi
Ali Alsalme
Saad G. Alshammari[...]
M R H Siddiqui
Herein, different types of metal-containing ionic liquid (IL) complexes and
various metal oxide-based nanocatalysts have been successfully prepared (from
ionic liquids) and applied for the oxidative desulfurization (ODS) of
dibenzothiophene (DBT). The ILs complexes are comprised of
N,N′-dialkylimidazolium salts of the type [RMIM-Cl]2[MCln], where [...
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