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Li, et al.

desulfurization owing to its three-dimensional aluminized MCM-41 and SBA-15 grafted with Ce ,
3+ 22
interconnected supercage structure (pore diameter Ni-Ce/alumina-silica (Al O -SiO ), Ce-Fe/activated
23
2
2
3
~1.3 nm) and exceptionally high specific surface area carbon (AC) composites. A few studies have also
24
(>700 m /g). Its framework is enriched with abundant reported on the use of ruthenium complexes for the
2
Brønsted and Lewis acid sites, facilitating acid-base extraction of dibenzothiophene (DBT) from petroleum
interactions with sulfur-containing molecules and feedstocks. For instance, the binuclear ruthenium
enabling efficient removal of bulky organosulfur complex, [CpRu(CO) (µ -η (S): η -DBT)RuCp*][PF ]
6
1
6 2
2
2
compounds such as thiophene, benzothiophene, and was used for desulfurization of DBT, in which one Ru
dibenzothiophene. Furthermore, Y-zeolite exhibits is η (S)-coordinated to DBT whereas the other Ru is
1
outstanding thermal stability and highly tunable η (S)-coordinated to the same DBT molecule. 25,26 As
6
structural properties, which can be optimized through ion noted, the strength of the direct S–M σ bond is mainly
exchange, steam treatment, and chemical modifications. dependent on the metal ion’s charge and ionic radius.
Nevertheless, pristine Y-zeolite suffers from inherent Specific metal ions with strong ionic polarities are able
limitations in practical applications. Its adsorption to enhance direct S–M interaction and further improve
primarily relies on physical interactions and weak acid- adsorption selectivity for sulfur compounds.
base affinities, which are inadequate for capturing low- Traditionally, the liquid phase ion-exchange method
polarity, refractory sulfur species. Moreover, competitive has been used to prepare the metal ion-modified
adsorption of non-sulfur aromatic hydrocarbons Y-zeolites, 14,15,27,28 while only a few studies have explored
in complex fuel matrices leads to poor selectivity, the solid state reaction method. 29,30 In this study, the
hindering the achievement of deep desulfurization at solid-state reaction method was used to develop high-
ultra-low sulfur levels (<10 ppm). In addition, repeated selectivity S–M interaction adsorbents. A series of metal
adsorption-regeneration cycles tend to degrade the ions with high charge number and lower ionic radius—
framework’s acidity and pore architecture, ultimately namely, ruthenium(III) (Ru ), bismuth(III) (Bi ),
3+
3+
compromising long-term operational stability. zirconium(IV) (Zr ), and antimony (III) (Sb )—were
4+
3+
Incorporating metal ions into adsorbents has been selected as active sites for the modification of Y-zeolite.
shown to enhance their performance, as the introduced The desulfurization performance of these MY-zeolite
metal species can act as active sites for the adsorption of adsorbents was evaluated using batch adsorption of
sulfur-containing compounds. Most studies have focused thiophene (TP) from a model gasoline containing 20
on reactive adsorption mechanisms, which can be ppmw sulfur. We investigated the effect of various
broadly categorized into two types: (i) π-complexation- parameters, such as the metal type, metal ion form,
based adsorbents, such as metal-ion-exchanged Y-type chemical state, and loading amount, on the TP removal
zeolites (denoted as MY-zeolites, where M represents efficiency.
metal ions including copper(I) (Cu⁺), silver(I) (Ag⁺),
nickel(II) (Ni²⁺), zinc(II) (Zn²⁺), and palladium(II) 2. Materials and methods
(Pd²⁺)); and (ii) adsorbents that rely on direct sulfur–metal
(S–M) interactions, where the Y-type zeolite is modified 2.1. Preparation of MY-zeolite (MY-1 and RuY-X
with high-charge metal ions such as cerium(IV) (Ce⁴⁺) series) adsorbents
and lanthanum(III) (La³⁺). 14,15 Compared to adsorbents Metal-ion-modified Y-type zeolite adsorbents were
based on π-complexation, those utilizing direct S–M prepared using the solid-state ion exchange method.
interactions generally demonstrate higher selectivity One gram of ammonium-exchanged Y-zeolite (NH₄Y-
for sulfur compounds, particularly in the presence zeolite) was thoroughly mixed and ground for 1 h with
of competing aromatic hydrocarbons. Recently, new a stoichiometric amount of ruthenium(III) chloride
zeolite nanofiber bundle catalysts developed by Tang hydrate (RuCl₃·xH₂O), antimony(III) chloride (SbCl₃),
et al. demonstrated sulfur reduction to below 10 ppmw zirconyl chloride octahydrate (ZrOCl₂·8H₂O), or
in diesel using the HDS process. This has underscored bismuth(III) nitrate pentahydrate (Bi(NO₃)₃·5H₂O),
16
the importance of adsorption selectivity over sulfur with an initial molar ratio of metal ion to ammonium ion
uptake in achieving the ultra-low sulfur fuel standard. (M/NH₄⁺) equal to 1. The mixtures were subsequently
A lot of high-selectivity sulfur adsorbents incorporating calcined in air at 500°C for 2 h. These resulting
Ce-modified microporous materials have been reported, adsorbents were denoted as MY-1 and RuY-X, where
such as CeY, 17,18 Ce-modified mesoporous structure M represents the metal ion (Ru³⁺, Sb³⁺, Zr⁴⁺, or Bi³⁺),
Y-zeolite, 19,20 Ce-doped MCM-41 frameworks, and X indicates the initial molar ratio of ruthenium(III)
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Volume 22 Issue 6 (2025) 90 doi: 10.36922/AJWEP025250204