Oxidative Desulfurization of Liquid Fuels Using Polyoxometalate-Based Catalysts: A Review

Abstract

Nowadays, desulfurization of liquid fuels is inevitable because of strict environmental and industrial regulations on liquid fuels specifications. Hydrodesulfurization (HDS) technology has been used widely to produce fuels with ultralow sulfur content (S ≤ 10 ppm). However, this method is not effective enough for removing refractory sulfur compounds (e.g., benzothiophene, dibenzothiophene, and their derivatives). Consequently, alternative or supplementary desulfurization methods have been rapidly developed in recent years. The oxidative desulfurization (ODS) process is a promising method with high selectivity, low cost, mild reaction conditions, and high efficiency. In the past few decades, the ODS process of fuels by polyoxometalates (POMs) as catalysts have attracted considerable attention, resulting in different works have been published due to their strong acidity, fast and reversible multielectron redox properties, tunable redox properties, as well as thermal, hydrolytic, and oxidative stability. In this review, the removal of S-compounds from fuel oils is investigated via the ODS process using homogeneous and heterogeneous polyoxometalate catalysts. Moreover, the advantages and problems of each system are discussed. Various techniques for reducing their noticeable drawbacks are also presented. Finally, the regeneration of POM catalysts, as an important step in industrial applications, is examined.

Advances in Oxidative Desulfurization of Fuel Oils over MOFs-Based Heterogeneous Catalysts

“…Polyoxometalates (POMs) have been widely studied as the active centers of ODS catalysts because their acidic and redox properties can be effectively designed and controlled through changing their compositions and structures at atomic or molecular scale [62,63]. However, it is well known that POMs are easily soluble in organic medium, which is not beneficial for the recycling and reuse of heterogeneous catalysts.…”

Facile Synthesis of a Novel Ni-WO3@g-C3N4 Nanocomposite for Efficient Oxidative Desulfurization of Both Model and Real Fuel

“…Based on experimental evidence, above 90% of thiophene, dibenzothiophene, and their derivatives can be easily oxidized under optimized conditions. 14 Moreover, ultradeep sulfur removal by ODS can now be carried out with H 2 O 2 (oxidant)-assisted inorganic–organic hybrid catalysts when compared with traditional desulfurization methods.…”

Thermal Structure Transformation of Methylammonium Vanadate and it's Application as a Negative Staining Reagent for Observing SARS‐CoV‐2

“…[1] Polyoxometalates form a wide variety of compositions and structures that produce different physical and chemical properties, such as negative charges, oxo‐enriched surfaces, acid‐base properties, and redox potential. [ 1 , 2 , 3 ] These properties have led to their wide use as the main compounds in catalysts,[ 4 , 5 ] electrocatalysts,[ 6 , 7 ] medicines, [8] sensors, [9] and staining reagents. [ 10 , 11 ] Normally, polyoxometalates are synthesized via the condensation of oxoanions (MoO 4 2− , WO 4 2− , or VO 4 3− ) using a self‐assembly process.…”