Brønsted–Lewis Acidic Ionic Liquids and Application in Oxidative Desulfurization of Diesel Fuel

Abstract

Study on alternative methods to hydrodesulfurization is always an interesting area, because of the ineffectiveness for hydrodesulfurization to remove some cyclic sulfur compounds (S-compounds) and the high cost from harsh operation conditions and expensive catalyst, among which oxidative desulfurization (ODS) using ionic liquids (ILs) as solvent is intensively studied recently. Here, we synthesize a series of Brønsted–Lewis acidic ILs of N-methylpyrrolidonium zinc chloride ([Hnmp]­Cl x /(ZnCl2) y , x:y from 2:1 to 1:2) and investigate the ODS of both model diesel fuel composed of n-octane and dibenzothiophene and real FCC feedstock where such ILs are used as extractant and catalyst and 30 wt % H2O2 is used as oxidant, involving the factors such as IL composition (or x:y), temperature, dose of oxidant (or molar ratio of O/S), dose of IL (or mass ratio of IL/oil), recycling of IL and multistage desulfurization. IL composition has an important effect on sulfur removal (S-removal) efficiency, and [Hnmp]­Cl/ZnCl2 (x:y = 1, the structure nature was characterized with ESI-MS and FT-IR) shows the highest desulfurization capability with good recyclability. With [Hnmp]­Cl/ZnCl2, the S-content in model diesel fuel can be reduced to <1 ppm from 500 ppm with 99.9% S-removal at 75 °C, IL/oil = 1/3 and O/S = 8 after only one stage, while the sulfur removal for real FCC diesel fuel is less than 38% in one stage and can reach 83% after five stages, which might be ascribed to more-complex S-species in real fluidized catalytic cracking (FCC) diesel fuel as indicated by gas chromatography–sulfur chemiluminescence detection (GC-SCD) chromatogram analyses. The sulfur content (S-content) in FCC diesel fuel, however, can be reduced to 5.3 ppm with a total S-removal of 97.6% after five-stage ODS with one more extractive desulfurization with furfural as the extractant. This work shows that such Brønsted–Lewis acidic ILs are potential solvents used in ODS to produce clean fuel oils.

Oxidative Desulfurization of Gasoline by Ionic Liquids Coupled with Extraction by Organic Solvents

“…In addition, higher temperature may decrease the viscosity of ILs, enhance effective mixing and inter-phase mass transfer, and H 2 O 2 may be used effectively after decomposition. [50][51][52] On the other hand, too high temperatures are not good choice and might lead to auxiliary risk of explosion in the process, although high temperature enhances H 2 O 2 decomposition. Therefore, reaction at higher temperature should be carefully avoided.…”

Propionic acid-based deep eutectic solvents: synthesis and ultra-deep oxidative desulfurization activity

“…The trend is consistent with a previous study. 33 However, the reaction temperature of 30 C was considered as the optimal reaction temperature since low temperature ensures safety and low cost.…”

[HDMF]Cl-based DES as highly efficient extractants and catalysts for oxidative desulfurization of model oil

“…[25][26][27][28] For instance, Li et al 29 synthesized 1.6Et 3 NHCl$FeCl 3 extract, which facilitated the desulfurization rate up to 87%. Chen et al 30 reported that [Hnmp]Cl/ZnCl 2 was applied in oxidative desulfurization and its desulfurization rate reached up to 99.9% for the model diesel oil. Li et al 31 reported that C 5 H 9 NO$0.3FeCl 3 was used as an extractant as well as a catalyst in ODS and the removal rate of DBT was 97% in 3 h. Chen et al 32 synthesized [C 4 mim]Cl/3ZnCl 2 and 99.9% sulphur-removal rate could be obtained.…”