Development of microwave induced hydrodesulfurization of petroleum streams: A review

Ionic Liquids as Green and Efficient Desulfurization Media Aiming at Clean Fuel

With increasingly stringent emission limits on sulfur and sulfur-containing substances, the reduction and removal of sulfur compounds from fuels has become an urgent task. Emissions of sulfur-containing compounds pose a significant threat to the environment and human health. Ionic liquids (ILs) have attracted much attention in recent years as green solvents and functional materials, and their unique properties make them useful alternatives to conventional desulfurization organic solvents. This paper reviews the advantages and disadvantages of traditional desulfurization technologies such as hydrodesulfurization, oxidative desulfurization, biological desulfurization, adsorptive desulfurization, extractive desulfurization, etc. It focuses on the synthesis of ionic liquids and their applications in oxidative desulfurization, extractive desulfurization, extractive oxidative desulfurization, and catalytic oxidative desulfurization, and it analyzes the problems of ionic liquids that need to be solved urgently in desulfurization, looking forward to the development of sulfuric compounds as a kind of new and emerging green solvent in the field of desulfurization.

Novel Gemini ionic liquid for oxidative desulfurization of gas oil

The N₁,N₁,N₃,N₃-tetramethyl -N₁,N₃-diphenylpropane-1,3-diaminium dichloride ionic liquid (ILc) is an environmentally friendly catalyst for oxidative-extractive desulfurization of gas oil (sulfur content = 2400 ppm) in the presence of H₂O₂ as an oxidizing agent. The precise structure of the prepared IL was confirmed using FT-IR spectroscopy, and¹H-NMR. The reaction temperature, IL ratios, H₂O₂ dosage, and reaction time were studied to assess their effects on the desulfurization efficiency. The thermodynamic parameters of the oxidation reaction were determined. A desulfurization efficiency of 84.7% was obtained after the extractive desulfurization process using acetonitrile as an organic solvent at a solvent to feed ratio of 1:1 (v/v). Furthermore, the prepared IL may be reused for at least six cycles without any significant change in its desulfurization performance or chemical structure, which confirms its high reusability.

Effects of microwave and plastic content on the sulfur migration during co-pyrolysis of biomass and plastic

In order to reduce the risks of sulfur-containing contaminants present in biofuels, the effects of microwave and content of hydrogen donor on the cracking of C-S bonds and the migration of sulfur were studied by co-pyrolysis of biomass and plastic. The synergistic mechanism of microwave and hydrogen donor was explored from the perspective of deducing the evolution of sulfur-containing compounds based on microwave thermogravimetric analysis. By combining temperature-weight curves, it was found that microwaves and hydrogen radicals promoted the cracking of sulfur-containing compounds and increased the mass loss of biomass during pyrolysis. The mixing ratio of hydrogen donor (plastic) was the key parameter resulting in the removal of sulfur from oil. By adjusting the mixing ratio, the yield of co-pyrolyzed oil was three times higher than that of cow dung pyrolysis alone and the relative removal rate of sulfur reached 73.67%. The relative content of sulfur in the oil was reduced by 73.77% due to the escape of sulfur-containing gases (H₂S, COS and C₂H₅SH) and the formation of sulfate crystals in the char. Microwave selectively heated sulfur-containing organics and hydrogen radicals stimulated the breaking of C-S bonds, which improved the cracking efficiency of the oil. This breaking will provide a theoretical and technological reference for the environmentally friendly treatment of biomass and biofuels.

Preparation of magnetic urchin-like NiCo2O4 powders by hydrothermal synthesis for catalytic oxidative desulfurization

The bundle-like NiCo2O4 powder was synthesized using hydrothermal synthesis and high-temperature calcination method and, as catalyst, NiCo2O4 powder was utilized to activate peroxymonosulfate for removing dibenzothiophene from fuel oil.

Catalytic activity of synthesized 2D MoS2/graphene nanohybrids for the hydrodesulfurization of SRLGO: experimental and DFT study

Hydrodesulfurization (HDS) of straight run light gas oil (SRLGO) using novel highly active two-dimensional (2D) MoS₂/graphene (G) nanohybrid catalysts is a precursor technology for the production of clean heavy fuel. The aim of this research is the synthesis of 2D MoS₂/G nanohybrid catalysts by use of exfoliation method from commercial bulky MoS₂ and graphite using hydrothermal ball milling system, which is a low-cost, high-yield, and scalable method. These nanohybrid catalysts were characterized by XRD, Raman spectroscopy, XPS, SEM, TEM, STEM, ICP, BET surface, TPR, and TPD techniques. Also, catalytic activities of 2D MoS₂/G nanohybrid catalysts were evaluated under different operating conditions such as temperature, pressure, LHSV, and H₂/Feed (SRLGO) ratio in the HDS reaction. The conversion of the HDS of SRLGO with 14000 ppm sulfur showed a considerably higher activity of 2D MoS₂/G nanohybrid catalyst (99.95% HDS efficiency) compared with the Co-Mo/γAl₂O₃ as a commercial catalyst (90% HDS efficiency) in the operation condition (340 °C, 40 bars, LHSV: 1 h^-1and H₂/oil: 600 NL L^-1) which is economically valuable. Using density functional theory calculations, the detailed mechanism of the HDS process over MoS₂/G catalyst was explored. It was found that sulfur coverage on the Mo edge of MoS₂ plays an important role in the hydrogenation of sulfur components.

Energy and Resource Utilization of Refining Industry Oil Sludge by Microwave Treatment

The oily sludge from crude oil contains hazardous BTEX (benzene, toluene, ethylbenzene, xylene) found in the bottom sediment of the crude oil tank in the petroleum refining plant. This study uses microwave treatment of the oily sludge to remove BTEX by utilizing the heat energy generated by the microwave. The results show that when the oily sludge sample was treated for 60 s under microwave power from 200 to 300 W, the electric field energy absorbed by the sample increased from 0.17 to 0.31 V/m and the temperature at the center of the sludge sample increased from 66.5 °C to 96.5 °C. In addition, when the oily sludge was treated for 900 s under microwave power 300 W, the removal rates were 98.5% for benzene, 62.8% for toluene, 51.6% for ethylbenzene, and 29.9% for xylene. Meanwhile, the highest recovery rates of light volatile hydrocarbons in sludge reached 71.9% for C3, 71.3% for C4, 71.0% for C5, and 78.2% for C6.

Experimental and theoretical study of microwave enhanced catalytic hydrodesulfurization of thiophene in a continuous-flow reactor

Hydrodesulfurization (HDS) of thiophene, as a gasoline model oil, over an industrial Ni-Mo/Al2O3 catalyst was investigated in a continuous system under microwave irradiation. The HDS efficiency was much higher (5%–14%) under microwave irradiation than conventional heating. It was proved that the reaction was enhanced by both microwave thermal and non-thermal effects. Microwave selective heating caused hot spots inside the catalyst, thus improved the reaction rate. From the analysis of the non-thermal effect, the molecular collisions were significantly increased under microwave irradiation. However, instead of being reduced, the apparent activation energy increased. This may be due to the microwave treatment hindering the adsorption though upright S-bind (η1) and enhancing the parallel adsorption (η5), both adsorptions were considered to favor to the direct desulfurization route and the hydrogenation route respectively. Therefore, the HDS process was considered to proceed along the hydrogenation route under microwave irradiation.

Microwave effects on NiMoS and CoMoS single-sheet catalysts

Single-sheet nanoclusters of MoS₂, NiMoS or CoMoS are widely used in hydrodesulfurization (HDS) catalysis in the petroleum industry. In HDS reactions under microwave irradiation, experiments indirectly pointed out that for pristine MoS₂ reaction rates are accelerated because hot spots are generated on the catalyst bed. In this work, we investigated NiMoS and CoMoS isolated single-sheet substituted catalysts before and after thiophene adsorption focusing on quantifying the effect of microwave irradiation. For that purpose, density functional theory (DFT) molecular charge densities of each system were decomposed according to the distributed multipole analysis (DMA) of Stone. Site dipole values of each system were directly associated with a larger or smaller interaction with the microwave field according to a proposed general approach. We showed that microwave enhancement of HDS reaction rates can occur more efficiently in the CoMoS and NiMoS promoted clusters compared to pristine MoS₂ in the following order: CoMoS > NiMoS > MoS₂. The atomic origin of the catalyst hot spots induced by microwaves was clearly established in the promoted clusters.

Co-promoted MoO3 nanoclusters for hydrodesulfurization

In this paper, we report the synthesis of ultrasmall Co-promoted MoO₃ nanoclusters (∼2 nm) supported over γ-Al₂O₃ possessing an increased number of Mo edge atoms, using colloidal synthesis for hydrodesulfurization reaction.

Preparation of rGO/ZrP as a new adsorbent in dibenzothiophene removal from n-decane with high capacities and good regenerability

In this work, reduced graphene oxide (rGO)/zirconium phosphate (ZrP) nanosheets were prepared by intercalation of graphene oxide (GO) between ZrP layers followed by its reduction to rGO.

DFT investigations of the adsorption and hydrodesulfurization mechanism of thiophene catalyzed by Pd(111) surface

The adsorption of thiophene on Pd(111) surface at hollow site through the ring plane is the most stable. The direct hydrodesulfurization has more than one possible product and is difficult to control. The indirect hydrodesulfurization was the best fit for the 1,2-cis-hydrogenation.