Extractive Desulfurization Research Articles

Uncovering structure-activity relationships in Brønsted acidic deep eutectic solvents for extractive and oxidative desulfurization

Modeling the structure-activity relationships (SARs) of deep eutectic solvents (DESs) is crucial for upgrading their catalytic performance in targeted reactions. Herein, a series of Brønsted acidic DESs are developed for the SARs research at molecular and atomic levels. Experimental and theoretical results suggest that the catalytic activity increases with the decreasing distances between O atom of active sites in DESs and S atom in sulfur compounds, and the R2 between EODS efficiency and the valid distances of O···S is above 0.9. Such geometric configuration can be optimized by altering the composition of DESs, which in turn substantially triggers the reaction acceleration between active intermediates and substrates. The resulting DES (TEAC/2BSA) achieved deep desulfurization for various sulfur compounds based on the optimal valid distances of O···S. This work contributes to a deep understanding of the reaction mechanism and enables the effective screening of task-specific DESs.

Metal-based Ionic Liquids and Solid-loaded Catalysts in Fuel Oil Desulfurization: A Review

Abstract: Metal-based ionic liquids (MILs) have the advantages of designability, efficiency, stability, and regenerative cycle and can efficiently convert thiophene and its derivatives, which are important for the production of "ultra-low sulfur" oils. This paper provides an overview of the research progress of MILs in the field of fuel desulfurization, focusing on the current status of MILs and solid-loaded MILs catalysts in extractive desulfurization, oxidative desulfurization, extraction-catalyzed oxidative desulfurization, and catalytic-adsorption desulfurization processes. For MILs, the anion and cation can be altered by design so as to impart specific functions. Loading is one of the effective ways to solidify MILs, and the combination of MILs with different carriers can not only reduce the usage while ensuring the catalytic activity but also improve the reusability of the catalyst. The combination of MILs with specially structured carriers also allows solution-free adsorption and removal of oxidation products. Compared with conventional MILs, polymetallic-based ionic liquids (PMILs) exhibit ultrahigh catalytic activity and are one of the most promising materials available, but are still in their infancy in the field of fuel catalysis, and researchers are needed to enrich the gap in this field. Finally, some problems faced by various types of MILs are pointed out in order to design new functional MILs catalysts with better properties in the future and promote the further development of MILs in the field of fuel catalysis.

Computational Advances in Ionic-Liquid-Mediated Extractive Desulfurization of Fuel: A Minireview

Computational Advances in Ionic-Liquid-Mediated Extractive Desulfurization of Fuel: A Minireview

Evaluation of two imidazolium dicyanamide ionic solvents for extractive desulfurization of model fuels

Evaluation of two imidazolium dicyanamide ionic solvents for extractive desulfurization of model fuels

The role of microwave radiation in extractive desulfurization of real diesel fuel for green environment: an experimental and computational investigation

The process of removing sulfur compounds and aromatic compounds to produce clean fuel is an important and effective contribution to the processes of mitigating and adapting to climate change. In contrast, it is necessary to find an innovative way to remove sulfur and carcinogenic aromatic compounds because clean, low-sulfur diesel is commonly used in all countries of the world at the present time. Therefore, in this work, we have studied the effect of the microwave radiation power and the irradiation time with the use of more than one type of organic solvent; methanol, acetonitrile and ethyl acetoacetate; as an extractant and solvent to feed ratio impact on the removal of sulfur and aromatic compounds of a real diesel fuel feed which has 450 ppm sulfur content and 16 wt% aromatic Content. The results showed that the best solvent used during this work was ethyl acetoacetate. According to the results, high sulfur removal (≈ 92%) was accomplished with microwave-assisted extractive desulfurization technique under the following ideal conditions: the irradiation time is 7 min, the solvent feed ratio is 3:1 and the microwave intensity is 180 W. To reveal the mechanism of microwave-assisted extractive desulfurization via different organic solvents, a theoretical study including structural examination and interaction energy analysis on the interaction between dibenzothiophene (DBT) or dimethyl dibenzothiophene (DMDBT) and the different organic solvents was also conducted.

Prediction of Nernst coefficient of S-containing compounds between fuel and ionic liquid phases in the extractive desulfurization using linear and supported vector machine (SVM) methods: QSPR-based machine learning

BackgroundThe presence of sulfur-containing compounds (SCCs) in the refinery streams has significant economic and environmental implications. Great attention has been focused on finding the proper green solvents like ionic liquids (ILs11Ionic liquids) with efficient extraction performance as a matter of concern of environmental issues. MethodsThe research aimed to develop a predictive model using QSPR to forecast the partition coefficient of dibenzothiophene by ILs from n-dodecane. Utilizing a dataset of 54 ILs and their partition coefficients for DBT, the study employed two methods to optimize ILs structures and compared linear (GA-MLR) and non-linear (LS-SVM) models, with non-linear models showing higher accuracy. After initial modeling and assessing the primary dataset of 54 ILs, yielding an R2 parameter of 0.39 for the test set, the dataset was divided into smaller clusters for further analysis. Three additional clusters were investigated. The second cluster comprised 14 ILs with identical cations and varying anions, modeled with two descriptors. The third cluster, consisting of 21 ILs with imidazolium cations and diverse anions, was modeled with three descriptors. Lastly, the fourth cluster, comprising 26 ILs with different cations but the same anion, was also modeled with three descriptors. Significant findingsThe MLR model yielded R2 values of 0.98, 0.85, and 0.93 for the test sets of the second, third, and fourth clusters respectively. Effective descriptors, including cation polarizability and alkyl branch length, were examined for their impact on partition coefficient and desulfurization efficiency. This research aids in enhancing EDS processes with ILs, advancing more efficient desulfurization technologies.

Carboxylic acid-based deep eutectic solvent for efficient desulfurization: Experimental and computational thermodynamics

The improvement of fuel quality requires the reduction of sulfur content. The main challenge of catalytic cracking diesel extraction desulfurization is to find low-price and good-performance extractants. Based on experimental research, this work further explores the separation mechanism of DES for thiophene (TP) and benzothiophene (BTP). First, the COSMOS-RS model was used to predict the separation performance of 10 HBAs and 10 HBDs for TP and BTP. The results showed that the low-cost carboxylic acid based DES had excellent separation performance. Secondly, the effect of experimental conditions on the separation performance of three carboxylic acid based DESs was investigated. When the molar ratio of DES to TP and BTP was 3:1, after three stage extraction, the extraction rates of TP and BTP by TEAC: PrA(1:3) were 98.06 % and 98.53 %, respectively. Finally, the structure–activity relationship was studied by using quantum chemistry and molecular dynamics simulation. It was found that EvdW plays a dominant role in the desulfurization process and does not include H-bond interactions. TEA+ was distributed parallel to the aromatic ring and has a CH···π interaction with thiophene. TP and BTP were distributed in the voids of DES and do not affect the regeneration performance of DES.

Study on extraction desulfurization of road-paving asphalt by deep eutectic solvents

During the hot mixing process of road-paving asphalt, odorous substances are released, primarily consisting of sulfur-containing compounds that are regarded as atmospheric pollutants, negatively impacting both human quality of life and the eco-environment. In the paper, a kind of simulated asphalt solution was designed with two sulfur-containing compounds, dibenzothiophene (DBT) and benzothiophene (BT), as well as n-eicosane dissolved in cyclohexane. DBT and BT were extracted with deep eutectic solvent (DES) of tetrabutylammonium bromide and polyethylene glycol (TBAB/PEG). The effects of different molecular weight of PEG as donor on desulfurization efficiency were investigated. The effects of DES donor/receptor ratio, extraction temperature and time, solvent oil ratio, mixing speed, recycling performance of DES on desulfurization efficiency were also studied and optimized. The results indicated that the maximum desulfurization efficiency of BT reached 89.40 % at room temperature with a ratio of agent to oil of 2:1, reaction time of 30 min, and mixing speed of 600 rpm. Similarly, the desulfurization efficiency of DBT achieved 95.54 % when the ratio of agent to oil was 3.5:1, with reaction time of 30 min and mixing speed of 600 rpm. After being recycled eight times, the extraction efficiencies of DBT and BT remained at 85.3 % and 65.2 %, respectively. Under optimized conditions, the extraction efficiency of petroleum asphalt exceeded 23 %. Fourier Transform Infrared (FTIR) analysis indicated that the sulfur-containing compounds found in the saturates and aromatics of road-paving asphalt were extracted by DESs, which are generally more volatile than those found in asphaltenes during hot-mixing. Additionally, minimal changes were observed in the structural composition of the four fractions of desulfurized asphalt.

Imminent prognosis for piperazinium-based ionic liquids applications for coal desulfurization

Sulfur is one of the most important quality parameters for coal rank and utility in power generation. Combustion of coal having high sulfur content leads to SOx emissions which have detrimental impacts on the environment and human health. For sulfur remediation, N-methyl piperazinium-based room temperature ionic liquids (RTILs) were synthesized with two acidic anions precursors’ dimethyl sulfate and Perchloric acid. These novel RTILs were characterized using standardized analytical techniques of FTIR, 1H NMR, 13C NMR, HPLC, and TGA/DSC. Thermal stability of dimethyl piperazinium methyl sulfate [DMPI+][MeSO4−] and methyl piperazinium perchlorate [MPI+][ClO4−] was 284 °C and 256 °C. The proximate and ultimate analysis of coal samples collected from block II of the Thar coal field shows high moisture content (29–47 %) and gross calorific value between 5006–6660 Btu/lb suggesting it is Lignite-B type fuel. Total sulfur content in coal samples was 1–4.1 % reflecting variable degree of sulfurization. Coal cleansing through oxidative extractive desulfurization theme using nifty combinations of these acidic RTILs was verified by HPLC, FTIR, CHNS Elemental Analyzer, and X-ray Florescence (XRF) techniques. Sulfur leaching from the coal matrix was higher for methyl piperazinium perchlorate and an 85 % decrease in the sulfur part of coal along with increased heat content through this study suggests cleaner and sustainable use of coal.

SBA-15 Type Mesoporous Silica Modified with Vanadium as a Catalyst for Oxidative and Extractive Oxidative Desulfurization Processes.

One of the current challenges is the reduction of sulfur emitted into the atmosphere, usually in the form of sulfur oxides generated by fossil fuel combustion. To achieve this goal, the sulfur content should be reduced in fuel. In this context, vanadium-containing materials based on SBA-15 mesoporous silica supports and two different sources of vanadium were prepared, characterized, and applied as catalysts for oxidative desulfurization (CODS) and extractive oxidative desulfurization processes (ECODSs). The novelty of this work was the comparative study of vanadium-containing materials in two desulfurization systems. The properties of the catalysts, the concentration and state of vanadium species, and their role in the catalytic process were examined by low-temperature nitrogen physisorption, XRD, UV-Vis, XPS, and chemisorption of pyridine combined with FTIR spectroscopy. The catalytic performance of the material prepared using ammonium metavanadate was superior to that of the catalyst obtained using vanadium(IV) oxide sulfate, which was explained by a higher concentration of vanadium species on the surface of the support and their lower oxidation state in the former. Both types of catalysts showed high activity and stability in the ECODS process.

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.

Ionic Porous Aromatic Frameworks Embedding Polyoxometalates for Heterogeneous Catalysis.

Porous aromatic frameworks (PAFs) are highly promising functional porous solids known for their feasible amenability and extraordinary stability. When the framework was modified by ionic functional groups, these ionic PAFs (iPAFs) exhibited charged channels for adsorption, separation, and catalysis. However, the surface areas of ionic porous frameworks are usually lower than that of neutral frameworks, and their synthesis is limited by specific strategies and complex modification processes. To address these challenges, an intuitive route to construct ionic porous framework with high specific surface area was proposed. Herein, a multivariate ionic porous aromatic framework (MTV-iPAFs, named PAF-270) was synthesized using readily available building units with ionic functional groups through a multivariable synthesis strategy. PAF-270 exhibited hierarchical structure with the highest specific surface area among reported imidazolium-functionalized PAFs. Utilizing its physical and chemical properties, the availability for polyoxometalate loading and heterogeneous catalysis of PAF-270 were explored. PAF-270 exhibited a high adsorption capacity up to 50 % for both H3O40PW12 (HPW) and (NH4)5H6PV8Mo4O40 (V8). HPW@PAF-270 and V8@PAF-270 exhibited excellent catalytic abilities for oleic acid esterification and extractive oxidative desulfurization, respectively. Due to the stability of PAFs, these materials also showed remarkable resistance to temperature and pH changes. Overall, these results underscore the potential application of MTV-iPAFs as versatile functional porous materials.

Confining peroxophosphomolybdate within size-matched Zr-MOFs for extractive oxidative desulfurization

Deep desulphurization of diesel is essential because the sulfides from fuel combustion can cause acid rain, respiratory diseases and corrosion of industrial equipment. Peroxophosphomolybdate (BTA)3{PO4[MoO(O2)2]4}·3H2O, marked as PMo4, was confined in size-matched Zr-MOFs (UiO-66 and UiO-67) to prepared composites for extractive oxidative desulfurization. The composites underwent comprehensive characterization, including ICP-MS, FT-IR, XRD, SEM, XPS, TG and N2 adsorption–desorption analysis. Desulfurization test was conducted with PMo4 as homogeneous catalyst, and the reaction conditions were optimized. Then, the catalytic activity of the prepared composites was compared, and the result showed that the catalyst PMo4@UiO-67 can remove 94.1 % of the sulfides in the diesel within 100 min. After 15 consecutive tests, the total removal rate of sulfides still reached 88.5 %, thanks to the narrow window of carrier UiO-67 limited the leaching of the active component PMo4.

Oxidative and Extractive Desulfurization of Fuel Oils Catalyzed by N-Carboxymethyl Pyridinium Acetate and N-Carboxyethyl Pyridinium Acetate Acidic Ionic Liquids: Experimental and Computational DFT Study

Oxidative and Extractive Desulfurization of Fuel Oils Catalyzed by <i>N</i>-Carboxymethyl Pyridinium Acetate and <i>N</i>-Carboxyethyl Pyridinium Acetate Acidic Ionic Liquids: Experimental and Computational DFT Study

Coupled one-pot oxidative extractive desulfurization of a model fuel catalyzed by nanostructured-ZIF-67/Biomass-derived activated carbon composite

The simultaneous oxidation and extraction of refractory sulfur compounds, such as DBT, has emerged as one of the most efficient complementary procedures for the HDS process in achieving ultradeep desulfurization of fuels. In this paper, a bio-based activated carbon (AC) obtained from the waste of date palm bark has been utilized as an abundant, green, and low-cost support for synthesizing a stable metal-organic framework, zeolitic imidazolate framework-67 (ZIF-67), on its structure to reach a novel nanocomposite catalyst (AC/ZIF-67) for the removal of DBT from a model fuel through the extractive oxidative desulfurization method. The accuracy of the AC/ZIF-67 catalyst formation was comprehensively characterized using XRD, FTIR, FESEM, BET, and TGA analytical techniques. Subsequently, the newly synthesized nanocomposite catalyst was employed efficiently for removing DBT from a toluene solution, acting as a model fuel. The impact of various operating variables, i.e. catalyst dosage, the temperature of reaction, oxidant-to-sulfur (O/S) molar ratio, contact time, initial concentration of DBT, and volume of extraction solvent on the removal efficiency has been thoroughly investigated. The results revealed that employing only 25 mg of the AC/ZIF-67 catalyst could achieve a remarkably high efficiency of around 98 % after one hour oxidation of a 25 ppm DBT solution in the presence of TBHP, followed by extraction using acetonitrile. This was achieved while maintaining a constant temperature of 60 °C and an O/S ratio of 20. The obtained results confirm the potential application of ACs for supporting MOF catalysts in various catalytic processes such as desulfurization.

Preparation of the MoO3- Fe3O4 nanocomposites for deep oxidative desulfurization of model fuel: Optimization and experimental design

In the present study, the catalytic activity of the MoO3-Fe3O4 of molybdenum oxides prepared by the impregnation method was investigated in the extractive oxidative desulfurization (EODS) process. Structural characterization of the nanocomposite catalysts was studied by XRD, N2 adsorption–desorption isotherm, FT-IR, and VSM analyses. The EODS technology was applied to remove sulfur from a model fuel (dibenzothiophene in n-octane, DBT) using H2O2 as the oxidant, acetonitrile as the extracting solvent, and MoO3-Fe3O4 as the catalysts. Among the catalysts with various loadings of MoO3 on Fe3O4 nanoparticles (3, 6, 9, 12, and 15 wt%), the catalyst with 9 wt% MoO3 demonstrated the highest performance. Subsequently, the optimal design of the experiments using response surface methodology (RSM) based on Box-Behnken design (BBD) was applied to study the effects of the independent parameters such as O/S molar ratio, reaction temperature, and catalyst dosage on sulfur removal efficiency. Optimization studies were performed, and maximum sulfur removal efficiency of 98 % was achieved under the optimal conditions of 58 °C, O/S molar ratio: 5.9, and 0.116 g of 9 wt% MoO3-Fe3O4 as catalysts. The activity of the catalyst remained unchanged after six times recycling in the EODS process. Additionally, a catalytic reaction mechanism was proposed.

Design of dual-functional protic porous ionic liquids for boosting selective extractive desulfurization

Porous ionic liquids have demonstrated excellent performance in the field of separation, attributed to their high specific surface area and efficient mass transfer. Herein, task-specific protic porous ionic liquids (PPILs) were prepared by employing a novel one-step coupling neutralization reaction strategy for extractive desulfurization. The single-extraction efficiency of PPILs reached 75.0% for dibenzothiophene. Moreover, adding aromatic hydrocarbon interferents resulted in a slight decrease in the extraction efficiency of PPILs (from 45.2% to 37.3%, 37.9%, and 33.5%), indicating the excellent extraction selectivity of PPILs. The experimental measurements and density functional theory calculations reveal that the surface channels of porous structures can selectively capture dibenzothiophene by the stronger electrophilicity (Eint(HS surface channel/DBT) = −39.8 kcal mol−1), and the multiple extraction sites of ion pairs can effectively enrich and transport dibenzothiophene from the oil phase into PPILs through π···π, C–H···π and hydrogen bonds interactions. Furthermore, this straightforward synthetic strategy can be employed in preparing porous liquids, offering new possibilities for synthesizing PPILs with tailored functionalities.

Oil extraction desulfurization based on ionic liquid: Back-extractant screening, experiment and process simulation

A comprehensive back-extractant screening method was first developed for regenerating ionic liquids (ILs) after oil extraction desulfurization (EDS). Statistical analysis was performed using the Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) with the Entropy Weighting Method (EWM) on screening indices obtained based on the COnductor-like Screening MOdel for Realistic Solvents (COSMO-RS) and the Quantitative Structure Activity Relationship (QSAR) models. CCl4 was selected as the optimal back-extractant among 196 candidates for regenerating the IL, 1-butyl-3-methylpyridinium dicyanamide ([BMPy][DCA]), targeting the simultaneous removal of thiophene (TS), benzothiophene (BT), dibenzothiophene (DBT), and 4,6-dimethyldibenzothiophene (4,6-DMDBT). The experimentally measured hexary liquid–liquid equilibrium (LLE) confirmed the satisfactory selectivities and distribution coefficients of CCl4. Based on the NRTL parameters correlated from the LLE data, a complete EDS process including IL-extraction and IL-regeneration was established and evaluated economically based on the total annual cost (TAC). The results demonstrated that this process significantly decreased the sulfur content from 500 ppm to less than 10 ppm. The study results verified the feasibility and effectiveness of the proposed method and showed the excellent industrial performance of the selected IL and back-extractant.

Tailoring Type III Porous Ionic Liquids for Enhanced Liquid-Liquid Two-Phase Catalysis.

Porous Ionic Liquids (PILs) have gained attention but facing challenges in catalysis, especially in liquid-liquid two-phase reactions due to limited catalytic sites and hydrophilicity control. This work engineered a Type III PILs (PILS-M) using zeolitic imidazolate framework-8 (ZIF-8) confined phosphomolybdic acid (HPMo) as the microporous framework and N-butyl pyridine bis(trifluoromethane sulfonyl) imide ionic liquid ([Bpy][NTf2]) as the solvent. The PILS-M not only combines the advantages of traditional ionic liquids and microporous frameworks, including excellent extraction, high dispersion of catalytically active species, remarkable stability, etc., but also can make the inner surface of ZIF-8 turned to be hydrophilic that favors the contact between aqueous hydrogen peroxide oxidant and catalytically active sites for the promotion of catalytic performance in reactive extractive desulfurization (REDS) processes of fuel oils. This study demonstrates Type III PILs' potential as catalysts for sustainable chemical processes, offering insights into versatile PILs applications in diverse fields.

Extractive desulfurization of crude petroleum oil and liquid fuels using trihexyl tetradecyl phosphonium bis(2-ethylhexyl) phosphate ionic liquid

Abstract Increasing environmental concerns have led to the development of alternative methods for the desulfurization of petroleum crude oil and liquid fuels. Phosphonium-based ionic liquids (PILs) have recently demonstrated promising potential for effective extractive desulfurization (EDS). The present study focuses on the synthesis and application of trihexyl tetradecyl phosphonium bis(2-ethylhexyl) phosphate [THTDP][D2EHP] for EDS of synthetic model fuels and real crude oils. The molecular confirmation and thermal stability of [THTDP][D2EHP] were investigated using FTIR and TGA analyses. In addition, the conductivity, solubility, and viscosity of the synthesized ionic liquid (IL) were analyzed. The impact of reaction time, temperature, and sulfur compounds, such as thiophene, benzothiophene, and dibenzothiophene (DBT), on the desulfurization efficiency from synthetic fuels was also investigated. The results indicated up to 63 and 57 % sulfur removal from DBT-based model fuels and Iranian crude oil, respectively. The optimum extraction conditions were found as 1:1 IL/fuel mass ratio, 35 °C, and 30 min. The findings of this study provide valuable insights into the synthesis and utilization of PILs as promising solvents for extractive desulfurization of crude oil and liquid fuels.