Thiophenic Compounds Research Articles

Carbon and sulfur isotopic composition of alkyl- and benzo-thiophenes provides insights into their origins and formation pathways

Thiophenic compounds can provide significant geochemical information and may be used as paleoenvironmental indicators as long as their biological origins and formation pathways are understood. To this end, we investigated the structures, distributions, δ13C and δ34S values, of specific thiophenic compounds extracted from immature sedimentary rocks from the Upper Cretaceous (Ghareb Formation, Shefela Basin, Israel).Isoprenoidal alkylthiophenes (ATs) showed a general trend of depletion in their 13C and 34S values relative to the normal (linear) ATs extracted from the studied samples. In addition, a consistent enrichment of up to 2‰ in 13C and 8‰ in 34S of methylated ATs (m/z = 111), relative to non-methylated ones (m/z = 97), was recorded. This suggests that AT precursors derived from different organisms and diagenetic pathways, which later affected their sulfurization mechanisms. The large variation, of ∼15‰, in the δ34S values of individual ATs, along with the general trend of 13C depletion with increasing Tmax, suggests that ATs formed by a set of diagenetic processes of mild thermochemical alteration. The δ13C values of benzothiophenes (BTs) were enriched in 13C relative to the rest of the organic sulfur compounds; by ∼3‰ on average. This in turn suggests that BTs were generated mainly by sulfurization and subsequent ring closure, or aromatization of 13C-enriched aromatic/alkyl cyclohexane compounds with unsaturation and/or functional groups in their alkyl chain. Such 13C-enriched precursors can be generated from carotenoids and terrestrial compounds (e.g., by lignin degradation). The large variation in δ34S values of individual BTs, of ∼15‰, suggests that the BTs in our samples were formed during diagenesis and did not experience advanced thermal alteration processes. Therefore, their occurrence in immature sedimentary rocks might be used as a proxy for early thermochemical alteration that cannot be detected using conventional geochemical indicators, such as Tmax.The combination of structural, 13C and 34S investigations of individual organic sulfur compounds enhanced an understanding of their sulfurization pathways and origins, which in turn may expand their utilization as paleoenvironmental indicators.

The Dielectric Properties of Thiophene Model Compounds: Insights for Microwave Desulfurization of Coking Coal

Microwave desulfurization capitalizes on the different dielectric properties of sulfur-containing and sulfur-free components in coal. However, the dielectric properties of thiophene compounds, the ...

Antiradical Properties of trans-2-(4-substituted-styryl)-thiophene.

2-substituted thiophene compounds with electron donating and electron withdrawing p-phenyl substitution were synthesized and studied their radical scavenging properties using DPPH assay and DFT method. It is shown that p-hydroxy and p-amino phenyl substituted compound exhibit radical scavenging activity. From DFT and radical scavenging studies, a correlation between IC50 with the bond dissociation enthalpy, proton affinity, ground state dipole moment and optical band gap of compound is found. Compounds 1-3 with electron withdrawing substituent (NO2, CN, Cl) do not show any radical scavenging properties, whereas compounds 6-7 with electron donating substituent (OH, NH2) show antiradical properties. Further, the antiradical activity is reduced drastically by replacing the -OH and -NH2 with methoxy and -N-alkylating group respectively in 6 and 7. The compound with p-hydroxy phenyl substitution, exhibits stronger antiradical activity as compared to the p-amino phenyl substitution due to smaller O-H bond dissociation energy as compared to the N-H bond. From DPPH and DFT studies, it is suggested that the radical scavenging activity in 2-substituted thiophene is occurred through proton transfer mechanism. The other possible SET, SPLET mechanisms are also corroborated. Graphical Abstract Antiradical properties of trans-2-(4-substituted-styryl)-thiophene Anamika Gusain, Naresh Kumar, Jagdeep Kumar, Gunjan Pandey, Prasanta Kumar Hota.

Biodesulfurization of refractory sulfur compounds in petro-diesel by a novel hydrocarbon tolerable strain Paenibacillus glucanolyticus HN4.

One of the main precursors of air pollution and acid rains is the presence of the recalcitrant thiophenic compounds, for example dibenzothiophene (DBT) and its derivatives in transportation fuels. In an attempt to achieve the worldwide regulations of ultra-low sulfur transportation fuels without affecting its hydrocarbon skeleton, a biphasic medium containing 100 mg/L DBT dissolved in n-hexadecane (1/4 oil/water v/v) used for enrichment and isolation of selective biodesulfurizing bacterium from an oil-polluted sediment sample collected from Egyptian Red Sea shoreline. The isolated bacterium is facultative anaerobe, motile, spore-former, and mesophile. It is genetically identified as Paenibacillus glucanolyticus strain HN4 (NCBI Gene Bank Accession No. MT645230). HN4 desulfurized DBT as a model of the recalcitrant thiophenic compounds without affecting its hydrocarbon skeleton via the 4S-pathway producing 2-hydroxybiphenyl (2-HBP) as a dead end product. HN4 substantiated to be a hydrocarbon tolerant, biosurfactants(s) producer, and endorsed unique enzymatic system capable of desulfurizing broad range of thiophenic compounds and expressed an efficient desulfurization activity against the recalcitrant alkylated DBTs. As far our knowledge, it is the first reported BDS study using P. glucanolyticus. Statistical optimization based on One-Factor-At-A-Time (OFAT) technique and response surface methodology (RSM) applied for elucidation of mathematical model correlations describing and optimizing the effect of different physicochemical parameters on batch biphasic BDS process. That illustrated an approximate increase in BDS efficiency by 1.34 fold and recorded 94% sulfur removal in biphasic batch process at optimum operation conditions of 120 h, 0.14 wt% S-content model oil (DBT dissolved in n-hexadecane), 33.5 °C, pH7 and 1/1 oil/water phase ratio, and 147 rpm. Resting cells of HN4 in a biphasic reactor (1/1 v/v) decreased the sulfur content of a refractory thiophenic model oil (thiophene, benzothiophene, DBT, and alkylated DBT dissolved in n-hexadecane) from 0.14 to 0.027 wt%, and petro-diesel from 0.2 to 0.04 wt%, within 120 h, keeping the calorific value of the treated fuel intact. Consequently, that novel strain could be recommended as a promising candidate for BDS as complementary to hydrodesulfurization process in oil refinery.

Elimination of Thiophenic Compounds by Cycloaddition with Ethylene for an Efficient Purification of Fuels: A DFT Study

Using DFT calculations, we have investigated the cycloaddition of thiophene with ethylene, followed by desulfurization of the produced heterobicyclic molecules at 373 K. The whole reaction process has been modeled in three steps: (i) the molecule adsorption on tungsten sulfide acting as a catalyst, (ii) the cycloaddition of the adsorbed molecule with ethylene, (iii) the elimination of the sulfur atom by hydrogenation of the cycloaddition products. Cycloaddition, in the presence or in the absence of catalyst, produced a bicyclic compound including a C–S bond. Its reaction with hydrogen led to the hydrogenolysis of C–S bonds. Without catalyst, the reaction of bicyclic compounds with hydrogen led to a double hydrogenolysis producing cyclohexa-1,2-diene and hydrogen sulfur. In the presence of catalyst, the reaction took place in two steps, leading to cyclohexene. With increasing the molecular weight of compounds, cycloaddition can allow the separation between light hydrocarbons from alkyl-thiophenic molecules with distillation, knowing that boiling temperature increases with the molecular weight. Although consuming more hydrogen, the reaction with catalysts led to an unsaturated cyclic product which can improve the octane number of fuels containing them.

High Adsorption Performance of Bimetal Ag,Ti-Doped SiO2 Aerogel Composites for the Removal of Thiophenic Compounds from Model Fuels

Ag2O/SiO2–TiO2-n aerogel composites with different molar ratios of Si/Ti, prepared by a sol–gel method followed by the ambient pressure drying technique, were used for the adsorptive removal of thi...

Desulphurisation kinetics of thiophenic compound by sulphur oxidizing Klebsiella oxytoca SOB-1.

The major aims of this study are to determine the capability of sulphur oxidizing bacterium (SOB-1) to desulphurize dibenzothiophene (DBT) and crude oil, detection of the reaction kinetics and identify the proposed pathway of DBT desulphurization. The isolate was genetically identified based on 16S rRNA gene sequencing as Klebsiella oxytoca and deposited in the Genebank database under the accession number: MT355440. The HPLC analysis of the remaining DBT concentration revealed that, SOB-1 could desulphurize 90% of DBT (0·25mmoll-1 ) within 96h. The maximum production of sulphate ions from the desulphurization of DBT (0·36mmoll-1 ) and crude oil (0·4mmoll-1 ) could be quantitatively detected after 48h of incubation at 30°C. The high values of correlation coefficient (R2 ) obtained at all studied concentrations; suggested that biodesulfurization kinetics of DBT follows the first-order reaction model. The kinetics studies showed that, DBT may have an inhibitory effect on SOB-1 when the initial concentration exceeded 0·75mmoll-1 . The GC-MS analysis exhibited four main metabolites rather than DBT. The most important ones are 2-hydroxybiphenyl (2-HBP) and methoxybiphenyl n(2-MBP). Klebsiella oxytoca SOB-1 catalyzes the desulphurization of DBT through 4S pathway and forms four main metabolic products. The release of sulphate ion and formation of 2-HBP indicating the elimination of sulphur group without altering the carbon skeleton of DBT. The bacterial strain could also catalyzes desulphurization of crude oil. The desulphurization kinetics follows the first-order reaction model. Klebsiella oxytoca SOB-1 could be used as a promising industrial and environmental biodesulfurizing agent as it is not affecting carbon skeleton of thiophenic compounds and forming less toxic metabolic product (2-MBP).

Metal and sulfur removal from petroleum oil using a novel demetallization-desulfurization agent and process

Removal of metals and sulfur is a challenging operation during the crude refining that often is the bottleneck thereby increasing costs and reducing overall energy efficiency. Specifically, soluble sulfur and metal compounds containing vanadium and nickel are the most difficult to manage leading to problems such as: elevated corrosion, rapid catalyst deactivation, and potential human exposure and health impacts. In this study, a novel demetallization-desulfurization process has been developed to selectively extract metals about 36 metals including vanadium and nickel from the core of the porphyrin ring without removing or destroying the ring. This novel process utilizes bis(2-ethylhexyl) phosphoric acid as the demetallization-desulfurization agent (DM-DSA). The primary mechanism is that the DM-DSA acts as a proton donor and selectively removes metals from the core of the porphyrin ring, thereby permitting the oil yield to be unaffected. A further benefit is the reduction in the levels of thiophene compounds via a different extraction mechanism under the same reaction conditions. This proton donor is able to form an ionic liquid under reaction conditions that extracts thiophene compounds through hydrogen bonding and electrostatic force. The maximum removal efficiency measured was 90% and 79% for vanadium and nickel, respectively, and 53% for sulfur when bis(2-ethylhexyl) phosphoric acid was mixed and reacted and subsequently separated from Basra crude oil. The novel developed process herein is environmentally friendly “green” and cost-effective since no additional operations such as emulsification are required (limited energy input), no solvents are consumed during the reaction and oil yield is not impacted.

A kinetic study of HKUST-1 for desulfurization applications

In this study, HKUST-1 prepared under solvothermal conditions and tested in desulphurization of model gasoline. The prepared HKUST-1 samples were characterized using surface area and pore volume analysis (BET), powder X-ray diffraction (XRD), and Fourier transforms infrared spectroscopy (FTIR). The prepared HKUST-1 was used for desulphurization of model gasoline (thiophene with iso-octane), and the influence of the thiophene concentration, HKUST-1 dose, temperature, and contact time. The experimental results revealed that the sulfur content in model fuel was reduced from 1500-148.2 ppm (90.12% removal efficiency) for four hours contact time at 30 ?C. In addition, an isotherm adsorption and kinetics study were performed for a batch process to understand the system equilibrium (i. e., the best fitting Langmuir isotherm or Freundlich isotherm). The kinetics study proved that the contained sulfur removal was best fitted by pseudo-second-order kinetics. Regeneration results show that the HKUST-1 has a reversible nature as an adsorbent. Therefore, HKUST-1 might be used as a promising adsorbent for removing thiophene compounds from gasoline.

Adsorptive desulfurization of thiophene over Ti0.9Ce0.1O2 mixed oxide: A mechanistic study on the basis of XPS, in-situ FT-IR and TPD characterizations

The adsorption of thiophenic compounds over Ti0.9Ce0.1O2, an oxidatively regenerable sulfur adsorbent, was studied by XPS, DRIFT, and TPD-MS. Effect of the oxidative pretreatment on thiophene adsorption over Ti0.9Ce0.1O2 adsorbent, the adsorption site for thiophenic compound, and the role of surface Ce and Ti cations in the adsorptive desulfurization (ADS) were investigated. The results suggest that the surface oxygen plays an essential role in ADS and is a major active site for chemical adsorption of the thiophenic compounds. The surface Ce and Ti were further oxidized by the surface oxygen in the oxidative pretreatment, and then reduced during the adsorption of thiophenic compounds. This phenomenon is attributed to an electron transfer from the adsorbates to the surface Ce and Ti. It appears that the role of the surface Ce and Ti can accept electrons from adsorbate, and also contributes to producing the active oxygen to oxidize the sulfur atom of thiophenic compounds. An oxidative pretreatment, including oxidative regeneration, activates the surface oxygen to forms active oxygen species and oxidizes the surface Ce and Ti. Based on the results obtained, a possible mechanism was proposed for the chemical adsorption, dissociation and surface reaction of thiophene on Ti0.9Ce0.1O2 mixed metal oxide adsorbent.

Decomposition mechanism of thiophene compounds in heavy oil under supercritical water

Quantum chemistry and experiments are combined to explore the detailed decomposition mechanism of thiophene compounds. Under reaction medium of supercritical water (SCW), the desulfurization degree of 3- methyl thiophene is 7.38% higher than that of thiophene due to the presence of the methyl, and the sulfur atom embedded into dibenzothiophene is hardly removed as a result of the steric hindrance by phenyls. The C-S on thiophene ring is more easily broken via the annelation with water clusters. Once the open ring reaction of thiophene compounds occurs, the sulfur atom will be removed efficiently in the form of H2S. The analysis of products indicates that the SCW participates in the decomposition of compounds. Meanwhile the massive radicals produced by n-tetradecane pyrolysis can promote the decomposition of thiophene compounds, which causes the enethiolatel mainly to form thiols and thioethers.

Facile fabrication of a superior Cu(I)-NH4Y zeolite adsorbent for improving thiophene adsorption selectivity in the presence of aromatics or olefins

Cu modified Y zeolite adsorbents have performed excellent adsorption desulfurization performance. Adsorption selectivity of thiophenic sulfur compounds, however, still remained a lower level in the presence of aromatics and olefins. In this work, we aim to address the above challenge, using Cu(I)-NH4Y zeolites obtained by liquid phase ion-exchanged method. Based on the coordination chemistry theory, the new adsorption active sites ([Cu+···NH3···H+] species) can be facilely fabricated at lower temperature (ca. 150 °C) and under H2 atmosphere. The desulfurization experimental results indicate that the outstanding breakthrough sulfur capacity (ca. 31.0 mg (S) · g−1) can be achieved by the Cu(I)0.10-NH4Y adsorbent, which is about 2.3 folds as high as the best one reported. After regeneration with three cycles, the adsorbent still remains a high sulfur capacity. Importantly, the thiophene adsorption selectivities of adsorbent have been improved in the presence of aromatics or olefins, which are about 44.5% and 6.3%, respectively. Meanwhile, the direct “S-M” bonding mechanism between thiophene and [Cu+···NH3···H+] species can be really proposed. Besides, the alkylation reaction between thiophene and olefins is significantly attenuated, mainly ascribed to the majority of strong Brønsted acid sites being masked. The new design idea of effective active sites in the zeolite adsorbents breaks out the traditional high-temperature preparation concept of excellent desulfurization adsorbents and can provide a new direction in the future.

Enhancing oxidation resistance of Cu(I) by tailoring microenvironment in zeolites for efficient adsorptive desulfurization

The zeolite Cu(I)Y is promising for adsorptive removal of thiophenic sulfur compounds from transportation fuels. However, its application is seriously hindered by the instability of Cu(I), which is easily oxidized to Cu(II) even under atmospheric environment due to the coexistence of moisture and oxygen. Here, we report the adjustment of zeolite microenvironment from hydrophilic to superhydrophobic status by coating polydimethylsiloxane (yielding Cu(I)Y@P), which isolates moisture entering the pores and subsequently stabilizes Cu(I) despite the presence of oxygen. Cu(I) in Cu(I)Y@P is stable upon exposure to humid atmosphere for 6 months, while almost all Cu(I) is oxidized to Cu(II) in Cu(I)Y for only 2 weeks. The optimized Cu(I)Y@P material after moisture exposure can remove 532 μmol g−1 of thiophene and is much superior to Cu(I)Y (116 μmol g−1), regardless of similar uptakes for unexposed adsorbents. Remarkably, Cu(I)Y@P shows excellent adsorption capacity of desulfurization for water-containing model fuel.

Direct sulfur-containing compounds analysis in petroleum via (+) ESI FT-ICR MS using HBF4 as ionization promoter

Molecular-level characterization of sulfur-containing compounds has attracted particular attention due to its relative high abundance and negative impact on the refining process. In this paper, a novel analytical method for selective ionization of sulfidic and/or isolated thiophenic compounds (thiophene rings that are not condensed with aromatic systems) and condensed thiophenic compounds (thiophene rings that are condensed with aromatic systems, DBE ≥ 6, DBE = number of rings plus double bonds to carbon) in petroleum samples was developed by using fluoroboric acid (HBF4) as ionization promoter. Positive-ion electrospray ionization [(+) ESI] Fourier transform ion cyclotron resonance mass spectrometry was followed to characterize the molecular composition. Sulfidic and/or isolated thiophenic compounds were mainly ionized as protonated molecular ions ([M+H]+), while condensed thiophenic compounds (DBE ≥ 6) were mainly ionized as molecular radical cations (M+). The method was validated by various sulfur-containing model compounds and then applied to vacuum gas oil, crude oil and heavy oil samples. (+) ESI coupled with HBF4 additive is a simple method for selective ionization of sulfides and thiophenes in high-sulfur-content petroleum samples and has the potential for the characterization of sulfides and thiophenes in other complex mixtures.

Metal-free oxidative desulfurization over a microporous triazine polymer catalyst under ambient conditions

A metal-free microporous triazine polymer (MCTP) was applied as a heterogeneous catalyst for the oxidative desulfurization (ODS) of thiophenic sulfur compounds in decane as a model fuel. Using a molecular oxygen (O2)/aldehyde system as the oxidant, complete removal of dibenzothiophene (DBT) from a 400 ppm DBT solution (10 mL) was achieved at room temperature in 15 min with 2 mmol of isobutyraldehyde (IBA). The highly efficient conversion of the DBT was explained by the formation of an acyl radical from IBA aided by the MCTP catalyst, which was converted to a peroxyacid that oxidized the DBT to DBT sulfone. The conversion efficiency of thiophenic compounds followed the sequence of electron densities in the individual S atoms: DBT > benzothiophene > thiophene. The MCTP catalyst could be reused for ODS for at least five consecutive runs without any reduction in the catalytic performance after a simple acetone wash.

Gas adsorptive desulfurization of thiophene by spent coffee grounds-derived carbon optimized by response surface methodology: Isotherms and kinetics evaluation

Abstract The elimination of sulfur compounds in the FCC gasoline is indispensable to protect downstream equipment. Researchers are trying to find technological innovations to produce the famous “zero sulfur” fuel. Many adsorbents, such as spent coffee grounds-derived carbon (SCG-AC), have been claimed to be effective in H2S removal. However, no study has been conducted to exploit its ability to eliminate the organo-sulfur compounds present in FCC gasoline such as thiophene. This work involves the optimization by the response surface methodology (RSM) of different operating conditions of activated carbon (AC) production by the chemical activation (H3PO4) of SCG. RSM was used to estimate the variables considered in the preparation of AC using the Box–Behnken Design (BBD). The optimized SCG-AC was used for the adsorption of thiophene through batch tests at ambient conditions. The equilibrium experimental data of the thiophene adsorption were analyzed by Langmuir, Freundlich, and Langmuir–Freundlich isotherms. The adsorption isotherm data fit the Langmuir–Freundlich isotherm where the adsorption’s kinetics were described by the Elovich model. The optimum SCG-AC exhibited the highest adsorption capacity, with up to 2.23 mmol/g. These results revealed that SCG-AC is a promising and economical adsorbent for the elimination of thiophenic sulfur compounds.

Molecular design and comprehensive evaluation of solvents capable of simultaneously extracting multiple active substances

It is of great significance to obtain an ionic liquid with the excellent extraction performance on multiple active components. In this work, a comprehensive evaluation and screening model of ionic liquid extractants is established, which could screen and comprehensively evaluate the performance of ionic liquids to remove thiophene compounds (thiophene, benzothiophene, dibenzothiophene) in fuel oil. Based on COSMO-SAC, the model calculated the infinite dilution activity coefficients of 124 ionic liquids, and obtained the solubility and selectivity data of 372 groups of ionic liquids for thiophenes. The extraction effect of ionic liquid was comprehensively evaluated by the entropy weight function and fuzzy comprehensive evaluation function. This model solves the problem that the extraction effects of different ionic liquids cannot be compared because the same ionic liquid has different extraction effects on different sulfur-containing impurities. Finally, 36 ionic liquids with the best comprehensive extraction effect were screened.

Synthesis and molecular modeling of novel bio-functional moieties derived from 2-cyanoacetamide-3,4,5-substituted thiophene as human carcinoma growth inhibitors

Synthesis of novel bio-functional substituted-thiophene scaffolds (3−15) employing the previously obtainable 2-cyanoacetamide-3, 4, 5-substitued thiophene compound (1) is described through its tandem nucleophilic and cyclization reactions. The structures of the novel compounds are confirmed by micro and spectroscopic analyses. The reactive chemical and biological sites in the molecules are illustrated by computational assay based on their frontier molecular orbitals (FMO’s) study. The synthesized compounds are examined in vitro against selected human cell lines of primary liver cancer (HEPG-2) and mammary gland carcinoma (MCF-7). The preliminary bioassay results indicate that the tested compounds exhibit variable degrees of inhibiting tumors growth respected to their structures.

Adsorption of DBT and 4,6-DMDBTon nanoporous activated carbons: the role of surface chemistry and the solvent.

Adsorption of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) from solutions in hexane and hexadecane respectively as well as in acetonitrile for both thiophenic compounds was investigated with sorbents of three activated carbons and their oxidized counterparts. The raw sorbents were of different surface acidity. Oxygen surface groups created after oxidation increased the adsorption of thiophenic compounds via polar interactions.

Separation and characterization of squalene and carotenoids derived sulfides in a low mature crude oil

An unusual distribution on molecular composition of organic sulfur compounds (OSCs) was found in a crude oil from the Bohai Bay Basin (China) that contains negligible thiophenic sulfur compounds but abundant in C30 and C40 sulfides. The sulfides were separated from the crude oil by methylation/demethylation method and characterized by gas chromatography-mass spectrometry (GC–MS) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). A novel series of C30 OSCs that possess a bio-precursor of squalene were identified. The lexene (C33) derived OSC was also identified for the first time in the crude oil, which indicates a strictly anaerobic condition during the early diagenesis of the source rock. Most C40 sulfur compounds were verified to be sulfides having a β-carotane skeleton. Most identified sulfides possess a thiolane group with a quaternary carbon atom or a thiane group within their carbon skeletons.