Atom Of Thiophene Research Articles

Removal of thiophene from model oil by polyethylene glycol via forming deep eutectic solvents

Abstract The removal of organosulfurs from liquid fuel has become a hot issue due to the serious environmental pollution by sulfur oxide gases. In this study, the removal of thiophene from model oil was carried out using polyethylene glycol (PEG). It was found that deep eutectic solvents formed by PEG as hydrogen bond donor and thiophene as hydrogen bond acceptor could efficiently separate thiophene from model oil. The influencing parameters in this process were discussed, such as extraction time, temperature, mass ratio of PEG to oil, and initial sulfur concentration. The results showed that the single extraction efficiency of PEG-200 and PEG-400 could reach up to 89.0% and 97.1% in optimal conditions, respectively. The extraction efficiency as high as 95.7% and 99.9% could be achieved after three extraction cycles. The kinetic equation of the extractive desulfurization was studied by in situ infrared (IR), and the kinetic constant k 1 of PEG-400 and PEG-200 was compared (k 1(PEG-400) > k 1(PEG-200)). The desulfurization mechanism of PEG was studied by IR, 1H NMR spectra, and density functional theory (DFT). The results showed that the hydrogen bond formed between hydroxyl hydrogen in PEG and sulfur atom in thiophene accounted for the high extraction efficiency.

Appropriate active-site in [Mo3S(S2)6]2− or [Mo2(S2)6]2− clusters for catalysis of thiophene hydrodesulfurization

Through a facial immersion method, thiomolybdates [Mo3S(S2)6]2 − and [Mo2(S2)6]2 − clusters have been successfully anchored on SBA-15, and the loaded catalyst was characterized by various methods. The terminal/bridging sulfur atoms on the sulfide cluster have a strong tendency to combine with H atom and then transferred to the S atom of thiophene for hydrodesulfurization. The catalytic activity and desulfurization selectivity of the supported catalysts Mo3S13/SBA-15 and Mo2S12/SBA-15 were investigated at different temperature and different time. Direct hydrogenation of thiophene occurs presumably with the participation of –SH groups, produced from the opening of S–S bridges by hydrogen. And the desulfurization of thiophene occurs presumably with the breaking of C–S bond and formation of C-OH bond for the product is butanol. Mo3S13/SBA-15 and Mo2S12/SBA-15 display excellent catalytic performance. The conversion rate of thiophene is about 97% for Mo3S13/SBA-15 and 94% for Mo2S12/SBA-15, while the desulfurization selectivity is about 97% (Mo2S12/SBA-15) and 82% (Mo3S13/SBA-15).

A near-infrared and lysosomal targeting thiophene-BODIPY photosensitizer: Synthesis and its imaging guided photodynamic therapy of cancer cells

In this study, a novel NIR and lysosomal targeting thiophene-BODIPY photosensitizer SBOP-Lyso was synthesized to explore its potential applications in photodynamic therapy of A549 cells. In the strategy of designing SBOP-Lyso, S atom in thiophene as well as heavy atom I were introduced to promote ISC efficiency to ensure high singlet oxygen yield. A common lysosome targeted group (M1: 1-(2-morpholinoethyl)-1H-indole-3-carbaldehyde) was linked to SBOP to extend its wavelength to the NIR region. Its absorption peak was at 660 nm (εmax = 5.2 × 104 cm−1 M−1) and its corresponding emission peak was located at 705 nm. Singlet oxygen could be quickly generated by SBOP-Lyso in the presence of 660 nm LED irradiation and the singlet oxygen yield was up to 44.1%. In addition, it also had good biocompatibility and could enter cells or zebrafish in a short time. SBOP-Lyso had negligible dark cytotoxicity (cell survival rate > 80%) and excellent phototoxicity (IC50 = 0.2 μM). DCFH-DA (ROS indicator) proved that SBOP-Lyso could generate singlet oxygen with 660 nm LED irradiation. Singlet oxygen produced by SBOP-Lyso could kill cancer cells in PDT process and it had the ability to effectively inhibit A549 cells migration. Besides that, lysosomal colocalization assay showed that it had good lysosomal localization ability (Pearson colocation coefficient, R = 0.93). Considering the above results, SBOP-Lyso as a unique lysosome-targeted photosensitizer with excellent properties would exhibit positive results in PDT process of cancer cells.

Removal of thiophene in air stream by absorption combined with electrochemical oxidation

Abstract As typical heteroaromatic compounds, thiophene is an air pollutant that pose serious environmental and health related impacts due to its volatility and toxicity. This work reports a hybrid process of absorption combined with electrochemical oxidation to degrade thiophene. The ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4) was employed as the absorbent to capture thiophene from air stream. Linear sweep voltammetry (LSV) demonstrated that thiophene could be oxidized on β-PbO2 anode modified with fluoride at 1.28 V versus Ag/Ag + electrode (RE) with a scan rate of 100 mV/s while [BMIM]BF4 was used as the electrolyte. Results of bulk electrolysis showed that thiophene could be thoroughly degraded within 60 min in [BMIM]BF4 under 50 mA/cm2 due to the successive attack of hydroxyl radicals (·OH) produced by electrolysis on the surface of β-PbO2 anode. Acetic acid was determined as the main intermediate and could be further mineralized to fumaric acid, maleic acid and oxalic acid, while sulfur atom in thiophene was finally converted to sulfate ions (SO42−). Based on the HPLC analysis and a precipitation of BaSO4, degradation pathway of thiophene was proposed and the thiophene sulfur could be degraded completely into sulfate. The kinetics of the electrochemical oxidation process for thiophene can be described by the pseudo-first order model. This absorption-electrochemical oxidation method with continuous operation would be a promising way for the clean and safe removal of heteroaromatic compounds from waste gases.

Density Functional Theory Investigation on Thiophene Hydrodesulfurization Mechanism Catalyzed by ReS2 (001) Surface

We present density functional theory calculations on the reaction mechanism of thiophene hydrodesulfurization (HDS) over ReS2 (001) surface under typical HDS reaction conditions. It is found that thiophene adopts an “upright” adsorption configuration with the binding energy of 1.26 eV. Considering the factors such as Bader charge, two reaction mechanisms, named direct desulfurization (DDS) to the product of butadiene and hydrogenation (HYD) to 2-butene, 1-butene, and butane, are systematically investigated. Results show that H prefers to attack thiophenic C before the first C–S bond rupture but begins to hydrogenate ST (S atom of thiophene) after ring-opening. Prehydrogenation has different effect on the activity of C–S bond breaking. When the ring is intact, it has nominal effect; but when the ring is open, appropriate prehydrogenation can dramatically decrease the energy barrier while complete hydrogenation makes the barrier rise again due to stereohindrance effect. The DDS mechanism is proved to be kin...

Adsorption Desulfurization on a Nanocrystalline NaY Zeolite Synthesized Using Carbon Nanotube Templated Growth

FAU-type (NaY) zeolite nanocrystals have been synthesized through crystallization of gel in a mesoporous system of carbon nanotubes (CNTs) with an internal diameter of 20–30 nm. Investigation using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM) shows that the nanocrystals possess the typical nanosized zeolite structural characteristics, which are different from those of microsized zeolites. Desulfurization of various model fuels containing about 500 ţg/g sulfur was studied over the synthesized nanosized NaY with a liquid hourly space velocity of 7.5 hr−1 at ambient conditions. The sulfur adsorption capacity was 7.2, 1.7, 6.7, 6.9, and 6.5 mg(S)/g adsorbent for thiophene, tetrahydrothiophene (THT), dibenzothiophene (DBT), 4-methyldibenzothiophene (4-MDBT), and 4,6-dimethyldibenzo-thiophene (4,6-DMDBT), respectively. The charges on the S atom in thiophene, THT, DBT, 4-DMDBT, and 4,6-DMDBT, calculated using density functional theory (DFT), were −0.159, −0.298, −0.211, −0.188, and −0.214, respectively, implying that the S-M bond between the adsorption sites and these sulfides is much weaker than other bonds (maybe due to π complexation).

Deep Desulfurization of Model Gasoline by Adsorption on Mesoporous CeMCM-41

Cerium atoms have been introduced into the framework of MCM-41 by a hydrothermal synthesis method with cetyltrimethylammonium bromide (CTMABr) as template, sodium silicate as silica source, and cerium chloride as cerium source. Desulfurization of various model fuels containing about 500 μg/g sulfur were studied over the synthesized CeMCM-41 with a liquid hourly space velocity of 7.5 hr−1 at ambient conditions. The sulfur adsorption capacity was 10.0, 11.8, 14.0, and 15.4 mg(S)/g adsorbent for thiophene, dibenzothiophene (DBT), 4,6-dimethyldibenzothiophene (4,6-DMDBT), and tetrahydrothiophene (THT), respectively. The charges on S atom in thiophene, DBT, 4,6-DMDBT, and THT, calculated by using density functional theory (DFT), are −0.159, −0.211, −0.214, and −0.298, respectively, implying that the S-M bond between the adsorption sites and thiophene is much weaker than that between the adsorption sites and DBT, 4,6-DMDBT, or THT.

Adsorptive desulfurization on a heteroatoms Y zeolite prepared by secondary synthesis

Gallium atoms have been introduced into the framework of Y zeolite by treating the zeolite with an aqueous solution of ammonium hexafluoro gallate. Desulfurization of various model fuels containing about 500 μg/g sulfur has been studied over the synthesized Y zeolite ([Ga]AlY). The sulfur adsorption capacity is 7.0, 17.4, 14.5, 16.9, 6.9 and 5.8 mg(S)/g adsorbent for thiophene, tetrahydrothiophene (THT), 4,6-dimethyldibenzothiophene (4,6-DMDBT), dibenzophiophene (DBT), benzothiophene (BT) and 4-methyldibenzothiophene (4-MDBT), respectively. The charges on the S atom in thiophene, THT, 4,6-DMDBT, DBT, BT and 4-MDBT, calculated using the density functional theory (DFT), are −0.159, −0.298, −0.214, −0.211, −0.193 and −0.188, respectively, implying that the S-M bond between the adsorption sites and thiophene is much weaker than that between the adsorption sites and THT, 4,6-DMDBT or DBT. The sulfur removal of FCC gasoline on [Ga]AlY is 68%.

Density functional theory study on adsorption of thiophene on TiO 2 anatase (0 0 1) surfaces

In order to develop a fundamental understanding of the adsorption mechanism of thiophenic compounds on TiO 2-based adsorbents for ultra-deep desulfurization of liquid hydrocarbon fuels, a density functional theory (DFT) study was conducted on the adsorption of thiophene over the TiO 2 anatase (0 0 1) surface. The perfect, O-poor (with oxygen vacancies), and O-rich (with activated O 2 on the surface) anatase (0 0 1) surfaces were built, and the interaction of thiophene molecule with these surfaces was examined. The adsorption configuration and adsorption energy on the different surfaces and sites were estimated. The results showed that thiophene may be adsorbed on both the perfect and O-poor surfaces through an interaction between the Ti cations on the surface and the S atom in thiophene, whereas on the O-rich surface through an interaction of the activated O atoms (the dissociatively or associatively adsorbed O 2) on the surface with the S atom in thiophene to form a sulfone-like surface species. The adsorption of thiophene on the O-rich surface is significantly stronger than adsorption on the perfect and O-poor surfaces on the basis of the calculated adsorption energies. The results indicate that the activated O 2 on the TiO 2 anatase (0 0 1) surface may play an important role in the adsorption desulfurization over the TiO 2-based adsorbents, and increased concentration of the activated O 2 on the surface may result in improvement of the adsorption capacity of the adsorbents.

Deep desulfurization by selective adsorption on a heteroatoms zeolite prepared by secondary synthesis

Gallium atoms have been introduced into the framework of Y zeolite by treating the zeolite with an aqueous solution of ammonium hexafluoro gallate. Desulfurization of various model fuels containing about 500 μg/g sulfur were studied over the synthesized Y zeolite ([Ga]AlY) with a liquid hourly space velocity of 7.2 h−1 at ambient conditions. The sulfur adsorption capacity was 7.0, 14.5, and 17.4 mg(S)/g adsorbent for thiophene, 4,6-dimethyldibenzothiophene (4,6-DMDBT), and tetrahydrothiophene (THT), respectively. The charges on S atom in thiophene, 4,6-DMDBT and THT, calculated by using density functional theory (DFT), are −0.159, −0.214 and −0.298, respectively, implying that the S–M bond between the adsorption sites and thiophene is much weaker than that between the adsorption sites and THT or 4,6-DMDBT.

An Anisotropic United Atoms (AUA) Potential for Thiophenes

The optimization of the parameters of the Lennard-Jones (LJ) 12-6 potential of the sulfur atom in thiophene has allowed the AUA 4 potential to be successfully extended to alkyl and polythiophenes. Monte Carlo Gibbs ensemble and grand canonical simulations combined with histogram reweighting techniques have been performed to investigate the resulting phase equilibrium and the critical region of different molecules of this family in order to test the proposed potential. Excellent agreement with experimental densities, enthalpies of vaporization, and saturation pressures has been obtained in most of the cases. In particular, the critical point of our model for thiophene has been located with a statistical precision of less than 0.1% and is within 1% of the experimental value. The calculation of the critical points has been made through a recently implemented methodology based on the calculation of a fourth order cumulant (Binder parameter) combined with the use of finite size scaling methods, allowing the critical points to be located in a straightforward and accurate way.

Selectivity of Thiophene/Toluene Competitive Adsorptions onto Zeolites. Influence of the Alkali Metal Cation in FAU(Y)

In the framework of research considering adsorption for gasoline desulfurization purposes, dynamic adsorption experiments have been performed to study a comparison between thiophene and toluene affinities toward Y-faujasite adsorbents (Si/Al = 2.4) exchanged with various alkali metal cations (Li+, Na+, K+, Rb+, Cs+). These experiments have been carried out at two concentration ranges in liquid n-heptane solutions: around 25 mmol·L-1 for competitive adsorptions and around 1.25 mmol·L-1 for single-solute adsorptions. Complementary microcalorimetry studies have been carried out in order to investigate the interaction of nucleophilic compounds toward alkaline Y zeolites, by measuring the adsorption enthalpy of CCl4 onto NaY and CsY sorbents. The results clearly exhibit two opposite trends for the adsorption of thiophene and toluene molecules onto alkaline Y faujasites. The thiophene affinity increases with cation electropositivity, while the toluene affinity decreases as the cations are more electropositive. Thus, from a favorable adsorption for toluene onto the LiY zeolite (αthio/tol = 0.38 at ca. 26 mmol·L-1), the selectivities shift in favor of thiophene so that the αthio/tol value reaches 3.00 with the CsY zeolite. The calorimetry measurements of CCl4 adsorption have exhibited an increase of the adsorption enthalpy with more electropositive cations, which seems to indicate that thiophene molecules are adsorbed similarly to CCl4, i.e., by strong interaction between the nucleophilic S atom of thiophene and the cationic charge. However, toluene should be mainly stabilized on the adsorption sites through other interactions, as combined attractions between the H atoms of toluene and the O atoms of the zeolite framework surrounding the SII cation can be suggested.

Enhanced Efficiency of Polymer Light-Emitting Diodes by Dispersing Dehydrated Nanotube Titanic Acid in the Hole-buffer Layer

Efficiency of polymer light-emitting diodes (PLEDs) with poly(2-methoxy-5-(2-ethyl hexyloxy)-p-phenylene vinylene) (MEH-PPV) as an emitting layer was improved if a dehydrated nanotubed titanic acid (DNTA) doped hole-buffer layer polyethylene dioxythiophene (PEDOT) was used. Photoluminescence (PL) and Raman spectra indicated a stronger interaction between DNTA and sulfur atom in thiophene of PEDOT, which suppresses the chemical interaction between vinylene of MEH-PPV and thiophene of PEDOT. The interaction decreases the defect states in an interface region to result in enhancement in device efficiency, even though the hole transporting ability of PEDOT was decreased.

The rotational spectrum of thiophene⋯HBr and a comparison of the geometries of the complexes B⋯HX, where B is benzene, furan or thiophene and X is F, Cl or Br

The ground-state rotational spectra of three isotopomers C4H4S⋯H79Br, C4H4S⋯H81Br and C4H4S⋯D79Br of a weakly bound complex formed by thiophene and hydrogen bromide have been observed in the gas phase by means of a pulsed-jet, Fourier-transform instrument. Each spectrum was analysed and fitted to give rotational constants A0, B0 and C0, centrifugal distortion constants ΔJ, ΔJK, ΔK, δJ and δJK and the components χaa, χbb − χcc and χab of the bromine nuclear quadrupole coupling tensor. A detailed analysis of the spectroscopic constants established that the geometry of the complex is of the face-on type. The Br atom of HBr is located close to the perpendicular drawn through the centre of mass of the thiophene ring and the H atom of HBr lies between the Br atom and the ring. The angle αaz made by the HBr internuclear axis z with the a-axis has the two possible values ±9.83°. The preferred structure is that generated when the positive value of the angle is chosen and has the HBr sub-unit pointing in the direction of the S atom of thiophene. The determined geometrical parameters are r(S⋯H) = 2.728(3) A, ϕ = 116.0(2)° and θ = 7.08(4)°, where ϕ is the angle made by the S⋯H internuclear line with the local C2 axis of thiophene and θ is the angular deviation of the S⋯H–Br nuclei from collinearity.

Adsorption of thiophene and 2,5-dimethylthiophene on Au [formula omitted] from ethanol solutions

The formation of thin films by the adsorption of thiophene (TP) and 2,5-dimethylthiophene (DMTP) on Au(1 1 1) in 1 mM ethanol solutions was investigated by X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM). XPS and STM studies revealed that the adsorption of TP molecules on Au(1 1 1) gives rise to the formation of two-dimensional ordered self-assembled monolayers through chemisorption between the sulfur atom in TP and the gold surface, while the adsorption of DMTP molecules having two methyl groups at 2,5-positions of the TP ring leads to the formation of physisorbed multilayers having a liquid-like phase. These results indicate that two methyl groups at 2,5-positions of the TP ring significantly affect the growth process of the thin film, which strongly reflect that interactions between the sulfur atom in the TP ring and gold play an important role in adsorption process of molecules.

Theoretical study of the structural, vibrational, and topologic properties of the charge distribution of the molecular complexes between thiophene and Brönsted acid sites of zeolites

AbstractThe main interaction between thiophene and zeolites leads to the formation of a hydrogen bond between the S atom of thiophene and the OH group of zeolites, giving 1:1 stable molecular complexes. The present work reports a theoretical study about the structural, vibrational, and topologic properties of the charge distribution of the molecular complexes between thiophene and a series of Brönsted acid sites of zeolites, modeled as the H3SiOHAlH3(B1), (OH)3Si(OH)Al(OH)3(B1OH), and H3Si(OH)Al(OH)2OSiH3(B2) clusters. The studied properties were calculated at a Hartree–Fock level with the standard 6‐31+G(d,p) basis set. Additionally, electron correlation effects for geometric and vibrational properties were evaluated at second‐order Møller–Plesset (MP2) and BLYP for B1–thiophene complex, whereas the BLYP technique was employed for the complexes of thiophene with B1OH and B2 clusters. Symmetry restriction was considered for structure calculations, beingC2vfor thiophene,Csfor zeolite clusters, andCslinear conformation for the complexes. It was found that these linear thiophene–zeolite complexes reproduce the tendencies in the experimental frequency shifts of the OH vibration mode from the adsorption of thiophene in ZSM5 zeolites. The topologic properties of the complexes give a pattern for the interaction of thiophene–zeolite. The results are compared with previous ones from silanol–thiophene calculations. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001

The importance of sulphur3s̄ulphur bonding in the hydrodesulphurization process of thiophene, using transition metal sulphide catalysts

Transition metal sulphides are widely used as catalysts for the hydrodesulphurization (HDS) process of thiophene and related compounds. It is generally believed that, during adsorption of thiophene onto vacant sulphur sites on the surface of the catalyst, strong σ and π bonds are formed between the thiophene sulphur and catalyst metal atoms, with strong metal d and sulphur p character. From a series of scattered-wave electronic structure calculations on Ni-promoted MoS 2—thiophene complexes for which the separation between the thiophene molecule and the catalyst is systematically varied, we show that metal—sulphur bonding is weak during adsorption. Strong interactions between the sulphur atom in thiophene and the sulphur atoms in the catalyst, operative at relatively large thiophene—catalyst separations, lead to weak binding of thiophene to the catalyst. A new mechanism for the adsorption of thiophene, not requiring sulphur vacancies on the surface of the catalyst, and based on sulphur—sulphur bonding, is proposed. It is shown that this adsorption mechanism can be an integral part of the overall HDS process if it occurs along the edges of (promoted) MoS 2 catalysts.

A quantum-chemical study of site modeling for the adsorption and desulfurization of thiophene

The active site of MoS 2 is modeled to obtain information on the initial steps of thiophene hydrodesulfurization. The model consists of a MoS 3H + 3 cluster with three anionic vacancies. Quantum-chemical extended Hückel theory studies were carried out on the adsorption and desulfurization steps for different geometries of the complex between the site and thiophene. The calculations show that the vertical adsorption of the S atom of thiophene on the Mo atom of the model catalyst is favored over any horizontal adsorption. In every case adsorption weakens the CS thiophene bonds. Desulfurization by straight rupture of these bonds to form a C 4H 4 radical leads to a moderate activation barrier. This theoretical approach to the problem, initially based on available data, leads to conclusions which are in good agreement with experimental results.

Quantum Chemical Studies of the Adsorption of Thiophene on MOS2 Hydroprocessing Sites

AbstractThe modelisation of an HDS site from the MoS2 structure is undertaken in order to understand the desulfurisation of thiophene. Depending on the number of coordinative unsaturation degrees (one, two and three anionic vacancies) and on their stoechiometry (Mo3S13H12”, MOS5H5”, MOS5H4”, MOS4H4 and MOS3H3+) these models may represent sites on basal planes, edges, or corners of the MOS2 crystal.Different types of adsorption (vertical, horizontal, on S, on the hetero‐cycle and on one pi bond) of the thiophene molecule on the different model sites are computed using the EHT quantum chemical method. The comparison of the adsorption energy curves obtained by approaching thiophene near the site shows that the vertical one point adsorption of the S atom of thiophene is prefered over any. This adsorption step can be readily followed by a desulfurization process supposing C4H4 radical is an intermediate. These theoretical predictions agree with different conclusions of the literature. The MOS4H4 model seems to be the best choice for the site.

Structure and degree of aromatic character in furan, pyrrole, and thiophene

The ab initio gradient method has been used to optimize the geometries of furan, pyrrole, and thiophene by SCF ab initio computation. The effect of augmenting a 4–21 split valence shell basis set by addition of d functions to oxygen, nitrogen, and sulfur has been investigated, and for furan a basis set including d functions on all heavy atoms has been used. The use of polarization functions is necessary to obtain realistic CO and CS bond distances, but otherwise any differences are minimal. Electron density difference plots give a graphic illustration of the basis set effects. The question of relative aromatic character of these compounds is investigated by means of Mulliken population analysis of the π electron distributions, determination of the spatial extent of the localized orbitals involved in the electron delocalization, determination of the deviations of bond lengths from typical single and double bond values, and plots of total electron density in planes parallel to, but far enough removed from, the molecular plane that the density is dominated by the contribution from the molecular π system. Extensive conjugation within the CCCC portion of the ring is found for all three compounds, but the ability to obtain true “aromatic” character by extension of this conjugation over the heteroatom is found to depend markedly on the size of the heteroatom. In pyrrole, the nitrogen atom is of ideal size to permit extension of the conjugation around the entire ring, and aromatic character is maximized. The oxygen atom in furan is too small and the sulfur atom in thiophene is too large to facilitate complete cyclic conjugation. It is suggested that electron delocalization within a portion of the ring does not constitute “aromaticity”, but rather a system is required such that the conjugation can extend completely around the ring.