Oxidation of Benzothiophenes Using Tert-amyl Hydroperoxide

Homogeneous oxidation using an oil-soluble oxidant, tert-amyl hydroperoxide （TAHP）, for ultra-deep desulfurization was performed under mild conditions in the presence of molybdenum oxide catalysts. Dibenzothio- phene （DBT）, benzothiophene （BT） and 4, 6-dimethyl-dibenzothiophene （DMDBT）, which are the refractory sulfur compounds for hydrodesulfurization （HDS）, were employed as model substrates for a simulated diesel fuel. Activity of molybdenum oxide supported on a macroporous weak acidic resin was investigated. The mass conversion of DBT reached near 100% at 90℃ and a TAHP/DBT molar ratio of 3 with 1% of molybdenum oxide supported on Amberlite IRC-748 resin for 1 h. It was further found that the activities of the model substrates decreased in the or- der of DMDBT 〉DBT 〉BT. In the flow oxidation using TAHP as the oxidant, mass conversion of DBT increased remarkably from 61.3% to 98.5% when dropping the weight hourly space velocity （WHSV） from 40 h^-1 to 10 h^-1. A series of experiments dealt with selectivity of this oxidation using TAHP revealed that the model unsaturated compounds, i.e. 4, 6, 8-trimethyl-2-nonylene, and 2-methylnaphthalene did not affect the oxidation of DBT. Carbazole had nearly no effect on the conversion of DBT using TAHP, but had some influence on the one using tert-butyl hydroperoxide （TBHP）. The mass conversion of DBT decreased remarkably from 75.2% to 3.6% when the content of carbazole increased from 0 to 500μg·g^-1. In the flow oxidation using TAHP as the oxidant, the concentration of DBT in model fuels was reduced from 500 μg·g^-1 to 7.2 μg·g^-1 at WHSV of 10 h^-1, and then reduced to 3.8 μg·g^-1 by adsorntion of Al2O3.

PHOTOCHEMICAL OXIDATION OF BENZOTHIOPHENE IN SEAWATER

Kinetic investigation into the phogochemical oxidation of benzothiophene in seawater showed that photo-oxidation rates of benzothiophene were influenced by the medium,pH,heary metal ion,dissolved oxygen,and light intensity.The photo-oxidation of benzothiophene followed the first order reaction law, with the rate constants ranging from 1.21×10 -5 /s to 5.38×10 -5 /s.An interesting observation was that the presence of Hg 2+ could markedly enhance the photo-oxidation rate of benzothiophene in seawater;and that the photo-oxidation rate of benzothiophene increased with light intensity.The effect of oxygen on the rate constant for benzothiophene photolysis was also observed.Compared with purging with nitrogen,purging seawater with oxygen evidently increased the photolysis rate of benzothiophene. Based on this observation,a benzothiophene photo-oxidation mechanism including singlet oxygen (O 2 1 Δ g) was suggested.Two photolysis products of benzothiophene were identified.The photolysis of benzothiophene is considered to be important in the removal of this compound in seawater.

The First Principle Study on the Rectification of Molecular Junctions Based on the Alkyl-chain-modified Phenyl Benzothiophene Derivative

Using density functional theory（DFT） combined with nonequilibrium Green＇s function investigates the electron-transport properties of several molecular junctions based on the PBTDT-CH=NH molecule, which is modified by one to four alkyl groups forming PBTDT-（CH2）nCH=NH. The electronic structures of the isolated molecules（thiol-ended PBTDT-（CH2）nCH=N） have been investigated before the electron-transport calculations are performed. The asymmetric current-voltage characteristics have been obtained for the molecular junctions. Rectifying performance of Au/S-PBTDT-CH=N-S/Au molecular junction can be regulated by introducing alkyl chain. The N3 molecular junction exhibits the best rectifying effect. Its maximum rectifying ratio is 878, which is 80 times more than that of the molecular junction based on the original N molecular junction. The current-voltage（I-V） curves of all the sandwich systems in this work are illustrated by transmission spectra and molecular projection density analysis.

ANALYSIS AND DISTRIBUTION FEATURES OF BENZOTHIOPHENE IN SEDIMENTS OF NANSHA ISLANDS SEA AREA

This work yielded an improved method for extracting and analysing benzothiophene in marine sediment.The detation limit was 0.05 ng S of benzothiophene, with precision of 8%. Benzothiophene was found in Nansha Islands sea area sediments and ranged from 1.1 -6.8 ng per gram dry sediment. Its concentration was closely correlated to hte organic carbon content in the sediment.Several source processes of benzohtiophene are discussed in this paper.

SORPTION OF BENZOTHIOPHENE ON MARINE SEDIMENTS

The sorption behavior of benzothiophene on marine sediments treated by different procedures was studied. Linear sorption isotherms were found for sorption of benzothiophene by no treatment and NaOAC-HOAC treatment sediments. The ediment treated by NaOAC-HOAC exhibited obviously larger Kp value for benzothiophene. The observed Koc value was basically consistent with the value predicted from the benzothiophene solubility in water. Nonlinear isotherms were observed for adsorption of benzothiophene on the sediments treated by H2O2 and could be described by the Freundlich equation.

Removal of Benzothiophene by Extraction with Deep Eutectic Solvents[Bmim]Br-Polyalcohol

Deep eutectic solvents(DESs)1-butyl-3-methylimidazolium bromide-polyalcohol([Bmim]Br-polyalcohol)were synthesized from[Bmim]Br and polyalcohol such as ethylene glycol(EG),propylene glycol(PG),glycerol(GL)at a molar ratio of 1:2.[Bmim]Br-2propylene glycol([Bmim]Br-2PG)was characterized with FT-IR spectroscopy and 1H NMR.The removal of benzothiophene(BT)from model oil was investigated by extraction with DES[Bmim]Br-2PG.The results showed that an extraction efficiency as high as 54.1%could be achieved with the solvent in one-stage extraction at 30℃in 30 min with a DES/oil mass ratio of 1:1.Deep desulfurization was realized after five-stage extraction,and sulfur content in model oil was reduced to less than 10μg/g.The used[Bmim]Br-2PG DES was regenerated and showed an extraction efficiency of 50.5%within four recycles.

Studies on the Structures and Spectra of Benzothiophene Oligomers

Theoretical studies on a series of oligobenzothiophenes were carded out with the AM 1 and DFT methods. Based on B3LYP/6-31G（D） optimized geometries, the electronic spectra, IR spectra and NMR spectra of the oligomers were calculated by INDO/CIS, AM1 and B3LYP/6-31G（D） methods, respectively. The energy gaps decrease, and the absorption in elec- tronic spectra exhibits a red-shift as polymerization increases. The IR frequencies are little affected by the polymerization and substituents. The ^13C chemical shifts are changed to be upfield since the electron-donating groups increase the electron density of carbon atoms but remain unchanged with the increase of polymerization.

Theoretical study on the mechanism of sulfur migration to gas in the pyrolysis of benzothiophene

The release and control of sulfur species in the pyrolysis of fossil fuels and solid wastes have attracted attention worldwide.Particularly,thiophene derivatives are important intermediates for the sulfur gas release from organic sulfur,but the underlying migration mechanisms remain unclear.Herein,the mechanism of sulfur migration during the release of sulfur-containing radicals in benzothiophene pyrolysis was explored through quantum chemistry modeling.The C_(1)-to-C_(2)H-transfer has the lowest energy barrier of 269.9 kJ·mol-1 and the highest rate constant at low temperatures,while the elevated temperature is beneficial for C−S bond homolysis.2-Ethynylbenzenethiol is the key intermediate for the formation of S and SH radicals with the overall energy barriers of 408.0 and 498.7 kJ·mol-1 in favorable pathways.The generation of CS radicals is relatively difficult because of the high energy barrier(551.8 kJ·mol-1).However,it can be significantly promoted by high temperatures,where the rate constant exceeds that for S radical generation above 930°C.Consequently,the strong competitiveness of S and SH radicals results in abundant H2 S during benzothiophene pyrolysis,and the high temperature is more beneficial for CS2 generation from CS radicals.This study lays a foundation for elucidating sulfur migration mechanisms and furthering the development of pyrolysis techniques.

Facile syntheses of 3-trifluoromethylthio substituted thioflavones and benzothiophenes via the radical cyclization

3-CF3 S substituted thioflavones and benzothiophenes were achieved via the reactions of AgSCF3 with methylthiolated alkynones and alkynylthioanisoles,respectively,promoted by persulfate.This protocol possesses good functional group tolerance and high yields.Mechanistic studies suggested that a classic two-step radical process was involved,which includes addition of CF3 S radical to triple bond and cyclization with SMe moiety.

Effect of textural property of coconut shell-based activated carbon on desorption activation energy of benzothiophene

In this work,the effect of the textural property of activated carbons on desorption activation energy and adsorption capacity for benzothiophene(BT)was investigated.BET surface areas and the textural parameters of three kinds of the activated carbons,namely SY-6,SY-13 and SY-19,were measured with an ASAP 2010 instrument.The desorption activation energies of BT on the activated carbons were determined by temperature-programmed desorption(TPD).Static adsorption experiments were carried out to determine the isotherms of BT on the activated carbons.The influence of the textural property of the activated carbons on desorption activation energy and the adsorption capacity for BT was discussed.Results showed that the BET surface areas of the activated carbons,SY-6,SY-13 and SY-19 were 1106,1070 and 689 m2·g^(-1),respectively,and their average pore diameters were 1.96,2.58 and 2.16 nm,respectively.The TPD results indicated that the desorption activation energy of BT on the activated carbons,SY-6,SY-19 and SY-13 were 58.84,53.02 and 42.57 KJ/mol,respectively.The isotherms showed that the amount of BT adsorbed on the activated carbons followed the order of SY-6>SY-19>SY-13.The smaller the average pore diameter of the activated carbon,the stronger its adsorption for BT and the higher the activation energy required for BT desorption on its surface.The Freundlich adsorption isotherm model can be properly used to formulate the adsorption behavior of BT on the activated carbons.

Ultra-deep oxidative desulfurization of fuel with H_2O_2 catalyzed by phosphomolybdic acid supported on silica

A highly active catalyst of phosphomolybdic acid ~HPMo） was prepared and applied in the catalytic oxidative desulfurization （CODS） system. The catalyst was characterized by FT-IR, XRD, XPS and superconducting NMR. The influences of rn（catalyst）/m（oil）, V（H202）fV（oil）, reaction temperature and reaction time on the fractional conversion of benzothiophene （BT） and dibenzothiophene （DBT） were investigated. GC-MS and micra-coulometric methods were employed to investigate the reaction. The catalyst has high desulfurization activity in the removal of BT and DBT under mild conditions. The recycling experiments indicated that DBT and BT removal could still reach 95.2% and 95.7% after 10 cycles.

The Triazole and Thiophene Containing New Heterocyclic Systems

The aim of the current work is to create new heterocyclic tetracyclic condensed systems which combine benzothiofen and benzimidazoleinto one molecule. The haisic products are 1,2-, 2,3- and 3,4- diamines of dibenzothiophenes. Orto-diamines react with hydrochloric acid and sodium nitrite and obtain three new isomeric heterocyclic systems： 3H-benzothieno[3,2-e]benzotriazole, 3H-benzothieno[2,3-f]benzotriazole and 1H-benzothieno[3,2-g]benzotriazole with the anticipated biological activity. Their spectral characteristics are studied.

Novel Photochromic Compounds Responding to InGaN Diode Laser;Synthesis and Photochromic Behavior of Dibenzothiophenylcycloalkenes

1, 2 - bis(3-Methylbenzo[b]thiophen-2-yl)cycloalkene derivatives 3a, 3b and 1 - (2-methylbenzo[b]thiophen - 3 - yl) - 2 - (3 - methylbenzo[b]thiophen - 2 - yl)cyclohexene 9 were synthesized. The obtained compounds exhibited photochromic property and the absorption bands of the colored forms 4a, 4b and 10 centered between 360-440 nm thus possessing the sensitivity at the wavelength of the newly developed InGaN diode laser.

Comparative Study on Oxidative Desulfurization of FCC Gasoline by Ce^(4+) Compound and H_2O_2

This article describes two kinds of model oil samples made of a benzothiophene/octane mixture and a 2-me- thylthiophene/octane mixture. Furthermore, this paper investigates the oxidative desulfurization selectivity and reaction efficiency when Ce4+ compound and H2O2 having identical electron equivalent weight were used as oxidants. The test re- sults showed that the two kinds of oxidants were more effective to remove benzothiophene in the model oil samples. For oxidative desulfurization of 2-methylthiophene, Ce4+ compound was obviously superior than H2O2. This paper by means of quantum chemistry analyses elaborates the complex formed between Ce4+ species and 2-methylthiophene and FT-IR spec- trograms of model oil samples before and after oxidation by Ce4+ compound and H2O2, respectively. The results demonstrat- ed that Ce4+ compound could remove sulfur compounds not only through oxidation reaction but also through complexation reaction.

Selectivity adsorption of thiophene alkylated derivatives over modified Cu^+-13X zeolite

Solid adsorbents Cu＋- 13X and Cu＋-13X loaded with La element were prepared by ion-exchange method. X-ray diffraction （XRD） and scanning electron microscope （SEM） were used to characterize the structure of the prepared zeolite. Adsorption of thiophene with differ- ent groups over the two adsorbents was investigated by static adsorption equilibrium and kinetic test. Static equilibrium data were correlated based on the Langmuir model and the modified Langmuir model. Kinetic data were fitted very well by Crank diffusion model. The results re- vealed that the adsorption capacity of single component over the Cu＋-13X loaded with La element increased about 10% as compared to the non-doped Cu＋-13X. Fitting results of ηi and De illustrated that loading of the La element into zeolite could change the interaction force be- tween binary components. The kinetic test showed that the competitive adsorption became moderate, and thus resulted in the improvement of the total desulfiarization capacity. Keywords： rare earths; static adsorption; kinetic adsorption; thiophene; 3-methylthiophene; 2,5-dimethvlthiophene; benzothiophene

Three-Component Synthesis of 2-Heteroaryl-3-hydroxybenzo[b]- thiophenes under Transition-Metal-Free Conditions

A convenient synthetic route to 2-heteroaryl-3-hydroxybenzo[b]thiophene derivatives via K_(2)CO_(3)-promoted multicomponent cycliza-tion between o-halogenated benzaldehyde,2-methylquinolines and sulfur powder has been demonstrated.This reaction is performed smoothly under simple conditions to give the corresponding products in moderate to good yields.The resultant 3-hydroxybenzo[b]thiophenes have been proved to be versatile building blocks in a range of transition-metal-catalyzed cross-coupling reactions.