Optimization of dendritic TS-1/Silica micro–mesoporous composites for efficient hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene

A novel composite material(TD)composed of TS-1 microcrystalline and dendritic mesoporous silica nanospheres(DMSNs)was successfully prepared.The TD composite material had open pore structure and large specific surface area,which was conducive to the mass transfer of reactants and products.The Ti element in TS-1 could be used as an electron assistant,and the spillover d-electrons were conducive to the improvement of the sulfidation and dispersion of MoS_(2),thereby forming more type II MoS_(2) active phases.The incorporation of Ti could bring more Brønsted(B)and Lewis(L)acid,which was conducive to the hydrogenation pathway(HYD)selectivity(41.2%)of dibenzothiophene(DBT)hydrodesulfurization(HDS)and isomerization(ISO)route selectivity(21.9%)of 4,6-dimethyldibenzothiophene(4,6-DMDBT)HDS,thus improve the HDS activity of DBT and 4,6-DMDBT.NiMo/TD-70(Aging temperature=70℃)had the best HDS activities of DBT(99.0%)and 4,6-DMDBT(93.7%)due to its large open pore structure,good acidity,suitable metal-support interaction(MSI)and perfect dispersion of the metallic active sites.

Two-photon Absorption and Optical Power Limiting Properties of Two Novel Dibenzothiophene-based Chromophores

Two novel V-shaped symmetric chromophores： E-2,8-bis（4-vinyl-4-carbazol-9-yl）diben- zothiophene （abbreviated as SK-G1） and E-2,8-bis（4-vinyl-4-triphenylamino） dibenzothiophene （abbreviated as ST-G1） have been synthesized and characterized. Their two photon absorption properties were measured by the open-aperture femtosecond Z-scan technique and the nanosecond nonlinear optical transmission （NLT）, respectively, when pumped by Ti： sapphire laser at 750 nm and 800 nm.

Quantitative Structure-chromatographic Retention Relationship for Polychlorinated Dibenzothiophenes and Their Corresponding Sulfones

Polychlorinated dibenzothiophenes(PCDTs)and their corresponding sulfone(PCDTO2)compounds are a group of important persistent organic pollutants.In the present study,geometrical optimization and subsequent calculations of electrostatic potentials(ESPs)on molecular surface have been performed for all 135 PCDTs and 135 PCDTO2 congeners at the HF/6-31G*level of theory.A number of statistically-based parameters have been extracted.Linear relationship between gas-chromatographic retention index(RI)and the structural descriptors have been established by multiple linear regression.The result shows that two descriptors derived from positive electrostatic potential on molecular surface,σ+^2 andπ,together with the molecular volume(Vmc)and the energy of the lowest unoccupied molecular orbital(ELUMO)can be well used to express the quantitative structure-retention relationship(QSRR)of PCDTs and PCDTO2.Predictive capability of the two models has been demonstrated by leave-one-out cross-validation with the cross-validated correlation coefficient(RCV)of 0.996 and 0.997,respectively.Furthermore,the predictive power of the models is further examined for the external test set.Correlation coefficients(R)between the observed and predicted RI values for the external test set are 0.997 and0.998,respectively,validating the robustness and good prediction of our model.The QSRR model established may provide again a powerful method for predicting chromatographic properties of aromatic organosulfur compounds.

Oil maturity assessment using maturity indicators based on methylated dibenzothiophenes

Aromatic fractions of 140 oils and condensates that originated from different types of source rocks （marine shale,terrestrial shale and marine carbonate） were analyzed using gas chromatographymass spectrometry （GC-MS） to investigate the relative distributions of methylated dibenzothiophenes with respect to thermal maturity.The positions of methyl groups of trimethyldibenzothiophene isomers （TMDBTs） including those used in the definition of maturity indicator TMDBT index in previous studies were firmly identified by co-elution of internal standards in GC-MS analysis and by comparing with reported retention indices.A new maturity ratio related to dimethyldibenzothiophenes （DMDBTs） is proposed on the basis of the differences in thermodynamic stability among different DMDBT isomers.Another maturity index （TMDBT-I2） based on TMDBTs is also suggested on the basis of our empirical observations and presumed thermodynamic stability of TMDBT isomers.These two newly proposed （2,6 ＋ 3,6）-/1,4-DMDBT ratio and TMDBT-I2 correlate well with MDR （4-/1-methyldibenzothiophene）and 2,4-/1,4-DMDBT ratios,suggesting their common chemical reaction mechanisms and similar behavior with increasing maturity.Therefore,they can be effectively applied for maturity assessments.Furthermore,the TMDBTs related maturity parameters are more reliable for over-mature oils and condensates due to the relatively higher concentrations of thermodynamically unstable TMDBT isomers,i.e.1,4,6-,1,4,8-and 3,4,6-TMDBT in this study than those of 1-methyldibenzothiophene （1-MDBT） or 1,4-DMDBT.In contrast with 4,6-/1,4-DMDBT,the newly proposed （2,6 ＋ 3,6）-/1,4-DMDBT ratios for oils that originated from different types of source rocks have approximately same relationship with the oil maturity （Rc %）.This suggests that the lithology and organic facies may have relatively less influence on （2,6 ＋ 3,6）-/1,4-DMDBT ratio compared to 4,6-/1,4-DMDBT.The maturity parameters based on methylated dibenzothiophenes are particularly useful in the maturity assessments of post-and over-mature oils and condensates and can complement maturity indicators based on steranes and terpanes.

Photocatalytic Oxidative Desulfurization of Dibenzothiophene on TiO2 Modified Bimodal Mesoporous Silica

By using the bimodal mesoporous silica(BMMS) as the carrier and butyl titanate as the titanium source, the TiO_2/BMMS catalyst was prepared. The samples were characterized by XRD, XRF, N_2 adsorption and desorption, FTIR, UVvis,SEM, EDS, and TEM techniques. The test results showed that TiO_2 was amorphous, the TiO_2/BMMS catalyst had an ordered bimodal mesoporous structure, and the chemical interaction existed between BMMS and TiO_2. Since the TiO_2/BMMS had a lower band gap, its photocatalytic activity was better than TiO_2. Under UV irradiation a one-pot PODS system was set up, using TiO_2/BMMS as the catalyst, H_2O_2 as the oxidant, and methanol as the solvent. The TiO_2/BMMS catalyst showed better photocatalytic activity than the mono-modal mesoporous TiO_2/SBA-15 catalyst, and the desulfurization rate of dibenzothiophene(DBT) over TiO_2/BMMS catalyst could reach 99._2%. The TiO_2/BMMS catalyst also had so good stability that the desulfurization rate of DBT did not drop apparently after 8 cycles of reusing, and could still be close to 90%.

Effects of nicotinamide and riboflavin on the biodesulfurization activity of dibenzothiophene by Rhodococcus erythropolis USTB-03

Rhodococcus erythropolis USTB-03 is a promising bacterial strain for the biodesulfurization of dibenzothiophene （DBT） via a sulfurspecific pathway in which DBT is converted to 2-hydroxybiphenyl （2HBP） as an end product. The effects of nicotinamide and riboflavin on the sulfur specific activity （SA） of DBT biodesulfurization by R. erythropolis USTB-03 were investigated. Both nicotinamide and riboflavin were found to enhance the expression of SA, which was not previously reported. When R. erythropolis USTB-03 was grown on a medium containing nicotinamide of 10.0 mmol or riboflavin of 50.0 μmol, SA was raised from 68.0 or so to more than 130 mmol 2HBP/（kg dry cells.h）. When R. erythropolis USTB-03 was grown in the presence of both nicotinamide of 5.0 mmol and riboflavin of 25.0 μmol, SA was further increased to 159.0 mmol 2HBP/（kg dry cells.h）. It is suggested that the biological synthesis of reduced form of flavin mononucleotide （FMNH2）, an essential coenzyme for the activities of biodesulfurization enzyme Dsz C and A, might be enhanced by nicotinamide and riboflavin, which was responsible for the increased SA of R. erythropolis USTB-03.

Desulfurization of dibenzothiophene by a newly isolated Corynebacterium sp. ZD-1 in aqueous phase

Sulfur emission through fuel combustion is a global problem because it is a major cause of acid rain. Crud oil contains many heterocyclic organic sulfur compounds, among which dibenzothiophene(DBT) and DBTs bearing alkyl substitutions usually are representative compounds. A strain was isolated from refinery sludge and identified as Corynebacterium ZD-1. The behavior of DBT degradation by ZD-1 in aqueous phase was investigated. Corynebacterium ZD-1 could metabolize DBT to 2-hydroxybiphenyl(2-HBP) as the dead-end metabolite through a sulfur-specific pathway. In shake flask culture, ZD-1 had its maximal desulfurization activity in the late exponential growth phase and the specific production rate of 2-HBP was about 0.14(mmol·kg dry cell -1·min -1, mmol·KDC -1·min -1). Active resting cells for desulfurization should be prepared only in this period. 2-HBP inhibited the growth of strain ZD-1, the production of DBT degradation enzymes, and the activity of enzymes. Sulfate inhibited the production of dibenzothiophene(DBT) degradation enzymes but had no effect on the enzymes' activity. The production rates of 2-HBP at lower cell densities were higher and the maximum amount conversion of DBT to 2-HBP(0.067 mmol/L) after 8 h was gained at 9.2 g dry cell/L rather higher cell density. The results indicated that this newly isolated strain could be a promising biocatalyst for DBT desulfurization.

Optimization for Microbial Degradation of Dibenzothiophene by Pseudomonas sp. LKY-5 Using Response Surface Methodology

In this research, the degradation of dibenzothiophene(DBT) was investigated by using Pseudomonas sp. LKY-5 isolated from oil contaminated soil. The response surface methodology(RSM) based on the Box-Behnken design(BBD) was applied for evaluating the interactive effects of four independent variables including substrate concentration, temperature, pH and agitation rate on the DBT removal response. A total of 29 experiments for four factors at three levels were conducted in present study. A second-order regression model was then developed, and the analysis of variance(ANOVA) illustrated that the proposed quadratic model could be utilized to navigate the design space. The value of determination coefficient(R2=0.953 4) indicated a satisfactory agreement between the quadratic model and the experimental data. It was found that DBT removal was more significantly affected(P<0.000 1) by substrate concentration compared with other three parameters. An 100% degradation of DBT could be obtained by Pseudomonas sp. LKY-5 at a substrate concentration of 100 mg/L.

Amorphous TiO_2-supported Keggin-type ionic liquid catalyst catalytic oxidation of dibenzothiophene in diesel

Supported ionic liquid(IL) catalysts [Cmim]PMoO/Am TiO(amorphous TiO) were synthesized through a one-step method for extraction coupled catalytic oxidative desulfurization(ECODS) system. Characterizations such as FTIR, DRS,wide-angle XRD, Nadsorption–desorption and XPS were applied to analyze the morphology and Keggin structure of the catalysts. In ECODS with hydrogen peroxide as the oxidant, it was found that ILs with longer alkyl chains in the cationic moiety had a better effect on the removal of dibenzothiophene. The desulfurization could reach 100% under optimal conditions, and GC–MS analysis was employed to detect the oxidized product after the reaction. Factors affecting the desulfurization efficiencies were discussed, and a possible mechanism was proposed. In addition, cyclic experiments were also conducted to investigate the recyclability of the supported catalyst. The catalytic activity of [Cmim]PMoO/Am TiOonly dropped from 100% to 92.9% after ten cycles, demonstrating the good recycling performance of the catalyst and its potential industrial application.

Study of Dibenzothiophene Adsorption Over Carbon Nanotube Supported CoMo HDS Catalysts

Adsorption properties of dibenzothiophene (DBT) on a CNT (carbon nanotube) support as well as on CoMoS/CNT and CoMoO/CNT catalysts have been studied. Consecutive desorption of adsorbates was measured by TGA. The commonly used carriers AC (activated carbon), γ-Al_2O_3, and their supported catalysts (CoMoO/AC, CoMoS/AC, CoMoO/γ-Al_2O_3, CoMoS/γ-Al_2O_3)were also subjected to analysis for comparison. The acidic properties of the samples were characterized using the NH_3-TPD technique. Correlation between the adsorption of DBT and the acidic properties of the catalysts has been established. It was found that the Co-Mo catalysts in the sulfide state adsorbed much more DBT molecules than the corresponding Co-Mo catalysts in the oxide state. The CoMoS/CNT catalyst exhibited very high HDS activity and selectivity, as compared with the CoMoS/γ-Al)_2O_3 catalysts. Based on the BET data and the high hydrogenolysis/hydrogenation selectivity of the CoMoS/CNT, it was deduced that more than 90% of the DBT molecules adsorbed on the CoMoS/CNT with an end-on mode, and the surface of the CoMoS/CNT catalyst was almost fully covered with DBT molecules. Although the AC support had very high surface area and high loading ability, the AC supported CoMoS catalyst showed lower HDS activity, as compared with the CoMoS/γ-Al_2O_3 catalyst.

Oxidation of Dibenzothiophene in Model Diesel Using Hydroperoxide Generated via In-Situ Reaction of Octane with Oxygen

The potential of carrying out oxidative desulfurization(ODS) using oxygen as an oxidant was explored in this work. n-Octane firstly reacted with oxygen to produce hydroperoxides in-situ, which were then used as oxidants to oxidize the dibenzothiophene(DBT) in the absence of catalysts. The hydroperoxides generated in-situ were effective in oxidizing DBT to its corresponding dibenzothiophene sulfone(DBTO_2) which was characterized by FT-IR and ~1H-NMR. The removal rate of DBT could reached 98.4% under conditions covering a temperaure of 140℃, a rection duration of 4 h, and an oxygen partial pressure of 0.4 MPa. The influences of different hydrocarbon components in diesel on DBT removal were investigated. The results showed that cyclohexane and n-dodecane had no effect on the removal of DBT, but xylene had a slight negative effect on DBT removal. A possible oxidation mechanism was proposed and the concentration of hydroperoxides in both O_2-oxidized octane and model diesel were detected.

N-butyl-pyridinium tetrafluoroborate as a highly efficient ionic liquid for removal of dibenzothiophene from organic solutions

In this research,1-butyl-pyridinium tetrafluoroborate([C4Py][BF4]-)was prepared by ion exchange method and was characterized by1H-NM R,13C-NM R,and FT-IR techniques.The synthesized ionic liquid w as used for removal of dibenzothiophene as a typical organosulfur pollutant from organic medium.The effect of different parameters on the extraction efficiency w as studied and optimized.At the optimized conditions,97.68%of dibenzothiophene w as extracted from 1 000 mg/L n-hexane solution.The extraction efficiency obtained in this w ork w as higher than the previous reported values.The desulfurization reaction w as kinetically follow ed the second order mechanism.The ionic liquid w as reusable and after four regeneration cycles 97%of its original extraction efficiency w as retained.

End-capped Thiophene Modulated Molecular Packing in 2,8-Dibenzothiophene-based Materials:from Face-to-face to Edge-to-face Stacking

Two new organic crystals of 2,8-bisthienyldibenzothiophene（BTDT） and 2,8-bis-dithienyldibenzothiophene（BDTDT） compounds were successfully obtained.The change of end-capped group from thiophene to dithiophene causes big differences in molecular packing and carrier-transport property.The adjacent molecules of compound BTDT adopt face-to-face π stacking and exhibit two-dimensional interchain interactions.On the contrary,BDTDT molecules are arranged in an edge-to-face motif and show mainly one-dimensional interacting character.The packing mode exerts dramatic effect on the carrier-transport property.The crystal of BTDT belongs to the orthorhombic system,space group P21212 with a = 20.1427（11）,b = 4.6016（3）,c = 8.6340（5） ,V = 800.27（8） 3,Z = 2,Dc = 1.446 g/cm3,F（000） = 360,S = 1.019,the final R = 0.0491 and wR = 0.0960 for 1605 reflections with I 2σ（I）.The crystal of BDTDT belongs to the orthorhombic system,space group P212121 with a = 7.2636（15）,b = 25.359（5）,c = 25.359 ？,V = 4670.9（14） ？3,Z = 8,Dc = 1.458 g/cm3,F（000） = 2112,S = 0.880,the final R = 0.0597 and wR = 0.1318 for 8047 reflections with I 2σ（I）.

Novel Diazole/Triazole and Dibenzothiophene Dioxide Containing Pentacyclic Systems with Promising Biological Activities

The aim of the current work is to synthesize the new heterocyclic pentacyclic condensed systems that combine benzothiophen and benzimidazole/triazole into one molecule. The dibenzothiophene was taken as an initial compound and by consistent “extension” was annihilated the imidazole and triazole nucleuses. As a result two new pentacyclic systems were produced: 3H-, 7H-diimidazole[4,5-b][5,4-g] dibenzothiophene-5,5-dioxide and 3H-, 7H-ditriazole[4,5-b][5,4-g] dibenzothiophene-5,5-dioxide with the promising antimi-crobial activity. Their spectral characteristics were studied.

Synthesis and self-association of dibenzothiophene derivatives for simulation of hydrogen bonding interaction in asphaltenes

The dibenzothiophene derivatives, namely 2-（dibenzothiophene-2-carbonyl）benzoic acid and 2-（diben- zothiophene-2-carbonyl）alkyl benzoate, were synthesized and characterized by nuclear magnetic resonance （1H NMR）, matrix-assisted laser desorption/ionization time of flight mass spectrometry, and elemental analysis. The self- association behavior of these dibenzothiophene derivatives in CH2C12 and CH3CN was investigated using UV-visible absorption spectroscopy, fourier transform infrared spec- troscopy, and atomic force microscopy. It was found that the carboxylic acid exhibited a strong self-association trend in CH2C12 solution at a concentration of about 5 × 10^-7 M. Hydrogen bonding of carboxyl in the dibenzoth- iophene derivatives was confirmed to be the main driving force for the formation of the carboxylic acid aggregates.

Theoretical Study of Dibenzothiophene Based Electron Transport Materials

Density functional methods have been used for the calculation of electronic structures, electronic transitions, vertical electron affinities and intermolecular reorganization energies for tri-aryl substituted dibenzothiophenes. These model compounds were then compared to the predicted values for dibenzo[b,d]thiophen-2-yltriphenylsilane (DBTSI 2) and to dibenzo[b,d]thiophene-2,8-diylbis(diphenylphosphine oxide) (PO15), known electron transport molecules. The results indicate that these model compounds can be used in a blue OLED system.

Kinetic Modelling of the Influence of H₂S on Dibenzothiophene Hydrodesulfurization in a Batch System over Nano-MoS₂

In this work, the possibility of enhanced activity during the hydrodesulfurization of dibenzothiophene over certain nano-MoS2 catalyst due to the presence of H2S was examined by focusing on the reaction kinetics. With H2S generated in situ, the overall reaction followed the autocatalytic rate law;while in the absence of H2S the kinetics indicated a pseudo-first-order reaction. H2S appears to modify the relative contributions of parallel hydrogenation and desulfurization reactions by drastically increasing the hydrogenation rate. Kinetic models were developed that describe the hydrodesulfurization reaction at various H2S concentrations, and the kinetic parameters and adsorption equilibrium constants associated with this process were estimated by fitting the experimental data. The results suggest that the promotion and/or inhibition of hydrodesulfurization by H2S likely result from the same overall reaction mechanism.

Few-layered hexagonal boron nitride nanosheets stabilized Pt NPs for oxidation promoted adsorptive desulfurization of fuel oil

A few-layered hexagonal boron nitride nanosheets stabilized platinum nanoparticles(Pt/h-BNNS)is engineered for oxidation-promoted adsorptive desulfurization(OPADS)of fuel oil.It was found that the few-layered structure and the defective sites of h-BNNS not only are beneficial to the stabilization of Pt NPs but also favor the adsorption of aromatic sulfides.By employing Pt/h-BNNS with a Pt loading amount of 1.19 wt%as the active adsorbent and air as an oxidant,a 98.0%sulfur removal over dibenzothiophene(DBT)is achieved along with a total conversion of the DBT to the corresponding sulfones(DBTO_(2)).Detailed experiments show that the excellent desulfurization activity originates from the few-layered structure of h-BNNS and the high catalytic activity of Pt NPs.In addition,the OPADS system with Pt/h-BNNS as the active adsorbent shows remarkable stability in desulfurization performance with the existence of different interferents such as olefin,and aromatic hydrocarbons.Besides,the Pt/h-BNNS can be recycled 12 times without a significant decrease in desulfurization performance.Also,a process flow diagram is proposed for deep desulfurization of fuel oil and recovery of high value-added products,which would promote the industrial application of such OPADS strategy.

Total alkyl dibenzothiophenes content tracing the filling pathway of condensate reservoir in the Fushan Depression,South China Sea

The condensates are generally characterized by high maturity,low concentration of steranes and ter-panes biomarkers and low content of non-hydrocarbon fraction. In this case commonly used steranes,terpanes and carbazoles parameters cannot be effectively applied in the reservoir-filling tracing. The hydrogen bond formed by sulfur atom in the dibenzothiophenes (DBTs) results in molecule adsorption and fractionation during oil migration in reservoir. Like carbazoles,total DBTs content decreases with the increasing of oil migration distance. Therefore,a new parameter——total DBTs content is proposed to be used to trace the oil migration orientation and filling pathway. In present study,total DBTs con-tents of condensates and light oils are obtained by adding internal standard——eight deuterium atoms substituted DBT during Gas Chromatography-Mass Spectrometry analysis of aromatic fraction. Except for a few samples with much lower content of non-hydrocarbon fraction,the total DBTs content shows a fine positive correlation with that of carbazoles. Large errors can be caused in the process of pyrrolic nitrogen compounds separation. The application of this new parameter in the Fushan Depression of Beibu Gulf Basin,South China Sea indicates that this parameter is a reliable one to trace filling pathway in condensate reservoirs. Combined with other DBTs-related parameters,such as 4-/1-methydibenzo-thiophene and 2,4-/1,4-dimethyldibenzothiophene,oil migration orientation and filling pathway of the Fushan Depression was determined. The accumulations of Huachang oil field in the Fushan Depres-sion are mainly migrated and charged from northeast to southeast along the Huachang uplift. It can be predicated that the light oil and condensates in the Huachang oil field should be sourced from the source kitchen at the Bailian Sag. It shows that total DBTs content is an effective parameter to tracing oil migration orientation and filling pathway.

Desulfurization of dibenzothiophene(DBT) by a novel strain Lysinibacillus sphaericus DMT-7 isolated from diesel contaminated soil

A new bacterial strain DMT-7 capable of selectively desulfurizing dibenzothiophene（DBT） was isolated from diesel contaminated soil.The DMT-7 was characterized and identified as Lysinibacillus sphaericus DMT-7（NCBI GenBank Accession No.GQ496620） using 16S rDNA gene sequence analysis.The desulfurized product of DBT,2-hydroxybiphenyl（2HBP）,was identified and confirmed by high performance liquid chromatography analysis and gas chromatography-mass spectroscopy analysis respectively.The desulfurization kinetics revealed that DMT-7 started desulfurization of DBT into 2HBP after the lag phase of 24 hr,exponentially increasing the accumulation of 2HBP up to 15 days leading to approximately 60% desulfurization of the DBT.However,further growth resulted into DBT degradation.The induced culture of DMT-7 showed shorter lag phase of 6 hr and early onset of stationary phase within 10 days for desulfurization as compared to that of non-induced culture clearly indicating the inducibility of the desulfurization pathway of DMT-7.In addition,Lysinibacillus sphaericus DMT-7 also possess the ability to utilize broad range of substrates as sole source of sulfur such as benzothiophene,3,4-benzo DBT,4,6-dimethyl DBT,and 4,6-dibutyl DBT.Therefore,Lysinibacillus sphaericus DMT-7 could serve as model system for efficient biodesulfurization of diesel and petrol.