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.

Preparation of highly dispersed desulfurization catalysts and their catalytic performance in hydrodesulfurization of dibenzothiophene

Micro-mesoporous ZK-1 molecular sieves with different Si/Al ratios were used as supports for binary Co-Mo hydrodesulfurization（HDS） catalysts.The CoMo/ZK-1 catalysts were prepared using an over-loading impregnation method,and characterized using N2 physisorption,X-ray diffraction,temperature-programmed NH3 desorption,temperature-programmed reduction（TPR）,ultraviolet-visible diffuse reflectance spectroscopy,and high-resolution transmission electron microscopy（HRTEM）.The results show that the CoMo/ZK-1 catalysts have high surface areas（～700 m^2/g）,large pore volumes,and hierarchical porous structures,which promote the dispersion of Co and Mo oxide phases on the ZK-1 supports.The TPR results show that the interactions between the Co and Mo oxide phases and the ZK-1 support are weaker than those in the CoMo/γ-Al2O3 catalyst.The HRTEM results show that the CoMo/ZK-1 catalysts have better MoS2 dispersion and more active edge sites.The catalysts were tested in HDS of dibenzothiophene.Under mild reaction conditions,the activity of Co and Mo sulfides supported on ZK-1 was higher than those of Co and Mo sulfides supported on ZSM-5,A1KIT-1,and γ-Al2O3.

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, ■ and π,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.

Solvothermal Synthesis of V_2O_3 Catalysts for Oxidative Desulfurization of Dibenzothiophene

V2O3 nanoparticles with high surface area have been successfully prepared by a new solvothermal method without using any surfactant and template. The size of V2O3 nanoparticles is mostly equal to 10 nm-30 nm. The highest surface area of obtained V2O3 nanoparticles reaches 49 m2/g. Several kinds of V2O3 catalysts were prepared by different methods. All these V2O3 catalysts obtained thereby showed high catalytic activity for oxidative desulfurization(ODS) reaction by using tert-butyl hydroperoxide as the oxidant. The V2O3 catalyst with a highest ODS activity was obtained under the following conditions: The catalyst was prepared upon using V2O5 as the vanadium source, methanol as the solvent, and oxalic acid as the complexing reagent at a V2O5/oxalic acid molar ratio of 1:2. The process for ODS of dibenzothiophene was carried out under mild conditions(under atmospheric pressure and at a relatively low temperature). The highest ODS activity of the obtained V2O3 nanoparticles can be attributed to their highest surface area.

Isolation of Soil Bacteria Species for Degrading Dibenzothiophene

Five bacterial strains, which are able to grow and to disintegratedibenzothiophene (DBT) and diben- zothiophene sulfone (DBTO_2) infossil fuels, are isolated. Analysis of products of DBT metabolizedby these strains shows that different bacteria strains oxidized DBTby different pathways. The isolated strains R-6, $-16, $-9 and R-8can metabolize DBT to DBTO_2 and 3-hydroxybiphenyl (HBP), which areidentified as Bacillus brevis, Bacillus Sphaericus, Nocardiagloberula and Pseudomonas delafieldii respectively.

Thermodynamic Properties for Polybrominated Dibenzothiophenes by Density Functional Theory

The thermodynamic properties of 135 polybrominated dibenzothiophenes （PBDTs） in the gaseous state at 298.15 K and 1.013×10^5 Pa, are calculated using the density functional theory （the B3LYP/6-311G^＊＊） with Gaussian 03. Based on these data, the isodesmic reacflons are designed to calculate the standard enthalpy of formation （△fH^θ） and the standard Gibbs energy of formation （△fG^θ） of PBDTs. The relations of these thermodynamic parameters with the number and positionof bromine subsfituents （NPBS） are discussed, and it is found that there exist good correlations between othermody namic parameters （including heat capacity at constant volume, entropy, enthaipy, free energy, △fH^θ, △fG^θ） and NPBS. Thoe relative stability order of PBDT congeners is proposed theoretically based on the relative magnitude of their △fG^θ. In addition, the values of molar heat capacities at constant pressure （Cp,m） for PBDT c ongelaers are calculated.

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.

Al-modified mesocellular silica foam as a superior catalyst support for dibenzothiophene hydrodesulfurization

A series of Al‐containing mesostructured cellular silica foams(Al‐MCFs)with different Si/Al molar ratios(x;x=10,20,30,40,or50)were prepared by a post synthetic method using aluminum isopropoxide as an alumina source.The corresponding NiMo catalysts supported on Al‐MCFs were prepared and evaluated using dibenzothiophene(DBT)as the probe reactant.All the synthesized samples were characterized by small‐angle X‐ray scattering,scanning electron microscopy,nitrogen adsorption‐desorption,UV‐Vis diffuse reflectance spectroscopy,H2temperature‐programmed reduction,27Al MAS NMR,temperature‐programmed desorption of ammonia,pyridine‐FTIR,Raman spectroscopy,HRTEM,and X‐ray photoelectron spectroscopy to analyze their physicochemical properties and to gain a deeper insight of the interrelationship between the structures and the catalytic performance.The synthesis mechanism was proposed to involve the formation of Br?nsted acid and Lewis acid sites through the replacement of Si4+with Al3+.Aluminum introduced into MCFs by the post synthetic method has a negligible influence on the mesostructure of the parent MCFs but can form silicoaluminate materials with moderate Br?nsted acidity.For Al‐MCFs(x)materials,the detection of tetrahedrally coordinated Al3+cations demonstrated that the Al species had been successfully incorporated into the silicon frameworks.Furthermore,the DBT hydrodesulfurization(HDS)catalytic activity of the NiMo/Al‐MCFs(x)catalysts increased with increasing Si/Al molar ratio,and reached a maximum at a Si/Al molar ratio of20.The interaction of Ni and Mo species with the support became stronger when Al was incorporated into the MCFs supports.The high activities of the NiMo/Al‐MCFs catalysts for the DBT HDS were attributed to the suitable acidity properties and good dispersions of the Ni and Mo active phases.

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.

Oxidative desulfurization of dibenzothiophene over Fe promoted Co–Mo/Al_2O_3 and Ni–Mo/Al_2O_3 catalysts using hydrogen peroxide and formic acid as oxidants

This work reports the enhancing effect of a highly cost effective and efficient metal, Fe, incorporation to Co or Ni based Mo/Al2O3 catalysts in the oxidative desulfurization （ODS） of dibenzothiophene （DBT） using H2O2 and formic acid as oxidants. The influence of operating parameters i.e. reaction time, catalyst dose, reaction temperature and oxidant amount on oxidation process was investigated. Results revealed that 99% DBT conversion was achieved at 60℃ and 150 min reaction time over Fe-Ni-Mo/Al2O3. Fe tremendously enhanced the ODS activity of Co or Ni based Mo/Al2O3 catalysts following the activity order：Fe-Ni-Mo/Al2O3 〉 Fe-Co-Mo/Al2O3 〉 Ni-Mo/Al2O3 〉 Co-Mo/Al2O3, while H2O2 exhibited higher oxidation activity than formic acid over all catalyst systems. Insight about the surface morphology and textural properties of fresh and spent catalysts were achieved using scanning electron microscopy （SEM）, X-ray diffraction （XRD）, energy dispersive X-ray （EDX） analysis, Atomic Absorption Spectroscopy （AAS） and BET surface area analysis, which helped in the interpretation of experimental data. The present study can be deemed as an effective approach on industrial level for ODS of fuel oils crediting to its high efficiency, low process/catalyst cost, safety and mild operating condition.

Preparation of highly active MCM-41 supported Ni_2P catalysts and its dibenzothiophene HDS performance

Highly active MCM-41 supported nickel phosphide catalysts for hydrodesulfurization （HDS） were synthesized by two different phosphorus sources, in which the surface of Ni2P catalysts were modified by air instead of being passivated by O2/N2 mixture. In addition, the catalysts need not be activated with flowing H2 （30 ml·min^-1） at 500℃ for 2 h prior to reaction as traditional method. X-ray diffraction （XRD）, X-ray photoelectro spectroscopy （XPS）, N2-adsorption specific surface area measurements and CO chemisorption were used to characterize the resulting catalysts. The effect of modification with air on the surface of the catalysts for HDS performance was investigated. Results showed that the surface modification with air can promote the formation of smaller Ni2P particles and more active Ni sites on surface of catalysts. At 3.0 MPa and 613 K, the dibenzothiophene （DBT） conversion of the catalysts modified with air was 98.7%, which was 7.1% higher than that of catalyst passivated by O2/N2 mixture. The higher activities of Ni2P（x）/M41-O catalysts can be attributed to the smaller Ni2P particles sizes and the increased hydrogen dissociation activity due to the surface modification.

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.