Thiophenic Sulfur Compounds Research Articles

Adsorption of Thiophene Out of Model Gasoline Using Metal Ion-Exchanged Zeolite

Adsorptions of organic sulfur compounds thiophene was carried out using metal ion-exchanged Y-zeolites. Na-Yzeolites exchanged with Ag+, La3+, Cu2+, Ni2+, Bi3+ions were prepared by liquid ion exchange method. Ag+and La3+ions modified Yzeolites showed markedly high adsorptive capacities for Thiophene. The sulfur uptake increased in the order of Bi-Yzeolite < Ni-Yzeolite < CuY-zeolite < AgY-zeolite < LaY-zeolite for thiophene. The mole ratios of TP/Ag and TP/La were 0.098 and 0.071, respectively.

Molecular Characterization of Sulfur Compounds in Venezuela Crude Oil and Its SARA Fractions by Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Venezuela crude oil was separated into saturates, aromatics, resins, and asphaltenes (SARA) fractions. The sulfur compounds in the crude oil and its SARA fractions were reacted with iodomethane in the presence of silver tetrafluoroborate and converted to methylsulfonium salts. The methylsulfonium salts were characterized by positive-ion electrospray ionization (ESI) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The S1, S2, S3, O1S1, O1S2, O2S1, and N1S1 class species were identified in crude oil derived methylsulfonium salts. The molecular composition and mass distribution of sulfur compounds in the subfractions were distinctly different. Small amounts of S1 class species (cyclic-ring sulfides) were present in the saturates fraction. Thiophenic sulfur compounds were dominant in the aromatics fraction. Complex multiheteroatoms (N1Sy, OxSy, and N1OxSy class species) were present in the resins and asphaltenes fractions. The relative abundance plots of double-bond equivalence (DBE) versus the carbon number of S1, S2, O1S1, and O2S1 class species showed that as the molecular polarity of the fraction increased, the DBE values of the abundant Sy class species increased. SARA fractionation isolates the highly aromatic sulfur species in the resins and asphaltenes fractions, which are not observed in the parent crude oil sample.

Preparation of MCM-41 supported phosphoric acid catalyst for thiophenic compounds alkylation in FCC gasoline

Abstract The alkylation of thiophenic sulfur compounds with olefins in FCC gasoline followed by distillation of heavy compounds is a good alternative to classical desulfurization technologies. In this study, the preparation condition of MCM-41 supported phosphoric acid catalyst was optimized and the activity tests in real gasoline proved that the optimal catalyst was promising to be applied in the alkylation transfer process of thiophenic sulfurs compared to the HY zeolite previously studied. Moreover, characterization results obtained by XRD and NH3-TPD revealed that the factors affecting on catalytic activity such as surface acid properties and crystallinity were greatly influenced by preparation conditions.

The Interpretation of Sulfur K-Edge XANES Spectra: A Case Study on Thiophenic and Aliphatic Sulfur Compounds

Sulfur K-edge XANES has been measured for three sulfur model compounds, dibenzothiophene, dibenzothiophene sulfone, and aliphatic sulfur (DL-methionine). The spectra have been simulated with Density Functional Theory (DFT) by using a number of methods, including the half-core-hole approximation. Dipole transition elements were calculated and the transitions were convoluted with linearly increasing Gaussian functions in the first 20 eV of the near-edge region. In the case of dibenzothiophene, relaxation of the first excited states in the presence of the core-hole gave a further improvement. The theoretical results reproduce well the features of the spectra and give insight in the relation between geometric structure and molecular orbitals. Though DL-methionine and dibenzothiophene show a similar sharp rise of the white line, their molecular levels are quite different, pointing out the difficulties in finding useful "fingerprints" in the spectra for specific compounds.

Biodesulfurization of dibenzothiophene by Shewanella putrefaciens NCIMB 8768

Clean fuel research, including into improvement of the processes of desulfurization and dearomatization, has become an important focus of environmental catalysis studies worldwide. Sulfur contained in diesel fuel is an environmental concern because the sulfur is converted to SOx during combustion, which not only contributes to acid rain, but also poisons the catalytic converters now widely installed for exhaust emission treatment. The problem of sulfur removal has become more apparent due to the high sulfur contents in crude oils and the low limit of sulfur content in finished fuel products specified by regulatory authorities. The Environmental Protection Agency of the United States (EPA) had set a target to reduce the sulfur content of diesel fuel from 500 ppm to 15 ppm for the year 2006 and 10 ppm will become the maximum content for sulfur by 2008 (Yang et al., 2005). Thiols, sulphides and thiophenes are readily removed by hydrodesulfurization (HDS), but up to 70% of the sulfur in petroleum is found as DBT and substituted (methylated) DBTs, which are particularly recalcitrant to HDS treatment compared with mercaptans and sulfides (Yang et al., 2005; Le Borgne et al., 2003). Microbiological methods to desulfurize hydrocarbon streams offer a potentially attractive alternative to traditional chemical engineering methods. Biological processes require relatively mild conditions (low pressures and low temperatures), which could be a major advantage of biodesulfurization. Therefore most studies on biodesulfurization (BDS) have focused on the removal of thiophenic sulfur compounds, of which DBT is widely accepted to be representative. DBT is indeed considered to be particularly relevant as a model compound for the forms of thiophenic sulfur found in fossil fuels, such as crude oils, coals or bitumen of particular geographic origins, and the various refining intermediates and fuel products manufactured therefrom (Olson, 1998). Various bacteria are able to metabolize DBT. In the 1970s, Kodama showed that microorganisms could attack DBT without removing sulfur (Scheme 1). This microbial transformation of DBT by the Kodama pathway involves cleavage of one of DBT’s aromatic rings so it has not been commercially developed because it did not remove the sulfur atom from the heterocyclic compound, and moreover led to a decrease in the fuel’s calorific value through the oxidation of benzene ring. Biodesulfurization of dibenzothiophene by Shewanella putrefaciens NCIMB 8768 F. Ansari,* P. Prayuenyong and I. Tothill 1 Microsystems & Nanotechnology Centre, Department of Materials, Cranfield University, Bedfordshire MK43 0AL, UK 2 Institute of Bioscience & Technology, Cranfield University, Cranfield Beds MK43 0AL, UK 3 Cranfield Health, Cranfield University, Bedfordshire MK43 0AL, UK

Heats of Adsorption from Liquid Solutions and from Pure Vapor Phase: Adsorption of Thiophenic Compounds on NaY and 13X Zeolites

A study of adsorption of thiophenic sulfur compounds, thiophene (T), benzothiopnene (BT), and dibenzothiophene (DBT), in normal alkane solvents (n-octane and hexadecane) on NaY and 13X zeolites was performed. Adsorption isotherms of pure-component n-octane, hexadecane, and T from the vapor phase were also measured. Analysis of the heats of adsorption (including differential and integral heats) calculated by using the Clausius−Clapeyron equation were in agreement with the results obtained by Ng et al. using flow calorimetry for the same systems. The simple theory estimating the relationship between the heat of adsorption from liquid solution and that from the vapor phase proposed in our previous work was tested using the experimental data. The enthalpies of solvation for T−octane and T−hexadecane were also used to validate the simple theory. The theoretical predictions were in close agreement with experiments. The simple theory is easy to use and can explain and provide insight into adsorption from liquid ...

Selective Adsorption of Sulfur Compounds: Isotherms, Heats, and Relationship between Adsorption from Vapor and Liquid Solution

Adsorption isotherms were measured for thiophenic sulfur compounds, thiophene (T), benzothiophene (BT), 2-methylbenzothiophene (2-MBT), and dibenzothiophene (DBT), from their binary solutions in n-octane. Two sulfur-selective, π-complexation sorbents were studied: Cu(I)-Y zeolite and PdCl2 impregnated on activated carbon (PdCl2/AC). Vapor-phase isotherms of n-octane and thiophene were also measured. The selectivity of adsorption from liquid solutions followed the order, T < BT < 2-MBT < DBT for PdCl2/AC, and T < DBT < 2-MBT < BT for Cu(I)-Y zeolite. The adsorption bond energies, which approximate the heats of vapor-phase adsorption, followed the order, T < BT < 2-MBT < DBT. This order was not followed for adsorption from liquid solutions on Cu-Y zeolite. The heats of adsorption were obtained by the temperature dependence of the isotherms. A simple theory was proposed for estimating the relationship between the heat of adsorption from liquid solution and that from vapor phase. The experimental results wer...

Liquid-Phase Adsorption of Multi-Ring Thiophenic Sulfur Compounds on Carbon Materials with Different Surface Properties

This work examines the effects of structural and surface properties of carbon materials on the adsorption of benzothiophene (BT), dibenzothiophene (DBT), 4-methyldibenzothiophene (4-MDBT) and 4,6-dimethyl-dibenzothiophene (4,6-DMDBT) in the presence of 10 wt % of aromatics in liquid alkanes that simulate sulfur compounds in diesel fuels. The equilibrium-adsorption capacity varies significantly, from 1.7 to 7.0 mg-S/g-A. The results show that different carbon materials have significantly different sulfur-adsorption capacities and selectivities that depend not only on textural structure but also on surface functional groups. The adsorption of multi-ring sulfur compounds on carbon materials was found to obey the Langmuir isotherm. On the basis of adsorption tests and the characterization of carbon materials by BET and XPS, the oxygen-containing functional groups on the surface appear to play an important role in increasing sulfur-adsorption capacity. The adsorption-selectivity trend of the carbon materials for various compounds increases in the order of BT < naphthalene < 2-methylnaphthalene < DBT < 4-MDBT < 4,6-DMDBT, regardless of carbon material types. This selectivity trend for sulfur compounds is dramatically different and almost opposite from that previously observed for adsorption over nickel-based adsorbents. The regeneration of spent activated carbons was also conducted by solvent washing. The high-adsorption capacity and selectivity for methyl DBTs indicate that certain activated carbons are promising adsorbents for selective adsorption for removing sulfur (SARS) as a new approach to ultra deep desulfurization of diesel fuels.

Oxidative desulfurization of synthetic diesel using supported catalysts: Part I. Study of the operation conditions with a vanadium oxide based catalyst

In this work, an experimental study was carried out to obtain the reactivity of different organic sulfur compounds and to examine the effect of various parameters, such as temperature, solvent and the amount of oxidant reagent in oxidative desulfurization (ODS) reaction. The oxidation was performed through a vanadium based catalyst in the presence of hydrogen peroxide under mild reaction conditions, atmospheric pressure and temperature range of 303–343 K. The sulfur compounds studied were: 2-methylthiophene (2-MT), 2,5-dimethylthiophene (2,5-DMT), benzothiophene (BT), dibenzothiophene (DBT), 4-methyldibenzothiophene (4-MDBT) and 4,6-dimethyl dibenzothiophene (4,6-DMDBT). All of them are typical thiophenic sulfur compounds present in diesel fuels. A synthetic diesel was prepared with these compounds in hexadecane. The experimental results showed that oxidation reactivities decreased according to the following order: DBT > BT > 4-MDBT > 2-MT > 2,5-DMT > 4,6-DMDBT. A fraction of the S compounds removed from the diesel phase, was not transformed to its corresponding sulfone, under these experimental conditions. It is only removed as sulfur compound by extraction, without ODS reaction. The surplus amount of oxidant promoted the equilibrium reaction, but the thermal decomposition of oxidant and oxidation reactions produces water, which inhibits the ODS reactions. Therefore, the controlled addition of H 2O 2 improves ODS reactivity of sulfur compounds.

Flow calorimetric and thermal gravimetric study of adsorption of thiophenic sulfur compounds on NaY zeolite

A study of adsorption of thiophenic sulfur compounds (thiophene, benzothiophene, dibenzothiophene and 4,6-dimethyl benzothiophene) in normal alkane solvents (octane, dodecane and hexadecane) on NaY zeolite has been performed by using flow calorimetry technique and thermogravimetric analysis. The measured heat of adsorption of sulfur compounds includes the heat from the displacement of the adsorbed solvent molecules by sulfur compounds and it is therefore much lower than that obtained by gas phase adsorption of sulfur compounds in the zeolite. The apparent heat of adsorption of sulfur compounds per gram of sorbent decreases when the solvent changes from octane, dodecane to hexadecane, but the heat of adsorption per mole of sulfur compound calculated based on the sorption data does not vary significantly with the solvent used. The measured heat of adsorption per gram of sorbent is also influenced by the molecular size of the sulfur compound and decreases in the order: thiophene > benzothiophene > dibenzothiophene due to the higher sorbent capacity for the smaller sulfur compound. Thermogravimetric analysis of the adsorbed sulfur compounds under combustion condition used for the sulfur elimination from the sorbent indicates that the combustion of the refractory sulfur compounds occurs at higher temperatures. Analysis of the effluent from the calorimeter could be used to estimate the breakthrough characteristics of the sorbent. This indicates that the flow calorimetry is a promising technique for establishing the relationship between sorption capacity and heat of adsorption of sulfur compounds. The information obtained from the flow calorimetry and thermogravimetry could be used for the development of selective sorbents for the production of ultra-clean fuels.

A study of the adsorption of thiophenic sulfur compounds using flow calorimetry

Selective adsorption of sulfur compounds from gasoline and diesel fuel has potential to produce ultra clean fuels for on-board fuel cell applications and also to meet the upcoming legislation for clean fuels. Removal of thiophenic sulfur compounds in a hexadecane solution using commercial zeolites, NaY, USY, HY and 13X, has been investigated by adsorption and flow calorimetry techniques. The S compounds chosen were thiophene (T), benzothiophene (BT), dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). The adsorption studies were carried out in the liquid phase at 55°C. Among the zeolites studied, NaY has the highest saturation sorption capacity for the sulfur compounds. The overall heat of adsorption of sulfur compounds in a hexadecane solution was measured at 30°C using a flow microcalorimeter. A linear correlation between the heat of adsorption and the amount of S adsorbed was found for NaY. Competitive adsorption using a mixture of anthracene, DBT and quinoline indicates that NaY selectively adsorbs quinoline while anthracene and DBT have similar affinity to NaY. Liquid flow calorimetry combined with the analysis of the effluent from the calorimeter is a promising technique to aid the development of selective sorbents for S removal and other sorption processes since it provides information on the relative heats of adsorption, the sorption capacity and the breakthrough curves.

Prediction of gas chromatographic retention times and indices of sulfur compounds in light cycle oil

Ninety sulfur compounds consisting of mercaptans, sulfides and thiophenes, were identified in a fluid-catalytic-cracking light cycle oil using gas chromatography with atomic emission detection. Their retention times and indices were correlated with molecular descriptors generated from their molecular structures. The best seven- and eight-parameter multi-linear regression models showed good predictive ability. The descriptors involved in the models reflect the geometrical, topological, and electronic properties of the molecules, related to the interactions between the solute and the stationary phase. For the 34 thiophenic sulfur compounds (benzothiophenes and dibenzothiophenes) of most interest in petroleum processing, another two five-parameter multi-linear models were developed for retention times and indices with standard errors s = 0.61 and 1.63, respectively. Such models for retention times and/or indices can be used for identification of unknown chromatographic peaks by matching their retention times or indices with those of sulfur compounds of known molecular structure when the corresponding chemical standards are unavailable.

Oxidation reactivities of dibenzothiophenes in polyoxometalate/H 2O 2 and formic acid/H 2O 2 systems

Dibenzothiophene, 4-methyldibenzothiophene, and 4,6-dimethyldibenzothiophene are typical thiophenic sulfur compounds that exist in diesel fuels. Using toluene solutions of the model compounds, experiments were carried out to compare the reactivity of the different dibenzothiophenes in oxidation reactions, a key step for oxidative desulfurizations. A series of polyoxometalate/H 2O 2 systems were evaluated for dibenzothiophene oxidation. The H 2O 2 solutions of phosphotungstic acid and its salt were very active catalyst systems for the model compound oxidation, while their molybdenum counterpart systems were much less active. The H 2O 2 solutions of silicotungstic and silicomolybdic compounds were the least active catalyst systems for the reaction. Oxidation reactivities decreased in the order of dibenzothiophene>4-methyldibenzothiophene>4,6-dimethyldibenzothiophene, the same reactivity trend that exists in HDS. However, the oxidation of the dibenzothiophenes was achieved under mild reaction conditions and it was easy to increase reaction temperature or reaction time to achieve high oxidation conversions, even for the least reactive 4,6-dimethyldibenzothiophene. Apparent activation energies of dibenzothiophene, 4-methyldibenzothiophene, and 4,6-dimethyldibenzothiophene oxidation were 53.8, 56.0, and 58.7 kJ/mol, respectively. These activation energies indicated a decrease in reactivity of dibenzothiophenes as methyl substitutes increased at the 4 and 6 positions on dibenzothiophene rings. Interestingly, in a formic acid/H 2O 2 system, the oxidation reactivity of the dibenzothiophenes showed the reverse trend, suggesting that steric hindrance might play a role when bulky polyoxoperoxo species, which likely form in a hydrogen peroxide solution, act as catalysts.

Sulfur specificity in the bench-scale biological desulfurization of crude oil byRhodococcus IGTS8

Biological removal of organic sulfur from petroleum feedstocks may offer an attractive alternative to conventional thermochemical treatment due to the mild operating conditions and greater reaction specificity afforded by the nature of biocatalysis. Previous investigations have either reported the desulfurization of model sulfur compounds in organic solvents or gross desulfurization of crude oil without data on which sulfur species were being removed. This study reports initial sulfur speciation data for thiophenic sulfur compounds present in crude oil which may be used as a guide both as to which species are treated by the biocatalyst investigated as well as to where biocatalyst development is needed to improve the extent of biological desulfurization when applied to whole crudes. Biodesulfurization of two different crude oils in the 22–31 ° API specific gravity range with total sulfur contents between 1 and 2% is demonstrated in 1-dm3 batch stirred reactors using wild type Rhodococcus sp IGTS8. While analysis of the crudes before and after biodesulfurization did not reveal a decrease in total sulfur, GC–MS did reveal significant (43–99%) desulfurization of dibenzothiophenes (DBT) and substituted DBTs. Fractionation of the whole crude, followed by analysis using gas chromatography–sulfur chemiluminescence detection (GC–SCD) of the aromatic fraction of the Van Texas crude oil, demonstrated a reduction of sulfur in this fraction from 3.8% to 3.2%. This research indicates that IGTS8 may be capable of biodesulfurization of refined products such as gasoline and diesel whose predominant sulfur species are dibenzothiophenes. Further biocatalyst development would be needed for effective treatment of the spectrum of sulfur-bearing compounds present in whole crudes.

Microbial desulfurization of a crude oil middle-distillate fraction: analysis of the extent of sulfur removal and the effect of removal on remaining sulfur.

Rhodococcus sp. strain ECRD-1 was evaluated for its ability to desulfurize a 232 to 343 degrees C middle-distillate (diesel range) fraction of Oregon basin (OB) crude oil. OB oil was provided as the sole source of sulfur in batch cultures, and the extent of desulfurization and the chemical fate of the residual sulfur in the oil after treatment were determined. Gas chromatography (GC), flame ionization detection, and GC sulfur chemiluminesce detection analysis were used to qualitatively evaluate the effect of Rhodococcus sp. strain ECRD-1 treatment on the hydrocarbon and sulfur content of the oil, respectively. Total sulfur was determined by combustion of samples and measurement of released sulfur dioxide by infrared absorption. Up to 30% of the total sulfur in the middle distillate cut was removed, and compounds across the entire boiling range of the oil were affected. Sulfur K-edge X-ray absorption-edge spectroscopy was used to examine the chemical state of the sulfur remaining in the treated OB oil. Approximately equal amounts of thiophenic and sulfidic sulfur compounds were removed by ECRD-1 treatment, and over 50% of the sulfur remaining after treatment was in an oxidized form. The presence of partially oxidized sulfur compounds indicates that these compounds were en route to desulfurization. Overall, more than two-thirds of the sulfur had been removed or oxidized by the microbial treatment.

5536387 Silver removal: Hill Michael R H; Neville Mark; Turner Andrew D, United Kingdom assigned to United Kingdom Atomic Energy Authority

Ninety sulfur compounds consisting of mercaptans, sulfides and thiophenes, were identified in a fluid-catalytic-cracking light cycle oil using gas chromatography with atomic emission detection. Their retention times and indices were correlated with molecular descriptors generated from their molecular structures. The best seven- and eight-parameter multi-linear regression models showed good predictive ability. The descriptors involved in the models reflect the geometrical, topological, and electronic properties of the molecules, related to the interactions between the solute and the stationary phase. For the 34 thiophenic sulfur compounds (benzothiophenes and dibenzothiophenes) of most interest in petroleum processing, another two five-parameter multi-linear models were developed for retention times and indices with standard errors s = 0.61 and 1.63, respectively. Such models for retention times and/or indices can be used for identification of unknown chromatographic peaks by matching their retention times or indices with those of sulfur compounds of known molecular structure when the corresponding chemical standards are unavailable.

Mass Spectrometic Investigation of Petroleum(IX). Mass Spectrometic Analysis of Aromatic Hydrocarbons and Sulfur Compounds

The mass spectrometric analysis was devised to analyse quantitatively aromatic hydrocarbons and thiophenic sulfur compounds separated from the aromatic fraction in high boiling range of petroleum. Thiphenic sulfur compounds in sample were oxidized to sulfons by hydrogen peroxide treatment and the oxidation mixture was separated sulfon fraction and hydrocarbon fraction by liquid chromatography. Aromatics in hydrocarbon fraction were analyzed by the mass spectrometry low voltage ionization method. Sulfon fraction was reduced to thiophenic sulfur compounds by ithium aluminum hydride treatment, and the thiophenic sulfur compounds were analyzed by the mass spectrometry of low voltage ionization method

Mass Spectrometric Investigation of Petroleum(V)

The mass spectrometric investigation was undertaken to analyse qualitatively aromatic hydrocarbons and thiophenic sulfur compounds separated from the aromatic fraction in high boilingrange of petroleum. The identification of the compound types was made by the characteristics of cleavage mechanism of aromatic hydrocarbons and thlophenic sulfur compounds under electron bombardment and the results of low voltage ionization method. By this method, alkylbenzene, alkyl monocyclobenzene, alkylnaphthalene, alkylphenanthrene, alkylbenzothiophene, alkyl 2, 3-dihyd obenzothiophene, alkyl dibenzothiophene and alkyl tetrahydrodibenzothiophene were determined.