Thiophene Concentration Research Articles

Electrically conductive composites prepared from 3-methyl thiophene by the FeCl3 oxidation method

Surface conductive polyurethane films from poly(propylene glycol), toluene 2,4-diisocyanate, 3-methyl thiophene and butyltin dilaurate can be successfully prepared by the diffusion-oxidative polymerization method. Various effects of the doping conditions, such as the reaction time, the FeCl3 concentration, the weight ratio of the 3-methyl thiophene to PU and the temperature on the electrical conductivity and thickness of the conductive layer of the 3-methyl thiophene/PU composite were investigated. Decomposition temperature rises gradually from pure undoped PU to doped composite that indicates blending took place in FeCl3/ethyl acetate solution. As oxidative reaction time increases, the electrical conductivity of the 3-methyl thiophene doped PU film increases together with the thickness of the coating layer. With increasing FeCl3 concentration and weight ratio of the 3-methyl thiophene to PU, the thickness of the coating layer decreases, while the electrical conductivity increases. The increase of the thickness of the PU film leads to the rise of the electrical conductivity. The thickness of the coating layer decreases, while the electrical conductivity of the 3-MT doped PU film increases with increasing reaction temperature. As the reaction time and temperature increase, the polar components of the PU film increase resulting into the increase of moisture regain value.

Synthesis and characterization of [HRu(CO)(CH3CN)(TPPTS)3]BF4: Catalytic properties in the aqueous-biphasic hydroformylation of olefins

Abstract The new water soluble complex [HRu(CO)(CH3CN)(TPPTS)3]BF4 (TPPTS = tris[(m-sulfonated)phenyl]phosphine P(m-C6H4SO3Na)3) has been synthesized by ligand exchange techniques from the corresponding PPh3 derivative in a methoxyethanol–water mixture. The new complex was characterized by FTIR, UV–vis, and 1H NMR and 31P {1H} NMR spectroscopy and used as catalyst precursor for the aqueous biphasic hydroformylation of several olefins and their mixtures under moderate reaction conditions. The catalytic activity order found was: 1-hexene > allylbenzene > 2,3-dimethyl-1-butene > styrene > cyclohexene. The sulphur tolerance of this complex was also investigated using thiophene as a model molecule; it was found that the new complex maintains its activity when the thiophene concentration is below 500 ppm. The mercury test in independent experiments showed no interference of the Hg at all with the evolution of the reaction, demonstrating that the catalysis is performed by molecular species. The recyclable nature of the complex was demonstrated during 1-hexene hydroformylation where at the end of each catalytic reaction all the metal remains in the aqueous phase.

Evaluation of sorbents for thiophene removal from liquid hydrocarbons

Thiophene is a commonly occurring sulfur compound in liquid hydrocarbon streams produced in a petroleum refinery. The concentration of thiophene often needs to be reduced to very low levels for most applications. Selective adsorption of thiophene is investigated in n-heptane, 1-octene and xylenes and their mixtures. A variety of adsorbents were tested for their selectivity and adsorption capacity. Improvements in adsorption capacity were attempted based on analysis of the adsorption mechanism. Adsorption capacity of NaX zeolite was found to be highest among tested adsorbents. However, competitive adsorption from xylenes reduced adsorption capacity for thiophene from mixtures containing large concentration of xylenes. Langmuir model is applied to describe observed competitive adsorption. Selective adsorption of organic sulfur compound could be used as a polishing step in a purification scheme which allows sulfur removal from hydrocarbons at low temperature and without the use of expensive hydrogen.

Co-aggregation of fullerene C 60 and thiophene in the non-aromatic solvent cyclohexene

Abstract Co-aggregation of fullerene C60 and thiophene has been studied calorimetrically in cyclohexene at 25 °C. The total aggregation heat is found to depend on initial concentration of thiophene and fall between −1.9 and −5.8 kJ mol−1. The corresponding thiophene/fullerene molar ratio (“co-aggregation number”) ranges from 7 to 12. The data are rationalized by formation of heteromolecular nanoaggregates with intermolecular contacts of both fullerene–thiophene and fullerene–fullerene types. A physical model describing interaction between fullerenes and π-donors in solution is substantiated and used to explain heterogeneity of composites containing fullerenes.

Thiophene conversion in the BIMF process

Catalytic conversion of an oil distillate with the added extra amounts of thiophene over a zeolite catalyst was studied. The rate of the catalyst deactivation was found to increase with the increase in the thiophene concentration in the feed. A possible pathway of the thiophene conversion is discussed.

Thermochemical sulphate reduction and the generation of hydrogen sulphide and thiols (mercaptans) in Triassic carbonate reservoirs from the Sichuan Basin, China

Abstract The Sichuan Basin in China is a sour petroleum province. In order to assess the origin of H2S and other sulphur compounds as well as the cause of petroleum alteration, data on H2S, thiophene and thiol concentrations and gas stable isotopes (δ34S and δ13C) have been collected for predominantly gas phase petroleum samples from Jurassic, Triassic, Permian and Upper Proterozoic (Sinian) reservoirs. The highest H2S concentrations (up to 32%) are found in Lower Triassic, anhydrite-rich carbonate reservoirs in the Wolonghe Field where the temperature has reached >130 °C. δ34S values of the H2S in the Wolonghe Triassic reservoirs range from +22 to +31‰ and are close to those of Triassic evaporitic sulphate from South China. All the evidence suggests that the H2S was generated by thermochemical sulphate reduction (TSR) locally within Triassic reservoirs. In the Triassic Wolonghe Field, both methane and ethane seem to be involved in thermochemical sulphate reduction since their δ13C values become less negative as TSR proceeds. Thiol concentrations correlate positively with H2S in the Triassic Wolonghe gas field, suggesting that thiol production is associated with TSR. In contrast, elevated thiophene concentrations are only found in Jurassic reservoirs in association with liquid phase petroleum generated from sulphur-poor source rocks. This may suggest that thiophene compounds have not come from a source rock or cracked petroleum. Rather they may have been generated by reaction between localized concentrations of H2S and liquid range petroleum compounds in the reservoir. However, in the basin, thiophene concentrations decrease with increasing vitrinite reflectance suggesting that source maturity (rather than source type) may also be a major control on thiophene concentration.

Thiophene Hydrogenation to Tetrahydrothiophene over Tungsten Sulfide Catalysts

Independent reactions of thiophene reduction to tetrahydrothiophene and thiophene hydrogenolysis to form hydrogen sulfide and C4 hydrocarbons are shown to occur over supported tungsten sulfide catalysts and unsupported tungsten sulfide at an elevated temperature and a high pressure. The highest rate of tetrahydrothiophene formation over the supported catalysts is observed when alumina was used as a support, and the lowest reaction rate is found when silica gel was used as a support. Both catalysts are less active than unsupported tungsten disulfide. The rate of thiophene hydrogenation over tungsten disulfide increases with increasing thiophene concentration and hydrogen pressure and is inhibited by tetrahydrothiophene. The selectivity to tetrahydrothiophene is constant (70–90%) in the whole range up to high thiophene conversions. The high selectivity over tungsten sulfide catalysts is suggested to be due to the reaction pathway through thiophene protonation mediated with the surface SH groups and to the inhibition of hydrogenolysis.

In Situ XANES Study of Pt/Mordenite during Benzene Hydrogenation in the Presence of Thiophene

The influence of the Na+/H+ ratio on the benzene hydrogenation activity and the sulfur tolerance of Pt supported on mordenite (MOR) was studied by in situ XANES. An increase of the Pt white line was observed with increasing concentrations of thiophene up to 400 ppm, which indicates that an equilibrium exists between the thiophene concentration in the gas phase and the sulfur compounds present on the metal surface. Above a certain concentration of thiophene the Pt white line was constant, indicating a saturation of the metal surface with thiophene. The effect of sulfur poisoning on the metal surface was more effective for Pt supported on H-MOR compared to the more basic Pt/Na-MOR catalysts, which is attributed to the more pronounced decomposition of thiophene and the formation of H2S on Brønsted acid sites. During benzene hydrogenation, a decrease of the Pt white line resulting from the adsorption of benzene and other reaction intermediates on the Pt surface was observed. In the presence of sulfur, the increase of the Pt white line intensity during benzene hydrogenation suggests a higher sulfur coverage of the metal for Pt/H-MOR compared to Pt/NaH-MOR. An optimum concentration of acid sites was found with respect to the benzene hydrogenation rate and sulfur tolerance of the catalysts, which is attributed to the presence of two reaction pathways for benzene hydrogenation, i.e., one which is catalyzed by Pt and another in which acid sites close to Pt particles are the catalitycally active sites.

Parameters of PEM fuel-cells based on new membranes fabricated from Nafion ®, silicotungstic acid and thiophene

Abstract Several new cation exchange membranes of different thicknesses (15–500 μm) based on a Nafion® solution and silicotungstic acid with and without thiophene (named NASTATH and NASTA respectively) were synthesized by a simple chemical route for PEM fuel-cell applications. The optimum parameters for the preparation of the membranes have been determined: 10 ml of 5% of the Nafion® 117 solution was reduced by 50% and mixed with 10−3–10−5 MSTA to produce a NASTA membrane. If liquid thiophene (0.5% by volume) is added to the above solution, a NASTATH membrane is produced. The water uptake and ionic conductivity of NASTA and NASTATH were compared with those of Nafion® 117. The effect of membrane thickness and the concentrations of STA and thiophene used during the preparation of NASTA and NASTATH on their water uptake and ionic conductivity were determined. It was shown that the water uptake of the NASTA membrane (60%) was significantly better than that of Nafion® 117 (27%), while the water uptake of NASTATH (40%) was higher than that of Nafion® 117 (27%). The ionic conductivity of both the NASTA (10.10×10−2 Ω−1 cm−1) and the NASTATH (9.5×10−2 Ω−1cm−1) was found to be significantly higher than that of the Nafion® 117 (1.23×10−2 Ω−1 cm−1). The membrane performances were also determined by chemical stability studies. The membranes fabricated with Nafion® and silicotungstic acid with and without thiophene still exhibited good mechanical strength and stability after they had been dipped in an acid or a basic medium for at least 10 months. The voltage-current characteristics of solid polymer electrolyte fuel cells were determined for Nafion® 117, NASTA and NASTATH based membranes. The fuel cell parameters were correlated to the membrane water uptake and ionic conductivity. The current density at 0.600 V of the solid polymer electrolyte fuel cells (SPEFCs) based on NASTATH (810 mA cm−2) membranes was higher than that of SPEFCs based on Nafion® 117 (640 mA cm−2). It was shown that the better fuel cell parameters were not obtained with the modified membranes having the higher water uptake.

Electropreparation and electrochemical stability of polythiophenes in acetonitrile containing anhydrous HBF4

The electrooxidation behavior of thiophene and 3-methylthiophene on a Pt surface in an acetonitrile + tetrabutylammonium tetrafluoroborate solution were investigated. The electropolymerization of these monomers was studied in neutral, acidic, and basic media. The effects of thiophene concentration and the added acid were elucidated. The polythiophene and poly(3-methylthiophene) films formed were characterized by their cyclic voltammograms in a blank solution and dry conductivities were measured. Electrochemical properties of these polymers in the same medium were investigated in the absence and in the presence of added anhydrous acid and base. The behavior of the freshly prepared films was compared with that which lost its electroactivity as a result of electrooxidation using cyclic voltammetry, controlled potential coulometry, and FTIR spectroscopy. The mechanisms related to the formation of the polymers and their electroactivity loss were proposed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 312–322, 2000

Concomitant aerobic biodegradation of benzene and thiophene

Abstract The concomitant aerobic biodegradation of benzene and thiophene was investigated in microcosm experiments using a groundwater enrichment culture. Benzene was biodegraded within 1 d, whereas thiophene could not be biodegraded as the sole source of carbon and energy. Some interesting phenomena were observed when both benzene and thiophene were present. In most cases, removal of thiophene was observed, and the removal occurred concomitantly with the biodegradation of benzene, suggesting that benzene was used as a primary substrate in the cometabolic biodegradation of thiophene. No biodegradation of the two compounds was observed for some combinations of concentrations, suggesting that thiophene could act as an inhibitor to benzene biodegradation. However, this effect could be overcome if more benzene was added to the microcosm. Residual concentrations of benzene and thiophene were observed in some microcosms and the data indicated that the biodegradation of the two compounds stopped when a critical threshold ratio between the concentrations of thiophene and benzene was reached. This ratio varied between 10 and 20. Results from modeling the biodegradation data suggested that thiophene was cometabolized concomitantly with the biodegradation of benzene and that the biodegradation may be described by a modified model based on a traditional model with an inhibition term incorporated.

CONCOMITANT AEROBIC BIODEGRADATION OF BENZENE AND THIOPHENE

The concomitant aerobic biodegradation of benzene and thiophene was investigated in microcosm experiments using a groundwater enrichment culture. Benzene was biodegraded within 1 d, whereas thiophene could not be biodegraded as the sole source of carbon and energy. Some interesting phenomena were observed when both benzene and thiophene were present. In most cases, removal of thiophene was observed, and the removal occurred concomitantly with the biodegradation of benzene, suggesting that benzene was used as a primary substrate in the cometabolic biodegradation of thiophene. No biodegradation of the two compounds was observed for some combinations of concentrations, suggesting that thiophene could act as an inhibitor to benzene biodegradation. However, this effect could be overcome if more benzene was added to the microcosm. Residual concentrations of benzene and thiophene were observed in some microcosms and the data indicated that the biodegradation of the two compounds stopped when a critical threshold ratio between the concentrations of thiophene and benzene was reached. This ratio varied between 10 and 20. Results from modeling the biodegradation data suggested that thiophene was cometabolized concomitantly with the biodegradation of benzene and that the biodegradation may be described by a modified model based on a traditional model with an inhibition term incorporated.

Determination of Dithiocarbamate and Its Breakdown Product Ethylenethiourea in Fruits and Vegetables

Abstract Improved methods for determination in fruits and vegetables of ethylene bisdithiocarbamate (EBDC) residues as carbon disulfide by gas–liquid chromatographic headspace analysis and of othylenethio-urea (ETU) residues by liquid chromatography (LC) are described. Improvements to the EBDC procedure include increased sensitivity by use of 140 mL crimp seal samples bottles fitted with silicone seals, which are leak-proof and reduce headspace volume; use of a Porapak column, which allows use of higher column temperature for better residue separation; and inclusion of thiopheno as an internal standard for bettor quality control. The relationship between the logarithm of the response of carbon disulfide divided by the thiophene response versus concentration of carbon disulfide is expressed by the regression equation Y = 1.011 X + 0.008, with a correlation coefficient r2 = 0.993. Mean recoveries from 8 commodities spiked with mancozcb at 1 and 3 mg/kg, equivalent to 0.473 and 1.419 mg/kg carbon disulfide, are 94.2 ±10 and 98.3 ± 13%, respectively. The Improved LC procedure for ETU residue analysis requires minimal cleanup of sample extract, no derivatization prior to injection, and no specialized LC detectors for quantitation. The UV detector response at 240 nm Is linearly related to ETU concentration [Y = (3.18X – 0.778) × 1000. r2 = 0.997]. Moan ETU recovery from 5 commodities spiked at 0.2 to 5 mg/kg is 93.9 ± 6%. ETU residues of 0.02 to 0.25 μg/g were detected in macerated samples of fruits and vegetables spiked with man-cozeb at 5 μg/g and incubated at room temperature for 3 days. The improved procedures were used to analyze EBDC and ETU residues in fruits and vegetables sampled at a wholesale Sydney produce market. Approximately 30% of samples tested contained EBDC residues, whereas ETU residues in the same samples were below the detection limit of the analytical method (<0.02 mg/kg).

Far-infrared absorption spectra of thiophene in liquid solutions with carbon disulfide

The far-infrared absorption spectra of thiophene with carbon disulphide are presented for the first time at three mole fractions of thiophene. The spectral features clearly show that, for the whole range of concentrations of thiophene in CS 2 considered, there exists a marked appearance of strong-interaction-induced phenomena between the two kinds of molecules and this is more evident in the absorption characteristics of the 0.75 mole fraction spectrum of thiophene in CS 2 , since there exist only slight differences from the spectrum of pure thiophene. This result might suggest that thiophene and CS 2 probably “associate” to some degree when in a solution. The behaviour of the corresponding concentration-dependent total dipole autocorrelation functions (ACF) is discussed up to 1 ps, in terms of the interaction between solvent and solute. The absorption bands of pure thiophene are presented at two different temperatures, from where it is seen that as the temperature decreases the absorption increases and the spectrum is shifted by a small amount towards higher frequencies.

Thiophene Hydrodesulfurization by Catalytic Palladium Membrane Systems.

Catalytic palladium membrane reactor was used for hydrodesulfurization (HDS) of thiophene at a low thiophene concentration of 4mol% and a constant temperature of 650K, changing the rate of hydrogen permeation corresponding to the hydrogen concentration of 20 to 70mol% in reaction mixture. It was found that at the same hydrogen concentrations above 50mol%, the total conversion at high rates of hydrogen permeation was greater, by a factor of about 5, than that of HDS using hydrogen premixed in reaction mixture. The product distributions were the same for HDSs using permeating and premixed hydrogen, which depended on hydrogen concentration. It was proved that HDS changed the surface of palladium membrane chemically and morphologically, and that the permeation of hydrogen at high rates inhibited the sulfurization of the membrane.

Catalytic synthesis of thiophene from the gas formed in the semicoking of kukersite shale

Abstract Liquid catalyzate containing thiophene has been obtained from the gas formed in semicoking of kukersite shale by means of heterocyclization over an alumina-chromium-lanthanum lanthanum oxide catalyst. The thiophene concentration in the catalyzate is 1.5–2 times higher than in industrial byproduct coking thiophene concentrate. At the same a reduction in the hydrogen sulphide content of the semicoking gas from 9–12% to 0·5 vol.% or less has been obtained.

The influence of thiophene on the selective reduction of NO by NH 3

The selective reduction of NO by NH3 addition has been studied in a lean-burning oil-fired laboratory combustion tunnel with pyridine and thiophene added to the fuel oil. Two distinct but interrelated effects were observed. The conversion of a fixed amount of fuel nitrogen to NO in the flame increased as the thiophene concentration increased. In the postcombustion gases, there was a shift in the temperature dependence of the reduction process when the sulfur combustion products were present. The extent of the NO reduction was not significantly altered, but the optimal temperature for reduction shifted to higher values as the thiophene concentration increased.

Catalyst poisoning and fixed bed reactor dynamics

Abstract The poisoning kinetics of thiophene on Ni-kieselguhr catalysts and the deactivation behavior of nonisothermal fixed bed reactors have been studied experimentally using benzene hydrogenation as a model exothermic reaction. The time dependent axial temperature profiles in the reactors were measured and compared with values evaluated from a dispersion model, the parameters of which have been determined in separate experimentation. Poisoning kinetics were measured in a series of differential reactor experiments at atmospheric total pressure, thiophene partial pressures of 0·037-0·19 torr, hydrogen to benzene molar ratios > 8 1 and temperatures from 60–180°C. Excellent agreement was found with a power law equation for the rate of change of activity with time, first order in catalyst activity and in thiophene concentration, with an experimental activation energy of 1080 kcal/kmole. This correlation of poisoning kinetics, however, was not able to predict the propagation of the zone of activity (hot-spot) on poisoning of an integral fixed bed reactor. Initial (steady state) temperature profiles were modeled satisfactorally, but the rate of migration of the hot spot was found experimentally to be more rapid than that predicted from the correlation of poisoning kinetics. A semi-empirical two site deactivation model is shown to resolve the discrepancy.

Investigation of the influence of thiophene on the properties of an aluminoplatinate catalyst under the conditions of the dehydroisomerization of m ethylcyclopentane

1. The conversions of methylcyclopentane with additions of various amounts of thiophene-S35, as well as pure methylcyclopentane in the presence of a 1% Pt-Al2O3 catalyst, were investigated at 500°, 20 atm, volume velocity 2 h−1, and molar ratio H2:HC=5 ∶1. 2. When the thiophene concentration in the initial methylcyclopentane is varied from 0.5 to 6%, the dehydroisomerizing ability of the catalyst decreases from 32.1 to 3.4% after ten hours of work; the strongest effect of thiophene is observed within the concentration range 0.5–1.18%. The yield of benzene from methylcyclopentane containing thiophene decreases continuously during the entire experiment. The rate of regeneration of the deactivated catalyst by the pure hydrocarbon is higher, the lower the concentration of the poison in the initial mixture during poisoning. 3. As the thiophene concentration in methylcyclopentane is increased from 0.5 to 6%, the amount of sulfur deposited on the catalyst is increased from 0.022 to 0.149% by weight. Moreover, the activity of the catalyst varies linearly as a function of its sulfur content in the catalyst comprises 30–35% of the original amount deposited.

The effect of thiophene on an aluminum-molybdenum catalyst in cyclohexane dehydrogenation under hydrogen pressure

1. A study has been made of the dehydrogenation of cyclohexane, both in the pure state and containing various amounts of thiophene (1.00; 1.99; 2.21; 3.13; 5.05; 7.14 and 9.84% by weight) carried out on an industrial aluminum-molybdenum catalyst at 500°, at a hydrogen pressure of 20 atm. 2. It was shown by radiometric analysis that when the concentration of thiophene in the cyclohexane is changed ten-fold (from 1 to 9.84%) the amount of sulfur deposited on the catalyst under these conditions increases by a factor of two (from 0.0676 to 0.1321 g), the sulfur being uniformly distributed along the length of the catalyst layer. Analysis of the cyclohexane catalyzates has shown that the general laws followed by the poisoning of an aluminum- molybdenum catalyst under hydrogen pressure are similar to those found previously for Pt-Al2O3 catalysts.