Hydrocarbon Matrix Research Articles

Aluminum halide—cobalt halide polynuclear complexes active in low-temperature conversion of alkanes: formation, molecular structures, and IR spectra

Low-temperature FT-IR studies of products of co-condensation of aluminum chloride and cobalt chloride in hydrocarbon matrices were carried out in the temperature range 80–250 K. DFT quantum mechanical calculations of the geometry and vibrational frequencies of aluminum chloride/cobalt chloride polynuclear molecular and ionic complexes of different compositon were carried out. Isomeric labile complexes Al2Cl6·CoCl2 were detected under partial matrix isolation conditions and their behavior was monitored. The interaction of the 1: 1 and 2: 1 aluminum halide/cobalt halide molecular complexes at 120–170 K produces catalytically active species in low-temperature conversion of alkanes. According to the data of in situ spectral studies and to the results of quantum chemical calculations, these species represent ionic associates which simultaneously contain Co and Al atoms in both cationic and anionic fragments.

Highly sensitive express methods for determining methanol in liquid hydrocarbons produced by OAO Gazprom

Simple and reliable methods are proposed for determining methanol in stable gas condensate, wide light hydrocarbon fractions, and liquefied hydrocarbon gases. High sensitivity of the methods (methanol detection range about 1 × 10−4 mass %) is attained by concentration of the methanol from the analysis specimens with water or aqueous salt solution in combination with flame-ionization detection. The risk of overlapping of chromatographic peaks of methanol and hydrocarbon matrix of the specimens is eliminated completely.

Removal of organically bound sulfur from oil shale by iron(III)-ion generated–regenerated from pyrite by the action of Acidithiobacillus ferrooxidans — Research on a model system

Oil shale is one of the alternative sources of hydrocarbon fuels (“synthetic petroleum”) but is characterized by increased sulfur and nitrogen contents, which represent even greater ecological problems in its use compared to classical fuels. Acidithiobacillus ferrooxidans ( At. f.) is capable of oxidizing pyrite to iron(III)-ions, providing a strong oxidation agent at low pH. We have used this oxidizing agent for the oxidation of the sulfur present in dibenzothiophene (DBT), as a substrate model to demonstrate its potential to oxidize organically bound sulfur in oil shale. An HCl-concentrate of oil shale was used as the hydrocarbon matrix. Acidithiobacillus ferrooxidans has already been shown to oxidize the pyritic sulfur component, thereby potentially providing a complete sulfur removal system. By applying GC-MS, we established that DBT transformation occurred by oxidation or elimination of sulfur. The products obtained were more soluble in water than the parent compounds, which reduced the concentration of organic sulfur.

On the composition analysis of nc-TiC/a-C : H nanocomposite coatings

Using a set of ion beam analysis (IBA) techniques the compositions of hydrogenated diamond-like carbon (DLC) nanocomposite coatings are scrutinized, including the hydrogen content. The coatings are composed of two constituents: amorphous hydrocarbon matrix (a-C : H) and nanocrystalline titanium carbide (nc-TiCa) which makes it challenging to quantify the sp3/sp2 ratio of the a-C : H matrix. Using IBA and SEM data, the partial mass densities of nc-TiCa and a-C : H matrix are obtained. The latter is analysed as a function of hydrogen content and compared with the density of pure sp3 bonding DLC and of sp2 graphite containing different contents of hydrogen. In addition, the fraction of sp3 bonding in the matrix is estimated assuming a linear dependence on the mass densities of the matrix.

Highly Conducting Patterned Pd Nanowires by Direct-Write Electron Beam Lithography

Palladium hexadecylthiolate is shown to serve as a negative-tone direct-write electron resist to produce nanopatterns down to 30 nm. The written patterns do not deviate much from the precursor in composition, while a post-treatment at 230 degrees C in air produced metallic Pd nanowires with residual carbon less than 10% and resistivity close to the bulk value, a desirable property of interconnects in nanocircuitry. The as-written patterns contain small nanocrystals (<5 nm) in a hydrocarbon matrix, which upon annealing aggregate to form well-connected networks of larger nanocrystals (5-15 nm), thus giving rise to metallic conductivity.

Synthesis and characterisation of Ti-C coatings with variable carbon content

Carbide coatings deposited by PVD techniques can provide different properties according to their structural and compositional features. In particular, MC/a-C(:H) composite coatings (where M is a carbide-forming element) receive increasing attention as wear resistant films with low coefficient of friction. In this work, Ti-C:H coatings were prepared by reactive magnetron sputtering and their atomic ratio Ti/C was varied between 0.14 and 5.3. Maximum hardness values were achieved for Ti/C ratios corresponding to the carbide formation. Nanocomposite coatings with hydrocarbon matrix were deposited after growing a functionally graded interlayer and their tribological properties were investigated both in air and in water.

Formation of rodlike structures of water between oppositely charged ions in decane and polyethylene

The Gibbs ensemble Monte Carlo method has been combined with the connectivity altering osmotic Gibbs ensemble to study water solubility and clustering in decane and polyethylene. We show that the presence of oppositely charged ion pairs that have fixed positions in the hydrocarbon matrices leads to an order of magnitude increase in the water solubility. This is important to a wide range of technical applications, since the uptake of the water leads to an increase in volume--or expansion--of the hydrocarbon phase which, in the case of polyethylene, may change the polymer properties and lead to water treeing. The increase in solubility is largest when the ions are sufficiently close so that rod-shaped clusters of water molecules form between the ions.

A Unified Approach for the Measurement of Individual or Total Volatile Organic Sulfur Compounds in Hydrocarbon Matrices by Dual-Plasma Chemiluminescence Detector and Low Thermal Mass Gas Chromatography

A novel gas chromatographic technique has been developed, offering dual-analytical capability of either speciation or rapid measurement of total volatile sulfur compounds in hydrocarbon matrices using the same hardware. The technique employs a pressurized liquid injection system for the delivery of volatile liquid hydrocarbons, low thermal mass gas chromatography, and a dual-plasma sulfur chemiluminescence detector to enable this dual capability with a high degree of sensitivity and selectivity towards sulfur-containing compounds. Using the technique described, a detection limit in the range of 20 ppb sulfur and less than 30 s analysis is attained. Response is linear over five orders of magnitude, with a high degree of repeatability.

Application of ICP-MS as a Multi-Element Detector for Sulfur and Metal Hydride Impurities in Hydrocarbon Matrices

Maturation of inductively coupled plasma-mass spectrometry (ICP-MS) in terms of size, reliability, and cost has had a significant impact on its consideration as a viable detector for gas chromatography. Its generally excellent sensitivity for those elements it can measure has been a contributing factor. A method for sulfur speciation in various hydrocarbon products is investigated, as well as sulfur and metal hydride contaminants in high purity hydrocarbon feed stocks. Detection limits for sulfur species in hydrocarbon liquids and gases are approximately 5 and 10 ppb, respectively, as sulfur. Lower detection limits on the order of 100 parts per trillion are achieved for arsine. The use of collision cell technology (CCT) is exploited to remove interferences. CCT has been described elsewhere (1) using helium or helium-hydrogen mixtures for suppression of (16)O(16)O(+) interference with (32)S. In this work, a novel approach is investigated which uses oxygen to remove this interference by shifting it in a comprehensive fashion. The advantage of operating the system at full power with a tandem gas and liquid interface is also discussed.

Capillary Flow Technology with Multi-Dimensional Gas Chromatography for Trace Analysis of Oxygenated Compounds in Complex Hydrocarbon Matrices

By employing multi-dimension gas chromatography with capillary flow technology in combination with highly selective capillary columns and a pressurized liquid injection system, light oxygenated compounds such as methanol, ethanol, n-propanol, 2-propanol, and n-butanol in the presence of either light hydrocarbon, heavy hydrocarbon, or aromatic matrices can be measured accurately with minimal possibility of a false positive. Using this technique, a detection limit of at least 0.20 ppm (w/w) with a linear correlation coefficient greater than 0.9993 over a range from 0.5 ppm to 600 ppm (w/w) and a relative standard deviation of greater than 2.7% are achieved for the solutes tested. The technique can also be effective for the measurement of other classes of oxygenated compounds such as ethers, aldehydes, and ketones. Another added benefit for the implementation of capillary flow technology is the capability to conduct column back-flushing, where heavier, undesired solutes in a sample can be back-flushed from the chromatographic system to improve system cleanliness and sample throughput.

Determining the mass density of a hydrocarbon matrix in thin-film nanocomposites by ion-beam techniques

An approach based on ion-beam analysis, including Rutherford backscattering, nuclear backscattering, and elastic recoil detection, for determining the partial mass density of a hydrocarbon matrix in nanocomposites is proposed and applied to the nc-TiC/a-C:H thin-film coating material.

A General Study of Asphaltene Flocculation Prediction at Field Conditions

Summary A large set of field data have been collected during the last decade related to various facets of asphaltene instability problems at our production facilities. These problems include compatibility of heavy oil with hydrocarbon diluents in a Venezuelan operation, commingling of live oil and condensate in a North Sea production facility, compatibility of drilling mud-base oil, and miscible injectants with reservoir fluids in Alaskan operations. In each of the field cases, significant lab data were generated by titrating the neat dead crude oil, and oil-solvent blends with n-alkanes. The solvents used to study the asphaltene issue were toluene, condensate, and base oil. We have applied available asphaltene prediction techniques (Heithaus 1960, 1962; Wiehe and Kennedy 2000ab; Wiehe et al. 2001; Andersen 1999; Wang and Buckley 2001; Wang et al. 2003, 2004; Leontaritis 1998) to explain the field data. None of the models has been found comprehensive enough to explain flocculation at all the conditions, including the flocculation that occurs at ambient conditions in the presence of paraffinic diluents; stability enhancement that occurs upon addition of aromatic solvents; and the instability that occurs in a live fluid because of changes in composition, pressure, and temperature. To handle a complex crude oil system, these models made some simplifying assumptions that enabled them to make the problem manageable. In doing so, they lose some predictive capability. We found there are two forces that need to be accurately captured— dynamics of the alteration of solubility parameter of the hydrocarbon matrix, and change in entropy of mixing—to model the asphaltene behavior. The latter has been either empirically estimated by extrapolating the ambient titration data or neglected in many of the previous models. The basic parameters for our model can be calculated from lab data generated by titrating the dead crude oil, or oil solvent blends with n-alkanes, at different temperatures. So far, this model has been applied to various field conditions in production facilities and has been found successful in matching the field data.

Determination of Tetrachloroethylene and Other Volatile Halogenated Organic Compounds in Oil Wastes by Headspace SPME GC–MS

Oil wastes and slops are complex mixtures of hydrocarbons, which may contain a variety of contaminants including tetrachloroethylene (perchloroethylene, PCE) and other volatile halogenated organic compounds (VHOCs). The analytical determination of PCE at trace levels in petroleum-derived matrices is difficult to carry out in the presence of large amounts of hydrocarbon matrix components. In the following study, we demonstrate that headspace solid-phase microextraction (HS-SPME) combined with GC–MS analysis can be applied for the rapid measurement of PCE concentration in oil samples. The HS-SPME method was developed using liquid paraffin as matrix matching reference material for external and internal calibration and optimisation of experimental parameters. The limit of quantitation was 0.05 mg kg−1, and linearity was established up to 25 mg kg−1. The HS-SPME method was extended to several VHOCs, including trichloroethylene (TCE) in different matrices and was applied to the quantitative analysis of PCE and TCE in real samples.

Removal of Organically Bound Sulfur From Oil Shale by Iron(III)-Ion Generated-Regenerated from Pyrite by the Action of &lt;i&gt;Acidithiobacillus ferrooxidans&lt;/i&gt;

Oil shales are one of the alternative sources of hydrocarbon fuels (“synthetic petroleum”), characterized by the increased sulfur and nitrogen content which represent even greater ecological problem in use, compared to classical fuels. Acidithiobacillus ferrooxidans is capable of oxidizing pyrite to iron (III)-ion, providing a strong oxidation agent at low pH. We have used this oxidizing agent for oxidation of sulfur present in DBT as a substrate model to demonstrate its potential to oxidize organically bound sulfur in oil shales. An HCl-concentrate was used as the hydrocarbon matrix. Acidithiobacillus ferrooxidans is already recognized to oxidize the pyritic sulfur component, thereby potentially providing a complete sulfur removal system. By applying GC-MS we established that DBT transformation occurred by oxidation or elimination of sulfur. The products obtained are more soluble in water than parent compounds and this reduces concentration of organic sulfur.

IDENTIFICATION AND QUANTIFICATION OF PAH IN BITUMEN BY GC- ION-TRAP MS AND HPLC-FLUORESCENT DETECTORS

Bitumen is a complex product with a large matrix of heavy aliphatic/naphthenic/aromatic hydrocarbons as well as a large number of isomeric compounds such as polycyclic aromatic compounds (PACs). Some PACs and derivatives are known to have a mutagenic and carcinogenic activity, and there is no generally satisfactory clean-up method for separating PACs from this very complex hydrocarbon matrix. Moreover, from an analytical point of view, the isomeric compounds usually co-elute in the same gas chromatography (GC) retention range, GC being one of the most widely used techniques in this area. However, the use of a suitable clean-up procedure for isolating the aromatic fractions, combined with two selective detection techniques such as mass spectrometry (GC-Ion Trap MS) and HPLC-Fluorescent detector (HPLC-FL), is expected to provide an effective tool for accurately determining certain PAC species in bitumen. In this paper we compare two quantitative extractions to analyse the 16 PAHs that occur in bitumen according to the US EPA reference list. Two clean-up protocols are assessed and compared by using both GC-Ion Trap MS and HPLC-FL chromatographic/detection techniques. The first extraction method combines well-established and proven clean-up operations with an automatic fractionation by semi-preparative HPLC (certification test program for PAHs in sewage sludge, in creosote-contaminated soil and in harbour sediment organised by the Community Bureau of Reference, BCR). The second method uses a multiple step-by-step liquid/liquid and liquid/solid extraction clean-up procedure. After the bitumen extracts are cleaned up, only the use of both GC-MS & HPLC-FL can provide reliable results. The more sensitive FL provides enhanced fluorescent selectivity signals that facilitate identification of PAH compounds. However, for their quantification, the capillary GC-ion trap mass spectrometric technique is preferred because of the insufficient resolution of the HPLC column and the possible quenching or co-elution effect of matrix compounds. Both detection techniques are regarded as complementary.

Unsaturated trinuclear osmium carbonyls: comparison with their iron analogues

Comparison of theoretical and experimental structural parameters as well as nu(CO) frequencies for Os(3)(CO)(12) suggests that the density functional theory (DFT) method MPW1PW91 with a suitable ECP basis set including relativistic effects is a reliable method for predicting structures and vibrational frequencies of third row transition metal carbonyl derivatives. Using this method the structures of the unsaturated trinuclear osmium carbonyl derivatives Os(3)(CO)(n) (n = 11, 10, 9) have been investigated for comparison with their iron carbonyl analogues. For Os(3)(CO)(11) the global minimum has micro-CO groups bridging each edge of the Os(3) triangle in contrast to its iron analogue predicted to have two micro(3)-CO groups bridging all three iron atoms. An alternative Os(3)(CO)(11) structure having only terminal CO groups, similar to that observed experimentally by Bentsen and Wrighton (J. G. Bentsen and M. S. Wrighton, J. Am. Chem. Soc., 1987, 109, 4518) in the photolysis of Os(3)(CO)(12) in low temperature hydrocarbon matrices, is predicted to lie approximately 7 kcal mol(-1) above this global minimum. The global minimum for Os(3)(CO)(10) has one face-bridging micro(3)-CO group and one edge-bridging micro-CO group. For Os(3)(CO)(9) the global minimum has an Os(3) scalene triangle with different metal-metal distances suggesting one single, one double, and one triple metal-metal bond similar to its iron analogue.

Nanostructured plasma coatings to obtain multifunctional textile surfaces

Nanostructured surfaces are of great interest, since they provide a high surface area. A high functionality can thus be obtained by ultrathin coatings. Plasma polymerization of acetylene mixed with ammonia (C 2H 2/NH 3) was used in a regime where both deposition and etching processes took place yielding a nanoporous, crosslinked network with accessible functional groups. These plasma coatings can be used as permanent hydrophilic treatment or for substrate-independent dyeing when deposited on textile fabrics. Increasing color intensity with film thickness proved that accessible amine groups were deposited within a nanoporous hydrocarbon matrix. Using plasma co-sputtering of a silver target, Ag nano particles can be in situ embedded within the growing plasma polymer yielding a well-defined size and distribution of nano particles at the coating surface. Hence, an anti-microbial activity was achieved. Multifunctional textile surfaces can thus be obtained by adjusting combined properties such as wettability, functional group density as well as anti-bacterial and bio-responsive surfaces. Scale-up of these combined plasma processes is enabled by control of plasma chemistry regarding energy input into the plasma zone and plasma physics by surface interaction with energetic particles.

Diphenylsilylene

Lamp or pulsed laser photolysis of 1,1,3,3-tetramethyl-2,2-diphenyl-1,2,3-trisilacycloheptane affords diphenylsilylene (SiPh2) with significantly higher selectivity than that reported previously from other SiPh2 precursors, allowing the direct detection of SiPh2 in solution for the first time. The UV/vis spectrum of the silylene in anhydrous hexane at 25 degrees C, determined by laser flash photolysis methods, agrees well with that obtained in frozen hydrocarbon matrixes, and that of the dimerization product, tetraphenyldisilene, is tentatively assigned. Absolute rate constants measured for the reaction of SiPh2 with a number of characteristic silylene scavengers correspond closely to those reported previously for SiMe2 with the same or similar substrates.

Probability of the reaction at the first collision with polyethylene of tritium atoms generated by thermal activation

The influence of the experimental conditions on the probability of the reaction of tritium atoms generated in the gas phase by thermal dissociation of tritium on a tungsten filament (thermal activation) with hydrocarbons in a solid target was examined. Experiments were performed with polyethylene films placed in a special case with a calibrated slit in the center of the top lid. For tritium atoms reaching the target without energy loss, the probability of the reaction at the first collision with the hydrocarbon matrix cooled to 77 K decreases from 18 to 2.5% with a decrease in the atomizer temperature from 2000 to 1660 K. For tritium atoms preliminarily thermalized in the gas phase to 77 K, the probability of the reaction at the first collision is so low that it cannot be measured with our experimental technique. Nevertheless, even at 77 K tritium atoms can react with the target, yielding the compound labeled at the C-H bonds.

Stretching the limits of static SIMS with C 60+

Pristine and Au-covered molecular films have been analyzed by ToF-SIMS (TRIFT™), using 15 keV Ga + (FEI) and 15 keV C 60 + (Ionoptika) primary ion sources. The use of C 60 + leads to an enormous yield enhancement for gold clusters, especially when the amount of gold is low (2 nmol/cm 2), i.e. a situation of relatively small nanoparticles well separated in space. It also allows us to extend significantly the traditional mass range of static SIMS. Under 15 keV C 60 + ion bombardment, a series of clusters up to a mass of about 20,000 Da (Au 100 −: 19,700 Da) is detected. This large yield increase is attributed to the hydrocarbon matrix (low-atomic mass), because the yield increase observed for thick metallic films (Ag, Au) is much lower. The additional yield enhancement factors provided by the Au metallization procedure for organic ions (MetA-SIMS) have been measured under C 60 + bombardment. They reach a factor of 2 for the molecular ion and almost an order of magnitude for Irganox fragments such as C 4H 9 +, C 15H 23O + and C 16H 23O −.