Analysis Of Complex Hydrocarbon Mixtures Research Articles

On-Line Composition Analysis of Complex Hydrocarbon Streams by Time-Resolved Fourier Transform Infrared Spectroscopy and Ion-Molecule Reaction Mass Spectrometry.

On-line composition analysis of complex hydrocarbon mixtures is highly desirable to determine the composition of process streams and to study chemical reactions in heterogeneous catalysis. Here, we show how the combination of time-resolved Fourier transform infrared spectroscopy and ion–molecule-reaction mass spectrometry (IMR-MS) can be used for compositional analysis of processed plant biomass streams. The method is based on the biomass-derived model compound 2,5-dimethylfuran and its potential catalytic conversion to valuable green aromatics, for example, benzene, toluene, and xylenes (BTX) over zeolite β. Numerous conversion products can be determined and quantified simultaneously in a temporal resolution of 4 min–1 without separation of individual compounds. The realization of this method enables us to study activity, selectivity, and changes in composition under transient reaction conditions. For example, increasing isomerization of 2,5-dimethylfuran to 2,4-dimethylfuran, 2-methyl-2-cyclopenten-1-one, and 2-methyl-2-cyclopenten-1-one is observed as the catalyst is exposed to the reactant, while BTX and olefin formation is decreasing.

1H and 13C NMR Analysis of Gas Turbine Fuels As Applied to the Advanced Distillation Curve Method

The analysis of gas turbine fuels by 1H and 13C nuclear magnetic resonance (NMR) spectroscopy as applied to the composition-explicit advanced distillation curve method is reported. To demonstrate the general applicability for such fuels, eight independent fuel samples were characterized: one sample of JP-5, one sample of JP-8, and six samples of Jet-A. Distillate fractions were obtained for each fuel by use of the advanced distillation curve (ADC) method. These fractions were analyzed by 1H and 13C NMR, along with the undistilled residue (i.e., the undistilled liquid remaining in the kettle after 90 vol % had been distilled) and the neat fuel. NMR spectroscopy is useful for the analysis of complex hydrocarbon mixtures because it provides the mole fractions of various classes of hydrocarbons, such as aromatics and linear alkanes, without the need to calibrate. NMR spectroscopy also gives ready access to other average properties for the components of each fuel sample, such as the extent and type of alkane branching. For example, the abundance of branch points at the β position of aliphatic chains changes little for the various distillate fractions; however, branching on the interior of the aliphatic chains approximately doubles over the course of the distillation. For the heavier fractions of the fuel, interior branching becomes as important as branching at the β and γ positions. Such information is useful for the development of realistic fuel surrogates required for reliable thermophysical models. Finally, we compare the results obtained by NMR spectroscopy to previously reported GC–MS and GC-FID analyses of the same fuel samples.

Atmospheric Pressure Laser-Induced Acoustic Desorption Chemical Ionization Mass Spectrometry for Analysis of Saturated Hydrocarbons

We present atmospheric pressure laser-induced acoustic desorption chemical ionization (AP/LIAD-CI) with O(2) carrier/reagent gas as a powerful new approach for the analysis of saturated hydrocarbon mixtures. Nonthermal sample vaporization with subsequent chemical ionization generates abundant ion signals for straight-chain, branched, and cycloalkanes with minimal or no fragmentation. [M - H](+) is the dominant species for straight-chain and branched alkanes. For cycloalkanes, M(+•) species dominate the mass spectrum at lower capillary temperature (<100 °C) and [M - H](+) at higher temperature (>200 °C). The mass spectrum for a straight-chain alkane mixture (C(21)-C(40)) shows comparable ionization efficiency for all components. AP/LIAD-CI produces molecular weight distributions similar to those for gel permeation chromatography for polyethylene polymers, Polywax 500 and Polywax 655. Coupling of the technique to Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) for the analysis of complex hydrocarbon mixtures provides unparalleled mass resolution and accuracy to facilitate unambiguous elemental composition assignments, e.g., 1754 peaks (rms error = 175 ppb) corresponding to a paraffin series (C(12)-C(49), double-bond equivalents, DBE = 0) and higher DBE series corresponding to cycloparaffins containing one to eight rings. Isoabundance-contoured plots of DBE versus carbon number highlight steranes (DBE = 4) of carbon number C(27)-C(30) and hopanes of C(29)-C(35) (DBE = 5), with sterane-to-hopane ratio in good agreement with field ionization (FI) mass spectrometry analysis, but performed at atmospheric pressure. The overall speciation of nonpolar, aliphatic hydrocarbon base oil species offers a promising diagnostic probe to characterize crude oil and its products.

Modifying the response of a polymer-based quartz crystal microbalance hydrocarbon sensor with functionalized carbon nanotubes

This report compares the performance of polymer and carbon nanotube–polymer composite membranes on a quartz crystal microbalance (QCM) sensor for the detection of aromatic hydrocarbons (benzene, toluene, ethylbenzene, p-xylene and naphthalene) in aqueous solutions. Several different polymers (polystyrene, polystyrene-co-butadiene, polyisobutylene and polybutadiene) and types of functionalized carbon nanotubes (multi-walled and single-walled carbon nanotubes) were investigated at varying carbon nanotube (CNT) loading levels and film thicknesses. In a majority of instances, the difference in response between membranes comprising pure polymer and membranes containing 10% (w/w) carbon nanotubes were not statistically significant. However, a notable exception is the decreasing sensitivity towards p-xylene with increasing carbon nanotube content in a polybutadiene film. This variation in sensitivity can be attributed to a change in the sorption mechanism from absorption into the polymer phase to adsorption onto the carbon nanotube sidewalls. With much thicker coatings of 10% (w/w) carbon nanotube in polybutadiene, the sensitivity towards toluene was higher compared to the pure polymer. The increased toluene sensitivity may be partially attributed to an increase in the sorption capacity of a carbon nanotube polymer composite film relative to its corresponding pure polymer film. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) measurements were performed to understand the mechanism of sorption and these studies showed that the addition of functionalized CNT to the polymer increases the absorption of certain types of hydrocarbons. This study demonstrates that carbon nanotubes can be incorporated into a polymer-coated QCM sensor and that composite films may be used to modify the QCM response and selectivity during the analysis of complex hydrocarbon mixtures.

On-line analysis of complex hydrocarbon mixtures using comprehensive two-dimensional gas chromatography

This paper discusses the first setup for on-line qualitative and quantitative comprehensive two-dimensional gas chromatography (GC × GC) of complex hydrocarbon mixtures. A built-in 4-port 2-way valve allows switching between flame ionization detection (FID) and time-of-flight mass spectrometry (TOF-MS) between runs, without the need to cool down and vent the MS. Proper selection of GC carrier gas flow rates enables maximal agreement between the obtained chromatograms in both configurations. For on-line analysis of reactor effluents, a dedicated sampling system allows automatic sampling of the hot reactor effluent gases and immediate injection of the sample on the GC × GC. To determine a complete effluent composition in a single run of the GC × GC, a subzero oven starting temperature was employed. Modulation is started when the oven temperature reaches 40 °C, thus dividing the chromatogram in a conventional 1D and a comprehensive 2D part. This work illustrates the mature and robust character of GC × GC, extending its capabilities from mere laboratory use to on-line routine analysis for industrial processes in the (petro-)chemical industry.

Improved kinetic data from analysis of complex hydrocarbon mixtures by using SIMCA

A SIMCA model was developed for classification of C 10-bicycloalkanes to assist evaluation of kinetic experiments involving complex mixture of C 10-hydrocarbons. The influence of different pre-processing methods, such as square root and cubic root scaling, and transformation methods, including autocorrelation transform and spectral features, on the classification of C 10-bicycloalkanes was investigated. While the transformation of mass spectra into spectral features was found essential for modeling of spectra of C 10-bicycloalkanes, the intensities scaling was only of little importance for the quality of the SIMCA models. The best SIMCA model was successfully applied in detailed analysis of C 10-bicycloalkanes originating from decalin isomerization and contributed to identification of the decalin isomerization mechanism.

Aromatic ring-type analysis of complex hydrocarbon mixtures by high-performance liquid chromatography with photodiode-array detection and curve resolution

For the resolution of overlapping peaks of high-boiling mineral oil distillates, Meister's method of curve resolution was applied to spectro-chromatograms recorded by means of a high-performance liquid chromatograph coupled to a photodiode-array detector. The algorithm is based on maximizing the dissimilarity between the spectra of the components. The method is universally applicable without a prior knowledge of the spectra and presupposes no limitations concerning the number of components and the shape of their elution profiles. The resolved spectra allow the spectral identification of the aromatic ring types. In addition, the corresponding elution profiles of the compound types can be evaluated, which permits, in principle, quantification of the aromatic ring types.

Supercritical Fluid Chromatography and Supercritical Fluid Chromatography/Mass Spectrometry for Analysis of Complex Hydrocarbon Mixtures

Supercritical fluid chromatography (SFC) and SFC/mass spectrometry (MS) techniques offer the potential of making major contributions to the analysis and characterization of complex hydrocarbon mixtures, particularly for compounds of higher molecular weight and greater polarity. The combination of a chromatographic separation method with MS detection provides a powerful analytical tool as evidenced by the dominance of gas chromatography (GC)/MS for the characterization of amenable compounds. The favorable physical properties and high solvating powers of supercritical fluids allow separation of many compounds that are generally reserved for liquid chromatography (LC) owing to either thermal lability or insufficient volatility, with chromatographic resolution and efficiency per unit time approaching that of GC. These properties also allow successful interfacing to MS. Both capillary column and microbore column SFC/MS interfacing methods are described, and the advantages and limitations of each method are defined. Selected examples illustrating these methods for the characterization of complex hydrocarbon mixtures are also presented.

High‐resolution mass spectrometry for type analysis of complex hydrocarbon mixtures

High‐resolution mass spectrometry for type analysis of complex hydrocarbon mixtures

Automatic system for the high-resulution gas chromatographic analysis of gasoline-range hydrocarbon mixtures

Equipment has been developed for the high-resolution gas chromatographic analysis of complex hydrocarbon mixtures in the gasoline boiling range. The equipment can operate continuously; the data generated are automatically presented as a printed list and are also stored on magnetic cassette tape for further processing.

Gas chromatographic analysis of complex hydrocarbon mixtures

Kerosene fractions containing a wide variety of homologues and isomers of hydrocarbons of different types and complexities could be analyzed by gas chromatography on a squalane-coated open tubular column (50 m × 0.20 mm). The presence of unsaturated and saturated compounds up to a retention index ( I) of 1150 was ascertained by using a mercury perchlorate post-subtraction column (1 ft. × 1 8 in. O.D.) in series with an open tubular column, which could give only a tentative identification. The temperature dependence of the retention indices ( d I d T ) and the differences in retention indices on polar and non-polar phases (Δ I) have been considered as the basis of an extension of the Kováts retention index system, and this method of peak characterization of kerosene fractions has been investigated. SE-30 was used in a non-polar analytical column and I values were obtained at five isothermal column temperatures ranging from 130° to 170° in order to determine d I d T values for all the peaks. For the determination of Δ I values, tetracyanoethylated pentaerythritol was used in a polar analytical column. Positive and unambiguous characterization of the peaks has been made possible by using the above technique. The limitations of the present methods are discussed critically and schemes are suggested for improved analyses of complex hydrocarbon mixtures.

Schnelle analyse komplizierter kohlenwasserstoff-mischungen mittels reaktionsgaschromatographie

Rapid analysis of complex hydrocarbon mixtures by reaction gas chromatography Narrow-boiling fractions, obtained by preparative gas chromatography, are directly analysed by reaction gas chromatography. Identification of the components is based on the known differences in retention index values during hydrogenation and dehydrogenation processes on 5% Pd/Chromosorb W, 5% Pt/silica gel and 5% Pd/silica gel at 90°, 190° and 325°. The analyses of shale oil fractions by the proposed method agree well with those obtained by capillary gas chromatography. The reaction gas chromatographic method is more simple and less laborious.

The use of a gas chromatograph-mass spectrometer for the analysis of complex hydrocarbon mixtures

In the present article several examples are given of the analysis of complex hydrocarbon mixtures by means of the combined gas chromatograph-mass spectrometer LKB-9000. Several methods, published in the literature or recommended as ASTM methods, were verified for group-type analysis on the mass spectrometric part of the apparatus. With fractions which can be divided into individual components by gas chromatography, the gas chromatograph-mass spectrometer enables the mass spectra of all the components to be determined without the necessity of isolating them from the mixture. The identification of seventeen individual hydrocarbons by one analysis of the fraction of aromatic hydrocarbons which have been isolated from a petroleum fraction boiling up to 200° was shown as an example. The high sensitivity of the LKB-9000 apparatus has also been utilized to obtain mass spectra of several hydrocarbons which have been unknown up to now and which have been prepared for this purpose in very low concentration by means of the methylene insertion reaction.

The Compounds and Composition of Petroleum by Instrumental Analysis

Analysis of C6-C8 hydrocarbons in Seria crude oil was made by means of infrared and Ramanspectra, and gas chromatography combined with distillation and percolation methods. By the results of the experiments, quantitative data on 43 hydrocarbons were presented, which were comprised in all of the anticipated compounds in C6 and C7 series, and principal components in C8 series. Then, a brief discussion was made on application of these analytical instruments to routine analysis of complex hydrocarbon mixtures.

High efficiency laboratory fractionation. I. Gauze ring packing and flooding technique for laboratory columns

AbstractThe development of gauze ring random packing for laboratory scale fractionating columns is described. The packing consists of small open‐ended cylinders of wire gauze and the column is operated in such a manner that a thin film of liquid is maintained over the entire surface of these cylinders. This Aim is produced by flooding the packing before the start of a fractionation and a method of doing this is described. This packing shows a high fractionating efficiency, a fractionating performance of 84 theoretical plates per foot of height having been obtained with some columns. It has also a low hold‐up per theoretical plate and a low pressure drop. It may be used in place of other packings in existing columns.High efficiency fractionation has been developed in the Billingham laboratories of the Imperial Chemical Industries, Limited, primarily for the analysis of complex hydrocarbon mixtures. Before 1936, the most common random packings were glass and metal beads,1 Lessing rings of metal or ceramic materials,2 metal eyelets, carding teeth,3 and jack chain.4 The fractionating efficiency of these packings was low, being only equivalent to about four theoretical plates per foot of height.Notable increases in efficiency were later obtained by Fenske5 using single turn wire helices, by Stedman6 who used a regular packing in the form of conical wire gauzes and by Lecky and Ewell7 who produced a spiral packing made from wire gauze.It was found in these laboratories that the gauze packings of Stedman and Lecky and Ewell were difficult to construct, needed precision bore glass tubing to ensure high efficiency, and that a uniform flow of reflux over the gauze surface was not obtainable. To improve the liquid distribution copper gauze cylinders in the form of Lessing rings 1/8 in. × 1/8 in. were introduced into the empty spaces around the cones of the Stedman packing and a great improvement in efficiency was obtained. A further improvement was obtained by removing the gauze cones completely and replacing them with more gauze rings. Since this cylindrical packing was comparatively easy to manufacture and use, the development work on other packings was abandoned and from 1941 to 1943 a study was made of the variables affecting the performance of this packing. The results of this work are summarized in this paper. A mixture of 20% normal heptane and 80% methyl cyclohexane was used throughout for the determination of fractionating efficiency.

GEOPHYSICAL CONTRIBUTIONS TO VIBRATION MEASUREMENTS AND MICRO‐CHEMISTRY

This paper gives a brief account of the development, during the war emergency, of equipment made especially for the measurement of vibration and strain in airplane structures in flight. Experience in the design and manufacture of seismograph equipment made rapid development possible. A mass spectrometer is also described. This instrument was built originally for analysis of gas samples in connection with geochemical prospecting, was then adapted for rapid analysis of complex hydrocarbon mixtures and has found application particularly in control of refinery processes.