Robert N. Hazlett

Determination of aromatic hydrocarbon fraction in oil shale by 13C n.m.r. with magic-angle spinning

Abstract A method for estimation of aromatic content in oil shales is demonstrated. Magic-angle spinning at 2 kHz is shown to remove chemical shift anisotropy to a sufficient degree to resolve aromatic and aliphatic 13 C n.m.r. spectral regions for a lithic oil shale specimen. The proton and carbon n.m.r. relaxation parameters are such as to allow room-temperature use of this proton-enhanced 13 C n.m.r. technique as a quantitative analytical tool. Cross polarization times of a millisecond or less and experiment repetition periods of 0.5 s or less are optimum. The specimen examined is represented by an aromatic carbon fraction 0.264 ± 0.007; this determination is quite insensitive to the proton-carbon cross polarization time. Spectra for kerogen, shale oil, and dawsonite are also presented. Dawsonite may interfere in the determination of the aromatic fraction.

Supercritical fluid chromatography and supercritical fluid chromatography—mass spectrometry of marine diesel fuel

Abstract The application of capillary column suprciritcal fluid chromatography (SFC) and supercritical fluid chromatography—mass spectrometry (SFC—MS) to the analysis of the polycyclic aromatic hydrocarbon fraction of selected marine diesel fuel samples is described. The chromatographic separation methods utilized pressure or density programming techniques and small diameter (50 μm) capillary columns. This work demonstrates the feasibility of achieving hihg-resolution separations of medium polarity compounds using nonpolar carbon dioxide as the mobile phase in SFC and the successful coupling of SFC to MS to obtain mass chromatograms and reliable chemical ionization mass spectra. High resolution separations of the polycyclic aromatic hydrocarbon fractions of marine diesel fuel samples were combined with isobutane chemical ionization MS. Analysis of the more polar components will require a more polar supercritical fluid mobile phase.

Relation between fuel properties and chemical composition. 1. Jet fuels from coal, oil shale and tar sands

Abstract Jet fuels derived from coal, oil shale and tar sands were subjected to extensive chemical and physical property analysis. The straight-chain alkane content of each fractionated fuel was determined by gas chromatography and combined GC-mass spectrometry. Average parameters of the aromatic fractions of these fuels were obtained by p.m.r. spectroscopy. These analytical data were used to help explain differences in several important properties of the alternative fuels compared with jet fuel derived from petroleum. While suitable fuels can be produced from these alternative fossil-fuel sources, the processing requirements will be much different. The alternative fossil-fuel crude oils used in this work are similar to the lower-API-gravity petroleum crudes and therefore hydrocracking and delayed coking will be extensively used to produce military fuels.

CHARACTERIZATION AND STABILITY PROPERTIES OF POLAR EXTRACTS DERIVED FROM A RECENT SHALE LIQUID

ABSTRACT A shale fuel of marginal stability has been used as a source of nitrogen-rich polar extracts. Polar compounds were isolated by mild acid extraction followed by silica gel adsorption and were identified by GC/HS. Alkyl substituted pyridines were the prevalent class of compounds present in most extracts. The effects of adding these shale derived fractions as dopants to a stable shale diesel fuel (0-11) were examined in terms of sediment formation and peroxide number under accelerated storage stability test conditions. The activities of the extracts in inducing fuel instability were correlated with their composition.

Storage stability studies of fuels derived from shale and petroleum

Abstract Fuel storage degradation was monitored in the early stages by laser light scattering of developing particles at ambient temperature. Degradation products obtained by heat stressing (at 80–120 °C) of fuels enriched with specific heteroatomic compounds were analysed by n.m.r., FT-i.r. and e.s.c.a. It was found that 2,5-dimethylpyrrole (DMP) is especially deleterious to fuel stability, followed in effect by alkyl-substituted quinolines, pyridines and indoles. The oxygen and nitrogen contents of the sediments from shale-derived jet and diesel fuels which contain DMP are almost twice the corresponding values of petroleum-DMP sediment. Oxygen is incorporated in the sediments as carboxylate and carbonyl groups. P.m.r. spectra of several soluble sediments show a wide range of aromatic signals, indicating that the sediment contains much polycyclic material. Deposits formed in the presence of DMP and thiophenol contain significant amounts of nitrogen and sulphur.

Determination of liquid and solid phase composition in partially frozen middle distillate fuels

Abstract A liquid-solid separator apparatus was constructed and a method developed for the separation and characterization (g.c.-m.s.) of the crystals and liquid from partially frozen middle distillate fuels. The filtrate data were straightforward, but the precipitate presented problems in interpretation since the waxy crystals entrapped significant amounts of liquid. Since it was not possible to remove all of the entrapped liquid from the precipitate, an indirect method was derived to determine the composition of the liquid-free crystalline material. This required that the fraction of entrapped liquid in the precipitate be known, which could be determined from the g.c. data. Tracer materials in the original fuel were selected which did not crystallize out at the temperatures under study and therefore showed no appreciable concentration change with temperature. These tracer materials were used to estimate the fraction of entrapped liquid in the precipitate. Results obtained by this technique were tested and confirmed by h.p.l.c.

Diesel fuel marine and sediment analysis: Supercritical ammonia extraction and direct fluid injection — mass spectrometry

Abstract The technique of direct fluid injection-mass spectrometry has been applied to the characterization of the polar components of diesel fuel marine. Two fractionation schemes involving alumina and silica column chromatography were used for initial separation into four fractions. DFI-m.s. with ammonia chemical ionization was used to provide selective detection of the more polar DFM components. Results were also obtained for supercritical ammonia extraction of the insoluble fuel sediments formed by aging the DFM samples and for the highly polar components adsorbed on silica particles during column fractionation. The results show that DFI-m.s. allows a rapid evaluation of the molecular weight distribution of the polar components in these fuels, including the most polar materials which are not amenable to conventional extraction and analysis methods.

ACID BASE PHENOMENA IN DISTILLATE FUEL STABILITY

ABSTRACT Carboxylic and organic sulfonic acids, added to distillate fuel blends containing catalytically cracked stock, Increase deposit formation, sometimes very dramatically. The carboxylic acids data fitted into a unified treatment in relationship to hydrogen ion concentration calculated from pKa values for aqueous solutions. These acids enhance deposit formation by catalytic action and are not Incorporated into the deposit. Organic sulfonic acids may fit into the unified acid catalysis pattern but await resolution of ionization phenomena in non-aqueous solution. A tertiary aliphatic amine stabilizer was effective for reducing deposit amounts from fuel blends containing acids. This amine acts on a stoichiometric basis to counteract strong acids in the fuels. For weak acids, the amine stabilizer exhibited an effect slightly more than that for a 1:1 basis with the amount of acid in the fuel. Other amines exerted favorable behavior only if they were strong organic bases.

Jet aircraft fuel system deposits

Fuels for use in turbine powered aircraft require many limitations on properties to obtain desirable engine behavior and reliable fuel handling. One of the most critical of the jet fuel properties is that of thermal oxidation stability. This requirement became evident in the middle fifties.

A NEW LOOK AT THE MECHANISMS OF OXIDATIVE SEDIMENT FORMATION IN FUELS

ABSTRACT Alkylpyrroles have been known to promote sediment formation and discoloration of petroleum distillates for over thirty years. There has been much effort directed towards understanding the detailed mechanism of alkylpyrrole promoted sediment formation in petroleum distillates. In addition, recent studies have investigated the mechanism of alkylpyrrole sediment formation in shale derived synfuels. It is the intent of this article to critically review some of the postulated mechanisms for alkylpyrrole promoted sediment formation in fuels and then to comment on the significance of these mechanisms to our overall understanding of the field of oxidative fuel stability.