Thermophysical properties of Devonian shales

A detailed study of the thermophysical properties of Devonian shales from the central and eastern United States has been carried out. Thermal conductivity, thermal diffusivity, specific heat and dielectric constant data are presented. A Michigan shale sample with an oil yield of 28 litres per metric ton (1 t^?1) and a Kentucky shale (oil yield: 52 l t^?1) were selected. The specific heats of these shales are in the range 0.20–0.30 cal gm^?1 °C^?1, and increase with increasing temperature. The thermal conductivity (κ) of the two shale samples are comparable (ca. 1 W m^?1 °C^?1). The κ values show only a weak temperature dependance. The thermal diffusivity (α) of these shales range from 0.3–0.5 × 10^?2 cm² s^?1 and tend to decrease with increasing temperature. The dielectric constants show anomalously high values at temperatures above 200 °C. This effect is indicative of interfacial polarization mechanisms presumably arising from loss of water and onset of pyrolysis of the shale organic matter. Comparison of the trends in thermophysical behaviour of Devonian shales with data obtained previously on Green River oil shales is presented. The importance of thermophysical measurements in on-field applications in oil shale technology is highlighted.     

N.m.r. study of US Eastern and Western shale oils produced by pyrolysis and hydropyrolysis

Shale oils produced from US Eastern and Western oil shales by pyrolysis and hydropyrolysis processes have been investigated by both ¹H and ¹³C high-resolution n.m.r. techniques. Eastern shale oils produced by hydropyrolysis, and subsequently hydrotreated, were also included. From the n.m.r. data of the shale oils, the average molecular structure parameters were calculated. These parameters quantitatively represent the differences observed in the n.m.r. spectra of the various shale oils because of changes in the chemical composition. Mol percentages of aromatics, olefins, and alkanes were also determined for the shale oils, and show that the composition of the shale oil is dependent upon the geographic origin of the oil shale, the pyrolysis method, and the hydrogenation process. In addition to the study of shale oils, solid-state ¹³C n.m.r. spectra of Eastern and Western oil shales before and after pyrolysis and hydropyrolysis were obtained. The spectral data show that the carbon aromaticities for the Eastern oil shales and shale oils are higher than for the Western oil shale and shale oils. The data also show that hydropyrolysis relative to pyrolysis reduces the amount of residual organic carbon remaining on the spent shales. Carbon aromaticity data for both oil shale and shale oil suggest that the organic moieties present in kerogen may be retained in the shale oils to a greater extent after hydropyrolysis than after pyrolysis.     

Correlation between oil yields of oil shales and 13C nuclear magnetic resonance spectra

Using the cross polarization/dipolar decoupling method, ¹³C n.m.r. spectra have been obtained on twenty oil shales and kerogens from around the world. A correlation is found between the integrated signal intensity of the aliphatic region of the spectra and the oil yields of the shales.     

Characterization of the residual carbon in retorted oil shale by solid-state 13C n.m.r.

Cross-polarization and magic-angle spinning suggest that the aromatic carbons in oil shales are largely inert to thermal processes and instead are responsible for the carbonaceous residue obtained during retorting. These results are based on ¹³C n.m.r. measurements of the organic carbon distribution of oil shales, before and after Fischer assaying, and for oil shales of different grades, geographic location, geologic ages and formations. The n.m.r. measurements suggest further that measurements of the organic carbon distribution of oil shales heated to various temperatures have practical relevance, and that this information can be of value in discriminating between unconverted kerogen and residual carbon in heated oil shales.     

Determination of carbon centre types in solid fuel materials by CP/MAS n.m.r.

Methyl, quaternary aliphatic and aromatic, and hydrogen-bearing aliphatic and aromatic carbon centres in solid fuel samples have been determined quantitatively by pulse-programmed ¹³C n.m.r. coupled with elemental analysis. The method may be used for unaltered samples of oil shales, coals, etc., and has been tested on model compounds representative of components in these materials.     

Comments on the Modified Fischer Assay of Eastern oil shales of Kentucky

The Modified Fischer Assay is the accepted method for evaluating the potential liquid fuel yield of an oil shale. For a given shale, percent of Fischer Assay oil yield has become the standard used for judging technologies. The method has been developed for and is well understood when applied to oil shales in the western United States. However, the assay can be successfully applied to eastern United States oil shales only if care is taken in several areas that prove less important for its successful application to western shales. In particular, standardized sample preparation and handling with minimum air exposure of pulverized shale is required; a well-controlled and reproducible heating profile during retorting must be employed; and consistently effective liquid product collection must be accomplished. These considerations have a major influence on assay accuracy. Only with care in these areas, can Modified Fischer Assays suitable for eastern shale resource evaluations and technology comparisons be obtained.     

E.p.r. study of paramagnetic metal ions in Victorian brown coal

Electron paramagnetic resonance (e.p.r.) spectra of some Victorian brown coals in the raw state possess absorbances attributable to metal ion radicals. E.p.r. signals at g≈4.3 and g≈2 (multiplet) have been assigned to iron(III) and manganese(II), respectively. The g≈4.3 signal intensity does not appear to vary directly with the total iron content of the raw coal. The amplitudes of the metal ion signals were found to change with drying of the coal, and were reduced to zero on removal of the metal ions by acid washing. Ion exchange of the sodium form of brown coal with iron(III) reintroduced the g≈4.3 signal and produced an additional broad signal centred at g≈2. The intensity of the latter signal was related to the total iron content of the iron(III)-exchanged coal. The extent of iron(III) exchange was shown to be pH dependent. Other paramagnetic ions, such as oxovanadium(IV), manganese(II) and copper(II) when exchanged onto brown coal produced their characteristic metal ion spectra.     

Thermogravimetry and decomposition kinetics of British Kimmeridge Clay oil shale

The characteristics of volatile matter evolution and the kinetics of thermal decomposition of British Kimmeridge Clay oil shale have been examined by thermogravimetry. TG has provided an alternative to the Fischer assay for shale grade estimation. The following relation has been derived relating TG % volatiles yield to the shale gravimetric oil yield: oil yield (g kg^?1) = (TG volatiles, % × 5.82) ? 28.1 ± 14.5 g kg^?1. A relationship has also been established for volumetric oil yield estimation: oil yield (cm³ kg^?1) = (TG volatiles, % × 4.97) – 5.43. TG is considered to give a satisfactory estimation of shale oil yield except in certain circumstances. It is found to be less reliable for low yield shales producing <≈40 cm³ kg^?1 of oil (≈10 gal ton^?1) where oil content of the TG volatiles is low: volumetric yield estimation accuracy is affected by variations in shale oil specific gravity. First order rate constants, k = 4.82 × 10^?5s^?1 (346.3 cm³ kg^?1shale) and k = 6.78 × 10^?5s^?1 (44.6cm³ kg^?1shale) have been obtained for the devolatilization of two Kimmeridge oil shales at 280 °C using isothermal TG. Using published pre-exponential frequency factors, an activation energy of ≈57.9 kJ mol^?1 is calculated for the decomposition. Preliminary kinetic studies using temperature programmed TG suggest at least a two stage process in the thermal decomposition, with two maxima in the volatiles evolution rate at ≈450 and 325 °C being obtained for some samples. Use of published pre-exponential frequency factors gives activation energies of ≈212 and 43 kJ mol^?1 for these two stages in the decomposition.     

Analysis of rich oil shales by 1H nuclear magnetic resonance

The potential yields of rich oil shales from the Colorado Green River Basin were measured by pulsed ¹H nuclear magnetic resonance. The rates of decay of the signals, as quantified by their second moments, decreased with increasing organic content. This implies that whenever shales of widely varying yields are being compared, their free-induction-decays must be extrapolated to time zero.     

Chattanooga Shale—An Important U. S. Mineral Resource

Abstract

Chattanooga shale, a major component of the eastern Devonian shales, covers a wide area from lower Kentucky through Tennessee and into northern Alabama. It contains sizable resources of oil and several critically needed metals. Leaching experiments with sulfuric acid have demonstrated that excellent trace metal solubilization can be obtained from hydroretorted Chattanooga shale, i.e. the solid residue remaining after the raw shale has been processed to produce oil and/or gas.     

Emission analysis of CdO–Bi2O3–B2O3 glasses doped with Eu and Tb

This article reports on the emission properties of cadmium bismuth borate (CdBiB) glasses as a function of doping concentrations of Eu³⁺ and Tb³⁺ ions. The functional groups present in the glasses have been identified by analyzing FT-IR spectra. The emission spectra of Eu³⁺ and Tb³⁺:CdBiB glasses have shown reddish green emissions at 616 nm (⁵D₀→⁷F₂) under the excitation at 465 nm and at 547 nm (⁵D₄→⁷F₅) under the excitation at 485 nm, respectively. The Judd–Ofelt (J–O) theory was applied to evaluate the J–O intensity parameters from the absorption and the emission spectra; by using the J–O intensity (Ω_λ) parameters, spontaneous emission transition probability (A), total radiative transition rate (A_T), radiative lifetime (τ_R) and branching ratios (β) of the various emission transitions have been computed for both Eu³⁺ and Tb³⁺:CdBiB glasses. The quenching behavior in the emission intensity with increased concentration of Eu³⁺ and Tb³⁺ was observed, which could be useful for optimizing the compositions toward practical applications.     

E.p.r. study of organic free radicals in Victorian brown coal

The signals at g≈2 in the e.p.r. spectra of Victorian brown coals are attributed to organic free radicals. Mathematical lineshape analysis and variation of linewidth with frequency suggested that the observed signals at low power levels are mainly homogeneously broadened. Power saturation experiments, however, resolved the signals to show the presence of from one to three resonances due to different free radical types.     

Oil-shale analysis by CP/MAS-13C n.m.r. spectroscopy

Solid-state ¹³C n.m.r. (CP/MAS-¹³C n.m.r.) spectroscopy provides a direct method for estimating potential oil yields of oil shale formations. Relative aliphatic resonance areas correlate linearly with oil yield and provide a method for oil yield estimation that obviates the need to determine weight per cent organic carbon for each specimen. This direct measurement is performed using an internal area standard, the carbonyl resonance of N-(2-¹³C-propanonyl)-N,N,N-trimethylammonium chloride, to monitor spectrometer sensitivity. Oil shale samples obtained as a function of depth at a site in the Mahogany Zone of the Green River Formation show a near-constant aliphatic carbon fraction, f_al ≡ (1?f_a), and a twofold, nonlinear variation in oil yield over the vertical dimension of the sampling. Aliphatic carbon resonance band shape changes among these samples are interpreted qualitatively as reflecting a two component mixture composed of the condensed alicyclic structures which link together to form the kerogen matrix and an n.m.r.-distinct but not necessarily chemically distinct contribution from normal-long chain hydrocarbon residues.     

Radical copolymers of 2-vinyl pyridine with methyl acrylate and methacrylate. A study of microstructures by 1H n.m.r.

Radical copolymerization of 2-vinyl pyridine with methyl acrylate and methacrylate, respectively, has been carried out in benzene solution with low conversion. The reactivity ratios for the two systems, have been determined using the Fineman-Ross and Kelen-Tüdös methods. The values obtained satisfy the terminal model of copolymerization. The signals sensitive to sequence distribution and configuration in the ¹H n.m.r. spectra are αCH₃ and OCH₃ from methyl methacrylate, OCH₃ from methyl acrylate and the aromatic proton signal from 2-vinyl pyridine. The configurational model for the two types of copolymers is discussed using the information from the signals together with influence of the neighbouring and next-neighbour units on signal splitting.     

Structural development and magnetic phenomenon in Zn–Cr–Fe multi oxide nano-crystals

The Cr³⁺ ions doped multi-oxide ZnFe_2−xCr_xO₄ ferrite nanoparticles have been synthesized by chemical co-precipitation method. Site occupancies of Zn²⁺, Cr³⁺ and Fe³⁺ ions were analyzed using X-ray diffraction data and Buerger's method. The effect of the constituent phase variation on the magnetic hysteresis behavior was examined by saturation magnetization which decreases with the increase in Cr³⁺ content in place of Fe³⁺ ions at octahedral B-site. Typical blocking temperature (T_B) around 90 K was observed by zero field cooling and field cooling magnetization study. Room temperature Mössbauer spectra show two paramagnetic doublets (tetrahedral and octahedral sites). The isomer shifts of both doublets decrease whereas quadrupole splitting and relative area of tetrahedral A-site increases with increasing Cr³⁺ substitution. The dielectric constant (measured on compositions x=0, 0.4, 0.8 and 1.0) increases when the temperature increases as in the semiconductor. This behavior is attributed to the hopping of electrons between Fe²⁺ and Fe³⁺ ions with a thermal activation.     

Quantitative determination of the monoclinic crystalline phase content in polyethylene by 13C n.m.r.

Solid-state ¹³C n.m.r. spectroscopy involving the techniques of cross-polarization (CP), magic angle spinning (MAS), and high power proton decoupling, has been used to determine quantitatively the ratio of monoclinic to orthorhombic crystalline phases in compression moalded ultra-high molecular weight polyethylene (UHMWPE) sheet which had been stretched uniaxially. Criteria for expecting quantitative relative intensities in ¹³C CP-MAS spectra are discussed. Attenuation of the non-crystalline (NC) signals relative to crystalline signals was observed. Experiments were therefore carried out to ascertain whether measurable relative intensity distortions exist between the monoclinic crystalline phase (MCP) and the orthorhombic crystalline phase (OCP) resonances due to possible differences in proton ‘spin diffusion’ between the NC and the two crystalline phases during cross-polarization. No relative intensity distortions were detected. This result, coupled with experiments in which spin diffusion was monitored at times longer than those used for cross-polarization, suggests that the average distance from the protons in a given crystalline phase to the nearest protons in the NC regions is the same for the MCP and the OCP. Finally, non-spinning ¹³C spectra of the deformed polyethylene were recorded to determine the orientation of the chains in the crystalline and NC regions. The Hermans orientation function, F_c, was determined independently for the crystalline (combined OCP and MCP) and NC regions, and found to be 0.66 + 0.06 and 0.23 + 0.04 respectively. The occurrence of orientation in the NC regions may be evidence for internal stresses, which, it is suggested, also stabilize the metastable MCP in the stretched sample.     

Novel Langmuir–Blodgett film with ternary europium complex of long chain mono-eicosyl cis-butene dicarboxylate and 1,10-phenanthroline: Cooperative assembly and luminescence

Maleic anhydride is modified by two long chain alcohol (1-hexadecanol, 1-octadecanol) to the corresponding monohexadecyl cis-butene dicarboxylate (MAH) and monooctadecyl cis-butene dicarboxylate (MAO), respectively. Then the two ternary europium complexes with the as-derived long chain monoester and 1,10-phenanthroline (Phen) are synthesized and characterized. Furthermore the ultra thin luminescent Langmuir–Blodgett (LB) films have been prepared by using the subphase containing Eu³⁺ by the film-formation ability of long chain monoester, whose luminescence has been sensitized by phen. The layer structure of the LB films is demonstrated by low-angle X-ray diffraction and the AFM study reveals that the LB films are uniform and crack free, and the films mainly consist of closely packed lines or stripes. The LB films present characteristic luminescence of Eu³⁺, and the signal can be detected from a single layer.     

Oxygen ion conductivity studies of bismuth and bismuth-calcium co-doped ThO2

A series of trivalent (Bi³⁺) doped and divalent (Ca²⁺) co-doped ThO₂ samples i.e., Th_0.50-xCa_xBi_0.50O_2-δ (x = 0.00, 0.05, 0.10, 0.15 and 0.20) have been synthesized by citrate-nitrate solution combustion route and investigated in the context of oxygen ion conductivity and dielectric relaxation phenomena. The Rietveld refinement of the Powder X-ray diffraction data confirmed monophasic fluorite structures (S.G. Fm$\stackrel{￣}{3}$m) for calcium concentrations up to 20 mol %. The optical band gap decreased with the increase in Ca²⁺ concentration up to 10 mol %. In contrast, the defect band's intensity in the Raman spectra increased due to oxygen vacancies on divalent addition. The quantitative aspect of oxygen vacancy and defect concentration was derived from Raman spectra. The crystallographic index application was further employed to interpret the optimum doping concentration to maximize oxide ion conductivity. Remarkably high oxide ion conductivity (~10^?3 S/cm) was observed for Bi³⁺ doped (50 mol %), and Bi³⁺ (50 mol %)-Ca²⁺ (10 mol %) co-doped ThO₂ samples at 773 K. The Nyquist plot exhibited grain contribution for low dopant levels. Both grain and grain boundary contribution were present in the higher dopant concentrations. Conductivity, dielectric, and modulus properties of doped and co-doped samples have been compared, from which 10 mol % of Ca²⁺-doping was identified to be the optimum concentration.