Francis P. Miknis

Characterization of organic material in coal by proton-decoupled 13C nuclear magnetic resonance with magic-angle spinning

13C n.m.r. spectra have been obtained on ten solid coal samples of various types and on three coal-derived materials, using high-power proton decoupling, cross polarization and magic-angle spinning, and provide valuable information on the carbon distribution between aromatic and non-aromatic structures in the sample. Apparent carbon aromaticities, fa′, have been determined and have been correlated with H/C ratios and as one factor in fuel values. Both solvent refining and reverse combustion (see introduction) are found to increase the aromatic fraction. These techniques should be very useful in characterizing and optimizing coal-conversion processes.

Cross-polarization magic-angle spinning 13C NMR spectra of coals of varying rank

Cross-polarization, magic-angle spinning 13C nuclear magnetic resonance spectra have been obtained on a series of coals that span the ASTM rank classification. Aromaticities thus obtained follow the classification reasonably well, increasing as rank increases NMR parameters were extensively varied to determine optimum conditions for the cross polarization contact time and pulse repetition rate. Good correlations were obtained between both the fixed carbon and the volatile matter obtained from the proximate analysis, and the aromatic carbon obtained from NMR. Generally the NMR spectra of lignites and low rank coals exhibit varying degrees of fine structure.

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.

Cross polarization magic-angle spinning 13C NMR spectra of oil shales

Cross plarization magic-angle spinning 13C NMR spectra have been obtained on oil shales representing a variety of geologic ages, origins, depositional environments, and source locations. The spectra show variations in the aliphatic and aromatic carbon distributions of the oil shales and reveal correlations between aliphatic carbon contents and potential shale oil yields. Hints of additional fine structure are present in the spectra of some samples, and examples are given of the spectral resolution that may be obtainable on other solid samples of geochemical interest.

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

Abstract 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 13 C 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.

Use of Fourier Transform infrared spectroscopy for determining oil shale properties

Abstract Fourier Transform infrared analysis has been examined as a technique for evaluating the oil-yielding potential of raw oil shales. The technique was developed recently for analysing coals, and gives a quantitative measure of aliphatic, aromatic and hydroxyl hydrogen. From these measurements, it was verified that an approximate rectilinear relation exists between the oil yield of an oil shale as determined by Fischer assay and the aliphatic hydrogen concentration in the shale. An equivalent relation was established previously between the oil yield and the aliphatic carbon concentration as determined by 13 C cross polarization n.m.r. When the oil yield is expressed in weight per cent, it is seen that the yield is only slightly less than the weight per cent of aliphatic hydrocarbons. This suggests that, under the conditions of the Fischer assay, there is almost complete conversion of the aliphatic components to oil.

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.

A common relation for correlating pyrolysis yields of coals and oil shales

Abstract Pyrolysis yields for both coals and oil shales exhibit a common relation between the original aromatic carbon content of the sample and the residual organic carbon after pyrolysis. Corresponding measurements of organic carbon distribution by solid-state 13C n.m.r. and pyrolysis yields by Fischer assay or proximate analysis have been correlated for 125 coal and oil shale samples composed of widely differing types of organic matter and inorganic constituents. Even though these measurements have been accumulated from various laboratories using different instrumentation and interpretative procedures, there is a remarkably high degree of correlation between original aromatic carbon and residue carbon. The common relation between pyrolysis yield and organic carbon distribution generally supports the previous notion that aromatic carbon is resistant to volatilization and extends this same characterization of pyrolysis behaviour to oil shale kerogen as well as coal.

Nuclear Magnetic Resonance: A Technique for Direct Nondestructive Evaluation of Source-Rock Potential

A direct nondestructive method for source-rock evaluation based on solid-state nuclear magnetic resonance (NMR) techniques is demonstrated. Direct measurement of the aliphatic and aromatic carbon structures of the total organic matter in whole rocks is provided by NMR techniques known as cross polarization with magic-angle spinning. The proportion of organic carbon present in aliphatic structures correlates with the oil-generating potential of a source rock. In addition, whether the organic matter in the rock has been altered during catagenesis can be evaluated. These evaluations are demonstrated for carbonaceous shales from the Retort and Meade Peak Phosphatic Shale Members of the Permian Phosphoria Formation. The NMR results show that the Retort shales have a high poten ial to generate oil, but the Meade Peak shales, having already undergone thermal alteration, have a low potential to generate additional oil.