Analysis of heavy crude oil residues by carbon-13 Fourier transform nuclear magnetic resonance spectrometry

Hájek, Milan; Sklenar, Vladimir; Šebor, Gustav; Lang, I.; Weisser, Otto

doi:10.1021/ac50027a027

Cited by 28 publications

(17 citation statements)

References 8 publications

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“…The contents of paramagnetic meral ions were determined by AAS measurements and concentrations were by about one order of magnitude lower than the values in heavy crude oil residues (12). The contents are summarized in Table I to- gether with contents of organic free radicals (OFR), which were measured by ESR spectrometry.…”

Section: R E S U L T S a N D Discussionmentioning

confidence: 97%

“…The magnitude of the NOE factor depends on the dipoledipole contribution to relaxation: (12) indicate that methods of measurements (I-111), delay times, and integration affect the precision of the measurements of the aromaticity. In order to know which of these ones is more important, the analysis of variance (25,26) was performed for all measured samples C 1-C 5.…”

Section: ( 5 )mentioning

confidence: 99%

“…Apparent simplicity of these measurements is, however, complicated by a number of factors, which usually alter the simple relationship between integrated intensities of lines and numbers of nuclei a t resonance. Some of them have been discussed by others (9,(12)(13)(14)(15)(16)(17)(18) enhancements (NOE) and spin-lattice relaxation rates of carbon-13 nuclei. Their unfavorable influences upon the results of the quantitative analysis by carbon-13 NMR may be eliminated by gated decoupling (19) or by use of relaxation reagents (20).…”

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confidence: 99%

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Analysis of coal asphaltenes by carbon-13 Fourier transform nuclear magnetic resonance spectrometry

Sklenar¹,

Hájek²,

Šebor³

et al. 1980

Anal. Chem.

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The influences of three different methods on the accuracy of aromaticity determination of coal asphaitenes by carbon-13 FT NMR were investigated. The results are compared on the basis of statlstical evaluation by means of a variance analysis method. The influences of nuclear Overhauser enhancements and spln-lattice relaxatlon times upon the results of analysis and their values for measured samples are dlscussed. Some conclusions concerning the size of the particles in solution are presented.

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Section: R E S U L T S a N D Discussionmentioning

confidence: 97%

Section: ( 5 )mentioning

confidence: 99%

mentioning

confidence: 99%

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Analysis of coal asphaltenes by carbon-13 Fourier transform nuclear magnetic resonance spectrometry

Sklenar¹,

Hájek²,

Šebor³

et al. 1980

Anal. Chem.

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“…This wide range forces a compromise in experimental conditions, even when a relaxation agent has been used to dramatically reduce the needed relaxation times. These accommodations have been thoroughly documented in the chemical literature. − Particularly useful is the work performed by Burger et al where the researchers provide a thorough description of the experimental conditions for the quantitative 13 C and 1 H NMR of complex fuels, identifying the differences between the predicted and observed values for several challenging chemicals typically used in surrogate fuels, as well as providing the relative uncertainty for each integration region of complex jet fuels . Ure et al provides a similar comparison, identifying the absolute differences observed in a set of model fuels in their very thorough methods paper .…”

Section: Introductionmentioning

confidence: 99%

Methodology for the Development of Empirical Models Relating ¹³C NMR Spectral Features to Fuel Properties

et al. 2020

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Effective formulation of new gasoline or diesel fuels for internal combustion engines would benefit from the development of reliable models for predicting key fuel properties based on a set of molecular descriptors obtained from a single measurement. This is particularly relevant in the case of renewable fuels, where the available fuel sample quantity may be limited. In this work, we present a statistically based methodology for building empirical models to predict multiple properties from onedimensional 13 C nuclear magnetic resonance (NMR) spectra measured on around 200 μL of a liquid fuel. NMR spectra contain information about the molecular composition of a sample and the carbon types and molecular substructures therein. Our approach uses this information to build sparse, interpretable models, where the predicted properties are linked to specific molecular features. The approach takes into consideration the constrained nature of the features making up the one-dimensional NMR spectrum, which, after standardization, represents a relative fuel composition. We point to the limitations in interpretability that arise when building this type of empirical predictive model and suggest how these limitations may be diminished. Among the many properties important for maximizing engine performance and minimizing emissions, we build models that predict derived cetane number and distillation temperatures, as these are of particular interest because of their links to fuel economy, drivability, and engine-out emissions. The results suggest that the properties of interest may be impacted by only a few of the 27 13 C NMR regions represented in the data, pointing to new directions for further testing in the development of improved fuels.

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“…Attempts6 at quantitative measurements have then to be made by using relaxation agents such as chromium acetylacetonate, iron acetylacetonate (all paramagnetic substances). In their studies, Shoolery and Budde2 and Hajek et al 3 have measured the c.m.r. spectra of some crudes as such and also by using methods of (i) gated decoupling; (ii) gated decoupling with relaxation agent; and (iii) broad-band decoupling with relaxation agent.…”

Section: Introductionmentioning

confidence: 99%

Compositional study of crude oils using fourier transform n.m.r. Characterisation

Srivastava

Singh

1980

J. Chem. Technol. Biotechnol.

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The Fourier transform (FT) 'H-and 13C-nuclear magnetic resonance (n.m.r.) spectra of three crude oils have been recorded at room temperature on a Jeol pulsed FT-n.m.r. spectrometer. The branchiness index has been calculated from 'H-n.m.r. spectra and the percentage of aromatic carbons (% CA) from the 13C-spectra. The results are discussed and the usefulness of n.m.r. techniques in such studies considered.

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Analysis of heavy crude oil residues by carbon-13 Fourier transform nuclear magnetic resonance spectrometry

Cited by 28 publications

References 8 publications

Analysis of coal asphaltenes by carbon-13 Fourier transform nuclear magnetic resonance spectrometry

Analysis of coal asphaltenes by carbon-13 Fourier transform nuclear magnetic resonance spectrometry

Methodology for the Development of Empirical Models Relating ¹³C NMR Spectral Features to Fuel Properties

Compositional study of crude oils using fourier transform n.m.r. Characterisation

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Analysis of heavy crude oil residues by carbon-13 Fourier transform nuclear magnetic resonance spectrometry

Cited by 28 publications

References 8 publications

Analysis of coal asphaltenes by carbon-13 Fourier transform nuclear magnetic resonance spectrometry

Analysis of coal asphaltenes by carbon-13 Fourier transform nuclear magnetic resonance spectrometry

Methodology for the Development of Empirical Models Relating 13C NMR Spectral Features to Fuel Properties

Compositional study of crude oils using fourier transform n.m.r. Characterisation

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Product

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Methodology for the Development of Empirical Models Relating ¹³C NMR Spectral Features to Fuel Properties