Chemical and nanometer-scale structure of kerogen and its change during thermal maturation investigated by advanced solid-state 13C NMR spectroscopy

Mao, Jingdong; Fang, Xun; Lan, Yeqing; Schimmelmann, Arndt; Mastalerz, María; Xu, Ling; Schmidt‐Rohr, Klaus

doi:10.1016/j.gca.2009.12.029

Cited by 147 publications

(158 citation statements)

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“…The wide application of 13 C cross polarization magic angle spinning (CP/MAS) technique has significantly promoted our knowledge on coal chemical structures [40][41][42][43][44][45][46][47][48]. Spectral-editing and peak-fitting techniques have been well established to identify specific functional groups from the spectra [49][50][51][52], and the high-resolution NMR methods allow for the measurement of the relative abundance of aromatic, aliphatic, phenolic, and carboxylic carbons [53,54]. Moreover, the chemical structures of coal lithotypes and macerals were also investigated by 13 C-NMR [55,56].…”

Section: Introductionmentioning

confidence: 99%

13C-NMR Study on Structure Evolution Characteristics of High-Organic-Sulfur Coals from Typical Chinese Areas

Wei

Tang

2018

Minerals

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Abstract:The structure evolution characteristics of high-organic-sulfur (HOS) coals with a wide range of ranks from typical Chinese areas were investigated using 13 C-CP/MAS NMR. The results indicate that the structure parameters that are relevant to coal rank include CH 3 carbon (f al *), quaternary carbon, CH/CH 2 carbon + quaternary carbon (f al H ), aliphatic carbon (f al C ), protonated aromatic carbon (f a H ), protonated aromatic carbon + aromatic bridgehead carbon (f a H+B ), aromaticity (f a CP ), and aromatic carbon (f ar C ). The coal structure changed dramatically in the first two coalification jumps, especially the first one. A large number of aromatic structures condensed, and aliphatic structures rapidly developed at the initial stage of bituminous coal accompanied by remarkable decarboxylation. Compared to ordinary coals, the structure evolution characteristics of HOS coals manifest in three ways: First, the aromatic CH 3 carbon, alkylated aromatic carbon (f a S ), aromatic bridgehead carbon (f a B ), and phenolic ether (f a P ) are barely relevant to rank, and abundant organic sulfur has an impact on the normal evolution process of coal. Second, the average aromatic cluster sizes of some super-high-organic-sulfur (SHOS) coals are not large, and the extensive development of cross bonds and/or bridged bonds form closer connections among the aromatic fringes. Moreover, sulfur-containing functional groups are probably significant components in these linkages. Third, a considerable portion of "oxygen-containing functional groups" in SHOS coals determined by 13 C-NMR are actually sulfur-containing groups, which results in the anomaly that the oxygen-containing structures increase with coal rank.

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Section: Introductionmentioning

confidence: 99%

13C-NMR Study on Structure Evolution Characteristics of High-Organic-Sulfur Coals from Typical Chinese Areas

Wei

Tang

2018

Minerals

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“…During the recent years, many advanced solid-state 13 C NMR techniques have been developed, improved, and applied for characterizing complexity of NOM in algaes, plants, soils, sediments, and kerogens [23,43]; Mao and Schmidt-Rohr [24][25][26], Mao et al [27][28][29]. These advanced solid-state NMR techniques include 13 C DP/ MAS NMR, quantitative DP/MAS plus dipolar dephasing, 13 C chemical-shift anisotropy filter (CSA), and CH, CH 2 spectral editing [28].…”

Section: Introductionmentioning

confidence: 99%

“…These advanced solid-state NMR techniques include 13 C DP/ MAS NMR, quantitative DP/MAS plus dipolar dephasing, 13 C chemical-shift anisotropy filter (CSA), and CH, CH 2 spectral editing [28]. They overcome the drawbacks of conventional CP/MAS techniques and enable us to obtain more detailed chemical and structural information on various types of NOM.…”

Section: Introductionmentioning

confidence: 99%

“…The identification and quantification of specific functional groups such as CH 2 , CH 3 , aromatic CH, aromatic C-O, protonated aromatic C, nonprotonated aromatic C, carbonyl C, and carboxyl C can be achieved. The structural parameters such as aromaticity and aromatic cluster size can also be estimated by using spectral analysis and long-range 1 H- 13 C recoupled dipolar dephasing [4,28]. These advanced techniques provide reliable measurements and have proven to be powerful tools for the characterization of NOM [28].…”

Section: Introductionmentioning

confidence: 99%

“…The structural parameters such as aromaticity and aromatic cluster size can also be estimated by using spectral analysis and long-range 1 H- 13 C recoupled dipolar dephasing [4,28]. These advanced techniques provide reliable measurements and have proven to be powerful tools for the characterization of NOM [28]. In the following sections, we will discuss several case studies (algae organic matter, pollen organic matter, sediment organic matter, atmospheric deposition particles, and kerogens) to prove the applicability of advanced 1D solid-state in this research field.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Composition and structure of natural organic matter through advanced nuclear magnetic resonance techniques

Zhang

Duan

Huang

et al. 2017

Chem. Biol. Technol. Agric.

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Natural organic matter (NOM) plays important roles in biological, chemical, and physical processes within the terrestrial and aquatic ecosystem. Despite its importance, a clear and exhaustive knowledge on NOM chemistry still lacks. Aiming to prove that advanced solid-state 13 C nuclear magnetic resonance (NMR) techniques may contribute to fill such a gap, in this paper we reported relevant examples of its applicability to NOM components, such as biomass, deposition material, sediments, and kerogen samples. It is found that nonhydrolyzable organic carbons (NHC), chars, and polymethylene carbons are important in the investigated samples. The structure of each of the NHC fractions is similar to that of kerogens, highlighting the importance of selective preservation of NOM to the kerogen origin in the investigated aquatic ecosystems. Moreover, during the artificial maturation experiments of kerogen, the chemical and structural characteristics such as protonated aromatic, nonprotonated carbons, and aromatic cluster size play important roles in the origin and variation of nanoporosity during kerogen maturation.

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Relaxation mechanisms and shales

Washburn

2014

Concepts Magnetic Resonance

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Unconventional petroleum resources present in shales have recently seen increased development due to growing demand for energy worldwide, declining conventional petroleum discoveries, and improved technology for production. Shale reservoirs differ from more conventional reservoirs in both matrix composition and structure, tending to be low in porosity and ultralow in permeability, making traditional laboratory characterization methods difficult to apply. The noninvasiveness of nuclear magnetic resonance (NMR) makes it a favored technique for shale analysis. However, interpretation of NMR relaxometry results for shales is more complex than in traditional reservoirs. Surface relaxivity in conventional reservoirs is predominantly caused by the interaction of fluid molecules with paramagnetic impurities on pore surfaces. However, in shales, small pore sizes coupled with the presence of hydrogen-rich organic matter can result in more interactions. This article discusses different relaxation mechanisms that may be present in shales and situations where they are relevant. Surface relaxation in organic matter is likely caused by homonuclear dipolar coupling, not paramagnetic impurities, and as such, will have a significant temperature dependence. Due to the small pore sizes in shales, the effect of internal gradients on the signal appears negligible in almost all situations. Analysis of transverse relaxation resulting from organic solids by an inverse Laplace transform may lead to results that are anomalously short and overcall signal intensity. Diffusional coupling between the shale pores confounds interpretation of the NMR response as a pore size distribution. There also appears to be rapid exchange of magnetization between mobile and immobile phases in the samples.

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Chemical and nanometer-scale structure of kerogen and its change during thermal maturation investigated by advanced solid-state 13C NMR spectroscopy

Cited by 147 publications

References 46 publications

13C-NMR Study on Structure Evolution Characteristics of High-Organic-Sulfur Coals from Typical Chinese Areas

13C-NMR Study on Structure Evolution Characteristics of High-Organic-Sulfur Coals from Typical Chinese Areas

Composition and structure of natural organic matter through advanced nuclear magnetic resonance techniques

Relaxation mechanisms and shales

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