Thermal Chemistry of Nitrogen in Kerogen and Low-Rank Coal

Kelemen, S.R.; Freund, Howard; Gorbaty, Martin L.; Kwiatek, P. J.

doi:10.1021/ef9802126

Cited by 79 publications

(64 citation statements)

References 56 publications

(126 reference statements)

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“…Our data agree with Kelemen et al's (1998Kelemen et al's ( , 1999 observation of a strong relative increase of quaternary nitrogen with increasing maturity. Following extensive high-temperature pyrolysis of nitrogencontaining amorphous carbon precursors in the laboratory, essentially all edge-located nitrogen atoms (Fig.…”

Section: Anthracitesupporting

confidence: 92%

“…XPS data of solid pyrolysis residues indicate that programmed pyrolysis in the laboratory can reproduce some trends in naturally metamorphosed samples (Fig. 7), for example a decrease in the relative abundance of pyrrolic nitrogen and an increase in the relative abundance of quaternary N-C 3 nitrogen, especially when kerogen type III is used as a starting material (Kelemen et al, 1998(Kelemen et al, , 1999. Important differences remain between artificial and natural paths of chemical evolution:…”

Section: The Role Of H O-containing Hot Fluids During Transformationmentioning

confidence: 99%

“…• Pyridinic nitrogen associated with an adjacent or nearby located -OH group forming an H-bridge (Kelemen et al, 1999) • Ammonium salt • N-C3 as above in "Metamorphic nitrogen moieties".…”

Section: Elemental Isotopic and Thermal Analysesmentioning

confidence: 99%

“…The organic carbon content C org is expressed as weight % on a dry, ash-free basis (daf). Vitrinite reflectance is given as R max (% Trace amounts of quaternary nitrogen in the pre-metamorphic stage reflect a form of pyridinic nitrogen associated with adjacent or nearby hydroxyl or carboxyl groups that are protonated via formation of H-bridges (Kelemen et al, 1999; see structural example in Table 2). Quaternary nitrogen XPS peaks in some materials may also reflect the presence of ammonium salts (Gong et al, 1997; NIST XPS database) and protonated amines (e.g., Clark et al, 1976;Vidyadhar et al, 2003), although this has limited relevance for coals and kerogens where these species are essentially absent.…”

Section: Sub-peak N-q1: Organic N-cmentioning

confidence: 99%

“…Laboratory pyrolysis experiments at high temperatures are typically performed in the absence of water, for example in a flow of inert gas at ambient pressure (e.g., Littke et al, 1995;Boudou and Espitalié, 1995;Kelemen et al, 1998Kelemen et al, , 1999. In contrast, deep sedimentary environments provide ubiquitous and abundant hot H, O-containing formation fluids at considerable pressure.…”

Section: The Role Of H O-containing Hot Fluids During Transformationmentioning

confidence: 99%

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Organic nitrogen chemistry during low-grade metamorphism

Boudou

Schimmelmann

Ader

et al. 2008

Geochimica et Cosmochimica Acta

136

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-Most of the organic nitrogen (N org ) on Earth is disseminated in crustal sediments and rocks in the form of fossil nitrogen-containing organic matter. The chemical speciation of fossil N org within the overall molecular structure of organic matter changes with time and heating during burial. Progressive thermal evolution of organic matter involves phases of enhanced elimination of N org and ultimately produces graphite containing only traces of nitrogen. Long-term chemical and thermal instability makes the chemical speciation of N org a valuable tracer to constrain the history of sub-surface metamorphism and to shed light on the subsurface biogeochemical nitrogen cycle and its participating organic and inorganic nitrogen pools. This study documents the evolutionary path of N org speciation, transformation and elimination before and during metamorphism and advocates the use of XRay Photoelectron Spectroscopy (XPS) to monitor changes in N org speciation as a diagnostic tool for organic metamorphism. Our multidisciplinary evidence from XPS, stable isotopes, traditional quantitative coal analyses, and other analytical approaches shows that at the metamorphic onset N org is dominantly present as pyrrolic and pyridinic nitrogen. The relative abundance of nitrogen substituting for carbon in condensed, partially aromatic systems (where N is covalently bonded to three C atoms) increases exponentially with increasing metamorphic grade, at the expense of pyridinic and pyrrolic nitrogen. At the same time, much N org is eliminated without significant nitrogen isotope fractionation. The apparent absence of Rayleigh-type nitrogen isotopic fractionation suggests that direct thermal loss of nitrogen from an organic matrix does not serve as a major pathway for N org elimination. Instead, we propose that hot H, O-containing fluids or some of their components gradually penetrate into the carbonaceous matrix and eliminate N org along a progressing reaction front, without causing nitrogen isotope fractionation in the residual N org in the unreacted core of the carbonaceous matrix. Before the reaction front can reach the core, an increasing part of core N org chemically stabilizes in the form of nitrogen atoms substituting for carbon in condensed, partially aromatic systems forming graphite-like structural domains with delocalized π-electron systems (nitrogen atoms substituting for "graphitic" carbon in natural metamorphic organic matter). Thus, this nitrogen species with a conservative isotopic composition is the dominant form of residual nitrogen at higher metamorphic grade.

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Section: Anthracitesupporting

confidence: 92%

Section: The Role Of H O-containing Hot Fluids During Transformationmentioning

confidence: 99%

Section: Elemental Isotopic and Thermal Analysesmentioning

confidence: 99%

Section: Sub-peak N-q1: Organic N-cmentioning

confidence: 99%

Section: The Role Of H O-containing Hot Fluids During Transformationmentioning

confidence: 99%

See 3 more Smart Citations

Organic nitrogen chemistry during low-grade metamorphism

Boudou

Schimmelmann

Ader

et al. 2008

Geochimica et Cosmochimica Acta

136

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Relationship between nitrogenous species in coals and volatile nitrogen‐containing yields during pyrolysis

Wang

Zhang

Zhao

et al. 2010

Asia-Pacific J Chem Eng

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Nitrogen in coal is a major pollutant that inhibits the effective and extensive utilization of coal, and hence, nitrogen removal during and after coal combustion is of great importance. Future utilization of coal requires accurate knowledge of its structure and properties. Datong coal (DT, bituminous coal), Huolinhe coal (NM, brown coal) and Fushun coal (FS, brown coal) were pyrolyzed in a fixed-bed reactor under argon atmosphere with a heating rate of 15• C/min. X-ray photoelectron spectroscopy (XPS) was used to investigate the presence of nitrogen in the coals and their chars obtained from pyrolysis. The nitrogenous components in the product gases were analyzed by Fourier transform infrared (FT-IR) spectrometer. The results indicate that N-5 is the main nitrogen-bearing compound in DT coal and NM coal, whereas in FS coal N-6 is the main nitrogen-bearing compound. After pyrolysis at 600• C, the quantity of N-6 in the char rises for DT coal, and drops for NM coal and FS coal. After pyrolysis at 1000• C, the quantity of N-6 decreases significantly for FS coal, and considerable quantity of N-Q is detected. NH 3 , HCN, and NO were identified among the gases resulting from pyrolysis, with the HCN and NO yields being lower than the NH 3 yields. In coal pyrolysis, the initial formation temperature of NH 3 is approximately the same as that of HCN. The temperatures are almost identical when the concentrations of NH 3 and HCN reach their maxima for DT coal and FS coal. The formation of HCN starts at a temperature of about 400• C, and below 700• C, considerable amounts of HCN and NH 3 are produced. The amount of nitrogen released increases with the temperature at which pyrolysis takes place, the maximum release rate being 81.28% at 1000• C. 

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Characterization of Toluene Insolubles from Low‐Temperature Coal Tar

Liu¹,

Liu²,

Sun³

et al. 2014

Energy Tech

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Hydrogenation has been investigated in recent years as a potential method for upgrading low‐temperature coal tar (LCT). LCT contains toluene insolubles (TIs) that can cause process problems by plugging hydrotreater feed filters and catalyst beds. In this study, TIs are separated from LCT, and the composition and structure are studied by using elemental analysis, scanning electron microscopy (SEM), Fourier‐transform infrared spectrometry (FTIR), X‐ray diffraction analyses (XRD), X‐ray photoelectron spectroscopy (XPS), and other techniques. Microscopic observations reveal TI particles to be small approximately 50 % of the particles have a diameter of <3 μm. TIs contain a high proportion of inorganic material, for example, quartz, aluminosilicate, and calcium. Evidence for aliphatic and aromatic species is demonstrated by FTIR and XPS analysis. Although LCT contains many complex aromatic compounds, TIs exhibit a lower degree of aromaticity. Sulfate salts are the main form of sulfur element, and the greatest amounts of nitrogen occur in TIs as pyridinic nitrogen (N‐6) and oxidized nitrogen (N‐X) species.

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Thermal Chemistry of Nitrogen in Kerogen and Low-Rank Coal

Cited by 79 publications

References 56 publications

Organic nitrogen chemistry during low-grade metamorphism

Organic nitrogen chemistry during low-grade metamorphism

Relationship between nitrogenous species in coals and volatile nitrogen‐containing yields during pyrolysis

Characterization of Toluene Insolubles from Low‐Temperature Coal Tar

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