The distribution of nitrogen between bitumen, water and residue in hydrous pyrolysis of extracted Messel oil shale

Barth, Tanja; Rist, Kristin; Huseby, B.; Ocampo, R.

doi:10.1016/s0146-6380(96)00070-8

Cited by 13 publications

(24 citation statements)

References 22 publications

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“…At relatively low temperatures of 225 to 365 °C, hydrous pyrolysis experiments of an oil shale across the oil window to incipient gas generation (Lewan, 1985) released significant amounts of aqueous NH 4 + by decomposition of N org (Barth et al, 1996). Ammonia formation was found to be slow at relatively low temperatures during hydrous pyrolysis of sedimentary organic matter, but accelerated above a temperature threshold corresponding to natural anthracitization (You and Gieskes, 2001).…”

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

confidence: 99%

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

confidence: 99%

Organic nitrogen chemistry during low-grade metamorphism

Boudou

Schimmelmann

Ader

et al. 2008

Geochimica et Cosmochimica Acta

136

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“…The geological evolution pathways of nitrogen in sedimentary organic matter has been the subject of much recent discussion. [21][22][23][24][25][26][27][28][29][30][31][32][33] Insight into these processes comes from both low-temperature and hightemperature laboratory pyrolysis experiments that have monitored gaseous nitrogen-containing reaction prod- ucts. 21,22,27,28,[31][32][33][34][35] There have been few XPS and XANES studies of nitrogen forms in kerogen.…”

Section: Introductionmentioning

confidence: 99%

Thermal Chemistry of Nitrogen in Kerogen and Low-Rank Coal

et al. 1999

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X-ray photoelectron spectroscopy (XPS) was used to identify the forms of nitrogen present in Green River Type I and Bakken Type II kerogen concentrate samples and to follow the changes in nitrogen forms in the tars and chars produced upon pyrolysis. Pyrrolic nitrogen is the most abundant form of nitrogen, followed by pyridinic, amino, and quaternary types. XPS results show that upon devolatilization at 510 °C, the resultant kerogen tar and char contain mostly pyrrolic and pyridinic forms while amino groups are preferentially released into the tar. A portion of the quaternary nitrogen initially present in the Bakken kerogen appears in the 510 °C char and tar. Similar transformations were found for low-rank coal. These transformations occur at lower temperatures at long pyrolysis times for both kerogen and low-rank coal. Severe pyrolysis of the devolatilized kerogen char (T ) 630-810 °C) results in the appearance of an asymmetric carbon (1s) line shape indicative of very large polynuclear "graphitic-like" units. This transformation is accompanied by an increase in the relative abundance of quaternary nitrogen forms. Quaternary and pyridinic nitrogen forms become the dominant forms in severely pyrolyzed kerogen chars.

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“…In view of its stability field, the NH + 4 ion can be used as a pH-Eh marker: it is stable at low pH and Eh and therefore is commonly encountered in sedimentary basins. Due to both its organic origin (Boudou et al, 1984;Williams et al, 1989;Williams & Ferrell, 1991;Barth et al, 1996) and pH-Eh stability field (Grishina et al, 1998) analyses of NH + 4 ions play an important role in reconstructing the sedimentary, diagenetic and metamorphic evolution of rocks.…”

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confidence: 99%

Characterization of smectite and illite by FTIR spectroscopy of interlayer NH₄⁺ cations

et al. 2003

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FTIR spectroscopy has been applied to NH4+-exchanged dioctahedral clay minerals to determine the molecular environment of NH4+ and to quantify N concentration. FTIR under vapourpressure control, coupled with heating and freezing treatments has shown that NH4+ ion symmetry varies with the nature of clay minerals. NH4+ has a perfect tetrahedral symmetry in hydrated or dehydrated smectites and belongs to the Td symmetry group. The NH4+-bending vibration is centred at 1450 and 1425 cm–1.The Si4+-Al3+ substitution in dioctahedral clay minerals induces the loss of symmetry elements of the NH4+ tetrahedron which acquires a C2v symmetry. As a consequence, the Td –C2v transition can be used to characterize the smectite–illite transition. Quantification of NH4+ content per half unit cell is provided by nNH4 = k[NH4]/[OH] where [NH4]/[OH] is the band area ratio of the NH4+-bending vibration to the OH-stretching vibration. k = 1.1 for hydrated smectite, 0.9 for dehydrated smectite and 0.8 for illite or tobelite. The bending vibration of NH4+ is chosen for the calculation because it is not affected by superimposed contributions.

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The distribution of nitrogen between bitumen, water and residue in hydrous pyrolysis of extracted Messel oil shale

Cited by 13 publications

References 22 publications

Organic nitrogen chemistry during low-grade metamorphism

Organic nitrogen chemistry during low-grade metamorphism

Thermal Chemistry of Nitrogen in Kerogen and Low-Rank Coal

Characterization of smectite and illite by FTIR spectroscopy of interlayer NH₄⁺ cations

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The distribution of nitrogen between bitumen, water and residue in hydrous pyrolysis of extracted Messel oil shale

Cited by 13 publications

References 22 publications

Organic nitrogen chemistry during low-grade metamorphism

Organic nitrogen chemistry during low-grade metamorphism

Thermal Chemistry of Nitrogen in Kerogen and Low-Rank Coal

Characterization of smectite and illite by FTIR spectroscopy of interlayer NH4+ cations

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Characterization of smectite and illite by FTIR spectroscopy of interlayer NH₄⁺ cations