Thermal chemistry of nitrogen in kerogen and low-rank coal

Citation
Sr. Kelemen et al., Thermal chemistry of nitrogen in kerogen and low-rank coal, ENERG FUEL, 13(2), 1999, pp. 529-538
Citations number
63
Categorie Soggetti
Environmental Engineering & Energy
Journal title
ENERGY & FUELS
ISSN journal
08870624 → ACNP
Volume
13
Issue
2
Year of publication
1999
Pages
529 - 538
Database
ISI
SICI code
0887-0624(199903/04)13:2<529:TCONIK>2.0.ZU;2-3
Abstract
X-ray photoelectron spectroscopy (XPS) was used to identify the forms of ni trogen 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 nit rogen, followed by pyridinic, amino, and quaternary types. XPS results show that upon devolatilization at 510 degrees C, the resultant kerogen tar and char contain mostly pyrrolic and pyridinic forms while amino groups are pr eferentially released into the tar. A portion of the quaternary nitrogen in itially present in the Bakken kerogen appears in the 510 degrees C char and tar. Similar transformations were found for low-rank coal. These transform ations 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 degrees C) results in the appearance of an asymmetric carbon (Is) line shape indicative of very large polynuclear "graphitic-like" units. Thi s 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.