Determination of the Fate of Nitrogen Functionality in Carbonaceous Materials during Pyrolysis and Combustion Using X-ray Absorption Near Edge Structure Spectroscopy

Abstract

X-ray absorption near edge structure (XANES) was used to investigate the fate of nitrogen functional groups in carbons derived from acridine, carbazole, and polyacrylonitrile during carbonization. Acenaphthylene and poly(vinyldene chloride) carbons with nitrogen incorporation by ammonia treatment at elevated temperatures were also studied. In general, the nitrogen XANES data provided more detail than the corresponding X-ray photoelectron spectroscopy (XPS) results and confirm the overall picture obtained from XPS involving the greater stability of pyridinic and quaternary nitrogen functionalities with increasing severity of pyrolysis. Partial gasification of the carbons in 20% oxygen/argon produced a new peak or greatly increased the intensity of an existing nitrogen XANES peak at ∼401.5 eV which was independent of the nitrogen functionality originally present in the carbon. The oxygen XANES spectra showed that carbonyl and carboxylic acid/acid anhydride functionality were also present on the surface of carbons partially gasified with oxygen. The XANES studies have also been compared with the temperatureprogrammed combustion and temperature programmed desorption studies of the carbons. The results are consistent with the presence of pyridone functionality in the partially gasified carbons. The overlap of bands may obscure the interpretation of data from X-ray absorption spectroscopy, and information is required from a number of techniques in order to provide a more detailed view.

XPS determination of the forms of nitrogen in coal pyrolysis chars

“…3 Pyrolysis studies on model compounds indicated that under mild conditions pyrrolic nitrogen was converted into pyridinic nitrogen during condensation of the carbon matrix, and pyridones, protonated pyridinic nitrogen and pyridinic nitrogen oxides were also converted to pyridinic nitrogen. 4,14 In the condensation process, nitrogen is incorporated in the graphene sheets. It was concluded that under severe pyrolysis conditions (1 h at 1000°C) all nitrogen was present as either pyridinic nitrogen at the edge of the graphene sheets or as 'quaternary' nitrogen in the interior of these sheets.…”

Organic nitrogen chemistry during low-grade metamorphism

“…(i) Pyrrolic N atoms are bonded to one H atom and two C atoms in a non-aromatic or partially aromatic ring, with or without oxygen-containing substituents. (ii) Aromatic pyridinic rings contain N atoms in addition to oxygen-containing substituents (e.g., hydrated pyridinic rings, pyridone and pyridine carboxylic acids; defined by Mitra-Kirtley et al, 1993;Zhu et al, 1997;Vairavamurthy and Wang, 2002;Schnadt et al, 2003). Oxygencontaining substituents, such as hydroxyl groups, may provide chemically active sites for ring opening and subsequent elimination of N org (Katritzky et al, 1997;Siskin and Katritzky, 2000).…”

“…(iii) Amine and amide moieties may be present in less mature coals and kerogens (Kelemen et al, 2006). Within the accuracy of XPS measurements, pyridone nitrogen cannot be distinguished from pyrrolic nitrogen (Zhu et al, 1997). Similar to pyridinic nitrogen, these reactive nitrogen species are primarily located along the edge of condensed and partially aromatic systems.…”

Influence of carbon content and nitrogen vacancies on the bonding structure and mechanical performance of graphite-like BCxN thin films

“…%-i.e., BCN and BC 2 N compositions, respectively-is ascribed here to pyridone-like environments. 44 We observe that the N1s core-level edge of the BC x N-(a) coatings is comparable to h-BN for low C contents (10 at. %).…”