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Sulfur- and nitrogen-containing phenol-formaldehyde co-resites for probing the thermal behaviour of heteroatomic forms in solid fuels

Ismail, K. and Sirkecioglu, O. and Andresen, J.M. and Brown, S.D. and Hall, P.J. and Snape, Colin (1996) Sulfur- and nitrogen-containing phenol-formaldehyde co-resites for probing the thermal behaviour of heteroatomic forms in solid fuels. Polymer, 37 (18). pp. 4041-4048. ISSN 0032-3861

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Abstract

In order to probe the formation of sulfur- and nitrogen-containing gases during the pyrolysis and combustion of coals and other solid fuels, non-softening model substrates are required. In this respect, phenol-formaldehyde (PF) resins are ideal since they readily facilitate the incorporation of individual heteroatomic functions into a highly crosslinked matrix. A series of sulfur- and nitrogen-containing co-resites have been prepared using phenol with, as the second component, thiophene, dibenzothiophene, diphenylsulfide, benzyl phenyl sulfide, thioanisole, 8-hydroxyquinoline and 2-hydroxycarbazole. A mole ratio of 3 : 1 (phenol: heteroatom-containing component) was adopted in order to ensure that a reasonably high degree of crosslinking was achieved. Resoles containing diphenyldisulfide were also prepared but, due to the comparable bond strengths of the S-S and C-O linkages, a curing temperature of only 130 degrees C was used to avoid cleavage of the disulfide bond. The virtually complete elimination of ether and methylol functions from the resoles by curing at 200 degrees C was monitored by solid-state C-13 nuclear magnetic resonance (n.m.r.) spectroscopy. The resultant resites were also characterized by sulfur K-edge X-ray absorption near-edge structure (XANES.) spectroscopy, X-ray photoelectron spectroscopy (X.p.s.) and differential scanning calorimetry (d.s.c.). Simple air oxidation was found to selectively convert the aliphatic-bound sulfur to a mixture of sulfones and sulfoxides. Applications of the resites in fuel science are described.