Ce. Snape et al., CHARACTERIZATION OF COKE FROM FCC REFINERY CATALYSTS BY QUANTITATIVE SOLID-STATE C-13 NMR, Applied catalysis. A, General, 129(1), 1995, pp. 125-132
Coke has been concentrated from two deactivated FCC refinery catalysts
via demineralisation to facilitate detailed characterisation by solid
state C-13 NMR, The catalysts were obtained from runs with a residue
feed (5% Conradson carbon) and a hydrotreated vacuum gas oil (HVGO). A
s for solid fuels, the use of a low-field spectrometer in conjunction
with the single pulse excitation (SPE or Bloch decay) technique has en
abled quantitative carbon skeletal parameters to be obtained for the c
okes, Internal standard measurements demonstrated that most of the car
bon was observed by SPE and, therefore, NMR-invisible graphitic layers
are not thought to be major structural features of the cokes, SPE gav
e much higher values for both the carbon aromaticities and the proport
ions of non-protonated aromatic carbon than the less quantitatively re
liable cross-polarisation (CP) technique. Differences in feedstock com
position were reflected in the structure of the cokes with the aromati
c nuclei being more highly condensed in the residue-derived coke and c
orresponding to 15-20 pericondensed aromatic rings.