CHARACTERIZATION OF COKE FROM FCC REFINERY CATALYSTS BY QUANTITATIVE SOLID-STATE C-13 NMR

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.