ASSIGNMENT OF AN AVERAGE CHEMICAL-STRUCTURE TO CATALYST CARBON DEPOSITS ON THE BASIS OF QUANTITATIVE C-13 NMR-SPECTRA

The quantitative MAS C-13 n.m.r. spectra of several catalyst carbon de posits (coke) were simulated using the LINESIM program. The aliphatic part of the coke spectra was simulated using Gaussian-Lorentzian (1/1) lines with linewidths of 80 to 150 Hz. The chemical shifts and linewi dths were chosen from the analysis of coked samples that had been expo sed to feed for a very short time (young cokes), with a resolved aliph atic spectral region. Otherwise, for coked samples exposed to feed for a very long time (old cokes), the spectrum consisted of two broad lin es: a major one for the aromatics and a minor one for the aliphatics. From the simulations it was possible to propose model molecular struct ures for the samples studied and draw conclusions on the activity of t he corresponding coked catalysts. Copyright (C) 1996 Elsevier Science Ltd.