The composition of gas oil stocks, either virgin, catalytically cracked, or a blend of both, can be characterized by a combination of analytical techniques. A hydrocarbon type analysis of the saturates, normal and isoparaffins, and of cycloparaffins and aromatics by detailed ring structure provides sufficient data to permit the engineer to correlate feed compositions with coke producing properties and product distributions for catalytic cracking operations. A polynuclear aromatic type ultraviolet analysis is obtained from the total sample, while another portion of the sample is separated into saturate and aromatic fractions by a liquid chromatographic procedure. Mass spectrometer analysis on each fraction coupled with the uv analysis and a molecular sieve separation on the saturate fraction for percent n-paraffins allow a complete hydrocarbon type distribution. In the case of catalytically cracked stocks, sulfur compounds present contribute to the uv spectrum. To correct the uv spectrum for their effects, a sulfur determination by either combustion or × ray is necessary. Weight percent polynuclear aromatics can be obtained solely from the uv analysis with the aid of boiling point and molecular weight correlations.
M. E. Fitzgerald, J. L. Moirano, H. Morgan, and V. A. Cirillo, "Characterization of Gas Oil Stocks: An Integrated Analysis," Appl. Spectrosc. 24, 106-114 (1970)