Determination of selected hydrocarbon concentrations in reformate using near infrared spectroscopy

Near infrared spectroscopy was used as a quantitative technique employing multiple linear regression and partial least squares regression for determining the concentration of hydrocarbon groups and individual hydrocarbons present in reformate, a refinery process stream. Models were generated for total aromatics, benzene, toluene, total xylenes and individual xylene isomers, ethylbenzene, total paraffins, n-hexane, n-heptane, total isoparaffins, isopentane, 2-methylhexane, total naphthenes, methylcyclopentane, and total olefins. Some models are being used with an on-line instrument to constantly monitor a reformate stream as it leaves the reforming unit, with a standard error of performance of 0.118 volume percent for the prediction of the benzene concentration for a six month period. This technique serves as a faster method which takes less than a minute to perform the operation, whereas the primary methods of gas chromatography can take in excess of three hours to perform. By providing reliable data, this faster analysis can lead to enhanced economics concerning analysis time and can be used on-line for better control of a refinery process