This paper reports a novel application of in-line, short wavelength, near infrared (SW-NIR) spectroscopy to monitor eight pilot scale reforming units, for real-time determination of research octane number (RON) and aromatic compositions (benzene, toluene, xylene and total aromatics) of reforming gasoline, by an on-line SW-NIR system constructed by ourselves. Robust partial least squares calibration models for sample composition and measurement conditions were built using a global calibration set including off-line and in-line samples. Prediction results of the global models, over a six month period, for the eight units show excellent correlation with the corresponding reference data. The spectral pretreatment method of mean sample residual spectrum correction was used to remove spectral difference among multi-channels caused by small coupling differences among fibres and the multiplexer in the analyser. The prediction statistics showed consistency among the eight channels without any systematic errors. The applications of the NIR analyser can rapidly reflect the state of the process at a given time without any operator intervention. Moreover, the high stability and ruggedness of the CCD array-based on-line instrumentation guarantees easy and reliable operation.

Keywords: near infrared, on-line process monitoring, partial least squares, pilot scale unit, reforming gasoline, research octane number, aromatic compositions