HYDROCARBON GROUP (PONA) ANALYSIS OF REFORMATE BY FT-IR SPECTROSCOPY

Multicolumn valve-switching gas chromatography is commonly used in ref ineries for determining paraffins, olefins, naphthenes and aromatics ( PONA) contents of reformate and naphtha samples. A simplified and fast alternative method, Fourier transform infrared (FT-i.r.) spectroscopy , for the same purpose was successfully used in the present work. In t his method, a calibration technique which took both spectral and conce ntration data into consideration was developed by using the instrument manufacturer's software utilizing partial least-squares (PLS) regress ion analysis. For this, the mid-i.r. range (4000-400 cm(-1)) was subdi vided into four regions that are usually attributed to different funct ional groups. An excellent correlation between the FT-i.r. and g.c. re sults was found, particularly for paraffins and aromatics (R(2) = 0.97 and 0.96 respectively). The average absolute differences between the results obtained from FT-i.r. and g.c. were 1.3, 0.5, 0.2 and 0.9 vol. % for paraffins, olefins, naphthenes and aromatics respectively. Copyr ight (C) 1996 Elsevier Science Ltd.