Multivariate determination of several compositional parameters related to the content of hydrocarbon in naphtha by MIR spectroscopy

Abstract

Several compositional parameters of the main hydrocarbon families are determined in naphtha. This hydrocarbon mixture is traditionally analysed by gas chromatography (GC) but there are several alternative spectroscopic methods, such as near-infrared spectroscopy combined with multivariate calibration. Spectroscopic methods have the advantage that they are faster and more suitable for on-line analysis. Previous studies have determined the global percentage of each hydrocarbon family: linear and branched paraffins, naphthenes and aromatic compounds. Here we present the determination by mid-infrared (MIR) spectroscopy and multivariate calibration of the most detailed compositional parameters provided by gas chromatography. Results were good, that is to say there was no bias and the root mean square error of cross validation (RMSECV) was low, for the determination of all the detailed naphthenes and aromatic compounds, and most n-paraffins and isoparaffins. Several methods of detecting outliers are discussed and the quality of the models is evaluated by sample specific error predictions calculated by two approaches: the Unscrambler expression and the Faber-Kowalski expression. The proposed method enables a more specific analysis of naphtha than other methods and provides the same information as GC.

Detection of Gas Concentration by Correlation Spectroscopy Using a Multi-Wavelength Fiber Laser

“…Instead of using some Priori method [10][11][12][13], we used a convenient and reliable signal processing method with the Unscrambler software [14][15][16] to exclude the disturbances and select the correlated pairs. Initially 1-3 correlated pairs were selected manually from the data in Fig.…”

“…A multi-wavelength fiber laser in the near-infrared with narrow spectral lines, which can be designed to match absorption lines of target gases well, is used to enhance the sensitivity and the selectivity, and the Unscrambler software [14][15][16] is applied to improve the efficiency of the signal processing. Furthermore, because of the wide wavelength tunable range of multi-wavelength fiber laser, the present technique can measure multi-gas simultaneously even if the absorption peaks of the gases are relatively far away from each other.…”

Predicting % of crystallinity in FCC catalysts by FT‐MIR and PLS

“…The application of quantitative chemometrics methods, particularly partial least squares (PLS) for multivariate chemical data, has been widespread in the petroleum laboratories [8,9]. Mid-infrared spectroscopy (FT-MIR) combined with PLS regression method have been extensively used in the analysis of physical and chemical properties of petrochemical products such as: gasoline, naphtha [8][9][10][11][12][13][14][15][16], kerosene, jet fuel [17][18][19][20][21], diesel [22,23], lubricants and oils [24,25].…”

Laboratory Quality Optical Analysis in Harsh Environments

“…For absorption spectroscopy, a wealth of fingerprint information may be derived in the near-and mid-infrared vibration absorption regions (Mattson et al 1977). Multiple authors (Mattson 1977, Khadmin 1999, Macho 1999, Kallevik 2000, Aske 2001, Aske 2002, Satya 2006) have used high-resolution dot product regression of high-resolution optical data to provide chemometric prediction of oil fractions and properties, including saturates, aromatics, resins, and asphaltenes fractions, density, and molecular weight. Relative model uncertainties are typically in the range of the range of 1 to 4%, depending on the study and parameter.…”

“…Studies have been conducted with dead oil, live oil, and dead oil reconstituted to live oil conditions. Macho et al (1999) showed that individual hydrocarbon molecules may be isolated by a chemometric dot product regression from C3 to C11 with a surprising degree of accuracy: 0.1 w% for C3 to 0.6 w% average for C6+, including resolution of branched, cyclic, and aromatic compounds. This degree of resolution approaches that of gas chromatography, which is often accepted as the laboratory gold standard with reported accuracies only 2 to 5 times greater.…”