RAMAN SPECTROSCOPIC INVESTIGATION OF OLEFINS IN SATURATED HYDROCARBONS AND THE SELF-ADJUSTABLE CALIBRATION MODEL DEVELOPMENT

Abstract

Based on the systematized collection of the Raman spectra of about 40 monounsaturated olefins, spectral regularities and invariant relations were established that formed the basis of the method for determining total olefins (total unsaturation per 100 carbon atoms) and their main classes in solutions of saturated hydrocarbons. Self-adjusting of the model by calculating the proportion of spectrally unresolvable C=C components with the use of the intensity of conjugated methyl groups increased its accuracy. In terms of repeatability, speed and cost-effectiveness of the analysis, the Raman-method is superior to standard methods of gas and adsorption chromatography and other modern spectral-correlation methods. The accuracy and stability of the results repeatability is confirmed by more than annual series of parallel comparisons with the data of known method. It is shown that five types of olefins in paraffin model solutions are sufficient to construct calibration curves in units of the number of C=C-bonds per 100 carbon atoms. These units allow recalculating data to the iodine scale and unifying the calibration model for different fractions regardless of the length of the hydrocarbon chains. The Raman technique can be extended to analyze other mixtures of non-aromatic hydrocarbons and be used for remote control of processes via fiber optic cables in industrial production.