engleski

Analysis of olefine content in liquid FCC fractions by hyphenated NP-HPLC/DAD

Crude oil samples do not contain olefins, but as a result of fluid catalytic conversion (FCC) of atmospheric or vacuum residues a significant amount of olefines are present in FCC gasoline or light cyclic oil fractions. Both of these fractions are used for blending gasoline and diesel fuels. Knowledge of the composition of FCC gasoline and light cyclic oil is very important, especially the contents of olefines due to their influence on octane number1. Standard normal phase high performance liquid chromatography technique (NP HPLC) equipped with the refractive index detector (RID) and silica or slightly modified silica columns, used for group-type hydrocarbon determination of light and heavy oil fractions, is not suitable for olefine determination, due to co-elution of olefines with paraffins. There are two ways of improving determination of olefines - Using specially prepared stationary phases to obtain the required resolution between olefines and paraffins - Using an additional detector sensitive and selective to olefins but not to paraffins Diode array detector (DAD) is a common additional detector hyphenated to NP-HPLC. The goal of this work was to determine and quantify the amount of olefines in different FCC samples cut in narrow temperature fractions using the amino modified silica column and RI and DAD detectors. To monitor the change in resolution between olefines and aromatics, the flow rate of mobile phase as well as temperature have slightly changed. Increasing the temperature from 20o to 40o C and flow rate from 0.6 to 1.0 mL/min the resolution has slightly decreased. For quantitative determination of olefines we had to find the corresponding monitoring wavelengths to minimize absorption of mobile phase (n-heptane) and not correlating with the absorption maximum of aromatics. 2, 3-dimetil-1, 3-butadiene calibration curve as external standard was used for the determination of olefines content. The calculated content of olefins has decreased with increase of the prepared FCC fraction boiling point, and it is in accordance with the published results2.

olefine content determination; FCC fractions; Hyphenated NP-HPLC/DAD

nije evidentirano