NEW GROUP CONTRIBUTION METHOD FOR ESTIMATING AVERAGE BOILING POINT OF HEAVY OIL FRACTIONS
Heavy oil was separated into over dozen cuts under a lower temperature(250 ℃) to avoid thermal cracking by the supercritical fluid extraction and fractionation method (SFEF).The properties and 1H NMR, 13 C NMR spectra of the fractions were measured to determine their structure parameters and construct average molecular models.The boiling points of heavy oil fractions were measured up to 950 K.Based on Rarey’s group contribution model recently published, 12 groups were defined for heavy oil cuts.It was found that Rarey’s model was accurate for below C 50 fractions but show higher errors for heavier cuts.The dependence of boiling point on total atom number (except hydrogen) was refitted, while the value of the original group kept unchanged.Estimation for boiling point of two different residua from Russian crude oil and a mixed crude oil of Daqing(70% in mass) with Russian(30% in mass) was found with an average deviation 1 4% in the range of 600 K to 950 K.The T b prediction of normal alkanes from C 3 to C 120 was also found in good agreement with literature data.It verifies that the group definition and structure expression for heavy oil fractions are reliable.The group contribution method combined with SFEF can extend T b estimation up to 1050 K with carbon numbers over 100.