Step by step modeling for thermal reactivities and chemical compositions of vacuum residues and their SFEF asphalts

In this paper, thermal conversions of 40 samples, including eight vacuum re sidues (six Chinese vacuum residues from Daqing, Dagang, Gudao, Shengli, Hu abei and Liaohe crudes, two from Oman and Saudi Arabia Light crudes) and th eir deoiled asphalts with different yields obtained by supercritical fluid extraction fractionation (SFEF) technique were carried out in a 100-ml auto clave at 410 degrees C and 1 h. The elemental composition (C, H, S and N), SARA (saturates, aromatics, resins and asphaltenes) composition and average molecular weight (MW) of the feedstocks were determined, and their average structural parameters were elucidated. It is found that the cracking and c ondensation conversion of the samples were correlated with their H/C ratio, contents of sulfur (S%) and nitrogen (N%), MW, and SARA composition (weigh t percentages of saturates (Sat), aromatics (Ar), resins (Re) and asphalten es (Asp)). The results obtained by a non-linear regression fit method indic ated that the characterization factors K-r or K'(r) for thermal cracking de fined by following two equations: K-r = (H/C)(0.257) (S%)(0.158)(N%)(0.184)(MW)(-0.151) or: K'(r) = (Sat)(0.026)(AR)(0.008)(Re)(0.380)(S%)(0.170)(MW)(-0.230) can characterize well the thermal cracking reactivity of the eight vacuum r esidues and their SFEF asphalts at the 410 degrees C and 1 h. Moreover, the characterization factors K-c or K'(c) for thermal condensation defined by the following two equations: K-c = (H/C)(-3.80)(MW)(0.40) or: K'(c) =(H/C)(-3.80)(Re + Asp)(0.30)(MW)(0.24) can characterize well. the thermal condensation reactivity of most samples at the same reaction conditions. It is also found that the yields of toluen e insolubles of the feedstocks were correlated linearly with the concentrat ion ratio of asphaltenes to resins plus aromatics of the cracked residues. This indicates that the formation of coke was the result of not only the co ndensation reaction of asphaltenes but also the phase separation of the col loidal system of residues. (C) 1999 Elsevier Science B.V. All rights reserv ed.