THERMAL DECOMPOSITION OF SAUDI CRUDE OIL ASPHALTENES

Abstract

Abstract Asphaltenes precipitated by the use of pentane, heptane and decane solvents from Saudi Arabian Light (AL) and Saudi Arabian Heavy (AH) crude oils 370°C + residua have been investigated by thermal gravimetric analysis and pyrolysis - gas chromatographic analysis at 350°C and 520°C. Gas chromatographic analysis of the gases evolved during pyrolysis has shown that CO, CO2 and CH4 constitute the major portion of the gases evolved at 350°C from pentane and heptane asphaltenes of AH residue and from pentane asphaltenes of AL residue. Whereas gases evolved from decane asphaltenes are dominated by CO2 and C2-C4 hydrocarbon gases. At 520°C, hydrogen and methane represent 56-80 vol %of the gases evolved from all the four asphaltenes. The amounts of C1-C4 hydrocarbon gases increased with an increase in the carbon number of the precipitating solvent at 350°C and decreased at 520°C. The presence of up to C36 normal alkane hydrocarbon has been indicated in the maltenes produced from these asphaltenes. The loss of nitrogen from AH asphaltenes during pyrolysis remained low (1-6 wt %), whereas the losses of oxygen and sulphur ranged from 58 to 74 wt % and 10 to 29 wt %, respectively.