Pyrolysis of petroleum residues III. Kinetics of pyrolysis

The kinetics of mesophase formation for three petroleum residues of differe nt aromaticities (R1, R2 and R3) have been followed by optical microscopy ( anisotropic content 'A') and solvent extraction (insolubility in heptane (H I), toluene (TI) and 1-methyl-2-pyrrolidinone (NMPI)). Kinetics of mesophas e formation followed as development of HI, TI, NMPI and 'A', approximate to apparent first order kinetics. Deviations from Arrhenius plots are observe d. These could be caused by: a) depletion of reactants; b) effect of consec utive reactions, c) effect of reversible reactions, d) submicron mesophase in the isotropic phase and e) mesophase solubility. Activation energies for the three feedstocks are in close agreement. Values are between 160 and 27 0 kJ mol(-1) and are a function of the experimental method (extraction with different solvents and optical microscopy). A consecutive reaction model h as also been applied for R1 and R2 pyrolyses. Experimental values adjust re asonably to calculated values applying this method. Both R1 and R2 follow t his model. with calculated activation energies of 240+/-20 kJ mol(-1). (C) 2000 Elsevier Science Ltd. All rights reserved.