Pyrolysis of petroleum residues: III. Kinetics of pyrolysis Original Research Article

The kinetics of mesophase formation for three petroleum residues of different aromaticities (R1, R2 and R3) have been followed by optical microscopy (anisotropic content ‘A’) and solvent extraction (insolubility in heptane (HI), toluene (TI) and 1-methyl-2-pyrrolidinone (NMPI)). Kinetics of mesophase formation followed as development of HI, TI, NMPI and ‘A’, approximate to apparent first order kinetics. Deviations from Arrhenius plots are observed. These could be caused by: a) depletion of reactants; b) effect of consecutive 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 270 kJ mol−1 and are a function of the experimental method (extraction with different solvents and optical microscopy). A consecutive reaction model has also been applied for R1 and R2 pyrolyses. Experimental values adjust reasonably to calculated values applying this method. Both R1 and R2 follow this model, with calculated activation energies of 240±20 kJ mol−1.