A test of the parallel reaction model using kinetic measurements on hydrous pyrolysis residues

Abstract

Open-system kinetics are measured on extracted residues from hydrous pyrolysis to test aspects of the parallel reaction model and the assumption of a single frequency factor for all energies. The absolute rates of the residues form a series supporting the concept that hydrous pyrolysis removes primarily the more reactive components at lower temperature. The parallel reaction model works well for the marine kerogen, except for the small amount of refractory material in the highest temperature residue that is not represented adequately in kinetics from the initial sample because of measurement limitations. The kinetic parameters derived from the unreacted coal do not work as well and predict too much remaining reactive material. The discrepancy may be caused by a weakness in the parallel reaction model, or due to the fact that the open-system kinetics are not intended to predict the generation and subsequent removal of extractable organic matter. That the parallel reaction model works less well for coal confirms earlier concerns about the complexity of oxygen-related reactions. The constant frequency factor approximation works fairly well for the kerogen but marginally well for the coal. The frequency factor shifts about ten-fold over the activation energy range in the kerogen and about 100-fold over the activation energy range in the coals.