An Appropriate Kinetic Model for Well-Preserved Algal Kerogens

Abstract

While the broadness of the pyrolysis profile of most kerogens is described well by a parallel reaction model, the pyrolysis profile at a constant heating rate for certain well-preserved algal kerogens is narrower than can be described by a single first-order reaction. Further, these kerogens show an acceleratory period under isothermal conditions that is inconsistent with any parallel or nth-order reaction model. Three different models (serial, Bouster, and three-parameter) are tested against isothermal and nonisothermal pyrolysis data for a few samples, with the conclusion that the three-parameter model fits well and is the most stable and reliable. The three-parameter model reduces to a first-order model when the acceleration parameter is zero. The overall activation energy and frequency factor from this model are very close to those of the T max-shift method recommended earlier.

Modelling of pyrolysis and combustion of gluten–glycerol-based bioplastics

“…According to this, the reaction rate depends on both non-reacted and reacted fractions. In this work, a modified Prout-Tompkims differential equation, used by Burnham et al (1996), has been used to describe the evolution of the reaction conversion (a i ):…”

“…The factor s, usually assumed as 0.01 (Burnham et al, 1996), is a constant that assures coherent values for reaction rate when conversion is close to extreme values of 0 or 1. The kinetic constant (k i ) is expressed by the Arrhenius law [k i = k 0i exp(E i /RT)], where k 0i is the preexponential factor and E i the activation energy.…”

Thermogravimetric measurement of amorphous cellulose content in flax fibre and flax pulp

“…However, later it was demonstrated that also is useful to represent solid reaction controlled by a nucleation process. Equation 1 is a modification of the PT equation used by Burnham et al (1996) and Burnham (2000), where a represents the reaction conversion, k the kinetic constant (expressed according to the Arrhenius law k ¼ k 0 e À E RT ), n the reaction order, m the nucleation order, and s a constant (assumed as 0.01) that assures reasonable values for the reaction rate when the conversion is close to extreme values (0 and 1). This equation can be expressed in form of Eq.…”

Use and misuse of logistic equations for modeling chemical kinetics

“…where n is the traditional reaction order and m is a ''growth'' parameter than can be correlated with the growth dimensionality of the geometric JMAEK nucleationgrowth model [8,9], although the precise relationship is more complicated [10,11] and will not be detailed here.…”