This paper presents a method of exploring the kinetics of supercritical tert-butyl alcohol extraction of coal. Molecular weight distributions (MWDs) of extraction products of bituminous coal are interpreted with a model based on continuous-mixture kinetics. A continuous-flow reactor, in which supercritical tert-butyl alcohol contacts a differential bed of coal particles, provides sequential samples that are analyzed by HPLC gel permeation chromatography to obtain the time-dependent MWD data. The observed MWDs of the reaction products and their precursors in the coal macromolecular network are described by three gamma distributions. At temperatures below 360-degrees-C the MWDs maintain a similar shape during the semibatch extraction, indicating that the first-order rate constant is independent of molecular weight. The results of MWDs for runs with coal extract as feed provide experimental evidence that secondary reactions, such as repolymerization and cracking, are negligible at extraction conditions.