ABSTRACT
Graphite (Bacon, 1950) is a single crystal produced by natural heating (geothermal gradient) applied to carbonaceous rocks already strained by tectonic stresses: stress graphitization (Bonijoly et al., 1982). Less crystallized “graphite” is obtained by pyrolysis of suitable organic matters under an inert gas flow, up to about 3000°C. Natural heating without stresses (coalification) only produces almost pure carbon (Bonijoly et al., 1982). The corresponding laboratory process (HTT < 2000° C) is carbonization. In a first approximation both processes are equivalent. Any organic matter being made of C, H, O, N, S, it provides pure carbon by heteroatom release. Carbon precursors are thus organic sediments such as coals (van Krevelen, 1993) or kerogens (parent rocks of oil) (Durand, 1980), their derivatives such as oils, tars, heavy oil residues, pitches, or compounds like cellulose, anthracene, organic polymers, etc... Carbonization and coalification as well are thermally activated processes (Fitzer et al., 1971) following kinetics laws. Pressure and residence time (also heating rate) must be fixed in addition to HTT.
