Pristane isomerization

Fig. 5. 33 Summary of phytol sedimentary diagenesis, showing pristane isomerization (phytane undergoes similar isomerization large arrows indicate biogenic inputs).

The analysis of Wyodak recycle solvent by SEC-GC-MS shows that certain distribution order exists for species in coal liquids with respect to their size and degree of isomerization. The alkanes increase in chain lengths without any appreciable degree of isomerization, except for some biological markers such as pristane and phytane. Phenols and aromatics vary in size and extent of isomerization which causes the liquid to contain a large number of species. 

The transformations reviewed in Section 5.5 are potential maturity indicators.The most useful reactions are those in which only one of the pair of components is present initially in immature sediments, so that the extent of the transformation can be attributed entirely to thermal maturation (the kinetics of the transformation are also simpler Box 5.4). Such reactions include isomerization of pristane at C-6 and C-10, of steranes at C-20 and of hopanes at C-22, and also the aromati-zation of C-ring monoaromatic steroidal hydrocarbons. A number of molecular maturity parameters are shown in Fig. 5.47, together with some bulk maturity measurements.The correlation of values is approximate and varies with the type of organic matter present, its potential for generating petroleum and its heating rate. 

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