DETERMINATION OF THE RELATIVE OXIDATIVE STABILITY OF PETROLEUM BITUMENS BY THERMOGRAVIMETRY

An isothermal thermogravimetric technique was used to determine the apparent activation energies (E(a)) for the oxidative degradation of petroleum bitumens produced from different crude sources and with different histories. The values of E(a) were found to be different for each bitumen. For a particular bitumen, E(a) was independent of temperature over the range studied (240-370-degrees-C), but increased with increasing fractional conversion (alpha). A good correlation at low-alpha was established between E(a) and the durability value for each bitumen. The durability value is a relative measure of oxidative stability derived from an oven aging procedure (100-degrees-C) which has been found to be useful in predicting actual sprayed bitumen seal lifetimes in the field.