THERMALLY INDUCED PHASE-TRANSITIONS IN PETROLEUM WAXES FROM SOME TYPICAL INDIAN CRUDE OILS

Abstract

ABSTRACT Waxes from vacuum gas oil range fractions of three crude oils having different geological origin, viz, Neelam (a Bombay High settaliite well), Rava (Godawari basin )and Assam (Mix)crude oils, have been separated and their physco-chemical characteristics have been studied. The phase transitions in these waxes have been investigated using a differential scanning calorimeter and the needle penetration ( hardness ) is measured by following the ASTM procedure It is observed that the solid-solid phase transition in these waxes, on which depended their solubility, is governed by the melting point. Lower melting waxes ( mp < 47°C) have normally shown multiple solid-solid transitions whereas waxes with melting points lying between 47 - 70°C have at least one solid-solid transition. Waxes melting above 70°C did not show any solid-solid transition. Moreover, waxes belonging to the same boiling range from the three crude oils did not show any significant difference in the phase-transitional characteristics The hardness of the wax and its temperature dependence has also been found to be governed by the phase transition phenomenon and the dependence of the needle penetration on temperature has been explained on the basis or an analytical equation derived in terms of phase transitional parameters An analytical expression has also been derived between the phase transitional temperature and the molecular weight of the wax which may prove quite useful in estimating the limiting temperature upto which the wax can retain its hardness.