Compatibility and rheology of bio-oil blends with light and heavy crude oils

Abstract

The morphological features, thermophysical properties, and rheology of bio-oil in comparison with light and heavy crude oils have been studied and analyzed. It has been demonstrated that bio-oil is a water-in-oil emulsion, light crude oil is a suspension of paraffin waxes in oil medium, and heavy crude oil is a homogeneous liquid. All oil samples have low-temperature phase transitions, which are most likely associated with crystallization of saturated compounds included in their composition. As a result, light oil and bio-oil are viscoelastic fluids that have a yield stress at low temperatures but demonstrate a Newtonian or weakly expressed non-Newtonian behavior, respectively, when heated. Heavy crude oil is viscoelastic fluid over a wide temperature range with a viscosity that decreases slightly but only at high shear stresses. Binary blends of bio-oil with fossil oils were studied with the content of components from 20 to 80 wt%. All bio-oil/crude oil blends are emulsions, the type of which depends on the ratio of oils. Due to limited miscibility between hydrocarbons of fossil oils and the oil phase of bio-oil, macroscopically compatible blends are formed only when heavy crude oil is mixed with bio-oil at a low content of the latter. It is shown that mixing light crude oil with bio-oil is not rational in terms of improving rheology of any of these oils, while the combination of bio-oil with heavy crude oil can slightly reduce the viscosity of the latter.