Influence of Resins on Crystallization and Gelation of Waxy Oils

In the present work, we employed model oil systems to examine the effects of resins upon the gelation and crystallization of waxy oils. Two types of waxes were explored, namely, n-tetracosane (wax A) and a commercial wax with a melting temperature of 52–54 °C (wax B). The resins were extracted from a deoiled asphalt from Venezuelan residue by the saturates, aromatics, resins, and asphaltenes fractionation method. The results from negative-ion electrospray ionization Fourier transform ion cyclotron resonance-mass spectrometry suggest that resins consist of one to four fused benzenes rings or one to two fused naphthalene rings constructed by N1, N1O1, N1S1, N1O1S1, N1O2, O1, O1S1, and O2 class species containing stacking aromatic rings. For both types of waxes examined, adding resins to the waxy oils suppresses wax precipitation and modifies the morphology of wax crystals, which collectively leads to lower gelation temperature and lower yield stress. Up to 7 °C of reduction in gelation temperature, 60% of reduction in yield stress, and 6 °C of reduction in wax appearance temperature were achieved when the waxy oils contain 7 wt % resins. Whereas for the wax A model oil, the gelation temperature decreases gradually with increasing resin content, for the wax B model oil, the resin effect is pronounced only at the resin concentration below 0.2 wt %. The reduction in yield stress caused by adding resins is also greater for the wax A model oil than wax B model oil. The different resin effects for the wax A model oil and wax B model oil might be caused by the compositional variations between wax A and wax B.