The effect of paraffinic fractions on crude oil wax crystallization

The influence of the concentration and type of paraffinic crude oil components on the wax appearance temperature (WAT) was evaluated by means of Polarized Light Microscopy. High pour point waxy crudes were doped with paraffin distillation cuts, and changes on cloud points permitted to assess the inefficiency of a polymeric commercial paraffin inhibitor for crudes rich in heavy paraffins. An insensitive crude oil upon the addition of wax inhibitors was fractionated into its hydrocarbon type fractions. Light components were distilled out as the C-24-constituents. C-24+ cyclo/iso and linear paraffins were isolated from the distillation residue s saturates by means of 5 Angstrom molecular sieves adduction. The effect of virgin crude oil enrichment with the cyclo/isoparaffins fraction on its cloud point and a polymeric paraffin inhibitor efficiency were evaluated. These components have no significant impact on the inhibitors efficiency at concentrations below 40 wt%, but they increase the crude oil cloud point above 50 wt%, as a consequence of the higher average molecular weight introduced by these components. At this high concentration, a crystal modifier activity enhancement was observed, probably caused by steric hindrance of naphthenic and branched structures. The linear paraffin fraction with more than 24 carbon atoms (nC(24)+), also isolated from the virgin crud(: oil, was used for doping experiments on reconstituted crude samples, containing all the original components except this particular fraction. A direct dependence between the cloud point and the concentration of this fraction was assessed.