The influence of heavy linear alkanes concentration on the wax crystallizat
ion tendency or wax appearance temperature (WAT) of a paraffinic crude oil
and on a paraffin inhibitor effectiveness was evaluated by means of polariz
ed light microscopy. A crude oil insensitive to the addition of wax inhibit
ors was fractionated into its hydrocarbon class fractions. Virgin crude oil
distillation, deasphaltation of the 385 degrees C+ residue, HPLC separatio
n of the heavy saturated hydrocarbons, and molecular sieves adduction enabl
ed us to isolate the linear paraffins fraction with a carbon distribution o
f more than 24 atoms (nC24+- paraffins). A synthetic crude was prepared by
mixing all separated fractions, except nC24+ paraffins, and the effect of t
his fraction concentration was evaluated by its controlled addition to the
synthetic crude followed by cloud point measurements of all doped samples.
The influence of this hydrocarbon class family concentration on a maleic an
hydride copolymer derivative paraffin inhibitor (MAC) efficiency was also e
valuated in all doped synthetic crudes. Abundance of these large linear alk
anes increases the crude oil tendency to wax crystallization, a fact that w
as demonstrated by a linear correlation between the concentration of this h
ydrocarbon family and the crude oil cloud point. nC24+ paraffins proved to
be deleterious for the efficiency of the selected paraffin inhibitor, affor
ding an asymptotic curve which tends to a zero activity value at 30 wt % co
ncentration of this fraction. Additionally, it was demonstrated that the fl
occulated asphaltenes provide wax crystallization sites whose presence incr
eases the cloud point of the crude oil and also interferes with the crystal
inhibition mechanism.