Based on an in-house Couette wax deposition device

the effect of polyoctadecyl acrylate (POA) pour point depressant upon wax deposition formed by synthetic waxy oils was investigated. The macroscopic morphology

DSC test

HTGC and wax crystal microscopic observation of the outer deposit (away from the wax deposition barrel) and inner deposit (close to the wax deposition barrel) were analyzed. It was found that the addition of POA reduces the wax deposition rate

accelerates the aging rate of the wax deposit

and leads to the formation of heterogeneous wax deposition structure (wax content gradually increased from outer deposit to inner deposit) in a certain concentration range (50-200 μg·g-1)

while the structure of wax deposit became homogeneous when adding 400 μg·g-1 of POA. The critical carbon number (CCN) of the wax deposit of pure waxy oil is C24

but the CCN of the wax deposit formed by additive treated waxy oil rises to C25. In comparison with the outer-layer wax deposit

the contents of the n-alkanes with carbon number ≤ C24 in the inner-wax deposit are lower and the contents of the n-alkanes with carbon number ≥ C25 are higher. With the increase of POA content

the waxy morphology of the wax deposit is gradually changed from small needle-like wax crystals to big sheet-like wax crystals

and the structure becomes more compact.