Modification effect of macroporous comb-like polymeric pour point depressants on the flow behavior of model waxy oils

Polyoctadecyl acrylate (POA) is a commonly used pour point depressant (PPD) for waxy crude oil, and its modification to further improve the fluidity of waxy crude oil is a hot research topic. In this paper, using the octadecyl acrylate (OA) as monomer and the divinylbenzene (DVB) as cross-linker, the macroporous polyoctadecyl acrylate (MP-POA) monoliths with a different cross-linking degrees were prepared by high internal phase emulsions template (HIPEs) method. After drying, the monoliths were ground into micron-scale MP-POA PPD and then characterized by FT-IR, SEM, BET, DSC, and XRD. The influence of the MP-POA PPD on the rheology of a model waxy oil was investigated through rheological tests, DSC analysis, and microscopic observation. The results showed that the crystallinity of MP-POA gradually deteriorated with increasing the cross-linking degree, while the rheological improving effect of the MP-POA first enhances and then reduces. We consider that the performance of the MP-POA PPD is influenced by two factors, that is, the crystallization ability and the nucleation template effect. With the increase of the cross-linker dosage, the crystallization ability of the MP-POA deteriorates, which will weaken the performance of the MP-POA PPD; meanwhile, the porosity of the MP-POA increases with increasing the cross-linking degree and then the waxy oil/MP-POA interfacial area increases, which will facilitate the nucleation template effect of the MP-POA PPD and then strengthen the performance of the MP-POA PPD. As a result, When the dosage of crosslinker was 0.5 wt%, MP-POA can best balance the crystallization ability and the nucleation template effect, resulting in the most excellent modification effect on the low-temperature rheology of model waxy oil, which further decreased its pour point by 3 °C and the yield value (10 °C) by 22.4 Pa. (compared with traditional POA).