Synthesis and performance of maleic anhydride copolymers with alkyl linoleate or tetra-esters as pour point depressants for waxy crude oil

The low-temperature flow properties of waxy crude oils are considered the determining factor in the pipeline transportation. Such properties are highly affected by the content, composition and structure of wax. Polymeric additives known as pour point depressants (PPDs) have been developed to control the growth habits of wax crystals to improve the cold flowability of waxy crude oils. The present study aimed to synthesize comb-shaped polymeric additives based on poly (alkyl ester of malenized linoleic acid) to lower the pour point of Egyptian waxy crude oil and study its impact on the growth of wax crystals. Such PPDs were first prepared by free radical polymerization of maleic anhydride with alkyl linoleate. The resultant copolymer was then esterified with fatty alcohol. These obtained polymeric derivatives were characterized by 1H NMR, FTIR and Raman scattering spectral analyses. The crystallization behavior of paraffin wax was investigated by differential scanning calorimetry (DSC), X-ray diffractometry (XRD), photomicrography and scanning electron microscopy (SEM). The findings of these analyses showed that both of poly (alkyl linoleate-co-succinic anhydride) and poly (alkyl linoleate-co-tetra-esters) lower the crystallization temperature and enthalpies of paraffin wax, whereas photographs and SEM micrographs revealed that treating waxy oils with these pre-prepared polymeric additives led to suppress formation of the paraffin crystallites, and thus reduce the paraffin crystal size. Pour point measurements exhibited that the maximum pour point depression (ΔPP = 18 °C) was obtained by using poly (alkyl linoleate-co-tetra-esters) at dose of 3000 ppm.