Influence of polymers with surfactant properties as pour point depressants on the cold flow properties of diesel fuel

Abstract

Polymers and surfactants are increasingly applied to improve the cold flow properties of diesel fuel. However, their depressive effects are closely related to the molecular structure of the structuring units. In this study, the structural properties of surfactants were applied to synthesise a series of polymers consisting of tetradecyl methacrylate and ether compounds as structural units, with the long alkyl chain and ether compounds acting as hydrophobic and hydrophilic groups, respectively. The polymers consisting of tetradecyl methacrylate and ether compounds combined the advantages of polymers and surfactants in improving the cold flow properties of diesel. Besides, the effects of different functional groups, molar ratios and additive amounts on the improvement of diesel fuel low–temperature fluidity were investigated. The results indicated that 1500 ppm polymer with tetradecyl methacrylate and allyl glycidyl ether as structural monomers at a molar ratio of 6:1 as polymer pour point depressant (PPD) showed a greater enhancement of cold filter plugging point and solid point of diesel (ΔCFPP = 12 ℃, ΔSP = 17 ℃). The molecular structures of efficient pour point depressants were screened and the polymer composition was broadened. Finally, differential scanning calorimeter, rheological and polarising optical microscopy were used to analyse the changes in wax crystals size and morphology in pure diesel and diesel treated with polymer PPDs, and a mechanism for polymer PPDs with surfactant structural properties to change the crystallisation and aggregation behaviour of wax crystals was inferred.