Impact of alkyl methacrylate–maleic anhydride–alkyl methacrylate terpolymers as cold flow improver on crystallization behavior of diesel fuel

Alkyl methacrylate–maleic anhydride–alkyl methacrylate terpolymers (MR1–MA–MR2) is one of the widely used cold flow improver. In order to develop more efficient MR1–MA–MR2, it is necessary to study the crystallization behavior of n-alkanes when adding MR1–MA–MR2 into diesel fuel. In this paper, MR1–MA–MR2 is prepared by the reaction of long-chain alkyl methacrylate (MR1), maleic anhydride (MA), and short alkyl methacrylate (MR2). The diesel fuel before and after adding MR1–MA–MR2 is in situ filtrated at its cold filter plugging point (CFPP) in a manual CFPP apparatus. Extensive measurements of composition variation of n-alkanes are done by gas chromatograph and the results are compared. The experimental results show that after adding MR1–MA–MR2, the concentration distribution of n-alkanes in the filtrate is wide and arranges from 8 to 26, and mainly centralizes from 10 to 19. For the precipitate, the concentration distribution of n-alkanes gets richer in the lighter n-alkanes and poorer in the heavier n-alkanes. The concentration distribution of n-alkanes in the crystal solid shows a decreasing trend, especially with high carbon number n-alkanes (heavier than C20). About 60–70% of the residual crystal solid is composed of non-paraffins such as isoparaffin, naphthene and other components. Crystallinities of n-alkanes show a slow decrease trend from C8 to C20. When the carbon number n-alkanes are heavier than C20, the crystallinities of n-alkanes begin to sharply reduce with an increase of carbon number. The largest decline of crystallinity is C26 n-alkane from 38.39% to 7.90%.