Antagonism between cloud point and cold filter plugging point depressants in a diesel fuel

Differential scanning calorimetry (d.s.c.) and thermomicroscopy were used to provide a better understanding of the antagonistic effect on cold filter plugging point (CFPP) when cloud point depressants (CPD) and CFPP additives are mixed into a diesel fuel. It is shown that the CFPP achieved by using only CFPP additive can be attained in the presence of CPD if a small, homogeneous size of crystals of paraffins is again obtained. Two ways are proposed to obtain this result: modification of the chemical structure of the CPD, and optimization of the concentration of each component of the blend. In either case a decrease in efficiency of the CPD is observed, but the antagonism disappears. It is possible to predict the efficiency of CFPP additives in a diesel fuel containing CPD by evaluation of T_g of the hydrocarbon matrix and determination of the percentage of light n-alkanes by d.s.c.