Pour point depressant efficacy for diesel fuels with different n-paraffin distribution

The use of diesel fuel in northern climates requires improvement of its cold flow properties, most often polymeric pour point depressants based on copolymers of alpha-olefins or alkyl methacrylates are used for this purpose. One of the problems arising in this method of improving cold flow properties is the significant dependence of the effectiveness of the pour point depressants on the hydrocarbon composition of the fuel. In this work the effect of pour point depressants based on copolymers of ethylene with vinyl acetate and copolymers of alkyl methacrylates with benzyl methacrylate on cold flow properties of diesel fuels and fractions of different genesis was studied. It was found that the cold filtering point of fuels without additives is mainly influenced by the average mass length of n-paraffins, and the effectiveness of pour point depressants depends on the relative dispersion of n-paraffins − a parameter reflecting the uniformity of distribution of n-paraffins by lengths, the higher the relative dispersion of n-paraffins in the fuel, the stronger the reduction of the cold filtering plugging point of fuel when pour point depressants are introduced into it. This fact can be explained by more uniform crystal formation in fuels with high relative dispersion of n-paraffins, and as a consequence more effective adsorption of additive molecules, which inhibit crystal growth and improve the filterability and flowability of fuel at low temperature.