Tribological behavior of diesel fuels and the effect of anti-wear additives

Petrodiesel fuels are complex mixtures whose composition differ from refinery to refinery and according to the type of crude oil processed. They are prepared by blending two types of streams viz. straight run distillate and distillates from upgrading of residues. In order to make diesel fuels to work over a wide variety of working conditions, its properties are fixed to a standard value, which may differ in different countries according to their climate conditions. Also, to reduce pollution, some rules and regulations have been framed so as to limit the amount of harmful components as sulfur, nitrogen in the fuel. Till 1990s, sulfur was accepted up to a maximum value of 500 ppm. But keeping the green environment in view, the regulations have been made more stringent and presently sulfur should not be present beyond 50 ppm or even less in some countries. So, it is required to be removed through different processes. But during those processes many components responsible for lubricity also get removed, leading to the breakdown of fuel distribution pump, engine failure, etc. So, the lubricity is required to be regained with the help of anti-wear additives. The paper reflects light on different types of bio as well as chemical anti-wear additives as lubricity enhancement in ULSD fuels, is still a challenging task for researchers. (C) 2012 Elsevier Ltd. All rights reserved.