Traditionally, diesel fuel injection equipment (FIE) has frequently relied on the diesel fuel to lubricate the moving parts. When ultra low sulphur diesel fuel was first introduced into some European markets in the early 1980's it rapidly became apparent that the process of removing the sulphur also removed other components that had bestowed the lubricating properties of the diesel fuel. Diesel fuel pump failures became prevalent. The fuel additive industry responded quickly and diesel fuel lubricity additives were introduced to the market. The fuel, additive and FIE industries expended much time and effort to develop test methods and standards to try and ensure this problem was not repeated. Despite this, there have recently been reports of fuel reaching the end user with lubricating performance below the accepted standards. Recent publications have also suggested that it is not uncommon for sodium hydroxide used in the fuel refining industry to be present in fuel entering the supply chain downstream of the refinery. Due to the chemical nature of some lubricity additives there is clearly the possibility of interaction.
This paper briefly reviews the need for diesel fuel lubricity improver additives, previous work on such additives and possible interactions. It then goes on to present new work performed to investigate how the presence of sodium compounds in the fuel may affect the performance of a range of lubricity additives of different chemistries. It shows that the presence of the sodium hydroxide can lead to reactions with and hence the depletion of certain types of lubricity additive. This could inevitably lead to reduced lubricity performance and fuels reaching the customer that do not meet specification.
