Degradation of petroleum diesel fuel accelerated by UV irradiation: the impact of ageing on chemical composition and selected physicochemical properties

The long-term chemical stability of diesel fuel during storage is one of the key factors, which enable the proper operation of the combustion engine and, therefore, may prolong its life. The progressive degradation of particular components of diesel can affect negatively their physicochemical parameters, what, in turn, entails the issues with regular work and performance of the engines and influences adversely the composition of the exhaust. Moreover, the ageing results in the formation of high molecular polymers that form troublesome sediments which cover the bottom of the container and disrupt the injection of the fuel to the combustion chamber. The present study was aimed to investigate the changes in the chemical composition of the conventional petroleum diesel fuel stored with unrestricted air access under UV irradiation (lambda = 254 nm). The changes in the chemical composition were determined by means of gas chromatography coupled to mass spectrometry. The changes in the crucial physicochemical parameters, namely: density, viscosity, flash point, cloud point, cetane number, cetane index, and distillation characteristic, caused by the photochemical degradation of diesel components, were discussed with regard to the changes in the molecular composition of diesel.