Effects of Molecular Structures of Alkanes on Peroxide Formation and Cetane Number Improvement by Autoxidation

Abstract

Diesel fuels having poor ignition properties would induce problems such as diesel knock and engine starting problems in cold weather. Diesel fuels in such cases need to have improved ignition properties. The addition of cetane number improving agents to diesel fuels is one method to improve the ignition properties of diesel fuels. However, addition of cetane number improving agents is not always an economically practical solution to improve the ignition properties of diesel fuels. Our previous study showed that the cetane numbers of autoxidized fuels in which hydroperoxides were produced increased. It is important for the development of cetane number improving systems by autoxidation to investigate the effects of molecular structures of hydrocarbons on the formation of hydroperoxides and the cetane number improvement. In this study, effects of carbon numbers and branching of alkanes on the formation of hydroperoxides were investigated. As a result, smaller carbon numbers produced more hydroperoxides. Also, effects of the molecular structures of the hydrocarbons on cetane number improvement by produced hydroperoxides have been investigated. The result suggests that the hydroperoxide produced from alkanes having a lower carbon number increases cetane number more. Furthermore, polynuclear aromatic hydrocarbons such as naphthalene and 1-methyl naphthalene had inhibition effects on the hydroperoxide production by autoxidation. From above results, the autoxidation could be a good method for improving diesel fuels such as city diesel and kerosene having low aromatic compounds and low distillation ranges because these fuels have to add cetane number improving agents to increase its number.