Upgrading of diesel fuels and mixtures of hydrocarbons by means of oxygen low pressure plasmas: a comparative study☆

The oxidation of n-heptane, 1-octene, toluene, cis-decahydronaphthalene, mixtures of them, 4-phenyl-1-butene, 1,2,3,4-tetrahydronaphthalene, and three commercial diesel fuels, all in the liquid phase, by means of low pressure high-voltage oxygen plasmas was studied. Oxygen pressure was 0.2 mbar, applied power was 35 watts and reaction times ranged from 1 min to 23 h. Both individually and forming part of mixtures, olefins were the most reactive with ground-state atomic oxygen, O(3P). Olefinic double bonds reacted ca. 150 times faster than C–H bonds. Products were: epoxides and aldehydes for olefins; alcohols and ketones for alkanes; phenols for aromatics. Addition of 4.7–7.8% wt of oxygen was achieved for the diesels, depending on the particular composition, those with higher content of olefins being favoured, followed by those with higher content of alkanes.