Color Change of Fused Polynuclear Aromatic Hydrocarbons in Toluene Induced by Sunlight Irradiation

Abstract

The behavior of color degradation of polynuclear aromatic hydrocarbons in toluene by sunlight was investigated at ambient temperature, using UV-vis, FT-IR, GPC and mass spectroscopy. Color of the solution containing three to five fused-ring aromatic hydrocarbons turned from pale yellow to dark brown and the amount of sediment formed increased with increasing sunlight irradiation. Contrary, no color degradation was observed in the solution of two fused-ring aromatics under the same conditions of irradiation. Additional charge of olefinic hydrocarbons to the solution of polynuclear aromatics did not give any significant effects on the behavior of color degradation. The color bodies formed from pyrene-toluene solution during irradiation comprised mainly oxidized pyrene and toluene with carbonyl, carboxyl, and hydroxy groups. The products of oxidation seem to combine with each other via chemical bonding including hydrogen bonds to form sediment.