Formation of oxygen complexes by ozonation of carbonaceous materials prepared from cherry stones: I. Thermal effects Original Research Article

In this study, the feasible use of ozone to form oxygen complexes in chars prepared from cherry stones (CS) is investigated. CS were charred at 450, 600 or 900°C for 2 h in nitrogen. Char samples were ozonated over the 25–250°C temperature range for 1 h. Elemental chemical analysis was effected for a few selected samples. The oxygen complexes were successfully analyzed by Fourier infrared spectroscopy (FT-IR) and by titration methods. Thermal decomposition of ozone in the gas stream was also studied and the mechanism of the ozonation process dealt with. The ozonation treatment of CS chars was found to yield products with a relatively high concentration of a number of oxygen complexes. These include phenolic hydroxyl, quinonic, carboxylic acid, and ether structures. The content of lactonic structures was very low in the ozonated samples. The type and quantity of oxygen complexes depended on the ozonation and charring temperatures. The formation of oxygen complexes was favored when the charring of CS was effected at 450°C and when the ozonation of the char prepared at 600°C was performed at 100°C. The ozone content in the gas stream was very sensitive to the temperature increase in the reactor. Several reaction routes have been proposed for the transformation of ether, aromatic, and olefinic structures present in CS chars into oxygen complexes.