Formatin of oxygen structures by ozonation of carbonaceous materials prepared from cherry stones II. Kinetic study

摘要

In this second part, the kinetics of the ozonation process of a char prepared from cherry stones (CS) is investigated. The char was obtained by heat treatmetn of CS at 600deg C h in nitrogen. The effects of reactin time, partial presure of ozone, and mass transport phenomena on the foramtion of oxygen complexes are studied. The surfce chemistry of the samples was examined by FT-IR spectroscopy and the elemental chemical analysis was also determined for some samples. Results showed that the ozonation of the char led to oxygen chemisorption and to carbon gasification. The amount of oxygen compelxes formed in the chemisoption stage (i.e., OH group, C=O structures, and ether structures) was foudn to be very with relatively high concentrations of C=O groups and ether structures were prepared by applying high ozone doses, whereas the formation of OH groups was favored at low ozone contents. The particle size did not influence the surface chemistry of the ozonated products. Only when the gas flow rate was lower than 40 l h~(-1), restrictins to ozone mass transport developed. For kinetics of the char ozonation process, a mechanism based on the Langmuir-Hinselwood adsorption-desorption model was proposed, and the intrinsic reaction rates were calcualted as a function of ozoantion temperature. The activtion energy for the ozoantion stage of the char was equal to 41.6 kJ mol~(-1).