Effect of ultrasonic field on isothermal kinetics of fullerene polyhydroxylation

Abstract

The isothermal kinetics of fullerene polyhydroxylation under ultrasonic field was investigated. The isothermal kinetic curves of fullerene polyhydroxylation at different temperatures ranging from 293 K to 313 K were determined. By application of the isoconversion method it was established that the reaction of fullerene polyhydroxylation with sodium hydroxide and cetyl trimethyl ammonium bromide as phase transfer catalyst was kinetically an elementary reaction. The model-fitting method confirmed that the kinetics model of first-order chemical reaction best described the kinetics of fullerene polyhydroxylation under ultrasonic field and the kinetics parameters of fullerene polyhydroxylation were determined (Ea,= 29 kJ/mol and lnA=9.4 min-1). It was established that the reaction rate of fullerene polyhydroxylation under ultrasonic field is higher from 1.5 times to 2.2 times than the rate of comparative reaction under the conventional heating. The activation energy is 28% lower than the value of activation energy determined under the conventional heating, whereas the value of pre-exponential factor is 40 times higher. The decreased value of activation energy (Ea,) and pre-exponential factor (lnA) in the ultrasonic field is explained with the increase in the value of ground energy level of the resonant vibration mode (ν = 500 cm-1) of C60 molecule (Ag(1) vibrational mode) and toluene molecule (out-of plane bending C-C-C vibration) and with the decreased value of anharmonicity factor.