The Size Dependences of Kinetic Parameters of a Nanoparticle Reaction in Theory and Experiment

摘要

There is marked effect of particle size of a reactant on the kinetic parameters in a heterogeneous reaction. Nevertheless the regularity and essence of effect of particle size on the kinetic parameters have not been understood completely. In this paper, the nanokinetic theory for nanoparticles reactions was advanced, the relations between kinetic parameters and particle size were derived theoretically, and influence essence of particle size on the kinetic parameters was discussed. Besides, using the reaction of nano-magnesium oxide with sodium bisulfate solution as heterogeneous reaction system, the kinetics parameters for nano-magnesium oxide with different particle sizes were determinated in the experiment, and the regularities of effects of particle size on the kinetic parameters were obtained. The results of the experiment and reported literatures are consistent with the nanokinetic theory. The theoretical and experimental results show that the kinetic parameters are markedly influenced by particle size; with the decrease of the particle size, the apparent activation energy and pre-exponential factor decrease, and rate constant and reaction order increase; logarithm of the reaction rate constant, apparent activation energy and logarithm of pre-exponential factor have corresponding linear relations with the reciprocal of particle size, respectively; and the essences of the effect of particle size on kinetic parameters: the apparent activation energy is influenced by the molar surface energy of nano-reactant, reaction order by the molar surface area, pre-exponential factor by the mole surface entropy, and reaction rate by both the molar surface energy and the mole surface entropy.