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On the mechanism of catalysis induced by mechano-activation of solid body

Kulczycki A., Kajdas C.K., Liang H.

Materials Science Poland

2014

Vol. 32, No. 4

583--591

The paper presents a new model of the mechanism of mechanocatalysis and tribocatalysis. The reason for the increase in heterogeneous catalysis effect after mechanical activation of a catalyst has not been fully understood yet. There is no known theory, which would explain the mechanism of the influence of mechanical energy introduced to catalyst particles on the rate of chemical reaction. All existing theories are based on Arrhenius equation and assume that catalysts increase reaction rate due to decreasing of activation energy Ea. We hypothesize that both for standard and catalyzed heterogeneous reactions the same Ea (real activation energy) is needed to trigger the reaction processes and the catalytic effect is the result of energy introduced to the reaction system, its accumulation by a catalyst and then emission of high flux of energy to the space near the catalyst particles. This energy emitted by molecules of reagents can reach a value equal to the value of Ea at lower ambient temperature than it would result from Arrhenius equation. This hypothesis is based on αi model described in previous papers by Kajdas and Kulczycki as well as the results of tribochemical research described by Hong Liang et al., which demonstrate that the reaction rate is higher than that resulting from temperature.

A new idea of the influence of solid materials on kinetics of chemical reactions

Kajdas C.K., Kulczycki A.

Materials Science Poland

2008

Vol. 26, No. 3

787--796

The mechanism of heterogeneous catalysis is still under discussion. There is no clear theory which explains the mechanism of influence of materials on the rate of chemical reactions. All existing theories assume that specific materials, catalysts, decrease activation energy Ea. We hypothesize that for standard and catalyzed heterogeneous reactions the same Ea (real activation energy) is needed to trigger reaction processes. We propose that the difference between Ea and apparent activation energy (Eapp) can be presented as catalytic reaction activation energy (Ec). This hypothesis is based on the so-called α model considering tribochemistry, work function, thermionic emission, and the negative ion–radical action mechanism. The proposed model assumes that mechanical work done on a solid material is accumulated in this material and then emitted as electrons and/or photons to the space in which the reaction takes place. The developed model includes a specific angle γ at which the reaction can be initiated, when the stream of energy eγ equals some 3–5 eV. Energy emitted by the surface as pulses of 3–5 eV can reach the value of Ea and trigger a heterogeneous catalytic process. The catalyst emits pulses of a high density energy flux and at the angle γ the value of emitted energy is equal to the real activation energy Ea.