Thermal deactivation of heterogeneous catalysts. Part 2: The compensation effect and the Catalytic Paradox

Abstract

The interpretation of the term "compensation" obscures a logical contradiction, the catalytic paradox, which is caused by inconsistent validity ranges of the Arrhenius parameters, the preexponential factor and the activation energy. For this reason, a theory which contains the Arrhenius parameters cannot be established for the entire system (whole temperature range) on the basis of classical logic. Only the subsystems can be consistent and complete. One subsystem is the range of the topocatalytic concept which is relevant for thermal deactivation, thermal bistability and for all reactions with surface dependence of activity. The other is the range of the energetic concept which is preferred in fundamental research. In order to complete the subsystems, new consistent symbols are introduced. The change of particle size caused by thermal deactivation can result in four possible particle size effects, two of which have been discussed in the literature.

A new particle size effect

“…agreement no agreement A further aspect is the Arrhenius energy E (= activation energy) which is introduced for the comparison of the two phenomena. 3) Agreement exists between the theory of separable kinetics [2] and all the interpretations of P.S.E. and no P.S.E., see Eqs (1) and ( l l ) , because a constant E is assumed.…”

“…and no P.S.E., see Eqs (1) and ( l l ) , because a constant E is assumed. 4) There is no agreement between the theory of non-separable kinetics [2] or the isokinetic relationship (= compensation effect; this expression will not be used because it is a semantic paradox [2]) and the discussed P.S.E., including no P.S.E. All these facts are compiled in Table 2.…”

“…The Arrhenius energy E (= activation energy [2]) must necessarily be constant, a fact which is not explicitly clarified in the literature. Eq.…”

“…These considerations revealed four possible particle size effects, P.S.E. [2]. Two of these effects have not been mentioned in literature and are, therefore, examined in the following.…”

“…In fundamental research, the sintering effect serves in the investigation of particle s u e influence on catalytic activity [2]. These considerations revealed four possible particle size effects, P.S.E.…”