Oscillatory Adsorption as the Determinant of the Fluctuating Behaviour of Different Heterogeneous Systems

Abstract

Heterogeneous, catalytic oscillatory reactions as well as the oscillatory process of complex formation based on solid urea have been analysed in an attempt to ascertain the cause of such oscillatory mechanisms. In this context, oscillatory adsorption/desorption, phase transitions of the supported metal employed as the catalyst in the relevant oscillatory oxidation–reduction reactions as well as the reactions themselves have been considered. Based on an analysis of two oscillatory systems, of which one (i.e. the oscillatory alkylation of isobutane with butenes on a metal-free zeolite catalyst) is not complicated by any phase transitions, whilst the other (i.e. the oscillatory formation of an urea–octane complex via the interaction of urea with a binary vapour mixture of octane and non-complex-forming hydrocarbons) is not complicated by any chemical reactions, it is possible to infer that the source of the oscillatory properties of heterogeneous systems which involve the chemical interaction of their components is oscillatory adsorption which occurs as an uncomplicated self-supporting process which appears to proceed without any increase in the entropy of the system. The occurrence of oscillatory adsorption in a heterogeneous system leads to an oscillatory behaviour in the corresponding process, involving its simultaneous retardation in a similar manner as does the pendulum of a clock with respect to the untwisting of a spring or the oscillatory circuit of an electromagnetic system with respect to the discharge of a dry battery.