Kinetics of heterogeneous reactions

Convection enhances mass transfer. The general convective diffusion equation is not trivial to solve and will be dealt with later. 

There are a variety of heterogeneous reactions. Most reactions encountered by geologists are heterogeneous reactions. The kinetic aspects of various heterogeneous reactions have been reviewed by a number of authors (Kirkpatrick, 1975, 1981 Berner, 1978). Heterogeneous reactions may be classified as at least three different types. 

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Intrinsic Kinetics of Heterogeneous Reactions Involving Solids 255... 

INTRINSIC KINETICS OF HETEROGENEOUS REACTIONS INVOLVING SOLIDS... 

The flow reactor is used primarily in the study of the kinetics of heterogeneous reactions. Planning of experiments and interpretation of data obtained in flow reactors are considered in later chapters. 

The mathematical difficulty increases from homogeneous reactions, to mass transfer, and to heterogeneous reactions. To quantify the kinetics of homogeneous reactions, ordinary differential equations must be solved. To quantify diffusion, the diffusion equation (a partial differential equation) must be solved. To quantify mass transport including both convection and diffusion, the combined equation of flow and diffusion (a more complicated partial differential equation than the simple diffusion equation) must be solved. To understand kinetics of heterogeneous reactions, the equations for mass or heat transfer must be solved under other constraints (such as interface equilibrium or reaction), often with very complicated boundary conditions because of many particles. 

Name some kinetic problems that you have already encountered or you may encounter in the future in your research. Then decide whether they belong to (i) kinetics of homogeneous reactions (ii) mass transfer, or (iii) kinetics of heterogeneous reactions (including phase transformation). 

In this chapter, the essential aspects of kinetics of heterogeneous reactions (nucleation, interface reaction, and mass/heat transfer) are first presented. Then one class of heterogeneous reactions, the dissolution and growth of crystals, bubbles, and droplets, is elaborated in great detail. Some other heterogeneous reactions are then discussed with examples. Many complex problems in heterogeneous reactions remain to be solved. 

The foregoing methods are certainly not exclusive, and many other techniques such as cloud chambers (e.g., see Miller et al., 1987) and fluidized bed reactors have also been applied to following the kinetics of heterogeneous reactions relevant to the atmosphere. However, due to space limitations, these will not be treated in detail here. 

KINETICS OF HETEROGENEOUS REACTIONS attached to the square root. It means simply a fractional power in the neighbourhood of 0-5. 

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