Reaction mechanism and kinetic study

Reaction mechanism and rate equations

For irreversible gas phase reaction , global rate for catalyst particles is expressed in terms of temperature and concentration of A in bulk gas stream which can be measured or specified directly. Global rates of catalytic reactions are usually expressed per unit mass of catalyst.

Power law model

For homogeneous reaction, power law form of rate equation is used where rate is function of concentration and rate is determined by fitting data to the equation to data. The exponents on the concentration is the apparent order of the reaction and ‘k' is the kinetic constant or reaction rate constant which is independent of concentration and depends on temperature.

For reactions A+B → C+D

Here α is the order with respect to A and β is the order with respect to B

This power law approach can also be used for solid catalytic reactions. This analysis is simple. The major disadvantage of this method is that it ignores all the factors associated with adsorption and reaction mechanism on surface of solid catalyst. Hence, power law kinetics fails to adequately describe any solid catalytic process and the rate equation derived from mechanistic model is more preferred. Power law kinetics is preferred as a mode of obtaining preliminary value of rate parameters for solid catalyzed reactions.