3.9 Catalysis

Many reactions can be catalyzed (i.e. sped up; rate increased) by the addition of a catalyst. There is a huge body of work devoted to this. A catalyst is a substance that is added to a reaction and is not consumed by the reaction.

\[\mathrm{A} + \mathrm{B} + \mathrm{catalyst} \longrightarrow \mathrm{products} + \mathrm{catalyst}\]

Here we see a catalyst going into a reaction and coming back out. It would not be seen in a typical chemical equation since it would cancel out. The catalyst speeds up the reaction by lowering the energy of activation. Consider the reaction pathway given below.

Figure 3.27: A catalyzed reaction pathway

The uncatalyzed reaction pathway (black line) has a higher energy of activation than the catalyzed reaction pathway (red line). The catalyzed reaction is faster because the energy of activation is lowered.

There are many types of catalysts and they can be categorized in many different ways. For example, homogeneous catalysts are substances that adopt the same phase as the reactants whereas heterogeneous catalysts do not.

Catalysts allow us to facilitate the formation of products on a more convenient timescale, particularly for reactions that would be too slow without the presence of a catalyst.