Catalysts

A catalyst is something that makes a chemical reaction go more rapidly. In the body, enzymes are the most common catalysts; they are the protein molecules that specifically speed up certain chemical reactions. For example, ptyalin in saliva facilitates the breakdown of starch into simple sugars, which is why bread tastes sweet if you hold it in your mouth for a while. In the fields of preparative synthetic chemistry and chemical engineering, catalysis is one of the greatest economic contributors because it can be used for applications such as oil refining. Starting with crude oil, catalysts are used to make gasoline and jet fuel and various hydrocarbon molecules, which in turn can be used to make plastics and petrochemicals.

One approach to increasing chemical reactivity is to take advantage of the fact that reactivity is related to surface area. If something has more surface area, there are more places for other chemical agents to bind, interact, and react. As particle size decreases, surface area increases, assuming the total mass of the material stays the same, just as in our cube of gold from Chapter 2. Therefore, as their particle size drops into the nanoscale, materials have the maximum possible surface area and therefore the maximum possible reactivity, which is the aim of a catalyst. This approach is used by companies such as Nanomat, which make materials with nanoscale grains for industrial applications.