How do heterolytic catalysts work?
What are catalysts? They are substances that speed up the rate of reaction by providing a favourable pathway, of lower activation energy, for the reaction to proceed. A heterogeneous catalyst is one that is of a different phase to the reactants. An example of this is Iron as a powdered solid in the Haber Process to manufacture gaseous ammonia (NH3) from gaseous N2 and H2. The reaction is: N2(g) + 3H2(g) <--> 2NH3 (g) How do they work? Partially filled d orbitals in Iron form weak covalent bonds with H2 and N2. The molecules are said to be adsorbed. This reduces the stability of the molecule which means less energy is required to break the N2 and H2 bonds to form the 3 N-H bonds in Ammonia. Ammonia molecules then desorb from the surface and the process can be repeated to catalyse the next set of N2 and H2 molecules.
