A3.3 Homogeneous Catalysts
Homogeneous (the opposite of heterogeneous) means “in the same state.” Homogeneous catalysts are more difficult to separate from the products of a reaction.
Homogeneous catalysts work in a different way than heterogeneous catalysts. The reactants react with the catalyst to form a temporary activated complex or reaction intermediate. For example suppose we have a reaction:
R1+R2 P\textsf{R1}+\textsf{R2}\ \rightarrow \textsf{P}
Activation energy
E\textsf{E}
where
R1\textsf{R1}
and
R2\textsf{R2}
are Reactants,
P\textsf{P}
is the Product. The catalysed reaction occurs in two steps involving the catalyst,
C\textsf{C}
1. R1+CXActivation energy E1\textsf{1.}\ \textsf{R1}+\textsf{C} \rightarrow \textsf{X} \\ {\textsf{Activation energy E1}}
2. X+R2P+CActivation energy E2 - note the catalyst is recovered\textsf{2. } \textsf X+\textsf{R2} \rightarrow \textsf{P}+\textsf{C}\\ \textsf {Activation energy E2 - note the catalyst is recovered}
Figure 3.1 Homogenous catalysts
Both
E1\textsf{E1}
and
E2\textsf{E2}
are smaller than
E\textsf E
, so the reaction will be faster.
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