Use the Arrhenius equation to calculate the activation energy \( E_a \):
\[
\ln \left( \frac{k_2}{k_1} \right) = \frac{E_a}{R} \left( \frac{1}{T_1} - \frac{1}{T_2} \right)
\]
Substituting the given values, we find \( E_a = 54 \, \text{kJ/mol} \).
Final Answer:
\[
\boxed{54 \, \text{kJ/mol}}
\]