What is Catalysis?
Catalysis is the process of increasing the rate of a chemical reaction by adding a substance known as a
catalyst. The catalyst is not consumed in the reaction and can act repeatedly.
How Do Catalysts Work?
Catalysts work by providing an
alternative reaction pathway with lower activation energy compared to the non-catalyzed reaction. This is often achieved by the formation of intermediate species that facilitate the transformation of reactants to products.
What Are Catalytic Mechanisms?
Catalytic mechanisms describe the step-by-step process through which a catalyst facilitates a chemical reaction. These mechanisms often involve the formation and decomposition of intermediate species. Common mechanisms include:
Adsorption and Desorption
In
adsorption, reactants adhere to the surface of the catalyst, which can weaken certain bonds in the reactants, making them more reactive. After the reaction, the products are released from the surface in a process known as
desorption.
Formation of Intermediates
Many catalytic processes involve the formation of intermediate species. For example, in the
Haber process for ammonia synthesis, nitrogen and hydrogen gases adsorb onto the catalyst surface, forming intermediate species that eventually produce ammonia.
Enzyme Catalysis
Enzymes are biological catalysts that operate through highly specific mechanisms. They often employ a "lock and key" model or an "induced fit" model, where the
substrate binds to the
active site of the enzyme, forming an enzyme-substrate complex that facilitates the reaction.
Temperature: Higher temperatures can increase reaction rates but may also deactivate the catalyst.
Pressure: In gas-phase reactions, increasing pressure can drive the reaction forward.
Concentration of reactants: Higher concentrations generally increase reaction rates.
Surface area of the catalyst: Larger surface areas provide more active sites for the reaction.
Why Are Catalysts Important?
Catalysts are crucial in numerous industrial processes, from the production of
ammonia in fertilizers to the refinement of
crude oil into fuels. They enable processes that would otherwise be too slow or require too much energy, thus playing a critical role in chemical manufacturing, environmental protection, and even biological systems.
