Catalyzed

Catalysis is a process in which the rate of a chemical reaction is increased by a substance known as a catalyst. Unlike other reactants in the chemical reaction, a catalyst is not consumed by the reaction itself and can continue to act repeatedly. Because of this, only very small amounts of catalyst are required to alter the reaction rate in principle. Catalysts typically speed up reactions by reducing the activation energy or changing the reaction mechanism.

Types of Catalysis

Catalysis can be divided into two main types: homogeneous catalysis and heterogeneous catalysis. In homogeneous catalysis, the catalyst is in the same phase (solid, liquid, or gas) as the reactants, facilitating direct interaction at the molecular level. In contrast, in heterogeneous catalysis, the catalyst is in a different phase from the reactants, usually solid in a liquid or gas mixture, where the reaction occurs at the interface between phases.

Homogeneous Catalysis

In homogeneous catalysis, because the catalyst and reactants are in the same phase, the reactions tend to be faster and more selective. Examples include the acid-catalyzed esterification of carboxylic acids and the transition metal-catalyzed hydrogenation of alkenes.

Heterogeneous Catalysis

Heterogeneous catalysis is characterized by the catalyst being in a different phase than the reactants. This type of catalysis is prevalent in industry, especially in the production of chemicals and fuels. Examples include the catalytic cracking of crude oil and the Haber-Bosch process for synthesizing ammonia.

Enzyme Catalysis

A special case of catalysis occurs in biological systems; this is known as enzyme catalysis. Enzymes are protein molecules that act as highly efficient catalysts for biochemical reactions. They are crucial for life, allowing complex biochemical reactions to occur under the mild conditions of temperature and pressure within living organisms.

Applications

Catalysis has a wide range of applications in both industrial and environmental processes. It is essential in the production of many chemicals, pharmaceuticals, and fuels. Catalysis is also critical in pollution control, such as in the catalytic converters used in automobiles to reduce exhaust emissions.

Catalyst Deactivation

Over time, catalysts can lose their effectiveness, a process known as deactivation. This can occur due to several reasons, including sintering, poisoning, fouling, and phase transformation. Catalyst regeneration or replacement is often necessary to maintain the efficiency of industrial processes.

See Also

• Chemical kinetics
• Surface science
• Biochemistry