Catalysts are compounds that reduce the activation energy required for a reaction to reach a transition state in order to increase the reaction rate. Catalysts may be gases, liquids, or solids. They are not consumed or chemically altered permanently as part of the reaction process. Catalysts can be divided into two types according to whether the phases of catalyst and reactant are the same or not. Homogeneous catalysts (typically liquid or gas) are those which exist in the same phase as the reactants, while heterogeneous catalysts are not in the same phase as the reactants. Heterogeneous catalysts are generally solid compounds added to a mixture of liquid or gas reactions, and their ability to speed up reactions is related to collision theory. Heterogeneous catalysts can be separated directly from the reaction mixture, so they are easily and efficiently recycled. However, once the catalyst surface is completely saturated with reactant molecules, the reaction cannot proceed until the products leave the surface. This process limits the speed of the catalyzed reaction. Unlike heterogeneous catalysts, homogeneous catalysts are mixed into the reaction mixture, allowing a very high degree of interaction between catalysts and reactant molecules, but homogeneous catalysts are often difficult to recycle after the reaction is complete. Another advantage of homogeneous catalysts is that they allow an increase in reaction rate without increasing in temperature.
Other types of catalysts are electrocatalysts, photocatalysts, biocatalysts, etc. Electrocatalysts are a specific form of catalysts that participates in electrochemical reactions. Electrocatalysts may be heterogeneous (e.g., platinum nanoparticles) or homogeneous (e.g., coordination complexes or enzymes). Photocatalysts use light to alter the electronic state of the catalyst, which then promotes chemical reactions. Both organic molecules and transition metal complexes are used as photocatalysts successfully. Organic photocatalysts tend to suffer from faster degradation during photocatalysis, and thus transition metal complexes are favored if high turn-over numbers are sought.
Amerigo Scientific offers high-quality catalysts to meet the catalytic needs of different reactions such as cycloaddition, cross-coupling reactions, ligand intermediates, chiral reactions, and phase-transfer catalysis (PCT).