#jsDisabledContent { display:none; } My Account | Register | Help

Homogeneous catalyst

Article Id: WHEBN0005994878
Reproduction Date:

 Title: Homogeneous catalyst Author: World Heritage Encyclopedia Language: English Subject: Chelation Collection: Publisher: World Heritage Encyclopedia Publication Date:

Homogeneous catalyst

In chemistry, homogeneous catalysis is a sequence of reactions that involve a catalyst in the same phase as the reactants. Most commonly, a homogeneous catalyst is codissolved in a solvent with the reactants.

Examples

Acid catalysis

Main article: acid catalysis

The proton is the most pervasive homogeneous catalyst [1] because water is the most common solvent. Water forms protons by the process of self-ionization of water In an illustrative case, acids accelerate (catalyse) the hydrolysis of esters:

CH3CO2CH3 + H2O $\overrightarrow\left\{\leftarrow\right\}$ CH3CO2H + CH3OH

In the absence of acids, aqueous solutions of most esters do not hydrolyze at practical rates.

Organometallic chemistry

Processes that utilize soluble organometallic compounds as catalysts fall under the category of homogeneous catalysis, as opposed to processes that use bulk metal or metal on a solid support, which are examples of heterogeneous catalysis. Some well-known examples of homogeneous catalysis include hydroformylation and transfer hydrogenation, as well as certain kinds of Ziegler-Natta polymerization and hydrogenation.[2] Homogeneous catalysts has also been used in a variety of industrial processes such as the Wacker process Acetaldehyde (conversion of ethylene to acetaldehyde) as well as the Monsanto process and the Cativa process for the conversion of MeOH and CO to acetic acid.

Many non-organometallic complexes are also widely used in catalysis, e.g. for the production of terephthalic acid from xylene.

Other forms of homogeneous catalysis

Enzymes are homogeneous catalysts that are essential for life but are also harnessed for industrial processes. A well studied example carbonic anhydrase, which catalyzes the release of CO2 into the lungs from the blood stream.

Contrast with heterogeneous catalysis

Homogeneous catalysis differs from heterogeneous catalysis in that the catalyst is in a different phase than the reactants. One example of heterogeneous catalysis is the petrochemical alkylation process, where the liquid reactants are immiscible with a solution containing the catalyst. Heterogeneous catalysis offers the advantage that products are readily separated from the catalyst, and heterogeneous catalysts are often more stable and degrade much slower than homogeneous catalysts. However, heterogeneous catalysts are difficult to study, so their reaction mechanisms are often unknown.[3]

Enzymes possess properties of both homogeneous and heterogeneous catalysts. As such, they are usually regarded as a third, separate category of catalyst.

References

This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.

Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.