In chemistry, a phase-transfer catalyst or PTC is a catalyst that facilitates the transition of a reactant from one phase into another phase where reaction occurs. Phase-transfer catalysis is a special form of catalysis and can act through homogeneous catalysis or heterogeneous catalysis methods depending on the catalyst used. Ionic reactants are often soluble in an aqueous phase but insoluble in an organic phase in the absence of the phase-transfer catalyst. The catalyst functions like a detergent for solubilizing the salts into the organic phase. Phase-transfer catalysis refers to the acceleration of the reaction upon the addition of the phase-transfer catalyst.
methyl)furan.Molecular_Catalysis_466_(2019)_112%E2%80%93121..jpg)
By using a PTC process, one can achieve faster reactions, obtain higher conversions or yields, make fewer byproducts, eliminate the need for expensive or dangerous solvents that will dissolve all the reactants in one phase, eliminate the need for expensive raw materials and/or minimize waste problems.[1] Phase-transfer catalysts are especially useful in green chemistry—by allowing the use of water, the need for organic solvents is reduced.[2][3]
Contrary to common perception, PTC is not limited to systems with hydrophilic and hydrophobic reactants. PTC is sometimes employed in liquid/solid and liquid/gas reactions. As the name implies, one or more of the reactants are transported into a second phase which contains both reactants.
Phase-boundary catalysis (PBC) is a type of heterogeneous catalytic system which facilitates the chemical reaction of a particular chemical component in an immiscible phase to react on a catalytic active site located at a phase boundary. The chemical component is soluble in one phase but insoluble in the other. The catalyst for PBC has been designed in which the external part of the zeolite is hydrophobic, internally it is usually hydrophilic, notwithstanding to polar nature of some reactants.[4][5][6][7][8] In this sense, the medium environment in this system is close to that of an enzyme. The major difference between this system and enzyme is lattice flexibility. The lattice of zeolite is rigid, whereas the enzyme is flexible.
- ^ Katole DO, Yadav GD. Process intensification and waste minimization using liquid-liquid-liquid triphase transfer catalysis for the synthesis of 2-((benzyloxy)methyl)furan. Molecular Catalysis 2019;466:112–21. https://doi.org/10.1016/j.mcat.2019.01.004
- ^ J. O. Metzger (1998). "Solvent-Free Organic Syntheses". Angewandte Chemie International Edition. 37 (21): 2975–2978. doi:10.1002/(SICI)1521-3773(19981116)37:21<2975::AID-ANIE2975>3.0.CO;2-A. PMID 29711128.
- ^ Mieczyslaw Makosza (2000). "Phase-transfer catalysis. A general green methodology in organic synthesis". Pure Appl. Chem. 72 (7): 1399–1403. doi:10.1351/pac200072071399.
- ^ H. Nur, S. Ikeda and B. Ohtani, Phase-boundary catalysis: a new approach in alkene epoxidation with hydrogen peroxide by zeolite loaded with alkylsilane-covered titanium oxide, Chemical Communications, 2000, 2235 – 2236. Abstract
- ^ H. Nur, S. Ikeda and B. Ohtani, Phase-boundary catalysis of alkene epoxidation with aqueous hydrogen peroxide using amphiphilic zeolite particles loaded with titanium oxide, Journal of Catalysis, 2001, (204) 402 – 408. Abstract
- ^ S. Ikeda, H. Nur, T. Sawadaishi, K. Ijiro, M. Shimomura, B. Ohtani, Direct observation of bimodal amphiphilic surface structures of zeolite particles for a novel liquid-liquid phase boundary catalysis, Langmuir, 2001, (17) 7976 – 7979. doi:10.1021/la011088c
- ^ H. Nur, S. Ikeda and B. Ohtani, Phase-boundary catalysts for acid-catalyzed reactions: the role of bimodal amphiphilic structure and location of active sites, Journal of Brazilian Chemical Society, 2004, (15) 719–724 – 2236. Paper
- ^ H. Nur, S. Ikeda, and B. Ohtani, Amphiphilic NaY zeolite particles loaded with niobic acid: Materials with applications for catalysis in immiscible liquid-liquid system, Reaction Kinetics and Catalysis Letters[dead link], 2004, (17) 255 – 261. Abstract