Narrow range ethoxylate
Encyclopedia
Fatty alcohol polyglycol ethers with a narrow homolog distribution
Distribution function
In molecular kinetic theory in physics, a particle's distribution function is a function of seven variables, f, which gives the number of particles per unit volume in phase space. It is the number of particles per unit volume having approximately the velocity near the place and time...

, which are also known as narrow-range ethoxylates (NRE), are known nonionic surfactant
Surfactant
Surfactants are compounds that lower the surface tension of a liquid, the interfacial tension between two liquids, or that between a liquid and a solid...

s, which are industrially produced, for example, by addition of ethylene oxide
Ethylene oxide
Ethylene oxide, also called oxirane, is the organic compound with the formula . It is a cyclic ether. This means that it is composed of two alkyl groups attached to an oxygen atom in a cyclic shape . This colorless flammable gas with a faintly sweet odor is the simplest epoxide, a three-membered...

 onto fatty alcohols in the presence of suitable catalysts (layer compounds which have been calcined or hydrophobized with fatty acids). This process can also be carried out on a variety of other hydrophobes and using different alkoxylating compounds (e.g., propylene oxide
Propylene oxide
Propylene oxide is an organic compound with the molecular formula CH3CHCH2O. This colourless volatile liquid is produced on a large scale industrially, its major application being its use for the production of polyether polyols for use in making polyurethane plastics...

 and butylene oxide) by modifying the catalyst properties.

Example

An ethoxylation
Ethoxylation
Ethoxylation is an industrial process in which ethylene oxide is added to alcohols and phenols to give surfactants. The invention of the process is attributed to Schöller and Wittwer at I.G. Farben industrie.-Production:...

 reaction proceeds under an inert atmosphere with an amount of heat depending on the starting material. The reaction proceeds via the epoxide (in this case ethylene oxide
Ethylene oxide
Ethylene oxide, also called oxirane, is the organic compound with the formula . It is a cyclic ether. This means that it is composed of two alkyl groups attached to an oxygen atom in a cyclic shape . This colorless flammable gas with a faintly sweet odor is the simplest epoxide, a three-membered...

) ring opening and activation of the nucleophile
Nucleophile
A nucleophile is a species that donates an electron-pair to an electrophile to form a chemical bond in a reaction. All molecules or ions with a free pair of electrons can act as nucleophiles. Because nucleophiles donate electrons, they are by definition Lewis bases.Nucleophilic describes the...

, ring, or combination thereof via the catalyst.



With conventional catalysts (i.e. potassium hydroxide
Potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...

, sodium hydroxide, etc.) one obtains a distribution of ethoxymers. If one targets a 12 mole
Mole (unit)
The mole is a unit of measurement used in chemistry to express amounts of a chemical substance, defined as an amount of a substance that contains as many elementary entities as there are atoms in 12 grams of pure carbon-12 , the isotope of carbon with atomic weight 12. This corresponds to a value...

 ethoxylate with a conventional alkaline earth hydroxide , one could expect to get a broad range of ethoxylates with n being anywhere from 3 to 30 moles of EO. With narrow range catalysts a much tighter distribution can be obtained.

Narrow range surfactants like alcohol ethoxylates and propoxylates can be incorporated into alkyl ether sulfates or mixed with other anionic surfactants and exhibit beneficial properties such as reduced irritation to skin/eyes and lower free alcohol content.
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