Этилен оксиді мен субстраттың химиялық әрекеттесуі: өнеркәсіптік масштабтағы процесс

Chemical reaction between ethylene oxide and substrate
the industrial scale process

In organic chemistry, ethoxylation is a chemical reaction in which ethylene oxide (|C2H4O) adds to a substrate. It is the most widely practiced alkoxylation, which involves the addition of epoxides to substrates. In the usual application, alcohols and phenols are converted into |R(OC2H4) {n}OH, where n ranges from 1 to 10. Such compounds are called alcohol ethoxylates. Alcohol ethoxylates are often converted to related species called ethoxysulfates. Alcohol ethoxylates and ethoxysulfates are surfactants, used widely in cosmetic and other commercial products. The process is of great industrial significance, with more than 2,000,000 metric tons of various ethoxylates produced worldwide in 1994.

The process was developed at the Ludwigshafen laboratories of IG Farben by Conrad Schöller and during the 1930s.

Industrial ethoxylation is primarily performed upon alcohols. Lower alcohols react to give glycol ethers which are commonly used as solvents, while longer fatty alcohols are converted to fatty alcohol ethoxylates (FAE's), which are a common form of nonionic surfactant. The reaction typically proceeds by blowing ethylene oxide through the alcohol at 180 °C and under 1 2 bar of pressure, with potassium hydroxide (KOH) serving as a catalyst. The process is highly exothermic (ΔH =  92 kJ/mol of ethylene oxide reacted) and requires careful control to avoid a potentially disastrous thermal runaway. Typically 5 10 units of ethylene oxide are added to each alcohol, however ethoxylated alcohols can be more prone to ethoxylation than the starting alcohol, making the reaction difficult to control and leading to the formation of a product with varying repeat unit length (the value of n in the equation above). Better control can be afforded by the use of more sophisticated catalysts, which can be used to generate narrow range ethoxylates. Ethoxylated alcohols are considered to be a high production volume (HPV) chemical by the US EPA.

Although alcohols are by far the major substrate for ethoxylation, many nucleophiles are reactive toward ethylene oxide. Primary amines will react to give di chain materials such as polyethoxylated tallow amine. The reaction of ammonia produces important bulk chemicals such as ethanolamine, diethanolamine, and triethanolamine.

Alcohol ethoxylates (AE) and alcohol ethoxysulfates (AES) are surfactants found in products such as laundry detergents, surface cleaners, cosmetics, agricultural products, textiles, and paint.

As alcohol ethoxylate based surfactants are non ionic they typically require longer ethoxylate chains than their sulfonated analogues in order to be water soluble. Examples synthesized on an industrial scale include octyl phenol ethoxylate, polysorbate 80 and poloxamers. Ethoxylation is commonly practiced, albeit on a much smaller scale, in the biotechnology and pharmaceutical industries to increase water solubility and, in the case of pharmaceuticals, circulatory half life of non polar organic compounds. In this application, ethoxylation is known as "PEGylation" (polyethylene oxide is synonymous with polyethylene glycol, abbreviated as PEG). Carbon chain length is 8 18 while the ethoxylated chain is usually 3 to 12 ethylene oxides long in home products. They feature both lipophilic tails, indicated by the alkyl group abbreviation, R, and relatively polar headgroups, represented by the formula |R(OC2H4) {n}OH.

AES found in consumer products generally are linear alcohols, which could be mixtures of entirely linear alkyl chains or of both linear and mono branched alkyl chains. A high volume example of these is sodium laureth sulfate a foaming agent in shampoos and liquid soaps, as well as industrial detergents.

Alcohol ethoxylates are not observed to be mutagenic, carcinogenic, or skin sensitizers, nor cause reproductive or developmental effects. One byproduct of ethoxylation is 1,4 dioxane, a possible human carcinogen. Undiluted AEs can cause dermal or eye irritation. In aqueous solution, the level of irritation is dependent on the concentration. AEs are considered to have low to moderate toxicity for acute oral exposure, low acute dermal toxicity, and have mild irritation potential for skin and eyes at concentrations found in consumer products. The remaining AEs are treated at waste water treatment plants and biodegraded via aerobic processes with less than 0.8% of AEs released in effluent. The removal of AES due to degradation via anaerobic processes is estimated to be between 75 and 87%.

Flow through laboratory tests in a terminal pool of AES with mollusks found the NOEC of a snail, Goniobasis and the Asian clam, Corbicula to be greater than 730 ug/L. Corbicula growth was measured to be affected at a concentration of 75 ug/L. The mayfly, genus Tricorythodes has a normalized density NOEC value of 190 ug/L.

AES has not been found to be genotoxic, mutagenic, or carcinogenic.