Patent GB-1067721-A (GB)
Title: Preparation of trialkyl phosphites
Inventor: SCHULZ ARTHUR CHARLES
IPC: C07F9/142
Filed: 1964-05-07
Abstract: A trialkyl phosphite wherein the alkyl groups have from 2 to 10 carbon atoms, is obtained by reacting an aryl phosphite of the formula P(OR)3, where R is a C2-C10 alkyl radical or an aryl radical, at least one of the OR groups being an oxyaryl with a C2 to C10 alkanol in the presence of a transesterification catalyst, to produce a transesterification reaction mixture comprising at least the trialkyl phosphite, a hydroxy-aromatic by-product corresponding to each aryl group of the aryl phosphite, the catalyst and non-volatile by-products, vaporizing the reaction mixture with the exception of the catalyst and non-volatile by-products and separating the trialkyl phosphite from the resultant mixture. The volatilized by-products of the reaction may be recycled to the reaction zone. The temperature of the reaction zone may be at or below the boiling point of the trialkyl phosphite under the prevailing conditions. Suitable alcohols are ethanol, propanol, isopropanol, butanol, isobutanol, pentanol and hexanol. Suitable phosphorus containing compounds are aryl dialkyl phosphites, diaryl alkyl phosphites, triaryl phosphites and mixtures thereof.  Specified transesterification catalysts include metal alcoholates and phenolates, preferably the alkali metal salts, strong organic bases and strong inorganic bases. In a preferred process, as shown, an alkyl alcohol, an aryl phosphite of the formula P(OR)3 and a transesterification catalyst are supplied by conduits 12, 14 and 16 respectively to a reaction zone 10. The stream of reaction mixture is then conveyed to a separation zone 18 via conduit 20, where the reaction products are removed from the catalyst and non-volatile by-products.  The catalyst and the by-products may then be recycled to reaction zone 10 via recycle conduit 22 and conduit 16. The reaction products may then be transferred to the stripping column 24 by conduit 26.  In the stripping column 24 the lower boiling trialkyl phosphite and alkyl alcohol may be separated from the higher boiling by-products. The lower boiling fraction is then separated in product column 28 to recover the desired trialkyl phosphite after being conveyed by conveyer means 30.  The recovered phosphite may then be further purified in finishing column 32.  The recovered alcohol is recycled to the reaction zone 10 via conduits 29 and 12.  By-products column 34 receives the by-products of the reaction from the stripping column and separates the aromatic by-products containing hydroxyl groups from other by-products. The by-products, other than the aromatic by-products, are recycled to the reaction zone 10 via conduit 36, while the aromatic by-product is conveyed to converter 38 via conduit 40 where a tri-aromatic phosphite may be formed which may then be conveyed to reaction zone 10 via conduits 42 and 14.  When ethanol or isopropanol are reacted with triphenyl phosphite, the catalyst and non-volatile by-products are removed by flash vaporization. The catalyst may also be removed by neutralization, filtration or by an ion exchange membrane.  The reactants are fed into the reaction zone 10 at a rate to maintain an excess of alcohol. Examples are given for the production of triethyl and triisopropyl phosphite.