Continuous production of organic phosphines

In a process for the continuous production of organic phosphines of the following general formula (I) or (II) ##STR4## in which formula (I) R.sub.1 and R.sub.2 each are selected from the group consisting of an alkyl-, cycloalkyl- or aralkyl group having 2 to 18 carbon atoms, or one of the substituents R.sub.1 and R.sub.2 is a hydrogen atom and the other is one of the said groups, and in which formula (II) m and n each are 1, 2 or 3, the sum of m+n being at most 5, and R.sub.3 and R.sub.4, being identical or different, each are a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, wherein the formula (I) compound is made by reacting an alkylene, cycloalkylene or aralkylene having 2 to 18 carbon atoms with hydrogen phosphide, or the formula (II) compound is made by reacting a compound of the following general formula (III) ##STR5## in which m, n, R.sub.3 and R.sub.4 have the meanings given above, with hydrogen phosphide at elevated temperature and under elevated pressure in the presence of a free radical-yielding catalyst solution in an inert solvent, terminating the reaction and separating the resulting organic phosphine from the reaction mixture, the improvement which comprises:

• continuously supplying from above a pressure reactor, which is provided in its interior with mixing elements, kept free from oxygen, and subdivided so as to comprise an upper cooling zone and a lower reaction zone, with (a) a solution of the alkylene, cycloalkylene or aralkylene or of a compound of general formula (III) and the catalyst in an inert solvent, and (b) a stoichiometric excess of hydrogen phosphide, the said (a) and (b) reactants being supplied jointly with, but separately from, one another;
• mixing the said (a) and (b) reactants in the upper cooling zone of the reactor at a temperature of about 0.degree. to 35.degree. C. and under a PH.sub.3 -pressure of about 80 to 300 bars;
• reacting the resulting mixture, which travels downwardly in the reactor, in the lower reaction zone at about 90.degree. to 190.degree. C., the reactants being allowed to remain in the reactor for a period of time about 13 to 15 times longer than the half life period of the catalyst;
• removing the reaction mixture through the bottom portion of the reactor and, after pressure release to atmospheric, subjecting the mixture to distillation so as to separate the organic phosphines therefrom.