Abstract: Polyphenylene ethers are prepared from monohydric phenols, which possess alkyl substituents in the two ortho-positions and, if desired, in the meta-position, but not in the para-position, by an oxidative coupling reaction with oxygen at from 15.degree. to 50.degree. C. and under from 1 to 10 bar in the presence of a catalyst complex, of a solvent and, if required, of an activator, by a method in which the conversion of the phenols is carried out in two more reaction zones, in which some or all of the solvent, the catalyst complex and the phenols and, where relevant, the activator is initially taken and is circulated by means of a conveying unit, and about 60-100% of the stoichiometric amount of oxygen required for the oxidative coupling is introduced into the first reaction zone and from 0 to about 40% of the said stoichiometric amount is introduced into the second reaction zone.

Abstract: The catalyst is removed in the preparation of high molecular weight polyphenylene ethers from monohydric phenols, which are alkyl-substituted at the two ortho-positions but not at the para-position and may or may not be alkyl-substituted at the meta-position, by an oxidative coupling reaction with oxygen at from 15.degree. to 50.degree. C.

Abstract: A coherent explosive gas phase in a gas/liquid reactor comprising a tubular body which is closed at the top and into which one or more jets of liquid which are fed from a liquid circulation and are directed downward, emerge from one or more nozzles located at the highest point of the reactor, and entrain a gas phase which is to be dispersed, introduce it into the liquid and finally produce complete dispersion of the gas, is avoided by a method wherein, before start-up of the liquid circulation, the inactive reactor is charged with an amount of liquid reactant such that a gas space corresponding to the subsequent gas hold-up of dispersed bubbles under operating conditions remains at the top of the reactor, this gas space is filled with a gas, at a pressure p.sub.

Abstract: In the preparation of a high molecular weight polyphenylene ether from a monohydric phenol by an oxidative coupling reaction with oxygen in the presence of a catalyst complex obtained from a metal salt and an organic amine and in the presence of a solvent, and isolation of the metal ion component of the catalyst from the polyphenylene ether solution by means of a complex-forming or chelate-forming compound, the catalyst is removed by a method wherein complex formation and isolation of the metal ion component of the catalyst are carried out in an aqueous medium in the presence of from 0.1 to 5,000 mg of an anionic or non-ionic surfactant.