Hoechst Aktiengesellschaft

Stefan Schafer

Klaus Gehrmann

Alexander Ohorodnik

Albert Mainski

Karl-Heinz Steil

Eberhard Auer

Johannes Rosenthal

Wernfried Riechmann

Friedhelm Bylsma

The disclosure relates to a process for making methyldichlorophosphane by reacting methane with phosphorus trichloride in the presence of 2 to 7 mol % carbon tetrachloride, based on the phosphorus trichloride used, at temperatures of 500.degree. to 650.degree. C. and over a period of time of 0.1 to 0.9 second. More particularly, the reaction is effected under a pressure of 2 to 10 bars, the proportion of carbon tetrachloride added being reduced at increasing pressure.

Process for making methyldichlorophosphane

The invention relates to a process permitting the deposition of solid matter in mixtures containing methyldichlorophosphane to be avoided. To this end, the mixture is stabilized by admixing it with phosphoric acid or a soluble compound containing at least one acid group selected from phosphoric acid, phosphonic acid, sulfonic acid, phosphonous acid, thiophosphoric acid or dithiophosphoric acid.

Process permitting the deposition of solid matter in mixtures containing

Production of methyldichlorophosphane. The compound is made by reacting methane and phosphorus trichloride in a reaction zone in which a temperature higher than 500.degree. C is maintained. More specifically, hot reaction gas coming from the reaction zone is mechanically freed from solid matter, and the reaction gas freed from solid matter is passed to a quenching zone in which it is quenched with liquefied reaction mixture having 0.3 to 5 weight % of an organic barium compound or a non-ionic surfactant dissolved therein.

Production of methyldichlorophosphane

Pure methyldichlorophosphane is recovered from a mixture containing phosphorus trichloride and methyldichlorophosphane as its principal constituents by distillation in two stages. Phosphorus trichloride and other low-boiling material are distilled off overhead in the first stage and methyldichlorophosphane is distilled off from high-boiling material in the second stage, the latter being fed with base product coming from the first stage. More specifically, there is dissolved in the said mixture, prior to admitting it to the first distillation stage, 0.01 to 1 weight % of an organic barium compound or 0.1 to 10 weight % of a non-ionic surfactant, and the base product coming from the first distillation stage is admixed, prior to admitting it to the second distillation stage, with 1 to 10 weight % of phosphorus oxychloride.

Production of pure methyldichlorophosphane

Methyldichlorophosphane is made by reacting methane with phosphorus trichloride in contact with carbon tetrachloride at temperatures higher than 500.degree. C. To this end, the starting reactant mixture is admixed with 2 to 7 mol % of reaction-initiating carbon tetrachloride, based on phosphorus trichloride; the carbon tetrachloride is reacted to an extent of 50 to 80% by varying the reaction temperature within the range 550.degree. to 650.degree. C for constant residence times of 0.1 to 0.9 second; and resulting reaction mixture containing a residual analytically detectable 20 to 50% proportion of the carbon tetrachloride used is condensed out.

Dilute sulfuric acid contaminated with acetic acid and hydrogen chloride is purified with the resultant formation of concentrated sulfuric acid and acetic acid. To this end, the contaminated sulfuric acid is heated in a first step to at most 60.degree. C under 25-30 mm Hg so as to expel all of the hydrogen chloride together with minor proportions of acetic acid and water. In a second step, the sulfuric acid is heated to at most 165.degree. C under 20-25 mm Hg so as to distil off the bulk of acetic acid together with water. In a third step, the sulfuric acid is cooled down to 60.degree.-90.degree. C, diluted with 10-30 wieght % of water with agitation and while cooling is continued. Following this, the sulfuric acid is heated to 160.degree.-165.degree. C under 20-25 mm Hg and thereby freed from the water and residual acetic acid.

Purification of sulfuric acid containing acetic acid

Crude hydrogen chloride gas obtained as a by-product in the production of chloroacetic acids by the catalytic chlorination of acetic acid with chlorine gas in contact with acetic anhydride and/or acetyl chloride, and contaminated with about 0.6 up to 3 % by volume of acetyl chloride is purified. To this end, crude hydrogen chloride gas is introduced into the base portion of a scrubbing zone and scrubbed countercurrently therein with 0.5 up to 20 liter, per normal cubic meter (S.T.P) of hydrogen chloride gas, of a cooled scrubbing liquid under circulation, consisting substantially of 20-80 weight % of concentrated H.sub.2 SO.sub.4, 15-60 weight % of acetic acid, and 5-50 weight % of water. The resulting purified moist hydrogen chloride gas issuing at the head of the scrubbing zone is introduced into the base portion of a drying zone and scrubbed countercurrently with precooled sulfuric acid under circulation.

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Bruhl, Germany

Stefan Schafer