PROCESS FOR THE SELECTIVE CATALYTIC DEHALOGENATION OF HALOCARBOXYLIC ACIDS

• Main Authors: WERNER MITTLER, HANS-JOACHIM HARDEL, ALEXANDER OHORODNIK, JOACHIM HUNDECK, KURT SENNEWALD
• Format: Patent
• Language: English
• Published: 19.07.1972
• Subjects: ACYCLIC OR CARBOCYCLIC COMPOUNDS; APPARATUS THEREFOR; CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOIDCHEMISTRY; CHEMISTRY; GENERAL METHODS OF ORGANIC CHEMISTRY; METALLURGY; ORGANIC CHEMISTRY; PERFORMING OPERATIONS; PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL; THEIR RELEVANT APPARATUS; TRANSPORTING

1282682 Dehalogenation of haloacids KNAPSACK AG 16 March 1970 [25 March 1969] 12540/70 Heading C2C Monohalocarboxylic acids are prepared from dihalocarboxylic acids, optionally in admixture with trihalocarboxylic acids, by hydrogenation at 60‹ to 170‹ C. using a stationary or suspended catalyst comprising a Group VIII metal with an inert carrier, the catalyst being activated by one or more of (a) a non-poisonous metal salt, oxide or hydroxide, and/or (b) an inorganic or organic proton donor. Examples relate to the purification of crude monochloroacetic acid obtained by the chlorination of glacial acetic acid in the presence of acetic anhydride and acetyl chloride, the product containing dichloroacetic acid, trichloroacetic acid and acetic acid. Metal and ammonium activators specified are metals, alkaline earth metals, rare earth metals or metals of Groups 4 or 5, e.g. lithium chloride, sodium acetate, sodium chloride, sodium chloroacetate, sodium carbonate, potassium acetate, potassium chloride, ammonium acetate, ammonium chloride, calcium chloride, aluminium chloride, cerium dioxide, titanium dioxide and vanadium pentoxide. Organic proton-donor activators specified are triethylamine, pyridine, 4-amino-pyridine, piperidine, glycine, urea or triphenyl-phosphine, salts thereof, trichlorosilane, glycocoll, butyraldehyde, di-isobutyl ketone, butyl acetate and cyanoacetic acid. Granular inert carriers of small grain size are advantageous. Specified catalyst-carrier systems are palladium-silica or silicic acid. The process is preferably operated continuously, with recycling of the hydrogenated products and separation of the catalyst therefrom.