Abstract: A process for decomposing organohalogen compounds which are present in dust-laden gases which have a carbon content of less than 0.6% by weight, by oxidative breakdown with the aid of solid catalysts suitable for this purpose, whereina) the dust is deposited from the gases at 250.degree.-500.degree. C., and the dust-free gas is passed together with oxygen or an oxygen-containing gas over the catalyst, orb) the deposition of the dust takes place at below 250.degree. C., the organohalogen compounds are desorbed from the dust in an oxygen-containing gas stream at 250.degree.-500.degree. C., and the gas stream is passed over the catalyst, orc) the dust-laden gas is passed in the presence of oxygen over the catalyst at 250.degree.-500.degree. C., and the dust is subsequently removed.

Abstract: Butynediol is prepared by reacting acetylene and formaldehyde in contact with a heavy metal acetylide as catalyst, in the liquid phase by the Reppe method. Acetylene is fed upwardly through a suspension of the catalyst in formaldehyde at such a rate that it is virtually completely consumed and a liquid zone containing no catalyst is formed above the suspension.

Abstract: Production of 4,4'-diphenylmethane diisocyanate and a mixture of diisocyanates and polyisocyanates by the phosgenation of pure 4,4'-diaminodiphenylmethane and a mixture of diamines and polyamines. 4,4'-Diaminodiphenylmethane is obtained by distillation of the mixture of products obtained from the reaction of aniline with formaldehyde and crystallization of the distillate from a solvent. The combined distillation residue and mother liquor from the crystallization form the mixture for reaction with phosgene to produce a mixture of diisocyanates and polyiisocyanates. This process produces a highly pure 4,4'-diphenylmethane diisocyanate which is particularly suitable for the production of polyurethanes serving as intermediates in the manufacture of rigid foams or as glue.