Abstract: Alkanals having a 2-alkyl branch are obtained from mixtures which contain the alkanals having a 2-alkyl branch in addition to n-alkanals, 3-alkylalkanals and/or further isomers by a process in whicha) the alkanal mixture is reacted with an aqueous formaldehyde solution in the presence of a secondary amine and of a carboxylic acid as a catalyst,b) the aqueous phase containing the catalyst and any unconverted excess formaldehyde is separated off andc) the alkanals having a 2-alkyl branch are isolated by distillation from the condensates of the other alkanals with formaldehyde.

Abstract: Preparation of C.sub.3 - to C.sub.25 -alkanols by catalytic hydrogenation of corresponding crude C.sub.3 - to C.sub.25 -alkanols, as obtained in the cobalt-catalyzed hydroformylation of C.sub.2 - to C.sub.24 -olefins, by partial 80-95% hydrogenation conversion in a first stage using a silica supported nickel and molybdenum oxide catalyst and then completing the conversion in a second stage using a cobalt catalyst containing copper, manganese, molybdenum and,optionally other activating additives. The process is especially adapted to the economic preparation of C.sub.9 -C.sub.11 - and C.sub.13 -C.sub.15 -alkanols which are used to prepare high-grade plasticizer esters.

Abstract: Aldehydes are obtained from the gaseous product of the hydroformylation of olefinically unsaturated compounds using a rhodium catalyst by a process (cf. FIG. 2) in which(a) this gaseous product is introduced, without being cooled or depressured, into a distillation column D,(b) the top fraction from this column is cooled in a condenser K so that the greater part of the aldehydes contained therein is condensed,(c) the condensate is separated, in a separator A, into a gas phase and a liquid phase,(d) the gas phase from A, after waste gas has been separated off, is again brought to the hydroformylation pressure by means of a compressor P, and is returned to the reactor as a recycle gas,(e) the liquid phase from A is returned to D, and(f) the aldehydes are taken off from column D as liquid bottom products and/or as a vaporous side stream.