Patent ID: 8598392

Claim:
A continuous process for preparing a 1-hydroxyalkylcyclohexane of the formula (I) where R 1 is isopropyl and R 2 is hydrogen or a straight-chain or branched alkyl radical having from 1 to 3 carbon atoms, which comprises catalytically hydrogenating an aromatic carbonyl compound of the formula (II) and/or by catalytically hydrogenating an aromatic alcohol of the formula (III) in which the R 1 and R 2 radicals are each as defined in formula (I), in the presence of hydrogen and in the presence of a catalyst which comprises, as an active metal, ruthenium applied to a support, the support comprising SiO 2 , and the catalyst being used in the form of a fixed bed catalyst in a hydrogenation reactor or in a plurality of hydrogenation reactors connected in series, and the fixed bed catalyst, based on the total weight of the finished catalyst, having a ruthenium content of from 0.1 to 0.5% by weight; wherein the catalytic hydrogenation is performed in a cascade of n hydrogenation reactors connected in series comprising a first hydrogenation reactor and one or more further hydrogenation reactors, where n is an integer from 2 to 5, and where a1) the reaction mixture which has been discharged continuously from an upstream hydrogenation reactor and not recycled, and hydrogen, are introduced continuously into the downstream hydrogenation reactor, b1) the resulting reaction mixture comprising 1-hydroxyalkylcyclohexane of the formula (I) is discharged continuously from the particular hydrogenation reactor and optionally, partly recycled back into the particular hydrogenation reactor, and c1) optionally, the 1-hydroxyalkylcyclohexane of the formula (I) is removed from the reaction mixture which has been discharged from the nth hydrogenation reactor in step b1) and not recycled.