N-VALERIC ACID - EXPANSION OF THE 2 PHASE HYDROFORMYLATION TO BUTENES

n-valeric acid (n-pentanoic acid) is the basis of new ester-type lubri cants for CFC-substitutes in refrigeration systems which are made from the carboxylic acid with trimethylolpropane, pentaerythritol or dipen taerythritol. Together with UCC, Hoechst is one of the largest produce rs of n-valeric acid for this field of application. Valeric acid is pr epared from butene cuts through hydroformylation to valeraldehyde with subsequent oxidation. The RCH-RP process of low-pressure hydroformyla tion [1] used at the Ruhrchemie side of Hoechst, involving an aqueous rhodium-TPPTS catalyst system (TPPTS = triphenylphosphane trisulfonate , sodium salt), has been used since 1984 to produce roughly 300,000 to n of n-butyraldehyde from propylene per year. A further development of this successful technology has been achieved using the available feed stock base of isomeric butenes (raffinate II) for the preparation of n -C-5 products (n-valeraldehyde, n/iso-amyl alcohol and n-valeric acid) [2]. The process developed permits high selectivity of the n/iso rati o to the desired n-aldehyde and it is environmentally benign as waste water contamination has been substantially reduced. In December 1995 p roduction of n-valeraldehyde was started up in a new plant. Oxidation to produce the acid using the Hoechst/Ruhrchemie process is carried ou t with proven technology.