Method for producing isomeric hexanoic acids from the subsidiary flows arising during the production of pentanals

A process for preparing isomeric hexanoic acids comprising 2-methylpentanoic acid from the secondary streams obtained in the preparation of pentanals, characterized in that

• a) a mixture comprising linear butenes is reacted in the presence of transition metal compounds of group VIII of the Periodic Table of the Elements with carbon monoxide and hydrogen at elevated temperature and elevated pressure to give a pentanal mixture;
• b) the mixture obtained in step a) is separated into a stream enriched with 2-methylbutanal and 3-methyl-butanal, and a stream enriched with n-pentanal;
• c) the stream enriched with 2-methylbutanal and 3-methylbutanal of step b) is reacted with formaldehyde;
• d) a stream enriched with 2-methylbutanal and a stream depleted of 2-methylbutanal are recovered from the reaction mixture obtained after step c);
• e) the stream depleted of 2-methylbutanal obtained after step d) is selectively reacted in the presence of a hydrogenation catalyst with hydrogen at elevated temperature and elevated pressure to give a mixture comprising isomeric hexanals;
• and
• f) the reaction mixture obtained in step e) is oxidized and isomeric hexanoic acids are removed by distillation.

A process for preparing isomeric hexanoic acids comprising 2-methylpentanoic acid from the secondary streams obtained in the preparation of pentanals, characterized in that

• a) a mixture comprising linear butenes is reacted in the presence of transition metal compounds of group VIII of the Periodic Table of the Elements with carbon monoxide and hydrogen at elevated temperature and elevated pressure to give a pentanal mixture;
• b) the mixture obtained in step a) is separated into a stream enriched with 2-methylbutanal and 3-methyl-butanal, and a stream enriched with n-pentanal;
• c) the stream enriched with 2-methylbutanal and 3-methylbutanal of step b) is reacted with formaldehyde;
• d) the reaction mixture obtained after step c) is selectively reacted in the presence of a hydrogenation catalyst with hydrogen at elevated temperature and elevated pressure to give a mixture comprising 2-methylbutanal and isomeric hexanals;
• and
• e) the reaction mixture obtained in step d) is oxidized and then 2-methylbutyric acid and a mixture of isomeric hexanoic acids comprising 2-methylpentanoic acid are removed by distillation.