Method for producing hexanediol

US6727395B1 · kind B1 · utility

Assignee

• BASF SE

Inventors

• Frank Stein · Bad Dürkheim, DE
• Thomas Krug · Worms, DE
• Thomas Nöbel · Schifferstadt, DE
• Harald Rust · Bochum, DE

Key dates

• Filing date: Dec 19, 2001
• Grant date: Apr 27, 2004
• Expiry date: Jan 2, 2023

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C07C29/149
• WIPO field: Organic fine chemistry
• WIPO sector: Chemistry

Abstract

A process for preparing 1,6-hexanediol from a carboxylic acid mixture comprising adipic acid, 6-hydroxycaproic acid and small amounts of 1,4-cyclohexanediols which is obtained as by-product in the oxidation of cyclohexane to cyclohexanone/cyclohexanol after water extraction of the reaction mixture followed by extraction with aqueous sodium hydroxide solution, by esterification of the acids and hydrogenation comprisesa) liberating the carboxylic acids from the alkaline extract by addition of a mineral acid,b) fractionating the organic phase comprising carboxylic acids to give a distillate comprising the low molecular weight monocarboxylic acids and a residue comprising adipic acid and 6-hydroxycaproic acid,c) reacting the monocarboxylic an dicarboxylic acids present in the aqueous dicarboxylic acid mixture with a low molecular weight alcohol to give the corresponding carboxylic esters,d) freeing the esterification mixture obtained of excess alcohol and low boilers in a first distillation step,e) fractionating the bottom product in a second distillation step to give an ester fraction essentially free of 1,4-cyclohexanediols and a fraction comprising at least the major part of the 1,4…