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    • 1. 发明申请
    • PROCESS FOR PREPARING 1,6-HEXANEDIOL
    • US20110263907A1
    • 2011-10-27
    • US13133006
    • 2009-11-30
    • Olivier AbillardGerd-Dieter TebbenRolf PinkosTobias Wabnitz
    • Olivier AbillardGerd-Dieter TebbenRolf PinkosTobias Wabnitz
    • C07C31/20
    • C07C67/08C07C29/149C07D313/04C07C31/20C07C69/675C07C69/44
    • A process for preparing 1,6-hexanediol from a carboxylic acid mixture which comprises adipic acid, 6-hydroxycaproic acid and small amounts of 1,4-cyclohexanediols and is obtained as a by-product of the oxidation of cyclohexane to cyclohexanone/cyclohexanol with oxygen or oxygen-comprising gases by water extraction of the reaction mixture, by esterification and hydrogenation to hexanediol, which comprises a) the mono- and dicarboxylic acids present in the aqueous reaction mixture are reacted with a low molecular weight alcohol to give the corresponding carboxylic esters, b) the resulting esterification mixture is freed of excess alcohol and low boilers in a first distillation stage, c) in a second distillation stage, a separation is performed of the bottom product into an ester fraction essentially free of 1,4-cyclohexanediols and a fraction comprising at least the majority of the 1,4-cyclohexanediols, d) the ester fraction from (c) is catalytically hydrogenated and 1,6-hexanediol is obtained in a manner known per se by distilling the hydrogenation product, e) optionally the bottom product of stage c) is subjected to a further esterification reaction with a low molecular weight alcohol, the low molecular weight alcohol is distillatively removed on completion of the esterification reaction, then adipic diesters and 6-hydroxycaproic esters are substantially separated from 1,4-cyclohexanediols and high boilers in the remaining bottom stream by distillation and said adipic diesters and 6-hydroxycaproic esters are fed to stage c), which comprises performing at least one of the esterification reactions with a catalyst which comprises at least one element of groups 3-14, and adding a monomeric or oligomeric polyol with at least 3 hydroxyl functions after the esterification reaction. After step c) of the process according to the invention, in a third distillation stage, a stream comprising essentially methyl 6-hydroxycaproate can be at least partly removed and heated to temperatures above 200° C. under reduced pressure, which cyclizes 6-hydroxycaproic ester to caprolactone, and pure ε-caprolactone can be obtained from the cyclization product by distillation.