Process for the preparation of pyrocatechol and hydroquinone

Details Process for the preparation of pyrocatechol and hydroquinone Process for the preparation of pyrocatechol and hydroquinone

C - Chemistry, Metallurgy

07

C

260/618, 202/73

C07C 39/08 (2006.01) C07C 37/60 (2006.01) C07C 37/74 (2006.01)

Patent

CA 1175445

ABSTRACT OF THE DISCLOSURE An improved process for the preparation of pyro- catechol and hydroquinone by reaction of phenol with a peroxidic hydroxylating reagent followed by working-up of the resultant reaction mixture is disclosed wherein the reaction mixture is: a) continuously fed to a first rectification column at a point between the rectifying section and the stripping section, the rectification column having 3 to 20 separation stages in the stripping section and 5 to 20 separation stages in the rectifying section, the first column being operated under pressure 0.02 and 5 bars, 20 to 95% by weight of the top product being condensed as liquid reflux and recycled to the first column, the top product from the first rectification column, which con- tains practically all constituents of the feed mixture boiling more easily than phenol, being removed, the bottom product is withdrawn, the bottom product containing phenol and substantially all of the more highly boiling constituents of the feed mixture; b) the bottom product of the first rectification column is continuously fed to a second rectification column, at a point between the stripping section and the rectifying section, said second rectification column having 3 to 20 separation stages in the stripping section and 3 to 15 separation stages in the rectifying stage, said second rectification column being operated under a pressure between 0.003 and 5 bars, 20 to 95% be weight of the product collecting at the head of said second rectification column being condensed and recycled as liquid reflux to the top of the second rectification column, pure phenol being removed as the top product and the bottom product being withdrawn said bottom product containing in addition to phenol, cyrocatechol and Le A 20 535-US hydroquinone. Pyrocatechol and hydroquinone are thereafter isolated from the bottom product of the second rectification column.

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