RESULTING FROM A CAPROLACTONE PRODUCTION

The present invention refers to an equipment and a process, utilizing said equipment, for processing of a product stream (a) comprising acetic acid, unreaeted cyclohexanone, reaction water and organic heavy ends, said product stream (a) being yielded in a caprolactone production wherein peracetic acid is generated from acetic acid and hydrogen peroxide according to reaction scheme (1) below and wherein yielded peracetic acid is subjected to a Baeyer-Villiger reaction with cyclohexanone according to reaction scheme (II) below

yielding a reaction mixture comprising caprolactone, acetic acid, unreaeted cyclohexanone, reaction water and heavy organic ends, which reaction mixture is further processed yielding purified caprolactone and at least one product stream (a) comprising acetic acid, unreaeted cyclohexanone, reaction water and heavy ends.

It is an object of the present invention to provide an improved, in particular a more economical process for obtaining pure products from said product stream (a). It has been found that this object is achieved by an equipment and a process comprising a divided wall column (1 ) for separating by distillation said product stream (a) obtained in said caprolactone process. Investment, costs can, by the present and claimed invention, be reduced with as much as 20% and heating, such as steam, costs by 20-30% compared wi h conventionally and typically used equipment comprising for instance at least one primary and one secondary distillation column.

The present invention is accordingly directed to an equipment and a process utilizing said equipment for processing of a said product stream (a), whereby said equipment and said process in embodiments of the present invention comprises/involves as main equipment a divided wal l column ( I ) comprising an upper section (2), a bottom section (3), a feed section (4) and a takeoff section (5), a separator (9), a distiliation column (20) and optionally a distillation column (15). Sections (4) and (5) comprise in especially preferred embodiments each at least one rectification and at least one stripping section.

Divided wall columns, that is distillation columns having vertical dividing walls preventing cross mixing of liquid streams and/or vapor streams in certain regions, are known for the separation of multicomponent mixtures by distillation. Divided wall columns typically have a dividing wall which divides the interior of the column into the following regions an upper section, a bottom section and a feed section and a take-off section. Mixture to be separated are introduced in the region of the feed section, high boiling fractions are removed from the bottom of the column and low boiling fractions are removed via the top of the column.

Said product stream (a), which typically comprises by weight for instance 45-65% of acetic acid, 30-40% of cyclohexanone, 1 -15% of water and 0-1 % of heavy ends, is in preferred embodiments of the present invention fed to the feed section (4) via an inlet (6) in the middle of said feed section (4) and said product stream (a) is in said feed section (4) by distillation separated in a water/acetic acid fraction (b) and a cyclohexanone/heavy end fraction (c), which typically comprises for instance more than 95% by weight of cyclohexanone.

The water/acetic acid fraction (b) is via an outlet (25) in said upper section (2) and an inlet (26) fed to a separator (9). Said acetic acid/water fraction is a homogeneous azeotrope which in presence of at least one entrainer is broken and in said separator (9) separated in an organic phase (d) comprising acetic acid and a minor amount of water and a water phase (e) comprising water and a minor amount of acetic acid. Entrainer(s) can be added for instance from a tank (24) via an inlet (10) arranged at said separator (9). The organic phase (d) is subsequently fed to said divided wall column (1) through an outlet (11 ) in said separator (9) and an inlet (12) in said upper section (2) and further evaporated yielding high concentrated acetic acid (f) typically having an acetic acid percentage of more than 95%, such as at least 98%, by weight, which is taken out via an outlet (13) in the middle of said take-off section (5) and preferably recycled to said peracetic acid generation or alternatively fed to for instance a storage tank for later use. and the water phase (e) is either dumped via an outlet (14) in said separator (9) or preferably via said outlet (14) fed to a distillation column (15) via an inlet (16) and further processed whereby water and said minor amount of acetic acid are separated in an acidic fraction (h) and a water fraction (i) consisting essentially of water. The acidic fraction (h) is preferably recycled, for recovery of remaining acetic acid, to said separator (9) via an outlet (17) arranged for instance at the top of said column (15) and an inlet (23) on said separator (9) and said fraction (i) can be dumped, sent to destruction or sent for further processing via an outlet (18) at the bottom of said column (15).

The cyclohexanone/heavy end fraction (c) is in preferred embodiments, via an outlet (7) in said bottom section (3) and via an inlet (19) fed to a distillation column (20) wherein cyclohexanone and heavy ends are separated in a purified cyclohexanone fraction (g) and a heavy end fraction (j). In said embodiments, the purified cyclohexanone fraction (g), typically having a cyclohexanone percentage of at least 98%, such as more than 99%, by weight is via an outlet (21 ) preferably recycled to said Baeyer-Villiger reaction or alternatively fed to for instance a storage tank for later use and the heavy end fraction (j) is via an outlet (22) either sent to destruction or to further processing.

The divided wall column ( 1) is. in preferred embodiments of the present invention, operated at a temperature of for instance 80-180°C, such as 100-160 ^o C, and at a pressure of 0.5-1.5 bar, such as 1.0-1.3 bar. Said separator (9) is, in likewise preferred embodiments, a liquid phase separato operated at a temperature of for instance 35-45°C and at a pressure of for instance 0.8-1.2 bar. Column (20) is preferably operated at a temperature of for instance 50-150°C and at a pressure of for instance 0.05-0.2 bar, and said optional column (15) is in preferred embodiments distillation column heated by a steam generator (27) and operated at a temperature of for instance 95-105°C and at atmospheric pressure.

Said entramer is in especially preferred embodiments of the present invention a C\ ~C alkyl acetate, such as methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate and/or isobutyl acetate. Further possible entrainers include aromatic and aliphatic hydrocarbons, such as toluene and hexane, and ethers, such as methyl feri.butyl ether. Entrainers for distillation of acetic acid/water systems are disclosed and discussed in for instance "Entrainer for batch distillation of acetic acid— water system" S.V. Gadekar et al., Journal of Scientific & industrial Research, vol. 68, Oct. 2009, pp 871-875.

In further aspects, the present invention refers to an equipment as well as a process as disclosed above and for processing of a product stream (a) comprising acetic acid, unreacted cyclohexanone, reaction water and organic heavy ends, which product stream (a) is yielded in a caproiactone production wherein peracetic acid is generated from acetic acid and hydrogen peroxide and wherein said peracetic acid is subjected to a Baeyer-Villiger reaction with cyclohexanone.

While particular embodiments and aspects of the invention have been disclosed, it will be understood, of course, that the invention is not limited thereto since many modification may be made. These and other objects will be more fully understood from the appended Figure 1 wherein an embodiments of the present and claimed invention is schemed and reference numerals and the like are as previously herein disclosed.