Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2001-11-13
2003-12-02
Barts, Samuel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S386000, C568S389000, C568S397000, C568S411000, C568S754000
Reexamination Certificate
active
06657087
ABSTRACT:
The invention relates to an improved process for the work-up by distillation of cleavage product mixtures produced in the cleavage of alkylaryl hydroperoxides. In particular, the present invention relates to a process for the work-up by distillation of cleavage product produced in the cleavage of cumene hydroperoxide.
The process of acid-catalyzed cleavage of cumene hydroperoxide into phenol and acetone has long been of particular industrial importance. In this preparation of phenol from cumene by the Hock process, in a first reaction stage, the oxidation, cumene is oxidized to cumene hydroperoxide (CHP) and the CHP is then concentrated in a vacuum distillation, the concentration stage, to 65 to 90% by weight. In a second reaction stage, cleavage, the CHP is cleaved into phenol and acetone by the action of an acid, usually sulfuric acid. In addition to phenol and acetone the cleavage product has other compounds which can be formed in the reaction steps preceding the cleavage and which are not converted, or are only partially converted, in the cleavage. The most important compounds which can be present in the cleavage product in addition to phenol and acetone are, in particular, &agr;-methylstyrene (AMS), cumene and acetophenone. In addition, small amounts of dimethyl phenyl carbinol (DMPC) already formed in the oxidation may be present in the cleavage product. Further impurities comprise compounds such as methylbenzofuran (MBF), hydroxyacetone, mesityl oxide (MO) and carbonyl compounds such as (acet)aldehydes and 2-phenylpropionaldehyde, for example. After neutralizing the cleavage product and any removal of an aqueous phase, the cleavage product is worked up by distillation.
Various processes for work-up of the cleavage product by distillation are known (Ullmann's Encyclopedia of Industrial Chemistry, 5th completely revised edition, Vol. A19, 1991, VCH Verlagsgesellschaft mbH, Weinheim). In principle, in all these processes, the cleavage product is first neutralized, with aqueous sodium hydroxide solution, amines, aqueous phenolate lye and/or ion exchanger resin being used. After a phase separation, the organic part of the neutralized cleavage product is transferred to a first column in which crude acetone, which can contain water, hydroxyacetone, cumene and/or AMS, is distilled off overhead from the residual cleavage product. This crude acetone is usually treated with alkali in a washer and again purified by distillation. However, in part, the wash also takes place in the column. The bottoms product produced in the first column is distilled in a second column, residual AMS and cumene being taken off from this column overhead and usually being fed to a hydrogenation in which cumene is again prepared. AMS and cumene can also be separated off in an azeotropic distillation with water. The bottoms product remaining in the second column is distilled in a crude phenol column.
The resultant crude phenol can be further purified by an extractive distillation with water and/or by treatment with an acid ion exchanger and subsequent distillation. In the latter process compounds which are difficult to separate from phenol by distillation, for example mesityl oxide and hydroxyacetone, are condensed to form higher-boiling compounds.
In DE-AS 1 105 878 (phenol chemistry) also, the neutralized cleavage product which is separated off from the crude acetone in a crude acetone column is transferred into a hydrocarbon column in which, in the presence of water, hydrocarbons boiling lower than phenol, such as AMS and cumene are distilled off overhead. From the bottom of the column the organic phase is taken off and applied to the top of a downstream column in which water is separated off from phenol and high-boilers which are produced in the bottom of the column. The mixture of phenol and high-boilers is then transferred to a crude phenol column. The residues produced in the crude phenol column and in the pure phenol distillation can then be fed to a cracking still in which the residues are worked up and one part of phenol is recovered. These recovered products of value can again be transferred to the hydrocarbon column.
EP 0 032 255 (UOP) describes a process for working up cleavage product in which the organic part of a virtually neutralized (pH≈6) cleavage product is again washed with water and then the organic part is transferred to a crude acetone column in which the crude acetone is separated off from the remaining cleavage product. The residue remaining in the bottom phase is transferred directly to a cumene column in which the crude phenol is produced as bottoms product which in turn is fed to a purifying distillation. The mixture taken off overhead from the cumene column, which contains principally AMS, cumene and water, is transferred to a phase-separation vessel in which an aqueous phase is separated off. The resultant organic phase is transferred to a washing column in which the organic mixture is treated with sodium hydroxide solution in order to remove any phenol still present from the mixture of AMS and cumene as sodium phenoxide. The mixture of AMS and cumene which has been freed from phenol is fed via the top of the column to a hydrogenation. In U.S. Pat. No. 4,262,150 (UOP), also, the same column circuit is used as described in EP 0 032 255 (UOP). The difference from EP 0 032 255 is that, to neutralize the cleavage product, an extraction column is used instead of one or more combinations of mixers and phase-separation apparatuses.
U.S. Pat. No. 3,322 651 (UOP) describes the use of nitrogen compounds, in particular amines, for purifying phenol obtained in the cleavage of CHP.
U.S. Pat. No. 5,510,543 (GE) describes a process for working up the cleavage product from CHP cleavage, in which the cleavage product is adjusted to a pH of 4.0 to 4.9 in a neutralizer by adding a base, in particular sodium hydroxide solution. In the neutralizer the cleavage product is separated into an aqueous phase and an organic phase. The organic phase is transferred to a column termed the splitter in which the cleavage product is separated by distillation into an acetone-rich fraction and a phenol-rich fraction. The phenol-rich fraction is taken off at the bottom of the column and fed to a phenol purification, which can consist, for example, of one or more further distillations. The acetone-rich fraction is taken off at the top of the column and fed to an acetone column, in which case base is added to this fraction before entry into the column in such an amount that the fraction has a pH of approximately 9, so that the organic acids which are also present in this fraction are neutralized. The mixture arising in the bottom phase of the column which, in addition to water, also contains hydrocarbons and the salts of organic acids, is transferred to a phase-separation apparatus in which this mixture is separated into an organic phase and an aqueous phase. The organic phase can be treated again for recovery of cumene.
Furthermore, processes have been developed in which individual fractions which arise in the work-up by distillation of cleavage product are treated specifically. Thus, U.S. Pat. No. 5,487,816 (UOP) describes a process for separating off AMS from a mixture which contains phenol, AMS and water and which arises as bottom product of a crude acetone column. The crude acetone column is operated in this case in such a manner that cumene is taken off from the cleavage product at the top of the crude acetone column together with the acetone. The mixture containing AMS and phenol is separated in a column in such a manner that in the bottom of the column predominantly phenol is produced, which can be fed to further work-up, and at the top of the column a mixture of AMS, water and smaller amounts of phenol is taken off, which mixture is condensed and adjusted to a pH above 6 by adding a basic reagent. This achieves the phenol being principally present in the aqueous phase, while the AMS is present in an organic phase in which only small amounts of phenol are present as impurity. The phases are separa
Korte Hermann-Josef
Schwarz Christoph
Tanger Uwe
Ullrich Jochen
Weber Markus
Barts Samuel
INEOS Phenol & GmbH Co., KG
Witherspoon Sikarl A.
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