Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2000-11-13
2002-12-03
Shippen, Michael L. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C423S449900, C568S754000
Reexamination Certificate
active
06489518
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a process for reducing the salt content of fractions comprising high boilers obtained in the preparation of phenol from cumene, by extraction. The process is particularly suitable for reducing the salt content of fractions comprising high boilers which already have a low phenol content, where the phenol content of the fractions comprising high boilers is further reduced by the process claimed and phenol is thereby recovered.
The invention likewise relates to the use of fractions comprising high boilers which have been extracted according to the invention as starting materials for the production of carbon black.
2. Discussion of the Background
In the preparation of phenol from cumene by the Hock process, cumene is oxidized to cumene hydroperoxide (CHP) in a first reaction step, known as oxidation. As is known, dimethyl phenyl carbinol (DMPC) and acetophenone (ACP) are formed as by-products in this step. In a second reaction step, known as cleavage, the CHP is cleaved into phenol and acetone by action of an acid, usually sulfuric acid. The product from the cleavage is subsequently neutralized with an alkali, usually aqueous sodium hydroxide, and worked up by distillation. Particularly in the cleavage, high-boiling components such as cumylphenols and indanes are formed from DMPC and these together with ACP are obtained as a high-boiling fraction (bottom product) in the distillation. Further constituents of this bottom product are alkali metal salts which get into the distillation as a result of the neutralization, and also phenol. U.S. Pat. No. 5,284,735 mentions typical a phenol content of 5-40% by weight, a ACP content of 5-30% by weight, a cumylphenol content of 10-50% by weight and a salt content of 0-2% by weight.
The bottom product or the fraction comprising high boilers is customarily incinerated as described in U.S. Pat. No. 5,283,376, by which means steam can be generated. As a further possible way of utilizing this fraction, Poll Nafta (Katowice, Poll) (1975), 31(12), 484/7, has described mixing it into asphalts, but this is problematical in the case of high phenol contents in the fractions comprising high boilers.
In the incineration of the fractions comprising high boilers, the sodium salts cause problems since they result in corrosion and emissions. The removal of these salts from the bottom product of phenol plants has been described many times. DE-B 1 219 035 describes, for example, the extraction of the salts using 10% strength sulfiric acid. U.S. Pat. No. 5,283,376 describes a process in which a fraction comprising high boilers is treated with an aqueous amine solution with the aim of simultaneously lowering the phenol content and the alkali metal content. Finally, U.S. Pat. No. 5,847,235 describes a process in which the fraction comprising high boilers is treated with water without further additives at from 10 to 90° C. in a multistage countercurrent extraction plant. Thus, according to U.S. Pat. No. 5,847,235, the salt content can be reduced from 0.139% to less than 0.001% (10 wppm) in a six-stage extraction column at 85° C. when the ratio of fraction comprising high boilers to water is 1:0.5 and the phenol content of this fraction is 17.2%. The fraction comprising high boilers forms the heavy phase in this extraction.
The phase separation between bottom product and water or aqueous solutions is, however, often incomplete. Causes are, depending on the composition of the fraction comprising high boilers or the bottom product, an insufficiently large density difference between the two phases, an excessively high viscosity of the bottom product and inhibition of coalescence at the phase interface presumably caused by the interfacial tensions being too low. Such unsatisfactory phase separations occur especially when the phenol content in the bottom product is low, i.e. below 5% by weight. Under unfavorable circumstances, the density ratios can be reversed in the extraction apparatus, i.e. contrary to the description in U.S. Pat. No. 5,847,235, the bottom product can become the lighter phase, so that malfunctions occur in the operation of such plants. Low phenol contents of less than 5% by weight in the fraction comprising high boilers and thus correspondingly low phenol losses over the entire phenol process are, however, desirable, since this increases the overall yield of the process and thus improves the economics. Such low phenol contents can be achieved by appropriate measures in the distillation, e.g. in combination with a thermal after-treatment (cracking) of the bottom products from the phenol columns as described in DE-B 1 121 621.
It is therefore an object of the present invention to provide a process for removing the salts from fractions comprising high boilers, in which optimum extraction conditions are achieved by means of good phase separations even when the fractions comprising high boilers have low phenol contents.
SUMMARY OF THE INVENTION
It has surprisingly been found that a process for reducing the salt content of fractions comprising high boilers obtained in the preparation of phenol from cumene, by extraction, in which not only an aqueous phase but also an organic phase or liquid are mixed into the streams comprising high boilers considerably simplifies the extraction and subsequent phase separation even in the case of low phenol contents in the streams comprising high boilers and also enables part of the phenol to be recovered from the fraction comprising high boilers.
The present invention accordingly provides a process for reducing the salt content of fractions comprising high boilers which are obtained in the preparation of phenol from cumene, by extraction, wherein at least one organic liquid is mixed as diluent into a fraction comprising high boilers which is to be extracted.
The present invention likewise provides for the use of a fraction comprising high boilers which has been extracted by a process as described above, as starting material for the production of carbon black.
In addition, the present invention provides for the use of a process as described above for recovering phenol from fractions comprising high boilers and containing up to 5% by weight of phenol.
The process of the invention has the advantage that mixing at least one organic phase or liquid into the fractions comprising high boilers before or during extraction with water or an aqueous phase or solution considerably simplifies the subsequent phase separation. Use of the process of the invention makes only one extraction stage and one phase separation sufficient for achieving the necessary salt content.
A further advantage of the process of the invention is that, even in the case of low phenol contents in the fractions comprising high boilers, part of the phenol can be recovered from these fractions.
In addition, mixing in an organic liquid of suitable density also makes it possible to influence the phase separation so that, for example, the organic phase is always the lighter phase (less dense) and the aqueous phase is always the heavier phase (more dense), even if the fractions comprising high boilers have a similar or even higher density compared to the aqueous phase. The advantage provided by the process of the invention in this respect is that phase separation is always ensured in the case of a continuous or batchwise process and that the organic phase is always the lighter phase so that it is not possible, for example, for the organic phase instead of the aqueous phase to be passed to a water treatment plant for treatment and cause damage there.
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Bickert Peter
Jordan Wilfried
van Barneveld Heinrich
Weber Manfred
Weber Markus
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Phenolchemie GmbH & Co. KG
Shippen Michael L.
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