Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
1999-12-13
2001-09-25
Shippen, Michael L. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S728000, C568S749000
Reexamination Certificate
active
06294702
ABSTRACT:
The present invention relates to a process for the continuous production of dihydroxydiphenylalkanes (bisphenols) by the reaction of fresh phenol, and of phenol obtained from the cracking of by-products containing phenol, with isoalkenylphenol and ketone. In the course of this process the reaction mixture is worked up by distillation and a high-purity bisphenol is produced. The bottom products and distillates containing the by-products are cracked under basic conditions and optionally thereafter under acidic conditions. The cracked products, which substantially consist of isoalkenylphenol and phenol, are recycled, optionally after purification, with the phenol obtained during the purification of bisphenol, to the reaction to form bisphenol. The residue obtained from cracking is disposed of.
It is known that bisphenols can be produced by the acid-catalysed reaction of ketones with phenol. There is a series of different proposals which have been made for this purpose (see U.S. Pat. No. 2,775,620, EP-A 342 758, EP-A 616 993, DE-OS 38 33 900, U.S. Pat. No. 4,308,404, U.S. Pat. No. 4,308,405, EP-A 630 878, U.S. Pat. No. 4,876,391, U.S. Pat. No. 3,242,219, for example).
In Ullmann's Encyclopedia of Industrial Chemistry, 5th Ed., Vol. A19, pp. 348-52, there is a review of the prior literature on the production of bisphenol. As a rule, bisphenols, particularly bisphenol A. which is the most important commercially of the bisphenols, are produced by adding ketone and phenol to a circulating mother liquor from the work-up of bisphenol passing this mixture over acidic ion exchangers and carrying out the reaction to produce bisphenol. Unreacted ketone is optionally recovered from the reaction mixture and is recycled to the reaction. The reaction mixture is cooled, and the bisphenol is crystallised out, optionally as a phenol addition compound, and is separated and washed with phenol. The phenol is separated from the addition compound by flash distillation and pure phenol is obtained. The mother liquor from the crystallisation stage is passed over acidic ion exchangers and any isomers which it contains are rearranged to form bisphenol. The bisphenol which is produced in this manner is separated by crystallisation, and the crystallised product obtained is transferred to the first crystallisation stage. Part (about 10 to 20%) of the mother liquor which is then obtained is separated and the bulk is recycled to the reaction. Phenol is distilled from the part which is separated and is recycled to the reaction. The residue obtained on distillation is removed from the process and is used for the production of phenolic resin, for example.
In this procedure, which is relatively complicated, the mother liquor is recycled time after time over the catalyst. This gives rise to many isomers and by-products, and also results in coloured compounds. The latter have to be carefully separated from bisphenol. which possibly makes a further crystallisation stage necessary. In addition, appreciable amounts of valuable compounds such as bisphenol and isomers are lost with the part which is separated and which is finally removed from the process. This removal from the mother liquor is absolutely necessary in order not to allow the amount of unusable contaminating compounds to become too large.
Attempts have therefore been made to subject the fraction which is removed from the process to work-up and cracking in order to recover valuable substances for the production of bisphenol. There has also been a series of proposals for this purpose. According to U.S. Pat. No. 2,497,503, phenols and alkenylphenols which still have to be carefully purified can be obtained in moderate yield by pyrolysis at about 300° C. According to the teaching of EP-A 17 852, a hydrogenation treatment also results in valuable products. The cracking process can also be speeded up by acidic and basic compounds. However, with acids such as sulphuric or toluenesulphonic acid, only phenol is obtained (U.S. Pat. No. 3,466,337). In contrast, basic catalysts result in the cracking of materials removed from the process into phenol and isoalkenylphenol. The following have been cited as catalysts: alkali compounds such as NaOH, KOH, NaHCO
3
, Na acetate, Na hypophosphite. K
2
CO
3
, MgO and Al isopropylate (U.S. Pat. No. 4,277,628, U.S. Pat. No. 4,594,459, U.S. Pat. No. 4,131,749). When this procedure is used, however, only part of the material removed from the process is cracked, and a batch or semi-continuous process is employed. Completely continuous processes are unknown.
These processes have been improved as regards a higher purity of the bisphenol by feeding the phenol/isoalkenylphenol mixture from the cracking stage into the first mother liquor after separating the first bisphenol fraction. The mixture is passed over the acidic catalyst, and both rearrangement and the reaction of isoalkenylphenol with phenol are allowed to proceed simultaneously. The second bisphenol fraction is then separated from the mixture by crystallisation, and the second mother liquor is recycled to the cracking stage. Tile second bisphenol fraction is fed to the first crystallisation stage. The purity of the bisphenol is thereby increased somewhat, but the process is complicated by a further recycling stage (U.S. Pat. No. 4,954,661).
It has also been proposed that the second mother liquor in the aforementioned bisphenol process, or the first mother liquor after separating the first amount of bisphenol and alter rearrangement be worked-up at least in part by distillation in order to achieve better utilisation of the valuable products contained therein. The bisphenol which is thus obtained is recycled to the first crystallisation stage and is purified there. The low-boiling fractions which contain isomers are fed to the reaction (WO 94/20 445 and EP-A 552 518). The difficulty consists of obtaining fractions which are sufficiently pure, and which arc particularly low in difficultly separable chromanes and indanies, from the mother liquor, which is considerably enriched in isomers and by-products, at a justifiable cost, without overly increasing the amount of residue which can no longer be used and without reducing the yield. A part of the distillation products therefore has to be rejected. The fractions low in bisphenol which are obtained on distillation can also be subjected to cracking, and the cracked products can be recycled to the process (EP-A 332 033).
It has also been proposed that bisphenol which originates from the first crystallisation stage in the aforementioned bisphenol process be purified further by distillation, whereby a high-purity (up to 99.985%) bisphenol is obtained (EP-A 679 626).
It has now been found that an outstanding yield of bisphenol of high purity is obtained, by a simple, completely continuous process, if phenol is reacted with ketone and isoalkenylphenol from the cracking stage so that as few as possible isomers and by-products are formed, this reaction product is freed from acidic constituents if necessary water of reaction and residual acetone are distilled off, the reaction mixture is concentrated by evaporation and phenol is recovered for the reaction process, the residue obtained is separated in an efficient distillation column into a distillate containing low-boiling fractions and bisphenol and into a bottom product containing high-boiling fractions, the distillate is separated in a further column into a low-boiling distillate and into a bottom product which constitutes high-purity bisphenol, the low-boiling distillate is combined with the high-boiling fractions from the first column, is treated with a basic catalyst and is continuously cracked in a reactive rectification stage. The distillate containing phenol and isoalkenylphenol is fed to the bisphenol reaction. The bottom product is acidified if necessary and is subjected to a second cracking procedure in a further reactive rectification stage, whereupon phenol passes over and an unusable residual bottom product is formed.
The starting materials for the process according to the
Buysch Hans-Josef
Fengler Gerd
Fennhof Gerhard
Osselaer Tony Van
Bayer Aktiengesellschaft
Gil Joseph C.
Preis Aron
Shippen Michael L.
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