Organic compounds -- part of the class 532-570 series – Organic compounds – Polycyclo ring system containing anthracene configured ring...
Reexamination Certificate
1998-09-10
2001-01-30
Kight, John (Department: 1612)
Organic compounds -- part of the class 532-570 series
Organic compounds
Polycyclo ring system containing anthracene configured ring...
C552S296000
Reexamination Certificate
active
06180804
ABSTRACT:
TECHNICAL FIELD
This invention relates to the anthraquinone process for the manufacture of hydrogen peroxide. More particularly, the invention is a process for regenerating a working solution used in the preparation of hydrogen peroxide in which tetrahydro-alkylanthraquinone epoxide is converted to working compound using a boehmite catalyst.
BACKGROUND
The anthraquinone process (also called the autoxidation process or the Riedl-Pfleiderer process) for the manufacture of hydrogen peroxide (H
2
O
2
) is well known. It is described, for example, in Riedl, U.S. Pat. No. 2,158,525, and in the
Kirk
-
Othmer Encyclopedia of Chemical Technology
, 3rd. ed., Volume 13, Wiley, New York, 1981, pp. 15-22. The process is shown schematically below.
In this process, an alkyl-substituted anthraquinone (I), preferably a 2-alkylanthraquinone, known as a working compound, is dissolved in a suitable solvent or solvent mixture to form a working solution. The working solution is catalytically reduced to form the corresponding dihydroanthraquinone (II). The dihydroanthraquinone is separated from the hydrogenation catalyst and exposed to an oxygen-containing gas, usually air, to produce hydrogen peroxide and reform the anthraquinone (I). The hydrogen peroxide is extracted from the solvent with water, purified, and concentrated. The extracted solvent is recycled to the hydrogenation step to reform the dihydroanthraquinone (II) and continue the process.
During the hydrogenation and oxidation steps the working compound can undergo a number of secondary reactions. Reduction of one of the aromatic rings produces a tetrahydro-anthraquinone (III). Although the tetrahydro-anthraquinone is effective in producing hydrogen peroxide and is considered to be part of the working compound, it is the apparent precursor of a tetrahydro-anthraquinone epoxide (IV). The tetrahydro-anthraquinone epoxide is ineffective in producing hydrogen peroxide. It builds up in the working solution as the working solution is recycled through the process. Eventually it must be converted to working compound or removed to maintain the composition of the working solution within prescribed limits.
Numerous processes for regenerating the working solution have been disclosed. For example, Sprauer, U.S. Pat. No. 2,739,875, discloses regenerating the working solution by heating it with either activated alumina or activated magnesia. Logan, U.S. Pat. No. 3,912,766, discloses that a degraded working solution may be regenerated by subjecting the solution to at least two different regeneration agents differing in at least one significant characteristic. The treatments suggested included activated alumina for the hydro (reduced) phase, and aqueous sodium hydroxide for the neutral (oxidized) phase. Shin, U.S. Pat. No. 3,965,251, discloses regenerating a working solution by contacting it at 130° C. or higher with a platinum metal and an olefinic compound whose hydrogenation compound is gaseous at the operating temperature. Ochoa, U.S. Pat. No. 4,566,998, discloses a process for regenerating a mixed oxidized and hydrogenated working solution with an alkaline, activated alumina containing sodium oxide at 145° C.
Although the epoxide can be converted back to working compound, these conversions are not quantitative; usually there is a significant loss of working compound. Because anthraquinone is expensive, this loss is a significant expense in the process. In addition, the epoxide is usually converted to working compound in the hydro phase or reduced phase (after hydrogenation), but dehydrogenation of tetrahydro-anthraquinone to the anthraquinone usually takes place in the neutral, or oxidized, phase (before hydrogenation) so that it necessary to treat both phases of the process. Thus, a need exists for a better method for converting tetrahydro-anthraquinone epoxide to working compound and which, preferably, also converts the tetrahydro-anthraquinone to the corresponding anthraquinone, so that it is only necessary to treat one phase of the process.
DISCLOSURE OF THE INVENTION
The invention is a process for regenerating a working solution used in the preparation of hydrogen peroxide in which tetrahydro-alkylanthraquinone epoxide is converted to working compound using a boehmite catalyst. More particularly, the invention is a process for regenerating a working solution used in the preparation of hydrogen peroxide, the working solution comprising working compound, a solvent, and a tetrahydro-alkylanthraquinone epoxide, the process comprising contacting the working solution with a catalyst comprising from 5% to 100% boehmite at a temperature of 25° C. to 150° C., whereby at least a portion the tetrahydro-alkylanthraquinone epoxide is converted to working compound.
As a result of this treatment at least part of the tetrahydro-alkylanthraquinone epoxide is converted to working compound. In addition, part of the tetrahydro-alkylanthraquinone is dehydrogenated to the alkylanthraquinone. The method is preferably carried out in the hydro phase, i.e., after reduction of the working solution, but before oxidation of the working solution.
Working Solution
The working solution comprises the working compound and the solvent. The working compound includes the alkylanthraquinone as well as those products formed from the alkylanthraquinone during the reduction and oxidation steps that are effective in producing hydrogen peroxide. Reaction products that are not effective in producing hydrogen peroxide are not considered to be part of the working compound. Although the chemical yield of hydrogen peroxide per cycle is high, these reaction products, known as inerts, build up in the working solution as the working solution is recycled through the process. Eventually these compounds must be either converted to working compound or removed to maintain the composition of the working solution within its prescribed limits.
Alkylanthraquinones suitable for use as the working compound are substituted with an alkyl group, preferably an alkyl group of one to six carbon atoms, on a position not immediately adjacent to the quinone ring (i.e., the 2-, 3-, 6-, or 7-position). These include 2-ethylanthraquinone, 2-iso-propylanthraquinone, 2-sec-butylanthraquinone, 2-tert-butylanthtraquinone, 2,5-butylanthraquinone, 2-sec-amylanthraquinone, 2-methylanthraquinone and 1,3-dimethylanthraquinone, as well as other alkylanthraquinones known in the hydrogen peroxide art. Preferred alkylanthraquinones are 2-ethylanthraquinone, 2-tert-butylanthraquinone, and 2-amylanthraquinone. A more preferred alkylanthraquinone is 2-ethylanthraquinone.
During the reduction and oxidation steps the anthraquinone can undergo a number of secondary reactions. Reduction of one of the aromatic rings produces 5,6,7,8-tetrahydro-anthraquinone (III). The tetrahydro-anthraquinone is also effective in producing hydrogen peroxide and is considered to be part of the working compound.
The maximum capacity of the working solution for a continuous flow process is limited by the solubility of the working compound in either its reduced or oxidized state. The solubility is, in part, dependant on the alkyl substituent on the alkylanthraquinone and the solvent system. Typically the maximum working compound solubility is a eutectic mixture of the alkylanthraquinone and the tetrahydro-alkylanthraquinone. Therefore, for optimum process operation, the composition of the working solution must be maintained within prescribed limits.
The solvent must have a high partition coefficient for hydrogen peroxide with water so that hydrogen peroxide can be efficiently extracted. It should be chemically stable to the process condition, insoluble or nearly insoluble in water, and a good solvent for the alkylanthraquinone in both its oxidized and reduced forms. For safety reasons, the solvent should have a high flash point, have a low volatility, and be nontoxic. Mixed solvents may be used to enhance the solubility of the anthraquinone working compound in both its hydrogenated (reduced) form, i.e., the hydroquinone form, and its oxidized (neutral) fo
Baker Patrick C.
Covington Raymond
FMC Corporation
Kight John
Monroe Bruce M.
LandOfFree
Reversion of expoxide in the production of Hydrogen peroxide does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Reversion of expoxide in the production of Hydrogen peroxide, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Reversion of expoxide in the production of Hydrogen peroxide will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2548223