Process for manufacturing an aqueous hydrogen peroxide solution

Details Process for manufacturing an aqueous hydrogen peroxide solution Process for manufacturing an aqueous hydrogen peroxide solution

1999-06-17

2001-05-01

Griffin, Steven P. (Department: 1754)

Chemistry of inorganic compounds

Oxygen or compound thereof

Peroxide

C423S272000, C423S587000, C423S588000

Reexamination Certificate

active

06224845

ABSTRACT:

The present invention relates to an improved process for manufacturing a purified aqueous hydrogen peroxide solution.
It is known practice (patent application EP 0,529,723 Al in the name of lnterox International) to obtain a purified aqueous hydrogen peroxide solution according to the alkylanthraquinone process. In this known process, a crude aqueous hydrogen peroxide solution is introduced into a purifier fed with organic solvent. The aqueous hydrogen peroxide solution collected at the purifier outlet is then subjected to distillation. Some of the distillation residue is recycled into the oxidation step of the alkylanthraquinone process. The aqueous hydrogen peroxide solution obtained according to this known process contains a large amount of organic compounds. When the nature of these organic compounds is examined, it is seen that there are a variety of organic compounds present The chemical constitution of these organic compounds can be determined, for example, by GC/MS (gas chromatography/mass spectrometry). Distillation treatments allow the boiling points of the said compounds to be indicated. It has been found that a large fraction of the organic compounds comprises from 7 to 11 carbon atoms and at least one oxygen atom and has a boiling point of from 200° C. to 300° C. The organic impurities render the aqueous hydrogen peroxide solution of little use, in particular for electronic applications. It is thus desirable to provide an aqueous hydrogen peroxide solution which has a reduced content of organic impurities. It is also desirable to obtain the aqueous hydrogen peroxide solution in an economically and technically advantageous manner, for example by consuming a minimum amount of starting materials and fresh reagents.
The invention is directed towards overcoming this problem by providing an improved process for purifying an aqueous hydrogen peroxide solution, which gives a high purity of organic compounds while remaining economically advantageous.
Consequently, the invention relates to a process for manufacturing a purified aqueous hydrogen peroxide solution, in which a crude aqueous hydrogen peroxide solution is subjected to a washing operation with at least one organic solvent which has been subjected to a purification treatment prior to the washing operation.
It has been found, surprisingly, that the washing of a crude aqueous hydrogen peroxide solution with a solvent which has been subjected to a purification treatment prior to the washing solves the problem posed above. Washing removes most of the impurities usually found in the aqueous hydrogen peroxide solutions after a distillation treatment.
The term “washing” is intended to denote any treatment, which is well known in the chemical industry, of a crude aqueous hydrogen peroxide solution with an organic solvent which is intended to reduce the content of impurities in the aqueous hydrogen peroxide solution. This washing can consist, for example, in extracting impurities in the crude aqueous hydrogen peroxide solution by means of an organic solvent in apparatuses such as centrifugal extractors or liquid/liquid extraction columns, for example, operating counter-currentwise. Liquid/liquid extraction columns are preferred. Among the liquid/liquid extraction columns, columns with perforated plates are preferred.
The expression “crude aqueous hydrogen peroxide solution” is intended to denote the solutions obtained directly from a hydrogen peroxide synthesis step or from a hydrogen peroxide extraction step or from a storage unit. The crude aqueous hydrogen peroxide solution can have undergone one or more treatments to separate out impurities prior to the washing operation according to the process of the invention.
It is preferred to bring the organic solvent in counter-current relative to the crude aqueous hydrogen peroxide solution. The efficacy of the washing depends on the flow rate of the organic solvent. The efficacy of the washing is improved when the flow rate of the organic solvent is increased. The volume of organic solvent used for the washing is defined as the quotient of the flow rate of solvent and of the flow rate of the hydrogen peroxide solution. The volume used in the process according to the invention is generally at least 3 l per m
3
of crude aqueous hydrogen peroxide solution. Preferably, the volume is at least 25 l per m
3
of aqueous hydrogen peroxide solution. The volume is generally not more than 100 l per m
3
of aqueous hydrogen peroxide solution. The volume is preferably not more than 75 l per m
3
of aqueous hydrogen peroxide solution. The washing temperature is generally at least 10° C. It is preferred to work at a temperature of at least 20° C. Generally, the temperature is not more than 60° C., preferably not more than 40° C. The washing time depends on the size of the apparatus chosen and on the flow rate of crude aqueous hydrogen peroxide solution introduced into the apparatus.
In the process according to the invention, polar solvents, nonpolar solvents and mixtures thereof can be used as organic solvent. It is preferred to use a mixture of polar solvent and of nonpolar solvent The polar solvents ensure good extraction of the impurities. The nonpolar solvents ensure good phase separation since they are immiscible with water.
Nonpolar solvents which can be used, for example, are an aliphatic and/or aromatic hydrocarbon or a mixture thereof These hydrocarbons are, for example, benzene or benzene derivatives comprising from 1 to 5 alkyl substituents. Generally, the alkyl substituents contain from 1 to 5 carbon atoms. Haloaliphatic and/or haloaromatic hydrocarbons such as methylene chloride can optionally be used.
Polar solvents which can be chosen, for example, are an alcohol or a mixture of alcohols, an amide, a carboxylic or phosphoric acid ester, an alkylphosphate or a mixture of at least two of these solvents. Linear or branched secondary aliphatic alcohols give good results. Diisobutylcarbinol is suitable for use.
In the process according to the invention, the organic solvent is subjected to a purification treatment prior to the washing operation. This purification treatment can consist of any treatment known to those skilled in the art, which is intended to reduce the content of impurities. It can be, for example, a distillation or an adsorption, for example on a column packed with active charcoal, with alumina or with an ion-exchange resin, for example a mixture of a cation-exchange resin and an anion-exchange resin, or alternatively a separate bed containing the anion-exchange resin followed or preceded by a bed of cation-exchange resin.
In one variant of the process, which is preferred, the treatment to purify the organic solvent is carried out by steam stripping. The technique of steam stripping is known, for example, in “Handbook of separation techniques for chemical engineers, McGraw-Hill, 1996, part 1, pp. 249-274”. In the case of a mixture of nonpolar organic solvent and a polar organic solvent, the purification by steam stripping has the advantage that it leads to a polarity which favours the removal of the impurities. The weight ratio between the nonpolar organic solvent and the polar organic solvent in the mixture after purification is preferably less than or equal to 4. In a particularly preferred manner, this ratio is less than or equal to 3.
In the process according to the invention, the aqueous hydrogen peroxide solution can be obtained according to any method known to those skilled in the art. Preferably, the hydrogen peroxide solution is obtained according to the alkylanthraquinone process. The expression “alkylanthraquinone process” is intended to denote a process for producing an aqueous hydrogen peroxide solution which consists in subjecting a working solution of at least one alkylanthraquinone and/or of at least one tetrahydroalkylanthraquinone to a hydrogenation step, in a diluent, to produce one or more alkylanthrhydroquinones and/or alkyltetrahydroanthrahydro-quinones. Diluents which may be used are the liquids which can be used as organic solvent, described

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