Liquid purification or separation – Processes – Ion exchange or selective sorption
Patent
1993-04-02
1995-03-14
Cintins, Ivars
Liquid purification or separation
Processes
Ion exchange or selective sorption
210677, 210263, 423584, B01D 1504
Patent
active
053974751
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process and apparatus for the purification of aqueous hydrogen peroxide solutions and in particular to the removal from solution of ionic metals to very low residual concentrations.
Chemicals for use in the manufacture of semiconductors, integrated circuits and the like and in related electronics industries need to be very pure, otherwise there is a risk that their use will introduce harmful or otherwise undesirable impurities onto or into the semiconductors, integrated circuits and the like, with potentially damaging operational difficulties. The industries are continuing to set ever higher standards of purity, so that products which even 5 to 10 years ago could meet the subsisting standards would no longer do so. Accordingly, there is a continuing need to develop improved purification techniques.
Aqueous hydrogen peroxide solutions are used in cleaning, stripping or etching operations. The existing commercial methods for manufacturing hydrogen peroxide in bulk, such as the hydrolysis of a persulphuric acid and, more commonly, the successive hydrogenation and oxidation of a substituted alkylanthroquinone in a suitable solvent system both produce a product that can contain high levels of impurities including cationic metals and other impurities. Pure grades that are suitable for other uses can be obtained by distillation which effects a partial purification, but the residual concentrations of metals are normally still too high for the product to meet the purity standards of the electronics industries. Accordingly, it is accepted within the industry that alternative or additional purification techniques are required for electronic grade material.
There is one further complication which a prudent manufacturer of an electronic grade hydrogen peroxide solution must take into account. When hydrogen peroxide decomposes, it does so exothermically and accordingly the temperature of its immediate environment is increased. Its rate of decomposition increases as the reaction temperature increases, in conformity with the teaching of Arrhenius. This can result in a self-accelerating reaction, terminating in an explosion. Transition metal ions comprise a principal cause of hydrogen peroxide decomposition and it will be recognised that these ions often represent a significant fraction of the impurities that it is desired to remove from the hydrogen peroxide solution.
It is self-evident that ions may be removed from impure aqueous hydrogen peroxide solutions by passage through a bed of an ion exchange resin, at least in theory. However, the conventional ion-exchange technique of a liquid being passed relatively slowly under pressure through a fixed bed of a solid ion-exchanger results in the metal ions being concentrated on the resin, and in contact with the hydrogen peroxide in a confined space. Such a technique is not only potentially dangerous, but has also resulted in a number of "incidents", namely explosions which destroyed the apparatus and threatened the safety of any process operator that was unfortunate enough to be in the vicinity. It was hypothesised subsequently that the incidents had arisen as a result of the metal ions catalysing localised peroxide decomposition, which led to a localised self-accelerating reaction, followed by decomposition which then spread to the remainder of the liquid phase.
It has been suggested by Wako Junyaku Kogyo in Japanese Patent Application Kokai 62-187103 that safety could be improved by pretreating the resin in a certain manner, but safety is such an important matter that it remains of great benefit to devise alternative or complementary operating procedures and apparatus. Accordingly, it was an object of the present programme of research into purification processes to devise processes and apparatus for purifying hydrogen peroxide solutions in which the risk of plant destruction was either eliminated or at least significantly reduced.
One comparatively safe purification technique has been described by Interox Chemicals in PCT application no P
REFERENCES:
patent: 1671864 (1928-05-01), Higgins
patent: 2366007 (1944-12-01), D'Alelio
patent: 2676923 (1954-04-01), Young
patent: 3074782 (1963-01-01), Meeker et al.
patent: 3174927 (1965-03-01), Cross et al.
patent: 3436343 (1969-04-01), Smith
patent: 4132762 (1979-01-01), Kim
Chemical Abstracts, vol. 69, No. 14, 30 Sep. 1968, (Columbus, Ohio), p. 4990, abstract 53300d, & PL, B, 55378 (Zaklady Elektrochemiczne "Zabkowice").
Crampton John R.
Hardy Francis R. F.
Millar Malcolm H.
Morris Gareth W.
Cintins Ivars
Interox Chemicals Limited
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