Liquid purification or separation – Processes – Ion exchange or selective sorption
Patent
1991-10-01
1993-11-16
Cintins, Ivars
Liquid purification or separation
Processes
Ion exchange or selective sorption
210688, B01D 1500
Patent
active
052620581
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to processes for the purification of hydrogen peroxide solutions and particularly to the production of solutions in which metallic impurity contents have been reduced to very low levels.
Aqueous hydrogen peroxide solutions are currently made or have been proposed to be made by a variety of different techniques. These include electrolytic techniques often involving hydrolysis of persulphuric acid or a salt thereof, autoxidation techniques in which a carrier, typically an alkyl-substituted anthraquinone, is subjected cyclically to reduction with hydrogen, oxidation with air and extraction of hydrogen peroxide with water and more recently processes involving the direct oxidation of hydrogen with oxygen in the presence of certain catalysts and under selected conditions.
Many variations of the foregoing manufacturing techniques are known. After the aqueous hydrogen peroxide solutions have been formed, they can be concentrated and purified to some extent by water removal or distillation techniques. Although the hydrogen peroxide manufacturing techniques differ markedly in their operation, they share the common result that the aqueous hydrogen peroxide solution obtained, even after distillation, contains significant amounts of residual impurities, including in particular a number of metal ions.
Although there has always been a desire to obtain aqueous hydrogen peroxide solutions of high purity, a qualitative term, the use of hydrogen peroxide in the semiconductor and allied electronics industries has imposed new and increasingly stringent, quantitative standards on the term in recent years. This is because such industries have demanded since their inception lower levels of residual impurities that could remain in peroxide solutions than were tolerable for other purposes, but also because their purity specifications have become increasingly tight, especially noticeably during the period of 1985 to date. It is convenient to call hydrogen peroxide solutions which meet 1988/9 impurity standards as ultra-pure so as to distinguish them from the state of the art products of former eras, which tolerated much higher impurity levels.
It is recognised that various techniques have already been proposed or used for the purification of hydrogen peroxide solutions and these include distillation and related water-removal techniques. These can be especially useful for the removal of organic impurities, such as compounds employed in autoxidation manufacturing methods, but are of lesser value for removing inorganic ions like metals or acidic anions in that they tend to remain to a greater or lesser extent in the aqueous hydrogen peroxide rather than being carried out in the distillate water.
More recently, an alternative purification technique has been suggested which comprises passing an impure aqueous hydrogen peroxide solution through a bed of certain types of ion exchange resins that are preferably in acid form. Such a technique is described, for example in Japanese Kokai 62-187103 (1987) to Wako Junyaku KK. This technique is capable of removing metal ion impurities, but the extent of its effectiveness brings with it, inevitably, a corresponding increase in the probability of an explosion when employing the technique to purify high concentrations of hydrogen peroxide in commercial quantities. The increased risk runs hand in hand with its effectiveness at purification because the initial action of the ion exchange resin removing the impurity levels of, in particular, transition metal ions such as copper, iron, chromium, vanadium etc, from solution is to concentrate them in and on the surface of the ion exchange resin. Such metals are well-known decomposition agents for hydrogen peroxide. This means that the hydrogen peroxide in the solution being purified is now brought into contact with a surface that carries concentrated decomposition catalysts. The risk is automatically increased of a localised decomposition of hydrogen peroxide occurring which increases the temperature locally, thereby further p
REFERENCES:
patent: 2017440 (1935-10-01), Hawkinson
Feasey Neil D.
Morris Gareth W.
Cintins Ivars
Interox Chemicals Limited
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