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Hydrogen Peroxide

已有 4783 次阅读 2011-10-20 10:13 |个人分类:科海漫游|系统分类:科研笔记| normal, style, color, class, target

H2O2-wikipedia

Stability and decomposition of H2O2

The property of hydrogen peroxide to decompose exothermally in the presence of certain catalytically acting impurities, with the formation of oxygen gas and water is very important for handling during storage as well as during chemical reaction. Decomposition is indicated by the development of gas and—with only slight removal of heat—by rise in temperature.

The stability of hydrogen peroxide solutions is influenced primarily by the temperature, the pH value, and above all by the presence of impurities with a decomposing effect.

An increase in the temperature promotes the decomposition as well as a higher pH value. For optimum stability, the pH range of pure H2O2 is below 4.5. Above pH 5, the decomposition increases sharply. Therefore, commercial solutions are generally adjusted to a pH value below 5.

The shelf life of hydrogen peroxide is negatively affected by impurities of every type even when some of these impurities are present in very low concentrations (ppm quantities). The decomposition can be induced homogeneously by dissolved ions with a catalytic effect. Heavy metals like iron, copper, manganese, nickel, and chromium are especially effective here. Hydrogen peroxide is also decomposed through the effect of light as well as by certain enzymes (catalase).

As a result of the stabilizers, which are usually added to our commercial grades in ppm amounts, our hydrogen peroxide is protected against unavoidable impact during handling and has an excellent shelf life. With normal handling and cool storage, and when the necessary precautionary measures are observed, the losses of hydrogen peroxide are very slight even during extended periods (years) of storage.

http://h2o2.evonik.com/product/h2o2/en/about/stability-decomposition/pages/default.aspx


Stability and decomposition. The decomposition of hydrogen peroxide to form. oxygen and water with the evolution of heat is expressed by the equation:
2H2O2(l)␣2H2(I) + O2(g) + 1240 BTU/lb of 100% H2O
Commercial grades of hydrogen peroxide are quite stable, typically losing less than 1% relative strength per year. At this rate, the heat of decomposition is dissipated readily to the surroundings, and the hydrogen peroxide remains at ambient temperature. However, several factors can increase the normally slow rate of hydrogen peroxide decomposition. The consequences of a rate increase can range from a deterioration of product concentration over a period of days or weeks, to a runaway reaction generating large amounts of heat and gas (oxygen and steam) at worst. The worst case scenario can lead to serious safety incidents including pressure bursts of vessels or pipes, fires due to spilled hydrogen peroxide, and personal injuries. The primary factors which must be controlled to prevent an increased rate of hydrogen peroxide decomposition are temperature, contamination and pH.
The temperature of the hydrogen peroxide solution is an important variable, since the decomposition rate is roughly doubled by every 10°C increase. Given the heat generated by decomposition, a self accelerating reaction can evolve if heat transfer to the surroundings is slower than the rate of heat generation. Hydrogen peroxide storage facilities and piping should be located well away from heat sources such as boilers, steam lines, etc. Storage of hydrogen peroxide in insulated vessels should be avoided.
Contamination of hydrogen peroxide solutions is a second major cause of accelerated decomposition, since many common materials act as catalysts for the decomposition reaction. Some contaminants can create rapid decomposition of hydrogen peroxide if present even in concentrations as low as 0.1 part per million. Homogeneous decomposition is prompted by dissolved contaminants such as alkalis, strong acids and salts of transition metals (nickel, chromium, copper, iron, etc.). Homogeneous decomposition is most frequently started when another chemical is erroneously put into a hydrogen peroxide vessel (or vice versa) or by process fluid back flow through a poorly designed or malfunctioning hydrogen peroxide feed system.
Heterogeneous decomposition of hydrogen peroxide is localised on the surface of solid catalytic contaminants, usually metals. Contact of hydrogen peroxide with improper materials of construction (copper, brass, zinc, mild steel, etc.) is a primary cause of heterogeneous decomposition. The accidental introduction of debris, such as tools, flash lights and so forth, into storage vessels is an all too frequent cause of heterogeneous decomposition.
Commercial grades of hydrogen peroxide contain stabilizers which chelate small amounts of impurities, providing protection against the effects of minor levels of contamination. Unfortunately, stabilizers are ineffective in dealing with gross contamination by decomposition catalysts.
The inherent stability of hydrogen peroxide is also affected by pH. Chart One shows the pH of high purity hydrogen peroxide. Stability is normally best in the region of neutral real pH. The normally measured pH (apparent pH) is affected by hydrogen peroxide concentration. The decrease of stability at lower pH is not normally large, but at higher pH, the stability deteriorates very rapidly, and alkaline hydrogen peroxide may be very unstable. Contamination of hydrogen peroxide by acids and particularly alkalis must therefore be avoided.

http://answers.yahoo.com/question/index?qid=20100713191350AAV1LCT

This is an interesting webpage. However, no much information is presented.

http://www.h2o2-4u.com/tech.html

A brief introduction to H2O2

http://www.brightenyourfuture.com/pdf/en/Hydrogen_peroxide.pdf

Infrared Spectra and Radiation Stability of H2O2 Ices Relevant to Europa(木卫二)

http://astrobiology.gsfc.nasa.gov/H2O2-Astrobiology.pdf



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