Sodium percarbonate
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| General | |||||||||||||||||||
| Surname | Sodium percarbonate | ||||||||||||||||||
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| Molecular formula | 2 Na 2 CO 3 • 3 H 2 O 2 | ||||||||||||||||||
| Brief description |
colorless and odorless, oxidizing powder |
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| properties | |||||||||||||||||||
| Molar mass | 314.02 g · mol -1 | ||||||||||||||||||
| Physical state |
firmly |
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| density |
2.14 g cm −3 |
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| Melting point |
Decomposition at approx. 60 ° C |
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| solubility |
easily soluble in water (150 g l −1 at 20 ° C) |
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| As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . | |||||||||||||||||||
Sodium percarbonate (2 Na 2 CO 3 · 3 H 2 O 2 ) is an addition compound ( adduct ) of hydrogen peroxide H 2 O 2 with sodium carbonate ( soda , Na 2 CO 3 ).
history
Sodium percarbonate (PCS) has been known since 1899. As a bleaching agent in washing powders, it could not prevail against the chemically more resistant sodium perborate . Only during the First and Second World Wars, when boron minerals were scarce, was there any significant production in Germany. After the Second World War, PCS remained a niche product for denture cleaners and stain removers. It was not until the beginning of the 1990s that new coating processes (coating of the PCS crystals) increased the shelf life and made sodium percarbonate a marketable bleach .
Extraction and presentation
Sodium percarbonate is industrially produced using a dry spray granulation process or a wet crystallization process. Both processes are based on the addition of hydrogen peroxide to sodium carbonate:
In the classic wet process, a sodium carbonate solution is mixed with hydrogen peroxide and crystallized sodium percarbonate is centrifuged off by cooling. It is then dried to the desired residual moisture in a fluidized bed dryer.
In the dry spray granulation process, a sodium carbonate and a hydrogen peroxide solution are sprayed together onto a fluidized bed of small sodium percarbonate seed crystals through which warm air flows, and crystallized. The resulting moisture is carried away with the air.
Both processes can be operated continuously. Unreacted raw materials are returned to the reaction space. Compared to the spray granulation process, the energy requirement in the wet process is lower due to the pre-separation of the dissolving water (mother liquor) before drying. The slightly more structured surface of the crystals produced in the wet process has a positive effect on the production of dishwasher or detergent tabs. Typical impurities in technical grade sodium percarbonate are sodium carbonate (<15%), sodium sulfate (<10%) and sodium chloride (<5%).
In 2004, the production capacity in the EU-25 was almost 500,000 tons. This makes it one of the chemical substances that are produced in large quantities (" High Production Volume Chemical ", HPVC) and for which the Organization for Economic Cooperation and Development (OECD) collects data on possible dangers (" Screening Information Dataset ", SIDS).
properties
Sodium percarbonate forms colorless crystals that dissolve well in water , the solution is strongly alkaline. The solid is irritating and corrosive. Under the influence of heat, the hydrogen peroxide is split off again from 50 ° C and further breaks down into water and active oxygen . The rate of reaction increases with increasing temperature.
use
Sodium percarbonate as a bleaching agent and oxidizing agent is ecologically safer than sodium perborate , which was widely used in the past , because it does not contain boron . In contrast to sodium perborate, sodium percarbonate is non-toxic to plants. Sodium percarbonate is a component of many detergents and dishwasher detergents. During the cleaning process, it releases oxygen from 60 ° C, which removes bleachable stains (including from tea, red wine, grass or fruit). The dyes are oxidized and therefore colorless, in some cases stain-forming substances are even converted into water-soluble substances and removed with the washing liquor. If the effect is to start at temperatures below 60 ° C or 50 ° C, a bleach activator is added to the cleaning agent .
In addition to various surfactants and enzymes, sodium percarbonate is the main active ingredient in many household detergents with a bleaching effect, which are advertised with terms such as "active oxygen" or the prefix "Oxi".
Individual evidence
- ↑ Entry on SODIUM CARBONATE PEROXIDE in the CosIng database of the EU Commission, accessed on April 17, 2020.
- ↑ a b c d Entry on disodium carbonate, compound with hydrogen peroxide (2: 3) in the GESTIS substance database of the IFA , accessed on February 8, 2017(JavaScript required) .
- ↑ a b c OECD : Screening Information Dataset (SIDS) Initial Assessment Report (SIAR) for Disodium carbonate, compound with hydrogen peroxide (2: 3) , accessed on October 3, 2014.
- ↑ a b Hansagroup: Safety data sheet