Interox International (societe Anonyme)

Solvay Interox (societe Anonyme)

Solvay Interox Sa

Lido Signorini

Alun P James

Graham R Horne

Manfred Mathes

Richard Roesler

Soraya Parvaneh

Romano Pardini

Stefano Bigini

Pier-Luigi Deli

Robert Owen

Uwe Droste

Konstantin Glinos

Philippe Deroisy

Fabienne Banneux

Sodium percarbonate is traditionally made in a crystallization process from aqueous hydrogen peroxide and sodium carbonate with recycle of mother liquor in the presence of a substantial concentration of a salting out agent, conventionally sodium chloride. The invention provides a process intended to be conducted without addition of chloride salting-out agent in which the dissolution step is controlled to restrict the sodium carbonate concentration to below 95%, preferably 60 to 90% of its saturated concentration at a temperature preferably controlled to at most 35C. and the mole ratio of hydrogen peroxide:sodium carbonate in the reaction vessel is controlled to between 0.7 to 1.2:1, and preferably about 1:1. In some embodiments at least a fraction of the mother liquor introduced into the dissolution tank is obtained by extraction from the reaction vessel and in other embodiments a fraction of the sodium percarbonate is introduced in solution in the mother liquor and a fraction is introduced in particulate form directly into the reaction vessel. Large particle sodium percarbonate is provided which has a 7 day aged heat emission at 40C. of not more than 3 &mgr;W/g measured in a microcalorimeter over 16 hours that is lower than the heat emission from conventionally produced sodium percarbonate employing a chloride salting-out agent.

Sodium percarbonate and process for producing sodium percarbonate

Sodium percarbonate is traditionally made in a crystallization process from aqueous hydrogen peroxide and sodium carbonate with recycle of mother liquor in the presence of a substantial concentration of a salting-out agent, conventionally sodium chloride. The invention provides a process intended to be conducted without addition of chloride salting-out agent in which the dissolution step (,) is controlled to restrict the sodium carbonate concentration to below 95%; preferably 60 to 90% of its saturated concentration at a temperature preferably controlled to at most 35&deg; C. and the mole ratio of hydrogen peroxide: sodium carbonate in the reaction vessel is controlled to between 0.7 to 1.2:1, and preferably about 1:1. In some embodiments at least a fraction of the mother liquor introduced into the dissolution tank (,) is obtained by extraction from the reaction vessel (,) and in other embodiments a fraction of the sodium percarbonate (,) is introduced in solution in the mother liquor (,) and a fraction is introduced in particulate form (,) directly into the reaction vessel (,). Large particle sodium percarbonate is provided which has a 7 day aged heat emission at 40&deg; C. of not more than 3 &mgr;W/g measured in a microcalorimeter over 16 hours that is lower than the heat emission from conventionally produced sodium percarbonate employing a chloride salting-out agent.

Process for producing sodium percarbonate

Process for obtaining aqueous hydrogen peroxide solutions by the alkylanthraquinone process, providing a concentrated aqueous hydrogen peroxide solution with a low content of impurities, according to which a continuous addition of acidifying compounds and/or of stabilising compounds is performed, consisting in recycling towards the oxidation unit at least a part of the purge leaving the distillation unit.

Process for obtaining aqueous hydrogen peroxide solutions

Process for obtaining purified hydrogen peroxide solutions, consisting in evaporating the crude aqueous hydrogen peroxide solution containing the impurities and feeding by means of the vapour phase produced the foot of a distillation column provided in its lower part with a zone for washing the vapour phase with a small flow of liquid which refluxes in the bottom of the column and which has the same composition as the purified aqueous hydrogen peroxide solution forming the product leaving the column, in drawing off this purified product at a column height such that the draw-off is carried out above the vapour phase washing zone and in collecting at the bottom of the column a residue consisting of the small flow of washing liquid which contains most of the impurities. The washing zone has a diameter which is greater than that of the remainder of the column. Distillation column for carrying out the process.

Process for obtaining purified aqueous hydrogen peroxide solutions

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