Aqueous hydrogen peroxide solutions and method of making same
An aqueous hydrogen peroxide solution containing i) less than 50 wppm alkali metals, alkaline earth metals or combinations thereof in total, irrespective whether the alkali or alkaline earth metals are present in cationic or complex form; ii) less than 50 wppm of amines having a pk B of less than 4.5 or the corresponding protonated compounds in total; and iii) at least 100 wppm anions or compounds that can dissociate to form anions in total, where the wppm are based on the weight of hydrogen peroxide and the concentration of hydrogen peroxide is more than 50% by weight based on the total weight of the hydrogen peroxide solution. A process for preparation of said hydrogen peroxide solution and the use of said solution in a process for epoxidation of olefins is also disclosed.
1. An aqueous hydrogen peroxide solution comprising:
less than 50 wppm alkali metals, alkaline earth metals or combinations thereof in total, irrespective whether the alkali metals or alkaline earth metals are present in cationic or complex form;
less than 50 wppm of amines having a pk B of less than 4.5 or the corresponding protonated compounds in total; and
at least 100 wppm anions or compounds that can dissociate to form anions in total,
the wppm being based on the weight of hydrogen peroxide,
wherein the concentration of hydrogen peroxide is more than 50% by weight based on the total weight of the hydrogen peroxide solution.
2. The aqueous hydrogen peroxide solution of claim 1 , wherein the concentration of hydrogen peroxide is more than 60% by weight based on the total weight of the hydrogen peroxide solution.
3. The aqueous hydrogen peroxide solution of claim 1 , wherein the concentration of hydrogen peroxide is from 60 to 70% by weight by weight based on the total weight of the hydrogen peroxide solution.
4. A process for the preparation of a hydrogen peroxide solution according to the anthraquinone loop process, said process comprising:
a) hydrogenating a working solution comprising an organic solvent or mixture of organic solvents and one or more active anthraquinone compounds to obtain a hydrogenated working solution,
b) oxidizing the hydrogenated working solution to form hydrogen peroxide,
c) extracting hydrogen peroxide with water to obtain extracted aqueous hydrogen peroxide solution,
d) stabilizing the extracted aqueous hydrogen peroxide solution,
e) concentrating the aqueous hydrogen peroxide solution to a concentration of hydrogen peroxide of at least 50% by weight based on the weight of the hydrogen peroxide solution to obtain a concentrated aqueous hydrogen peroxide solution comprising:
i) less than 50 wppm alkali metals, alkaline earth metals or combinations thereof in total, irrespective whether the alkali or alkaline earth metals are present in cationic or complex form;
ii) less than 50 wppm of amines having a pk B of less than 4.5 or the corresponding protonated compounds in total; and
iii) at least 100 wppm anions or compounds that can dissociate to form anions in total,
said wppm being based on the weight of hydrogen peroxide
f) drying the working solution after extracting hydrogen peroxide, and
g) regenerating and purifying the working solution,
whereby during the entire process neither alkali or alkaline earth metals nor amines having a pk B of less than 4.5 or compounds forming such amines during the process are introduced in amounts that result in amounts of
i) 50 wppm or more of alkali metals, alkaline earth metals or combinations thereof in total, irrespective whether the alkali or alkaline earth metals are present in cationic or complex form; or
ii) 50 wppm or more of amines having a pk B of less than 4.5 or the corresponding protonated compounds in total;
in the resulting aqueous hydrogen peroxide solution, said wppm being based on the weight of hydrogen peroxide.
5. The process of claim 4 , wherein
the working solution is essentially free of organic nitrogen compounds,
drying the working solution in step f) is conducted without using alkali or alkaline earth metal compounds, and
regeneration of the working solution in step g) is done by treating with active aluminum oxide.
6. The process of claim 5 , wherein drying is conducted by water evaporation in vacuum.
7. The process of claim 5 , wherein no further purification of the extracted aqueous hydrogen peroxide solution is carried out.
8. The process of claim 6 , wherein no further purification of the extracted aqueous hydrogen peroxide solution is carried out.
9. The process of claim 4 , wherein at least one base having a pk B of at least 4.5 without containing alkali or alkaline earth metals is added in an amount resulting in at least 100 wppm of such bases or corresponding protonated compounds in total based on the weight of hydrogen peroxide in the final aqueous hydrogen peroxide solution.
10. The process of claim 9 , wherein the base is selected from the groups consisting of organic amines and amides having a pk B of at least 4.5, organic hydroxylamines having a pk B of at least 4.5, ammonia and hydroxylamine.
11. The process of claim 10 , wherein the base is ammonia.
12. The process of claim 9 , wherein the base is added either during the preparation of the hydrogen peroxide solution or at any stage between preparation and final use of the hydrogen peroxide solution.