Process for the production of hydrogen peroxide
The invention relates to a process for the production of hydrogen peroxide by the anthraquinone process, comprising a hydrogenation stage, an oxidation stage and an extraction stage. According to the invention, catalytic hydrogenation of anthraquinone derivatives dissolved in a working solution is carried out in the presence of added molecular oxygen. Per mol hydrogen, 0.1 to 10 mmol oxygen is preferably introduced into the hydrogenation stage with the hydrogenating gas, in mixture with an inert gas and/or dissolved and/or dispersed in the working solution. This increases the residence time of the catalyst.
1. In a process for the production of hydrogen peroxide, comprising:
a) a hydrogenation stage reaction comprising the hydrogenation of an anthraquinone derivative with a hydrogen-containing gas in the presence of a hydrogenating catalyst to form an anthrahydroquinone derivative, said anthraquinone derivative and anthrahydroquinone derivative being contained within a working solution;
b) an oxidation stage reaction comprising the reconversion of said anthrahydroquinone of step a) back to said anthraquinone derivative using an oxygen-containing gas, said reconversion being accompanied by the formation of hydrogen peroxide; and
c) an extraction stage comprising isolating said hydrogen peroxide formed in step b) and then returning the working solution to said hydrogenation stage reaction,
the improvement comprising adding molecular oxygen (O 2 ) in the form of a gas containing molecular oxygen as a component to said hydrogenation stage reaction in a quantity of at least 0.02 mmol O 2 per mole H 2 and less than the explosion limit under the hydrogenation conditions.
2. The process of claim 1 , wherein said molecular oxygen is added to said hydrogenation step reaction in a form selected from the group consisting of: O 2 alone; air alone; O 2 or air in mixture with said hydrogen-containing gas of said hydrogenation stage reaction; and O 2 or air in mixture with an inert gas.
3. The process of claim 1 , wherein said molecular oxygen is added to said hydrogenation stage reaction in a quantity of 0.1 to 20 mmol O 2 per mole of hydrogen.
4. The process of claim 3 , wherein molecular oxygen is added in a quantity of 0.5 to 10 mmol of O 2 per mole of hydrogen.
5. The process of claim 1 , wherein said hydrogen-containing gas in said hydrogenation stage reaction has an oxygen content of 100 vpm (volume parts per million) to 5000 vpm.
6. The process of claim 1 , wherein said hydrogenation stage reaction is carried out in a fixed bed reactor with an LHSV (liquid hourly space velocity) of 0.1 h −1 to 20 h −1 .
7. The process of claim 1 , wherein a precious metal-containing fixed bed catalyst of particles having an average diameter of 0.5–20 mm is used for said process.
8. The process of claim 7 , wherein said fixed bed catalyst contains palladium.
9. The process of claim 6 , wherein said fixed bed reactor is operated as a trickle bed.
10. The process of any one of claim 1 – 9 , wherein, after the isolation of said hydrogen peroxide in said extraction stage, said working solution is brought into contact with said molecular oxygen or gas containing molecular oxygen before being returned to said hydrogen stage reaction.
11. The process of any one of claims 1 – 9 , wherein said molecular oxygen or gas containing molecular oxygen is added directly to a reactor in which said hydrogenation stage reaction is taking place, said addition occurring after the isolation of said hydrogen peroxide, and wherein said addition is made in a quantity of 0.1 to 20 mmol of O 2 per mole of hydrogen.