Patent EA-004475-B1 (EA)
Title: Supported metal catalyst, preparation and applications for directly making hydrogen dioxide
Inventor: DEVIC MICHEL
IPC: B01J23/44
Filed: 2000-06-07
Abstract: 1. A method for making a supported metal catalyst based on at least two metals selected in the group M consisting of palladium, platinum, ruthenium, rhodium, iridium, holmium, osmium and gold, comprising successively an impregnating step with a solution based on one or several salt(s) of at least two metals of group M on a support, and a reduction step characterised in that at the end of the reduction step, the catalyst is treated with an aqueous acid solution (A) comprising bromine and bromide ions. 2. The method according to claim 1, characterized in that the concentration of bromide ions in the aqueous acid solution (A) ranges between 2 to 20 mg/l, preferably 2 to 10 mg/l. 3. The method according to claim 1 or 2, characterized in that the concentration of bromine in the aqueous acid solution (A) ranges between 20 to 200 mg/l, preferably 20 to 100 mg/l. 4. The method according to one of claims 1-3, characterized in that pH the aqueous acid solution (A) ranges between 1 to 3. 5. The method according to one of claims 1-4, characterized in that the treatment temperature ranges between 10 to 80 degree C, preferably between 40 to 60 degree C. 6. The method according to one of claims 1-5, characterized in that after said treatment a solid catalyst substance is separated from the solution (A) and dried at 100 to 140 degree C. 7. The method according to one of claims 1-6, characterized in that after impregnation step and before reduction step the resultant suspension is filtered, drained and finally dried. 8. The method according to claim 7, characterized in that the drying step is performed under conditions favored for slow crystallization. 9. The method according to any one of claims 1-8, characterized in that palladium and gold are preferably selected as metals. 10. The method according to one of claims 1-9, characterized in that a catalyst is a supported bimetal catalyst, in which a minor metal constitutes 0.001 to 0.1 wt % from a catalyst. 11. The method according to claim 10, characterized in that the minor metal is platinum. 12. The method according to 5one of claims 1-11, characterized in that the support is silicon dioxide having specific BET area surface preferably greater than 200 m<2>/g. 13. A supported metal catalyst based on at least two metals selected in the group M consisting of palladium, platinum, ruthenium, rhodium, iridium, holmium, osmium and gold, in which a metal content is from 0.1 to 10 wt % of the catalyst, characterized in that crystallised metal aggregates range between 0.1 and 20 microns and preferably between 0.1 and 10 microns in size. 14. The catalyst according to claim 13, characterized in that, characterized in that palladium and gold are preferably selected as metals. 15. The catalyst according to claim 13, characterized in that the catalyst is a supported bimetal catalyst, in which a minor metal constitutes 0.001 to 0.1 wt % from the catalyst. 16. The catalyst according to claim 15, characterized in that the minor metal is platinum. 17. The method according to one of claims 13-16, characterized in that the support is silicon dioxide having specific BET area surface preferably greater than 200 m<2>/g. 18. A method for directly making hydrogen peroxide from hydrogen and oxygen, characterized by using a catalyst prepared according to one of claims 1-12 or a catalyst according to one of claims 13-17.