Chemistry of inorganic compounds – Oxygen or compound thereof – Peroxide
Reexamination Certificate
1998-12-22
2001-04-03
Langel, Wayne (Department: 1754)
Chemistry of inorganic compounds
Oxygen or compound thereof
Peroxide
Reexamination Certificate
active
06210651
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a process of producing hydrogen peroxide by direct reaction between hydrogen and oxygen in the presence of a catalyst to form hydrogen peroxide gas.
Production of hydrogen peroxide by direct reaction between hydrogen and oxygen can be performed by contacting hydrogen and oxygen with a catalyst in an aqueous reaction medium as described in, for example, U.S. Pat. Nos. 4,661,337, 4,681,751, 4,772,458, 5,180,573, 5,128,114 and 5,338,531, as well as J. R. Kosak (DuPont), “A Novel Fixed Bed Catalyst for the Direct Combination of H
2
and O
2
to H
2
O
2
”, Chem. Ind. (Dekker), 1995, Vol, 62, Catalysis of Organic Reactions.
However, the formation of hydrogen peroxide in these processes is rather slow. Further, it is hard to obtain high concentrations of hydrogen peroxide and the product will also contain additives in the reaction medium as impurities, such as sulfuric acid and/or bromide or chloride ions. These problems are assumed to be due to the facts that only low amounts of the reactants can be dissolved in the reaction medium and that the same catalyst that promotes formation of hydrogen peroxide also catalyses direct formation of water and peroxide decomposition into water and oxygen.
A similar process conducted in an organic solvent as reaction medium is described in WO 97/32811. However, in order to obtain hydrogen peroxide in aqueous solution a separation step such extraction or desorption is necessary.
DE patent 558431, CH patent 140403, U.S. Pat. No. 2,368,640 and WO 97/32812 disclose production of hydrogen peroxide from hydrogen and oxygen in gas phase. However, unless operating under extreme conditions the selectivity is low: instead of hydrogen peroxide a great deal of the end product will be water.
U.S. Pat. No. 5,500,202 discloses production of hydrogen peroxide in a reactor, wherein hydrogen and oxygen are reacted in a gaseous state at the surface of a solid catalyst and the hydrogen peroxide formed is dissolved in a liquid trickling through the reactor. However, also in this process only hydrogen peroxide solutions of low concentration and low purity can be obtained.
SUMMARY OF INVENTION
It has now been found that it is possible to solve these problems and combine the high reaction rate obtained in gas phase with high selectivity by using a special kind of catalyst.
Thus, the invention relates to a process for continuously producing hydrogen peroxide comprising the steps of feeding hydrogen and oxygen containing gas to a reactor provided with a catalyst; contacting the hydrogen and oxygen gas with the catalyst and thereby forming hydrogen peroxide, and; withdrawing hydrogen peroxide containing gas from the reactor. The free volume of the reactor is thus preferably filled with gas comprising hydrogen, oxygen and hydrogen peroxide, and most preferably also inert gas such as nitrogen. The catalyst comprises a solid catalytically active material at least partially covered with a layer of a stationary phase different from the catalytically active material. The stationary phase suitably has a thickness from a mono-atomic or mono-molecular layer up to about 100 &mgr;m, preferably from about 0.002 up to about 25 &mgr;m, most preferably from about 0.004 up to about 5 &mgr;m. These ranges refer to the mean value of the thickness of the stationary phase, which, for example, can be measured by repeated sputter analysis or be calculated from the formula m/(&rgr; s) where m is the weight of the stationary phase, &rgr; is the density of the stationary phase and s is the total surface of the substrate (normally the BET surface). If direct measurement of the thickness for some reason is impossible, Preferably, the stationary phase covers substantially all the active sites of the catalytically active material.
REFERENCES:
patent: 2368640 (1945-02-01), Cook et al.
patent: 4369128 (1983-01-01), Moseley et al.
patent: 4661337 (1987-04-01), Brill
patent: 4681751 (1987-07-01), Gosser
patent: 4772458 (1988-09-01), Gosser et al.
patent: 5128114 (1992-07-01), Schwartz
patent: 5180573 (1993-01-01), Hiramatsu et al.
patent: 5338531 (1994-08-01), Chuang et al.
patent: 5500202 (1996-03-01), Germain et al.
patent: 140403 (1930-08-01), None
patent: 558431 (1932-09-01), None
patent: 0 498 166 A1 (1992-08-01), None
patent: 0 878 235 A1 (1998-11-01), None
patent: WO 97/32812 (1997-09-01), None
patent: WO 97/32811 (1997-09-01), None
“A Novel Fixed Bed Catalyst for the Direct Combination of H2 and O2 to H202”, Catalysis of Organic Reactions, by John R. Kosak. Chemical Independence (Dekker), vol. 62, 1995 pp. 115-124, (no month).
Herrmann Wolfgang
Nystrom Mats
Wanngard Johan
Akzo Nobel N.V.
Langel Wayne
Serbin David J.
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