Direct synthesis of hydrogen peroxide by heterogeneous catalysis

Details Direct synthesis of hydrogen peroxide by heterogeneous catalysis Direct synthesis of hydrogen peroxide by heterogeneous catalysis

1993-10-04

1995-09-05

Langel, Wayne

Chemistry of inorganic compounds

Oxygen or compound thereof

Peroxide

502213, 502217, B01J 27053, C01B 1501

Patent

active

054477069

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a method for direct synthesis of hydrogen peroxide from hydrogen and oxygen. It more particularly concerns a method for synthesis of hydrogen peroxide by heterogeneous catalysis.


FIELD OF THE INVENTION

It also relates to a catalyst for the said method as well as a method for manufacture of this catalyst.


TECHNOLOGY REVIEW

It is known by Patent Application EP-A2-0,274,830 (du Pont de Nemours) to synthesize hydrogen peroxide by direct reaction of hydrogen with oxygen in the presence of a solid metal catalyst chosen from palladium, platinum or a combination of these two metals in an acidic aqueous reaction mixture containing bromide as a promoter or inhibitor of decomposition of the peroxide formed. The metal of the catalyst can be supported on an appropriate support chosen from carbon, silica, alumina or ion exchange resins.
In Patent Application EP-A2-0,342,047 (dupont de Nemours), it is furthermore disclosed that it is advantageous for the acid and bromide ion concentrations to lie, independently of each other, between 0.001 M and 0.05 M.
It is also disclosed in U.S. Pat. No. 4,832,938 (du Pont de Nemours) that the Pt/(Pt+Pd) ratio by weight should preferably be in the range from 0.02 to 0.2.
In all these known methods, the selectivity of the reaction with respect to the reactants and, in particular, with respect to the hydrogen used, is not very high and generally lies between 50 and 70% molar. In the best of these cases, it never exceeds 77% molar. Now, as regards the economics of the method, the cost of the hydrogen plays an important part in the cost price of the hydrogen peroxide produced. Moreover, it is not uncommon for the support of the catalyst to be partially dissolved in the acidic reaction mixture.


SUMMARY OF THE INVENTION

The subject of the present invention is a method of direct synthesis of hydrogen peroxide from hydrogen and oxygen which does not have the disadvantages of the known methods.
For this purpose, the invention relates to a method for direct synthesis of an aqueous solution of hydrogen peroxide from hydrogen and oxygen by heterogeneous catalysis in a three-phase system, according to which hydrogen and oxygen are directly reacted in the gaseous state and at a pressure greater than atmospheric pressure, at the surface of a solid heterogeneous catalyst suspended in the granular state in a liquid aqueous phase, the catalyst consisting of a metal compound chosen from pure palladium or a combination of palladium with at least one other noble metal, and the metal compound being impregnated on a support comprising at least one compound chosen from the sulphates or the phosphates of alkaline-earth metals.


DETAILED DESCRIPTION OF THE INVENTION

Direct synthesis of an aqueous solution of hydrogen peroxide is intended to designate the synthesis of solutions of H.sub.2 O.sub.2 in water from its elements, namely oxygen and hydrogen. According to the invention, these two reactants are used in regulated conditions of temperature and pressure so that they are in the gaseous state, the pressure chosen being however greater than atmospheric pressure.
The catalyst in accordance with the method according to the invention belongs to the class of solid catalysts used in heterogeneous catalysis, that is to say a catalysis which acts at the interface between the catalytic solid and one or more other phases containing the reactants. According to the invention, the solid catalyst is maintained in suspension in the form of granules in a liquid aqueous phase capable of collecting and solubilizing the hydrogen peroxide formed. The two gaseous reactants, oxygen and hydrogen, are put in contact with the catalyst in suspension in the solution. The catalyst moreover consists of pure palladium or, in an alternative way which is not preferred, of a combination of palladium with another noble metal. The palladium or the combination of palladium is furthermore impregnated on a support consisting of a sulphate or a phosphate of an alkaline-earth metal. Pure palladium is int

REFERENCES:
patent: 2418851 (1947-04-01), Rosenblatt et al.
patent: 4007256 (1977-02-01), Kim et al.
patent: 4279883 (1981-07-01), Izumi et al.
patent: 4661337 (1987-04-01), Brill
patent: 4832938 (1989-05-01), Gosser et al.

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