Hydrophobic multicomponent catalyst useful for direct...

Details Hydrophobic multicomponent catalyst useful for direct... Hydrophobic multicomponent catalyst useful for direct...

2000-01-19

2002-02-12

Griffin, Steven P. (Department: 1754)

Chemistry of inorganic compounds

Oxygen or compound thereof

Peroxide

C502S004000, C502S071000, C502S077000, C502S304000, C502S307000, C502S308000, C502S310000, C502S313000, C502S314000, C502S316000, C502S318000, C502S321000, C502S322000, C502S327000, C502S329000, C502S331000, C502S332000, C502S333000, C502S334000, C502S335000, C502S336000, C502S337000, C502S338000, C502S339000, C502S349000, C502S352000, C502S355000

Reexamination Certificate

active

06346228

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a novel hydrophobic multicomponent catalyst useful in the direct oxidation of hydrogen to hydrogen peroxide and to method for the preparation of such catalyst. More particularly, this invention relates to a novel hydrophobic multicomponent catalyst comprising a hydrophobic polymer membrane deposited on a Pd containing acidic catalyst, useful for the direct oxidation of hydrogen by oxygen to hydrogen peroxide, and a method for the preparation thereof. The present invention also envisages direct oxidation of hydrogen to hydrogen peroxide in the presence of the novel catalyst of the present invention.
The hydrophobic catalyst of the invention has a great potential utility in the chemical and petrochemical industries for the production of hydrogen peroxide by direct oxidation of hydrogen by oxygen to hydrogen peroxide in an environmentally clean manner.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 1,108,752 of Henkel et al discloses the use of palladium for promoting the formation of hydrogen peroxide and water from a mixture of hydrogen and oxygen. Since then, there are numerous disclosures of palladium containing catalysts useful for the direct oxidation of hydrogen by oxygen to hydrogen peroxide.
Hydrophilic Catalysts for the Direct Oxidation of Hydrogen by Oxygen to Hydrogen Peroxide
U.S. Pat. No. 4,832,938 of Grosser et al discloses a Pt—Pd bimetallic catalyst supported on a carbon, silica or alumina support for making hydrogen peroxide from direct combination of hydrogen and oxygen in an aqueous reaction medium. German Patent Ger. Offen. DE 4,127,918 of Lueckoff et al discloses a supported palladium gold catalyst for the manufacture of hydrogen peroxide from hydrogen and aqueous medium, the catalyst containing 5-95 weight % of Au and supported on carbon. A number of platinum group metal containing catalysts: (1) Pt-Group metal on high surface area support, such as carbon, silica or alumina (Ref. U.S. Pat. No. 5,169,618); (2) Pt-Group catalyst on solid acid carrier (Ref. EP application No. 504,741 A1); (3) Pt-Group element supported on Nb—or Ta oxide (Ref. WO 9,412,428 A1); (4) Sn-modified Pt-Group metals supported on catalyst carriers (ref. EP Application No. 621,235 A1); (5) Pt-Group metal catalyst supported on hydrophilic support (Ref. U.S. Pat. No. 5,399,334) for the oxidation of hydrogen to hydrogen peroxide are known in the prior art.
The above-mentioned Pd- of Pt-Group metal containing catalysts are hydrophilic in nature, and hence the aqueous reaction medium used in the oxidation of hydrogen to hydrogen peroxide over these catalysts is in close contact with the catalyst surface. When the above-mentioned catalysts are used, the selectivity for hydrogen peroxide is drastically reduced because of the close contact between the catalyst and the reaction medium. The hydrogen peroxide, which is formed by the reaction between hydrogen and oxygen on the catalyst and then absorbed in the reaction medium due to the high affinity between hydrogen peroxide and water, is readsorbed on the catalyst from the reaction medium and converted to water and oxygen. Fu et al also disclose that Pd catalysts supported on hydrophobic support are selective towards hydrogen peroxide formation in the oxidation of hydrogen [Ref. Fu et al., Stud. Surf. Sci. Catal., 72 (1992) 33-41].
Hydrophobic Catalysts for Direct Oxidation of H
2
by O
2
to Hydrogen Peroxide
A few Pt-group or Group VIII metal catalysts deposited on hydrophobic support, useful for the oxidation of hydrogen to hydrogen peroxide are also known in the prior art.
Japanese Patent Jpn. Kokai Tokyo Koho JP 01133909 A2 of Kyora discloses a Pt-Group metal catalyst carried on a hydrophobic support such as porous and hydrophobic Teflon. EP 3,660,419 A1 of Chuang discloses a Group VIII metal catalyst deposited on a hydrophobic support for the manufacture of hydrogen peroxide by reacting hydrogen with oxygen in an aqueous medium. Intl. Appl. WO 9314025 A1 of Chuang discloses a Group VIII metal on a partially hydrophobic and partially hydrophilic support, such as Pd on fluorinated carbon, as a catalyst for the oxidation of hydrogen to hydrogen peroxide.
Although the hydrophobic support used in these catalysts provides some hydrophobic character to the Pd—or Group VIII metal catalysts, they also suffer from various disadvantages and limitations. It is difficult to deposit catalytically active components from aqueous solution on a hydrophobic support as there is no wetting of the surface of the hydrophobic support by the aqueous solution. Another disadvantage is that hydrophobic supports such as Teflon or other hydrophobic polymer supports are thermally unstable at the calcination temperatures that are normally employed for decomposing the precursor compounds of catalytically active components of the catalyst. Yet another disadvantage is that the hydrophobic character of the support is lost at least partially, if not completely due to the deposition of hydrophilic catalytically active components on the hydrophobic support.
Apart from the above mentioned disadvantages and/or limitations, the prior art catalysts with or without hydrophobic support are employed in the oxidation of hydrogen by oxygen to hydrogen peroxide at a pressure much above the atmospheric pressure. At high pressure, the explosion hazards for the reaction between hydrogen and oxygen are higher.
Thus, there is a need for developing a new catalyst that is active in the direct oxidation of hydrogen to hydrogen peroxide even at atmospheric pressure and also has a hydrophobic character such that the selectivity for the formation of hydrogen peroxide by the reaction of hydrogen and oxygen in an aqueous medium is high.
OBJECTS OF THE INVENTION
It is an object of the invention to provide a novel hydrophobic catalyst useful for the direct oxidation of hydrogen by oxygen to hydrogen peroxide with high selectivity.
It is another object of the invention to provide a novel hydrophobic catalyst useful for the direct oxidation of hydrogen by oxygen to hydrogen peroxide, which has high selectivity even at atmospheric pressure and in an aqueous medium.
It is another object of the present invention to provide a process for the preparation of such novel hydrophobic catalyst for the direct oxidation of hydrogen by oxygen to hydrogen peroxide with high selectivity even at atmospheric pressure and in an aqueous medium.
It is a further object of the invention to provide a novel hydrophobic catalyst comprising PdO in a highly acidic environment created by a solid acid or a solid super acid such that the catalyst shows both high activity and high selectivity in the direct oxidation of hydrogen to hydrogen peroxide.
It is yet another object of the invention to provide a novel hydrophobic multicomponent catalyst that is useful for the direct oxidation of hydrogen by oxygen even at atmospheric pressure and shows high hydrogen conversion activity and high selectivity for hydrogen peroxide formation.
These and other objects of the invention are accomplished by providing a novel hydrophobic multicomponent catalyst comprising a hydrophobic polymer membrane deposited on a highly acidic Pd containing catalyst, and a process for the preparation thereof.
SUMMARY OF THE INVENTION
Accordingly, the present invention relates to a novel hydrophobic multicomponent catalyst useful in the direct oxidation of hydrogen by oxygen to hydrogen peroxide, said catalyst being of the formula:
R(
a
)/A
x
B
y
PdO
z
(
b
)/X(
c
)/MO
n
(
d
)/N
wherein: R is a hydrophobic polymer, which forms a hydrophobic polymer membrane permeable to hydrogen, oxygen and hydrogen peroxide vapors; A is a metallic element selected from a group consisting of Ag, Au, Cu, Fe, Cd, Zn, Sn or mixtures thereof; B is a noble metal element other than palladium and selected from the group consisting of Ru, Pt, Rh, Ir, Os, or a mixture thereof; Pd is palladium element; O is oxygen element; X is a halogen element selected from the group consisting of F, Cl, Br, I or a mixture thereof; M is N an element

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