CA2128430C

CA2128430C - Production of hydrogen peroxide

Info

Publication number: CA2128430C
Application number: CA002128430A
Authority: CA
Inventors: Karl T. Chuang; Bing Zhou
Original assignee: Eka Nobel AB
Current assignee: Nouryon Pulp and Performance Chemicals AB
Priority date: 1992-01-21
Filing date: 1993-01-21
Publication date: 1998-10-27
Anticipated expiration: 2013-01-21
Also published as: EP0623095A1; BR9305762A; HUT69291A; WO1993014025A1; SK88294A3; FI943377A; FI943377A0; NO942714L; HU9402151D0; NZ246548A; US5925588A; KR940703780A; AU670058B2; SK281953B6; FI111708B; JPH07503447A; US5846898A; US5338531A; NO313091B1; JP3375628B2

Abstract

The invention a relates to hydrogen peroxide manufacture, and catalyst therefor, by direct oxidation of hydrogen with oxygen in an acidic aqueous medium. The catalyst includes a Group VIII metal on a partially hydrophobic, partially hydrophilic support, such as Pd on fluorinated carbon. Improvements in H2O2 selectivity and catalyst stability are achieved by adding a source of sodium and chloride ions to the reaction medium and, in the case of a fluorinated carbon support, adding a source of fluoride ions.

Description

WO93/14025 PCT/CA93/0~27 X12~3430 1 D~SCRIPTION

4 This invention relates to a process for the production of hydrogen peroxide by direct catalytic 6 oxidation of hydrogen with oxygen. The invention also 7 relates to a catalyst for such process and a me.hod for 8 producing the catalyst.
9 BACRGROUND OF ~HE INVENTION
Hydrogen peroxide is commercially produced using 11 a process known as the Riedl-Pfleiderer process. In 12 accordance with this two step process, anthraquinone in 13 a carrier solvent, termed "working solution", is cycled 14 between an oxidation reactor and a hydrogenation reactor to convert hydrogen plus oxygen to hydrogen peroxide.
16 Variations to the process have co~centrated on the form 17 of anthraquinone, the composition of the working 18 solution and the type of catalyst used. A typical 19 catalyst is palladium, raney nickel, or nickel boride on an inert support. The catalyst may be in the form of a 21 slurry or a fixed bed. Hydrogen is needed at high 22 partial pressures in this reaction posing the risk of 23 explosion. The process is characterized as belng 24 complex and capital intensive.
Processes for the direct oxidation of hydrogen 26 and oxygen to hydrogen peroxide offer the opportunity to 27 develop a simpler, less costly process. Processes of 28 this nature have been proposed, but to the inventors' 29 knowledge have not been commercialized to date. The difficulties with the heretofore proposed processes 31 include:
32 - low concentrations of product 33 - low selectivity (thus high hydrogen 34 consumption) - low reaction rates 5 PCT/CA93/~27 1 - hazardous operating conditions (particularly 2 hydrogen partial pressure requirements in the explosive 3 range) and 4 - high acid content.
Exemplary of such processes are the following 6 patents, all of which include catalytic conversion of 7 hydrogen with oxygen in an acidic aqueous medium:

8 US 4,009,252 issued to Izumi et al. reports good 9 product concentrations (9 - 12% H2O2 by wt.) by operating at high acid concentrations (1 gpl HCl plus 49 gpl H2SO4) 11 using Pd deposited on silicic acid, and oxygen to 12 hydrogen molar ratios of 1.5 to 20, well into the 13 explosive range for hydrogen. Selectivities for 14 hydrogen to hydrogen peroxide were good with many examples in the range of from 80 - 89%. Reaction rates 16 were generally low, ranging from less than 1 to just 17 over 6 g of hydrogen peroxide per litre-hour.
18 US 4,661,337 issued to Brill reports high 19 concentrations of hydrogen peroxide and high reaction rates using Pd deposited on carbon in an aqueous 21 solution containing 35 gpl HCl, by operating a stirred 22 reactor in such a manner to keep the thickness of the 23 aqueous slurry to 2 mm or less. For example, 24 concentrations of 19.5% hydrogen peroxide were achieved at a rate of 48 g of hydrogen peroxide per litre-hour 26 using hydrogen at 250 psi partial pressure and oxygen at 27 750 psi total pressure. However, much of the benefit of 28 the higher reaction rates was lost since most of the 29 reaction vessel was empty. Also, the reaction conditions were in the explosive range for hydrogen.
31 US 4,772,458 issued to Gosser et al. (see also US
32 4,681,751 and EPA 0132294 to Gosser et al.) achieved 33 high concentrations and reaction rates with moderate 34 selectivity at low acid levels (less than 2.5 gpl H2SO4) using Group VIII metals on a variety of carriers, but at 36 hydrogen concentrations of 17% or higher, making the 37 process hazardous. Selectivities tended to be low, W O 93/14025 PC~r/CA93/00027 21;~8~30 ~ ~ P ~

1 ranging from 30% to 70%, provided bromide ions were 2 present in the reaction medium. If chloride ions were 3 used, very low selectivities of about 6~ were achieved.
4 The best results appear to have been achieved using a 51:10 ratio of Pt to Pd on an alumina carrier (1.10%
6 total metal) with a hydrogen concentration of 17.8%.
7 Hydrogen peroxide concentrations were 16.4% at 70%
8 selectivity and the reaction rate was 52 g hydrogen 9 peroxide per litre-hour.
10There is a need for a direct oxidative process 11 for the production of hydrogen peroxide which will 12 produce hydrogen peroxide in good concentrations and at 13 high selectivities and reaction rates, while allowing 14 the process to be conducted at low acid levels and below the explosive range of hydrogen.

17The present invention is based on a number of 18 surprising discoveries made in investigating the direct 19 catalytic oxidation of hydrogen with oxygen in an acidic aqueous medium using a catalyst comprising a Group VIII
21 metal on a support. Firstly, the inventors discovered 22 that the nature of the catalytic support used was 23 important. Typically supports used in prior art 24 processes were either strongly hydrophobic or strongly hydrophilic. The inventors discovered that a 26 hydrophilic/hydrophobic balance in the catalyst support 27 (and thus the resulting catalyst) was desirable. The 28 catalyst (and catalyst support) must be partially 29 hydrophobic so as to allow the gaseous reactants (hydrogen and oxygen) to contact the catalyst surface.
31 However, the catalyst (and catalyst support) must also 32 be partially hydrophillic, or partially wettable, so as 33 to allow the hydrogen peroxide formed at the catalyst 34 surface to be diffused into the liquid phase. If the hydrogen peroxide remains associated with the catalyst 36 surface for a period of time water is formed.

21 ~430 The inventors have found that this hydro-phobic/hydrophilic balance is preferably achieved using a fluorinated carbon support or a partially wettable Vulcan (Trade Mark for carbon black) carbon support. The level of fluorination is preferably in the range of 10-65% F, more preferably 20-50% F.
A second surprising discovery was that the selectivity of the reaction for hydrogen peroxide could be increased with the addition of a source of sodium and chloride ion. This can be achieved in the catalyst preparation stage, as will be described hereinafter, or by adding a source of these ions to the acidic aqueous reaction medium. In fact since these soluble ions are constantly removed with the aqueous reaction medium during the process, a supply of these ions to the aqueous medium is preferable throughout the process or at least once a decline in catalytic activity is noticed. The most economical source of these ions is in the form of NaCl. Amounts in the range of 3 to 30 wt % based on catalyst are desired.

21 ~8430 4a The inventors noticed that the catalytic activity of their preferred catalyst (Pd on a fluorinated carbon support) declined with use. Having discovered the level of fluorination to be important to the catalyst, the inventors tried adding a source of fluoride ions to the aqueous medium. This led to an important third discovery, that a source of fluoride ions in the aqueous medium stabilized the catalyst against decline in catalytic activity. A convenient source of fluoride ions is NaF, which can be included in amounts of 2 to 10 wt %
based on catalyst.
In producing a supported catalyst, the inventors made a fourth important discovery. The inventors found that it was preferable to slurry together the Group VIII metal (preferably Pd) with sodium citrate in a solution such as water. It is believed that this forms a Pd-sodium citrate complex or colloid with two important WO93/1~25 PCT/CA93/0~27 2128~30~ ~

1 consequences. When the catalyst support is impregnated 2 with the Pd-sodium citrate complex, the metal is 3 strongly held to the support and well distributed on the 4 support surface. In the preferred embodiment of the invention, this method of catalyst preparation also 6 provides the desired sodium and chloride ions in the 7 catalyst, the sodium being supplied from the sodium 8 citrate and the chloride from the chloride salt of the 9 Group VIII metal (for example PdCl2) which is initially slurried with the sodium citrate.
11 The combination of the above-described 12 discoveries have resulted in a process for the 13 production of hydrogen peroxide which can be conducted 14 with good concentrations of H2O2 (5-6%), at high selectivities (up to 100%) and good reaction rate (5 -16 11 gpl-hr H2O2), while allowing one to operate at 17 hydrogen pressures below the explosive limit and 18 moderate acidities (for example 6 gpl H2SO4).
19 Broadly stated, the invention provides a process for producing hydrogen peroxide by direct oxidation of 21 hydrogen with oxygen in an acidic aqueous medium, 22 comprising:
23 (a) contacting the hydrogen and oxygen containing 24 acidic aqueous medium with a catalyst consisting of at least one Group VIII metal on a partially hydrophobic, 26 partially hydrophilic support in a pressure vessel;
27 (b) providing a source of sodium and chloride 28 ions to the acidic aqueous medium either at the outset 29 of the reaction or once there is a decline in catalytic activity;
31 (c) maintaining the pressure in the vessel in the 32 range of 3.5 MPa - 20 MPa, with a hydrogen partial 33 pressure below the explosive limit; and 34 (d) maintaining the temperature in the range of the freezing point of the aqueous medium to about 60~C.

WO93/14025 PCT/CA93/0~27 z~za43~ -~

1 In another aspect, the invention broadly provides 2 a catalyst for use in the production of hydrogen 3 peroxide, comprising:
4 (a) a partially hydrophobic, partially hydrophilic support, preferably Vulcan carbon or 6 fluorinated carbon with a 10-65% F content;
7 (b) a Group VIII metal; and 8 (c) a source of sodium and chloride ions.
9 In yet another broad aspect of the invention, there is provided a method of produclng a catalyst for 11 the production of hydrogen peroxide, comprising:
12 (a) providing sodium citrate and a Group VIII
13 metal salt in an aqueous solution;
14 (b) heating the solution to form a Group VIII -sodium citrate colloid;
16 (c) adding a catalyst support to the colloid 17 containing solution;
18 (d) evaporating the solution from the solid; and 19 (e) reducing the resulting solid in a hydrogen atmosphere.

22 A Group VIII metal is used in a catalytically 23 effective amount in the catalyst of this invention.
24 While such metals as Pt, Ru, Rh, Ir are catalytically active for the production of hydrogen peroxide, Pd is 26 the preferred metal. Mixtures of Group VIII metals may 27 also be used. The metal is generally provided in the 28 form of salt, preferably a chloride salt such as PdCl2.
29 The Group VIII metal is employed in the form of a supported catalyst, the catalyst support being 31 partially hydrophobic and partially hydrophillic, as 32 described hereinafter.
33 The support should have a surface area in the 34 range of 50 m2/g to 1500 m2/g. A surface area of about 130 m2/g has been found to be suitable. Preferably, the 36 support is used as discrete particles or granules ;~28~30 q ~ i 1 (partlcle size less than 1 micrometer being suitable), 2 but it may also be deposited on other support material 3 such as ceramic beads or rings, as is known ln the art.
4 As previously set forth, the catalyst support (and the resulting catalyst) should have a hydrophobic/
6 hydrophilic balance which allows the gaseous reactants 7 (H2 + ~2) to reach the catalyst surface (in aqueous 8 medium) while allowing the formed H202 to be released 9 into the aqueous medium. Strongly hydrophobic catalyst supports as are known in the art, are not suitable.
11 Hydrophobicity is often defined by the "contact angle"
12 according to Young's Theory. A catalyst support having 13 a contact angle of 90~ is typically accepted as being a 14 hydrophobic catalyst support. Catalyst supports in accordance with the present inventions will have a 16 contact angle less than 90~.
17 Two preferred catalyst supports in accordance 18 with this invention are partially wettable 19 prefluorinated carbon and Vulcan carbon. In respect of the former material, the level of fluorination affects 21 the hydrophobic/hydrophilic nature of the catalysts. A
22 level of fluorination of 10 - 65 % F is preferred. A
23 level of fluorination of 20 - 50 % F is more preferred 24 with 28% F being found to be sufficient. Partially wettable Vulcan carbon is a specially treated activated 26 carbon available from Cabot, U.S.A.
27 The catalyst is preferably made by first 28 preparin~ a complex or colloid of the Group VIII metal 29 with sodium citrate. This provides a stronger attachment of the metal to the catalyst support and 31 better disperses the metal on the catalyst surface. To 32 that end, sodium citrate and the Group VIII metal are 33 slurried in a solution such as water and heated to form 34 the colloid. Heating should be at the boiling point for at least 6 hours and preferably 10 hours. The amount of 36 GrGup VIII metal used should be sufficient to provide 37 about 0.1 - 10 % wt in the final catalyst. In respect 2~,z843~

1 of Pd, an amount of 0.7% wt in the catalyst is 2 sufficient.
3 The catalyst support is impregnated with the 4 metal-colloid solution. Preferably a rea~ent is added to the catalyst support metal-colloid slurry to lower 6 the density of the slurry and decrease the tendency of 7 the catalyst support to float at the surface. Methanol 8 is suitable for this purpose. After slurrying, the 9 solution is evaporated and the catalyst is reduced in a hydrogen atmosphere (preferably 14 hours at 300~C).
11 In accordance with the preferred embodiment 12 described above, the catalyst inherently contains the 13 desired sodium chloride ions found to improve subsequent 14 H2O2 production. The sodium is provided by the sodium citrate while the chloride is provided from the PdCl2 16 salt. When prepared in this manner, the catalyst can 17 initially be used without adding NaCl to the reaction 18 medium.

19 Production of Hydrogen Peroxide The process for producing hydrogen peroxide is 21 preferably performed in a stirred, pressure reactor such 22 as a flow slurry autoclave, at temperatures between the 23 freezing point of the liquid medium and about 60~C, 24 preferably 0 - 25~C. As the reaction is highly exothermic, cooling to these temperature is generally 26 needed.
27 The reactor is preferably charged with the 28 catalyst and the additives (NaCl and NaF, if desirable) 29 prior to adding the acidic aqueous solution. As previously indicated, these additives may be added later 31 during the reaction, once the catalyst activity begins 32 to decline, The additive NaCl is preferably added in 33 an amount of 3 - 30 wt % (based on catalyst) and the NaF
34 additive is preferably added in an amount of 2 - 5 wt %
(based on catalyst).

W O 93/14025 PC~r/CA93/00027 Z1~8~3~

1 The acidic solution is preferably a mild acidic 2 solution. An H2SO4 solution is economical. An acid 3 strength of 0.5 - 1.0 % w/w H2SO4 is suitable. Higher 4 acid strengths have not been found to improve the process.
6 ~xygen and hydrogen gas are then charged to the 7 reactor. A major advantage of the process of thls 8 invention is that it can be carried out at a hydrogen 9 partial pressure below the explosive limit. This limit is understood to be the highest percent hydrogen in the 11 reaction atmosphere which will indicate an explosive 12 range as measured by a standard MSA explosimeter.
13 Typically a H2 partial pressure below about 4 volume 14 percent is used. The total pressure in the reactor will be in the range of 500 psig (3.5 MPa) to 3000 psig (20 16 MPa), the preferred range being 1000 psig (6.7 MPa) to 17 1500 psig (10 MPa). Oxygen may be supplied in a pure 18 form or, more preferably, in combination with nitrogen.
19 Oxygen contents as low as air may be used. A preferred gas feed to the reactor consists of 3.2% H2, 10% N2 and 21 86.8% ~2-22 The reaction may be performed on a continuous or 23 batch basis. Since the NaCl and NaF additives are water 24 soluble, these additives should be added on a continuous basis as they are washed out of the system.
26 This invention is further illustrated in the 27 following examples:

28 Preparation of Catalyst 29 Example 1 Sodium citrate (8.07g) was dissolved in 807 ml of 31 water, to which was added 56 ml of 6.7 x 10-3M PdCl2.
32 This mixture was further diluted with 403 ml of water.
33 The mixture was heated to boiling for 10 hours to form 34 a Pd-sodium citrate colloid solution. To this was added 2 g fluorinated carbon (fluorine content 28%, median 36 particle size less than one micrometer, surface area 130 m2/g) together with 100 ml methanol. The solution was evaporated and the solid was reduced in hydrogen for 14 hours at 300~C. The resultant catalyst contained approximately 0.7% Pd. The catalyst was a partially wettable, black, slightly sticky powder.

Example Z
Further catalysts were prepared in accordance with the procedure set out in Example 1, with fluorinated carbon supports similar in all other respects, but having 10% to 65% F content respectively.

ExamPle 3 A further catalyst was prepared in accordance with the procedure set out in Example 1, but using a partially wettable Vulcan Carbon support available from Cabot, U.S.A. (Vulcan 9 A43 CS-329).

lOa Production of Hydroqen Peroxide Example 4 A stirred, 450 ml flow slurry autoclave was charged as follows:
- 0.3 g catalyst (Example 1) - 0.03 g NaCl - 50 ml 0.6% w/w H2SO4 The autoclave was put in a cold bath maintained at 0~C. The hydrogen and oxygen gas were introduced into the autoclave and the pressure was increased to 1000 psig with a total gas flow rate of 300 ml/min (3.2 % vol H2, 10% N2 and 86.8% ~2)~ with vigorous mixing. Product conversion and selectivity after 1, 3, 6 and 10 hours were analyzed. The gas phase was analyzed by on-line gas chromatography with a thermal conductivity detector.
Argon was used as a carrier gas for analysis. The H2, N2 and ~2 in the gas feed were separated by a 10' x 1/8"
diameter stainless steel column packed with 80-100 mesh Porapak QS (Trade Mark).

1 The llquid product was titrated by potasslum 2 permanganate to quantitatively determine the H2O2 formed.
3 The equation for the titration is:
4 5H2O2 + 2KMnO4 + 3H2SO~ 2MnSO4 + K~SO4 + 8H2O + 5~2 The H2O2 concentration was measured directly by titration 6 and confirmed by U.V. spectroscopy. The H2 convers~on 7 was calculated as a ratlo of 8 H2 content initial - H2 content measured 9 H2 content initial The H2O2 selectivity was calculated on the basis that, if 11 all the H2 reacted was converted to H202, the selectivity 12 would be 100%, thus 13 H202 measured 14 H2O2 selectivity = X 100, H202 calculated 16 where;
17 3. 2% X FX t X H2 conv % 100 18 H2O2 calculated = X 34 X
19 22.4 5 where F = flow of the gas 21 t = reaction time 22 The results are summarized in Table 1 23 TART,~ 1 24 Reaction H2O2 conc, H2 conv, % H2O2 Time % w/w Selectivity %

27 1 hr 1.1 70 84 28 3 hr 2.3 61 73 29 6 hr 3.8 58 63 10 hr 5.4 52 59 31 Example 5 32 This example is included to show the results of 33 H2O2 production without the NaCl additive. The catalyst 34 obtained after several runs in accordance with Example 4 was thoroughly washed and filtered to remove NaCl.
36 When the washed catalyst was thereafter used in H2O2 37 production (same conditions as Example 4, no added NaCl) 2~28430 the results after 10 hours were 1.32 % w/w H20~, H2 2 conversion 25.5%, H202 selectivity 30 %.

3 Example 6 4 The stabilizing effect of NaF is illustrated in this example. The procedure for producing H2O2 as set 6 forth in Example 4 was repeated. Without the addltion 7 of NaF, after 8 days reaction, the H2 conversion had 8 dropped to 33%. When NaF was added to the aqueous 9 medium in an amount of 0.01 g. the H2 conversion after 8 days was 44%.

11 Example 7 12 The importance of the hydrophobic/hydrophillic 13 balance in the catalyst support is illustrated in this 14 example. The catalysts of Example 2 (10% and 65% F
content) were subjected to reaction conditions similar 16 to Example 4 with the following results after 10 hours.

17 TABT,~ 2 18 % F H2O2 conv, H2 conv, % H202 19 % w/w Selectivity %

21 10% F 2.1 25 66 22 65% F 2.2 31 38 23 Example 8 24 This example illustrates the effect of varying the amount of NaCl added to the reaction medium. The 26 catalyst of Example 1 (0.7% w/w Pd on fluorinated carbon 27 support) was reacted under conditions similar to Example 28 4 (0.3g catalyst, 50 ml 1% w/w H2S04, varying amounts of 29 NaCl, 3.2% H2, 10.0% N2 balanced by ~2l 0~C, 1000 psig, 300 ml/min gas, 10 h reaction time). The results are 31 summarized in Table 3.

WO93/l4025 PCT/CA93/00027 1 TABT,~ 3 2 NaCl(g) H2O2 conc, H2 conv, % H202 3 % w/w Selectivity, 4 %

6 0.0117 5.83 61 53 7 0.0306 5.83 53 60 8 0.0500 5.86 53 61 9 0.1008 5.79 48 69 Example 9 11 This example lllustrates the effect of varying 12 the amount of NaF added to the reaction medium. The 13 procedure of Example 4 was repeated, but with 0.0261 g 14 NaCl and 0.0054 g NaF. After 6 hours , 4.0% w/w H2O2 was obtained, H2 conversion was 61% and H202 selectivity was 16 63%. This procedure was repeated with 0.0328 g NaCl and 17 0.0078 g NaF. After 6 hours, 3.32% w/w H2~2 was 18 obtained, H2 conversion was 58% and H202 selectivity was 19 60%. This procedure was repeated with 0.03g NaCl and 0.0290 g NaF. After 10 hours, the H2O2 concentration was 21 2.16% w/w, H2 conversion was 52% and H202 selectivity was 22 23.6%.

23 Example 10 24 This example demonstrates that NaBr and KBr do not provide similar benefits to the NaCl or NaF
26 additives of this invention. The procedure of Example 27 4 was repeated using 0.0361 g KBr in place of NaCl (acid 28 solution was 1% w/w H2SO4). After 10 hours, 1.1% w/w H202 29 was obtained, H2 conversion was about 4% and H2O2 selectivity was estimated at 100%. This procedure was 31 repeated with 0.0308g NaBr in place of NaCl. After 10 32 hours reaction, 1.1% w/w H2~2 was obtained, H2 conversion 33 was about 3% (below the detection limit of GC) and H2O2 34 selectivity was estimated at about 100%.

2~2~3~) 1 Example 11 2 The example illustrates H~O~ production with an 3 alternate catalyst support, partially wettable Vulcan 4 carbon. The catalyst of Example 3 was reacted under the conditions of Example 4 with the results of Table 4.

TABT,~ 4 7 Reaction H2Oz conc, H2 conv, % H2o~
8 Time % w/w Selectivity, 9 %

11 1 hr 1.6 91 99 12 3 hr 4.3 61 100 13 6 hr 5.8 55 95 14 10 hr 6.5 55 64

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for producing hydrogen peroxide by direct oxidation of hydrogen with oxygen in an acidic aqueous medium, comprising:
(a) contacting said hydrogen and oxygen containing acidic aqueous medium with a catalyst consisting of at least one Group VIII metal on a partially hydrophobic, partially hydrophilic support in a pressure vessel, said catalyst support being a partially wettable Vulcan (Trade Mark) carbon or a fluorinated carbon having a level of fluorination in a range of about 10 to 65% F;
(b) providing a source of sodium and chloride ions to the acidic aqueous medium either at the outset of the reaction or once there is a decline in catalytic activity;
(c) maintaining the pressure in the vessel in the range of 3.5 MPa - 20 MPa, with a hydrogen partial pressure below the explosive limit; and (d) maintaining the temperature in the range of the freezing point of the aqueous medium to about 60°C.

2. The process as set forth in claim 1, wherein the catalyst support is said fluorinated carbon, said level of fluorination being such that the support is partially hydrophobic to allow gaseous reactants to contact the catalyst, while being partially hydrophilic to diffuse formed hydrogen peroxide from the catalyst to the aqueous medium.

3. The process as set forth in claim 1 or 2, wherein the level of fluorination is in the range of about 20 to 50% F.

4. The process as set forth in claim 1 or 2, wherein the level of fluorination is about 28% F.

5. The process as set forth in claim 1, 2, 3 or 4, wherein the at least one Group VIII metal is Pd.

6. The process as set forth in claim 1, 2, 3, 4 or 5, wherein sodium, chloride and fluoride ions are provided to the aqueous medium in the form of NaCl and NaF.

7. The process as set forth in claim 6, wherein NaCl is provided in the range of about 3 - 30 wt %, based on catalyst and NaF is provided in the range of about 2 - 10 wt %, based on catalyst.

8. The process as set forth in claim 1, wherein the catalyst support is said partially wettable Vulcan (Trade Mark) carbon.

9. The process as set forth in claim 1, 2, 3, 4, 5, 6, 7 or 7, wherein the aqueous medium is agitated to prevent the catalyst from floating at the surface.

10. A catalyst for use in the production of hydrogen peroxide, comprising:
(a) a partially hydrophobic, partially hydrophilic support, said catalyst support being a partially wettable Vulcan (Trade Mark) carbon or a fluorinated carbon having a level of fluorination in a range of about 10 to 65% F;
(b) a catalytically effective amount of at least one Group VIII metal; and (c) a source of sodium and chloride ions, said source being in an amount effective to increase the selectivity of catalytic production of hydrogen peroxide by direct oxidation of hydrogen with oxygen in acidic medium.

11. The catalyst as set forth in claim 10, wherein the catalyst support is said fluorinated carbon.

12. The catalyst as set forth in claim 10, wherein the catalyst support is said partially wettable Vulcan (Trade Mark) carbon.

13. The catalyst as set forth in claim 10, 11 or 12, wherein the at least one Group VIII metal is Pd, provided in an amount in the range of about 0.1 - 10% wt.

14. The catalyst as set forth in claim 11, wherein the level of fluorination is about 20-50%.

15. The catalyst as set forth in claim 14, wherein the level of fluorination is about 28% F.

16. The catalyst as set forth in claim 14 or 15, wherein the at least one Group VIII metal is Pd, provided in an amount in the range of about 0.1 - 10% wt.

17. A method of producing a catalyst for the production of hydrogen peroxide, comprising:
(a) providing sodium citrate and a Group VIII metal salt in an aqueous solution;
(b) heating the solution to form a Group VIII
- sodium citrate colloid;

(c) adding a catalyst support to the colloid containing solution, said support being partially hydrophobic, partially hydrophilic, said catalyst support being a partially wettable Vulcan (Trade Mark) carbon or a fluorinated carbon having a level of fluorination in a range of about 10 to 65% F;
(d) evaporating the solution from the solid; and (e) reducing the resulting solid in a hydrogen atmosphere.

18. The method as set forth in claim 17, wherein the Group VIII metal is Pd, provided as a chloride salt in an amount sufficient to provide a level of Pd in the resulting catalyst in the amount of about 0.1 - 10 % wt.

19. The method as set forth in claim 17 or 18, wherein the catalyst support is said fluorinated carbon.

20. The method as set forth in claim 19, wherein the level of fluorination is between about 20 and 50% F.

21. The method as set forth in claim 20, wherein the level of fluorination is about 28% F.

22. The method as set forth in claim 17 or 18, wherein said catalyst support is said partially wettable Vulcan (Trade Mark) carbon.

23. The method as set forth in claim 17, 18, 19, 20, 21 or 22, wherein a reagent is added in step (c) to reduce the density of the aqueous solution such that the support does not float at the surface.

24. The method as set forth in claim 23, wherein the reagent is methanol.

25. The method as set forth in claim 17, 18, 19, 20, 21, 22, 23 or 24, wherein step (e) is conducted at an elevated temperature.

26. Use of a catalyst according to claim 10, 11, 12, 13, 14, 15 or 16, for production of hydrogen peroxide by direct oxidation of hydrogen with oxygen.