CA1312719C - Catalytic process for making hydrogen peroxide from hydrogen and oxygen employing a bromide promoter - Google Patents

Abstract

TITLE
Improved Catalytic Process for Making Hydrogen Peroxide from Hydrogen and Oxygen Employing a Bromide Promoter ABSTRACT OF THE DISCLOSURE
A process for making hydrogen peroxide from hydrogen and oxygen employing an aqueous reaction medium containing a bromide promoter is disclosed.

Description

~ITLE
Improved Catalytic Process for Making Hydrogen Peroxide from Hydrogen and Oxygen Employing a Bromide Promoter 5 Field of the Invention This invention concerns an improved catalytic proce~s for producing hydrogen peroxide from hydrogen and oxygen.

10 Background of_the Invention The following references disclose catalytic prooe~ses for producing hydrogen peroxide from hydrogen a~d oxygen. One problem associated with known direct combination processes is that product yields are too low 15 for large ~cale commercial applications. Improved processes for producing hydrogen peroxide in high concentrations are of significant interest to the chemical industry.
U.S. Patent 3,336,112 issued to Hooper, 20 discloses a process for producing hydroqen peroxide.
The process comprises contacting hydrogen and oxygen with a solid catalyst in the liquid pha~e in the presence of water ~nd a hydrogen peroxide stabilizer, for example, a sequestrative hydrogen peroxîde ~tabilizer. U.S. Patent 3,361,533 i~sued to Hooper, discloses a process for the production of hydrogen peroxide. The process comprises contacting hydrogen and oxygen with a solid catalyst in the liquid phase in the presence of water, an acid and a non-acidic 30 oxygen-containing organic compound.
U.S. Patent 3,433,582 issued to Campbell, disclo~es a process for producing hydrogen peroxide.
The process comprises contacting hydrogen and oxygen with a solid catalyst in a liquid medium containing ~3~2719 water and dissolved boric acid. The reference discloses that there may also be present a second radical, especially a halogen or pseudo-halogen.
U.S. Patent 4,007,256 issued to Kim et al., discloses a process for production hydrogen peroxide by contacting hydrogen and oxygen with ~ supported palladium catalyst in the presence of water, an organic nitrogen-containing compound and a strong acid.
Posplova et al., Russian Journal of Physical Chemistry, 35(2):143-14~ (1961) disclose palladium-catalyzed synthesis of hydrogen peroxide from hydrogen and oxygen.
Palladium black and palladium deposited on alumina gel, tungstic anhydide, ~ilica gel, and bone ~harcoal were used as the catalysts.
U.S. ~atent 4,009,252 issued to $~umi et al., discloses a process for preparing hydrogen peroxide by a catalytic reaction of hydrogen and oxygen in an aqueous medium containing a platinum-group catalyst. The process is characterized in that the partial pressure of hydrogen and the partial pressure of oxygen in the gaseous phase of the reaction ~ystem are ~aintained at at least 0.5 atmosphere and at least 1.0 atmosphere, r~spectively, The platinum group catalyst is cau~ed to be present in an~amount, calculated as ~etal, of at least a minimum e~fective catalytic amount up to 30 mg per 100 mL of the aqeous medium.
U.S. Patent 4,279,8B3, i6sued to Izumi et al., discloses a process for preparing hydrogen peroxide by reacting hydrogen with oxygen in the presence of a catalyst in an aqueous medium çontaining hydrogen peroxide, the improvement which comprises using an aqueous medium which contains dissolved hydro~en ~nd a platinum-group catalyst having adsorbed thereto hydrogen. Supported Pd catalysts with carbon, ilica, and a number of other materials are describcd as equivalents for support purposes.

~312719 U.S. Patent 4,335,092, issued to Dalton, Jr. et al., discloses a proce~s for preparing hydrogen peroxide. Hydrogen and oxyyen are contacted with a supported palladium catalyst in the presence of methanol. Preferably, the methanol contains up to 1.~%
S by weight of formaldehyde and is at least 0.001 N in hydrochloric acid.
U.S. Patent 4,336,238, issued to DaltQn, Jr. et al., discloses an improvement in a proce~s for producing hydrogen peroxide by contacting a mixture of hydrogen and ox~gen with a palladium on carbon catalyst in the presence of an acidic aqueous liquid capable ~
inhibiting decomposition of hydroqen peroxide. The improvement comprlses prolonging the useful life of the catalyst by continuous removal of palladium salts produced by 501ubilization of the catalyst from the acidic aqueous liquid. The medium employed comprises up to 95~ by volume of an organic ~olvent. Moreover, B202 concentrations are very low.
U.S. Patent 4,336,239, issued to Dalton, Jr. et al., discloses an improve~ent in hydrogen peroxide synthesi~ from hydrogen and oxygen in an acidic medium containing an oxygenated or nitrogenous or~anic compound using a supported~roup VIII noble ~etal catalyst. The improvement c~mprises using an oxygen/hydrogen ratio 2~ higher than about 3.4 and a catalyst level above 30 mg per 100 mL of medium.
U.S. Patent 4,379,778, issued to Dalton, Jr. et al., disclo~es improvements in palladium-carbon catalysts for the production of hydrogen peroxide from a 3~ mixture of hydrogen and oxygen in the presence of an aqueous liquid capable of inhibiting the decomposition or hydrogen peroxide. The improve~ent comprises pretreating the catalyst with an aldehyde or ketone, ar.d, preferably, also pretreating the catalyst with a 3c ~2~1~

dilute solution of hydrochloric acld. I~proved catalysts are obtained by reducing a soluble palladium compound deposited on a high surface area non-graphitic carbon base~ in the form of a dried powder, with hydrogen at 27-200C.
U.S. Patent 4,389,390, issued to Dalton, Jr. et al., discloses an improvement in a process for producing hydro~en peroxide by contac:ting a ~ixture of hydrogen and oxygen with a palladium on carbon ~atalyst in the presence of ~n acidic liquid capable of inhibiting decomposition of thus~produced hydrogen peroxide. The improvement comprise~ prolonging the useful life of the catalyst by continuous removal of palladium ~alts produced by solubilization of the catalyst from the acidic liq~id, preferably by employing high surface area activated carbon as the catalyst support and adsorbent for palladium salts.
The following four publications disclose the danger inherent in producing hydrogen peroxide in the presence of an organic component. Swern, Or~anic Peroxides, Wiley-Interscience, New York, page 26, (1970) discloses the preparation of peroxy compounds from aldehydes and hydrogen peroxide. The reference discloses that e~treme caution should be taken when handling and preparing ketone peroxides, ~ince some are very ~ensitive and explode with violence. Schu~b et ~1., Hydrogen Peroxide, Reinhold Publishinq Corporation, page 179 (1955) describes explosive characteristics of solutions of methyl alcohol, ethyl alcohol, or ~lycerine in concentrated hydrogen peroxide. ~allel Chemical and En~ineering News, _~27):4 ~1984) de~cribes potential hazards associated with organic peroxides. Schwoegler, Chemical and Enqineering News, 63(1):6 ~19~5) describe~
the shock sensitivity of acetone peroxides.

~3~2~

U.S. Patent 4,681,751 issued to Gosser, discloses a method for making hydrogen peroxide from hydrogen and oxygen employing a catalytically effective amount of Pd on adsorbent carbon.
s SUMMARY OF TIHE INVENTION
This invention concerns an improved catalytic process for making hydrogen peroxide from hydsogen and oxygen in a reaction medium. The improvement comprises (i) employing a catalytically effective amount of palladium, platinum, or a combination thereof, (ii) employing an aqueous reaction medium comprising an acid component and a bromide promoter, and ~iii) employing the acid component and bromide promoter in amounts to provide a molar ratio of hydrogen ion to bromide ion of at least about 2:l in the reaction medium.

DETAILED DESCRIPTION OF THE INVENTION
~ ,, The present invention provides an improved catalytic process for making hydrogen peroxide from hydrogen and oxygen. It has been found that high product yields can~be achieved by employing an aqueous reaction medium comprising an acid co~ponent and a bromide promoter in specified molar amountE ~nd a catalytically effective amount of palladium, platinum, or a combination thereof. These high product yields make the present method commercially feasible for large-scale applications.
The process of this invention employs a catalytically effective amount of palladium, platinum, or a combination thereof. The form of ~he ~pecified metals is not critical. ~he metals can be employed in the form of metal ions as a result of using palladium and/or platinum salts or in the form of bulk metal. The ~31271~

specified metals can also be employed in the form of a supported catalyst, optionally a supported cataly~t prepared from a metal colloid. Suitable ~upports include various for~s of carbon, silica, alumina, or ion exchange resins. Preferably, the ratio of palladium to 5 platinum is above about 20 weight percent, and most preferably above about 50 weight percent. In one embodiment, the specified metals are employed in the form of a metal colloid.
Regardless whethsr the catalyst i~ premade or made in situ in the aqueous reaction medium, the latter will comprise an acid component and a bromide promoter.
As used herein, the expression "bromide promotern in~ludes any ~ource capable of generating bromide ions in the reaction medium. The bromide ion source can, for example, be H~r, a soluble metal bromide or a compound hydrolyzable or reducible to afford bromide ion under reaction conditions. One improvement represented by employing a bromide promoter i~ that less halide can be employed to produce equivalen~ or superior product yields as compared to other halide promoters. Thus, hydrogen peroxide solutions can be produced that oontain relatively low concentrations of halide ion, as desired in certain hydrogen peroxide applications, ~uch a~ in electronic applications. Although halide ions can be removed from hydrogen peroxide solutions cont~minated therewith by various means, including treatment with ion exchange materials, the lower the initial halide ion concentration, the lower the cost of such treatment.
~referably, the bromide ion concentra~ion in the reaetion medium is from about 1 X 10 7 M to about 0.1 M, and most preferably, from about S x 10 5 M to about 0.01 M. The molar ratio of bromide ion to ~etal (Pd and/or Pt) is generally from about 10-4:1 to about 104:1, preferably from about 102:1 to about 10-3:1, and most preferably 10:1 to about 10 2:1.

.

Chloride and other compatlble halide ions can also be present in the reaction medium, but preferably the concentration of halide ions other than bromide ion is not greater than the concentration o the bromide ion. Preferably, the total halide ion concentration is not greater than about 10 1 M, in keeping with the desire to produce low halidle content hydrogen peroxide product.
It has been found that hydrogen peroxide concentrations are increased by employing the acid component and bromide promoter in amounts to provide a molar ratio of hydrogen ion to bromide ion o~ at least about 2:1 in the reaction medium. 8uitable acid~
include hydrochloric, phosphoric, ~ulfuric, nitric ~nd perchloric. Other protonic acids having a pK less than about 8 can be employed provided that they are compatible with other components of the reaetion ~edium.
Preferably, the hydrogen ion concentration in the reaction medium is from about 1 x 10 5 M to about 10 M, and most preferably from about I x 10 3 M to about 2 M.
2a The molar ratio of hydrogen ion to bro~ide ion in the reaction medium is preferably of ~rom about 5:1 to about 106:1, more preferably from about 10:1 to about 104:1, and most preferab~ly from about 100:1 to about 104:1.
~he concentrations of acid and bromide promoter are interrelated, ~o that best results are achieved with relatively high acid concentrations when the halide concentrations are at the low end of the recited ranges.
Typically, the process has been run at relative ambient partial pressures of 2 to H2 ~ about 2 to 1 up to 20 to 1 or higher. Ratios of 20 to l and aoove are preferred to avoid the possibility of explosion during continuous process runs. ~lthou~h ratios o les6 than 2 to l can be employed, such ratios may result in lower hydrogen peroxide concentrations.

~.3~27~

The process can be carried out at -50~C to 90C
and preferably from about 0C to 50C. Lower temperatures can be employed so long as liquid freezing is not a problem. Depending on the type and concentration of reaction ingredients, temperatures below -10~C are contemplated. Presence of ~bout 45 weight percent hydrogen peroxide in the reaction mixture will permit operation at -50C without freezing. It has ~een ~ound that higher temperature6 can be employed provided that the reaction system is ~ree of impurities that promote hydrogen peroxide decomposition.
Preferably the present process i6 conducted at a supcsat~ospheric pressure. Preferred pres6ure~ are in the range of from about 200 psig (1.48 MPa) to 4000 psig (27.7 MPa) with incr~asing hydrogen peroxide concentrations resulting from use of higher pressure~.
Most preferred pressures for hydrogen peroxide formation are about 400 psig t 2 . ~6 MPa) to 2500 psig (17.34 MPa).
In 6emibatch operation, with gases con~inuously entering and exiting the reactor, peroxide concentrations above about 30~ can be achieved at about 10 MPa and an inle~
O2/H2 ratio of about 4:1.
~ n advantage of the use o~ a substantially all-aqueous m~diu~ is that explosion hazards associated with the combination of high hydrogen peroxide conoentrations and organic cosolvent~ are absent.
Another ~dvantage is that a large organic recycle ~tream .
! is avoided. Other advantages include the lessenin~ of explosive hazards caused by buildup of organic peroxy compounds and elimination of catalyst deactivation cau~ed by decompGsition of organic materials.
In a most preferred embodiment, continuou5 operation of the process of this invention is conducted at about 1000 psi~ (7.0 MPa) total pressure~ ~ O2/H2 inlet ratio of about 3:1, about 0.025 M H2S04, and about 20C, with vigorous gas-liquid co~tact.

13~271~

The invention is further described in the following Examples wherein all parts and percentages are by weight and degrees are Celsius, unless otherwise stated. The weight percent H2O2 was obtained by titration with potassium permanganate solution. The weight gain and weight perc~ent H2O2 were used to calculate the selectivity as moles H2O2 found divided by the sum of the moles of water formed and the moles o~
R2O2 formed. This value was multiplied by 100 to give the selectivity in percent. In the Examples and Comparative Experiments mesh sizes refer to U.S.
Standard sieve l~nits.

Example 1 A reaction mixture ~as prepared from 5 mg of a 5% Pd on carbon catalyst (400-500 mesh), 18 g purified water, 1.0 g of 1. 0 N H2SO4 and 1.0 g of 0.001 N NaBr.
The mixture was placed in a 400 mL autoclave containing a glass liner. The autoclave was mounted on a shaking table in a large ~etal barricade with facilities for adding and removing gases and monitoring temperature and pressure from outside the barricade. The charged autoclave was pressure tested and evacuated. Then, 2.48 MPa of H2 were added to the autoclavs and 2 was added to bring the total pressure to 13.9 MPa. After 15 minutes, 2 was, again, added to bring the pressure up to 13.9 MPa. During the the reaction the temperature of the autoclave was between 15 and 19. The reaction resulted in a pressure drop of 1.63 MPa. After three hours of agitation, the weight gain of the reaction - 30 mixture was 3.8 g, the H2O2 content was 12.6 weight percent, and selectivity to H2O2 was 66%. These result~
are shown in Table I.

~3~271~

Compa_a_ive Experiments A and B
The procedure described in Example 1 was substantially repeated t~o times, except that a chloride promoter was employed. The apparatus used was the 400 mL autoclave described in Example 1. The reaction mixtures were prepared from 5 m~ of the ~% Pd on carbon catalyst (400-500 mesh), 18 g purified water, 1.0 g of 1.0 N H2SO4 and 1.0 g of 0.001 N NaCl solutior.. In each experiment, the charged autoclave was pressure tested ~nd evacuated. Then, 2.43 MPa o~ H2 were added to the autoclave and 2 was added to bring the total pressure to 13.9 MPa. After 15 minutes, 2 was, again, added to bring the pressure up to 13.9 MPa. During the reactions, the temperature of the autoclave was between 14 and 19. The reactions resulted in pre~sure drops ; 15 of 4.24 MPa and 2.46 MPa. After three hours of agitation, the weight gains of the reaction mixtures were 3.95 g and 4.05 g, the H2O2 conte~t~ were 1.9 and 2.3 weight percent, and selectivities to H2O2 were 6.4%
and 7.7%, respectively. These results are shown in Table I.

Table 1: Bydrogen Peroxide Yields from ~romide and Chloride Promoters Ex. Comp.Exp. Promoter(mmol) Wt% H2O2 Wt. Gaint~) 1 ~romide(0.001~ 12.6 3.8 A Chloride(0.001) 1.9 4~0 B Chloride(0.001) 2.3 4.0 ~3:L27~.9 The apparatus used was the 400 mL autoclave described in Example 1. The reaction mixture was prepared from 20 mg of a 5% Pd on silica gel ~atalyst (400 mesh), 18 9 purified water, 1.0 9 of 1.0 N H2SO4 and 1.0 g of 0.001 N Nasr solution. The charged autoclave was pressure tested and evacuated. Then, 2.48 MPa of H~ were added to the autoclave and 2 was added to bring the total pressure to 13.9 MPa. After 15 minu~es, 2 was, again, added to bring the pressure up to 13.9 MPa. During the reaction, the temperature of the autoclave was between 15 and 19. The reaction resulted in a pressure drop of 2.66 MPa. APter three hours of agitation, the weight gain of the reaction 15 ~ixture was 4.72 g, the H2O2 content 11.7 weight percent, and selectivity to H2O2 was 46%. These results are shown in Table 2.

Comparative Experiments C and D
The procedure described in Example 2 was substantially repeated two times, except that a chloride promoter was employed. The apparatus used was the 400 mL autoclave des~ribed in Example 1. The reacti~n ~ixtures were prepared from 20 mg of the 5% Pd on silica 25 gel (400 ~esh~, lB g purified water, 1.0 g of 1.0 N
H2~O4 and 1.0 9 of 0.001 N NaCl s~lution. ~n each experiment, the charged autoclave was pressure tested and evacuated. Then, 2.4B MPa of ~2 were added to the autoclave and 2 was added to bring the total pressure 30 to 13.9 MPa. After 15 minutes, 2 was, again, added to bring the pressure up to 13.9 MPa. ~uring the reaction, the te~perature of the autoclave was between 14 and 19. After three hours of agitation, the reactions resulted in pressure drops of 2.69 MPa and 2.45 MPa. The weight qains of the reaction mixtures were 3.81 9 and 3.80 g, the H2O2 contents were each 0.1 weight percent, and selectivities to H2O2 were each 0.3%. These results are shown in Table 2.

Table 2: Hydrogen Peroxide Yields from Bromide and Chloride Prom~ters Ex. Comp.Exp. Promoter(mmol) Wt~ H O Wt. Gain(g) 2 BromidelO.0~1) 11.7 4.7 C Chloride(0.001~ 0.1 3.8 D Chloride~.001) 0.1 3.8 Example 3 The apparatus used was the 400 mL autoclave described in Example 1. The reaction mixture was prepared from 50 mg of a 1~ Pd on alpha alumina catalyst (325 mesh~, 18 g purified water, 1.0 g of 1.0 N H2SO4 and 1.0 9 of 0.01 N NaBr solution. The mixture was placed in a sonic cleaner bath for a couple of minutes to disperse the catalyst. The charged autoclave was pressure tested and evacuated. Then, 2.48 MPa of H2 were added to the autoclave and 2 was added to bring the total pres ure to 13.9 MPa. After 15 ~inutes, 2 was, again, added to bring the pressure up to 13.9 MPa.
During the reaction, the temperature of the autoclave was between 17 and 20. The reaction re~ulted in pressure drop of 6.4 MPa. After three hours of agitation, the weight gain of the reaction mixture was 1.23 g, the H2O2 content was 4.7 weight percent, and selectivity to H2O2 was 65%. These rcsults are shown in 3~ T~ble 3.

:13~27~9 Comparative Examples E and F
The procedure described in Example 3 was 6ubstantially repeated two times, except that a chloride promoter was employed. The apparatus used wa~ the 400 mL autoclave described in Example 1. The reaction mixtures were prepared from 50 mg of the 1% Pd on alpha alumina catalyst ~325 mesh), 18 g purified water, 1.0 g of 1.0 N H2SO4 and 1.0 9 of 0.01 N NaCl solution. In each experiment, the charged autoclave was pressure tested and evacuated. ~hen, 2.48 MPa of ~2 were added to the autoclave and 2 was added to bring the total pressure ~o 13.9 MPa. Af~er 15 minutes, 2 was, again, added to bring the pressure up to 13.9 MPa. During the reactions, the temperature of the autoclave was between ~ 16 and 21. The reactions resulted in pressure drops of ¦ 15 2.87 MPa and 2.21 MPa. After three h~urs of agitation, the weight gains of the reaction mixtures were 3.28 g and 3.32 g, the H2O2 contents were 2.7 and 2.9 weight percent, and selectivities to H2O2 were 11% and 12%, respectively. These results are shown in Table 3.
Table 3: Hydrogen Peroxide Yields from Bromide and Chloride Promoters Ex. Comp.Exp.~ Promoter!mmol? Wt~ H2O2 Wt- Gain(~?
I 3 Bromide(0.01) 4.7 1.2 1 25 E Chloride~0.01) 2.7 3.3 ~ F Chloride(~.01) 2.9 3.3 . .
Example 4 The apparatus used was the ~00 mL autocla~e described in Example 1. The reaction mixture was prepared frnm 5 mg of a 1% Pt on carbon catalyst, 18 g purified water, 1.0 9 of 1.0 N H2SO4 and 1.0 9 of 0.1 N
NaBr solution~ The mixture was placed in a sonic ~3 2 7 :1 9 cleaner bath for a couple of minutes to disperse the catalyst. The charged autoclave was pressure tested and evacuated. Then, 2.48 MPa of H2 were added to the autoclave and 2 was added to bring the total pressure to 14.0 MPa. After 15 minutes, 2 was, again, added to bring the pressure up to 14.0 MPa. During the reaction, the temperature of the autoclave was between 16 and 21. The reaction ~esulted :in a pressure dr~p of 5.24 MPa. After three hours of agit~tion, the weight gain of the reaction mi~ture was 3.!;1 g, the H2O2 content was 9.3 weight percent, and selectivity to H2O2 was 47%.
These results are shown in 'rable 4.

Comparative Experiment G
The procedure described in Example 3 was substantially repeated, except ~hat a chloride promoter was employed. The apparatus used was the 400 mL
autoclave described in Example 1. ~he reaction mixtures were prepared from 5 mg of the 1~ Pt on carbon catalyst, 18 g purified water, 1.0 g of 1.0 N H2SO4 and 1.0 g of 0.1 N NaCl solution. The charged autoclave was pressure tested and evacuated. Then, 2.48 MPa of H2 were added to the autoclave a~d 2 was added to bring the total pressure to 13.9 MPa. After 15 minutes, 2 was, again, added to bring the pressure up to 13.9 MPa. During the reaction, the temperature of the autoclave was between 14 and 19~. The reaction resulted in a pressure drop of 3. sa MPa. After three hours of agitation~ the weight gain ~f the reaction mixtures was 3.19 g, the H2O2 content was 2.3 weight percent, and and selectivity to H2O2 was 10%. These results are shown in Table 4.

13~2719 Table 4: Hydrogen Peroxide Yields from sromide and Chloride Prom~ters Ex. Comp.Exp. Promoter(mmol) wt% H2O2 Wt. Gain(g~

4 Bromide(0.1) 9.3 3.5 SG Chloride(0.1) 2.3 3.2 Examples 5 and 6 The apparatus used was the 400 mL autoclave described in Example 1. The reaction mixture~ were ~ prepared from 20 mg of a 5~ Pt on silica catalyst, 18 g purified water, 1.0 g of 1.0 N H2SO4 and 1.0 g of 0.1 N
NaBr ~olution. The mixtures were plaeed in a ~onic cleaner bath for a couple of minutes to disperse the catalyst. In each Example, the autoclave was pressure tested and evacuated. Then, 20 4B ~Pa of H2 were added to the autoclave and 2 was added to bring the total pressure to 14.0 MPa. After 15 minutes, 2 was, again, added to bring the pressure up to 14.0 MPa. During the reaction~, the temperature of the autoclave was between lS~ and 19^. The reactions resulted in pres~ure drops of 1.85 MPa and 2.60 MPa. After three hours of ~gitation, the weight gains of the reaction mixtures were 3.42 9 and 3`67 g, the H2O2 contents were S.S and 6.9 weight percent, respectively, and ~electivities to H2O2 wer~ each 30%O The results are ~hown in Table 5.

Comparative Experiment ~
The procedure described in ~xamples 5 and 6 was fiubstantially repeated, excPpt that a chloride promoter was e~ployed. The apparatus used was the 403 mL
autoclave described in Example 1. The reaction mi~ures were prepared from 20 ~g of the 5~ Pt on ~ilica catalyst, 18 g purified water, 1.0 g of 1.0 N ~25~ and ~3~271~

l.O g of 0.1 N NaCl solution. The charged autoclave was pressure tested and evacuated. Then, 2.48 MPa of H2 were added to the autoclave and 2 was added to bring the total pressure to 13.9 MPa. After 15 minutes, 2 was, again, added to bring the pressure up to 13.9 MPa.
During the reaction, the temperature of the autoclave was between 16 and 19. The reaction resulted in a pressure drop of 3.16 MPa. After three hours of agitation, the weight gain of the reaction mixtures was 3.53 g, the H202 content was 0.1 weight percent, and the selectivity to H202 was 0.4%. The results are shown in Table 5.

Table 5: Hydrogen Peroxide Yields from Bromide and Chloride Promoters Ex. Co~p.Exp. Promoter~mol) Wt% H22 Wt. Gain(g) 5Bromide~O.l) 6.5 3.4 6~romide(O.l) 6.9 3.7 H ChloridetO.1) 0.1 3.5 Examples 7 and ~
The apparatus used was the 400 mL autoclave described in Exam~le 1. The reaction Mixtures were prepared from 5 mg of a l~ Pt on alpha alumina catalyst (325 mesh), 18 9 purified water, 1.0 9 of 1.0 N H2S04 and 1.0 ~ of 0.1 N ~aBr ~olution. The ~ixtures were placed in a sonic cleaner bath for a couple of minutes to disperse the catalyst. In each Example, the charged autoclave was pressure tested and evacuated. Then, 2.48 MPa Qf H2 were added to the au~oclave and 2 was added to bring the total pressure to 14.0 MPa. After 15 minutes, 2 was, again, added to bring the pressure up to 14.0 MPa. During the reaction, the te~perature of the autoclave was between 14 and ~B. The reactions ~312719 resulted in pressure drops of 2.14 MPa and 1.79 MPa.
After three hours of agitation, the weight gains of the reaction mixtures were 3.B6 g and 2.60 9, the H2O2 contents were ~.6 and 6.1 ~eight percent, and the selectivities to H2O2 were 38% and 37%, re~pectively.
These results are shown in Table 6.

Compa ative Experiment I
The procedure described in Examples 7 and 8 was substantially repeated, except that a ehloride promoter 10 was employed. The apparatus used was the 400 mL
autoclave described in Exarnple 1. The reaction mixture~
were prepared from 5 mg of ~he 1~ Pt on alpha alumina ; catalyst (325 mesh), 18 g purified water, l.0 g of 1.0 H2SO4 and 1.0 g of 0.1 N NaCl solution. The charged autoclave was pressure tested and evacuated. Then, 2.48 MPa of ~2 were added to the autoclave and 2 was added ~i to bring the total pressure to 13.9 MPa. After 15 minutes, 2 was, again, added to bring the pressure up to 13.9 MPa. During the reaction, the temperature of the autoclave was between 14 and 19. ~he reaction resulted in a pressure drop of 2.23 MPa. After three hour~ of aqitation, the weight gain of the reaction mixtures was 3.4~ g, the H2O2 content was 0.5 weight peroent, and the selectivity to ~22 was 1.9%. These results are shown in ~able 6.

Table 6: Hydrogen Peroxid4 Yields from Bromide and Chloride Promoters _ Ex. Comp.E~p. Promoter~mmol) Wt~ H2O2 Wt. Gain~) 7 Bromide(0.1) 6.1 3.9 8 Bromide(0.1) 8.6 3.4 I Chl~ride(0.1) 0.5 2.6 ~7 ~31271~

Exa~ple 9 and Comparative ExperimentS J and_~

Preparation of simetalllc Cataly~t A bimetallic catalyst of 0~1% Pt and 1% Pd on carbon was prepared according to the following procedure. A pla~inum-palladium bime~allic colloid was prepared according to a method similar to that described in Turkevich, et al., Proc.of YII Int. Con~r. Catal.
(Elsevier, New York, 1981~ at page 160, the disclosure of which is incorporated herein by reference. ~11 glassware was cleaned with aqua regia prior to use. The water used was purified by distillation and then filtered through a water purification system, equipped with mixed bed ion exchangers and an organic/colloid removal column. The following reagent solutions were prepared: 0.1320 9 of ~dCl~ and ~ mL of 1 N HCl wer~
diluted to lO0 mL with water; 0.2500 g of H2PtCl6 6H~O
was added to lO0 mL of water; and 1% sodium citrate solution. ~ll solutions were filtered through a 0.22 micrometer millipore filter prior to use. A two lit~r 3 necked round bottom flask was charged with 940 mL of water. The water was brought to boiling with an electric heating mantle, and 75 mL of the chloropalladic acid solution and 5 mL of the chloroplatinic acid solution were added. The resulting ~olution was bright yellow.
The solution was brought to boiling, and 120 mL
of 1% sodium citrate was added. Within fifteen minutes the solution became darker and at the end of thirty minutes was completely black. This ~olution was refluxed for four hours, whereupon it was allowed to cool ~nd then transferred to a refrigerator for storage.
Uv-vis spectroscopy and analytical electron microscopy was used to characterize the as-formed sols.
The second part of the preparation involved ~5 adsorption of this colloidal bimetzlllic onto a carbon support. A slurry was formed from two grams of wide pore carbon ~325 mesh) having a surface area of 560 m2/g and 380 mL of the above platinum-palladium colloid.
This slurry was stirred for one hour and then filtered through a 0.22 micrometer millipore filter. Uv-vis spectroscopy indicated the absence vf bimetallic colloid in the iltrate. ~he solid remaining on the filter was allowed to air dry and then loaded into a yuartz tube containing a medium-size fritted disc. This tube was put in a vertical Lindberg tube furnace, flowmeter set at 70 mL/min. The resulting sample wa6 purged with helium for twenty minutes, after which the feed gas was switched to hydrogen and allowed to flow ~or ten minutes before heating to 200C. The sample was held at 200C
for one hour in H2. It was then allowed to cool in the hydrogen at~osphere until room temperature was reached, and then flushed with helium for twenty minutes. This procedure gave a 0.1~ Pt and 1.0% Pd on carbon catalyst.

Example 9 The apparatus used was the 400 mL autoclave described in Example 1. The reaction mixture was prepared from 5 ~9 of the 0~1% Pt and 1.0% Pd on ~arbon catalyst described above, 18 ~ purified water, 1.0 g of l.0 N H2SO4 and 1.0 9 ~f 0.0001 N NaBr ~olution. The mixture was placed in a sonic cleaner bath for a coupl~
of minutes to disperse the catalyst. ~he charged autoclave was pressure tested and evacuated. Then, 2.48 MPa of H2 were added to the autoclave ~nd 2 was added to bring the total pressure to 13.9 MPa. ~fter 15 ~inute~, ~2 was, again, added to bring the pressure up to 13.9 MPa. During the reaction, the temperature of the autoclave was between 16 and 19. The reaction resulted in a pressure drop of 2.54 MPa. ~fter three 11 3~271~

hours of agitation, the weight gain of the reaction mixture was 5.40 g, the H2O2 content was 15.8 weight percent, and the selectivity to H2O2 was 61~. These results are shown in Table 7.

Comparative Experiments J and X
The procedure described in Example 9 was substantially repeated two times, except that chloride promoters were employed. The apparatus used was the 400 mL autoclave described in Example 1. The reaction mixtures were prepared from 5 mg of the 0.1% Pt and 1.0%
Pd on carbon catalyst described above, 18 g purified water, 1.0 g of 1.0 N H2SO4 and l.0 g of 0.0001 N NaCl solution. The mixtures were placed in a sonic eleaner bath for a couple of minutes to disperse the catalyst.
In each experiment, the charged autoclave was pressure tested and evacuated. Then, 2.48 MPa of H2 were added to the autoclave and 2 was added to bring the total pressure to 13.9 MPa. After 15 minutes, 2 was, again, added to bring the pressure up to 13.9 MPa.~ During the reaotion, the temperature of the autoclave was between 16 and 19. The reactions resulted in pressure drops of 2.96 MPa ~nd 2.71 MPa. After three hours of agit~tion, the weight gains~of the reaction ~ixtures were 4.48 g and 4.37 g, the H2O2 contents were 2.4 and 2.2 weight percent, and the selectivities to ~22 were 7O4% ~nd 6.9%, respectively. These results are shown in Table 7.

Table 7: Hydrogen Peroxide Yields from Bromide and Chloride Promoters Ex. Comp.Exp. Promoter(mmol? t~ H2O2 Wt. Gain(g~
9 ~romidetO.0001) 15.8 5.4 J Chloride(0.0001) 2.4 4.5 X Chloride(0.0001) 2.2 4.4 13i271~

Example 10 and Comparative Exper_ments L and M

Preparation o _ imetallic Cataly~
A 0. 05% Pt and 1~ Pd on silica catalyst was prepared according to the following procedure using metal salts as the metal source. The following reagent solutions were prepared: 0.0052 g~ of H~PtC16 6H2O was dissolved in 380 mL water, (purified as described above in Example 9) and 0.0632 g o~ PdC12 and 3 ~L in HCl were diluted to 380 mL with water. ~he 2s prepared chloropalladic acid solution and chloroplatinic acid sol~tions were combined and stirred for approximately ten minutes. To this was added 10 g of an aqueous colloidal dispersion of silica particles commercially available from ~.I. du Pont de Nemours and Company under the registered trademark Ludox-HS-40~. This mixture was stirred for approximately S minutes and then spray-dried using a Buchi*laboratory ~cale spray-dryer. The ~pray-drying conditions were as follows~ inlet temperature ~ 220C. outlet temperature - llODC. The material collected from the spray-drying was a light orange powder, The powder was subjected to ~ hydrogen procedure similar to that described in Exa~ple 9, except that 300C was used.

Example 10 Thé apparatus used wa~ the 400 mL
autoclave described in Ex~mple 1. The reaction ~ixture was prepared from 5 mg of the 9.05% Pt and 1~ Pd on silica catalyst described above, 18 g purified water, 1.0 g o~ 1.0 N H2SO4 an~ 1.0 g of 0.000~ N Na~r solution. The mixture was placed in a sonic oleaner 35 * denotes trade mark bath for a couple of minutes to disperse the catalyst.
The charged autoclave was pressure tested and evacuated.
Then, 2.48 MPa of H2 were added to the autoclave and 2 was added to bring the total pressure to 13.g MPa.
After 15 ~inutes, 2 was, again, added to bring the pressure up to 13.9 MPa. During the reaction, the temperature of the ~utoclave was between 16 and 19.
The reaction resulted in a pressure drop of 2~12 MPa.
After three hours of agitation, the weight gain of the reaction mixture was 4.79 g, the H202 content was 15.5 weight percent, and the selectivity to H202 was 68~.
These results are shown in Table B.

Comparative Experiments L and M
The procedure described in Example 10 was ~ubstantially repeated two times, except ~hat chloride promoters were e~ployed. The apparatus used was the 400 mL autoclave described in Example 1. The reaction mixtures were prepared from 5 mg of the 0.05% Pt and 1%
Pd on silica catalyst described above, 18 ~ purified water, 1.0 g of 1.0 N H2S04 and 1.0 9 of 0.001 N NaCl ~olution. The mixtures were placed in a sonic cleaner bath for a couple of minutes to disperse the catalyst.
In ea2h experime~t, the charged autoclave was pressure tested and evacuated. Then, 2.48 MPa o~ H2 were added to the sutoclave and 2 was added to bring the total pressure to 13.9 MPa. After 15 minutes, 2 was, again, ; added to bring the pressure up to 13.9 MPa. During the reaction, the temperature of the autoclave was between 16 and 19~. The reactions resulted in pressure drops of 2.16 MPa and 2.42 MPa. After three hours of agitation, the weight gains of the reaction ~ixtures were 3.75 9 and 3.81 ~, the H202 contents were 7.8 and 7.6 weight percent, and the selectiYities to H202 were 34% and 32~, respectively. The results are shown in Table 8.

~312~

Table ~: Hyd~ogPn Peroxide Yields from Bromide and Chloride Promoters ~x. Comp.ExP. Promoter(mmol) Wt% H2V2 Wt- Gain(~
Bromide(0.0001) 15.9 4.8 L Chloride~0.0001~ 7.8 3.a M Chloride~0.0001) 7.6 3.8 Example 11 and Compar~tive Experiments N and O

PrEparation of Bimetallic Catalyst A 0.1% Pt and 1% Pd on alumina catalyst was prepared ~ccording to a two step procedure similar to that described in Example 9. First, a ten liter batch of platinum-palladium bimetallic colloid was prepared using a procedure similar to that described in Example 9. Second, a 380 m~ aliquot of this blaek platinum-palladiu~ colloid was slurried with 2.0 9 of A12O~ (Sumitomo*AKP-50) having a surface area of about 12 m /g. The resulting mixture was stirred and then spray-dried using a Buchi laboratory scale spray-dryer~
~he spray-drying conditions were as follows: inlet temperature - 220.C. outlet temperature ~ 110C. The spray-dried material was a gray-brown powder. This ample was given a hydrogen treatment ~imilar to that described in Exa~ple 9 to give the 0.1% Pt and 1.0% Pd on A12O3 catalyst.

Example 11 The apparatus used was the 400 mL autoclave described in Example 1. The reaction mixture was prepared from 5 mg of the 0.1% Pt and 1.0% Pd on A12O3 catalyst described above, 18 g purified water, 1.0 g of 1.0 N H25O4 and 1.0 g of 0.0001 N Na~r solution. The * denotes trade mark ~312719 mix~ure was placed in a sonic cleaner bath for a couple of minutes to disperse the catalyst. The charged autoclave was pressure tested and evac~ated. ~hen, 2.48 MPa of H2 were added to the autoclave and 2 was added to bring the total pressure to 13.9 MPa. After 15 minutes, 2 was, again, added to bring the pressure up to 13.9 MPa. The initial temperature of the autoclave was 20. The reartion resulted in a pressure drop of 2.36 MPa. After three hours of agitation, the weight gain of the reaction mixture was 5.04 9, the H2O2 content was 16~4 weight percent, and the selectivity to H22 was 70%.
Comparative Experiments N and O
The procedure described in Example 11 was substantially repeated two times, except that chloride promoters were employed. The apparatus used was the 400 mL autoclave described in Example 1. ~he reaction mixtures were prepared from S mg of the 0.05% Pt and 1 Pd on silica catalyst described above, 18 9 purified water, 1.0 g of 1.0 N H2S04 and 1.0 g of 0.0001 N NaCl solution. ~he mix~ures were placed in a sonic cleaner bath for a couple of minutes to disperse the catalyst.
In each experiment, the charged autoclave was pressure tested and evacuated. Then, 2.48 MPa of H2 were added to the autoclave and 2 was added to bring the total pressure to 13.9 MPa. After 15 minutes, 2 was, again, added to bring the pressure up to 13.9 MPa. During the reaction, the temperature of the autoclave was between 16 and 20. The reactions resulted in pressure drops 30 of 3.30 MPa and 2.86 MPa. After three hours of agitation, the weight gains of the reaction mixtures - were 4.84 9 and 4 . 62 9, the H2O2 contents were 9.5 and 9.1 weight percent, and the selectivities to H2O2 were 32~ and 35%, respectively.

~3~2~

Example 12 and Comparative Experiments P and Q

Palladium Catalyst Preparation A 4~ Pd on a perfluorinated polymer catalyst S was prepared according to the following procedure. The acid form of a perfluorinated polymer, commercially available from E.I. du Pont de Nemours and Company under the registered trademark Nafion~ 511 (44.2 g) was ball milled for 16 h and then sieved to obtain a 230-400 mesh fraction weighing 10.5 g. The specified polymer has an equivalent weight of 1100. A 5.5 g portion of the ~230-400 mesh) fraction was slurried with Pd~WO3)2.xH2O
(x - 2, 0.72 g, 2.71 mmol) in 100 mL distilled water.
The solution was heated at 80C for 5.5 h. The resulting exchanged resin was filtered and the filtrate was evaporated to dryness. No residue remained after evaporation. This pd~2 exohanged resin was washed with 2 x 200 m~ distilled water and the washings discarded.
After drying the resulting resin in a vacuum oven under N2 for 1.5 h at 100C, it weighed 5.4 g. Palladium analysis by Galbraith Laboratories was 4.26~.

Example 12 The app~ratus used was the 400 ~L autoclave described in Example 1. The reaction mixture was prepared rom 25 ~g of the 4% Pd on perfluorinated polymer catalyst (230-400 mesh) described above, 18 g purified water, 1.0 9 of 1.0 N H2S~4 and 1.0 g o~ 0.01 N
NaBr s~lution. The mixture was placed in a sonic cleaner bath for a couple of minutes to disperse th~
catalyst. The charged autoclave was pressure tested and evacuated. Then, 2.48 MPa of ~2 weEe added, and 2 was added to bring the total pressure to 13.9 MPa. After 15 minutes, 2 was, again, added to bring the pressure up 13il 27~ ~

to 13.9 MPa. During the reaction, the temperature of the autoclave was between 16~ and 19. The reaction resulted in a pres~ure drop of 4.OB MPa. After three hours of agitation, the weight gain of the reaction ~ixture was 4.29 g, the H202 content was 9.3 weight percent, and the selectivity to H202 wa~ 37%.

Comparative Ex~periments P and Q
The procedure described in Example 11 was substantially repeated two times, except that chloride promoters were employed. The ~pparatus used was the 400 mL aut~clave described in Example 1. The reaction mixtures were prepared from 25 ~g of the 4% Pd on perfluorinated polymer catalyst described above, 18 g purified water, 1.0 g of 1.0 N H2S~ and 1.0 g of 0.01 N
NaCl solution. The mixtures were placed in a ~onic cleaner bath for a couple of minutes to disperse the catalyst. In each experiment, the charged autoclave was pressure tested and evacuated. Then, 2.4B MPa of H2 were added and 2 was added to bring the total pressure to 13.9 MPa. After 15 minutes, 2 was, again, added to bring the pressure up to 13.9 MPa. During the reactions, the temperature of the autoclave was between 13 and 18. The reactions resulted in pressure drops o~ 3.37 MPa and 3.46 MPa. After three hours of agitation, the weight gains of the reaction mixtures were 4.97 g and 4.72 q. The H202 content and the i selectivity to ~22 were 0.0 in each experiment.

Example 13 The apparatus used was the 400 mL aut~clave described in Example 1. The reaction mixture was prepared fro~ 10 mg of the 5~ Pd on carbon catalyst ~3~27~.~

described in Example 1 ~400-500 mesh), 18 g purified water, 1.0 g of 1 N H2504, and 1.0 g of a solution of sr2 in water diluted to about 0.0001 M. The mixture was placed in a sonic cleaner bath for a couple of minutes to disperse the catalyst. The charged autoclave was pressure tested and evacuated. Then, 2.~9 MPa of H2 were added and 2 was added to bring the total pressure to 13.9 MPa. After 15 minutes, 2 was, a~ain, added to bring the pressure up to 13.9 MPa. During the reaction, the temperature of the autoclave was between 10 and 13. The reaction resultecl in a pressure drop of 2.64 MPa. After three hours of agitation, the weight gain of the reaction mixture was 5.15 g, the H202 content wa~
12.9 weight percent, and the selectivity to H202 was 47%.
Example 14 The apparatus used was the 400 mL aut~clave described in Example 1. The reaction mixture was prepared from 10 mg of the 5~ Pd on carbon cataly6t ~escribed in Example 1 (400-500 mesh), 19 g purified water, 1.0 g of 1 N H2S04, and 2 mg of sodiu~ bromate.
The mixture was placed in a sonic cleaner bath for a couple of minuteS to disper~e the catalyst. The charged autoclave was pressure tested and evacuated. Then, 2.48 MPa of ~2 were added and 2 was a~ded to bring the total pressure to 13.9 ~Pa. After 15 minutes, G2 was, again, added to bring the pressure up to 13.9 MPa. During the reaction, the temperature of the autoclave was between 9 and 11. The ensuing reaction resul~ed in a pressure drop of 2.73 MPa. After three hours of agitation, the weight gain of the reaction mixture was 6.01 g, the H202 content was 18.6 weight percent, and ~he selectivi~y to H202 was 69%.

Exa~les 15 - 19 In these examples, hydrogen peroxide was produced employing phosphoric, trifluoroacetic, and trifluoromethanesulfonic acids in the reaction mixture.
The apparatus used was the 400 mL autoclave described in Example 1.
In Example 15, the reaction mixturs was prepared from 20 mg of the 5% Pd on carbon cataly~t described in Example 1 ~400 mesh), 16.5 g distilled water, 1.0 9 of 0.01 N Nasr, and 2.5 g of 0.2 M ~3PO4.
The charged autoclave was pressure tested and evacuated.
Then, 2.48 MPa o H2 were added and 2 was added to bring the total pressure to 13.9 MPa. After 15 minutes, 2 was, again, added to bring the pressure up to 13.9 MPa. During the reaction, the temperature of the autoclave was between 7 and llD. The reaction resulted in a pressure drop of 2.70 MPa. After three hours of agitation, the weight gain of the reaction mixture was 6.12 g, the H2O2 content was 17.3 weight percent, and the selectivity to H2O2 was 60%.
In Example 16, the reaetion mixture was prepared from 10 mg of the 5% Pd on carbon catalyst (400 mesh), lB.5 9 distilled water, 1.0 g of 0.01 N HBr, and 0.5 g of 0.1 M CF3COOH. The charged autoclave was pressure tested and evacuated. Then, 2.48 MPa of H2 were ~dded and 2 was added to bring the total pres~ure t~ 13.9 MPa. After 15 minutes, 2 was, again, added to bring the pressure up to 13.9 ~Pa. During the r~action, the te~perature of the autoclave was between 14 and 17. The reaction resulted in a pressure drop of 2.79 MPa. After three hours of agitation, the weight gain of the reaction mixture was 5.49 g, the H2O2 content was 14.4 weight percent, and the selectivity to B2O2 was 52%.

~ 3~

In ~xample 17, the reaction mixture was prepared from 10 ~g of the 5~ Pd on carbon catalyst (400 mesh), 18.5 9 distilled water, 1.0 9 of 0.01 N HBr, and O . 5 9 of O .1 M CF3S03H. The charq~d autcclave was pressure tested and evacuated. Then, 2.43 MPa of H2 S were added and 2 was added to bring the total pressure to 13.9 MPa. After 15 minutes, 2 was, again, added to bring the pressure up to 1 39 MPa. During the reaction, the temperature of the autoclave was between 14~ and 15C. The reaction resultecl in a pressure drop of 2.82 MPa. After three hours of agitation, the weight gain of the reaction mixture was 5"53 g, the H2O2 content was 14.2 weight percent, and the selectivity to H2O2 was 50~ .
In Example 18, the reaction mixture was prepared from 10 mg of the 5% Pd on carbon ~atalyst (400 mesh), 9.0 9 distilled water, 1.0 g of 0.01 N NaBr, and 10 g of 0.2 M H3BO3. ~he charged autoclave was pressure tested and evacuated. Then, 2.48 MPA of H2 were added and 2 was added to ~ring the total pressure to 13.9 MPa. After 15 minutes, 2 was, again, added to bring the pressure up to 13.9 ~Pa. During the reaction, the temperature of the autoclave was between 8 and 11.
The reaction resulted in a pressure drop of 2.49 MPa.
After three hours of agitation, the weight gain of the reacti~n mixture was 4.76 g, the H2O2 content was 7.9 weight percent, and the selec~ivity to H2O2 was 26~.
In Example 19~ the reaction mixture was prepared from 10 mg of the 5~ Pd on carbon ca~alyst (400 mesh), 17.0 g distilled water, 1.0 9 of 0.01 N H~r, and 2 g of 0.2 M ~NO3. The charged autoclave was pressure tested and evacuated. Then, 2.48 MPa of ~2 were added and 2 was added to bring the total pressure to 13 9 MPa. After 15 minutes, 2 was, again, added to bring the pressure up to 13.9 MPa. During the reaction, the 13~L2719 temperature of the autoclave was between 13 and 16.
The reaction resulted in a pressure drop of 2.17 MPa.
After three hours of agitation, the weight qain of the reaction mixture was 5.66 g, the H2O2 content was 16.9 weaght percent, and the selectivity to H2O~ was 63~.

Comparative Experiments P-X
In these comparative experimsnts, hydrogen peroxide was produced employing sulfate, phosphate, perchlorate, nitrite, cyanate, hexafluorosilicate, nitrate, and iodide promoters. The apparatus used was the 400 mL autoclave described in Example l.
In Comparative Experiment P, the reaction mixture was prepared from 10 mg of the 5~ Pd on carbon catalyst ~400 mesh), 9.5 g purified water, 0.5 g of 4 N
lS H25O4. The charged autoclave was pressure tested and evacuated. Then, 2.48 MPa of H2 were added and 2 was added to bring the total pressure to 13.9 MPa. ~fter 15 minutes, 2 was, again, added to bring the pressure up to 13.9 MPa. During the reaction, the temperature of the autoclave was between 10 and 11~. The reaction resulted in a pressure drop of 2.40 MPa. After three hours of agitation, the weight gain of the reaction mixture ~as ~.19 g. The H2O2 content was 0.0 weight percent and the selectivity to H2O2 was 0.0~.
In Comparative Experiment Q, the reaction mixture was prepared from 10 mg of the 5% Pd on carbon catalyst (325 mesh~, 9.5 q purified water and 0.5 g of 2 M H3PO4. The charged autoclave was pressure tested and evacuated. Then, 2.48 MPa of H2 were added and 2 was added to bring the total pressure to 13.9 MPa. ~fter lS
minutes, 2 was, again, added to bring the pressure up to 13.9 MPa. During the reaction, the temperature of the autoclave was between 13 and 15o The reaction resulted in a pressure drop of 2.67 MPa. After three 13:12719 hours of agitation, the weight gain of the reaction mixture was 4.12 g. The H202 content was 0.0 weight percent and the selectivity to H202 was 0.0%.
In Comparative Experiment R, the reaction mixture was prepared from 10 mg of the 5~ Pd on carbon catalyst (400-500 mesh), 18 g purified water, 2 g of 1 N
H2S04, and 12 mg of sodium perchlorate. ~he charged autoclave was pressure tested and evacuated. Then, 2.48 MPa of H2 were added and 2 was added to brinq the total pressure to 13.9 ~Pa. After 15 minutes, 2 was, again, added to bring the pressure up to 13.9 MPa. ~uring the reaction, the temperature of the autoclave was between 9 and 17. The reaction resulted in a pressure drop of 2.60 MPa. After three hours of agitation, the weight gain of the reaction mixture was 4.58 g, the H202 content was 0.2 weight percent, and the selectivity to H202 was 0.5%.
In Comparative Experiment S, the reaction mixture was prepared from S mg of the 5% Pd ~n carbon catalyst t400-500 mesh), 19 g purified water, 1 g of 1 N
H2S04, and ~ mg of sodium nitrite. The charged autoclave was pressure tested and evacuated. Then, 2.48 MPa of ~2 were added and 2 was added to bring the total pressure to 13.9 MPa. After lS minutes, 2 was, again, added to bring the pressure up to 13.9 MPa. During the reaction, the temperature of the autoclave was between 10 and 12. The reaction resulted in a pressure drop I of 2.42 MPa. After three hours of agitation, the weight gain of the reaction mixture was 3.03 9, the H202 content was 3.4 weight percent, and the selectivity to H202 was 16%.
In Comparative Experiment ~, the reaction mixture was prepared from 5 mg of the 5% Pd on carbon catalyst (400-500 mesh), 19 g purified water, 1 g of 1 N
H2504, and 5 mg of sodium cyanate. The charged autoclave was pressure tested and evacuated. Then, 2.48 MPa of H2 were added and O~ was added to bring the total pressure to 13.9 MPa. After 15 ~inutes, 2 was, again, added to bring the pressure up to 13.9 MPa. During the reaction, the temperature of the autoclave was between 7~ and llD. The reaction resulted in a pressure drop of 1.97 MPa. After three hours of agitation, the weiqht gain of the reaction mixture was 3.43 g, the H2O2 content was 0.4 weight percent, and the ~electivity to H2O2 was 2%.
In Comparative Experiment U, the reaction mixture was prepared from 10 mg of the 5~ ~d on carbon cataly~t (400-500 ~esh), 19 9 purified water, 1 g of 1 N
H2SO4, and 40 mg of sodium hexafluorosilicate. The charged autoclave wa~ pressure tested and evacuated.
Then, 2.48 MPa of ~2 were added and 2 was added to bring the total pressure to 13.9 MPa. After 15 minutes, 2 was, again, added to bring the pressure up to 13.9 MPa. During the reaction, the temperature of the autoclave was between 10 and 14. The reaction resulted in a pressure drop of 2.98 MPa. After three hours of agitation, the weight qain of the reaction mixture was 4.B4 9, the ~22 content was 0.0 weight percent, and the selectivity to H2O2 ~as 0Ø
In Comparative Experiment V, the reaction mixture was prepared from 5 mg of the 5% Pd on carbon catalyst ~400-500 me~h), 18 g purified water, 1 g of l N
H2SO4, and 1 g of 0.1 N nitric acid. The charged autoclave was pressure tested and evacuated. ~hen, 2.4~
MPa of ~2 were added and 2 was added to bring the total pressure to 13.9 MPa. ~fter 15 minutes, 2 was, again, added to bring the pressure up to 13.9 MPa. During the reaction, the temperature of the autoclave was between lOD and 13. The reaction resulted in a pressure drop of 2.25 MPa. After three hours of agitation, the weight gain of the reaction mixture was 3.72 g, the H2O2 content was 1.3 weight percent, and the selectivity to H2O2 was 5%.
In Comparative Experiment W, the reaction mixture was prepared from 10 mg of the 5% Pd on carbon catalyst (400-500 mesh), 19 9 purified water, 1 9 of 1 N
H2SO4, and 0.4 mg of potassium thiocyanate. The charged autoclave was pressure testled and evacuated. Then, 2.48 MPa of H2 were added and 2 was added to bring the total pressure to 13.9 MPa. After 15 minutes, 2 was, again, added to bring the pressure up to 13.9 MPa. During the reaction, the temperature of the autoclave was between g and 11. ~he reaction rlesulted in a pressure drop of 7 k~a. After three hours of agitation, the weight qain of the reaction mixture was 0.44 g, the H2O2 content was 0.6 weight percent, and the selectivity to H2O2 was 17%.
In Comparative Experiment X, the reaction mixture was prepared from 10 mg of the 5% Pd on çarbon catalyst (325 mesh), 8.5 9 purified water, O~S g of 4 N
H2SO4, and 1.0 g of 0.001 N potassium iodide. The charged autoclave was pressure tested and evacuated.
Then, 2.48 MPa of ~2 were added and 2 was added to bring the total pressure to 13.9 MPa. After 15 minutes, 2 was, again, added to bring the pressure up to 13.9 MPa. During the reaction, the temperature of the autoclave was between 10 and 11. The reaction resulted in a pressure drop of 540 kPa. After three hours of agitation, the weight gain of the reaction mixture was l.OB g, the H2O2 content was 6.0 weight percent, and the selectivity to H2O2 was 46%.
Example 20 This example illustratates the use of a bromide promoter in a continuous reactor. The apparatus was a no~inally 125 mL reactor equipped with a glass ~312719 liner, tantalum baffles and a tantalum gas dispe~sion stirrer. ~he reactor was fitted with lines to ~upply H2 and 2 and a liquid feed during the reaction period~
There was also a gas exit line and a nickel filter frit to retain the catalyst while allowing a liquid exit stream to ~low as needed to keep the reactor ~lurry volume about 45 mL. Samples of the liquid exit ~tream were titrated with potassium permanganate. The reactor was mounted in a metal barric:ade.
The reaction mixture was prepared from 1.25 g of 80~ H3P~4, 20 g of 0.1 N ~aBr and 40 g of 2.5 N H2SO4 and purified water to bring the total volume to 2 L.
The catalyst was 150 mg of a 5% Pd/C sieved to 325-400 mesh, commercially available from Alfa Products Company.
During the run the temperature was 21C~ H2 (3~ ~e~ wa~
fed at 40 mL/min and 2 at 110 mL/min ~ambient temperature & atmospheric pressure) while the reaction pressure was maintained at 7.0 MPa. The acid/bromide solution was pumped into the reactor at 0.025 mL/min.
The exit liquid contained about 25 weight percent hydrogen peroxide for about 24 hours of operation.

Example 21 The apparatus was as described in Example 20 except that a fluorocarbon polymer (Teflon~) liner was used in place of the glass one. The liquid feed solution was the same as above, but it was pumped at 0.05 mL/min. The catalyst was 450 mg of a 0.1~ Pt and 1% Pd on silica. A bimetallic colloid was prepared according to a method similar to that described in Example 9. 3800 mL of the metal colloid was mixed with 50 g of a colloidal silica commercially available from E.I. du P~nt de Nemours and Company under the registered trademark Ludox-HS40~. The resulting mixture was spray ~3~271~ .

dried using a ~iro*spray dryer with a rotacy disc atomizer at 220. The resulting solid was redu~ed in ~2 according to a method similar to that described in Example 9 to form the catalyst. The slurry volume in the reactor was about 50 mL. The total pres~ure was about 6.89 MPa. Oxygen was fed at about 141 mL/min and H2-He at about 14 mL/min (flows referenced to 1 atmosphere and room temperature). The re~ctor temperature was about 20C. The exit liquid contained about 11 weight percent hydrogen peroxi~c for ~bout 600 hours of operations.

Example 22 This example demonstrates u6e of a bromide promoter in a semibatch (semicontinuous) ~ystem. The catalyst was a 0.2% Pt and 2% Pd on ~ilica. A
bimetallic colloid prepared according to a method similar to that described in Example 9. 760 mL of the metal colloid were mixed with 5 g of a colloidal silica commercially available from E.I. du Pont de Nemours and Company under the registered trademark Ludox-HS40~. The resulting ~ixturç was ~pray dried u~ing a ~uchi Laboratory spray dryer. The resultinq ~olid was reduced in H2 according to a method similar to that de~cri~ed in ~xample 9 to form the catalyst. A glass reactor with a tantalum stirrer was charged with a mixture of 5 mg of the 0.2% Pt and 2% Pd on silica catalyst and 1 g of a solution prepared by mixing 9.0 9 purified water, 10.0 g lN H2SO4, and 1.0 9 0.01 N NaBr. The mixture was sparged with H2 for a minute. The reactor was placed on a rocker in a steel barricade and attached to gas supply and exit equipment. During the reaction period a mixture of 7~ He in H2 was fed at about 3 mL/min and 2 was fed at about 11 mL/min Ireferenced to ambient pressure and temperature). Gas was allowed to flow from * denotes trade mark 13127~9 the reactor to maintain the total pressure near 9.65 MPa. After 68 hours agitation in an about 2DC cooling bath the reaction mixture weighed 4.1 9 and contained 45.7 weiqht percent H2O~.

Example 23 This experiment was carried out according to a method similar to that described in Example 22 except that 5 mg of commercial 5% Pd/C lAlpha Products Co.) sieved to 400 to 500 mesh was used in place of the Pt, Pd bimetallic catalyst. ~he recovered reaction mixture weighed 5.3 g and contained 35.8 weight percent H2O2.

Claims (31)

1. An improved catalytic process for making hydrogen peroxide from hydrogen and oxygen in a reaction medium, wherein the improvement comprises:
(i) employing a catalytically effective amount of palladium, platinum, or a combination thereof, (ii) employing an aqueous reaction medium comprising an acid component and a bromide promoter, and (iii) employing the acid component and bromide promoter in amounts to provide a molar ratio of hydrogen ion to bromide ion of at least about 2:1 in the reaction medium.

2. A method according to Claim 1, wherein the ratio of palladium to platinum is above about 20 weight percent.

3. A method according to Claim 2, wherein the ratio of palladium to platinum is above about 50 weight percent.

4. A method according to Claim 1, wherein the palladium, platinum or combination thereof is employed in the form of metal ions as a result of using palladium and/or platinum salts.

5. A method according to Claim 1, wherein the palladium, platinum or combination thereof is employed in the form of a supported catalyst.

6. A method according to Claim 5, wherein the palladium, platinum, or combination thereof is employed in the form of a supported catalyst prepared from a metal colloid.

7. A method according to Claim 1, wherein the palladium, platinum or combination thereof is employed in the form of a colloid.

8. A method according to Claim 1, wherein the palladium, platinum or combination thereof is employed in the form of bulk metal.

9. A method according to Claim 1, wherein the bromide ion concentration in the reaction medium is from about 1 X 10-7 M to about 0.1 M.

10. A method according to Claim 9, wherein the bromide ion concentration is from about 5 X 10-5 M to about 0.01 M.

11. A method according to Claim 9, wherein the molar ratio of bromide ion to metal is from about 102:1 to about 10-3:1.

12. A method according to Claim 11, wherein the molar ratio of bromide ion to metal is from about 10:1 to about 10-2:1.

13. A method according to Claim 9, wherein the hydrogen ion concentration is from about 1 X 10-5 M to about 10 M.

14. A method according to Claim 13, wherein the hydrogen ion concentration is from about 1 X 10-3 M
to about 2 M.

15. A method according to Claim 9, wherein the molar ratio of hydrogen ion to bromide ion in the reaction medium is from about 5:1 to about 106:1.

16. A method according to Claim 15, wherein the molar ratio of hydrogen ion to bromide ion is from about 10:1 to about 104:1.

17. A method according to Claim 16, wherein the molar ratio of hydrogen ion to bromide ion is from about 100:1 to about 104:1.

18. A method according to Claim 15, wherein the method is conducted at a temperature of from about -50°C to about 90°C.

19. A method according to Claim 18, wherein the temperature is from about 0°C to about 50°C.

20. A method according to Claim 19, wherein the method is conducted at a superatmospheric pressure.

21. A method according to Claim 20, wherein the pressure is from about 1.48 MPa to about 27.7 MPa.

22. A method according to Claim 21, wherein the pressure is from about 2.86 MPa to about 17.34 MPa.

23. An improved catalytic process for making hydrogen peroxide from hydrogen and oxygen in a reaction medium, wherein the improvement comprises:
(i) employing a catalytically effective amount of palladium, platinum, or a combination thereof in the form of metal ion as a result of using palladium and/or platinum salts, (ii) employing an aqueous reaction medium comprising an acid component and a bromide promoter (iii) employing the acid component and bromide promoter in amounts to provide a molar ratio of hydrogen ion to bromide ion of at least about 2:1 in the reaction medium.

24. A method according to Claim 23, wherein the ratio of palladium to platinum is above about 20 weight percent.

25. A method according to Claim 24, wherein the ratio of palladium to platinum is above about 50 weight percent.

26. A method according to Claim 23, wherein the bromide ion concentration in the reaction medium is from about 1 X 10-7 M to about 0.1 M.

27. A method according to Claim 26, wherein the molar ratio of bromide ion to metal is from about 102:1 to about 10-3:1.

28. A method according to Claim 26, wherein the hydrogen ion concentration is from about 1 x 10-5 M
to about 10 M.

29. A method according to Claim 26, wherein the molar ratio of hydrogen ion to bromide ion in the reaction medium is from about 5:1 to about 106:1.

30. A method according to Claim 26, wherein the method is conducted at a temperature of from about -50°C to about 90°C.

31. A method according to Claim 30, wherein the method is conducted at a superatmospheric pressure.