Method for the direct synthesis of hydrogen peroxide

Abstract

The present invention relates to a method for the direct synthesis of hydrogen peroxide using a catalyst comprising at least one catalytically active metal selected from elements in Groups 7 to 11, wherein the catalytically active metal is supported on a carrier comprising at least one compound selected from the group consisting of sulfates and phosphates of alkaline-earth metals, wherein said compound is precipitated on the carrier.

Claims

1. A method for the direct synthesis of hydrogen peroxide, comprising reacting hydrogen and oxygen in the presence of a catalyst comprising at least one catalytically active metal selected from elements in Groups 7 to 11, wherein the catalytically active metal is supported on a carrier comprising precipitated barium sulfate, wherein the carrier further comprises SiO.sub.2 and wherein the barium content of the catalyst, measured by ICP-OES is higher than 3% wt.

2. The method according to claim 1, wherein the catalytically active metal is selected from palladium, platinum, silver, gold, rhodium, iridium, ruthenium, osmium, and combinations thereof.

3. The method according to claim 2, wherein the catalytically active metal is palladium or the combination of palladium with another metal.

4. The method according to claim 1, wherein the catalytically active metal is present at least partly in reduced form.

5. The method according to claim 1, wherein the barium content of the catalyst, measured by ICP-OES, is higher than 5% wt.

6. The method according to claim 1, wherein the catalyst has been prepared by a method wherein in a first step, barium sulfate is precipitated on a SiO.sub.2 support material to form the carrier and in a second step, the catalytically active metal is deposited on said carrier.

7. The method according to claim 6, wherein solutions of halides of the alkaline-earth metal and of the catalytically active metal are used respectively in the first and in the second step.

8. The method according to claim 6, wherein after the metal has been deposited on the support material, the product is recovered, washed and dried and subsequently, the metal deposited on the support is at least partially reduced.

9. The method according to claim 1, wherein the synthesis is carried out in a liquid phase containing halide ions.

10. The method according to claim 9, wherein the liquid phase further comprises an acid chosen from sulfuric acid, nitric acid and orthophosphoric acid.

11. The method according to claim 10, wherein the acid comprises orthophosphoric acid.

12. The method according to claim 9, wherein the synthesis is carried out in a liquid phase containing bromide ions.

13. The method according to claim 1, wherein the catalytically active metal is palladium or the combination of palladium with another metal.

14. The method according to claim 1, wherein the carrier consists essentially of SiO.sub.2 with a precipitated layer of barium sulfate thereon.

Description

EXAMPLES

Example of Catalyst Preparation

(1) In a beaker of 11, 100 cc of demineralized water and 250 cc of sulfuric acid 1M have been introduced. 20 g of silica have been added. The mechanical stirrer has been started (250 rpm) and the suspension was heated at 80 C.

(2) An aqueous solution of 1.41 g barium chloride (BaCl2) in 10 ml of demineralized water was prepared at room temperature.

(3) With a syringe pump, the solution of BaCl2 was introduced in the solution at 80 C.

(4) The beaker was let during 24 hours at room temperature without stirring.

(5) The suspension was filtered under vacuum and the solid was washed with demineralized water.

(6) The solid was dried one night at 100 C.

(7) A solution of palladium chloride in water was prepared with the amount of Pd necessary to obtain a loading of 0.62% Wt Pd on the catalyst. The catalyst was dried at 95 C. for 24 hours. The Pd was reduced under influence of hydrogen, diluted with nitrogen, during 5 hours at 150 C.

(8) This catalyst was called catalyst A.

Example of Catalyst Preparation

(9) Same recipe as describe above has been used for another batch but with a Pd loading of 2%. This catalyst was called catalyst B.

Example of Catalyst Preparation

(10) In a flask of 250 cc, 40.44 g of silica were introduced and put on a rotating dryer. It was heated at 75 C. and the pump was started for obtaining a vacuum of 230 mbars.

(11) An aqueous solution of 2.78 g barium chloride (BaCl2) in 65 ml of demineralized water was prepared at room temperature.

(12) The solution was introduced drop by drop in the rotating dryer, under vacuum. The water was evaporated directly and the salt of barium was precipitated on the silica.

(13) 250 cc of sulfuric acid 0.12M was introduced slowly, drop by drop directly in the flask at 75 C. and 110 mbars. The water and the HCl were evaporated directly and the barium sulfate was formed on the surface.

(14) The support was dried during one night at 95 C., grinded and calcined during 5 h at 600 C.

(15) A solution of palladium chloride in water was prepared with the amount of Pd necessary to obtain a loading of 2% Wt Pd on the catalyst. The catalyst was dried at 95 C. for 24 hours. The Pd was reduced under influence of hydrogen, diluted with nitrogen, during 5 hours at 150 C.

(16) This catalyst was called catalyst C.

(17) Characterization of Catalyst A, B & C

(18) TABLE-US-00001 Catalyst A Catalyst B Catalyst C Pd content % Wt 0.62% NM 1.80% Ba content % Wt 5.0% 5.8% 3.9% BET surface m2/g NM 325 NM Granulometry m NM 100-200 NM NB: NM stands for Not Measured

Counterexamples of Catalyst Preparation

(19) A catalyst based on barium sulfate has been prepared by incipient wetness method: 1 g of a solution of palladium chloride (19.9% Wt in Pd) has been diluted in 19 g of demineralized water. The solution has been put in contact with 20 g of BaSO4. Catalyst has been dried overnight at 95 C.

(20) Palladium was reduced under influence of a mix hydrogen/nitrogen at 150 C. during 5 hours.

(21) This catalyst was called catalyst D.

(22) The Pd content of this catalyst is 1.20% Wt. The BET surface is 9.7 m2/g and the granulometry is upper than 110 m.

(23) A catalyst based on silica has been prepared by incipient wetness method: 1 g of a solution of palladium chloride (19.9% Wt in Pd) has been diluted in 19 g of demineralized water. The solution has been put in contact with 20 g of silica. Catalyst has been dried overnight at 75 C.

(24) Palladium was reduced under influence of a mix hydrogen/nitrogen at 125 C. during 8 hours.

(25) Pd content has been determined by ICP-OES and reaches 0.91% Wt.

(26) This catalyst was called catalyst E.

(27) Catalyst E has a surface area determined by BET of 316 m2/g and is amorphous (DX). The diameter of the particles determined by SEM is around 200 microns.

Examples of Catalyst Preparation

(28) Several catalysts have been prepared following the recipe described for the catalyst A. The Pd loading attended is 2% Wt in each case. They were called catalysts F, G, H and I.

(29) Characterization of Catalyst D to I

(30) TABLE-US-00002 Catalyst Catalyst Catalyst Catalyst Catalyst D F G H I Pd content % Wt 2.0% NM NM NM NM Ba content % Wt NM 2.3% 2.4% 1.9% 2.9% BET surface m2/g 9.7 NM NM NM NM Granulometry m 3.7 NM NM NM NM
Direct Synthesis of Hydrogen Peroxide

(31) In a HC276 380 cc reactor, methanol (220 g), Hydrogen bromide (58 ppm), ortho-phosphoric acid (H3PO4) and catalyst (1.80 g) were introduced. The amount of o-phosphoric acid was calculated to obtain a final concentration of 0.1M.

(32) The reactor was cooled to 5 C. and the working pressure was at 50 bars (obtained by introduction of nitrogen).

(33) The reactor was flushed all the time of the reaction with the mix of gases: Hydrogen/Oxygen/Nitrogen. The total flow was 3975 mlN/min

(34) When the gas phase out was stable (GC on line), the mechanical stirrer was started at 1200 rpm.

(35) GC on line analyzes every 10 minutes the gas phase out.

(36) Liquid samples were taken to measure hydrogen peroxide and water concentration.

(37) Hydrogen peroxide was measured by redox titration with cerium sulfate.

(38) Water was measured by Karl-Fisher titration.

(39) Attrition Test

(40) The following usual laboratory equipment was used:

(41) Sieve shaking machine, for instance: Rotap-International Combustion Ltd, Derby, UK.

(42) Test sieves: 200 mm diameter, aperture sizes 106 m and 63 m, complying with ISO 565.

(43) Balance capable to weigh to 0.1 g.

(44) Attrition apparatus: a glass tube equipped with a P4 filter at the bottom.

(45) Gas goes through the filter and fluidized the solid.

(46) 25 mm diameter glass tubing with associated gaskets and flanges

(47) Soxhlet thimbles, 25 mm diameter

(48) Orifice plate stainless steel, with a 0.4 mm hole drilled centrally (drill the plate to match the flanges)

(49) Flow meter, graduated in liters per minute.

(50) The following recipe was used:

(51) Place about 30 g of support on the 106 m sieve. Place the sieves on the shaking device and sieve for 10 minutes. Weigh 25.0 g of catalyst retained on the 106 m sieve.

(52) Transfer 25.0 g of catalyst to the attrition apparatus. Place the dust collector (Soxhlet thimble) on the top of the glass tube and set ON the timer button to allow the air to pass into the attrition tube for 30 minutes.

(53) When the apparatus was stopped, set OFF the timer button.

(54) Transfer quantitatively the contents of the attrition tube and dust collector into the nest of sieves for 10 minutes. Weigh the contents of each sieve and the base pan. Let the weight of the sample which has a size smaller than 63 m be W1. Let the total weight of all sieves be WP.

(55) Attrition, %=W1/WP100

Examples No. 1 & 2 of Hydrogen Peroxide Direct Synthesis

High Amount of H3PO4

(56) TABLE-US-00003 Catalyst A Catalyst B Methanol g 220.26 220.01 HBr ppm 57.7 57.7 H.sub.3PO.sub.4 M 1.6 1.6 Catalyst g 1.7843 1.8012 Temperature C. 5 5 Pressure bar 50 50 Hydrogen % Mol 3.3 3.3 Oxygen % Mol 68.1 68.1 Nitrogen % mol 28.5 28.5 Total flow mlN/min 3155 3155 Speed rpm 1200 1200 Contact time Min 240 300 Hydrogen peroxide fin % Wt 4.06 3.26 Water fin % Wt 4.13 0.45 Conversion fin % 35.7 18.1 Selectivity fin % 69.0 79.0 Productivity fin mol H.sub.2O.sub.2/(kg of Pd*h) 5999 1179

(57) These results show that a better selectivity but a lower productivity is obtained when switching from 0.62 to 2% wt Pd loading.

Examples No. 3 & 4 of Hydrogen Peroxide Direct Synthesis

Lower Amount of H3PO4 and Influence of the H2/O2 Ratio

(58) Catalyst B was used in both examples, with a different H2/O2 ratio

(59) TABLE-US-00004 Catalyst B Catalyst B Methanol g 220.35 221.10 HBr ppm 57.7 57.7 H.sub.3PO.sub.4 M 0.1 0.1 Catalyst g 1.8003 1.8010 Temperature C. 5 5 Pressure bar 50 50 Hydrogen % Mol 3.3 3.6 Oxygen % Mol 68.1 55.0 Nitrogen % mol 28.5 41.4 Total flow mlN/min 3155 3975 Speed rpm 1200 1200 Contact time Min 240 240 Hydrogen peroxide fin % Wt 6.33 8.56 Water fin % Wt 3.40 4.75 Conversion fin % 57.5 36.9 Selectivity fin % 52 51 Productivity fin mol H.sub.2O.sub.2/(kg of Pd*h) 2873 3895

Example 5 and Counterexamples No. 1 & 2

Comparison with a Catalyst Based on Silica or Barium Sulfate

(60) TABLE-US-00005 Catalyst B, Catalyst D & Catalyst E Catalyst Catalyst Catalyst B D E Methanol g 221.10 220.11 150.49 HBr ppm 57.7 57.8 51 H.sub.3PO.sub.4 M 0.1 1.6 0 Catalyst g 1.8010 0.9186 2.6675 Temperature C. 5 25 5 Pressure bar 50 50 50 Hydrogen % Mol 3.6 3.3 3.51 Oxygen % Mol 55.0 68.1 35.06 Nitrogen % mol 41.4 28.5 61.43 Total flow mlN/min 3975 3155 2567 Speed rpm 1200 1200 1500 Contact time Min 240 240 225 Hydrogen peroxide fin % Wt 8.56 5.06 2.48 Water fin % Wt 4.75 4.11 5.31 Conversion fin % 36.9 47.1 46.0 Selectivity fin % 51 74 19.9 Productivity fin mol H.sub.2O.sub.2/ 3895 7350 1207 (kg of Pd*h)

(61) As can be see, Catalyst D gives the better results in terms of selectivity and productivity but it requires a high H3PO4 content (1.6M) with the associated corrosion problems; and it gives bad results in attrition (see below).

Counterexample 3

Catalyst D Based on BaSO4 Alone and Used with 0.1 M H3PO4

(62) TABLE-US-00006 Catalyst D Methanol g 219.99 HBr ppm 35 H.sub.3PO.sub.4 M 0.1 Catalyst g 0.8181 Temperature C. 25 Pressure bar 50 Hydrogen % Mol 3.6 Oxygen % Mol 55 Nitrogen % mol 41.4 Total flow mlN/min 3975 Speed rpm 1200 Contact time Min 180 Hydrogen peroxide fin % Wt 0.64 Water fin % Wt 2.19 Conversion fin % 11.2 Selectivity fin % 15 Productivity fin mol H.sub.2O.sub.2/(kg of Pd*h) 1247

(63) This counterexample shows indeed the bad results obtained when lowering the H3PO4 content with Catalyst D.

Examples No. 6 to 9

Comparison with Different Ba Loading

Catalysts F to I

(64) TABLE-US-00007 Catalyst Catalyst Catalyst Catalyst F G H I Methanol g 220.39 221.34 220.41 223.42 HBr ppm 57.7 57.7 57.7 57.7 H.sub.3PO.sub.4 M 0.1 0.1 0.1 0.1 Catalyst g 1.8000 1.8016 1.8008 1.8006 Temperature C. 5 5 5 5 Pressure bar 50 50 50 50 Hydrogen % Mol 3.6 3.6 3.6 3.6 Oxygen % Mol 55.0 55.0 55.0 55.0 Nitrogen % mol 41.4 41.4 41.4 41.4 Total flow mlN/min 3975 3975 3975 3975 Speed rpm 1200 1200 1200 1200 Contact time Min 240 240 240 240 Hydrogen % Wt 3.58 3.34 3.81 4.50 peroxide fin Water fin % Wt 2.76 2.19 2.73 2.21 Conversion % 19.0 6.2 20.1 21.3 fin Selectivity % 43 46 43 53 fin Productivity mol H.sub.2O.sub.2/ 1627 1519 1727 2068 fin (kg of Pd*h)

(65) SEM analysis of catalyst H shows a better barium repartition on the SiO2 particles.

(66) In fact, Ba loadings below 3% wt give a rather high experimental error: see FIG. 1 attached, which represents graphically for examples 3 and 6 to 9, the evolution of the final H2O2 concentration in function of the Ba loading.

(67) This is why in a preferred embodiment of the invention, the barium content of the catalyst, measured by ICP-OES, is higher than 3% wt, more preferably higher than 5% wt.

Example of Attrition

(68) TABLE-US-00008 Attrition, % Wt Catalyst C 3.2% Catalyst E 3.1% Catalyst D .sup.6%

(69) The value of the attrition given for catalyst D is an approximation because the product was sticky and difficult to handle.

(70) Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.