MXPA98002676A - Composite membrane and use of it for quim synthesis - Google Patents

Abstract

This invention is a composite membrane for chemical synthesis, a chemical reactor in which the composite membrane can be incorporated, and a method for using the composite membrane. The composite membrane comprises a substrate, a first side, and a second side, wherein the substrate operatively connects the first side and the second side, the first side comprises an oxidation catalyst and the second side comprises a reduction catalyst. The reduction catalyst comprises the elemental or combination form, lanthanum, zinc, cerium, praeseodinium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, bismuth or indium. A chemical reactor that uses this composite membrane can react with hydrogen and oxygen to form hydrogen peroxide without direct mixing of the reactants.

Description

COMPOSITE MEMBRANE AND USE OF IT FOR CHEMICAL SYNTHESIS BACKGROUND AND COMPENDIUM OF THE INVENTION This invention relates to a composite membrane for chemical synthesis and to a method for its use. Said membrane compound is particularly useful in the synthesis of hydrogen peroxide from hydrogen and oxygen. The trend in today's facilities is for materials, which are "environmentally friendly". One of these materials is hydrogen peroxide. Hydrogen peroxide has many potential applications in, for example, chemical oxidation processes. An especially large field of use could be as a bleaching agent for paper.

The demand for hydrogen peroxide is expected to grow at a rapid rate over the years. As such, it could be advantageous to develop an efficient process for the production of this product.

Most hydrogen peroxide (H2O2) is manufactured through a well-known anthraquinone processing. See, for example, Binran, 1 Appl. Chem. , De. Chem. Soc. 302 (Japan 1986). Among the disadvantages of this processing are that it requires the addition of numerous organic solvents, forms many unwanted byproducts, and requires several separation steps. Another method for the preparation of H202 is the cathodic reduction of oxygen in an alkali metal hydroxide solution. However, this procedure requires the entry of significant amounts of electrical energy. Still another method for forming hydrogen peroxide is through catalytic reaction of hydrogen and oxygen with supported or homogeneous platinum group metal catalysts suspended or dissolved in aqueous solutions of sulfonic acid and hydrochloric acid. However, this method requires bringing hydrogen and oxygen into a potently explosive, dangerous mixture at high pressures (for optimal production, usually greater than 7,000 kPa), constituting a serious safety hazard. It may be desirable to have a reactor and a method that eliminates the need for organic solvents, complex electrical equipment, and direct the mixture of potentially explosive reagents. The invention described herein seeks to eliminate many of the difficulties described above. It has been found that using a reactor cell design, where the reagents are controllably separated from one another through a catalytically optimized composite membrane, provides an environment where relatively high pressures can be used without directing the reagent mixture, such like hydroxide and oxygen. The reactor cell uses novel reduction catalysts and can be optimized for many types of reactions. Furthermore, since hydrogen and oxygen can be reacted directly in a single reactor, the use of organic solvents is not necessary.

In one aspect, this invention is a composite membrane for chemical synthesis comprising a substrate, a first side, a second side, wherein the substrate operatively connects the first side and the second side, the first side comprises an oxidation catalyst ( for example, platinum), and the second side comprises a reduction catalyst, which comprises, in elemental or in combination, lanthanum, zinc, cerium, praeseodinium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium , tulio, ytterbium, lutetio, bismuth or Indian. The composite membrane can then be used in an appropriate reactor design. For example, an appropriate reactor design that can be used for the synthesis of hydrogen peroxide by safely reacting hydrogen and oxygen, comprises: (a) the aforementioned composite membrane, wherein the first side is a contact side of hydrogen and the second side is an oxygen contact side; (b) a hydrogen supply chamber for placing the hydrogen in contact with the hydrogen contact side of the composite membrane; and (c) an oxygen supply chamber for placing the oxygen in contact with the oxygen contact side of the composite membrane. The composite membrane is placed between the hydrogen supply chamber and the oxygen supply chamber, so that the hydrogen contact side is operatively connected to the hydrogen supply chamber, and the contact side of oxygen is operatively connected to, the oxygen supply chamber. This type of chemical reactor can also be used to conduct these synthesis reactions where similar conditions are desired.

DETAILED DESCRIPTION OF THE INVENTION It has heretofore been discovered that a composite membrane provides means for the effective synthesis of H2O2 at room temperature, by reacting H2 and O2 safely in a single reactor in the absence of organic solvents. Using the reduction catalysts set forth above, this composite membrane can also be effective for performing many other chemical synthesis options, such as the following: oxidation of an alkene (for example propylene) to an alkylene oxide (for example propylene oxide); H2SO4 from SO2, H2O, and O2 (see, Langer et al., "Chem icals With Power", Chemtech 226, 229 (April 1 985)); amine dyes from organo-nitro compounds (see Spillman et al., "Why Not Make Chemicals in Fuel Cells?", Chemtech 1 76, 1 82 (March 1 984)); and phenol from benzene (see Otzuka et al., "Direct Synthesis of Phenol from Benzene duri ng H2O2 Fuel Cell Reactions", 1 39 (No. 9) J. Electrochem Soc. 281 (1992)). The synthesis of H2O2 is currently felt to be of significant importance and should be discussed more specifically in the present. However, in view of the following description, one skilled in the art is able to adapt the composite membrane of this invention to other reactions, and the discussion specific only to the synthesis of H2O2 does not represent limiting the scope of this invention. Specifically, a first aspect of this invention is a composite membrane comprising a substrate, a first side and a second side, wherein the substrate operatively connects the first side and the second side, the first side of the composite membrane comprises a catalyst of oxidation and the second side of the composite membrane comprises a reduction catalyst. The catalysts can be either supported or unsupported and can be either discrete or non-discrete layers. A "discrete" layer, for the purposes of this invention, is one that is attached, or adjacent, to the substrate, and a "non-discrete" layer is one in which the catalyst is integrally mixed directly with the substrate. The substrate can be any membrane exhibiting a sufficient ionic conductivity, preferably cationic conductivity, under the method of this invention. However, for hydrogen peroxide, it is additionally necessary that the substrate inhibit the conduction of peroxyl anions. A person skilled in the art is capable of determining effective substrates to perform this function. Generally, the substrate is a polymeric membrane. Typical polymeric membranes are also organic, such as polymeric perfluorosulfonic acid (PFSA) or polycarboxylic acids. PFSA is an ion exchange membrane that has negatively charged groups attached within the membrane. For a discussion of some commonly preferred PFSA polymers, and methods for preparing such polymers, see De Vellis et al., U.S. Pat. No. 4,846,977, column 5, lines 1-36 (incorporated herein by reference). Also see T. D. Sierke, "Perfluorinated lonomer Membranes", ACS Symposium Series No. 180, pp. 386-88 (1982) (incorporated herein by reference). An example of a commercially available PFSA polymer is NAFION ™ (E.l. du Pont de Nemours and Company). Additional organic polymer membranes can be materials such as sulfonated styrene grafts on a polytetrafluoroethylene base structure (eg, RAIPORE ™ membranes, available from RAI Research Corporation), and entangled sulfonated copolymers of vinyl compounds (eg, TYPE CR membranes). ™, available from Lonics, Inc.). Since organic polymers are very common, inorganic polymers such as ceramic membranes, gels, siloxanes and salt bridges are also possible. The oxidation catalyst can be any material that facilitates oxidation under conditions where it is used. One skilled in the art is capable of determining the effective oxidation catalysts to effect oxidation in a desired reaction without undue experimentation. For example, in the synthesis of H202, it is necessary that the first layer of the composite membrane oxidizes the hydrogen to protons and electrons. Effects of useful catalysts for the first side in the synthesis of H2O2 include: platinum, palladium, gold, silver, mercury, iridium, ruthenium, ruthenium dioxide, nickel, nickel boride, sodium-tungsten bronzes, tungsten trioxide, carbide of tungsten, molybdenum sulphide, cobalt carbide, cobalt sulphide, cobalt molybdate, platinized boron carbide, copper phthalocycline, palladium acetylacetonate, niobium, and mixed metal and spinel electrocatalysts. Other examples of potential oxidation agents are generally described in Appleby et al., "Electrocatalysis of Hydrogen", Fuel Cell Handbook 322-35 (Van Nostrand Reinhold 1989), incorporated herein by reference. Preferred oxidation catalysts for the synthesis of H202 include palladium, platinum, iridium and combinations thereof. The reduction catalyst on the second side of the composite membrane comprises elemental or in combination, lanthanum, zinc, cerium, praeseodinium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, bismuth or indian. By "combination form", it is meant that the reduction catalysts may also include mixtures and compounds that contain at least one of the elements described above. It should be understood that "oxide" means including partial oxides, where a "partial oxide" is a mixture of different stoichiometries of oxygen and metal, so that the total stoichiometry of the metal oxide is not a simple integer Examples of mixtures of Reduction catalysts include: lanthanum-manganese, and indium-tin oxide, praeseodium-indium oxide, and lanthanide salts of polyunsaturated acid such as lanthanum phospho-nitolystate (LaPW12O 0). Preferred reduction catalyst metals for the synthesis of H2O2 include gadolinium, zinc, lanthanum, mixtures thereof, and compounds thereof. Methods for depositing the metallized layers on, and incorporating them into, substrates are well known in the art and one skilled in the art is capable of optimizing these deposition methods to form the composite membrane of this invention. Examples of such deposition methods are described by Nidola and other US Pat. 4,364,803 (1982), Wilson, patent of E. U.A. 5,211, 984 (1993), and Takenaka et al., Patent of E. U.A. 4,328,086 (1982). The relevant teachings of these references are incorporated herein by reference. When a discrete layer of the catalyst is used, preferred embodiments of the present invention employ a layer thickness for the first and second sides of the composite membrane no greater than 35 microns (μ). Therefore, the particle size of the preferred catalyst is also not greater than 35μ. Most preferably, the particle size is less than 10μ. A second aspect of this invention is a reactor comprising the aforementioned composite membrane. The reactor includes a first reagent supply chamber for placing a first reagent in contact with the first side of the composite membrane, and a second reagent supply chamber for placing a second reagent in contact with the second side of the composite membrane. The composite membrane is positioned between the first reagent supply layer and the second reagent supply chamber, so that the first side of the composite membrane is operatively connected to the first reagent supply chamber and the second side of the reagent supply chamber. the composite membrane is operatively connected to the second reagent supply chamber. Typically, the first reagent supply chamber faces the first side, and the second reagent supply chamber faces the second side. With respect to the supply chamber and the composite membrane, "operatively connected" means that the supply chambers are arranged so that the relevant compositions contained therein can be placed in contact with the appropriate sides of the composite membrane forming a adjacent surfaces between the relevant compositions and the appropriate sides. "Supply chamber" includes any container, space, zone, or the like, capable of substantially containing and facilitating contact between any relevant composition and an appropriate side of the composite membrane. In addition, each chamber desirably has at least one aperture for delivery and / or removal of the relevant compositions, reaction products, or both. The first and second sides of the composite membrane are also operatively connected to each other. With respect to the "operative connection" of these sides to each other, the operational connection is such that both ions and electrons can be conducted from the first side to the second side. The electrons can be conducted either externally, internally, or both externally and internally. An example of an external electrical operational connection is the use of current collector plates in electrical contact on each side of the composite membrane, and also the electrical contact between each other through placement of cables between the plates through a busbar. short external circuit. An example of an internal electrical operational connection is to have an intimate multiple phase mixture of an electron conducting material with an ion conducting material, wherein the electron conductive phase is internally disposed through the ion conductive phase. "Internationally dispersed" means that the phases, although independent and substantially continuous, are integrally intermixed so that the electron conductive phase is an interpenetration network and not exclusively placed externally in relation to the ion conductive phase. This type of multi-phase mixture is described in the patent application of E.U.A. copending series number 08/239, 017 (incorporated herein by reference). The chemical reactor may further comprise means for supplying the first reagent to the first reagent supply chamber, and means for supplying the second reagent to the second reagent supply chamber. Each of these means can be any conventional system or apparatus that transports relevant compositions from one source of the compositions to the respective chamber. For example, each medium may be a pump and a conduit or passage operatively connected to a source of the composition, such that the relevant composition is pumped from its source, through the conduit, and into its respective chamber. The chemical reactor may further comprise a similar type of means for recovering the reaction products, such as hydrogen peroxide, from the reduction chamber. In a preferred reactor, the first side of the composite membrane is a hydrogen contact side, the second side is an oxygen contact side, the first reagent supply chamber is a hydrogen supply chamber, and the second chamber is Reagent supply is an oxygen supply chamber. Therefore, in the synthesis of H2O2, for example, the first side of the composite membrane oxidizes hydrogen to protons and electrons, and the second side, in combination with the electrons produced on the first side, reduces oxygen to oxygen ions. at least two electrons and cations have been provided to the oxygen contact side of the composite membrane, H2O2 is produced. A third aspect of this invention is a method for using the reactor described above. A preferred embodiment of this method is the synthesis of hydrogen peroxide. However, the synthesis of other compositions is possible using the reactor of this invention. Said methods of synthesis will be more apparent to those skilled in the art in view of the following method, specifically described, for the synthesis of hydrogen peroxide. For the synthesis of hydrogen peroxide, one step of the method comprises placing the hydrogen in contact with the aforementioned hydrogen contact side of the composite membrane in the preferred reactor to produce at least one electron and at least one and proton. For example, when hydrogen is introduced in the H2 form, the oxidation catalyst (for example, Pt) provides oxidation to two protons and two electrons. However, hydrogen can be introduced in any form (for example, a mixture or a compound containing hydrogen), provided that the contact side of hydrogen produces at least one electron and at least one proton. A mixture containing desirable hydrogen is hydrogen gas in mixture with water. The water helps keep the composite membrane hydrated, thus allowing a good ionic conductivity. A second step of the method comprises placing the oxygen in contact with the oxygen contact side of the composite membrane. The oxygen can be placed in contact with the composite membrane as pure O2, or as any mixture or compound containing oxygen. A mixture containing desirable oxygen is a mixture of water and water. Examples of means for placing er a hydrogen / water or oxygen / water mixture in contact with the composite membrane is er bubbling hydrogen or oxygen through the water before feeding the gas into the reactor, or placing the gas hydrogen or oxygen in contact with the composite membrane as a flow segmented with water. Generally, water helps to dilute the hydrogen peroxide product, thus producing its potential decomposition. As with the contact side of hydrogen, the water also helps keep the composite membrane hydrated. A third step of the method comprises conducting at least one electron and at least one proton produced on the hydrogen contact side of the composite membrane, towards an abutting surface between the oxygen contact side of the composite membrane and the oxygen. At least one electron and at least one proton react with oxygen in the presence of the reduction catalyst to form the reaction product, and when a total of two electrons and two protons are reacted with oxygen, hydrogen peroxide is produced . This chemical synthesis method can be, if desired, conducted at an elevated temperature. Generally, the temperature should not exceed a temperature at which any of the materials of the composite membrane, or any desired product, significantly decomposes or degrades. This temperature, and the importance of the degradation of the composite membrane, vary according to the composition of the composite membrane. One skilled in the art is able to determine both the appropriate temperatures for conducting various synthesis reactions and whether decomposition is important, in the synthesis of H 2 O 2, the method of this invention is preferably carried out in the reactor at a higher temperature than , or equal to 2 ° C. Preferably, the temperature is also less than or equal to 50 ° C, preferably less than or equal to 30 ° C, and most preferably less than or equal to 10 ° C. In addition, the hydrogen and oxygen feed streams are preferably placed in contact with the composite membrane at a pressure greater than or equal to 689 kPa, preferably greater than or equal to 33447 kPa, and most preferably greater than or equal to 4826 kPa. Finally, it is preferred to remove any reaction product from the second side of the composite membrane. This isolates the desired reaction products and minimizes unwanted side reactions such as the decomposition of H2O2.

EXAMPLES The invention will now be explained through the consideration of the following examples, which are intended only to illustrate the use of the invention.

EXAMPLE 1 A 10.2 x 10.2 cm square polymeric perfluorosulfonic acid (PFSA) membrane with an equivalent weight of 800, with a thickness of 127 microns was converted to a sodium salt form by heating in a caustic solution (1 M NaOH) for 1 hour. hour and rinsing suddenly in deionized water (DI) to form the substrate. The oxidation and reduction catalysts were applied independently to cover the areas of 3.0 x 3.5 cm on each side of the substrate through the direct painting method (DPO). For the DPO method, two inks were made, one for each catalyst. Both inks were made by forming suspensions of a catalyst on carbon black with a propylene carbonate carrier and an ionomeric binder. The oxidation catalyst on the carbon black (available from E-TEK, Inc.) was made by combining platinum and carbon black at 20% by weight of Pt. The reduction catalyst on carbon black was made by combining zinc powder ( available from Aldrich Chemical Company) and carbon black at 20% by weight Zn. The ionomeric binder consisted of 5% by weight of NAFION ™ in mixed alcohols and a water solution (available from E l. Du Pont de Nemours and Company) and was added to each of the catalyst mixtures on carbon black in a amount such that the total weight of the catalyst on the carbon black was 2.5 times greater than the weight of PFSA in the PFSA / mixed alcohol / H20 binder. The propylene carbonate (available from Aldrich Chemical Company) was added to each of the inks in such an amount that the propylene carbonate was 2.5 times the total amount of the catalyst on carbon black, by weight. The ink of the reduction catalyst was placed by painting the substrate in an amount sufficient to provide a metal loading of 1.25 mg / cm2 and the ink of the oxidation catalyst was placed as paint on the opposite side of the substrate in an amount sufficient to provide a Total metal loading of 0.3 mg / cm2. The inks were placed as paints at the same time on the substrate, while the substrate was placed on a vacuum board of frit, hot (50 ° C) for 30 minutes. The table ensured that the substrate remained flat and aided the evaporation of propylene carbonate and binder solvents. Evaporation of the propylene carbonate vehicle and the binder solvents formed a composite membrane having a layer of oxidation agent incorporated on the hydrogen contact side and a layer of reducing agent incorporated on the oxygen contact side. In order to protect the active catalysts on both sides of the composite membrane for the next heat compression step, a 6.35 x 6.35 cm sandwich was formed by placing on each side of the composite membrane the following (in order): a sheet non-adherent of a KAPTON ™ polyimine film with a thickness of 50.8 microns; a sheet of rubber is reinforced with glass; a stainless steel plate treated with chrome, polished, with a thickness of 1 .59 mm. This composite membrane sandwich was preheated to 150 ° C and at a minimum pressure (ie, the plates will only touch each other) for 5 minutes and then compressed with heat at 150 ° C and 1380 kPa for 5 minutes. The composite membrane compressed by heat was then removed from the press as the sandwich and cooled to room temperature. After cooling to room temperature, the composite membrane was removed from the sandwich and then re-protonated from its sodium salt form to its proton form by immersing it in 1 N of H2SO4 for 30 minutes at room temperature. The composite membrane that was re-protonated was then flattened by placing it upside down on the hot frit vacuum board (50 ° C) for 30 minutes. The composite membrane that was re-protonated was then operatively connected to a fuel cell reactor, flux-field, parallel channel (available from Fuel Cell Technologies, Inc.) so that the oxidation catalyst looked into the hydrogen supply chamber of the reactor and the revolution catalyst looked into the oxygen supply chamber of the reactor. reactor. The filling of both chambers was a carbon fabric diffuser impregnated with TEFLON ™ / carbon black (available from E-TEK, Inc., as ELAT ™). The reactor was operated under short circuit conditions on a fuel cell test stand (also available from Fuel Cell Technologies, Inc.). The operating pressures for the reactor were 310 kPa for the hydrogen contact side of the composite membrane and 413 kPa for the oxygen contact side. The reactor was operated at room temperature (25 ° C) and the hydrogen gas feed stream was wetted by bubbling it through water at 50 ° C before introducing it into the hydrogen supply chamber of the reactor. The gas and oxygen feed stream was left dry. The product was collected through an ejector from the outlet of the oxygen supply chamber of the reactor. The reactor operated at approximately 100 mA / cm2 and produced a peroxide solution of 3.1% by weight. Similar results were obtained when the same processing of this example doubled with the exception that the zinc oxide (ZnO) was deposited on the carbon black instead of the zinc powder. The ZnO was deposited from a salt of Zn (OAc) 2 on carbon black and calcined in the air at 120 ° C for 1 hour.

EXAMPLE 2 A composite membrane was produced as described above, however, the reduction catalyst in the reduction catalyst ink was 20% gadolinium oxide on carbon black (weight ratio of Gd to Gd plus carbon weight) made of Gd (NO3) 3 6 crystalline H2O (water-soluble gadolinium salt available from Aldrich Chemical Company). The gadolinium on the carbon black was first made by dissolving the crystals of the gadolinium salt (0.72 g of salt / g of carbon) in a minimum amount of water. Second, carbon black was added to the salt solution to form a paste, as a method of incipient dryness known in the art. Then, the water was removed from the paste by heating the paste moderately while grinding in a mortar and grinder. The resulting Gd + 3 / carbon powder was then placed in a convection oven and kept at a temperature of 120 ° C for 30 minutes to form the reduction catalyst on the carbon black. The resulting reduction catalyst ink (including the propylene carbonate carrier and an ionomeric binder, as in Example 1) was placed as paint on the substrate in an amount sufficient to provide a metal loading of 0.1 mg / cm2 and the oxidation catalyst ink (20% Pt on the carbon and including the propylene carbonate carrier and an ionomeric binder) was placed as paint on the opposite side of the substrate in an amount sufficient to provide a metal loading of 0.30 mg / cm. In contrast to Example 1, the resulting composite membrane was left in its sodium salt form after heat compression. The composite membrane was operated in the same fuel cell reactor (as in Example 1), however, the reactor was operated on a high pressure fuel cell test standard, which was able to operate at a pressure up to 63.27 kg / cm2. Similar to the above, the hydrogen supply chamber was filled with ELAT ™, however, the oxygen supply chamber was filled with an untreated carbon paper, with a thickness of 76.2 microns (available from Spectrocarb, Corp.) . The inlet pressure of the hydrogen gas, which was in contact with the oxidation catalyst on the hydrogen contact side of the composite membrane, was 4830 kPa and that of the oxygen gas, which was in contact with the reduction catalyst on the oxygen contact side of the composite membrane was also at 4830 kPa. The oxygen gas was fed to the reduction catalyst as a segmented flow of 02 with deionized water (DI), the water being added to the gas at a rate of 0.2 mL / min. The reactor was operated at room temperature with a continuous gas feed for a period of 14 minutes. A reaction product was formed and combined with the added water to produce a concentration of 3.0% by weight of hydrogen peroxide. By measuring the electrical current that passes through this facility via the voltage difference across a calibrated short-circuit bar, it was determined that an electron that passes through the fixation for each hydrogen atom that was consumed forms a product ( water or peroxide). A weight determination of the total product formed was 2.87 grams. Together with these measurements the calculation of the selectivity of the reaction in terms of moles of peroxide formed per mole of hydrogen was allowed. For this example, 0.95 amps (passed) of the hydrogen contact side to the oxygen contact side were generated during the 14 minute test, corresponding to a selectivity of hydrogen for hydrogen peroxide of 62 mol%. The maximum hydrogen peroxide calculated could be 0.14 g at 100% conversion efficiency for this current and this time. When this composite membrane was operated with an external water flow of 0.05 mL / minute, 4.1% by weight of hydrogen peroxide was generated at a hydrogen selectivity of 44 mol%.

EXAMPLE 3 Procedures identical to those described in Example 2 above were followed, except for the following: (1) lanthanum nitrate (same work as Gd nitrate) was used for the oxygen reduction catalyst; and (2) after the compression step with heat, the composite membrane was again protonated from its sodium salt form to its proton form, cooling first to room temperature, then immersing in 1 N of H2SO4 for 30 minutes at room temperature. The composite membrane that was re-protonated had to be flattened again by placing it down on the hot frit vacuum table (50 ° C) for 30 minutes. While conducting the synthesis reaction with this composite membrane, the water flow to the reactor was 0.2 μL / minute, and the resulting product stream was 1.3% by weight of hydrogen peroxide with a hydrogen selectivity for 70% molar hydrogen peroxide.

EXAMPLE 4 Procedures identical to those described in Example 3 were conducted, with the exception that lanthanum phospholitungstate (LaPW12O40) was used instead of lanthanum nitrate. While conducting the synthesis reaction with this composite membrane, the water flow to the reactor was 0.8 mL / minute, and the product collected was 1.1% by weight of hydrogen peroxide with a selectivity of hydrogen for hydrogen peroxide. 72 molar hydrogen.

Other embodiments of the invention will be apparent to those skilled in the art from a consideration of this specification or practice of the invention described herein. It is intended that the specification and examples be considered only as illustrative, with the true scope and spirit of the invention being indicated in the following claims.

Claims (1)

1. CLAIMS 1. - A composite membrane comprising a substrate, a first side, and a second side, wherein the substrate operatively connects the first side and the second side, the first side comprises an oxidation catalyst, and the second side comprises a reduction catalyst , which comprises, in elementary form in combination, lanthanum, zinc, cerium, praeseodium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, bismuth or indium. 2 - The composite membrane according to claim 1, wherein the reduction catalyst comprises, in elemental or combination form, gadolinium, zinc or lanthanum. 3. The composite membrane according to claim 1, wherein the reduction catalyst is an oxide. 4. The composite membrane according to claim 1, wherein the reduction catalyst is lanthanum phospho-nitropungate. 5 - The composite membrane according to claim 1, wherein the oxidation catalyst comprises, in elementary or combination form palladium, platinum, or iridium. 6 - The composite membrane according to claim 1, wherein the substrate is a polymer-based membrane, 7 - The composite membrane according to claim 6, wherein the polymer-based membrane is organic. 8 -. 8 - The composite membrane according to claim 7, wherein the polymeric, organic base membrane comprises a polymeric perfluorosulfonic acid. 9. A reactor comprising: (a) the composite membrane of claim 1; (b) a first reagent supply chamber for placing a first reagent in contact with the first side of the composite membrane; and (c) a second reagent supply chamber for placing a second reagent in contact with the second side of the composite membrane; wherein the composite membrane is placed between the first reagent supply chamber and the second reagent supply chamber, so that the first side of the composite membrane operatively connects the first reagent supply chamber, and the second side of the Composite membrane operatively connects the second reagent supply chamber. 1. The reactor according to claim 9, wherein the first side is a hydrogen contact side, the second side is an oxygen contact side, the first reagent supply chamber is a This is a second chamber of oxygen supply, and the second chamber of reagent supply is a second chamber of oxygen supply. 1 - The reactor according to claim 10, further comprising means for recovering hydrogen peroxide. 12. A method for the synthesis of hydrogen peroxide using the reactor of claim 10, wherein the method comprises: (a) placing the hydrogen in contact with the hydrogen side of the composite membrane to produce at least one electron and at least one proton; (b) placing the oxygen in contact with the oxygen contact side of the composite membrane; and (c) conducting at least one electron and at least one proton produced in step (a) to an abutting surface between the oxygen contact side of the composite membrane and oxygen, so that at least one electron and at least and proton react with the oxygen to form a reaction product comprising hydrogen peroxide. 13. The method according to claim 12, wherein the hydrogen in step (a) is provided as a mixture containing hydrogen. 14 - The method according to claim 13, wherein the mixture containing hydrogen comprises hydrogen and water. 1 - The method according to claim 12, wherein the hydrogen in step (a) is provided as a hydrogen-containing compound. 16. - The method according to claim 12, wherein the oxygen in step (b) is provided as an oxygen-containing mixture. 17. The method according to claim 16, wherein the oxygen-containing mixture comprises oxygen and water. 18. The method according to claim 12, wherein the reactor is maintained at a temperature of 2 ° C to 30 ° C. 19. The method according to claim 12, wherein the hydrogen and oxygen are placed in contact with the composite membrane at a pressure greater than 689 kPa.