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WO1999002264A1 - Membrane et procede destines a la synthese du peroxyde d'hydrogene - Google Patents

Membrane et procede destines a la synthese du peroxyde d'hydrogene Download PDF

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Publication number
WO1999002264A1
WO1999002264A1 PCT/US1998/012156 US9812156W WO9902264A1 WO 1999002264 A1 WO1999002264 A1 WO 1999002264A1 US 9812156 W US9812156 W US 9812156W WO 9902264 A1 WO9902264 A1 WO 9902264A1
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WO
WIPO (PCT)
Prior art keywords
membrane
hydrogen
oxygen
contact side
catalyst
Prior art date
Application number
PCT/US1998/012156
Other languages
English (en)
Inventor
James A. Mcintyre
Edgar S. Sanders, Jr.
Robert D. Mahoney
Steven P. Webb
Craig B. Murchison
David A. Hayes
Original Assignee
The Dow Chemical Company
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by The Dow Chemical Company filed Critical The Dow Chemical Company
Priority to AU80675/98A priority Critical patent/AU8067598A/en
Publication of WO1999002264A1 publication Critical patent/WO1999002264A1/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/50—Catalysts, in general, characterised by their form or physical properties characterised by their shape or configuration
    • B01J35/58—Fabrics or filaments
    • B01J35/59—Membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J12/00—Chemical processes in general for reacting gaseous media with gaseous media; Apparatus specially adapted therefor
    • B01J12/007—Chemical processes in general for reacting gaseous media with gaseous media; Apparatus specially adapted therefor in the presence of catalytically active bodies, e.g. porous plates
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/24—Stationary reactors without moving elements inside
    • B01J19/2475—Membrane reactors
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B15/00—Peroxides; Peroxyhydrates; Peroxyacids or salts thereof; Superoxides; Ozonides
    • C01B15/01—Hydrogen peroxide
    • C01B15/029—Preparation from hydrogen and oxygen
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/00049—Controlling or regulating processes
    • B01J2219/00051—Controlling the temperature
    • B01J2219/00074—Controlling the temperature by indirect heating or cooling employing heat exchange fluids
    • B01J2219/00076—Controlling the temperature by indirect heating or cooling employing heat exchange fluids with heat exchange elements inside the reactor
    • B01J2219/00085—Plates; Jackets; Cylinders
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/00049—Controlling or regulating processes
    • B01J2219/00162—Controlling or regulating processes controlling the pressure

Definitions

  • This invention relates to a membrane and method for its use in synthesis of hydrogen peroxide by reaction of hydrogen and oxygen.
  • the trend in commodities today is for materials and processes which are "environmentally friendly".
  • One such material is hydrogen peroxide.
  • Hydrogen peroxide has many potential applications in, for example, chemical oxidation processes.
  • One especially large field of use is as a bleaching agent in the pulp and paper industry.
  • the demand for hydrogen peroxide is expected to grow at a rapid rate for many years.
  • the current commercially practiced processes for synthesis of hydrogen peroxide are inefficient and have many disadvantages. As such it would be advantageous to develop a more efficient process for production of this commodity.
  • a second method for avoiding excessive mixing of hydrogen and oxygen is to use fuel and reactor cells such as Proton Exchange Membrane (PEM) fuel cells.
  • PEM Proton Exchange Membrane
  • Such cells typically require formation and conductance of electrons and ions across the fuel cell by means of an electrochemical potential, they typically require complex catalytic, ionic, and electrical equipment. This equipment is generally inappropriate for large scale manufacturing operations.
  • a method for producing hydrogen peroxide without excessive mixing of the hydrogen and oxygen using a palladium metal membrane is unsuitable. For example, such a membrane is expensive, susceptible to poisoning, requires relatively higher temperatures for satisfactory hydrogen fluxes, and may be lifetime limited due to hydrogen embrittlement.
  • the invention disclosed herein includes a membrane which is useful for synthesis of hydrogen peroxide.
  • the membrane has an oxygen contact side and a hydrogen contact side and comprises a porous hydrophobic catalyst layer facing the oxygen contact side and a gas flux control layer facing the hydrogen contact side.
  • the gas flux control layer is positioned between the hydrogen contact side and the porous hydrophobic catalyst layer such that the flux of hydrogen may be controllably delivered to the porous hydrophobic catalyst layer.
  • An advantage of this method is that hydrogen peroxide may be produced at attractive rates using a considerably simplified process when compared to existing technology.
  • the porous hydrophobic catalyst layer advantageously permits oxygen to be transported to a reactive interface with hydrogen while inhibiting the flooding of water through the porous hydrophobic catalyst layer from the oxygen side of the membrane.
  • Another advantage of this invention is that it provides an effective mechanism for controlling the flux of hydrogen as it is transported to a reactive interface with oxygen.
  • FIGURE 1 is one embodiment of this invention. It illustrates a membrane having a Hydrogen Contact Side 1 and an Oxygen Contact Side 2.
  • a Gas Flux Control Layer 3 faces the Hydrogen Contact Side 1 and is positioned between the Hydrogen Contact Side 1 and Porous Hydrophobic Catalyst Layer 5, more specifically between the Hydrogen Contact Side 1 and the Macroporous Support 4.
  • the Macroporous Support 4 is positioned substantially between the Porous Hydrophobic Catalyst Layer 5 and the Gas Flux Control Layer 3. Covering the Oxygen Contact Side 2 surface of the Porous Hydrophobic Catalyst Layer 5 is an Erosion Control Layer 6.
  • FIGURE 2 is another embodiment of the invention.
  • the Membrane 9 (see FIGURE 1), having the Hydrogen Contact Side 1 and the Oxygen Contact Side 2, separates the two chambers.
  • the Hydrogen Contact Side 1 of the membrane faces the Hydrogen Supply Chamber 8 and the Oxygen Contact Side 2 faces the Oxygen Supply Chamber 7.
  • Two outlets 10 for withdrawal of product and excess gas are located at opposite ends of the reactor from the two inlets.
  • FIGURE 3(a) depicts a cross section of a reactor containing "serpentine" channels 11 (depicted in FIG. 3(b)) for this invention.
  • Serpentine channels refer, simply, to a series of Oxygen Supply Chambers 7 on the Oxygen Contact Side 2 of the Membrane 9 and a corresponding series of Hydrogen Supply Chambers 8 on the Hydrogen Contact Side 1 of the Membrane 9.
  • the membrane of this invention requires a porous hydrophobic catalyst layer and a gas flux control layer.
  • the porous hydrophobic catalyst layer faces an oxygen contact side of the membrane and the gas flux control layer faces a hydrogen contact side of the membrane.
  • the oxygen contact side of the membrane may simply be a surface of one side of the porous hydrophobic catalyst layer.
  • the hydrogen contact side of the membrane may simply be a surface of one side of the gas flux control layer.
  • the gas flux control layer is positioned between the hydrogen contact side and the porous hydrophobic catalyst layer such that the flux of hydrogen may be controllably delivered to the porous hydrophobic catalyst layer.
  • This membrane is useful for synthesis of hydrogen peroxide by placing hydrogen in contact with the hydrogen contact side of the membrane, placing oxygen in contact with the oxygen contact side of the membrane, and allowing the hydrogen and oxygen to be transported into the membrane to an interface at the porous hydrophobic catalyst layer. When the oxygen and hydrogen are contacted at the catalyst layer, reaction may take place, producing hydrogen peroxide.
  • the word “hydrophobic”, when used in conjunction with the catalyst layer, is meant to mean that the layer substantially inhibits the spontaneous intrusion of water from the oxygen contact side of the membrane into the catalyst layer. "Spontaneous intrusion of water” can occur if the catalyst layer is substantially hydrophilic such that, water contacting the layer will wet the pores of the catalyst layer and be retained by capillary action unless the differential pressure across the layer exceeds the "bubble-point” pressure.
  • the word “porous”, when used in conjunction with the catalyst layer is meant to mean that the layer permits oxygen to access catalyst sites in the catalyst layer without being significantly impeded by pore size and/or spontaneous intrusion of water into the pores. Therefore, by having the catalyst layer be both hydrophobic and porous, maximum interaction of hydrogen and oxygen is permitted at the catalyst layer.
  • the porous hydrophobic catalyst layer comprises a catalyst and a substantially hydrophobic material.
  • the porous hydrophobic catalyst layer may comprise a catalytic material and a hydrophobic composite material wherein the composite comprises a first material that has been treated with a second material of low surface energy such that the composite exhibits a contact angle with water of greater than ninety degrees.
  • the catalytic material may be intermixed with the hydrophobic material, or may be organized as a more discrete layer (within the porous hydrophobic catalyst layer) wherein the hydrophobic material may be part of a layer which is positioned primarily towards the oxygen contact side of the porous hydrophobic catalyst layer and the catalytic material is part of a layer which is positioned primarily towards the hydrogen contact side of the porous hydrophobic catalyst layer.
  • Examples of materials which are substantially hydrophobic include: styrene divinylbenzene copolymers; polyethylene, polypropylene or ethylene- propylene copolymers; silica which has been rendered hydrophobic by treatment with a silane or with fluorine or a fluorinated compound; fluorinated polymers and copolymers; carbon which has been rendered hydrophobic by treatment with a silane or with fluorine or a fluoridated compound; and combinations thereof.
  • the catalyst is typically an oxygen reducing catalyst.
  • the oxygen reducing catalyst comprises a metal selected from the group consisting essentially of platinum, palladium, rhodium, rhenium, indium, gold, silver, copper, cobalt, iron, nickel, and combinations thereof.
  • catalysts which are beneficial for oxygen reduction such as: silver, gold, bismuth, palladium, cobalt (see, for example, Putten et al., J. Chem. Soc, Chem. Commun. All (1986), incorporated herein by reference), niobium-titanium, lanthanum-manganese mixtures, indium-tin oxide mixtures, praseodymium-indium oxide mixtures, metal phthalocyanines (see, for example, Cook et al., 137 [No. 6] J. Electrochem. Soc. 2007 (1990), incorporated herein by reference), metal porphyrins (see, for example, Chan et al., 105 J. Am.
  • oxygen reducing catalysts comprise at least palladium.
  • additive metals may also be useful, in combination with the above-described oxygen reducing catalysts, such as lead, zinc, copper, gallium, tin, and bismuth.
  • One embodiment for the catalyst is to utilize the catalytic material such that it is present in at least two different oxidation states.
  • Catalysts may be in the form of pure materials, or they may be supported on carriers.
  • a preferable carrier is selected from the group consisting of carbon, silica, titania, zirconia, alumina, lanthanum oxides, cerium oxides, zeolites, heteropolyacids, alkaline earth sulfates, alkaline earth phosphates, titanium silicates, vanadium silicates, and combinations thereof.
  • one embodiment of this invention is to deposit ultrafine gold particles (for example particle having a radius of less than 10 nanometers) on one of the above carriers, such as a titanium silicate.
  • the catalyst, or catalyst with carrier may then be rendered hydrophobic by any appropriate method such as treating it, mixing it, or forming a composite, with the substantially hydrophobic material.
  • one further embodiment of this invention is to also include at least one hydrogen peroxide selectivity increasing additive in the porous hydrophobic catalyst layer.
  • Such additive may be doped into the porous hydrophobic catalyst layer using a pretreatment process.
  • Methods for incorporating and depositing catalysts and other additives onto and into other materials are well known in the art. In light of the disclosure herein, one of skill in the art is capable of optimizing these deposition methods to form the porous hydrophobic catalyst layer. Examples of membrane fabrication and catalyst deposition methods are disclosed in: A. B.
  • an ion exchange material is useful for enhancing the productivity of the catalyst.
  • an ion exchange material will capture the soluble catalyst and allow: (1) reaction back to the insoluble form by an added reactant (oxidant or reductant), and/or (2) regeneration of the insoluble catalyst in a separate step. Therefore, the ion exchange material inhibits catalyst loss without removing spent catalyst from the system nor introducing materials that may cause product decomposition. For example, when a membrane is used without the ion exchange membrane, conditions of operation typically oxidize and dissolve the catalyst into the product stream.
  • PFSA perfluorosulfonic acid
  • the membrane also includes a gas flux control layer which faces the hydrogen contact side of the membrane.
  • the gas flux control layer is positioned between the hydrogen contact side and the porous hydrophobic catalyst layer such that the flux of hydrogen may be controllably delivered to the porous hydrophobic catalyst layer.
  • the gas flux control layer must allow hydrogen to be delivered from the hydrogen contact side to the oxygen contact side at a rate at least equal to that required for maintaining an acceptable minimum rate of reaction with oxygen.
  • the gas flux control layer must also prevent excessive flow of hydrogen to the oxygen contact side, since such excessive flow can create a danger of an explosion, or necessitate venting or recycle of large volumes of undesirably mixed gases, adding complicated and costly steps to the synthesis reaction.
  • the gas flux control layer also preferably inhibits excessive oxygen transport across the membrane.
  • Fluor as used herein shall mean the flow rate of a permeating species per unit cross-sectional area of the gas flux control layer (that is (standard cc)/(cm 2 -sec), wherein "standard” is equal to 0° C and 760 mmHg pressure).
  • the gas flux control layer is selected from a material which is effective for at least one of the following means for transporting hydrogen from the hydrogen contact side of the membrane: solution-diffusion transport; viscous flow; Knudsen flow; and any combination thereof.
  • Equation I describes this mechanism of transport:
  • N ss is the steady state flux
  • / is the thickness
  • ⁇ p is the partial pressure driving force across the membrane and is the selectivity.
  • N v (Equation 3) wherein S is the cross sectional area, r is the radius, p is pressure, ⁇ is viscosity, R is the gas constant, I is the membrane thickness, and T is temperature.
  • S and r are characteristic of the pore structure for a given membrane and ⁇ is a physical property of the gas. Viscous flow differs from solution-diffusion flow in that the driving force is the pressure difference rather than the partial pressure difference across the membrane. Another major difference is that viscous flow increases with system pressure as well as differential pressure. Because of this, the viscous permeance (Nv/Dp) and permeability are an increasing function of pressure.
  • Knudsen flow Like viscous flow, Knudsen flow describes flow in a small channel or capillary (see Hwang, S. and Kammermeyer, K. Membranes in Separations, John Wiley & Sons 1975). However, in Knudsen flow, the diameter of the channel is less than the mean free path of the molecule and the molecule has more collisions with the wall of the capillary than with other molecules. Because of this, the driving force for Knudsen flow is the partial pressure difference across the membrane. Knudsen flow can be described by the following equation:
  • N ⁇ is the flux
  • r is the radius of the capillary
  • R is the gas constant
  • M w is the molecular weight
  • T is the temperature
  • / is the membrane thickness
  • ⁇ p is the partial pressure difference across the flow channel.
  • the selectivity of the membrane is the square root of the ratio of the reciprocal molecular weight of the two gases:
  • Knudsen selectivity is intermediate to viscous and solution-diffusion selectivity and much closer to viscous flow selectivity.
  • a major difference between Knudsen flow and viscous flow is that the Knudsen flow permeability coefficient is independent of pressure. Like S-D flux, Knudsen flux increases linearly with partial pressure.
  • Solution-Diffusion membranes are typically used for gas separations. This is primarily due to the high selectivity achievable by this mechanism. In gas separations, a large differential pressure is imposed on the membrane to maximize productivity and promote the enhanced flux of one component of the mixture. Membranes for membrane reactor applications have different requirements. The purpose of the membrane reactor is to separate the pure bulk phases of the two potentially dangerous reactive species and to controllably react (mix) the reactants. For a typical membrane-type reactor, two essentially pure gases are flowing on opposing sides of the membrane. Although the pressure differential across the membrane can be relatively small, the partial pressure difference across the membrane is high for both gases. In a solution diffusion membrane, this causes diffusion of the low pressure gas into the high pressure gas. Flammability limits can be reached by back-diffusion.
  • a viscous flow membrane would have very desirable selectivity since flow is driven by the absolute pressure gradient. Gas substantially flows from the high pressure side of the membrane to the low pressure side.
  • the difficulty with gas delivery by a viscous flow mechanism is the degree of uniformity required in the membrane.
  • the discreet pores need to be uniformly distributed over the membrane. Equally important is the pore size distribution. Flow through a pore increases as the fourth power of the radius. Small changes in the pore size can lead to large changes in gas delivery.
  • a flux control layer exhibiting all three flow mechanisms is a desirable means for gas delivery.
  • the three flow mechanisms lead to different methods to regulate the gas flux across the membrane.
  • One method of control is absolute pressure. Increasing the pressure of the system at a fixed differential pressure increases the solution diffusion, Knudsen and viscous contributions to an equivalent extent. As pressure is increased, oxygen flux increases due to the increased driving force. Since there is substantially no reaction occurring on the hydrogen side of the membrane, helping to diminish the influx of oxygen, it is possible to reach flammability limits on the hydrogen side of the reactor. A decrease in oxygen pressure could help to alleviate the problem. Oxygen flux will decrease linearly with the pressure decrease.
  • a 10% decrease in oxygen flux would require the differential pressure to increase by 20 to 40 psi.
  • increasing the differential pressure will simultaneously increase hydrogen flux and decrease the oxygen flux thereby requiring smaller changes in differential pressure.
  • selectivity of the flux control layer can be regulated by differential pressure for a membrane that incorporates all three flow mechanisms.
  • the composition of the gas flux control layer may be any which functions as set forth herein.
  • gas flux control layer for obtaining the described fluxes should be within the skill in the art when combined with the teachings provided herein. It may be either organic, inorganic, or a combination thereof.
  • One composition for the gas flux control layer comprises a composite of polytetrafluoroethylene and carbon. Catalyst may be incorporated predominantly into one side of the composite in order to form the catalyst layer.
  • the gas flux control layer comprises an organic, polymeric material selected from the group consisting essentially of polycarbonates, polyester, polyestercarbonates, polysulfones, polyoiefins, polyphenylene oxides, polyethers, polyimides, polystyrenes, polyetherimides, polyamideimides, and polyethersulfones.
  • a preferable material is tetrabromobisphenol A polycarbonate (TBBA-PC). More preferably, the composition of the gas flux control layer is halogenated.
  • Such materials include sulfonated styrene grafts on a polytetrafluoroethylene backbone (commercially available from RAI Research Corporation as RAIPORETM membranes) and crosslinked sulfonated copolymers of vinyl compounds (commercially available from Ionics, inc., as TYPE CRTM membranes).
  • the membrane further comprise a macroporous support.
  • the macroporous support may be positioned anywhere within the membrane as long as it provides sufficient mechanical strength to withstand any differential pressure across the membrane.
  • the macroporous support layer may be omitted and another layer in the membrane, such as the erosion control layer (described hereinbelow), may be constructed of sufficient mechanical strength as to additionally serve the same purpose as the macroporous support layer.
  • the erosion control layer described hereinbelow
  • it is positioned substantially between the porous hydrophobic catalyst layer and the gas flux control layer.
  • macroporous it is meant that the support is of a pore size sufficient enough to provide negligible resistance to gas flow compared to the flux reduction layer.
  • porous substrates/supports are carbon paper (for example Toray TGPH-120TM) and supports for reverse osmosis membranes such as disclosed in U. S. Patent 4,277,344, assigned to FilmTec Corporation.
  • the support may desirably be rendered hydrophobic by incorporating a hydrophobic material such as poly[1-trimethylsilyl-1 -propyne] ("PTMSP”) into the porous support to enhance overall hydrogen flux, provide a surface with enhanced capability to impede the transportation of undesirable fluid components through the composite structure, or to minimize the effect of pinhole leaks in the membrane.
  • a hydrophobic material such as poly[1-trimethylsilyl-1 -propyne] (“PTMSP)
  • the porous supporting layer is characterized in that it does not greatly impede the transport of molecular hydrogen when the hydrogen is placed in contact with the macroporous supporting layer.
  • the selectivity of the support layer doesn't matter and is typically very low.
  • the macroporous support is a porous polymer membrane.
  • polymeric supporting layers are cellulose ester and porous polysulfone membranes.
  • Such membranes are commercially available under the trade names MILLIPORETM, PELLICONTM and DIAFLOWTM. Where such supporting membranes are thin or highly deformable, a frame may also be necessary to adequately support the semi-permeable membrane.
  • One preferred embodiment is to utilize a support having a "dual porosity" structure.
  • “dual porosity” it is meant that the support structure has a “coarse” pore layer facing the hydrogen contact side of the membrane, and a “fine” pore layer facing the oxygen contact side of the membrane.
  • the “coarse” pores (for example radius of 10-30 micrometers) are larger than the “fine” pores (for example radius of 0.8-1.0 micrometers), which means that the capillary pressure of any liquid (for example water or product on the oxygen contact side of the membrane) is larger in the fine pore layer than it is in the coarse pore layer.
  • Liquid penetrates the fine pore layer, and would continue to penetrate the coarse pore layer, interface control is achieved by increasing the pressure of the gas to a point between the capillary pressure of the liquid in each pore size region.
  • the gas pressure is greater than the capillary pressure in the coarse pore layer, and forces the liquid back. Since it is less than the capillary pressure in the fine pore layer, liquid is further inhibited from intrusion towards the hydrogen contact side of the membrane.
  • a method for utilization of a dual porosity mechanism has been disclosed and patented by The Dow Chemical Company. See U.S. Pat. No.'s 4,341 ,606 and 4,260,469, incorporated herein by reference. Such a structure may be fabricated in many different ways, but one typical method would be to form a composite of two layers, one layer having the coarse pores and the other layer having the fine pores.
  • a preferred embodiment of this invention is for the membrane to further comprise a catalyst erosion control layer.
  • the catalyst erosion control layer is preferably located on the surface of the porous hydrophobic catalyst layer, more preferably, the oxygen contact side of the porous hydrophobic catalyst layer.
  • the function of the catalyst erosion control layer is to inhibit the erosion of catalyst out of the porous hydrophobic catalyst layer. Typically, this occurs by the catalyst being carried away by either water and/or hydrogen peroxide synthesis products which are formed and removed from the oxygen contact side of the membrane.
  • the catalyst erosion control layer may comprise any material useful for performing this function.
  • One embodiment comprises porous carbon paper.
  • a preferred embodiment comprises ion exchange resin, as described previously for incorporation into the porous hydrophobic layer itself.
  • the ion exchange resin for example NAFION
  • the ion exchange resin will capture soluble catalyst and allow: (1) reaction back to the insoluble form by an added reactant (oxidant or reductant), and/or (2) regeneration of the insoluble catalyst in a separate step. Therefore, the ion exchange material inhibits catalyst loss without removing spent catalyst from the system nor introducing materials that may cause product decomposition.
  • a catalyst erosion control layer which comprises both porous carbon paper and ion exchange resin. As described previously with regards to the "macroporous support", it may also be advantageous to fabricate the catalyst erosion control layer such that it has sufficient mechanical strength to withstand differential pressure across the membrane.
  • membrane preparation techniques which are already known to those of skill in the art (see citations set forth herein above), fabrication of the membranes of this invention may be accomplished.
  • the membranes of this invention may further be subjected to treatments with heat or by stretching in order to modify properties of the membranes.
  • the membranes may be subjected to other treatments known to one of skill in the art such as solvent annealing, etching, irradiating, cross-linking, fluorinating, sulfonating, plasma treating, and the like.
  • the membrane is heat annealed before use. The membrane is exposed to temperatures above the beta transition and below the glass transition temperature of the membrane for a period of time to partially density the polymer.
  • the membrane may be utilized in many different structural forms.
  • One embodiment of this invention is to use a hollow fiber form of the membrane, however, typically the membrane is in the form of a substantially flat sheet. Since the membrane may be relatively thin or highly deformable, it may be desirable to provide added support to the membrane. There are well known ways to produce membranes to do this.
  • the peripheral area of the membrane is affixed to a framing structure which supports the outer edge of the membrane.
  • the membrane can be affixed to the framing structure by a clamping mechanism, adhesive, chemical bonding, or other techniques known by one of skill in the art.
  • the membrane affixed to the frame can then be sealingly engaged in the conventional manner in a vessel so that the membrane surface inside the framing support separates two otherwise non-communicating compartments in the vessel.
  • the skilled artisan will recognize that the structure which supports the membrane can be an integral part of the vessel or even the outer edge of the membrane.
  • a chemical reactor which incorporates the membrane of this invention.
  • Such a chemical reactor typically comprises: the membrane, as set forth herein; a means for supplying hydrogen gas to the hydrogen contact side of the membrane; a means for supplying oxygen gas to the oxygen contact side of the membrane; and a means for removing product from the oxygen contact side of the membrane.
  • the hydrogen contact side of the membrane is positioned such that it faces, and operatively connects to, a hydrogen supply chamber.
  • the oxygen contact side of the membrane is positioned such that it faces, and operatively connects to, an oxygen supply chamber.
  • Operatively connects means that each chamber is positioned with respect to the membrane such that a relevant composition (for example, hydrogen or oxygen) can be placed in contact with its respective contact side of the membrane.
  • a hydrogen supply chamber provides an effective environment for introducing, containing, and placing hydrogen, or a hydrogen containing mixture, in contact with the hydrogen contact side of the membrane.
  • the oxygen supply chamber provides an effective environment for introducing, containing, and placing oxygen, or an oxygen containing mixture, in contact with the oxygen contact side of the membrane.
  • each chamber desirably has at least one opening for supply and/or removal of relevant composition(s), reaction products, or both.
  • a "Serpentine" channel arrangement wherein the hydrogen and/or oxygen chambers on respective sides of the membrane consist of a series of connected parallel channels with alternating flow directions. With such a serpentine channel, it is preferred that the channels on one side of the membrane are aligned in parallel with respective channels on the other side of the membrane.
  • more than one opening per chamber may also be provided wherein one opening is an inlet for introducing a relevant composition into its respective chamber and one opening is an outlet for removing reaction products and/or unreacted relevant compositions.
  • Another aspect of this invention is a method of using the membrane of this invention for synthesis of hydrogen peroxide.
  • the method comprises placing hydrogen in contact with the hydrogen contact side of the membrane, placing oxygen in contact with the oxygen contact side of the membrane, and contacting the hydrogen and oxygen at an interface in the hydrophobic catalyst layer.
  • Conditions, such as temperature and pressure should also be provided which are sufficient to react the hydrogen and oxygen to form the hydrogen peroxide.
  • the hydrogen When the hydrogen is contacted with the hydrogen contact side, the hydrogen is transported through at least the flux control layer to the porous hydrophobic catalyst layer.
  • the oxygen is provided at the oxygen contact side of the membrane, it is transported to the porous hydrophobic catalyst layer and is placed in contact with the hydrogen at the catalyst layer.
  • the hydrogen then reacts with the oxygen to form a reaction product comprising hydrogen peroxide.
  • the oxygen contact side comprises an oxygen reducing catalyst (for example palladium).
  • the oxygen reducing catalyst at the oxygen contact side is chosen to enhance the rate of the reaction between hydrogen and oxygen, and to provide high selectivity to produce hydrogen peroxide rather than water.
  • the oxygen is preferably provided to the oxygen contact side of the membrane as a stream of pure oxygen gas
  • a typical method of introducing oxygen to the oxygen contact side is as a component in a mixture such as air. It is also preferable for the oxygen to be introduced in a mixture with water.
  • the water helps dilute the hydrogen peroxide product, thereby reducing its potential decomposition. The water may also assist in the removal of the heat of reaction. It is desirable that, when the oxygen is introduced in a mixture with water, the concentration of oxygen is high enough such that at least bubbles, or even pockets, of oxygen are present in the water (in contrast to substantially all of the oxygen being dissolved in the water). Hydrogen peroxide stabilizers may also be included in the oxygen feed stream.
  • Typical hydrogen peroxide stabilizers include amino-tri(methylene phosphonic acid), 1-hydroxyethyiidene-1 ,1-diphosphonic acid, ethylene diamine tetra(methylene phosphonic acid), pyrophosphoric acid, salts thereof, and combinations thereof. It is most preferred to further include additives to the membrane which are optimized for increasing hydrogen peroxide selectivity. Such additives may be provided to the membrane in any number of ways depending upon the membrane reactor design utilized. For example, such additives may be doped into the porous hydrophobic catalyst layer using a pretreatment process, or they may be supplied by means of one or both of the oxygen- or hydrogen-containing feed streams.
  • Such additives may include H 2 SO 4 , HCN, HNO 3 , H 3 PO 4 , HCI, HBr, HI, (COOH) 2 , CH 3 COOH, HCOOH, salts thereof, and combinations thereof.
  • Many such additives are known in the art for increasing selectivity to hydrogen peroxide. See T.Z. Pospelova et al., "Palladium-Catalysed
  • This method of chemical synthesis may, if desired, be conducted at an elevated temperature.
  • the temperature should not exceed a temperature at which any one of the materials of the chemical reactor (for example the membrane), or product (for example hydrogen peroxide) significantly decompose or degrade.
  • This temperature, and the significance of chemical reactor degradation vary according to the specific composition of the membrane.
  • the temperature is maintained at less than 75° C, however, one of skill in the art is capable of selecting an appropriate temperature as other conditions in a chemical reactor may be varied.
  • the method of the invention is typically conducted at a pressure of from ambient
  • a pressure differential between each side of the composite membrane does not exceed 700 kPa (100 psi) to avoid damage to the membrane.
  • Robust membranes may allow the use of higher differential pressures from increased hydrogen pressures. Elevated hydrogen pressures can enhance the flux of hydrogen relative to that of oxygen. Generally, increased pressure provides an increased mass transfer rate of the reactants.
  • a particularly preferred pressure is from 750 kPa (109 psi) to 6,800 kPa (986 psi). It is typically preferable that the pressure of hydrogen on the hydrogen contact side of the membrane is greater than that of the oxygen on the oxygen contact side of the membrane.
  • it is also important to also maintain a flux of hydrogen from the hydrogen contact side which results in a concentration of hydrogen in the oxygen supply chamber which is outside of the flammability range.
  • reaction product removal is for the product to be swept up at the surface of the oxygen contact side of the membrane into a continually flowing oxygen feed stream containing liquid water.
  • the carbon paper was purchased from E-TEK, Inc., Natick, MA. Specifically, Toray TGPH-120TM, from E-TEK was utilized. Toray TGPH-120TM is a porous carbon paper having a nominal thickness of 12-14 mils and density of approximately 0.55 grams/cm 3 . The gas permeability of the Toray carbon paper is approximately 54,000 X 10-4 cc / cm 2 x sec. x cm. Hg.
  • TeflonTM-coated TorayTM paper also set forth in the examples below are references to TeflonTM-coated TorayTM paper. Unless stated otherwise, this is intended to mean a Toray TGPH-120TM carbon paper which has been coated with a dispersion of (poly)tetrafluoroethylene (PTFE), specifically DuPont's TeflonT- 30TM.
  • PTFE polytetrafluoroethylene
  • the TeflonTM-coated paper is dried in an oven under vacuum at approximately 325°C to melt the PTFE and disperse it over the whole surface of the carbon paper.
  • the resulting treated carbon paper is hydrophobic (as demonstrated by water repulsion).
  • the paper remains porous, but now has a density of approximately 1.1 grams/cm 3 .
  • the gas permeability of the TeflonTM-coated Toray carbon paper is approximately 38,000 X 10 "4 cc / cm 2 x sec. x cm. Hg.
  • the coated carbon paper has a volume of dispersion containing the equivalent of approximately 10-18 mg of PTFE per centimeter squared (cm 2 ) of carbon paper.
  • Catalyst was prepared by mixing 1.25 gram (g) of 20 weight percent (wt%) Pd on carbon (obtained from E-TEK, Inc.) with 5g glycerol, 1.25 g water, and 8.3 g of a 5 wt% solution of NAFIONTM in an alcohol/water solution (obtained from Aldrich Chemical, Milwaukee, Wl) to obtain a catalyst paint.
  • the catalyst paint was applied to TeflonTM-coated carbon paper using an artist's brush. Only a thin coating was applied each time. It was then dried in the oven under vacuum at 135°C, cooled to room temperature (25°C), and the painting continued until all the paint was transferred onto the carbon paper to obtain a carbon paper composite with the required Pd loading.
  • the composite was then dried at 135°C for 45 minutes under vacuum.
  • the carbon paper/catalyst composite was then heat pressed at 2.25 MPa, and a plate temperature of 140°C to form a carbon paper composite having an approximate size of 36 x 11 cm.
  • a TBBA-PC (tetrabromobisphenol A polycarbonate) asymmetric membrane was prepared by forming an 32 wt% solution of TBBA-PC in N-methylpyrrolidone at 58°C. The solution was degassed in a vacuum oven and was cast on a PYREXTM glass plate heated to 75°C. The resulting cast film and the plate was immediately immersed in water having a temperature between 10°C to 25°C and left in the water for between 1 to 2 hours. The resulting asymmetric membrane was air dried and then dried in vacuum at 60°C. The thickness of the membrane was 0.2 mm and the membrane had one side that was comparatively more dense than its opposite side which was comparatively more microporous.
  • Permeation rates of hydrogen and oxygen through the membrane were measured using standard techniques, as described and referenced in J. Comyn, Editor, “Polymer Permeability", Elsevier Applied Science Publishers, London/New York, 1985, ISBN 0- 85334-322-5.
  • the hydrogen flux through the membrane ranged from 1x10 '5 to IxlO *6 (standard cc)/(cm 2 -sec). This hydrogen flux was as high as 15 times greater than the oxygen flux through the membrane.
  • a TBBA-PC asymmetric membrane prepared as described in Example 1 (b)
  • a carbon paper/catalyst composite prepared as described in Example 1 (a)
  • Pd catalyst loading 0.6 mg/cm 2
  • the reactor consisted of metal plates having milled flow channels arranged in a "serpentine" pattern, the flow channels being used to supply hydrogen to one side of the membrane, and oxygen and water to the other side of the membrane.
  • the area of membrane exposed to the serpentine channels on each face of the membrane was 15 in 2 (100 cm 2 ).
  • the dense side (as opposed to the microporous, hydrogen contact, side) of the asymmetric TBBA-PC film was placed against the exposed carbon paper side of the carbon paper/catalyst composite.
  • the catalyst side of the composite thus faced the oxygen/water flow channel.
  • the aqueous "water” solution also contained hydrogen peroxide selectivity increasing additives of 0.01 M H 2 SO 4 and 0.008M HBr. This aqueous solution was added to the oxygen feed stream at a rate of 0.25 ml_/min., while the molecular oxygen was added at a rate of 0.5 L/min.
  • the H 2 diffusion through the membrane ranged from 7 to 30 standard cc /min for the 15 in 2 (100 cm 2 ) of area exposed to the gas supply channels. Analysis of the exiting gas on the oxygen side showed that 80% of the hydrogen diffusing through the membrane completely reacted to form water or hydrogen peroxide.
  • Methylene chloride (MeCI), HPLC-GC/MS grade, was obtained from Fisher Scientific (Pittsburgh, Ca).
  • TBBA-PC was obtained from The Dow Chemical Company (Midland, Ml). Methylene chloride and the 1 ,2 dimethylcyclohexane were mixed to a ratio of 2.06 :1 w/w methylene chloride to dimethylcyclohexane. To make the casting solution, 14.8 wt% TBBA-PC was added to the MeCi/DMC solution.
  • a phosphoric acid fuel cell electrode (FCE) on TeflonTM-coated carbon paper was purchased from E-TEK Inc. ("Gas Diffusion Electrodes and Catalyst Materials", 1995 Catalogue , E-TEK inc. Natick, MA). Using 80 grit sandpaper, the non-catalytic side of the electrode was roughened. The electrode was placed in a fume hood with the catalyst side down. The surface of the electrode was saturated with methylene chloride to fill the pores of the macroporous carbon paper. Immediately after the surface liquid disappeared (evaporated), the casting solution was poured onto one end of the FCE. A 38 mil doctor blade was drawn down the length of the FCE uniformly covering the FCE with the casting solution. The solvents were allowed to evaporate leaving the gas flux control layer.
  • a fuel cell electrode utilizing a catalyst containing 1.2 wt% copper/20 wt% palladium was purchased from E-TEK, Inc.
  • the metal loading of the membrane was 1.5 mg/cm 2 .
  • a TBBA-PC gas flux control layer was applied to the electrode to form the membrane using the method of Example 3.
  • the membrane was loaded into the reactor. Pressure in the hydrogen chamber of the reactor was increased to 250 psi with hydrogen.
  • the membrane was conditioned with hydrogen at 250 psi. Nitrogen was substituted for hydrogen and the reactor returned to 100 psi.
  • the reactor was brought to operating conditions at 200 psi of H 2 in the hydrogen supply chamber and 190 psi in the oxygen supply chamber. A 10 psi differential pressure existed across the membrane.
  • a phosphoric acid fuel cell electrode comprised of 20wt% palladium on Vulcan XC carbon with 0.5 mg/cm 2 total metal loading was purchased from E-TEK Inc. The electrode was subsequently treated with a formalin solution to deposit copper onto the catalyst. A TBBA-PC gas flux control layer was applied to the electrode using the method of Example 3. The resulting membrane was placed in a serpentine channel reactor. Hydrogen pressure was increased to 250 psi to condition the catalyst.
  • Hydrogen was fed to the reactor on the a 0.43 SLPM.
  • Oxygen was fed to the oxygen contact side of the membrane at 0.65 SLPM.
  • Hydrogen pressure was controlled at 100 psi.
  • a 20 psi differential was maintained across the membrane.
  • Temperature was maintained at 7 °C.
  • a promoter solution containing 0.01 M H 2 SO 4 and 0.001 M HBr was fed with the oxygen stream at a rate of 4 ml/minute. Under these conditions, the productivity of the reaction was 0.15 lb/ft hr and the hydrogen peroxide concentration of the product was 50 ppm.
  • Hydrogen pressure was increased to 310 psi. Differential pressure was increased to 25 psi. Hydrogen was fed to the reactor on the a 0.52 SLPM. Oxygen was fed to the catalyst side of the membrane at 0.69 SLPM. Promoter flow rate was decreased to 0.5ml/minute. Temperature increased to 13 °C. Productivity increased to 0.36 lb/ft hr. The hydrogen peroxide concentration increased to 0.28wt%.
  • a phosphoric acid fuel cell electrode comprised of 20wt% palladium on Vulcan XC carbon with 0.5mg/cm 2 total metal loading was purchased from E-TEK Inc. The electrode was subsequently treated with a formalin solution to deposit copper onto the catalyst. A TBBA-PC gas flux control layer was applied to the electrode using the method of Example 3. The resulting membrane was placed in a serpentine channel reactor. Hydrogen pressure was increased to 250 psi to condition the catalyst. Nitrogen was substituted for hydrogen and the reactor returned to 100 psi.
  • Hydrogen was fed to the reactor on the a 0.39 SLPM.
  • Oxygen was fed to the oxygen contact side of the membrane at 0.28 SLPM.
  • Hydrogen pressure was controlled at 100 psi.
  • Hydrogen pressure was increased to 150 psi. All other conditions were held constant. Productivity increased to 0.14 lb/ft 2 hr. The hydrogen peroxide concentration was essentially unchanged (0.22 wt%).
  • a phosphoric acid fuel cell electrode comprised of 20 wt% palladium on Vulcan XC carbon with 0.5mg/cm 2 total metal loading was purchased from E-TEK Inc. Using a paint brush, a solution comprised of 100 ul 48wt% HBr, 450 ul of 98wt% H 2 SO 4 , and 40ml methanol was painted on both sides of the phosphoric acid fuel cell electrode. The methanol wet the TeflonTM-coated carbon paper and the catalyst layer carrying the promoter inside of the electrode. The methanol was allowed to evaporate leaving the promoter within the membrane. This doping procedure was repeated. A TBBA-PC gas flux control layer was applied to the electrode using the method of Example 3. The resulting membrane was placed in a serpentine channel reactor. Hydrogen pressure was increased to 250 psi to condition the catalyst. Nitrogen was substituted for hydrogen and the reactor returned to 100 psi.
  • Hydrogen was fed to the reactor at 0.5 SLPM.
  • Oxygen was fed to the catalyst side of the membrane at 0.34 SLPM.
  • Hydrogen pressure was controlled at 100 psi.
  • a 10 psi differential was maintained across the membrane.
  • a promoter solution containing 0.05 M H 2 SO 4 and 0.01 M HBr was fed with the oxygen stream at a rate of 1 ml/minute. Under these conditions, the productivity of the reaction was 0.2 lb/ft 2 hr and the hydrogen peroxide concentration of the product was 0.47wt%.
  • a phosphoric acid fuel cell electrode comprised of 20wt% palladium on Vulcan XC carbon with 0.5mg/cm 2 total metal loading was purchased from E-TEK Inc. (Natick, Ma.). The electrode was subsequently treated with a formalin solution to deposit copper onto the catalyst. Using a paint brush, a solution comprised of 100 ul 48wt% HBr an 450 ul of H 2 SO 4 and 40ml methanol was painted on both sides of the phosphoric acid fuel cell electrode. The methanol wet the TefionTM-coated carbon paper and the catalyst layer carrying the promoter inside of the electrode. The methanol was allowed to evaporate leaving the promoter within the membrane. A single doping procedure was used.
  • a TBBA-PC gas flux control layer was applied to the electrode using the method of Example 3.
  • the resulting membrane was placed in a serpentine channel reactor. Hydrogen pressure was increased to 250 psi to condition the catalyst. Nitrogen was substituted for hydrogen and the reactor returned to 100 psi. Promoter concentration was 0.04 M H 2 SO 4 and 0.004 M HBr. The following data were collected:
  • a phosphoric acid fuel cell electrode comprised of 10 wt% palladium and 1.2 wt%Copper on Sibunit carbon with 0.5mg/cm 2 total metal loading was purchased from E-TEK Inc. Using a paint brush, a solution comprised of 100 ul 48wt% HBr, 450 ul of 98wt% H 2 SO 4 , and 40ml methanol was painted on both sides of the phosphoric acid fuel cell electrode. The methanol wet the TeflonTM- coated carbon paper and the catalyst layer carrying the promoter inside of the electrode. The methanol was allowed to evaporate leaving the promoter within the membrane. A single doping procedure was used. A TBBA-PC gas flux control layer was applied to the electrode using the method of Example 3. The resulting membrane was placed in a serpentine channel reactor. Hydrogen pressure was increased to 250 psi to condition the catalyst. Nitrogen was substituted for hydrogen and the reactor returned to 100 psi.
  • Hydrogen was fed to the reactor at 0.85 SLPM.
  • Oxygen was fed to the catalyst side of the membrane at 0.50 SLPM.
  • a 70 wt% hydrogen/30 wt% nitrogen feed was introduced to the hydrogen supply chamber and the pressure controlled at 400 psi.
  • a 10 psi differential was maintained across the membrane.
  • a promoter solution containing 0.05 M H 2 SO 4 and 0.01 M HBr was fed with the oxygen stream at a rate of 0.3 ml/minute. Under these conditions, the productivity of the reaction was 0.27 lb/ft 2 hr and the hydrogen peroxide concentration of the product was 5.0 wt%.
  • a phosphoric acid fuel cell electrode comprised of 20 wt% palladium and 1.2 wt% copper on Vulcan XC carbon with 0.5mg/cm 2 total metal loading was purchased from E-TEK Inc. Using a paint brush, a solution comprised of 100 ul 48wt% HBr, 450 ul of 98wt% H 2 SO 4 , and 40ml methanol was painted on both sides of the phosphoric acid fuel cell electrode. The methanol wet the TeflonTM- coated carbon paper and the catalyst layer carrying the promoter inside of the electrode. The methanol was allowed to evaporate leaving the promoter within the membrane. A single doping procedure was used. A TBBA-PC gas flux control layer was applied to the electrode using the method of Example 3. The resulting membrane was placed in a serpentine channel reactor.
  • Hydrogen pressure was increased to 250 psi to condition the catalyst. Nitrogen was substituted for hydrogen and the reactor returned to 100 psi.
  • Hydrogen was fed to the reactor at 0.85 SLPM.
  • Oxygen was fed to the oxygen contact side of the membrane at 0.50 SLPM.
  • Hydrogen pressure was controlled at 400 psi.
  • a 65 psi differential was maintained across the membrane.
  • a promoter solution containing 0.05 M H 2 SO 4 and 0.01 M HBr was fed with the oxygen stream at a rate of 0.2 ml/minute. Under these conditions, the productivity of the reaction was 0.21 lb/ft 2 hr and the hydrogen peroxide concentration of the product was 1.5 wt%.
  • a phosphoric acid fuel cell electrode comprised of 20 wt% palladium and 1.2 wt% copper on
  • Vulcan XC carbon with 1.0 mg/cm 2 total metal loading was purchased from E-TEK Inc. Using a paint brush, a solution comprised of 100 ul 48 wt% HBr, 450 ul of 98wt% H 2 SO 4 , and 40ml methanol was painted on both sides of the phosphoric acid fuel cell electrode. The methanol wet the TeflonTM- coated carbon paper and the catalyst layer carrying the promoter inside of the electrode. The methanol was allowed to evaporate leaving the promoter within the membrane. A single doping procedure was used. A TBBA-PC gas flux control layer was applied to the electrode using the method of Example 3. The resulting membrane was placed in a serpentine channel reactor.
  • Hydrogen pressure was increased to 250 psi to condition the catalyst. Nitrogen was substituted for hydrogen and the reactor returned to 100 psi. Hydrogen was fed to the reactor at 1.0 SLPM. Oxygen was fed to the catalyst side of the membrane at 0.60 SLPM. Hydrogen pressure was controlled at 310 psi. A 30 psi differential was maintained across the membrane. A promoter solution containing 0.05 M H 2 SO 4 and 0.01 M HBr was fed with the oxygen stream at a rate of 0.1 ml/minute. Under these conditions, the productivity of the reaction was 0.82 lb/ft 2 hr and the hydrogen peroxide concentration of the product was 1.6 wt %.
  • Teflon 30B is a negatively charged, hydrophobic colloid, containing approximately 60% [by total weight] of 0.05 to 0.5 mm PTFE resin particles suspended in water.
  • the TeflonTM-coated carbon paper was fully immersed in a bath of the Teflon 30B.
  • the Teflon 30B bath containing the "coated” carbon paper was placed in a vacuum oven, and 29.5 in of vacuum applied. At intervals, the vacuum was released, whereupon the bubbles resulting from the vacuum treatment would collapse.
  • the carbon paper was then removed from the Teflon 30B bath. This treated carbon paper was then dried in an oven at 90 to 120°C for approximately 30 minutes. The treated carbon paper was then subject to a devolatiization heating step at 288°C for 30 minutes. The final step was a sintering step where the treated carbon paper was heated at 378° C for 30 minutes. The entire process of immersion in a Teflon 30B vacuum bath, drying, devolatiiization, and sintering was repeated twice, but could have been repeated more times if desired. At the conclusion of this treatment, the modified carbon paper was 15.0 mils thick, and weighed 57.0 mg./cm .
  • the gas permeability of the modified paper was approximately 0.7 X 10 "4 cc / cm 2 x sec. x cm. Hg.
  • this resulting TeflonTM modification of the TeflonTM-coated carbon paper shall be referred to as the "TeflonTM-modified carbon paper" (as opposed to the “TeflonTM-coated carbon paper”).
  • the TeflonTM-modified carbon paper and catalyst (20 wt% palladium, 1.2 wt% copper on Vulcan XC-72) was supplied to E-TEK, Inc.
  • a membrane was prepared by incorporating the catalyst onto one side of the TefionTM-modified carbon paper such that the TeflonTM and carbon paper could serve as the gas flux control layer and the catalyst was on the oxygen contact side of the TeflonTM- modified carbon paper membrane.
  • the membrane had a total metal loading of 0.6mg/cm 2 .
  • a solution comprised of 100 ul 48wt% HBr, 450 ul of 98wt% H 2 SO 4 , and 40ml methanol was painted on the oxygen contact side of the membrane.
  • the methanol wet the TeflonTM-modified carbon paper and the catalyst layer carrying the promoter inside of the membrane.
  • the methanol was allowed to evaporate leaving the promoter within the membrane.
  • the resulting membrane was placed in a serpentine channel reactor. Hydrogen pressure was increased to 250 psi to condition the catalyst. Nitrogen was substituted for hydrogen and the reactor returned to 100 psi.
  • Hydrogen was fed to the reactor at 0.39 SLPM.
  • Oxygen was fed to the oxygen contact side of the membrane at 0.27 SLPM.
  • Hydrogen pressure was controlled at 250 psi.
  • a 5 psi differential was maintained across the membrane.
  • a promoter solution containing 0.05 M H 2 SO 4 and 0.01 M HBr was fed with the oxygen stream at a rate of 0.2 ml/minute. Under these conditions, the productivity of the reaction was 0.13 lb/ft 2 hr and the hydrogen peroxide concentration of the product was 0.1 wt%.

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  • Organic Chemistry (AREA)
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  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)

Abstract

L'invention concerne une membrane utile pour la synthèse du peroxyde d'hydrogène à partir d'hydrogène et d'oxygène. La membrane, qui comprend une face en contact avec l'hydrogène et une face en contact avec l'oxygène, renferme une couche catalytique hydrophobe poreuse opposée à la face en contact avec l'oxygène et une face de régulation du flux gazeux opposée à la face en contact avec l'hydrogène. La couche de régulation du flux gazeux est placée entre la face en contact avec l'hydrogène et la couche catalytique, de façon que le flux d'hydrogène puisse être amené d'une manière contrôlée à ladite couche catalytique. Cette membrane et ce procédé peuvent être utilisés pour synthétiser de manière contrôlée du peroxyde d'hydrogène directement à partir d'hydrogène et d'oxygène, sans utiliser ni solvants organiques, ni matériel complexe pour le transport ionique et électrique.
PCT/US1998/012156 1997-07-11 1998-06-10 Membrane et procede destines a la synthese du peroxyde d'hydrogene WO1999002264A1 (fr)

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19960660A1 (de) * 1999-12-15 2001-06-28 Bakowsky Udo Biosymphatische Implantat-Materialien, deren Modifizierung, Funktionalisierung und Verwendung
JP2002201010A (ja) * 2000-12-28 2002-07-16 Nok Corp 過酸化水素製造装置
WO2003014014A3 (fr) * 2001-08-02 2003-07-17 Eni Spa Catalyseur et utilisation de celui-ci dans la synthese du peroxyde d'hydrogene
WO2002002846A3 (fr) * 2000-07-05 2003-08-28 Johnson Matthey Plc Cellule electrochimique
US6806390B1 (en) 2000-08-18 2004-10-19 Inuista North America S.àr.l. Hydroperoxide decomposition catalyst
DE102005042920A1 (de) * 2005-09-08 2007-03-15 Dechema Gesellschaft Für Chemische Technik Und Biotechnologie E.V. Inhärent sicheres selektives Verfahren zur direkten Synthese von Wasserstoffperoxid aus Wasserstoff und Sauerstoff mit einer katalytisch beschichteten benetzbaren porösen Membran und eine Vorrichtung zum Durchführen des Verfahrens

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1995030474A1 (fr) * 1994-05-06 1995-11-16 The Dow Chemical Company Membrane composite pour synthese chimique
WO1997013006A1 (fr) * 1995-10-06 1997-04-10 The Dow Chemical Company Membrane composite et son utilisation dans les syntheses chimiques

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1995030474A1 (fr) * 1994-05-06 1995-11-16 The Dow Chemical Company Membrane composite pour synthese chimique
WO1997013006A1 (fr) * 1995-10-06 1997-04-10 The Dow Chemical Company Membrane composite et son utilisation dans les syntheses chimiques

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19960660A1 (de) * 1999-12-15 2001-06-28 Bakowsky Udo Biosymphatische Implantat-Materialien, deren Modifizierung, Funktionalisierung und Verwendung
WO2002002846A3 (fr) * 2000-07-05 2003-08-28 Johnson Matthey Plc Cellule electrochimique
US6806390B1 (en) 2000-08-18 2004-10-19 Inuista North America S.àr.l. Hydroperoxide decomposition catalyst
JP2002201010A (ja) * 2000-12-28 2002-07-16 Nok Corp 過酸化水素製造装置
WO2003014014A3 (fr) * 2001-08-02 2003-07-17 Eni Spa Catalyseur et utilisation de celui-ci dans la synthese du peroxyde d'hydrogene
RU2268858C2 (ru) * 2001-08-02 2006-01-27 Эни С.П.А. Катализатор и его применение для синтеза пероксида водорода
US7101526B2 (en) 2001-08-02 2006-09-05 Eni S.P.A. Catalyst and its use in the synthesis of hydrogen peroxide
DE102005042920A1 (de) * 2005-09-08 2007-03-15 Dechema Gesellschaft Für Chemische Technik Und Biotechnologie E.V. Inhärent sicheres selektives Verfahren zur direkten Synthese von Wasserstoffperoxid aus Wasserstoff und Sauerstoff mit einer katalytisch beschichteten benetzbaren porösen Membran und eine Vorrichtung zum Durchführen des Verfahrens
WO2007028375A1 (fr) * 2005-09-08 2007-03-15 Dechema Gesellschaft Für Chemische Technik Und Biotechnologie E.V. Procede selectif, sur, et inherent pour effectuer la synthese directe de peroxyde d'hydrogene a partir d'oxygene et d'hydrogene comprenant une membrane poreuse, pouvant etre humidifiee, et recouverte de maniere catalytique, et dispositif pour mettre en oeuvre le procede

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