Classifications

• • 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
  • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
  • B01J31/02—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides
  • B01J31/06—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides containing polymers
• • 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
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
  • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
  • B01J23/44—Palladium
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B13/00—Oxygen; Ozone; Oxides or hydroxides in general
  • C01B13/02—Preparation of oxygen
  • C01B13/0229—Purification or separation processes
  • C01B13/0233—Chemical processing only
  • C01B13/0237—Chemical processing only by oxidation
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B5/00—Water
• • 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
  • B01J2231/00—Catalytic reactions performed with catalysts classified in B01J31/00
  • B01J2231/60—Reduction reactions, e.g. hydrogenation
  • B01J2231/64—Reductions in general of organic substrates, e.g. hydride reductions or hydrogenations
• • 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
  • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
  • B01J31/02—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides
  • B01J31/12—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides containing organo-metallic compounds or metal hydrides
  • B01J31/123—Organometallic polymers, e.g. comprising C-Si bonds in the main chain or in subunits grafted to the main chain
  • B01J31/124—Silicones or siloxanes or comprising such units
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B2210/00—Purification or separation of specific gases
  • C01B2210/0043—Impurity removed
  • C01B2210/0053—Hydrogen

Definitions

• This invention pertains generally to a composition of matter suitable for removing hydrogen from gaseous mixtures including hydrogen and oxygen and particularly to a composition suitable for removing hydrogen from gaseous mixtures containing hydrogen and oxygen, wherein the concentration of hydrogen is within the explosive range.
• Hydrogen can be produced from corrosion of metals by atmospheric gases or stray electric currents; from batteries, operating in normal or abnormal condition; and from leaky hydrogen piping.
• the accumulation of hydrogen can present a significant fire hazard, and in the presence of oxygen can represent a potential explosion hazard particularly in sealed components.
• getters hydrogen absorbing materials
• active metals such as zirconium or titanium, and alloys thereof in U.S. Patent No. 4,512,721.
• These metals are capable of maintaining low hydrogen partial pressures but have the disadvantage of requiring high temperatures for initial activation and/or ongoing operation because of the necessity to diffuse surface contaminants into the bulk metal thereby providing a fresh surface for continued hydrogen absorption.
• the presence of oxygen the hydrogen/oxygen mixture can react explosively on contact with these getter materials.
• the present invention provides a composition of matter suitable for safely removing hydrogen from gas mixtures including hydrogen and oxygen, particularly when the concentration of hydrogen is within the explosive range, by the controlled reaction between hydrogen and oxygen, in the presence of a catalyst, to form water.
• a noble metal hydrogenation catalyst preferably Pd dispersed on an inert medium such as carbon
• the polymeric matrix serves two functions: 1) as a permeation restriction to the reactive hydrogen and oxygen gases, slowing the rate of diffusion of these gases to the hydrogenation catalyst, thereby reducing the consequent production of heat; and 2) as a heat sink to immediately absorb the heat of reaction between hydrogen and oxygen and conduct it away from the catalyst in order that the temperature cannot rise to the ignition temperature of the mixture of hydrogen and oxygen.
• the present invention further provides a means for employing the catalyst in a variety of useful 4 forms such as a monolith, a potting agent, and a thermally or UV curable coating or paint that can be applied directly to devices where hydrogen might be generated.
• Figure 2 shows the pressure time curves for two embodiments of a catalyst/polymer matrix material composition.
• the present invention provides a method for safely removing hydrogen from hydrogen oxygen mixtures that can be explosive by recombing the hydrogen and oxygen in the presence of a noble metal hydrogenation catalyst, dispersed in a polymeric matrix, to form water.
• a noble metal hydrogenation catalyst is dispersed in a polymeric matrix that is substantially unreactive to hydrogen and that provides for the diffusion of hydrogen and oxygen to the catalyst but prevents a run-away exothermic reaction between hydrogen and oxygen(i.e., and explosion) by limiting the rate at which the reactants (hydrogen and oxygen) can diffuse to the catalyst surface and thus, the rate of the exothermic hydrogen/oxygen recombination reaction and the rate at which heat is generated.
• the polymeric matrix further provides a heat sink that removes the heat generated by the exothermic hydrogen/oxygen recombination reaction, thus helping to moderate the rate of reaction between hydrogen and oxygen.
• the present invention provides additional benefit for a closed system containing a high concentration of hydrogen and no oxygen that is suddenly exposed to oxygen (air). The invention will not serve as an ignition source in such a scenario because of the moderated reaction rate, as discussed above.
• polymer getter materials such as those described in
• the polymeric material of the present invention does not participate as a reactant but only serves as a matrix to contain the hydrogenation catalyst, as a diffusion restriction, and as a heat sink. This is advantageous in that there are essentially no changes in the physical properties of the polymeric matrix material because of hydrogenation. 5 * -
• a composition suitable for removing hydrogen from a hydrogen oxygen mixture can be prepared by adding between about 1-95 wt%, preferably between l-30wt%, of a hydrogenation catalyst, preferably between 1-10 wt% Pd dispersed on an inert medium, such as carbon or alumina, to a polymeric matrix material selected from the group consisting of silicone-based catalyst dispersions, including 2-part catalyzed addition cure, such as by Pt compounds and other metal-based compounds; 1-part moisture cure, such as commonly release acetic acid, methanol, or oxime water-based acrylic paint dispersions; water-based zinc chromate primer dispersions; a pigment and resin in a vehicle such as water or an organic solvent (ink); and solvent and solventless suspensions of coatings cured by oxygen, heat or UV radiation and combinations thereof.
• the composition can be prepared as a monolith, a thermally or UV curable coating or paint, an adhesive, or a potting agent or in
• EXAMPLE 10 g of a 1 wt% Pd on C catalyst was dispersed into 90 g of an acetoxy-type silicone sealant (1-part moisture cure) by mixing. Hand mixing will yield working formulations, but mechanical mixing is preferred to fully disperse the catalyst. Different mechanical mixers such as blenders, attritors, or kneaders are effective depending on the viscosity of the starting and finished materials. Additional organic solvents or water may be added as processing aids. To be effective the polymeric matrix material and hydrogenation catalyst should be mixed together until essentially no free powder remains. The formulation may be cured and used as a monolith or coated onto a substrate for subsequent curing (thermal cure, moisture cure, UV cure, etc.).
• Table 1 identifies various formulations that were prepared to illustrate this invention.
• the formulations shown in Table 1 were all prepared by mixing the components together to provide a dispersion of the catalyst in the polymeric matrix material.
• a UV curable paint comprising 10.2 g acrylated low molecular weight polybutadiene, 3.5 g 1,1,1 - tri(methacryloxymethyl) ethane, and 0.3 g photoinitiator/accelerator.
• a composition suitable for removing hydrogen from hydrogen oxygen mixture can also be prepared by combining a hydrogenation catalyst with a silicone matrix material, such as a 1-part moisture or 2-part catalyzed addition cure silicone.
• a silicone matrix material such as a 1-part moisture or 2-part catalyzed addition cure silicone.
• the hydrogenation catalyst typically a noble metal dispersed on an inert substrate and preferably 1-10 wt% Pd dispersed on carbon, can be mixed with the silicone matrix material by hand or with the aid of a mechanical mixer. It is preferred that the proportions of hydrogenation catalyst to silicone matrix material be in the weight ratio of about 80:20, however, other proportions have been shown to be useful.
• the silicone matrix material is then cured using procedures known to those skilled in the rubber art. Subsequent to curing of the silicone matrix material, the siliconized hydrogenation catalyst can be further processed by, for example, wet or dry grinding or milling or other methods known to those WO . 914,1 .11 PCT/US98/05449
• the siliconized hydrogenation catalyst can be mechanically mixed with a rubber material selected form the group consisting of styrene/butadiene rubber, silicone- based rubber, styrene/butadiene/acrylonitrile rubber, and polybutadiene rubber. It is desirable that the two materials be intimately mixed. Intimate mixing of the siliconized hydrogenation catalyst and the rubber material can be done by methods known to those skilled in the art such as by grinding or milling. Mixing can be done with the use of a processing aid such as a liquid grinding medium.
• a preferred liquid grinding medium is liquid nitrogen which renders the materials brittle, thereby effectuating size reduction and intimate mixing, and is easily removed from the resulting rubber/siliconized hydrogenation catalyst mixture by evaporation.
• the preferred weight ratio of rubber material to siliconized hydrogenation catalyst can be between 10:90 and 75:25.
• the rubber/siliconized hydrogenation catlyst mixture can be formed into a monolith or dispersed in a liquid medium and the dispersion can then be rolled, brushed or sprayed onto a surface.
• Mixing the hydrogenation catalyst with a silicone matrix material also serves to reduce hydrogenation of any unsaturated bonds that can be present in the rubber material; a process incidental to the operation of the compositions claimed herein.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Inorganic Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Catalysts (AREA)
• Paints Or Removers (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Removal Of Specific Substances (AREA)
• Solid-Sorbent Or Filter-Aiding Compositions (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
• Macromolecular Compounds Obtained By Forming Nitrogen-Containing Linkages In General (AREA)
• Fire-Extinguishing Compositions (AREA)
• Medicines Containing Antibodies Or Antigens For Use As Internal Diagnostic Agents (AREA)

Priority Applications (7)

Applications Claiming Priority (1)

Publications (1)

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Citations (4)

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• 1998
  • 1998-03-19 EP EP98910501A patent/EP1071642B1/en not_active Expired - Lifetime
  • 1998-03-19 CA CA002324588A patent/CA2324588C/en not_active Expired - Fee Related
  • 1998-03-19 JP JP2000536675A patent/JP4563579B2/ja not_active Expired - Fee Related
  • 1998-03-19 AT AT98910501T patent/ATE286494T1/de not_active IP Right Cessation
  • 1998-03-19 DE DE69828533T patent/DE69828533T2/de not_active Expired - Lifetime
  • 1998-03-19 WO PCT/US1998/005449 patent/WO1999047477A1/en not_active Ceased
  • 1998-03-19 AU AU64728/98A patent/AU6472898A/en not_active Abandoned

Patent Citations (4)

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