WO2005066288A1 - Substrates having a nanoporous carbon-containing coating, method for the production thereof and their use - Google Patents

Abstract

Substrates having a nanoporous, carbon-containing coating are produced by applying to the substrate a coating composition, which contains an organic, inorganic or organic/inorganic binding agent and carbon particles as well as optional other solid particles, and by heat treating this composition whereby forming a nanoporous layer. The coated substrates are suited for use as adsorbents and catalysts.

Description

SUBSTRATES WITH A NANOPOROUS CARBONATING COATING, METHOD FOR THE PRODUCTION AND USE THEREOF

The invention relates to substrates provided with a nanoporous carbon-containing coating, a process for their production and their use.

Porous carbon-containing layers are of interest for numerous applications. For example, they can be used as adsorbent layers in a wide variety of geometries. Such layers have the advantage over pellets and other shaped bodies that they are aerodynamically favorable and at the same time have very rapid kinetics, especially if the layers have corresponding geometries with regard to their thickness and their pore structure. Problems arise, however, from the fact that it is very difficult to deposit porous carbon layers on surfaces in a stable form without affecting the porosity. This requires binders that make it possible to bind to a layer without affecting the porosity. Porous carbon-containing systems are known to be good adsorbents, but only if the porosity is sufficiently high.

The object of the present invention was therefore to provide substrates with a carbon-containing coating with a suitable pore structure via a wet-chemical coating process. In this case, binders in particular are to be used which make it possible to carry out a wet-chemical coating and at the same time maintain sufficient porosity after baking or baking.

The invention relates to a substrate with a nanoporous, carbon-containing coating.

The invention further relates to a method for producing such a substrate with a nanoporous, carbon-containing coating, which is characterized in that a coating composition containing a contains organic, inorganic or organic-inorganic binder and carbon particles and optionally other solid particles, applied to the substrate and heat-treated to form a nanoporous layer.

Suitable carbon materials are e.g. Carbon black, graphite, activated carbon, crushed natural coal, fullerenes and mixtures of these carbon materials.

The carbon black used can be any type of carbon black or a mixture of such types. An industrial carbon black is expediently used. The carbon black can be in the form of a powder, in granular form or else as a carbon black preparation, i.e. be used as a liquid, pasty or solid carbon black solvent concentrate. Such soot forms are commercially available. In general, carbon black consists of approximately spherical primary particles of approximately 5 to 500 nm in diameter, which can sometimes grow together to form branched, chain-like aggregates.

Examples of suitable types of carbon black are e.g. Fuma carbon black, channel black, flame black, degussa gas black, thermal black or acetylene black. For activation, the soot can optionally be oxidatively e.g. aftertreated with water vapor, oxygen or air, which increases the hydrophilicity.

Both natural and synthetic graphite, which e.g. can be obtained from pitch or petroleum coke. Activated graphite can also be used. The activated carbons can e.g. can be obtained from petroleum coke, sugar, wood or other carbon-containing materials. As comminuted coals are e.g. ground brown coal, hard coal, anthracite or pitch coal.

In addition to the carbon particles, the coating can also contain other solid particles which have a binder function and / or give the coating a specific (eg catalytic) functionality. These additional solid particles are preferably nanoscale particles. The term “nanoscale” refers to a size below 1 micron. Particles with an average particle diameter (volume average) below 1 μm, preferably not more than 300 nm, more preferably not more than 100 nm and in particular not more than 50, are thus considered to be nanoscale particles In general, the particles are larger than 1 nm, in particular larger than 2 nm and preferably larger than 5 nm.

The term “nanoporous” refers to an average pore size in the range from <1 to 100 nm, preferably <1 to 50 nm. Micro- and mesoporous layers are particularly preferred according to the invention, the term “microporous” corresponding to the IUPAC nomenclature Pore size <2 nm and the term "mesoporous" denotes an average pore size of 2 to 50 nm.

The other solid particles optionally used in addition to the carbon particles are, for example, one- or multi-component oxide particles. Among these, nanoscale SiO ₂ particles (silica) are particularly preferred, which are obtained, for example, by flame pyrolysis, plasma processes, colloid techniques, sol-gel processes, controlled nucleation and growth processes, MOCVD processes and emulsion processes. The nanoscale SiO ₂ particles can also be produced in situ, for example using sol-gel processes. These methods are described in detail in the literature. The SiO ₂ particles are also commercially available, for example as silica sols such as the Levasil ® silica sols from Bayer AG, or pyrogenic silicas, for example the Aerosil products from Degussa. However, the SiO ₂ particles are preferably used in the form of an alkaline or, in particular, acid-stabilized sol (silica sol) which, however, can also contain further components such as functionalized silanes.

Instead of or in addition to the SiO ₂ particles, further solid particles made of any inorganic materials can optionally be added. These are in particular metal compounds, such as oxides or oxide hydrates of Al, B, Ba, Pb, Zn, Cd, Ti, Zr, Ce, Sn, In, La, Fe, Mn, Cu, Co, Ni, Cr, Ta , Nb, V, Mo or W, and corresponding mixed oxides or spinels. examples are the optionally hydrated oxides ZnO, CdO, TiO ₂ , ZrO ₂ (also Y-stabilized), Ce0 ₂ , SnO ₂ , Al ₂ O ₃ , including AIO (OH) (boehmite), ln ₂ O ₃ , La ₂ O ₃ , Y ₂ O ₃ , Fe ₂ O ₃ , Fe _x O _y (intermediates between Fe ₂ O ₃ and Fe ₃ O ₄ ), Cu ₂ O, Ta ₂ O ₅ , Nb ₂ 0 ₅ , V ₂ O, MoO ₃ or WO _3rd It is also possible to use particles provided with noble metal spots on the particle surfaces, which are obtained by impregnating the particles with noble metal salt solutions (halides, nitrates or also complexes) and subsequent annealing.

Other components for such composite binder systems are minerals such as asbestos, talc, mica, and ceramic materials such as boehmite, corundum and mixed systems boehmite / corundum. Such a component can be added in the form of a powder, a sol or a slurry in a suitable suspending agent.

The solid particles can be surface-modified. The surface modification of solid particles is a known method, e.g. is described in WO 93/21127 (DE 4212633) or WO 96/31572, to which reference is hereby made.

All particles or nanoparticles can be crystalline or amorphous; they can have any shape, e.g. spherical, cubic, hexagonal, plate-shaped, needle, whisker or fibrous.

The coating composition used to coat the substrate contains an organic, inorganic or organic-inorganic binder or mixtures thereof. Examples of suitable organic binders are polyacrylic acid, polyacrylic acid esters, polymethacrylic acid, polymethacrylic acid esters, polyacrylamide, polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl acetate, polyvinyl butyral, polyvinyl pyridine, polyallylamine, polyethylene glycol, polypropylene glycol,

Polybutylene glycol or corresponding copolymers and mixtures, fats, fatty acids (e.g. stearic acid), paraffins, waxes, gums (e.g. gum arabic), rubber derivatives (e.g. rubber hydrochloride) or carbohydrates, such as mono-, oligo- and polysaccharides. Examples of the latter are sugar, starches dextrin, cellulose and cellulose derivatives, for example cellulose ethers and cellulose esters such as cellulose acetate, cellulose acetate butyrate and cellulose nitrate.

Examples of inorganic binders are metal oxides, semimetal oxides, minerals, glasses or ceramic materials, as have already been mentioned above.

A particularly preferred organic-inorganic binder contains a hydrolyzate or precondensate of one or more silanes of the formula (I)

RnSiX ₄ . _n (I)

wherein the radicals R are identical or different and represent hydrolytically non-removable groups, the radicals X are identical or different and represent hydrolytically removable groups or hydroxyl groups and n has the value 0, 1, 2 or 3, preferably at least one silane at least one hydrolytically has non-removable group.

In the general formula (I), the hydrolytically removable groups X, which can be identical or different, are, for example, hydrogen, halogen (F, Cl, Br or I, in particular Cl or Br), alkoxy (for example C _1-6 alkoxy, such as methoxy, ethoxy, n-propoxy, i-propoxy and n-, i-, sec.- or tert.-butoxy), aryloxy (preferably C _6- io-aryloxy, such as phenoxy), alkaryloxy, e.g. benzoyloxy, Acyloxy (eg Ci-β-acyloxy, preferably Cι- ₄ -acyloxy, such as acetoxy or propionyloxy) and alkylcarbonyl (eg C _2-7 alkylcarbonyl such as acetyl). Also suitable are NH ₂ , amino mono- or disubstituted with alkyl, aryl and / or aralkyl, examples of the alkyl, aryl and / or aralkyl radicals being those given below for R, amido such as benzamido or aldoxime or ketoxime groups. Two or three groups X can also be connected to one another, for example in the case of Si-polyol complexes with glycol, glycerol or Brenzcatec in. The groups mentioned can optionally contain substituents, such as halogen, hydroxy, alkoxy, amino or epoxy. Preferred hydrolytically removable radicals X are halogen, alkoxy groups and acyloxy groups. Particularly preferred hydrolytically removable radicals are C _2-4 alkoxy groups, especially ethoxy.

The hydrolytically non-cleavable radicals R of the formula (I), which may be the same or different for n greater than 1, are, for example, alkyl (for example C _-2 o-alkyl, in particular C _{4 -4} -alkyl, such as methyl, ethyl, n-propyl , i-Propyl, n-butyl, i-butyl, sec-butyl and tert-butyl), alkenyl (for example C _2-20 alkenyl, in particular C _2- alkenyl, such as vinyl, 1-propenyl, 2- Propenyl and butenyl), alkynyl (for example C ₂ _ ₂₀ -alkynyl, especially C _2-4 -alkynyl, such as ethynyl or propargyl), aryl (especially C ₆ -ιo-aryl, such as phenyl and naphthyl) and corresponding aralkyl and alkaryl groups such as tolyl and benzyl, and cyclic C ₃ -C ₂ alkyl and alkenyl groups such as cyclopropyl, cyclopentyl and cyclohexyl.

The radicals R can have customary substituents, but the radicals preferably do not have any substituents. The substituents can be functional groups via which the condensate can also be crosslinked via the organic groups, if required. Common substituents are e.g. Halogen (e.g. chlorine or fluorine), epoxy (e.g. glycidyl or glycidyloxy), hydroxy, ether, amino, monoalkylamino, dialkylamino, optionally substituted anilino, amide, carboxy, alkenyl, alkynyl, acrylic, acryloxy, methacrylic, methacryloxy, mercapto, cyano, Alkoxy, isocyanato, aldehyde, alkylcarbonyl, acid anhydride and phosphoric acid. These substituents are bonded to the silicon atom via divalent bridging groups, in particular alkylene, alkenylene or arylene bridging groups, which can be interrupted by oxygen or -NH groups. The bridge groups contain e.g. 1 to 18, preferably 1 to 8 and in particular 1 to 6 carbon atoms. The bivalent bridging groups mentioned are derived e.g. from the monovalent alkyl, alkenyl or aryl radicals mentioned above. Of course, the radical R can also have more than one functional group.

Preferred examples of hydrolytically non-releasable radicals R with functional groups via which crosslinking is possible are a glycidyl or a glycidyloxy- (Cι _-20 ) alkylene radical, such as ß-glycidyloxyethyl, γ-glycidyloxypropyl, δ- Glycidyloxybutyl, ε-glycidyloxypentyl, ω-glycidyloxyhexyl, and 2- (3,4-epoxycyclohexyl) ethyl, a (meth) acryloxy (C _1-6 ) alkylene radical, e.g. (meth) acryloxymethyl, (meth) acryloxyethyl, (meth) acryloxypropyl or (meth) acryloxybutyl, and a 3-isocyanatopropyl radical. An example of a fluorine-substituted radical R is 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl. Particularly preferred residues are γ-glycidyloxypropyl and (meth) acryloxypropyl. Here, (meth) acrylic stands for acrylic and methacrylic.

Preferred radicals R are alkyl groups, preferably having 1 to 4 carbon atoms, in particular methyl and ethyl, and phenyl.

Examples of hydrolytically removable silanes of the formula (I) with n = 0 are Si (OCH ₃ ) ₄ , Si (OC ₂ H ₅ ) ₄ , Si (On- or iC ₃ H ₇ ) ₄ , Si (OC ₄ H ₉ ) , SiCI, HSiCI ₃ , Si (OOCCH ₃ ) ₄ . Of these silanes, tetraethoxysilane is particularly preferred.

Examples of silanes of the formula (I) with n greater than 0 are compounds of the following formulas, the alkylsilanes and in particular methyltriethoxysilane being particularly preferred:

CH ₃ -SiCI ₃ , CH ₃ -Si (OC ₂ H ₅ ) ₃ , C ₂ H ₅ -SiCI ₃ , C ₂ H ₅ -Si (OC ₂ H ₅ ) 3, C ₃ H ₇ -Si (OC ₂ H ₅ ) 3, C ₆ H ₅ - Si (OC ₂ H ₅ ) ₃ , (C ₂ H ₅ O) 3-Si-C ₃ H ₆ -CI, (CH ₃ ) ₂ SiCl ₂ , (CH ₃ ) ₂ Si (OC ₂ H ₅ ) 2, (CH ₃ ) ₂ Si (OH) ₂ , (C ₆ H ₅ ) ₂ SiCl ₂ , (C ₆ H ₅ ) ₂ Si (OC ₂ H ₅ ) ₂ , (iC ₃ H ₇ ) ₃ SiOH, CH ₂ = CH-Si (OOCCH ₃ ) ₃ , CH ₂ = CH-SiCI ₃ , CH ₂ = CH-Si (OC ₂ H ₅ ) ₃ , CH ₂ = CHSi (OC ₂ H ₅ ) _3l CH ₂ = CH-Si (OC ₂ H ₄ OCH ₃ ) 3, CH ₂ = CH-CH ₂ -Si (OC ₂ H ₅ ) ₃ , CH ₂ = CH-CH ₂ -Si (OC ₂ H ₅ ) ₃ , CH ₂ = CH-CH ₂ -Si (OOCCH ₃ ) ₃ , CH ₂ = C (CH ₃ ) COO-C ₃ H ₇ -Si (OC ₂ H ₅ ) ₃ , nC ₆ H ₁₃ -CH ₂ -CH ₂ -Si (OC ₂ H ₅ ) ₃ , nC ₈ H ₁₇ -CH ₂ -CH ₂ - Si (OC ₂ H ₅ ) ₃ , (C ₂ H ₅ O) ₃ Si- (CH ₂ ) ₃ -O-CH ₂ -CH -CH ₂ O The silanes can be prepared by known methods; see. W. Noll, "Chemistry and Technology of Silicones", Verlag Chemie GmbH, Weinheim / Bergstrasse (1968).

In a preferred embodiment, the coating composition comprises at least one silane of the formula (I), where n = 0 (SiX-, and at least one silane Formula (I) in which n is greater than 0 and preferably 1. In the coating composition, preferably at least 50 mol%, more preferably at least 60 mol% and in particular at least 70 or 80 mol% of the hydrolyzable compounds used have at least one hydrolytically non-removable group and preferably only one hydrolytically non-removable group. Accordingly, the rest of the hydrolyzable compounds are compounds, in particular silanes, without groups which cannot be hydrolytically split off (for example SiX). In certain cases it may be even more favorable if more than 80 or even more than 90 mol% (for example 100%) of the hydrolyzable compounds are silanes of the formula (I) with n> 1. For the calculation of quantitative ratios, hydrolyzable compounds or silanes are generally understood to be the monomeric compounds. If, as explained below, precondensed compounds (dimers, etc.) are used as starting materials, the corresponding monomers must be converted.

The coating composition preferably comprises hydrolysates or precondensates of methyltriethoxysilane (MTEOS) or of mixtures of MTEOS and tetraethoxysilane (TEOS).

Optionally, hydrolyzable compounds of elements other than Si can be used for the coating composition to produce the hydrolyzate or precondensate. These are in particular compounds of glass- or ceramic-forming elements, in particular compounds of at least one element M from the main groups III to V and / or the subgroups II to IV of the periodic table of the elements. They are preferably hydrolyzable compounds of Al, B, Sn, Ti, Zr, V or Zn, in particular those of Al, Ti or Zr, or mixtures of two or more of these elements. Of course, other hydrolyzable compounds can also be used, in particular those of elements of main groups I and II of the periodic table (for example Na, K, Ca and Mg) and subgroups V to VIII of the periodic table (for example Mn, Cr, Fe and Ni). Hydrolyzable compounds of the lanthanides can also be used. These compounds have in particular the general formula MX _a , where M is the element defined above, X is as defined in formula (I), two groups X can be replaced by an oxo group, and a corresponds to the valence of the element and usually 3 or 4. Alkoxides of Zr and Ti are preferably used.

Examples of usable hydrolyzable compounds of elements M are AI (OCH ₃ ) ₃ , AI (OC ₂ H ₅ ) ₃ , AI (OnC ₃ H ₇ ) ₃ , AI (OiC ₃ H ₇ ) ₃ , AI (OnC ₄ H ₉ ) ₃ , AI (O-sec.-C ₄ H ₉ ) ₃ , AICI ₃ , AICl (OH) ₂ , AI (OC ₂ H ₄ OC ₄ H ₉ ) ₃ , TiCI ₄ , Ti (OC ₂ H ₅ ) ₄ , Ti (OnC ₃ H ₇ ) ₄ , Ti (OiC ₃ H ₇ ) ₄ , Ti (OC ₄ H ₉ ) ₄ , Ti (2-ethylhexoxy) ₄ , ZrCI ₄ , Zr (OC ₂ H ₅ ) ₄ , Zr (OnC ₃ H ₇ ) ₄ , Zr (OiC ₃ H ₇ ) _l Zr (OC ₄ Hg), ZrOCI ₂ , Zr (2-ethylhexoxy), and Zr compounds which have complexing residues, such as, for example, β-diketone and (meth ) acrylic residues, sodium methylate, potassium acetate, boric acid, BCI ₃ , B (OCH ₃ ) ₃ , B (OC ₂ H ₅ ) ₃ , SnCI ₄ , Sn (OCH ₃ ), Sn (OC ₂ H ₅ ) ₄ , VOCI ₃ and VO (OCH ₃ ) ₃ .

The hydrolysates or precondensates of the coating composition are obtained from the hydrolyzable silanes or hydrolyzable compounds by hydrolysis and condensation. Hydrolyzates or precondensates are understood to mean, in particular, hydrolyzed or at least partially condensed compounds of the hydrolyzable starting compounds. Pre-condensed compounds can also be used instead of the hydrolyzable monomer compounds. Such oligomers, which are preferably soluble in the reaction medium, can e.g. straight-chain or cyclic low-molecular partial condensates (e.g. polyorganosiloxanes) with a degree of condensation of e.g. about 2 to 100, especially about 2 to 6.

The hydrolysates or precondensates are preferably obtained by hydrolysis and condensation of the hydrolyzable starting compounds by the sol-gel process. In the sol-gel process, the hydrolyzable compounds are hydrolyzed with water, optionally by heating or acidic or basic catalysis, and, if appropriate, at least partially condensed. There can be stoichiometric amounts of water, but also smaller or larger ones Amounts used. The sol which forms can be adjusted to the viscosity desired for the coating composition by means of suitable parameters, for example degree of condensation, solvent or pH. Further details of the sol-gel process are available, for example, from CJ Brinker, GW Scherer: "Sol-Gel Science - The Physics and Chemistry of Sol-Gel-Processing", Academic Press, Boston, San Diego, New York, Sydney (1990) described.

The hydrolysis and condensation is preferably carried out under sol-gel conditions in the presence of acidic condensation catalysts (e.g. hydrochloric acid, phosphoric acid or formic acid) at a pH of preferably 1 to 2. A viscous sol is generally obtained. The amount of water used for the hydrolysis and condensation of the hydrolyzable compounds, in particular the silanes of the formula (I), is preferably 0.1 to 0.9 and particularly preferably 0.25 to 0.75 mol of water per mol of the hydrolyzable groups present. Particularly good results are often achieved with less than 0.5 mol of water, in particular 0.35 to 0.45 mol of water, per mol of the hydrolyzable groups present.

In a preferred embodiment, the organic-inorganic binder described above additionally contains (preferably nanoscale) solid particles. These are either powder or brine. Suspensions added or formed in situ. These solid particles are preferably SiO ₂ particles, but are, for example, TiO ₂ , ZrO ₂ , GeO ₂ , CeO ₂ , Al ₂ O ₃ , including AIO (OH) (boehmite), corundum and mixed systems boehmite / corundum, ZnO , CdO, SnO ₂ , Ta ₂ O ₅ and mixtures thereof are also suitable.

The coating composition can contain other conventional components. Examples are solvents, surfactants, dyes, flame-retardant additives, anti-corrosion agents, starters and coating aids such as defoamers, surface modifiers, thickeners and leveling agents.

The coating composition typically comprises a solvent for application to a substrate. These are the usual ones on the Solvent used in the field of coating. Examples of suitable solvents are water, alcohols, preferably lower aliphatic alcohols (-CC ₈ alcohols), such as methanol, ethanol, 1-propanol, i-propanol and 1-butanol, ketones, preferably lower dialkyl ketones, such as acetone and methyl isobutyl ketone, Ethers, preferably lower dialkyl ethers, such as diethyl ether, or monoethers of diols, such as ethylene glycol or propylene glycol, with C 1 -C ₈ alcohols, amides, such as dimethylformamide, tetrahydrofuran, dioxane, sulfoxides, sulfones or butyl glycol and mixtures thereof. Water and alcohols are preferably used. High-boiling solvents can also be used, for example polyethers such as triethylene glycol, diethylene glycol diethyl ether and tetraethylene glycol dimethyl ether. If hydrolyzable compounds with alkoxylate groups are used, it is optionally not necessary to use an additional solvent in addition to the alcohol formed during the hydrolysis. In some cases, other solvents are also used, e.g. light paraffins (petroleum ether, alkanes and cycloalkanes), aromatics, heteroaromatics and halogenated hydrocarbons.

The proportion of the carbon particles in the coating composition is usually at least 1% by weight, preferably at least 3% by weight and more preferably at least 8% by weight and generally not more than 30% by weight, preferably not more than 5% by weight. -% and more preferably not more than 12% by weight.

The carbon particles can be admixed as such or predispersed in a solvent.

The usual coating methods can be used to coat the substrate with the coating composition, e.g. Dipping, flooding, knife coating, drawing, spraying, rolling, spinning, spreading, screen printing or electrostatic coating. Flooding or knife coating is particularly preferred according to the invention.

The substrate can be any substrate suitable for the purpose. Examples of suitable substrate materials are metals or metal alloys, such as Steel including stainless steel, chrome, copper, titanium, tin, zinc, brass and aluminum; Glasses such as float glass, borosilicate glass, lead crystal and silica glass; Ceramics, glass ceramics, enamel and heat-resistant plastics. The substrate either consists of such materials or has at least one surface made of such a material. The substrate can have any physical shape, for example tubular or sheet-like. However, spherical and granular substrates can also be coated, for example.

The applied layer is preferably dried before the heat treatment (hardening). Drying can be a simple flashing off at room temperature. Higher drying temperatures are e.g. above 50 ° C and preferably above 80 ° C and at not more than 150 ° C and preferably not more than 120 ° C.

The heat treatment temperatures used depend, among other things, on the type of substrate and the binder system used, and on the heat treatment atmosphere. In the air, the heat treatment can e.g. at a temperature above 150 ° C, preferably above 250 ° C, and up. at 400 to 500 ° C. In an inert gas atmosphere (e.g. nitrogen or argon), depending on the load limit of the substrates, higher temperatures up to 500 to 1000 ° C can be used, e.g. 800 to 1000 ° C for steels.

The duration of the heat treatment depends on the coating and the temperature used. The curing time is usually around 1 hour. The heating rate is often chosen to be 1K / min, starting at room temperature.

The layer thicknesses achieved for the nanoporous carbon-containing coating are usually 0.1 to 500 μm, preferably 0.1 to 100 μm. The desired layer thickness can easily be adjusted via the solids content of the coating composition. The substrates according to the invention with a nanoporous, carbon-containing coating are particularly suitable as adsorbents or / or catalysts. The functionality of the nanoporous, carbon-containing coating can be controlled by using appropriate binder and particle systems and / or changed by subsequent surface modification (eg hydrophilization or coupling of functional groups). In this way, for example, bi- or multifunctional absorber materials can be produced that have a wide adsorption capacity to different systems.

Examples

Example 1 (carbon black / organic binder)

35.7 g of a 30% solution of a polyvinyl alcohol A (Moviol M4-88 from Clariant), 35.7 g of a 12% solution of a polyvinyl alcohol B (Moviol M26-88 from Clariant) and 28.6 g of glycerin mixed and stirred overnight.

2 g of a surfactant (Leunapon F1315 / 7 from Leuna-Tenside GmbH) are dissolved in 100 g of water and 5 g of carbon black (Printex 90 from Degussa) are added. After 15 minutes of treatment with an ultrasound disintegrator, the mixture is stirred overnight. 1 g of the mixed binder obtained above is added and the mixture is stirred for a further 2 hours. The finished suspension is applied to glass or stainless steel by flooding and dried to a crack-free film at room temperature. The layers are air cured for 1 hour at 350 ° C.

Example 2 (graphite / organic binder)

12.8 g of graphite (Timrex KS6) are added to a solution of 1.95 g of a surfactant (Tween 80) in 200 g of water. The suspension is treated with an ultrasound disintegrator for 5 minutes and then stirred overnight. 12.8 g of a 30% solution of a polyvinyl alcohol (Moviol 4-88) in water are added and stir again for 2 hours. The finished suspension is applied to glass or stainless steel by flooding and dried to a crack-free film at room temperature. The layers are air cured for 1 hour at 350 ° C.

Example 3 (carbon black suspension / organic binder)

30 g of a carbon black suspension (AN1-25Λ / L from Degussa) are diluted with 61.6 g water. 8.2 g of the mixed binder from Example 1 and 0.5 ml of octanol are added. The finished suspension is applied to glass or stainless steel by flooding and dried to a crack-free film at room temperature. Curing at 450 ° C for 1 hour in the air produces deep black, crack-free layers. '

Example 4 (alumina / carbon black / organic binder)

a) Approach of the ceramic component

60 g of water are adjusted to pH 3 with concentrated nitric acid. 140 g of corundum (APA-0.5 from Ceralox) are suspended in portions in the water with ultrasound treatment. If necessary, the pH is readjusted with concentrated nitric acid. The suspension is homogenized in an attritor mill for 1 hour, then separated from the grinding balls and, if necessary, corrected again to pH 3. 42.86 g of the suspension are mixed with 8.9 g of a 30% solution of a polyvinyl alcohol A (Moviol M4-88), 22.3 g of a 12% solution of a polyvinyl alcohol B (Moviol M26-88), 2.1 g Glycerin and 23.7 g of water are added.

b) adding the soot suspension

60.1 g of a carbon black suspension (Derussol A from Degussa) are added to 100 g of the aluminum oxide suspension from 4a) and the mixture is stirred overnight. The finished suspension is applied to stainless steel substrates by flooding and dried to a crack-free film at room temperature. The layers are cured at 500 ° C for 3 hours under nitrogen. Example 5 (carbon black / organic-inorganic binder system)

a) Preparation of the binder

A mixture of 1069.9 g (6.0 mol) of methyltriethoxysilane and 312.5 g (1.5 mol) of tetraethoxysilane is divided into two portions (portion 1 and portion 2) of the same weight. 246.8 g of silica sol (Levasil 300/30 from Bayer) are added to portion 1 with stirring. After an emulsion has been formed (approx. 30 s), 5.60 g of 36% by weight HCl are added. After briefly stirring (30-50 s) the reaction mixture becomes clear with heating. Serve with portion 2 in one go. After a short time, the reaction mixture becomes cloudy due to a white precipitate (NaCl). The mixture is then stirred for 15 minutes with cooling in an ice bath. The silane hydrolyzate is left to stand at room temperature for 12 hours and decanted from the sedimented solid. Before use, the sol is adjusted to a degree of hydrolysis of 0.8 by activation with hydrochloric acid (8% by weight, addition of 0.108 g of acid per g of sol).

b) adding the carbon suspension

2.6 g of graphite (Timrex KS6) are dispersed in 40 g of ethanol, mixed with 0.39 g of surfactant (Tween 80) and treated with the ultrasound disintegrator in an ice bath for 30 minutes. 0.52 g of the activated silane hydrolyzate from 5a) are added and the mixture is stirred for 1 hour. The finished suspension is applied to stainless steel substrates by flooding and dried to a crack-free film at room temperature. The layers are cured at 350 ° C for 1 hour.

Example 6 (ground activated carbon / organic binder)

a.) 5 g of surfactant (Tween 80) are dissolved in 40 g of water and 10 g of mortarized activated carbon (Rx3 Extra from Norit) are added. The mixture is ground in a ball mill in a zirconium oxide grinding jar for 2 hours. Then 2 g of the mixed binder from Example 1 are added and the mixture is stirred overnight. The finished suspension is applied to stainless steel substrates by flooding and dried to a crack-free film at room temperature. The layers are cured for 1 hour at 550 ° C under nitrogen. b.) Analogously, the activated carbon can be ground with the surfactant in ethanol. After the grinding process, 3 g of the binder from Example 5a are added and the mixture is stirred for one hour. The finished suspension is applied to stainless steel substrates by flooding and dried to a crack-free film at room temperature. The layers are cured at 350 ° C for 1 hour.

Claims

1. Substrate with a nanoporous, carbon-containing coating.

2. Substrate according to claim 1, characterized in that the carbon is selected from carbon black, graphite, activated carbon, comminuted natural coal, fullerenes and mixtures of these carbon materials.

3. Substrate according to claim 1 or 2, characterized in that the coating additionally contains other solid particles.

4. Substrate according to one of claims 1 to 3, characterized in that the substrate consists of metal, glass, ceramic, glass ceramic or another heat-resistant material or has a surface made of these materials.

5. A method for producing a substrate with a nanoporous, carbon-containing coating, characterized in that a coating composition which contains an organic, inorganic or organic-inorganic binder and carbon particles and optionally other solid particles is applied to the substrate and to form a nanoporous layer heat treated.

6. The method according to claim 5, characterized in that the organic binder for the coating composition is polyacrylic acid, polyacrylic acid ester, polymethacrylic acid, polymethacrylic acid ester, polyacrylamide, polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl acetate, polyvinyl butyral, polyvinyl pyridine, polyallylamine, polyethylene glycol, polypropylene glycol or polybutylene glycol or polybutylene glycol or polybutylene glycol or polybutylene glycol, and mixtures, fats, fatty acids, paraffins, waxes, gums, rubber derivatives or carbohydrates.

7. The method according to claim 5, characterized in that metal oxides, semimetal oxides, minerals, glasses or ceramic materials are used as the inorganic binder for the coating composition.

8. The method according to claim 5, characterized in that a hydrolyzate or precondensate of one or more silanes of the formula RnSiX _{4-n is} used as the organic-inorganic binder for the coating composition, in which the radicals R are identical or different and represent groups which cannot be split off hydrolytically, the radicals X are identical or different and represent hydroxyl groups or hydrolytically removable groups and n has the value 0, 1, 2 or 3, preferably at least one silane having at least one hydrolytically non-removable group.

9. The method according to claim 8, characterized in that the binder additionally contains solid particles.

10. The method according to any one of claims 5 to 9, characterized in that one carries out the heat treatment in air at temperatures of up to 400-500 ° C.

11. The method according to any one of claims 5 to 9, characterized in that one carries out the heat treatment in an inert gas atmosphere at temperatures of up to 500-1000 ° C.

12. Use of the substrate with a nanoporous, carbon-containing coating according to one of claims 1 to 4 as an adsorbent and / or catalyst.