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
  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
  • B01J35/39—Photocatalytic properties
• • 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
• • 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
  • B01J19/26—Nozzle-type reactors, i.e. the distribution of the initial reactants within the reactor is effected by their introduction or injection through nozzles
• • 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
  • B01J2/00—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
  • B01J2/003—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic followed by coating of the granules
• • 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
  • B01J2/00—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
  • B01J2/02—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic by dividing the liquid material into drops, e.g. by spraying, and solidifying the drops
  • B01J2/04—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic by dividing the liquid material into drops, e.g. by spraying, and solidifying the drops in a gaseous medium
• • 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
  • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
  • B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
  • B01J21/08—Silica
• • 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
  • B01J35/20—Catalysts, in general, characterised by their form or physical properties characterised by their non-solid state
  • B01J35/23—Catalysts, in general, characterised by their form or physical properties characterised by their non-solid state in a colloidal state
• • 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
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/34—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation
  • B01J37/349—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation making use of flames, plasmas or lasers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G23/00—Compounds of titanium
  • C01G23/04—Oxides; Hydroxides
  • C01G23/047—Titanium dioxide
  • C01G23/07—Producing by vapour phase processes, e.g. halide oxidation
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
  • C09C1/36—Compounds of titanium
  • C09C1/3607—Titanium dioxide
  • C09C1/3653—Treatment with inorganic compounds
  • C09C1/3661—Coating
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
  • C09C1/36—Compounds of titanium
  • C09C1/3607—Titanium dioxide
  • C09C1/3684—Treatment with organo-silicon compounds
• • 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
  • B01J2219/00121—Controlling the temperature by direct heating or cooling
  • B01J2219/00123—Controlling the temperature by direct heating or cooling adding a temperature modifying medium to the reactants
• • 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
  • B01J2219/00157—Controlling the temperature by means of a burner
• • 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
  • B01J2219/00164—Controlling or regulating processes controlling the flow
  • B01J2219/00166—Controlling or regulating processes controlling the flow controlling the residence time inside the reactor vessel
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2002/00—Crystal-structural characteristics
  • C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
  • C01P2002/85—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70 by XPS, EDX or EDAX data
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/01—Particle morphology depicted by an image
  • C01P2004/04—Particle morphology depicted by an image obtained by TEM, STEM, STM or AFM
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/60—Particles characterised by their size
  • C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
  • C01P2004/82—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases
  • C01P2004/84—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases one phase coated with the other
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
  • C01P2004/82—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases
  • C01P2004/84—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases one phase coated with the other
  • C01P2004/86—Thin layer coatings, i.e. the coating thickness being less than 0.1 time the particle radius
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
  • Y10T428/2982—Particulate matter [e.g., sphere, flake, etc.]
  • Y10T428/2991—Coated
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
  • Y10T428/2982—Particulate matter [e.g., sphere, flake, etc.]
  • Y10T428/2991—Coated
  • Y10T428/2993—Silicic or refractory material containing [e.g., tungsten oxide, glass, cement, etc.]

Definitions

• the present invention relates to a process for the preparation of coated nanoparticles comprising a core containing at least one first material and at least one core at least partially surrounding the core of at least one second material, nanoparticles comprising a non-porous core, the at least one first Contains substance, and at least one at least partially surrounding the core porous shell of at least one second material, wherein the nanoparticles have a narrow particle size distribution, the use of such nanoparticles in photocatalysis and an apparatus for performing the method according to the invention.
• Nanoparticles which have a core of at least one metal oxide and a shell of at least one further metal or semimetal oxide, and processes for their preparation, are already known from the prior art.
• WO 2005/1 13442 A1 discloses a process for producing mixed ternary metal or semimetal oxide powders, comprising mixing vaporizable silicon and titanium compounds and a third vaporizable compound, hydrogen and air, and burning this gaseous mixture in a reaction space, Separating the powder thus obtained from the gaseous reaction products.
• the resulting ternary mixed metal oxide powder can be used in sunscreen formulations.
• WO 2005/1 13442 A1 discloses a process for producing mixed oxide particles in which the individual oxides are present in a mixture throughout the particle, a layer structure is not obtained by the process according to WO 2005/113442 A1.
• US 2006/0093544 A1 discloses a method for producing composite microparticles with a thin coating by reacting a precursor compound of the core material of this microparticle in vaporized or sprayed form to obtain the corresponding core particles. Subsequently, a gaseous precursor is supplied to the coating in parallel with the core particles to form the coating. US 2006/0093544 A1 does not disclose a method for obtaining nanoparticles in a narrow distribution of the particle size or for adjusting the layer thickness of the coating on the particles. Furthermore, the cited document does not disclose a method for obtaining a porous coating on a non-porous core.
• EP 1 138 632 A1 discloses a process for producing doped titanium dioxide, wherein an aerosol containing precursor compounds of the compounds is selected from the group consisting of zinc oxide, platinum oxide, magnesium oxide and / or alumina, the gas mixture of the flame oxidation for the production of titanium dioxide is mixed homogeneously, the aerosol gas mixture is reacted in a flame and the resulting doped oxides produced are separated in a known manner from the gas stream.
• the mixed oxide particles thus obtained have a homogeneous distribution of titanium dioxide and the further oxide in the particle.
• a layer structure comprising a core and at least one shell can not be obtained by the method according to EP 1 138 632 A1.
• JP 2001/286728 discloses a process for producing photocatalysts provided with a layer of a porous ceramic.
• the coating contains pores to maintain the function of the catalyst while avoiding degradation of an organic material in contact with the photocatalyst.
• the method for producing these particles comprises coating photocatalysts with a film of the porous ceramics by hydrophilizing a metal alkoxide as a precursor compound of the ceramics with a polyhydric alcohol, adding water and photocatalyst to this mixture, and spray-drying this mixture to form a powder to obtain, which is finally dried.
• JP2003-001 118 A discloses photocatalytically active nanoparticles consisting of a titanium dioxide core and an incomplete coating of this core of SiO 2 . This document does not disclose nanoparticles that have a specifically adjustable activity over the thickness and porosity of the shell.
• the object of the present invention is to provide a process for producing coated nanoparticles, which makes it possible to obtain core-shell nanoparticles which have a narrow particle size distribution. Furthermore, nanoparticles should be available which have a thin, porous shell whose layer thickness and thus the catalytic activity of the substance present in the non-porous core can be adjusted in a targeted manner.
• a process for producing coated nanoparticles comprising a core of at least one first material and at least one shell at least partially surrounding the core of at least one second material in a flowing system, comprising the following steps: (A) providing a main stream of a reaction gas or aerosol containing at least one precursor compound of the at least one first substance which is present in the core of the coated nanoparticle,
• step (B) transferring the at least one precursor compound present in the reaction gas or aerosol from step (A) into the corresponding at least one first material to form the core of the nanoparticle to be produced by thermal reaction in the main stream,
• step (C) adding a further reaction gas or aerosol containing at least one precursor compound of the at least one second substance which is present in the at least one shell, in cross-flow with respect to the main flow from step (B),
• step (D) transferring the at least one precursor compound present in the reaction gas or aerosol from step (C) into the corresponding at least one second substance to form the at least one shell of the nanoparticle to be produced by thermal reaction in the main stream and
• step (E) rapidly cooling the nanoparticle obtained in step (D) by adding a coolant to the main stream.
• the object is achieved by nanoparticles comprising a nonporous core of at least one first material and at least one porous shell of at least one second material at least partially surrounding the core, wherein the nanoparticles have a narrow particle size distribution through the use of such nanoparticles photocatalysis and by a device for carrying out the method according to the invention.
• all precursor compounds of the first substance in step (A) are suitable, which can be converted by a thermal treatment in the corresponding substances.
• the core of the nanoparticle contains at least one metal or semimetal oxide and the at least one shell of the nanoparticle contains at least one further metal or semimetal oxide.
• inorganic and organic compounds can be used as a precursor compound of the at least one metal or semimetal oxide which is present in the core of the coated nanoparticle according to the invention.
• Suitable metals or semimetals whose oxides are present in the core of the nanoparticle according to the invention and whose corresponding precursor compounds are used in step (A) are generally selected from the group consisting of elements of groups 1 to 15 of the Periodic Table of the Elements (according to IUPAC), Lanthanides, actinides and mixtures thereof, preferably from the group consisting of V, Ti, Zr, Ce, Mo, Bi, Zn, Mn, Si, Ba, Au, Ag, Pd, Pt, Ru, Rh, La and mixtures thereof.
• Suitable inorganic precursor compounds are, for example, the halogens, preferably the chlorides, carbonates, nitrates of the corresponding metals or semimetals and corresponding pure metals or semimetals, as organic precursor compounds are, for example, salts of the corresponding metals of alcohols having 1 to 8 carbon atoms, for example methanol, ethanol, n- or iso-propanol, tert-butanol and mixtures thereof.
• Other suitable organic precursor compounds are organometallic complexes.
• Titanium tetrachloride (TiCl 4 ), silicon tetrachloride (SiCl 4 ), tetraisopropyl orthotitanate, siloxanes such as hexamethyldisiloxane and mixtures thereof are particularly suitable as precursor compounds of the at least one metal or semimetal oxide in the core of the coated nanoparticle.
• TiCl 4 or SiCl 4 is used.
• tetraisopropyl orthotitanate or siloxanes such as hexamethyldisiloxane.
• a particularly preferred metal or semimetal oxide which is the core of Nanoparticle forms, TiC> 2 which is preferably present in more than 50%, particularly preferably 60 to 65% in the anatase modification.
• the reaction gas in step (A) is obtained by evaporating or evaporating the at least one precursor compound according to methods known to those skilled in the art.
• the temperature of the evaporation depends on the boiling point of the precursor compound to be evaporated.
• the evaporation or evaporation of the corresponding precursor compound can be carried out in an inert atmosphere, for example in nitrogen or a noble gas.
• the evaporation or evaporation can be carried out under atmospheric pressure or under a pressure below atmospheric pressure. If it evaporates or evaporates at a pressure below atmospheric pressure, the temperature can be chosen correspondingly lower. Alternatively, the precursor compound can be vaporized or evaporated even at higher pressure with elevation of the temperature.
• the precursor compound may also be in solution.
• Suitable solvents may be the solvents mentioned below as fuels.
• a reaction aerosol can also be used.
• aerosol is understood to mean a fine distribution of liquid mist droplets in a gaseous medium.
• the aerosol used in step (A) can be obtained by nebulising the at least one precursor compound of the metal or semimetal oxide present in the core or a solution thereof by methods known to those skilled in the art. Such methods are, for example, atomization by single-component or multi-component nozzles or ultrasonic atomizers.
• the gaseous carrier substance for the aerosol can be inert gases such as nitrogen, noble gases, oxygen or air or mixtures thereof.
• the carrier gas may also be a combustible gas, which serves as fuel in step (B) of the process according to the invention, for example.
• a fuel may be added to the reaction gas or reaction aerosol in step (A).
• This may be gaseous under the reaction conditions, or in the case of the use of an aerosol, be present as a finely divided liquid mist.
• Suitable fuels are for example hydrogen, carbon monoxide or hydrocarbons such as methane, ethylene, organic solvents such as xylene, toluene, benzene or mixtures thereof. If the process according to the invention is carried out industrially, hydrogen is a preferred fuel.
• Step (A) of the method according to the invention comprises providing a main stream of the above-mentioned reaction gas or aerosol.
• This main stream is preferably provided in a tubular reactor with the main stream flowing from the reactor inlet to the reactor outlet.
• the reactions which lead to the formation of the core-shell nanoparticles according to the invention are carried out while the substrates or the products of the individual process steps are moved with the main stream.
• step (A) can be carried out in a preferred embodiment by introducing the present components in the gaseous, vaporized, atomized or liquid state through a mixing device into the reactor and mixing them there.
• the pressure at which the reaction mixture is introduced into the reactor is generally up to 10 bar (gaseous precursor) or up to 100 bar (liquid precursor).
• a second gas stream which contains oxygen is fed simultaneously in parallel or transversely to the stream containing the reaction gas or aerosol.
• This second stream may contain pure oxygen or a mixture of oxygen and further components, other components being, for example, nitrogen or other inert gases. It can also be used air.
• Step (B) of the method according to the invention comprises
• step (B) transferring the at least one precursor compound present in the reaction gas or aerosol from step (A) into the corresponding at least one first material to form the core of the nanoparticle to be produced by thermal reaction in the main stream.
• step (B) of the process according to the invention the precursor compound of the first substance present in the core is converted by thermal treatment into the corresponding substance.
• the oxidizable compounds fed in (A) are used as fuel in step (B).
• the energy produced by burning this fuel is used to form the corresponding substance from the precursor compound, preferably the corresponding oxide.
• step (B) the core of the nanoparticle to be prepared according to the invention is formed while the main flow moves in the tubular reactor.
• the stream of a reaction gas or aerosol dwells in a preferred embodiment. Formation 1 to 1000 ms, more preferably 1 to 100 ms and most preferably 1 to 50 ms in the reaction zone, ie in the zone in which the thermal reaction of the precursor compound takes place in the corresponding preferred present in the core metal or Halbmetalloxid.
• the temperature in the reaction zone is preferably 600 to 2500 ° C., particularly preferably 800 to 1800 ° C. In this case, the temperature in a preferred embodiment is constant in the entire reaction zone.
• the particularly precisely adjustable residence time in the hot reaction zone according to the invention results in that the cores of the nanoparticles according to the invention are obtained in a very uniform primary particle size of preferably at most 1 .mu.m, particularly preferably 1 to 200 nm, very particularly 5 to 40 nm.
• the narrow particle size distribution of the nanoparticles according to the present invention is based on comparison with other nanoparticles produced by flame synthesis.
• the cores produced according to the invention are non-porous.
• step (C) of the process according to the invention another reaction gas or aerosol is produced from the main stream from step (B) comprising the cores of the nanoparticle to be prepared which have been produced in step (B) by thermal reaction of the corresponding precursor compounds in the flowing system, given.
• the further reaction gas or aerosol contains at least one precursor compound of the at least one second substance which is present in the at least one shell of the nanoparticle which can be prepared according to the invention.
• the nanoparticle produced according to the invention has a shell.
• the residence time between metering of the core material precursor at the main nozzle in step (A) and the addition of the coating material precursor in step (C) in a preferred embodiment is 1 to 1000 ms, more preferably 1 to 100 ms, and most preferably 1 to 20 ms.
• Preferred precursor compounds for forming the at least one shell of the nanoparticle according to the invention comprise compounds containing elements of groups 1 to 15 of the Periodic Table of the Elements (according to IUPAC), lanthanides, actinides and mixtures thereof, preferably selected from the group consisting of V, Ti, Zr, Ce, Mo, Bi, Zn, Mn, Si, Ba, Au, Ag, Pd, Pt, Ru, Rh, La and mixtures thereof. Very particular preference is given to Ti and Si.
• metals and semimetals mentioned are present in inorganic or organic compounds or as mixtures of both.
• suitable precursor compounds what has been said with regard to the precursor compounds for the metal or semimetal oxide which is present in the core of the particle according to the invention applies.
• titanium tetrachloride (TiCl 4 ) or silicon chloride (SiCl 4 ) are used as inorganic precursor compounds in step (C).
• tetraisopropyl orthotitanate (TTiP) or hexamethyldisiloxane (HMDS) are used as organic precursor compounds.
• TiP tetraisopropyl orthotitanate
• HMDS hexamethyldisiloxane
• TiCl 4 and SiCl 4 are preferred. If the process is carried out on a laboratory or pilot plant scale, tetraisopropyl orthotitanate or hexamethyldisiloxane are preferred precursor compounds.
• Particularly preferred oxides are SiO 2 , ZnO, CeO 2 , TiO 2 or SnO.
• reaction gas or aerosol can be produced in the same way as has already been described with regard to step (A) of the process according to the invention.
• this second reaction gas or aerosol is supplied at one or more circumferentially distributed locations in cross flow relative to the main stream which has been generated in steps (A) and (B). This can be done in a preferred embodiment by corresponding inlets or nozzles in the tubular reactor.
• cross-flow means that the reaction gas or aerosol impinges on the main stream containing the cores of the nanoparticle to be produced in step (B) at an angle ⁇ of 45 to 135 °, preferably 60 to 120 ° ,
• the tangential angle ⁇ in the equatorial plane to the main flow is in the range of -90 to + 90 °, preferably -30 to + 30 °.
• the cross-flow of the precursor compound of the shell with respect to the main stream causes the mixing time between core and precursor compound of the coating to be very short, so that the core is surrounded by a homogeneous concentration of the precursor compound and a porous shell is obtained which is as uniform as possible. is formed. Furthermore, varying the concentration of the precursor compound of the coating allows a variation of the layer thickness.
• the inventive method it is possible by the inventive method to produce coated nanoparticles, which are characterized by a narrow distribution of particle sizes, as well as by a very narrow distribution of the layer thicknesses. The narrow distribution of the particle size is clear from FIG.
• Step (D) of the method according to the invention comprises
• step (D) transferring the at least one precursor compound present in the reaction gas or aerosol from step (C) into the corresponding at least one second material to form the at least one shell of the nanoparticle to be produced by thermal reaction in the main stream.
• the at least one precursor compound of the at least one second substance, preferably at least one metal or semimetal oxide which is present in the at least one shell, applied to the core in step (C) is converted into the corresponding substance in step (D), preferably transfers the metal or semimetal oxide to form the at least one shell of the nanoparticle to be produced.
• This conversion is carried out according to the invention by thermal reaction of the precursor compounds, wherein the approximately isothermal reaction control allows the formation of a very homogeneous distribution of the layer thicknesses of the shell.
• step (D) the at least one shell of the nanoparticle is formed so that the nanoparticle according to the invention consists of a core and a shell that at least partially surrounds this core.
• the shell is preferably porous and preferably has a layer thickness of at most 10 nm, more preferably 0.1 to 3 nm.
• step (E) rapidly cooling the nanoparticle obtained in step (D) by adding a coolant.
• the nanoparticle obtained in step (D) comprising a core and at least one cladding is cooled as quickly as possible in step (E) by adding a coolant.
• the cooling rate in step (E) is preferably at least 10 4 K * s "1 , more preferably at least 10 5 K * s " 1, and most preferably at least 5 MO 5 K * s "1 .
• step (E) The cooling (quenching) in step (E) is carried out so that the temperature of the Christsgemsiches in the main stream after step (E) below the melting point of core and shell material, preferably ⁇ 800 0 C, more preferably ⁇ 400 0 C and very particularly preferably ⁇ 200 0 C is.
• the coolant in step (E) of the method according to the invention is a gas or a liquid.
• Suitable quench gases are in a preferred embodiment selected from the group consisting of air, nitrogen or other inert gases and mixtures thereof.
• suitable quenching liquids are selected from liquid nitrogen, organic solvents, for example diethylene glycol dimethacrylate, paraffin oil (white oil), tetrahydrofuran, naphtha, soybean oil, water or mixtures thereof. These organic solvents are sprayed liquid in a particularly preferred embodiment in the main stream.
• the addition of the quench liquid can be carried out in a preferred embodiment by appropriate inlets or nozzles.
• the quench liquid can be supplied at an angle ⁇ 'of 45 to 135 °, preferably 60 to 120 ° to the main stream, the angle ⁇ ' in the equatorial plane to the main flow is -90 to + 90 °, preferably -30 to + 30 °.
• step (E) may optionally be added a further step, which comprises the addition of an organic substance for surface modification of the resulting coated nanoparticles from step (E).
• Suitable surface modification agents are anionic, cationic, amphoteric or nonionic surfactants, e.g. Lutensol®, dispersants having a molecular weight of from 2 to 20,000 g / mol, e.g. Sokalan® or chemical surface functionalizing agents and any combination of these substances.
• these organic substances may also be used directly as the quenching liquid in step (E), or may be added to the quenching liquids mentioned above so that they are added directly in step (E).
• the nanoparticles obtained after step (E) are separated off as a powder or as a dispersion.
• the method according to the invention is followed by separation of the coated nanoparticles from gaseous impurities via a filter or cyclone.
• the present invention therefore also relates to nanoparticles which have a narrow particle size distribution for a flame synthesis, preparable by the process according to the invention.
• a narrow particle size distribution means that preferably ⁇ 70%, particularly preferably ⁇ 80%, very particularly preferably ⁇ 90% of the particle sizes are within a range of only 20, preferably 15, particularly preferably 10 nm from the average particle size differ.
• the core-shell nanoparticles produced by the process according to the invention are characterized in that they have a non-porous core and a porous coating.
• the specific adjustable by the various process parameters porosity and thickness of the coating makes it possible to adjust the catalytic activity of the core targeted to the appropriate requirements.
• the present invention also relates to nanoparticles comprising a non-porous core of at least one first material and at least one porous shell of at least one second material at least partially surrounding the core, wherein the nanoparticles have a ratio of photoactivity with respect to pollutant degradation to polymer degradation of more than 1, 8 have.
• the photoactivity against fluid pollutants is preferably more than 60% of the photoactivity of a standard photocatalyst (Degussa P25), more preferably more than 70%, most preferably more than 80%.
• the photoactivity towards fixed matrices is preferably less than 65% of the photoactivity of a standard photocatalyst (Degussa P25), more preferably less than 60%, and most preferably less than 55%.
• the ratio of the photoactivity with respect to pollutant degradation to photoactivity with respect to polymer degradation is more than 1.8, preferably more than 2, and more preferably more than 2.5.
• the non-porous core of the nanoparticle of the invention consists of TiO 2 and the porous shell of SiO 2 . That at the core TiC> 2 present in the nanoparticle is preferably more than 80%, particularly preferably 90 to 95%, in the anatase modification.
• the core of the nanoparticle according to the invention has a diameter of preferably at most 1 .mu.m and the shell of the nanoparticle has a thickness of at most 10 nm.
• the diameter of the core is 1 to 200 nm, more preferably 5 to 40 nm preferred embodiment, the layer thickness of the shell 0.1 to 10 nm, more preferably 0.1 to 3 nm.
• the porosity of the shell of these nanoparticles prepared according to the invention can be expressed by the ratio of the proportion Si in atom% to Ti in atom% and is 2 to 80, more preferably 5 to 60, particularly preferably 8 to 40, in each case measured via XPS (X-). Ray Photo Electron Spectroscopy - ESCA Electron Spectroscopy for Chemical Analysis).
• the present invention also relates to the use of these nanoparticles in photocatalysis.
• the present invention also relates to an apparatus for carrying out the method according to the invention, comprising in a tubular reactor
• the ratio of diameter to length of the tubular reaction space of the device according to the invention is 1/2 to 1/10, more preferably 1/4 to 1/6.
• Suitable units for supplying the reaction gas or aerosol containing at least one precursor compound of the at least one first substance present in the core and for forming a main flow in the tubular housing are selected from the group consisting of two-component nozzles, homogeneous mixing devices. These units mentioned are suitable for mixing the corresponding precursor compound and, if appropriate, fuels in the form of gases or liquid mists and optionally other gaseous components, for example an O 2 -containing gas, and to generate a main stream by injection into the reactor.
• the unit for thermal conversion of the at least one precursor compound contained in this reaction gas to the at least one core in a preferred embodiment is designed so that sufficient thermal energy is generated by combustion of the mixture containing the precursor compound of the metal or semimetal of the core, to the implementation of the precursor compound in the corresponding substance, preferably the corresponding oxide, with simultaneous formation of the nanoparticles takes place.
• the same temperature prevails in the reactor, with the exception of the point of cooling, preferably 600 to 2500 ° C., more preferably 800 to 1800 ° C. This constant temperature allows nanoparticles to be formed with a narrow particle size distribution.
• the unit for the thermal reaction of the precursor compounds which form the substance present in the core is preferably a part of the main stream generated at the beginning.
• the material, preferably the oxide, of the core is formed along the main flow.
• the reactor according to the invention is designed such that the residence time in the zone in which the cores are formed is preferably 1 to 1000 ms, particularly preferably 1 to 100 ms and very particularly preferably 1 to 50 ms.
• the unit for supplying the reaction gas or aerosol containing at least one precursor compound of the at least one second substance present in the at least one shell in cross-flow with respect to the main flow is, in a preferred embodiment, formed with nozzles attached to the inside of the tubular reactor which make it possible to make the reaction gas or aerosol at an angle ⁇ of preferably 45 to 135 °, particularly preferably 60 to 120 ° to the main flow.
• the unit for rapid cooling of the nanoparticles obtained in the device according to the invention is designed in a preferred embodiment such that cooling rates of greater than 10 4 K * s "1 , preferably 10 5 K * s " 1 , more preferably 5 * 10 5 K * s "1 can be achieved.
• the addition of the quench liquid can be carried out in a preferred embodiment by appropriate inlets or nozzles.
• the quench liquid can be supplied at an angle ⁇ 'of 45 to 135 °, preferably 60 to 120 ° to the main stream.
• the angle of attack ⁇ 'in the equatorial plane to the main flow is -90 to 90 °, preferably -30 to 30 °.
• the device according to the invention corresponds to the device shown in FIG.
• the reactor has at the top in the burner region a main nozzle (1) via which a liquid, dissolved for example in an organic solvent titanium precursor compound (3) with air (2) is atomized and burned.
• a liquid dissolved for example in an organic solvent titanium precursor compound (3) with air (2) is atomized and burned.
• preheated air and a fuel gas (4) eg, methane, ethylene
• an outer nozzle ring fuse burner
• the titanium precursor compound in reaction zone (8) is converted to TiC> 2 .
• a liquid silicon precursor compound is conveyed to an evaporator where it is mixed with preheated nitrogen and passed into the reaction space via annularly arranged openings (5) so that the vaporized silicon precursor compound meets the stream of atomized titanium precursor compound at right angles.
• the silicon precursor compound in the main stream is converted to SiC> 2 .
• the reaction mixture is then rapidly quenched with gaseous nitrogen at room temperature (6).
• the formed core-shell nanoparticles and exhaust gases can escape through the outlet (7).
• FIG. 2 shows the cross section of the reaction space in order to represent the angle of attack ⁇ or ⁇ 'in the equatorial plane relative to the main flow.
• FIG. 3 shows a TE M incorporation of a core-shell nanoparticle which has been produced by the process according to the invention.
• titanium dioxide precursor compound solution (batch: 284 g of tetraisopropyl orthotitanate (TTiP) and 716 g of xylene) per kg solution are fed to the main nozzle Nm 3 * h "1 air. Additional fuels, eg. B. Methane for the nozzle ring (2) is not used. After ignition (with a hydrogen ignition burner used only for start-up) a flame stabilizes in the reactor. A stream of 0 to 2.5 g * h "1 silicon dioxide precursor hexamethyldisiloxane (HMDS) is mixed with 0.80 Nm 3 * h " 1 nitrogen, evaporated at 130 0 C and introduced into the reactor. In the quench area, cool 25 Nm 3 * h "1 nitrogen the reaction mixture to 250 to 200 0 C.
• HMDS silicon dioxide precursor hexamethyldisiloxane
• Titanium dioxide coated with silicon dioxide is deposited as a fine powder with particle sizes of 5 to 100 nm (determined from TEM images) via a membrane filter.
• the layer thickness of the SiO 2 -HuIIe is determined by means of TE M recordings on a FEG-TEM (Field Emission Gun - Transmission Electron Microscopy) investigation method.
• the modification of the crystalline TiO 2 is determined by SAD (Selected Area Diffraction).
• the Si concentration is detected in EDXS (Energy Dispersive X-Ray Spectroscopy) analyzes and the weight percent Si confirmed by elemental analysis.
• the porosity of the SiO 2 layer is measured by XPS (X-Ray Photo Electron Spectroscopy - ESCA Electron Spectroscopy for Chemical Analysis). Table 2 shows the results:
• the photoactivities of the powders produced are determined by the rate of photocatalytic degradation of the chlorinated hydrocarbon dichloroacetic acid (DCA) in suspension.
• DCA chlorinated hydrocarbon dichloroacetic acid
• the total runtime of the experiments to check the rate of photocatalytic degradation of DCA under UV irradiation in aqueous solution is 24 hours.
• the UV light intensity is 1 mW / cm 2 .
• the pH of the suspension is adjusted to 3 with sodium hydroxide solution.
• the temperature in the reactor is in the range of 20 to 30 ° C.
• the concentration of DCA is 20 mmol / L, and the concentration of the photocatalyst is 3 g / L.
• Blank tests are carried out to degrade DCA under irradiation with the addition of a standard photocatalyst (Degussa P25). There will still be blind attempt to degrade DCA under UV irradiation without addition of photocatalyst.
• the rate of photocatalytic degradation of an organic matrix is measured by GC measurements of a polymer suspension in which the photocatalyst is introduced.
• the total running time of the tests for checking the rate of photocatalytic degradation under daylight irradiation (Suntest, 1 mW / cm 2 UV intensity) is 700 hours.
• the photocatalyst is stirred into a polymer suspension (eg Squalen®).
• the concentration of the photocatalyst is 0.25% by weight.
• Blank tests are carried out to degrade the polymers under irradiation with the addition of a standard photocatalyst (Degussa P25).
• Blank tests are also carried out to degrade the polymer under irradiation without addition of the photocatalyst.
• TOC means "totally organic carbon” Table 4: Polymer degradation

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