EP3021966A1

EP3021966A1 - Method for producing an efficient catalyst for generating multi-walled carbon nanotubes, multi-walled carbon nanotubes and carbon nanotube powder

Info

Publication number: EP3021966A1
Application number: EP14739419.1A
Authority: EP
Inventors: Heiko Hocke; Stefan Grasser; Oliver Felix Karl SCHLÜTER
Original assignee: Covestro Deutschland AG
Current assignee: Covestro Deutschland AG
Priority date: 2013-07-19
Filing date: 2014-07-14
Publication date: 2016-05-25
Also published as: DE102013214229A1; CN105451883A; WO2015007670A1; JP2016530083A; US20160160394A1; KR20160034292A

Abstract

The invention relates to a method for producing a catalyst for the synthesis of multi-walled carbon nanotubes. The invention also relates to a method for producing multi-walled carbon nanotubes and a carbon nanotube powder with improved properties and comprising said carbon nanotubes.

Description

Process for the preparation of an efficient catalyst for the production of multi-walled carbon nanotubes, multi-walled carbon nanotubes and carbon nanotube powders

The invention relates to a process for the preparation of a catalyst for the synthesis of multi-walled carbon nanotubes. Furthermore, the invention relates to a method for producing multi-walled carbon nanotubes and a carbon nanotube powder having these properties and having these carbon nanotubes.

In the prior art, carbon nanotubes are understood to mean mainly cylindrical carbon tubes having a diameter of between 1 and 100 nm and a length which corresponds to a diameter of between 1 and 100 nm

Multiple of the diameter. These tubes consist of one or more layers of ordered carbon atoms and have a different nucleus in morphology. These carbon nanotubes are also referred to as "carbon fibrils" or "hollow carbon fibers", for example. Carbon nanotubes have long been known in the literature. Although Iijima (Publication: S. Iijima, Nature 354, 56-58, 1991) is commonly referred to as the discoverer of nanotubes, these materials, particularly multi-graphene fibrous graphite materials, have been known since the 1970's and early 1980's, respectively. Tates and Baker (GB 1469930A1, 1977 and EP 0056004A2, 1982) described for the first time the deposition of very fine fibrous carbon from the catalytic decomposition of hydrocarbons. However, the carbon filaments made from short-chain hydrocarbons are no longer characterized in terms of their diameter.

The production of carbon nanotubes with diameters smaller than 100 nm is described for the first time in EP 205 556B1 or WO 86 / 03455A1. For the preparation herein, light (i.e., short and medium chain aliphatic or mononuclear or dinuclear aromatic) hydrocarbons and an iron based catalyst are used where carbonaceous compounds are decomposed at a temperature above 800 ° C - 900 ° C.

The methods known today for producing carbon nanotubes include arc, laser ablation and catalytic processes. In many of these processes, carbon black, amorphous carbon and high-diameter fibers are formed as by-products. In the catalytic process, a distinction can be made between the deposition on registered catalyst particles and the deposition on in-situ formed metal centers with diameters in the nanometer range (so-called flow processes). In the production via the catalytic separation of carbon from gaseous hydrocarbons at reaction conditions (hereinafter CCVD; Catalytic Carbon Vapor Deposition) are mentioned as possible carbon donors acetylene, methane, ethane, ethylene, butane, butene, butadiene, benzene and other carbon-containing educts.

The catalysts usually include metals, metal oxides or decomposable or reducible metal components. For example, in the prior art, as the candidate metals for metals, Fe, Mo, Ni, V, Mn, Sn, Co, Cu and others are mentioned. Although the individual metals usually alone have a tendency to catalyze the formation of nanotubes. However, according to the prior art, high yields of nanotubes and small amounts of amorphous carbons are advantageously achieved with metal catalysts which contain a combination of the abovementioned metals.

Particularly advantageous catalyst systems based on the prior art are based on combinations containing Fe, Co or Ni. The formation of carbon nanotubes and the properties of the tubes formed depend in a complex manner on the metal component used as catalyst or a combination of several metal components, the carrier material used and the interaction between catalyst and carrier, the educt gas and partial pressure, an admixture of hydrogen or other gases, the reaction temperature and the residence time or the reactor used. Optimization represents a special challenge for a technical process.

Typical structures of carbon nanotubes are those of the cylinder type (tubular structure). The cylindrical structures are differentiated between single-walled carbon nanotubes (SWCNT) and multi-walled carbon nanotubes (MWCNTs). Common processes for their preparation are e.g. Arc discharge, laser ablation, chemical vapor deposition (CVD process) and catalytic vapor deposition (CCVD process).

After an arc process, such cylindrical carbon tubes can also be produced. Iijima (Nature 354, 1991, 56-8) reports the formation of carbon tubes in the arc process which consist of two or more graphene layers rolled up into a seamlessly closed cylinder and nested together. Depending on the rolling vector, chiral and achiral arrangements of the carbon atoms along the longitudinal axis of the carbon fiber are possible.

The method described in WO 2009/036877 A2 makes it possible to produce carbon nanotubes which have a so-called scroll structure in which one or more graphs consisting of two or more superimposed graphite layers form a rolled structure.

Other known structures of carbon nanotubes are described in a review (Milne et al. Encyclopedia of Nanoscience and Nanotechnology, 2003, Volume X, pp. 1-22, ISBN 1-58883-001-2), and are the, herringbone 'Structure or the cup-stacked and the stacked structure, the bamboo structure, the platelet structure. Carbon nanofibers can also be produced by means of electrospinning of polyacrylonitrile and subsequent graphitization (Jo et al Macromolecular Research, 2005, Volume 13, pp 521-528).

It should be noted that the metal component used in the CCVD and referred to as a catalyst is consumed in the course of the synthesis process. This consumption is due to a deactivation of the metal component, eg. B. due to deposition of carbon on the entire particle, which leads to the complete coverage of the particle (this is known to the skilled person as "Encapping".) A reactivation is usually not possible or economically not useful The catalyst here comprises the whole of the support and the catalyst used, and owing to the described consumption of catalyst, a high yield of carbon nanotubes, based on the catalyst used, is an essential requirement for catalyst and process.

With the increasing industrial and technological importance of the carbon nanotubes, in addition to the requirements for a highly efficient, economical and scalable production process of the CNT, the nature and properties of the carbon nanotubes or the carbon nanotube powder resulting from these compositions, in particular the purity, the processability and performance has increased. In order to achieve the highest possible economic efficiency, in addition to the costs for the raw material, in particular the catalyst costs, the space-time yield, i. which amount of CNT can be produced in a given reactor volume per time is of crucial importance.

Oberlin, Endo and Koyama have described a way of producing cylindrical carbon nanotubes in the state of the art (Carbon 14, 1976, 133), in which aromatic hydrocarbons, such as benzene, are reacted on a metal catalyst, in particular iron, at about 1100.degree. C. in a fly-back reactor. This forms carbon nanotubes with a graphitic core, which is however covered with a coating of amorphous carbon. A subsequent technically and economically complex thermal treatment at high temperatures, usually above 1800 ° C, of these fibers then leads to a product with predominantly graphitic carbon. In this case, a part of the catalyst is often removed, whereby a purification takes place. The product is very low or not entangled, which means the handling on Grand of low bulk density and the extreme dusting behavior is very difficult.

Another process for producing carbon nanotubes is described in US Pat. No. 7,198,772B2 (Hyperion Catalysis International), in which ethylene is reacted at temperatures of approximately 680 ° C. over an iron-containing catalyst. The catalysts used for CNT synthesis are obtained both by precipitation of active metal, usually iron and molybdenum, on a support such as aluminum oxide, aluminum hydroxide or magnesium oxide and by co-precipitation of active metal and support. The CNTs thus produced are isolated in the form of aggregates with yields of 11.4-46 g of CNT per 1 g of catalyst. The co-precipitated catalysts generally show a higher efficiency.

The application WO 2006/050903 (Bayer MaterialScience AG) describes a catalyst system which can already be used very efficiently for the production of carbon nanotubes. Cobalt, manganese, magnesium and aluminum salts are simultaneously co-precipitated under basic conditions. The application WO 2009 / 043445A1 describes the preparation of a catalyst by means of spray drying, in which the starting salts can also be partly dispersed in a solvent. However, no co-precipitation, especially not under basic conditions, takes place. The yields were about 25 to 34 g carbon nanotubes per gram of catalyst used. As a result, with the above-described prior art, it is only possible to a limited extent to produce carbon nanotubes in high purity and at low cost.

The object of the present invention is to provide a supported catalyst which on the one hand can be produced inexpensively on the one hand, but on the other hand, the production of carbon nanotubes with increased efficiency both with respect to the catalyst used and to the space-time - Yield in the reactor allowed.

The invention is further based on the object to provide an improved CNT production process in which carbon nanotubes with high quality and excellent properties, eg with a very high surface area, can be obtained. For economic reasons, moreover, a catalyst is desirable in which, by only slightly varying the CNT production conditions, eg the temperature, with otherwise almost the same reactor design and process management different, optimized to the particular intended use CNT, especially with different specific surface produced can. The object is achieved according to the invention by a process for producing a catalyst at least consisting of one or more active metals and one or more support materials, comprising the following steps: a) presentation of a substrate in powder form, which serves as a support material for the catalyst, and dispersing the substrate powder in a solvent by mechanical action and adjustment of the dispersion to a pH of at least 8, preferably at least 9, more preferably at least 9.5 and at most 13 b) adding one or more metal salt solutions containing precursor compounds of catalytic active metals and support metals, optionally adjusting the chosen pH so that they are co-precipitated and simultaneously precipitated onto the previously dispersed substrate powder, c) separation and isolation of the precipitated solid, d) optional washing of the solid with solvent, e) spray-drying or optionally grinding and / or screening (classification) f) optionally calcination at 200 ° C to 950 ° C, preferably 400 ° C to 900 ° C, more preferably 400 ° C to 850 ° C with reduction or Oxidation with subsequent reduction g) reduction of the catalyst material formed.

Preferred precursor compounds of the catalytic active metals are preferably those of one or more metals selected from the group: iron, cobalt, nickel, manganese or molybdenum.

Particular preference is given to using compounds of cobalt and manganese as precursor compounds, preferably in a mixture.

Preferred precursor compounds for carrier materials are selected from one or more compounds of the group of the compounds of magnesium, aluminum, silicon, titanium, barium or calcium.

Particularly preferred as precursor compounds for support materials are compounds of magnesium and / or aluminum.

The average particle diameter of the substrate powder submitted from step a) is preferably less than 1 mm, particularly preferably less than 0.1 mm and in particular less than 0.02 mm. Preferred as precursor compounds for catalyst or carrier independently of one another are water-soluble salts, in particular nitrates, nitrites, chlorides, sulfates, carboxylates, in particular acetates or citrates, of the abovementioned metals. The metal compounds are particularly preferably in the form of nitrates or acetates. A preferred embodiment of the novel process is characterized in that the metals in the form of their oxides or hydroxides, mixed oxides / hydroxides, or mixed oxides or mixed hydroxides are present in the isolated solid from step c).

In a further preferred method, the grain diameter of the main fraction of the catalyst after spray-drying and / or grinding and sieving according to step e) is in the range from 0.01 to 1 mm, preferably 0.02 to 0.25 mm and in particular 0.03 and 0 , 12 mm.

The novel catalyst preparation process is preferably carried out so that the solvent used for steps a), b) and optionally d) one or more selected from the group: water, alcohols, ethers, ketones is used. Water is particularly preferably used as solvent. In a further preferred variant of the novel process, the dispersion is intensively homogenized during the addition of the metal salt solution in step b), in particular by stirring or by means of high-pressure dispersion.

In another preferred embodiment of the new method, the adjustment and adjustment of the pH in the dispersion by means of alkali or ammonium hydroxide, or alkali or ammonium carbonate, or alkali or ammonium bicarbonate, in particular with alkali or ammonium hydroxide. These substances are added in particular in the form of an aqueous solution of the dispersion.

Preferred alkali metal compounds are those of lithium, sodium or potassium, particularly preferred are sodium compounds. The precipitation b) is preferably carried out at a temperature of the dispersion to 100 ° C, preferably at ambient temperature.

A preferred method is characterized in that the ratio of metal content in mol% of the catalytically active metal in the catalyst to the metal of the support 90/10 to 5/95, preferably 80/20 to 20/80, particularly preferably 70/30 to 30 / 70 is. The ratio of the content of submitted substrate metal for the catalyst support to precipitated substrate metal for the catalyst support in mol% is 1/99 to 95/5, in a preferred embodiment of the process from 2/98 to 50/50.

Another object of the invention is a catalyst obtained from a new catalyst production process as described above.

The invention also relates to the use of a catalyst prepared by the novel catalyst preparation process as described above for producing fibrous carbon materials, in particular carbon nanotubes.

The invention further provides a process for the production of fibrous carbon (carbon nanotubes) by preparing catalyst with the novel catalyst preparation process as described above,

Introducing the catalyst from the catalyst preparation process into a suitable reactor, preferably with a moving reaction bed and in particular a fluidized bed,

Generation of carbon nanotubes by reaction of carbonaceous gases (precursor) in the presence of the catalyst at elevated temperature, in particular at least 500 ° C to 1000 ° C, preferably 550 ° C to 850 ° C, more preferably 600 ° C to 750 ° C optionally in the presence of hydrogen and / or inert gas, in particular nitrogen and / or noble gas and discharge of the carbon nanotubes and other reaction products from the reactor.

In the context of the invention it has been found that, in contrast to the prior art, in a process with these steps, carbon nanotubes with very high efficiency, ie both very high CNT yields based on the catalyst used and on the space-time in the reactor, to be obtained. In addition, when using the catalyst according to the invention by varying the temperature in the CNT production step, the surface of the CNT formed can be selectively changed and adjusted. With the new production process for carbon nanotubes basically all types of carbon nanotubes are accessible. Examples of carbon nanotube types are: single wall nanotubes with a single graphene-like layer, multi-wall nanotubes with multiple graphene-like layers; Carbon nanotubes with a tubular structure, bamboo, ring-bone, cup-stacked, winding or scroll structure; so-called capped carbon nanotubes, in which at least one tubular graphene-like layer is closed at their ends by fullerene hemispheres; or any combination of the aforementioned species, as well as carbon nanofibers and boron- or nitrogen-containing carbon nanotubes (B-CNT, N-CNT). In the following, the carbon nanotube production process will be described in more detail in general and in specific embodiments.

The carbon nanotube production process is preferably carried out in a moving bed of a reactor. A reactor with a moving bed is procedurally delimited in particular by a fixed bed reactor and by a reactor without a bed, such as, for example, an entrained flow reactor. In a reactor with a bed, the substrate is spatially located above a support. In the case of a fixed bed reactor, for example, the substrate can be contained in an upwardly opened boat, the boat serving as a carrier here. The substrate is therefore substantially at rest during the process. The carbonaceous precursor preferably contains or consists of an optionally substituted aliphatic, cyclic, heterocyclic, aromatic or heteroaromatic compound or a mixture thereof.

Aliphatic means unbranched, branched and / or cyclic alkane, alkene or alkyne. Preferably, the aliphatic molecules have from about 1 to about 20, more preferably from about 1 to about 12, and most preferably from about 2 to about 6 carbon atoms.

Practical experiments have shown that particularly good results are obtained when the carbon-containing precursor is an at least partially unsaturated or aromatic compound or the precursor contains such a compound or a mixture thereof.

Examples of partially unsaturated compounds are unbranched, branched and / or cyclic alkenes or alkynes, which may be optionally substituted.

"Alkene" as used herein means a hydrocarbon base element which contains at least one carbon-carbon double bond.Carbon-containing precursors which can be used according to the invention are, for example, ethylene, propene, butene, butadiene, pentene, isoprene, hexene, 1-, 2- or 3 Hexene, 1-, 2-, 3-, or 4-octene, 1-nonene or 1-decene, which may be optionally substituted, such as acrylonitrile.

"Alkyne" as used herein means a hydrocarbon base member containing at least one carbon-carbon triple bond. Preferred carbonaceous precursors include, for example, ethyne, propyne, butyne, pentyne, hexyne, 1-, 2- or 3-heptynol, 1-, 2-, 3-, or 4-octyne, nonyne, or decin, which may be optionally substituted As cyclic alkenes or alkynes, non-aromatic, mono- or multicyclic ring systems of, for example, about 3 to about 10, preferably about 5 to about 10 carbon atoms in question, which in the case of the cycloalkenes at least one carbon-carbon double bond in the case of the cycloalkynes, at least one carbon-carbon triple bond. Examples of monocyclic cycloalkenes are cyclopentene, cyclohexene, cycloheptene and the like. An example of a multicyclic alkene is norbornene.

The carbonaceous precursor may also contain or consist of an optionally substituted heterocyclic molecule. Herein, "heterocyclic" means a mono- or multicyclic ring system of from about 3 to about 10, preferably from about 5 to about 10, more preferably from about 5 to about 6 carbon atoms wherein one or more carbon atoms in the ring system are replaced by heteroatoms.

"Heteroatom" as used herein means one or more atoms of oxygen, nitrogen or boron, with the respective oxidized forms included.

According to a particularly preferred embodiment of the invention, the heterocyclic compounds used as carbonaceous precursors contain at least one carbon-carbon or carbon-heteroatom double bond.

"Aromatic molecule" or "aromatic compound" as used herein includes optionally substituted carbocyclic and heterocyclic compounds containing a conjugated double bond system. Heterocyclic aromatics are also referred to as "heteroaromatics." Examples of aromatic molecules according to the invention are optionally substituted monocyclic aromatic rings having 0 to 3 heteroatoms independently selected from O, N and B, or 8 to 12 membered aromatic bicyclic ring systems 0 to 5 heteroatoms, which are selected independently of one another from O, N and B. Suitable carbonaceous precursors which can be used according to the invention are, for example, optionally substituted benzene, naphthalene, anthracene, pyridine, quinoline, isoquinoline, pyrazine, quinoxaline, acridine, pyrimidine, chi nazoline, pyridazine, cinnoline, furan, benzofuran, isobenzofuran, pyrrole, indole, isoindole, imidazole, benzimidazole, purine, pyrazole, indazole, oxazole, benzoxazole, isoxazole, benzisoxazole, if this is referred to as "optionally substituted", this means that the molecule or the compound can either be unsubstituted or several, bev orzugt 1 to 3, substituents can carry. The substituents may be purely aliphatic or contain one or more heteroatoms. According to a preferred embodiment, the substituents are selected from the group consisting of Ci to Cio-aliphatic, C3 to Cio-cycloaliphatic, CÖ to Cio-aryl, 5- to 10-membered heteroaryl or 3- to 10-membered heterocyclyl Ci - to C 6 haloalkyl, ci to Cio alkoxy, halogen, N0 ₂ , -OH, -CN,. Particularly preferred examples of carbonaceous precursors which have achieved good to very good results in practice are unsaturated hydrocarbons such as ethylene or acrylonitrile and aromatic molecules such as benzene or pyridine.

Catalysts which cause carbon nanotubes to grow in length are used in particular in the production of carbon nanotubes in known processes. For example, iron, cobalt or nickel-containing catalysts are often used for this purpose.

During the catalytic production of carbon nanotubes, residues of the catalyst used regularly remain in the carbon nanotube powder produced. These catalyst residues can be largely removed from the carbon nanotube powder by an acid wash, in particular with hydrochloric acid, so that acid-cleaned carbon nanotubes only have very low catalyst residue contents.

In a further embodiment of the novel CNT production process, a fluidized bed of a fluidized bed reactor is used as the moving bed. By means of nozzle openings provided in the carrier, a gas stream is introduced into the CNT catalyst (and optionally into an auxiliary bed), so that the CNT catalyst (and optionally the auxiliary bed) and the gas stream form a so-called fluidized bed. The fluidized bed is characterized by a liquid-like behavior in which the individual particles of the CNT catalyst are mixed in the gas stream. In addition to good mixing of the CNT catalyst, a good heat and mass transfer is achieved in the fluidized bed, so that essentially homogeneous process conditions are present in the fluidized bed. This gives a product with very homogeneous physical and chemical properties. In experiments, correspondingly high yields were achieved with the fluidized bed reactor.

For example, a fluidized-bed reactor in which the reactor is essentially formed by a quartz glass housing, for example a quartz glass tube, can be used as the fluidized-bed reactor.

In an alternative embodiment of the method, the moving bed may also be provided by a rotary tube reactor. A rotary tube reactor has a reactor tube, the longitudinal axis of which is aligned at a small angle of, for example, 1-5 ° to the horizontal. The reactor tube is rotatably mounted about its longitudinal axis and driven for rotation about this axis. For the implementation of the method, the CNT catalyst is first applied to the inner surface of the reactor tube. Subsequently, the reactor tube is rotated about its longitudinal axis, while a carbon-containing precursor is introduced into the reactor tube. The process can be operated in cocurrent, ie reaction gas and catalyst or CNT move in the same direction, or in countercurrent. Preference is given to working with counterflow. In a further embodiment of the method in which the fluidized bed of a fluidized-bed reactor is used as the moving bed, a gas flow through the fluidized bed is adjusted in such a way that stable fluidization is achieved. With this gas flow range, experimentally good yields were found. For controlling the yield and the process itself, it is also possible to use gas mixtures, for example a mixture of an inert carrier gas with the carbonaceous precursor.

Stable fluidization means that the gas flow has a velocity that is greater than or equal to the minimum fluidization velocity. For determining the minimum fluidization velocity, reference is made to WO 2007 / 118668A2, the content of which is intended to be part of the present description by reference. In particular, reference is made to formula (1) on page 7 of WO 2007 / 118668A2 for determining the minimum fluidization rate.

The carbon nanotube production process can be carried out continuously, quasi-continuously or discontinuously. In a preferred continuous process procedure, the fluidized-bed reactor is continuously supplied with CNT catalyst and / or taken from produced carbon nanotubes. In a batch process, the process is carried out in successive batches. For a batch, a CNT catalyst is charged, and the product obtained is substantially completely withdrawn from the fluidized bed reactor at the end of the process. In a quasi-continuous procedure, only a certain portion of the product is removed from the fluidized-bed reactor at the end of a process and the CNT catalyst is replenished accordingly.

In a further embodiment of the method, in particular in the quasi-continuous or batchwise process, a process duration of between 10 and 600 minutes, preferably 10 to 120 minutes. and especially 20 to 50 min set. Preferably, the process time is adjusted so that the bulk density of the carbon nanotubes or agglomerates produced after the end of the process in the range 10 to 500 g / L, preferably 40 to 250 g / L and in particular 60 to 150 g / L.

The production of carbon nanotubes with doped graphene-like layers can be achieved in a further preferred embodiment of the method in that the carbon-containing precursor contains or consists of a compound comprising carbon and at least one heteroatom from the group consisting of nitrogen or boron , Alternatively, the carbonaceous precursor may also contain at least two compounds, at least one of which comprises carbon and at least one other thereof comprises an element selected from the group consisting of nitrogen and boron. A doping is understood to mean that the otherwise graphene-like structure of a layer in addition to the carbon atoms additionally has foreign atoms, preferably at least 1.5 at.%, Preferably at least 2 at.%, More preferably at least 5 at.%, In particular at least 10 at. %). These can be arranged, for example, instead of carbon atoms on lattice sites or impurities of the graphene lattice. An undoped layer is understood to mean a graphene-like layer which has not been deliberately doped by foreign atoms, so that the defects within this layer lie in the natural impurity region, ie in particular in the region <1 at.%>, In particular <0.5 at.%.

The object of the invention is further solved by a carbon nanotube powder containing the above-described carbon nanotubes.

The carbon nanotubes of the carbon nanotube powder preferably have an average diameter of 1 to 100 nm, preferably 3 to 50 μm, in particular 5 to 25 nm. This diameter range corresponds to frequent technical specifications and can be easily achieved with the invention. The carbon nanotube powder preferably has a purity of at least 90%, preferably of at least 95%, more preferably of at least 97%, more preferably of at least 98%. In the present context, purity is understood as meaning the proportion in% by weight of carbon nanotubes in the powder compared to other constituents, in particular amorphous carbon and inorganic metal oxides. It has been found that carbon nanotube powders of high purity can be produced with the present invention.

Carbon nanotubes having a ratio of length to outer diameter of greater than 5, preferably greater than 100, are particularly preferably obtained.

The carbon nanotubes are particularly preferably obtained in the form of agglomerates, the agglomerates in particular having a mean diameter in the range of 0.05 to 5 mm, preferably 0, 1 to 2 mm, particularly preferably 0.2 to 1 mm.

The invention therefore also relates to the use of fibrous carbon materials produced by a novel process for the production of fibrous carbon, as described above in electrode materials, lithium ion batteries, polymeric, ceramic or metallic composites, in membranes, as a catalyst support and for the improvement of mechanical or electrically conductive properties of composite materials. Examples

Experimental part

General Procedure Experiment 1 - 9. a) Preparation of Solutions: were prepared of 19.4 g Co (N03) 2 * 6H20 four solutions of deionized in 50 ml of water, 17.0 g Mn (N03) 2 _* 4H20 in 50 ml deionized water,

A1 (NO 3) 3 * 9H 2 O (amount see Table 1) in 35 ml of deionized water and 30.6 g of Mg (NO 3) 2 _* 6H 2 O in 35 ml of deionized water. The manganese nitrate hydrate solution and cobalt nitrate hydrate solution were then combined (solution A), the aluminum nitrate hydrate solution and magnesium nitrate hydrate solution were also combined (solution B). The two resulting solutions (A and B) were then also combined and stirred for 5 minutes (solution C). A solution hereinafter referred to as solution D was prepared by stirring 60 g of solid sodium hydroxide (NaOH) in 211 ml of deionized water to give a 22.1% by weight NaOH solution. b) Precipitation: At room temperature (about 23 ° C), both solutions (C and D) were added to a multi-necked round-bottom flask with intensive stirring and 200 ml deionized water

Aluminum hydroxide (Reflamal® S20 from Dadco, amount see Table 1) metered, wherein the pH was maintained by NaOH solution addition at about pH = 10. The precipitation took about 30-40 minutes. After dosing was stirred for 10 min. c) Filtration / washing: The solid obtained was filtered after the precipitation. Subsequently, the solid was washed by three times slurrying. The amount of

Washing water was about 1 L. d) Drying: The catalyst was dried overnight at 120 ° C under air. e) Grinding / Screening: Before being used in the CNT synthesis, which took place in a fluidized fluidized bed, the dried particles were ground by means of an IKA mill (M 20) and then supported by a screening machine AS 20 from Retsch sieved a corresponding air jet sieve. The fraction 0.03-0.1 mm was used for CNT synthesis. As a quality for grindability, the percentage amount of Gutkornfraktiion was taken in relation to the used regrind, whereby proportion of good grain> 60% = good, 60- 40% = medium and <40% = poorly evaluated. f) Calcination (optional): In some cases (see Table 1), the catalyst was heated after milling / sieving and before testing in CNT synthesis in air at 400 ° C for 6 hours. g) CNT synthesis:

The catalysts prepared as described above were tested in a fluid bed apparatus on a laboratory scale. For this purpose, a defined amount of catalyst (0.5 g) was placed in a heated from the outside by a tube furnace quartz glass reactor with an inner diameter of 5 cm. The temperature of the fluidized bed was controlled by a PID control. The temperature of the fluidized bed was determined by a thermocouple. Feed gases and inert diluent gases were fed into the reactor via electronically controlled mass flow controllers.

The reactor was then inertized with nitrogen and heated to a fixed temperature (Table 1). Thereafter, the reactant gas was added as a mixture of ethene, hydrogen and the inert nitrogen directly. The volume flows (based on standard liters of LN) were as follows: ethene 6 LN-min ¹ , hydrogen 3 LN-min ¹ and nitrogen 1 LN-min ¹ set. The charging of the catalyst with the educt gases was carried out for a period of 33 minutes. Thereafter, the current reaction was stopped by interrupting the Eduktzufuhr, the reactor purged with nitrogen, cooled and taken from the reactor contents. The results are summarized in Table 1. Indication of the catalyst activity with respect to mass of the "incombustible / irreversible" portions of the catalyst ("loss on ignition yield")

The oxide catalyst for CNT synthesis always contains a certain amount of water, which depends on the history of the catalyst, especially the drying and calcination. For better comparison of the actual yield of the experiments with each other, therefore, the method of determining the loss on ignition is best suited.

The amount of carbon deposited was determined by weighing. The "incombustible / irreplaceable" portion of the CNTs was determined by heating in a muffle furnace at 650 ° C. for 6 hours in air, and the amount of deposited carbon in relation to the incombustible portion (catalyst residue), hereinafter referred to as yield, became Based on the mass of catalyst residue (mkat) and the weight gain after reaction (m total mkat) defined: Yield = (m total mkat) / mkat.

Determination of the Specific Surface Area of the CNTs by the BET Method The CNTs were pretreated as follows: 150 ° C / 0.1 mbar / 16 h; N ₂ - Adsorption by multipoint BET method at -196 ° C (analogous to DIN ISO 9277) Determination of the bulk density of CNTs

The determination was made according to EN ISO 60.

Claims

Patent claims

1. A process for preparing a catalyst at least consisting of one or more active metals and one or more support materials comprising the steps: a) presentation of a substrate in powder form, which serves as a support material for the catalyst, and dispersion of the substrate powder in a solvent by mechanical action and Adjusting the dispersion to a pH of at least 8, preferably at least 9, more preferably at least 9.5 and at most 13 b) adding one or more metal salt solutions containing precursor compounds of catalytic active metals and support metals, optionally adjusting the selected pH c) precipitating and isolating the precipitated solid, d) optionally washing the solid with solvent, e) spray-drying or drying and optionally milling and / or sieving (cl f) optionally calcination at 200 ° C to 950 ° C, preferably 400 ° C to 900 ° C, more preferably 400 ° C to 850 ° C with reduction or oxidation with subsequent reduction g) reduction of the catalyst material formed.

2. The method according to claim 1, characterized in that as precursor compounds of the catalytic active metals selected from one or more metals selected from the group: iron, cobalt, nickel, manganese or molybdenum.

3. The method according to claim 1 or 2, characterized in that compounds of cobalt and manganese are used as precursor compounds.

4. The method according to any one of claims 1 to 3, characterized in that the precursor compounds for support materials are selected from one or more compounds of the group of compounds of magnesium, aluminum, silicon, titanium, barium or calcium.

5. The method according to any one of claims 1 to 4, characterized in that the precursor compounds for support materials are compounds of magnesium and / or aluminum.

6. The method according to any one of claims 1 to 5, characterized in that in the isolated solid from step c) the metals in the form of their oxides or hydroxides, mixed oxides / hydroxides, or mixed oxides or mixed hydroxides are present.

7. The method according to any one of claims 1 to 6, characterized in that the grain diameter of the main fraction of the catalyst after spray drying and / or grinding and sieving according to step e) in the range of 0.01 to 1 mm, preferably 0.02 to 0, 25 mm and in particular 0.03 and 0.12 mm.

8. The method according to any one of claims 1 to 7, characterized in that the solvent for the steps a), b) and optionally d) one or more selected from the group: water, alcohols, ethers, ketones.

9. The method according to any one of claims 1 to 8, characterized in that the dispersion during the addition of the metal salt solution in step b) is intensively homogenized, in particular by stirring or by means of high-pressure dispersion.

10. The method according to any one of claims 1 to 9, characterized in that the adjustment and adjustment of the pH in the dispersion by means of alkali or ammonium hydroxide, or alkali or ammonium carbonate, or alkali metal or ammonium bicarbonate, in particular with alkali metal or ammonium hydroxide.

11. The method according to claim 10, characterized in that alkali compounds are those of lithium, sodium or potassium, preferably sodium.

12. The method according to any one of claims 1 to 11, characterized in that the precipitation b) at a temperature of the dispersion to 100 ° C, preferably at ambient temperature.

13. The method according to any one of claims 1 to 12, characterized in that the ratio of metal content in mol% of the catalytically active metal in the catalyst to the metal of the carrier 90/10 to 5/95, preferably 80/20 to 20/80, especially preferably 70/30 to 30/70.

14. The method according to any one of claims 1 to 13, characterized in that the ratio of the content of submitted substrate metal for the catalyst support to precipitated Sub- stratmetall for the catalyst support in mol% 1/99 to 95/5 and preferably from 2/98 to 50/50.

15. The method according to any one of claims 1 to 14, characterized in that the mean grain diameter of the substrate powder submitted from step a) is less than 1 mm, more preferably less than 0.1 mm and in particular less than 0.02 mm.

16. A catalyst obtained from a process according to any one of claims 1 to 15.

17. Use of a catalyst prepared according to claims 1 to 15 for the production of fibrous carbon materials, in particular of carbon nanotubes.

18. A process for producing fibrous carbon by preparing the catalyst by the process according to any one of claims 1 to 15,

Generation of carbon nanotubes by reaction of carbonaceous gases in the presence of the catalyst at elevated temperature, in particular at least 500 ° C to 1000 ° C, preferably 550 ° C to 850 ° C, more preferably 600 ° C to 750 ° C optionally in the presence of hydrogen and or inert gas, in particular nitrogen and / or noble gas and

Discharge of the carbon nanotubes and other reaction products from the reactor.

19. The use of fibrous carbon materials prepared by a process according to claim 18 in electrode materials, lithium ion batteries, polymeric, ceramic or metallic composites, in membranes, as a catalyst support and for improving mechanical or electrically conductive properties of composite materials.