CN101213020B - Method for synthesis of carbon nanotubes - Google Patents

Abstract

The invention concerns a method for preparing carbon nanotubes by contacting a carbon source with a multivalent metal and/or metal oxide based catalyst deposited on an inorganic substrate of BET specific surface greater than 50m<2>/g. The resulting carbon nanotubes can be used as agents for improving the mechanical and electrical conductivity properties in polymer compositions.

Description

Translated fromChinese

碳纳米管的合成方法Synthesis of carbon nanotubes

本发明的目的是碳纳米管(NTC)的合成方法，该方法是在用特定无机基体承载的金属催化剂的存在下在气相中进行的。The object of the present invention is a process for the synthesis of carbon nanotubes (NTCs) carried out in the gas phase in the presence of a metal catalyst supported on a specific inorganic matrix.

现有技术current technology

今天，人们知道碳纳米管因其机械性能、非常高的形状比率(长度/直径)以及电性能而是具有很多优点的材料。Today, carbon nanotubes are known as materials with many advantages due to their mechanical properties, very high shape ratio (length/diameter) and electrical properties.

它们是由半球封端缠绕石墨层组成的，该半球是由接近富勒烯结构的五角形和六角形组成。They consist of wound graphite layers capped by a hemisphere composed of pentagons and hexagons close to the fullerene structure.

人们知道由单层组成的纳米管：因此称之为SWNT(单壁纳米管的英语缩写)，或知道由同心多层组成的纳米管，因此称之为MWNT(多重壁纳米管的英语缩写)。一般而言，SWNT的生产比MWNT的生产困难。Nanotubes are known as consisting of a single layer: hence the name SWNT (English abbreviation for single-walled nanotube), or as nanotubes consisting of concentric multilayers, hence the name MWNT (English abbreviation for multi-walled nanotube) . In general, the production of SWNTs is more difficult than that of MWNTs.

可以根据不同的方法生产碳纳米管，例如放电法、激光烧蚀法或蒸汽相化学沉积法(CVD)。Carbon nanotubes can be produced according to different methods, such as electrical discharge, laser ablation or vapor phase chemical deposition (CVD).

在这些技术中，这后一种技术似乎是唯一能容易保证大量地生产碳纳米管的技术，保证能够达到能使它们大量地用于聚合物和树脂应用中的成本的必要条件。Of these techniques, this latter technique appears to be the only one that can easily guarantee the production of carbon nanotubes in large quantities, at the cost necessary to make them available in large quantities in polymer and resin applications.

根据这个方法，把具有相对高温度的碳源注入到催化剂中，所述的催化剂可以是由无机固体承载的金属组成的。在这些金属中，优选地列举铁、钴、镍、钼，和在这些载体中，往往是氧化铝、二氧化硅或氧化镁。According to this method, a carbon source having a relatively high temperature is injected into a catalyst, which may consist of a metal supported on an inorganic solid. Among these metals, iron, cobalt, nickel, molybdenum are preferably cited, and among these supports, often alumina, silica or magnesia.

可考虑的碳源是甲烷、乙烷、乙烯、乙炔、乙醇、甲醇、丙酮，甚至合成气体CO+H₂(HIPCO方法)。Carbon sources that come into consideration are methane, ethane, ethylene, acetylene, ethanol, methanol, acetone, and even synthesis gas CO+H₂ (HIPCO process).

在涉及碳纳米管合成的文件中，可以列举Hyperion Catalysis International Inc.的WO 86/03455A1，它相应于EP 225.556B1，该文件可以认为是合成NTC的基础专利之一，它要求保护几乎圆柱形的碳原纤维(NTC的以前名称)，其直径是3.5-70nm，形状比率高于或等于100，以及它们的制备方法。Among the documents dealing with the synthesis of carbon nanotubes, one can cite the WO 86/03455A1 of Hyperion Catalysis International Inc., which corresponds to EP 225.556B1, which can be considered as one of the basic patents for the synthesis of NTCs, which claims almost cylindrical Carbon fibrils (former name of NTC), the diameter of which is 3.5-70 nm, the shape ratio is higher than or equal to 100, and their preparation method.

使含有铁(例如Fe₃O₄、碳载体承载的Fe、氧化铝载体承载的Fe或含碳原纤维制成的载体承载的Fe)的催化剂与含有碳(优选地CO或烃类)的气态化合物接触进行这种合成，有利地在能与碳进行反应生成气态产物(例如CO、H₂或H₂O)的化合物存在下。在这些实施例中，这些催化剂是采用干浸渍、沉淀或湿法浸渍方法制备的。Catalysts containing iron (such as Fe₃ O₄ , Fe on carbon supports, Fe on alumina supports, or Fe on supports made of carbon-containing fibrils) are mixed with gaseous The synthesis is carried out by contacting the compounds, advantageously in the presence of compounds capable of reacting with carbon to form gaseous products such as CO,_H2 or_H2O . In these examples, the catalysts were prepared by dry impregnation, precipitation or wet impregnation methods.

相应于同一申请人的EP 270.666 B1的WO 87/07559要求保护使用同样反应物和催化剂生产直径为3.5-70nm，而形状比率L/D为5-100的原纤维的方法。WO 87/07559 corresponding to EP 270.666 B1 of the same applicant claims a process for producing fibrils with a diameter of 3.5-70 nm and a shape ratio L/D of 5-100 using the same reactants and catalysts.

除了应该在含有碳的气态化合物是苯的情况下，在800℃以上进行操作外，没有给出有关产率(它应表示为每克催化剂每单位时间生成原纤维的质量)的任何信息。No information is given about the yield (which should be expressed as the mass of fibrils formed per gram of catalyst per unit time) except that the operation should be carried out above 800°C in the case where the gaseous compound containing carbon is benzene.

其它一些文件要求保护其改进方法，例如连续流化床，它能够控制催化剂和生成的含碳材料的聚集状态(例如参见以清华大学名义申请的WO02/94713A1)，或要求保护其改进产品，例如以Trustées Of Boston Collège名义申请的WO 02/095097 A1，它通过依靠催化剂性质和这些反应条件制备出非校直的不同形态的纳米管。Some other documents claim improved methods, such as continuous fluidized bed, which can control the aggregation state of catalyst and generated carbonaceous materials (see, for example, WO02/94713A1 filed in the name of Tsinghua University), or claim improved products, such as WO 02/095097 A1, filed in the name of Trustées Of Boston Collège, prepares non-aligned nanotubes of different morphologies by relying on catalyst properties and these reaction conditions.

Hyperion Catalysis International Inc.的US 2001/0036549 A1描述了通过与多价过渡金属或优选地金属混合物(例如Fe和Mo、Cr、Mn和/或Ce)接触的碳源的分解制备NTC的改进方法，其改进之处在于形成大量的尺寸为3.5-70nm的催化位点的过渡金属被承载于尺寸小于400μm的无机基体上。US 2001/0036549 A1 to Hyperion Catalysis International Inc. describes an improved method for the preparation of NTCs by decomposition of a carbon source in contact with a polyvalent transition metal or preferably a metal mixture such as Fe and Mo, Cr, Mn and/or Ce, The improvement is that transition metals forming a large number of catalytic sites with a size of 3.5-70 nm are carried on an inorganic matrix with a size of less than 400 μm.

在这些实例中，这种碳源是氢气/乙烯混合物，其各自分压是0.66和0.33，在650℃的反应时间是30分钟，这种催化剂是在甲醇存在下使用硝酸铁浸渍热解氧化铝(未给出铁含量，估计15％)制备得到的，其甲醇的量足以得到糊；产率是在30分钟6.9g/g，而当添加钼盐，对于铁含量约9-10％与钼含量1-2％时，其产率达到10.9-11.8。当共-金属是铈、铬、锰时，纳米管的产率分别是8、3、9.7和11。In these examples, the carbon source was a hydrogen/ethylene mixture with respective partial pressures of 0.66 and 0.33, the reaction time at 650°C was 30 minutes, and the catalyst was impregnated fumed alumina with ferric nitrate in the presence of methanol (iron content not given, estimated 15%) was prepared in an amount of methanol sufficient to obtain a paste; yield was 6.9 g/g in 30 minutes, and when molybdenum salts were added, about 9-10% for iron content with molybdenum When the content is 1-2%, the yield reaches 10.9-11.8. When the co-metals were cerium, chromium, manganese, the yields of nanotubes were 8, 3, 9.7 and 11, respectively.

还证实，乙酰基丙酮铁的效率不如硝酸铁。It was also confirmed that iron acetylacetonate is not as efficient as iron nitrate.

在实施例16中，在pH基本等于6时，通过同时添加硝酸铁和碳酸氢钠溶液进行沉淀的湿法进行浸渍。当铁含量为15％与往该反应器中半连续加入时，该催化剂达到的选择性是10.5。In Example 16, at a pH substantially equal to 6, the impregnation was carried out by a wet method of precipitation by simultaneous addition of ferric nitrate and sodium bicarbonate solutions. The catalyst achieved a selectivity of 10.5 when the iron content was 15% and fed semi-continuously to the reactor.

采用铁和钼湿法浸渍的另一个实施例得到了与甲醇法同样好的结果。Another example using iron and molybdenum wet impregnation gave equally good results as the methanol method.

这个文件还表明，用以Mo计高于2.5％含量的钼代替铁更确切地说是不利的，因为等比例Fe和Mc(总量＝16.7％)混合物在30分钟内的产率达到8.8。This document also shows that the substitution of molybdenum for iron with a content higher than 2.5% based on Mo is rather disadvantageous, since a mixture of equal proportions of Fe and Mc (total=16.7%) gives a yield of 8.8 within 30 minutes.

当使用非多孔载体，例如Hyperion所使用的比表面积＝100m²/g的Degussa热解氧化铝时，证实浸渍大量的铁是困难的，因为只是外层是气体可到达的，这些内层没有充分的催化作用。When using a non-porous support such as Degussa fumed alumina with a specific surface area = 100 m² /g used by Hyperion, it is difficult to demonstrate impregnation of large quantities of iron because only the outer layers are gas accessible, these inner layers are not sufficiently catalytic effect.

另外，使用这类载体的技术是复杂的，因为这些微粒的尺寸是20nm，其散装密度是0.06，这样增加了工业使用的难度。In addition, the technique of using such carriers is complicated because the size of these particles is 20 nm and their bulk density is 0.06, which increases the difficulty of industrial use.

本发明的目的是通过分解碳源合成NTC的方法，将碳源置于反应器中，优选地在流化床反应器中，在温度500-1500℃下，使该碳源与一种或多种氧化态为零和/或呈氧化物形式(正氧化态)的多价过渡金属进行接触，以及回收所述的NTC，其特征在于这种或这些过渡金属和/或其一种或多种氧化物是用BET比表面积高于50m²/g，优选地70m²/g至300m²/g的基体承载的；在这些载体中，优选地可以列举这些无机载体，有利地为γ或θ型氧化铝。The object of the present invention is to synthesize NTC by decomposing a carbon source. The carbon source is placed in a reactor, preferably in a fluidized bed reactor, and at a temperature of 500-1500° C., the carbon source is mixed with one or more contacting a polyvalent transition metal in oxidation state zero and/or in the form of an oxide (positive oxidation state), and recovering said NTC, characterized in that the transition metal(s) and/or one or more thereof The oxide is supported by a substrate with a BET specific surface area higher than 50 m² /g, preferably 70 m² /g to 300 m² /g; among these supports, preferably these inorganic supports can be cited, advantageously of the gamma or theta type alumina.

根据一种优选的实施方式，这些载体易于浸渍一定量的多价过渡金属和/或过渡金属氧化物，例如，过渡金属的质量可以是直到该最终的催化剂的50重量％，有利地地是最终的催化剂的15-50重量％，优选地30-40重量％。According to a preferred embodiment, these supports are liable to be impregnated with a certain amount of polyvalent transition metals and/or transition metal oxides, for example, the mass of transition metals can be up to 50% by weight of the final catalyst, advantageously the final 15-50% by weight of the catalyst, preferably 30-40% by weight.

有利地选择载体微粒的尺寸，以使得在NTC合成反应时该催化剂有良好的流化。在实际中，为了保证合理产率，载体微粒直径在广义上约20-500μm是更优选的。当然，如果该载体微粒的尺寸是在前面所指出的范围之外，也没有超出本发明的范围。The size of the support particles is advantageously chosen such that the catalyst is well fluidized during the NTC synthesis reaction. In practice, a carrier particle diameter in the broad sense of about 20-500 µm is more preferred in order to ensure a reasonable yield. Of course, it is within the scope of the invention if the size of the carrier particles is outside the range indicated above.

有利地，在干燥气体吹扫下，进行载体微粒的浸渍，例如在室温至该溶液沸腾温度的温度下，当该过渡金属是铁时以硝酸铁水溶液方式；选择浸渍溶液的量，以便这些载体微粒随时与足够量的溶液接触，从而保证在所述载体微粒上形成表面膜。Advantageously, the impregnation of the support particles is carried out under a dry gas purge, for example in the form of an aqueous solution of ferric nitrate when the transition metal is iron, at a temperature ranging from room temperature to the boiling temperature of the solution; the amount of impregnation solution is chosen so that the supports The microparticles are contacted at any time with a sufficient amount of solution to ensure the formation of a surface film on the carrier microparticles.

“干”加工事实，即随时正好具有在催化载体微粒表面形成液膜所必需的液体量是有利的，因为这样在以干燥空气吹扫方式加热时能够避免这些含水排放物(例如当该浸渍溶液含有硝酸铁时硝酸盐含水排放物；浸渍后，得到的产物以惰性或非惰性气体形式被加热到约300℃，以除去这些硝酸盐)。The "dry" processing fact that there is at any time just the amount of liquid necessary to form a liquid film on the surface of the catalytic carrier particles is advantageous because these aqueous discharges can be avoided when heating with dry air blowing (for example when the impregnating solution Aqueous discharge of nitrates when ferric nitrate is present; after maceration, the resulting product is heated to about 300°C with inert or non-inert gas to remove these nitrates).

根据优选的实施方式，在该合成反应器中，有利地在流化床合成反应器中原位进行这种催化剂的还原反应，而这种催化剂不再接触空气，因此，这种或这些过渡金属，优选地铁保持金属形式。According to a preferred embodiment, in the synthesis reactor, the reduction of this catalyst is advantageously carried out in situ in a fluidized bed synthesis reactor, without this catalyst being in contact with the air, so that the transition metal(s), Preferably the subway remains in metallic form.

在使用金属氧化物形式的，优选地氧化铁形式的催化剂连续合成NTC的情况下，该催化剂可以直接注入该反应介质中，无须通过还原步骤。因此有利地避免安装还原反应器和/或储存呈还原形式的催化剂，而这种催化剂应在惰性气体下使用。In the case of continuous synthesis of NTCs using a catalyst in the form of metal oxides, preferably in the form of iron oxides, the catalyst can be injected directly into the reaction medium without going through a reduction step. It is therefore advantageous to avoid installing a reduction reactor and/or storing the catalyst in reduced form, which should be used under inert gas.

该碳源可以选自任何种类的含碳材料，例如甲烷、乙烷、丙烷、丁烷、其它高级脂族链烷、苯、环己烷、乙烯、丙烯、丁烯、异丁烯、其它高级脂族链烯、甲苯、二甲苯、枯烯、乙苯、萘、菲、蒽、乙炔和高级炔、甲醛、乙醛、丙酮、甲醇、乙醇、一氧化碳等，它们是单独的或混合的。The carbon source can be selected from any kind of carbonaceous material, such as methane, ethane, propane, butane, other higher aliphatic alkanes, benzene, cyclohexane, ethylene, propylene, butene, isobutylene, other higher aliphatic Alkenes, toluene, xylene, cumene, ethylbenzene, naphthalene, phenanthrene, anthracene, acetylene and higher alkynes, formaldehyde, acetaldehyde, acetone, methanol, ethanol, carbon monoxide, etc., individually or in combination.

根据上述方法得到的NTC可以用于许多技术领域中，尤其是电子(根据温度和其结构，它们可以是导体、半导体和绝缘体)、机械，例如用于增强复合材料(这些NTC比钢坚固100倍而轻六倍)和电动机械(通过注入填料可以将它们伸长或收缩)技术领域中。例如可以列举NTC在大分子组合物中的用途，这些大分子组合物用于例如电子组件的包装、油管(燃油管线)、抗静电涂层或涂料的生产的用途，和在热敏电阻、超级容量电极等的用途。NTCs obtained according to the method described above can be used in many technical fields, especially electronics (depending on temperature and their structure, they can be conductors, semiconductors and insulators), mechanics, for example for the reinforcement of composite materials (these NTCs are 100 times stronger than steel and six times lighter) and electromechanical (they can be stretched or shrunk by injecting fillers) technology. One can cite, for example, the use of NTC in macromolecular compositions for applications such as the packaging of electronic components, oil pipes (fuel lines), antistatic coatings or coatings, and in thermistors, super Capacitive electrodes, etc.

实施例1Example 1

使用Puralox NWA 155γ氧化铝制备催化剂，该Puralox NWA 155γ氧化铝的5重量％以下的微粒小于100μm，而2％以下大于500μm，中值直径是约250μm。这些表面特征和空隙度特征列于下面：The catalyst was prepared using Puralox NWA 155 gamma alumina with less than 5% by weight of particles smaller than 100 μm and less than 2% larger than 500 μm with a median diameter of about 250 μm. These surface and porosity characteristics are listed below:

BET表面(m²/g)        154BET surface (m² /g) 154

总孔体积(cm³/g)      0.45(采用DFT测量0-200nm的孔)Total pore volume (cm³ /g) 0.45 (use DFT to measure the pores of 0-200nm)

微孔体积(cm³/g)      0.005(采用t-plot测量0-2nm的孔)。Micropore volume (cm³ /g) 0.005 (use t-plot to measure pores of 0-2 nm).

在加热到100℃的3L夹套反应器中，加入300g氧化铝，用空气吹扫。然后利用泵连续注入700ml含有545g/l无水硝酸铁的铁溶液。目标比(金属质量/催化剂质量)是15％铁金属，该铁溶液的添加时间是10小时，该液体添加速度等于水的蒸发速度。In a 3 L jacketed reactor heated to 100°C, 300 g of alumina was charged and purged with air. Then, 700 ml of iron solution containing 545 g/l anhydrous ferric nitrate was continuously injected by means of a pump. The target ratio (mass of metal/mass of catalyst) was 15% iron metal, the addition time of the iron solution was 10 hours, and the liquid addition rate was equal to the evaporation rate of water.

该催化剂然后置于100℃烘箱中16小时。The catalyst was then placed in an oven at 100°C for 16 hours.

实施例2Example 2

使用中值直径约85μm的Puralox SCCA 5-150γ氧化铝制备催化剂。The catalyst was prepared using Puralox SCCA 5-150 gamma alumina with a median diameter of approximately 85 μm.

这些表面特征和空隙度特征列于下面：These surface and porosity characteristics are listed below:

BET表面(m²/g)                148BET surface (m² /g) 148

总孔体积(cm³/g)    0.47(采用DFT测量0-200nm的孔)Total pore volume (cm³ /g) 0.47 (use DFT to measure the pores of 0-200nm)

微孔体积(cm³/g)    0.0036(采用t-plot测量0-2nm的孔)Micropore volume (cm³ /g) 0.0036 (use t-plot to measure 0-2nm pores)

以与实施例1相同方式进行制备催化剂与浸渍。Catalyst preparation and impregnation were performed in the same manner as in Example 1.

实施例3Example 3

使用同样的SCCA 5-150氧化铝，通过在接近于实施例2的条件下浸渍制备含有25％铁的催化剂：按希望设定的铁含量的比例简单地调节添加时间与溶液体积，即16小时。Using the same SCCA 5-150 alumina, a catalyst containing 25% iron was prepared by impregnation under conditions close to Example 2: simply adjust the addition time and solution volume in proportion to the desired iron content, i.e. 16 hours .

该催化剂然后置于100℃烘箱中16小时。The catalyst was then placed in an oven at 100°C for 16 hours.

实施例4Example 4

通过浸渍SCCA 5-150氧化铝制备含有35％铁的催化剂。按希望设定的铁含量的比例简单地调节添加时间与溶液体积，即23小时。A catalyst containing 35% iron was prepared by impregnating SCCA 5-150 alumina. Simply adjust the addition time to the solution volume in proportion to the iron content desired to be set, ie 23 hours.

该催化剂然后置于100℃烘箱中16小时。The catalyst was then placed in an oven at 100°C for 16 hours.

实施例5Example 5

通过浸渍SCCA 5-150氧化铝制备含有50％铁的催化剂。按希望设定的铁含量的比例简单地调节添加时间与溶液体积，即32小时。Catalysts containing 50% iron were prepared by impregnating SCCA 5-150 alumina. Simply adjust the addition time and solution volume in proportion to the iron content desired to be set, ie 32 hours.

该催化剂然后置于100℃烘箱中16小时。The catalyst was then placed in an oven at 100°C for 16 hours.

实施例6Example 6

使用中值直径为150μm的Engelhard的C 500-511γ氧化铝制备催化剂。The catalyst was prepared using Engelhard's C 500-511 gamma alumina with a median diameter of 150 μm.

这些表面特征和空隙度特征列于下面：These surface and porosity characteristics are listed below:

BET表面(m²/g)        206BET surface (m² /g) 206

总孔体积(cm³/g)      0.48(采用DFT测量0-200nm的孔)Total pore volume (cm³ /g) 0.48 (use DFT to measure the pores of 0-200nm)

微孔体积(cm³/g)      0(采用t-plot测量0-2nm的孔)Micropore volume (cm³ /g) 0 (use t-plot to measure the pores of 0-2nm)

采用实施例3的条件，制备含有25％铁的催化剂。该催化剂置于100℃下16小时。Using the conditions of Example 3, a catalyst containing 25% iron was prepared. The catalyst was placed at 100°C for 16 hours.

实施例7Example 7

使用中值直径为70μm的Engelhard的C 500-512θ氧化铝制备催化剂。The catalyst was prepared using Engelhard's C 500-512θ alumina with a median diameter of 70 μm.

这些表面特征和空隙度特征列于下面：These surface and porosity characteristics are listed below:

BET表面(m²/g)        93BET surface (m² /g) 93

总孔体积(cm³/g)      0.37(采用DFT测量0-200nm的孔)Total pore volume (cm³ /g) 0.37 (use DFT to measure the pores of 0-200nm)

微孔体积(cm³/g)      0.003(采用t-plot测量0-2nm的孔)Micropore volume (cm³ /g) 0.003 (use t-plot to measure 0-2nm pores)

在与实施例3的相同条件下，采用浸渍法制备含有25％铁的催化剂。Under the same conditions as in Example 3, a catalyst containing 25% iron was prepared by an impregnation method.

实施例8Example 8

将质量约150g的层状催化剂装入直径为25cm、有效高度为1m的反应器中进行催化测试，该反应器配备了用于避免将细微粒带到下游的分离器。在氮气下在300℃加热使这些硝酸盐分解，然后在氢气和氮气(20％/80％体积/体积)下加热至到650℃。在这个温度下，设定乙烯流量为3000NL/小时，氢气流量为1000NL/小时，这相应于乙烯分压为0.75。A layered catalyst with a mass of about 150 g was loaded into a reactor with a diameter of 25 cm and an effective height of 1 m, equipped with a separator to avoid carrying fine particles downstream, for catalytic testing. These nitrates were decomposed by heating at 300°C under nitrogen and then up to 650°C under hydrogen and nitrogen (20%/80% v/v). At this temperature, the ethylene flow rate was set at 3000 NL/hour and the hydrogen flow rate was 1000 NL/hour, which corresponds to an ethylene partial pressure of 0.75.

气体流量应足以使这种固体大大超过流化极限速度，同时依然低于飞出速度。The gas flow rate should be sufficient to drive this solid well above the fluidization limit velocity while still below the fly-off velocity.

60分钟后，停止加热，估计生成产物量结果。同时，采用显微镜法评估生成纳米管量(生成NTC类型：SWNT或MWNT；

存在C的其它形式)。After 60 minutes, the heating was stopped and the amount of product produced was estimated. At the same time, the amount of nanotubes produced was evaluated by microscopy (generated NTC type: SWNT or MWNT;

Other forms of C exist).

这些结果汇集于下表中：These results are compiled in the table below:

作为对比，US 2001/0036549的实施例10描述了由氢气/乙烯混合物与含有12％铁的催化剂接触合成NTC，该催化剂是用硝酸铁浸渍的热解氧化铝制备的；在30分钟内催化剂的NTC产率是5.5。For comparison, Example 10 of US 2001/0036549 describes the synthesis of NTC by contacting a hydrogen/ethylene mixture with a catalyst containing 12% iron, prepared from fumed alumina impregnated with iron nitrate; The NTC yield was 5.5.

实施例9Example 9

将实施例4制备的催化剂加到实施例8的反应器中，并在300℃加热以分解这些硝酸盐。用空气冷却该反应器并回收该催化剂。没有经受还原步骤的并因此呈铁氧化物形式的这种催化剂，然后再被加入到被加热至650℃的实施例8反应器中，直接在乙烯和氢气流中，其中乙烯分压是0.8。反应60分钟后，停止加热，评估生成产物的量与质量结果。得到14.6的产率，该结果与使用还原催化剂得到的结果是可比较的；生成的NTC是MWNT型的/

10-30nm，它们不含有碳的其它形式。The catalyst prepared in Example 4 was added to the reactor of Example 8 and heated at 300°C to decompose these nitrates. The reactor is cooled with air and the catalyst is recovered. This catalyst, not subjected to the reduction step and thus in the form of iron oxide, was then recharged to the reactor of Example 8 heated to 650°C directly in a flow of ethylene and hydrogen with an ethylene partial pressure of 0.8. After reacting for 60 minutes, the heating was stopped, and the amount and quality results of the generated product were evaluated. A yield of 14.6 was obtained, which was comparable to that obtained using the reduced catalyst; the NTCs formed were of the MWNT type/

10-30nm, they do not contain other forms of carbon.

Claims (8)

1. through decomposing the method for carbon source synthesizing carbon nanotubes, under temperature 500-1500 ℃, to make this carbon source that places fluidized-bed reactor be zero with oxidation state and/or the iron that is oxide form contacts, and reclaim described CNT, it is characterized in that:

-iron and/or its oxide are to use the BET specific area to be 70m²/ g-300m²The matrix of/g carries, and this matrix is selected from γ or θ type aluminium oxide,

-use dipping solution this matrix of dipping under dry gas purges that contains at least a molysite to prepare catalyst; And select the amount of dipping solution; So that these carrier particles enough contact with the solution that guarantees the amount of formation skin covering of the surface on said carrier particles at any time with just in time

The amount of-iron is the 15-50 weight % of final catalyst.

2. method according to claim 1 is characterized in that catalyst is iron oxide based.

3. method according to claim 1 and 2, the amount that it is characterized in that iron are the 30-40 weight % of final catalyst.

4. method according to claim 1 and 2 is characterized in that these catalyst particles are the particulate form of diameter 20-500 μ m.

5. method according to claim 1 and 2 is characterized in that said catalyst is through using the iron nitrate aqueous solution impregnation matrix to prepare.

6. method according to claim 5 is characterized in that said catalyst is through using iron nitrate aqueous solution impregnation matrix under the temperature between room temperature to this dipping solution boiling temperature to prepare.

7. method according to claim 1 and 2 it is characterized in that this catalyst original position reduces, and this catalyst contacts no longer with air.

8. method according to claim 1 and 2 is characterized in that this method is continuous.