WO2025027320A1

WO2025027320A1 - Fc-cvd continuous synthesis apparatus and process

Info

Publication number: WO2025027320A1
Application number: PCT/GB2024/052012
Authority: WO
Inventors: Adam Boies; Michael GLERUM; James Elliott; Martin Pick
Original assignee: Cambridge Enterprise Limited
Priority date: 2023-08-01
Filing date: 2024-07-30
Publication date: 2025-02-06
Also published as: GB202311814D0

Abstract

A process for the production of a material agglomerate is described. The process comprises: (a) providing a temperature-controlled flow-through reactor; (b) introducing a flow of metal catalyst or metal catalyst precursor into the temperature-controlled flow-through reactor; (c) introducing a flow of a source of production material into the temperature-controlled flow-through reactor; (d) operating the source of thermal energy to expose the metal catalyst or metal catalyst precursor and source of production material to a temperature in a reaction zone of the flow-through reactor that is sufficient to generate particulate metal catalyst and to produce a production material precursor; (e) displacing the production material precursor as a continuous discharge through a discharge outlet of the temperature-controlled flow-through reactor; (f) collecting the continuous discharge. The method is characterised in that the source of thermal energy comprises a heat source within the flow through volume spaced apart from the reactor wall, the said heat source providing at least a major part of the thermal energy to raise the temperature of materials in the reaction zone of the flow-through reactor. An apparatus for performing the method is also described.

Description

FC-CVD^CONTINUOUS^SYNTHESIS APPARATUS^AND^PROCESS Field^of^Invention The invention relates to an apparatus and process for the synthesis of material agglomerates in the gas phase via a continuous floating catalyst chemical vapour deposition (FC-CVD) process. The invention in particular embodiments relates for example to an apparatus and process for carbon nanotube (CNT) aerogel and for example for the production of single-walled or multi-walled carbon nanotubes, but may find general application in relation to the fabrication of other one-dimensional nanomaterials such as nanotubes, nanorods and nanowires of other composition. Background^to^the^Invention The remarkable mechanical and electronic properties exhibited by nanomaterials, and in particular one-dimensional nanomaterials such as nanotubes, nanorods and nanowires, such as carbon nanotubes, have encouraged efforts to develop mass production techniques. As will be understood in the art, one-dimensional nanomaterials are materials with one dimension outside the nanoscale and include nanotubes, nanorods and nanowires. The invention is not limited by particular size, but typically a one-dimensional nanomaterial might generally be understood to be limited in the two nanoscale dimensions to no more than 5000 nm and to have a high aspect ratio with a long axial direction that is at least ten times the diameter. The invention is particularly exemplified herein in relation to the production of carbon nanotubes, but the skilled person will appreciate that the principles so exemplified may find application across a range of other one- dimensional nanomaterials such as nanotubes, nanorods and nanowires of other composition. Carbon nanotubes have been produced previously using various approaches including the laser or arc-discharge ablation of a carbon/catalyst mixture target. For larger scale synthesis, the most promising methods have been based on chemical vapour deposition (CVD). CVD typically uses a cheap feedstock and has relatively low energy requirements, and has therefore attracted interest for the purposes of bulk synthesis. In CVD methods, a carbon-containing gas is decomposed at high temperatures in the reaction zone of a furnace under the influence of a finely divided catalyst (usually iron, nickel, cobalt or other transition metals or alloys). A process for the synthesis of single-walled or multi-walled agglomerates, again exemplified for the fabrication of carbon nanotubes in the gas phase is described in WO2005/007926A2. Floating catalyst chemical vapor deposition (FC-CVD) using hot-walled ceramic reactors, and for example tube furnaces, is a known technique for the continuous synthesis of carbon nanotube (CNT) aerogel that can be directly transformed into a CNT mat or fibre. This method produces individual CNTs with the highest aspect ratio (lengthCNT / diameterCNT, AR, 10⁴ – 10⁵) and the highest carbon double bond percentage (crystallinity, G/D ratio). The uptake of the synthesis technique, however, is currently limited with some inherent issues such as scalability limits of the process. The lack of process design focusing on improving the low production density (10^-4 – 10⁰ kg/h/m³) and the energy intensity of the synthesis (10³ – 10⁵ MJ/kgCNT) has resulted in CNT textiles being less competitive with CNT powder counterparts for price/kilo (10,000 – 100, 000 $/kg_{CNT, textile}, 100 – 1000 $/kg_{CNT, powder}). One significant limitation when it comes to scale-up is the use of ceramic walled reactors for example formed as tube furnaces in hot-wall CVD processes. The tubes are necessary due to the high temperature (1100 – 1500°C) required for synthesis. Variations of the thermal input to the process gases within FC-CVD literature has been limited, contrary to other CVD techniques, such as substrate grown CVD (SG-CVD) used to synthesise CNTs. Improving SG-CVD has involved trialing multiple thermal sources, including hot-wire filaments, plasmas and electrical resistant furnaces with success in improving the production density by reducing reactor volume. The limited attempts within the FC-CVD literature provide opportunity for improving the power density (W/m³) of the system and improving the production densification to make CNT textile more cost competitive. Improving the production densification (kg/h/m³) can also be achieved by either utilising a smaller reactor volume or increasing the mass flow of feed, however, high mass flows (0.5 – 1 kg/s) require a large thermal flux (10⁶ W/m³). For the synthesis temperatures required, the power density cannot be realised with current furnace designs. The limited number of advancements addressing these issues prevent process scalability. Other issues surrounding present FC-CVD processes and apparatus include the low catalyst utilisation, with the effective number of catalysts being the lowest of all CNT CVD techniques (average = 0.053%). This is predominantly due to rapid particle coagulation growing to particle sizes that reduce the growth rate (k_grow ∝ 1/d_p), losses of small particles (1 – 5 nm) diffusing to the walls of the reactor (~50 – 90%) and two zones of nucleation of the catalyst particles, caused by evaporation in the furnace. The process effectively relies on the secondary nucleation zone to provide ~90% of the CNT mass, located in the downstream zone of the furnace. This occurs when the hydrocarbon has undergone pyrolysis contacting the nucleating catalyst sites. Crucially, literary evidence has shown that separate injection of the CH4 and catalyst precursors could synthesise material continuously, allowing for precise injection locations of the precursors, limiting the mentioned losses. Currently, however, hot wall furnaces such as tube furnaces with ceramic walls limit the ability to separately introduce catalyst precursors into the reaction at a desired location whilst preventing unwanted catalyst precursor decomposition. Injecting catalyst precursors into the furnace at either the entry or exit leads to uncontrollable particle size distributions and number concentrations with limited optimization possible. Recent work has shown that optimising the delivery of catalyst precursors with a high jet velocity can benefit the quantity and quality of CNT aerogel. In this arrangement, however, recirculation of the catalyst is likely, increasing the residence time and therefore the catalyst particle size, affecting the CNT growth. It is desirable to develop apparatus and processes for the synthesis of single-walled or multi-walled carbon nanotubes in the gas phase via a continuous floating catalyst chemical vapour deposition (FC-CVD) process that mitigate some or all of these disadvantages of prior art apparatus and processes, and in particular that mitigate some or all of the disadvantages arising in hot-wall CVD processes using hot wall furnaces such as tube furnaces with ceramic walls. Summary^of^Invention In accordance with the invention in a first aspect, a process for the production of carbon nanotubes comprises: (a) providing a temperature-controlled flow-through reactor having a flow-through volume defined by a reactor wall, and provided with a source of thermal energy operable to control the temperature of a reaction zone therein; (b) introducing a flow of metal catalyst or metal catalyst precursor into the temperature-controlled flow-through reactor; (c) introducing a flow of a source of production material into the temperature- controlled flow-through reactor, wherein the source comprises a source of production material selected from the group comprising at least one of Ti, Zn, B, N, C; (d) operating the source of thermal energy to expose the metal catalyst or metal catalyst precursor and source of production material to a temperature in a reaction zone of the flow-through reactor that is sufficient to generate particulate metal catalyst and to produce a production material precursor; (e) displacing the production material precursor as a continuous discharge through a discharge outlet of the temperature-controlled flow-through reactor; (f) collecting the continuous discharge; wherein the source of thermal energy comprises a heat source within the flow through volume spaced apart from the reactor wall, the said heat source providing at least a major part of the thermal energy to materials in the flow-through reactor volume. The general process of the generation of a continuous discharge of carbon nanotubes will be familiar. In CVD methods, a carbon-containing gas is decomposed at high temperatures in the reaction zone of a furnace under the influence of a catalyst. A heat source is used to raise the materials (eg, carbon-containing gas, carrier gas, metal catalyst precursor) to the required temperature to be decomposed in a reaction zone of a reactor. The invention is distinctly characterised by the provision of a heat source comprising one or more thermal elements within the flow through volume spaced apart from the reactor wall. The internal heat source is preferably such as to provide at least a major part of the necessary thermal energy to raise the temperature of the materials in reaction zone of the flow-through reactor to one that is sufficient to generate particulate metal catalyst and to produce carbon nanotube aerogel. In some embodiments, the heat source comprising one or more thermal elements within the flow through volume spaced apart from the reactor wall may provide all the thermal energy to the reaction zone. The reactor wall does not need to be, and in preferred embodiment is not, provided with thermal elements so as to act as a source of thermal energy to the reaction zone. In such a case, the sole source of thermal energy to a reaction zone defined in the flow through reactor volume may be provided only by one or more thermal elements within the flow through volume spaced apart from the reactor wall, and no thermal elements are provided in the reactor wall. This does not necessarily, although in embodiments it may, exclude the possibility of providing a more complete reaction system with further heating elements either upstream or downstream of the flow through reactor volume. Such an arrangement may offer advantages over a co-axial arrangement that has both central and peripheral heating, and is thus potentially less restrictive of the geometry. The reactor body may in such a case have any suitable geometry and not be restricted to cylindrical cross-section. In preferred embodiments, the process comprises introducing a flow of metal catalyst or metal catalyst precursor into the temperature-controlled flow-through reactor at a location downstream of the said heat source within the flow through volume spaced apart from the reactor wall. Thus, the catalyst or precursor does not directly pass the thermal elements within the volume, and this may avoid deposits thereon that may otherwise occur through thermal degradation of the catalyst or precursor. In particular preferred embodiments, the source of thermal energy to a reaction zone defined in the flow through reactor volume comprises and preferably is provided only by one or more thermal elements within the flow through reactor volume spaced apart from the reactor wall and extending along a longitudinal portion of the flow through reactor volume, and the flow of metal catalyst or metal catalyst precursor is introduced into the temperature-controlled flow-through reactor at a location downstream thereof. The heat source for example comprises a radiative heat source, that is to say, a heat source that is configured to provide thermal energy to materials in the flow-through reactor volume via a radiative heat transfer mechanism. A radiative heat source may for example, comprise a sheathed radiative heat source, for example comprising one or more sheathed heating elements. Additionally or alternatively the heat source may comprise a conductive or convective heat source, that is to say, a heat source that is configured to provide thermal energy to materials in the flow-through reactor volume via a heat conductive and/ or convective heat transfer mechanism. In preferred embodiments, a thermal medium may be provided as discussed below, and the heat transfer mechanism is at least in part and preferably in substantial part by conduction from a radiative heat source via the thermal medium. In some embodiments, the method is applied to the generation of a continuous discharge of carbon nanotubes. In such a case, the source of production material is a source of carbon. However, the invention encompasses production materials comprising any of Ti, Zn, B, N, C and mixtures thereof. In such a case, the production material precursor may be a carbon nanotube aerogel. However, the invention encompasses any production material precursor including aerogels, fibrous networks, powders or porous structures. The invention is discussed hereinbelow in the context of the continuous discharge of carbon nanotubes but the principles may readily be applied to the continuous production of a range of one-dimensional nanomaterials such as nanotubes, nanorods and nanowires as applicable. Both the power density and catalyst injection problems can be resolved if a different method is used to deliver thermal energy to the synthesis gasses that either reduces or eliminates the need for heated walls. Options for delivery of thermal energy to the synthesis gasses at a point spaced from the walls include the use of radio-frequency plasmas, internally generating fuel rods and sheathed heating elements. Of those, the simplest and most scalable technique which can also provide isothermal reactors, is by sheathing heating elements away from the process gas. The element can then be placed within the reactor space and provide high power density to a local area. With all the thermal energy having to pass through the sheath and into the incoming gas stream, the energy efficiency is also improved. The invention is characterised by the provision of a heat source within the flow through volume spaced apart from the reactor wall. The heat source may be a single source unit effective at a single location within the flow volume, or comprise a plurality of heat source units effective at a corresponding plurality of locations within the flow volume. For example, the heat source may comprise a plurality of sheathed heating elements at a corresponding plurality of locations within the flow volume. The heat source within the flow through volume spaced apart from the reactor wall (which term includes plural heat source units as above described) is as noted preferably such as to provide a major part of the necessary thermal energy to raise the temperature of the reaction zone. Thus, the heat source within the flow through volume spaced apart from the reactor wall does not merely provide a secondary source of heat for a secondary purpose, for example to manipulate catalyst temperature or to provide a particular thermal profile, but provides the major part, and preferably substantially all and more preferably all of the necessary thermal energy to modify the temperature of the reaction zone of the flow-through reactor to that necessary to sustain and optimize the reaction to generate particulate metal catalyst and to produce carbon nanotubes. For example by way of definition of a heat source that provides at least a major part of the necessary thermal energy to raise the temperature of the reaction zone of the flow-through reactor to one that is sufficient to generate particulate metal catalyst and to produce carbon nanotube aerogel, the heat source is operable to create a temperature in the reaction zone that is greater in proximity to the source than it is at the reactor wall, and/ or is operable to raise the temperature of the reaction zone to one that is sufficient along at least a major part of the length of the reaction zone. By analogy, in accordance with the invention in a second aspect, an apparatus for the production of a material agglomerate, and for example carbon nanotubes, comprises a temperature-controlled flow-through reactor operable to perform the method of the first aspect, and preferred features and technical advantages of each aspect will be understood by analogy from the description herein. For example, in accordance with the invention in a second aspect, an apparatus for the production of a material agglomerate, and for example an apparatus for the production of carbon nanotubes comprises: a temperature-controlled flow-through reactor having a flow-through volume defined by a reactor wall, and provided with a source of thermal energy operable to control the temperature of a reaction zone therein; a supply of metal catalyst or metal catalyst precursor, for example configured to be operable in use to introduce a flow of metal catalyst or metal catalyst precursor into the temperature-controlled flow-through reactor; a supply of a source of production material , wherein the source comprises a source of production material selected from the group comprising at least one of Ti, Zn, B, N, C, for example configured to be operable in use to introduce a flow of a source of production material into the temperature-controlled flow-through reactor; a reaction zone, wherein the source of thermal energy comprises a heat source within the flow through volume spaced apart from the reactor wall, said heat source providing at least a major part of the thermal energy to raise the temperature of materials in the reaction zone of the flow-through reactor, and preferably being the sole source of such thermal energy to the reaction zone, and being configured to be operable to expose the metal catalyst or metal catalyst precursor and source of production material to a temperature in the reaction zone of the flow-through reactor that is sufficient to generate particulate metal catalyst and to produce a production material precursor which may be a carbon nanotube aerogel; and a discharge outlet of the temperature-controlled flow-through reactor, through which the production material precursor may be displaced as a continuous discharge for collection. Preferably, the supply of metal catalyst or metal catalyst precursor is configured to be operable in use to introduce a flow of metal catalyst or metal catalyst precursor into the temperature-controlled flow-through reactor at a location downstream of the said heat source within the flow through volume spaced apart from the reactor wall. In particular preferred embodiments, the source of thermal energy to a reaction zone defined in the flow through reactor volume comprises and preferably is provided only by one or more thermal elements within the flow through reactor volume spaced apart from the reactor wall and extending along a longitudinal portion of the flow through reactor volume, and the supply of metal catalyst or metal catalyst precursor is configured to be operable in use to introduce the same into the temperature- controlled flow-through reactor at a location downstream thereof. The heat source is for example a radiative heat source, that is to say, a heat source that is configured to provide thermal energy to materials in the flow-through reactor volume via a radiative heat transfer mechanism. A radiative heat source may for example, comprise a sheathed radiative heat source, for example comprising one or more sheathed heating elements. Additionally or alternatively the heat source may comprise a conductive or convective heat source, that is to say, a heat source that is configured to provide thermal energy to materials in the flow-through reactor volume via a heat conductive and/ or convective heat transfer mechanism. In particularly preferred embodiments, a thermal medium may be provided as discussed below, and the heat transfer mechanism is at least in part and preferably in substantial part by conduction from a radiative heat source via the thermal medium. Thus, in familiar manner in operation, metal catalyst or metal catalyst precursor and production material such as carbon are introduced via an inlet or inlets of a flow- through volume upstream of the reaction zone of the flow-through volume where aerogel is formed, to a discharge outlet of the flow-through volume for collection. An apparatus is provided for the synthesis of a material agglomerate such as a carbon nanotube (CNT) aerogel in the gas phase via a continuous floating catalyst chemical vapour deposition (FC-CVD) process and the generation of a continuous discharge of carbon nanotube aerogel in generally familiar manner. The apparatus is distinctly characterised by the provision of a heat source within the flow through volume spaced apart from the reactor wall. The reactor walls do not need to be, and in preferred embodiments are not, a source of heat. As with the method, in particular embodiments, discussed by way of example, the apparatus is applied to the generation of a continuous discharge of carbon nanotubes but the principles may readily be applied to the continuous production of a range of one-dimensional nanomaterials such as nanotubes, nanorods and nanowires as applicable. Thus, as discussed hereinabove in relation to the proves of the first aspect, both the power density and catalyst injection problems can be resolved by use of means to deliver thermal energy to the synthesis gasses that either reduce or eliminate the need for heated walls, achieved by the provision of a heat source within the flow through volume spaced apart from the reactor wall. The heat source may be a single source unit effective at a single location within the flow volume, or comprise a plurality of heat source units effective at a corresponding plurality of locations within the flow volume. For example, the heat source may comprise a plurality of sheathed heating elements at a corresponding plurality of locations within the flow volume. The heat source within the flow through volume spaced apart from the reactor wall (which term includes plural heat source units as above described) is preferably such as to provide a major part of the necessary thermal energy to raise the temperature of the reaction zone of the flow-through reactor to one that is sufficient to generate particulate metal catalyst and to produce carbon nanotube aerogel. Thus, the heat source within the flow through volume spaced apart from the reactor wall does not merely provide a secondary source of heat for a secondary purpose, for example to manipulate catalyst temperature or to provide a particular thermal profile, but provides the major part, and preferably substantially all and more preferably all of the necessary thermal energy to modify the temperature of the reaction zone of the flow-through reactor to that necessary to sustain and optimize the reaction to generate particulate metal catalyst and to produce carbon nanotubes. For example by way of definition of a heat source that provides at least a major part of the necessary thermal energy to raise the temperature of the reaction zone of the flow-through reactor to one that is sufficient to generate particulate metal catalyst and to produce carbon nanotube aerogel, the heat source is operable to create a temperature in the reaction zone that is greater in proximity to the source than it is at the reactor wall, and/ or is operable to raise the temperature of the reaction zone to one that is sufficient along at least a major part of the length of the reaction zone. The method of the first aspect is thus applied to and the apparatus of the second aspect thus comprises a temperature-controlled flow-through reactor having a flow- through volume defined by a reactor wall, and provided with a source of thermal energy operable to control the temperature of a reaction zone therein, the invention being characterised by the use of source of thermal energy comprises a heat source within the flow through volume spaced apart from the reactor wall to contribute a major part of the thermal energy, preferably such as to dispense substantially or entirely with the need for hot-walled reactor configurations. The design of flow-through reactor may nevertheless be based on existing principles. For example, a typical flow-through reactor may have an inlet end, a discharge outlet end, and an elongate portion therebetween including the reactor volume. The elongate portion or at least a major part thereof is for example tubular, being defined by a tubular wall, the reactor constituting a tube reactor. The tubular elongate portion may be of constant cross-section. The tubular elongate portion may be cylindrical. The tubular elongate portion may alternatively have polygonal cross-section and is for example rectangular. The flow-through reactor thus comprises an elongate flow-through volume defined by a reactor wall, through which reaction products may be caused to flow from an inlet end to a discharge outlet end, and defining a reaction volume therein. The reactor wall then conveniently comprises, at least for a major part of the length, a tubular wall, and for example a polygonal or cylindrical tubular wall defining an elongate flow direction. The invention is characterised by the provision of a heat source within the flow- through volume spaced apart from the reactor wall. The heat source may be a single source unit effective at a single location within the flow volume, or comprise a plurality of heat source units effective at a corresponding plurality of locations within the flow volume. In the case of an elongate furnace defining an elongate flow direction as above the heat source may comprise at least one elongate heat source unit extending parallel to the elongate flow direction. In some embodiments, the elongate heat source unit extends parallel to the elongate flow direction for at least a major part of the distance from the inlet end to and preferably through the reaction volume. In some embodiments, the heat source may comprise a plurality of elongate heat source units extending parallel to each other in the elongate flow direction. The elongate heat source units may each comprise comprises one or more sheathed heating elements. The invention is distinctly characterised by the provision of a heat source within the flow through volume spaced apart from the reactor wall. The reactor wall does not need to be, and in preferred embodiments is not, a source of heat. Thus the reactor wall does not need to be, and in preferred embodiments is not, fabricated from a refractory ceramic. For example, the reactor wall is metal. The flow-through reactor may be open, in the sense that the gases therein flow through an open volume defined by the reactor wall from an inlet end to an outlet end. Alternatively, at least a part of the flow-through reactor volume, and for example at least a substantial part of the reaction zone therein defined, may comprise a solid particle thermal medium bed to improve thermal transfer therein. Preferably the solid particle thermal medium bed comprises ceramic or ceramic coated particles. Suitable refractory ceramic materials for the particles or particle coatings will readily suggest themselves. For example the solid particle thermal medium bed comprises Al2O3 particles. The carrier gas used to synthesise CNTs is usually hydrogen (H₂), a symmetrical diatomic gas with only excited transitions emitting infra-red (IR) radiation. This results almost none of the thermal transfer emitted from the surface of tube in a conventional tube furnace to be absorbed by the gas leading to most of the energy transferred through convection. Forced convective heat transfer is limited to the flow rate of the gas through the tube. A bed of solid particle within streams is used to improve thermal transfer. The solid particles improve the conductive transfer by the providing increased number of contact points, a tortuous path for the gas and effective thermal conductive of the channel where the packing is located. For a thermal medium to operate with CNT synthesis, one has to select solid particles that are chemically inert to the process gases. This can be readily achieved with high purity non-porous alumina (99+ % Al2O3) particles. Chemically Al2O3 is not etched by H2 and at high temperatures CH4 is not catalysed to deposit graphitic layers on it surfaces for the diluted quantity at typical conditions run in FC-CVD which is readily observed in the tubes post synthesis. The key to the process of the invention is the delivery of the necessary process thermal energy from a point spaced from the walls in a manner which allows to reduce or dispense with the need for thermal heating from the walls. The materials used in and process parameters for the reaction are otherwise as would be familiar. For example, in a typical embodiment, the metal catalyst or metal catalyst precursor may be a nanoparticulate metal catalyst. Preferably the nanoparticles of the nanoparticulate metal catalyst have a mean diameter (eg a number, volume or surface mean diameter) in the range 1 to 50 nm (preferably 1 to 10 nm). Preferably 80% or more of the particles of the nanoparticulate metal catalyst have a diameter of less than 30 nm. Particularly preferably 80% or more of the particles of the nanoparticulate metal catalyst have a diameter of less than 12 nm. Typically the metal catalyst is one or more of the group consisting of alkali metals, transition metals, rare earth elements (eg lanthanides) and actinides. Preferably the metal catalyst is one or more of the group consisting of transition metals, rare earth elements (eg lanthanides) and actinides. Preferably the metal catalyst is at least one of the group consisting of Fe, Ru, Co, W, Cr, Mo, Rh, Ir, Os, Ni, Pd, Pt, Ru, Y, La, Ce, Mn, Pr, Nd, Tb, Dy, Ho, Er, Lu, Hf, Li and Gd. Most preferably the metal catalyst is iron. The metal catalyst precursor may be a metal complex or organometallic metal compound. Examples include iron pentacarbonyl, ferrocene or a ferrocenyl derivative (eg ferrocenyl sulphide). Preferably the metal catalyst precursor is sulphur-containing. A metal catalyst precursor which is sulphur-containing may promote carbon nanotube growth. Preferably the metal catalyst precursor is a sulphur-containing organometallic. Particularly preferably the metal catalyst precursor is a sulphur-containing iron organometallic. More preferably the metal catalyst precursor is a sulphur-containing ferrocenyl derivative. Yet more preferably the metal catalyst precursor is mono- (methylthio) ferrocene or bis- (methylthio) ferrocene. The metal catalyst or metal catalyst precursor may be introduced in step (b) together with a sulphur-containing additive. The sulphur-containing additive may promote carbon nanotube growth. The sulphur-containing additive may be thiophene, iron sulphide, a sulphur- containing ferrocenyl derivative (eg ferrocenyl sulphide), hydrogen sulphide or carbon disulphide. In a preferred embodiment, the sulphur- containing additive is thiophene or carbon disulphide. Particularly preferably the sulphur-containing additive is thiophene. In a preferred embodiment, the metal catalyst precursor is ferrocene optionally together with a sulphur-containing additive (preferably thiophene or carbon disulphide). The metal catalyst or metal catalyst precursor introduced in step (b) may be in a gaseous, liquid or solid form. The metal catalyst or metal catalyst precursor may be introduced in step (a) with a non-metal catalyst modifier or precursor thereof. The non-metal catalyst modifier may be chalcogen-containing (eg sulphur-containing). The generation of particulate metal catalyst may be initiated in step (d) by thermal decomposition or dissociation of the metal catalyst or metal catalyst precursor into metal species (eg atoms, radicals or ions). The generation of particulate metal catalyst in step (d) may comprise nucleation of the metal species into nucleated metal species (eg clusters). The generation of particulate metal catalyst may comprise growth of the nucleated metal species into the particulate metal catalyst. The metal catalyst or metal catalyst precursor may be introduced (eg injected) in step (b) in a linear, axial, vortical, helical, laminar or turbulent flow path. The metal catalyst or metal catalyst precursor may be introduced at a plurality of locations. In step (b), the metal catalyst or metal catalyst precursor may be introduced axially or radially into the temperature-controlled flow-through reactor. The metal catalyst or metal catalyst precursor may be introduced axially through a probe or injector. The metal catalyst or metal catalyst precursor may be in a mixture with a carrier gas. The carrier gas is typically one or more of nitrogen, argon, helium or hydrogen. The mass flow of the metal catalyst or metal catalyst precursor in admixture with the carrier gas is generally in the range 10 to 30 ppm. The metal catalyst or metal catalyst precursor may be introduced in a mixture with a carrier gas. The carrier gas is typically one or more of nitrogen, argon, helium or hydrogen. In such cases as described hereinabove for preferred modes, inlet sites, flows and flow paths, mixtures and compositions etc, the supply of metal catalyst or metal catalyst precursor is configured to be operable in use to introduce a flow of metal catalyst or metal catalyst precursor in such manner, and for example at such inlet sites, with such flows and flow paths, comprising such mixtures and compositions etc. Similarly from known systems for example, in a typical embodiment, the source of carbon may be methane optionally (but preferably) in the presence of an optionally substituted and/or optionally hydroxylated aromatic or aliphatic, acyclic or cyclic hydrocarbon (eg alkyne, alkane or alkene) which is optionally interrupted by one or more heteroatoms (eg oxygen). The source of carbon may be a C1-6 -hydrocarbon such as methane, ethylene or acetylene. The source of carbon may be an alcohol such as ethanol or butanol. The source of carbon may be an aromatic hydrocarbon such as benzene or toluene. Before step (c), the source of carbon may be heated. Before step (c), the source of carbon may be subjected to radiative heat transfer by a source of infrared, visible, ultraviolet or x-ray energy. In step (c) the source of carbon may be introduced (eg injected) in a linear, axial, vortical, helical, laminar or turbulent flow path. In step (c), the source of carbon may be introduced axially or radially into the temperature-controlled flow-through reactor. The source of carbon may be introduced axially through a probe or injector. The source of carbon may be introduced at a plurality of locations. In a preferred embodiment, the source of carbon is methane optionally in the presence of propane or acetylene. The source of carbon may be introduced in a mixture with a carrier gas. The carrier gas is typically one or more of nitrogen, argon, helium or hydrogen. In such cases as described hereinabove for preferred modes, inlet sites, flows and flow paths, mixtures and compositions etc, the supply of carbon is configured to be operable in use to introduce a flow of carbon source material in such manner, and for example at such inlet sites, with such flows and flow paths, comprising such mixtures and compositions etc. Brief^Description^of^Drawings The invention will now be described by way of example only with reference to figures 1 to 4 of the accompanying drawings. Figure 1 shows (a) Diagram of a prior art FC-CVD setup; (b) Design where catalyst delivery is optimised for the standard horizontal furnace; and (c) modification of the same to provide an internally heated FC-CVD system according to the principles of the invention. Figure 2 shows the variation of catalyst particle number concentration and mean particle diameter as the catalyst is injected into the synthesis stream. Figure 3 shows production data. Figure 4 develops alternative furnace concepts embodying the principles of the invention. Detailed^Description^ Illustrative examples of a new FC-CVD reactor platform and of the process of operation thereof that embodies principles of the invention, are described hereinbelow, together with example operation parameters and results. The principles of the invention are shown to offer the potential for higher density of reaction, and has an inherently high carbon conversion efficiency. The particular example is applied to the production of CNT aerogels, but the principle of the invention may be applied to any materials and nanostructures encompassed within the scope of the invention as defined by the claims appended hereto. Figure 1 shows the general principle of the invention, as it might be applied as a modification to a prior art FC-CVD setup for the continuous generation of CNT aerogels. Figure 1 shows: (a) Diagram of a prior art FC-CVD setup; (b) Design where catalyst delivery is optimised for the standard horizontal furnace; and (c) modification of the same to provide an internally heated FC-CVD system in accordance with an embodiment of the invention. Figures 1a and b showcase the furnace setups found in the FC-CVD literature with the different methods of catalyst and precursor injection. Both co-flow (standard) and deep-injection FC-CVD utilise an outer electric furnace to provide the thermal energy. Figure 1c depicts the schematic of the internally heated FC-CVD with a sheathed element and a counterflow injection line. This simple embodiment was used to illustrate the concept in accordance with the method described in detail below. CNT synthesis In an example process illustrative of principles of the invention, CNTs were continuously synthesised using a vertical reactor following the principles illustrated in Figure 1c. The example reactor contained an external electrical resistance furnace (Carbolite, STF 15/450) with an alumina tube having an inner diameter of 80 mm and a length of 1200 mm. CH₄ was used as the hydrocarbon precursor (190 sccm) with hydrogen (H2, 2.00 L/min) as the main carrier gas. Ferrocene (150 sccm) and thiophene (80 sccm) were used as the catalyst and promoter precursors respectively with argon used as the carrier gas. The total flow rate in the system was 3.42 L/min. All gases were delivered using mass flow controllers. A custom evaporation unit was used to evaporate ferrocene at 90 and 100℃ which was maintained throughout the synthesis, thiophene was delivered through a bubbler held at 0°C in an ice bath. The moles of hydrocarbon precursor and Fe:S during an individual run were kept constant (Fe:S, 1:82, C:Fe, 7556:1 and C:FeS, 91:1). A packed bed (Alumina, Al₂O₃, Boud Mineral, nominal size of 1.2 mm, 99.5% purity) was placed into the furnace with a silicon carbide (SiC) heating element (heated length: 200 mm, total length 450 mm, OD = 13 mm), sheathed in a ceramic tube (Al2O3, ID = 26 mm, OD = 30 mm, Almath crucibles). The external furnace was in an example operational mode set to 1250°C with the packed bed temperature set at 1350°C. The packed bed temperature was monitored and controlled using a sheathed S-type thermocouple and the power to the internal element was varied (600 - 900 W) using a constant voltage, variable power transformer (RS). A gas exchange valve was used to dilute the synthesis flow to below the lower explosion limit of H2 and the material was collected in a custom-built chamber using either a bobbin (5 m/min, 130 °C) or on a rod (350 °C) that was manually operated. The catalyst particles were delivered at both co and counterflow injection points. For the co-flow experiments, catalyst particles were injected with the delivery line exposed to temperatures exceeding 1350°C using a narrow catalyst injector (ID = 1 mm, length = 450 mm) with an additional argon flow (1 L/min). After 5 minutes of continuous delivery, however, the line would clog. The counterflow delivery line contained a larger Al₂O₃ delivery tube (ID = 8 mm, length = 350 mm) that was mounted in the collection chamber. the catalyst particles were delivered to a temperature zone held at ~ 900°C. A supplementary, argon stream (1 L/min) was also used to decrease the residence time of the catalyst within the delivery tube and to prevent clogging. Fluid dynamics simulations Reference is made to the table of equations 1 to 10 below. A steady-state numerical simulation of the reactor was performed solving mass, momentum and energy equations shown in equations 1-4, using COMSOL Multiphysics v6.0. The thermal and velocity transport was solved using the same numerical technique, with the equations for solution shown in 5-10. 1 ^(^^) = ^ 2 ⁽^^^⁾^ = ^⁽−^^ + ^⁾ + ^^

10 ^ ^_^^^ = − (^^ + ^^) ^ Where ρ and ρ_f (kg/m³) are the fluid’s density, u (m/s) is the fluid’s velocity field, p is the fluid’s pressure (kg/m s²), μ is the viscosity of the gas (Pa s), C_p,f (J/kgK) is the heat capacity of the gas, k (W/m K) is the thermal conductivity of the gas, T (K) is the gas temperature, g (m/s²) is the force of gravity. The energy equation for the porous domain (eqn.6) was adjusted to accommodate the effective thermal conductivity (keff, (W/mK)) which encapsulated the effect the solid particle thermal conductivity (k_s ^θ (W/mK) has on the fluid’s thermal conductivity (kf^{^}). The porosity (^ = 0.4) was uniform across the bed. κ is the permeability which was evaluated using the Karman- ^ ^{^} Cozeny relationship ( ^{^} _{^ ^} ^^^ _(^^^) ^{^}) where d_p is the particle diameter (1.2 mm). The temperature distributions were achieved through radiative transfer to the unit and confirmed by experimental temperature measurements along the reactor axis. The models simulated radiative transfer between the external heating elements and the outer tube as well as the internal heating element. The view factors in the model were calculated using the Hemicube method and a correction was accounted for when running 2-D simulations to 3-D counterparts. The porous domain was simulated to have a uniform porosity (0.4) and the gas-solid mixture was in a local thermal equilibrium (LTE) solving an effective properties energy equation (eq. 5) could be used to solve for the temperature distribution. The simulated patterns then provided information on the flow dynamics of the incoming catalyst allowing us to realise the potential flaws of each catalyst delivery setup.

in the reactor To measure the particle size distribution and number concentration of the catalysts, a scanning mobility particle sizer was used (SMPS, TSI instruments, model 3080 classifier, 1.5 L/min sample rate). Prior to entering the sampler an ejector dilutor was connected upstream to the unit and was provided a continuous supply of N2 (5 L/min), diluting the sample flow (0.04 L/min). The longest residence time of the sampled gas within the sampling tube (1.78 s) was determined to be short enough to prevent coagulation. Thermal conductivity of the packed bed The thermal conductivity of the packed bed was measured using helium as the gas (He, k_He (20°C) = 0.17 W/mK) and performed by inserting 2 thermocouples (K-type) at set radial locations (r = 32.5 mm and r = 17 mm) from the internal Al3O3 sheath (r = 15mm) and the inner wall of the ceramic tube. The axial location of the thermocouple was varied between the hot-zone section of the internal element (200 mm) that was set to provide a constant power (600 W). The analysis of the thermal conductivity is shown in supplementary information 3. The low flow-rates used for synthesis provided the assumption of a quiescent bed, and it was found that the temperature of the bed followed a power-law, similar to those found using other packed beds. Characterisation of CNTs and CNT material The CNTs were characterised using Raman (Horiba XploRa PLUS, 638 nm laser, 50× objective, 1200 grating, 25% laser power) to quantify the G/D ratio by calculating the ratio of peak intensity which were averaged over 3 samples. Thermogravimetric analysis (TGA, Metler-Toledo TGA/DSC 2) was performed on produced samples using air (25 sccm, ramp rate = 5°C/min) quantifying the content of amorphous carbon, polydispersity of produced CNTs and the total residual content within the product. Scanning electron microscopy and high-resolution tunnelling electron microscopy (SEM, Tescan Mira 3 FEG-SEM, 5kV and HRTEM, FEI Talos, 200 kV, 200 X) were used to qualitatively asses presence of CNTs and to quantify the CNT diameter and wall number respectively. For HRTEM, the samples were prepared by mechanically agitating the material for 30 minutes with a holey carbon grid (300 mesh) inside the material sample box. Production values of CNTs were measured by weighing the retrieved mass from the bobbin or the collection rod on a microgram mass balance (Satorius, SE2-F) and corrected for the total carbon mass by multiplying through the residual content and amorphous carbon content. CNT material was rolled into a wire shape and the samples were weighed using a microbalance (Satorius, SE2-F). The weight was then divided by the length of the samples to provide the linear density of material in tex (g/km). The resistance of the material was measured using a custom-build 4 point set-up monitoring the resistance with a milliohm meter (Aim-TTi BS407). The specific electrical conductivity (Sm²/kg) was calculated by first measuring the linear resistance (proportional to the linear conductance) and normalising by the linear density. An average of 3 samples was taken as the reported value. Tensile tests were performed using and Instron mechanical tester (5500R) with a sample length of 50 mm. The initial gauge length was set at 20 mm with an extension rate of 1 mm/s and a sample pretension of 0.1 N. Further, aluminium foils were placed side-by-side on the sample and glued to to prevent slippage in during the test. Three runs were performed and the strain at failure was averaged and fibre tenacity (N/tex) calculated by normalising with the sample’s linear density. Result and Discussion To enhance the thermal transfer between the sheath and the incoming H2 carrier gas, a packed bed of Al2O3 particles was chosen due to the high thermal conductivity (5 W/mK at 1300°C, kbed:kH2 = 30) and inert properties. The radial thermal conductivity of the packed bed in He was 4.4 ± 0.5 W/mK at 1000 °C. The external furnace was used to solely balance the pre-heaters power output in the location of the element. For low CH₄ precursor feed (10 – 20%) during the synthesis conditions, shown in the supplementary table 1, there was no observed fouling on the surface of the particles. To express the longevity of this measurement, two pressure transducers were mounted on the inlet and exhaust of the reactor. For continuous synthesis (2 hours) there was a negligible pressure increase in the bed (< 3000 Pa). Even if the Al2O3 particles got coated with graphitic layer, the autocatalytic reaction with low MW hydrocarbons is slow and with the H₂ able to react with surface carbon turning it back into CH₄. The developed reactor showed the possibility to inject the catalyst and hydrocarbon precursors separately whilst producing material that had similar properties to that found of unprocessed CNT aerogel. The material was synthesised using both co-flow and counter-flow catalyst injection points. With the co-flow catalyst injection, it was not possible to synthesise material continuously due to clogging issues. In Figure 2, the variation of catalyst particle number concentration and mean particle diameter as the catalyst is injected into the synthesis stream (a) was compared with the fluid dynamics of the counter-flow injection (c) and the simulated profile of the co-flow delivery (b) was also investigated for synthesis. Of the two attempted injection points co-flow appeared the best from simulation results (figure 2a), however, practically this location was limited due to clogging. Another approach was to deliver the catalyst counter-flow to the main synthesis flow, which resulted in most (90%) of the catalyst number concentration not entering the furnace, however, provided a sufficient mass ( > 160 mg/m³)¹⁰ to synthesise the aerogel. The computational simulations (figures 2a, b) highlighted the non-optimum delivery with eddy formations during the co-flow (figure 2b) and flow predominantly ejecting as it entered from counter-flow. SMPS results, summarised in figure 2c, showed that as the catalyst precursors were injected into the synthesis stream, they rapidly nucleated and coagulated forming large particles (d_p = 27 nm, N_tot = 4.5 × 10⁷ #/cm³). The particles then entered the temperature gradient of the reactor (1100°C) and started to evaporate, forming a bi- modal distribution (T = 1135 °C, d_p,av1 = 20 nm, d_p,av2 = 38 nm; T = 1193 °C, d_p,av1 = 18 nm, dp,av2 = 25 nm). Once the particles entered the hot-zone of the furnace, they had completely evaporated at the set-point temperature (1200 – 1250°C). The observation of particle evaporation was similar to the particle dynamics found in previous literature results. The bi-modal distribution was attributed to the vortex formation as the injected flow entered the hot-zone, increasing the residence the collision time between the particles, during the evaporation stage. To investigate this laminar counter jet effect figure 2b, showed the simulated flow profile as the argon jet (1 L/min) entered the furnace (Tentry = 909°C). Visually as the aerogel was collected, it swirled inside the inner synthesis tube, colliding with the catalyst injector or directly ejected onto the bobbin. Further, a significant amount (d_p,_av = 33 nm, N_tot = 1.8 × 10⁸ # /cm³) catalyst particle, shown in figure 2c, exhausted without interacting with the hydrocarbon gas. Most of the catalyst lost was due to migration of fluid away from the synthesis tube, however, ~ 1 – 10% of the total concentration was able to enter the hot zone and result in synthesis of material despite the large number of particles lost to the exhaust. Due to the limitations of using ceramic walled reactors, a precise injection of particle was not possible with this setup though is the subject of on-going work. Figure 3 shows production data. Specifically: Production (a) of CNTs retrieved from improving the thermal transfer to CH4 and H2. SEM ((b.i, b.ii) and TEM (iii-v) images of the material produced using the two different catalyst delivery methods (b.i, b.ii). The TEMs of the counter-flow product showed a SWCNT (b.iii), DWCNT (b.iv) and MWCNT (b.v). TGA (c) and Raman spectra (d) of the counter-flow samples were used to finalise characterisation of the material. We found that increasing the heat transfer (h_int ~ 5 – 7 W/m²K, k_bed ~ 4 – 5 W/mK) to CH4 and H2 increased the production density (0.07 ± 0.01 to 0.23 ± 0.2 kg/h/m³) and carbon conversion (from 14 to 36%), summarised in figure 3a. This result shows promise that the re-distribution of thermal energy within the synthesis zone of CNTs will increase production density and provide a scalable method of production. Comparing the results with previous literature studies, we found that we had the highest conversion (36%) in the academic literature using CH4 as the precursor gas in FC-CVD synthesis. Figure 3b shows the SEM and TEM images of the product. From the TEM results, we saw a distribution of CNT diameters and walls (1.68 – 3.70 nm, 1 – 3 walls). SEM images showed the bundled CNTs collected from the reactor with some CNTs forming an ellipse, suggesting they were shorter than others. The TGA results of the counter- flow catalyst injection (figure 3c) showed a low amorphous carbon content (0 ± 1%, mass loss Telut. < 400°C)) and a low quantity of non-carbon residue (11 – 15%). The sample had a distribution of CNTs predominantly containing SWCNTs (56 – 63% of carbon in sample, Telut. = 500 – 550°C) with some MWCNTs (26 – 38%, Telut. = 680 – 700 °C). The presence of SWCNTs was further confirmed by the Raman spectroscopy (figure 3b) exhibiting radial breathing mode (RBM) peaks (100 – 200 cm^-1). The apparent catalyst efficiency calculated from the mass of the residue from the packed- bed synthesis remained similar (~ 0.1% ± 0.03) to that found in other FC-CVD process, explained by both the losses to the walls (visual deposition of Fe2O3 post synthesis) and losses and exiting through the top of the furnaces in large. The co-flow catalyst delivery line orientation produced a large amorphous fraction from the synthesis process (35%) and high variability in the samples residual content (15 – 40%). The variability was caused by the build-up inside the delivery line causing non-uniform injection of Fe. As the process did not provide a continuous synthesis (20 minutes), it was not possible to obtain a carbon mass conversion for the process. The power delivered to both the furnace and the internal element units were monitored using a current clamp (RS Pro, ICA 31) and a voltmeter (RS Pro, IDM 67). The power loading of the internal heating element was varied until the desired temperature in the bed was reached (1220+ °C). When monitoring the process; the power of the process remained constants (4000 ± 100W). The reduction in power consumption by the external furnace was equal to the amount of power delivered by the internal element, displaying its effectiveness (P_int = 900 ± 2 W (3.5 × 10⁷ W/m³), P_ext 2900 ± 150 W (2.19 × 10⁶ W/m³), T_{bed, exhaust} = 1350°C, T_furnace = 1250 °C). When integrating power across the element’s volumes, the total power of the external furnace exceeded the internal, however, when we look locally at the exit temperature of the fluid from the packed bed, most of the power (55 – 80%, H₂ = 1 – 2 L/min) was delivered by the internal element. Figure 4 develops alternative furnace concepts embodying the principles of the invention based on the above, using an individual element surrounded by thermal insulation (a), improving heat flux to the gases (b) and a schematic comparing the two arrangements showing required heat flux required for high production density (c, d). In particular, we see that if the external furnace was removed, and replaced with insulation, or with another repeated unit, the energy can be used solely to preheat the H₂ and CH₄. This process could contain the gases in a metal walled container with insulation. Such an arrangement is visualised in figure 4a and 4d in concept with the maximum depth of insulation is shown. Utilising the above arrangement can improve the power density (W/m³) of the reactor and pre-heat the incoming H₂ carrier gas. This enables one to increase the volume of a production unit without a significant increase in the furnace’s footprint or required heat flux. It is conceivable that a single reactor unit may contain several SiC elements wrapped in an Al2O3 tube and provide a sufficient power to produce t/h of CNTs. Figure 4 displays a conceptual model to implement this idea. For scaled production (100 – 1000 kg/h/m³) of material the power density (10⁶ – 10⁷ W/m³) required solely to heat the carrier gas (H2) would result in surface temperatures exceed the melting points of all known materials (5.6 × 10³ – 4.4 × 10⁴ ℃). It is also unsurprising that FC-CVD synthesis is limited to ~ 1 – 5 kg/h/m³ of product with the current synthesis temperature (1300 – 1400 °C). These values are greatly influenced by the dilution factor of methane within the gas stream (10% CH₄) and the overall conversion (80%). To begin to match the production density of CNT powders (100 kg/h/m³), a separate strategy could involve multiple individual heating units which would populate a reactor. Using an energy balance on the surface of a sheathed element maintained at a normal temperature (1400 °C), we see that to provide sufficient power (10⁷ W/m³) to reach scaled production (1000 kg/h/m³) would require ~ 415 individual units in a unit volume. Other power management strategies could also provide the breakthrough into the mass production of CNTs including the use of plasmas. Conclusion FC-CVD requires a different approach to synthesis that can reuslt in a scalable process providing ultra-long CNTs with high tube crystallinity (G/D ratio) and multiple scalable forms of material, however, the method requires a scalable reactor platform that can deliver a scalable route. The power density and catalyst utilisation must increase to imrpove production density and match the that of fluidised bed CVD CNT synthesis (10² kg/h/m³). We attempted to address these challenges by providing a synthesis method which improved the power density, and adapts the thermal energy location. The new, internally heated FC-CVD method produced CNTs using a pre-heating unit to predominantly provide the energy to the incoming fluid. The setup had an inherently high carbon conversion (36 ± 4%), moderate production density (0.23 ± 0.2 kg/h/m³) with inherently high carbon crystallinity (IG:ID 14 – 20 ± 1) and low residual content (11 – 15 %). This design is the first to predominantly provide the thermal energy from an internal heating element and will lead to scalable designs that have the potential to maximise production density of CNT aerogel. Embodiments of the invention described hereinabove present a new approach to FC- CVD developing a new reactor platform that achieves higher density of reaction, and has an inherently high carbon conversion efficiency. It was achieved through improving the thermal transfer and changing the thermal input to the furnace. These advancements enable new synthesis concepts eliminating the need for ceramic vessels and improve methods for optimized catalyst injection points. Further, this advancement can provide solutions to addressing large heat flux issues found in scale-up that are currently unsolved. In particular, embodiments of the invention described hereinabove may seek solely to heat the reaction body using an internal heating source with use of a thermal media to distribute the thermal energy to the carrier gas (H₂ which is IR inactive) as well as to separate the delivery of the precursors from the carrier gas and hydrocarbon input. The differences in Objectives result in several differences between the patents. Key features consequent on those objectives may include the following. Multiple geometric arrangements (perpendicular, coaxial, parallel) of the thermal source can be utilised. The reactor boy may have any geometric cross section not restricted to coaxial (cylindrical) only. No external heating required using our invention as it solely uses the heating from the internal heating elements with the external heating elements to be replaced with insulation. The internal element doesn’t need to run along the length of the reactor as the invention seeks to change the temperature profile along reactor axis and not maintain its uniformity. This axial thermal gradient is useful in order to induce material formation. The invention may use a conductive thermal media to promote the heat transfer and distribute the thermal energy both radially and axially. In such an arrangement thermal transfer to materials in the rection volume is through conduction of energy from the radiative heat source via the conductive thermal media. This may be advantageous over synthesis performed solely using radiative thermal transfer. The invention seeks to concentrate the source of conductive thermal energy allowing the distribution to occur via conduction and radiation rather than a uniformly distributing the thermal energy using the internal heating body. This is a crucial addition which fundamentally seeks to distribute the energy through promotion of conduction and convection to the carrier gas which is IR inert. The invention facilitates the separate delivery of the catalyst precursors from the hydrocarbon and carrier gas. The separate delivery of the catalyst precursors from the hydrocarbon and carrier gas has improved benefits over the other potential materials. The thermal system may preferably deliver the precursor materials at higher temperatures. The thermal media illustrated in preferred embodiments may for example seek to deliver gases to temperatures in excess of 1000C.

Claims

CLAIMS 1. A process for the production of a material agglomerate comprising: (a) providing a temperature-controlled flow-through reactor having a flow-through volume defined by a reactor wall, and provided with a source of thermal energy operable to control the temperature of a reaction zone therein; (b) introducing a flow of metal catalyst or metal catalyst precursor into the temperature-controlled flow-through reactor; (c) introducing a flow of a source of production material into the temperature-controlled flow-through reactor, wherein the source comprises a source of production material selected from the group comprising at least one of Ti, Zn, B, N, C; (d) operating the source of thermal energy to expose the metal catalyst or metal catalyst precursor and source of production material to a temperature in a reaction zone of the flow-through reactor that is sufficient to generate particulate metal catalyst and to produce a production material precursor; (e) displacing the production material precursor as a continuous discharge through a discharge outlet of the temperature-controlled flow-through reactor; (f) collecting the continuous discharge; wherein the source of thermal energy comprises a heat source within the flow through volume spaced apart from the reactor wall, the said heat source providing at least a major part of the thermal energy to raise the temperature of materials in the reaction zone of the flow-through reactor.

2. The process of claim 1 or 2 wherein introducing a flow of metal catalyst or metal catalyst precursor into the temperature-controlled flow-through reactor is effected at a location downstream of the said heat source

3. The process of any preceding claim wherein at least a part of the flow-through reactor volume, and for example at least a substantial part of the reaction zone therein defined, comprises a solid particle thermal medium bed to improve thermal transfer therein.

4. The process of claim 3 wherein the heat transfer mechanism is by conduction from a radiative heat source via the thermal medium.

5. The process of claim 3 or 4 wherein the solid particle thermal medium bed comprises Al2O3 particles.

6. The process of any preceding claim wherein the heat source comprises a radiative heat source.

7. The process of claim 7 wherein the heat source comprises one or more sheathed heating elements.

8. The process of any preceding claim wherein the heat source comprises a radiative heat source and/ or a convective heat source.

9. The process of any preceding claim wherein the reactor wall is not a source of thermal energy.

10. The process of any preceding claim wherein the metal catalyst or metal catalyst precursor is a nanoparticulate metal catalyst.

11. The process of any preceding claim wherein the metal catalyst is at least one of the group consisting of Fe, Ru, Co, W, Cr, Mo, Rh, Ir, Os, Ni, Pd, Pt, Ru, Y, La, Ce, Mn, Pr, Nd, Tb, Dy, Ho, Er, Lu, Hf, Li and Gd.

12. The process of any preceding claim wherein the metal catalyst precursor is a metal complex or organometallic metal compound.

13. The process of any preceding claim wherein the metal catalyst precursor is sulphur-containing.

14. The process of any preceding claim wherein the metal catalyst or metal catalyst precursor and/ or the source of carbon is introduced in a mixture with a carrier gas comprising one or more of nitrogen, argon, helium or hydrogen.

15. The process of any preceding claim wherein the flow-through reactor has an inlet end, a discharge outlet end, and an elongate portion therebetween defining an elongate flow direction and including the reactor volume, the elongate portion or at least a major part thereof being defined by a tubular wall, the reactor constituting a tube reactor.

16. The process of claim 15 wherein the heat source comprises a plurality of elongate heat source units extending parallel to each other in the elongate flow direction.

17. The process of any preceding claim wherein the source of production material is a source of carbon.

18. The process of claim 17 wherein the production material precursor is a carbon nanotube aerogel.

19. An apparatus for the production of a material agglomerate comprising: a temperature-controlled flow-through reactor having a flow-through volume defined by a reactor wall, and provided with a source of thermal energy operable to control the temperature of a reaction zone therein; a supply of metal catalyst or metal catalyst precursor, for example configured to be operable in use to introduce a flow of metal catalyst or metal catalyst precursor into the temperature-controlled flow-through reactor; a supply of a source of production material , wherein the source comprises a source of production material selected from the group comprising at least one of Ti, Zn, B, N, C, for example configured to be operable in use to introduce a flow of a source of production material into the temperature-controlled flow- through reactor; a reaction zone, wherein the source of thermal energy comprises a heat source within the flow through volume spaced apart from the reactor wall, said heat source providing at least a major part of the thermal energy to raise the temperature of materials in the reaction zone of the flow-through reactor, and configured to be operable to expose the metal catalyst or metal catalyst precursor and source of production material to a temperature in the reaction zone of the flow-through reactor that is sufficient to generate particulate metal catalyst and to produce a production material precursor; and a discharge outlet of the temperature-controlled flow-through reactor, through which the production material precursor may be displaced as a continuous discharge for collection.

20. An apparatus according to claim 19 wherein the supply of metal catalyst or metal catalyst precursor is configured to be operable in use to introduce a flow of metal catalyst or metal catalyst precursor into the temperature-controlled flow-through reactor at a location downstream of the said heat source within the flow through volume.

21. An apparatus according to any one of claims 19 to 20 wherein at least a part of the flow-through reactor volume, and for example at least a substantial part of the reaction zone therein defined, comprises a solid particle thermal medium bed to improve thermal transfer therein.

22. An apparatus according to claim 21 wherein the solid particle thermal medium bed comprises Al2O3 particles.

23. An apparatus according to any one of claims 19 to 22 wherein the heat source comprises a radiative heat source.

24. An apparatus according to claim 23 wherein the heat source comprises one or more sheathed heating elements.

25. An apparatus according to any one of claims 19 to 24 wherein the heat source comprises a radiative heat source and/ or a convective heat source.

26. An apparatus according to any one of claims 19 to 25 wherein the reactor wall is not a source of thermal energy.

27. An apparatus according to any one of claims 19 to 26 wherein the flow- through reactor has an inlet end, a discharge outlet end, and an elongate portion therebetween defining an elongate flow direction and including the reactor volume, the elongate portion or at least a major part thereof being defined by a tubular wall, the reactor constituting a tube reactor.

28. An apparatus according to claim 27 wherein the heat source comprises a plurality of elongate heat source units extending parallel to each other in the elongate flow direction.

29. An apparatus for the production of a material agglomerate comprising a temperature-controlled flow-through reactor operable to perform the method of any one of claims 1 to 18.

30. An apparatus according to any one of claims 19 to 29 wherein the source of production material is a source of carbon and wherein the production material precursor is a carbon nanotube aerogel.