WO2016012365A1 - Process for modification of particles - Google Patents

Process for modification of particles Download PDF

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Publication number
WO2016012365A1
WO2016012365A1 PCT/EP2015/066409 EP2015066409W WO2016012365A1 WO 2016012365 A1 WO2016012365 A1 WO 2016012365A1 EP 2015066409 W EP2015066409 W EP 2015066409W WO 2016012365 A1 WO2016012365 A1 WO 2016012365A1
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Prior art keywords
particles
graphite
process according
gaseous stream
gas
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PCT/EP2015/066409
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French (fr)
Inventor
Andreas Mueller
Matthias Georg SCHWAB
Klaus Muellen
Hermann Sachdev
Original Assignee
Basf Se
MAX-PLANCK-Gesellschaft zur Förderung der Wissenschaften e.V.
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Publication of WO2016012365A1 publication Critical patent/WO2016012365A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
    • B01J8/005—Separating solid material from the gas/liquid stream
    • B01J8/006—Separating solid material from the gas/liquid stream by filtration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
    • B01J8/0015—Feeding of the particles in the reactor; Evacuation of the particles out of the reactor
    • B01J8/003—Feeding of the particles in the reactor; Evacuation of the particles out of the reactor in a downward flow
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
    • B01J8/005—Separating solid material from the gas/liquid stream
    • B01J8/0055—Separating solid material from the gas/liquid stream using cyclones
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
    • B01J8/16—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with particles being subjected to vibrations or pulsations
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
    • B01J8/18—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles
    • B01J8/24—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles according to "fluidised-bed" technique
    • B01J8/40—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles according to "fluidised-bed" technique with fluidised bed subjected to vibrations or pulsations
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
    • B01J8/18—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles
    • B01J8/24—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles according to "fluidised-bed" technique
    • B01J8/42—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles according to "fluidised-bed" technique with fluidised bed subjected to electric current or to radiations this sub-group includes the fluidised bed subjected to electric or magnetic fields
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/20—Graphite
    • C01B32/21—After-treatment
    • C01B32/22—Intercalation
    • C01B32/225—Expansion; Exfoliation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2208/00—Processes carried out in the presence of solid particles; Reactors therefor
    • B01J2208/00008—Controlling the process
    • B01J2208/00017—Controlling the temperature
    • B01J2208/00433—Controlling the temperature using electromagnetic heating
    • B01J2208/00442—Microwaves
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2208/00—Processes carried out in the presence of solid particles; Reactors therefor
    • B01J2208/00008—Controlling the process
    • B01J2208/00017—Controlling the temperature
    • B01J2208/00433—Controlling the temperature using electromagnetic heating
    • B01J2208/00469—Radiofrequency
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2208/00—Processes carried out in the presence of solid particles; Reactors therefor
    • B01J2208/00796—Details of the reactor or of the particulate material
    • B01J2208/00893—Feeding means for the reactants
    • B01J2208/00902—Nozzle-type feeding elements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2208/00—Processes carried out in the presence of solid particles; Reactors therefor
    • B01J2208/00796—Details of the reactor or of the particulate material
    • B01J2208/00893—Feeding means for the reactants
    • B01J2208/00929—Provided with baffles

Definitions

  • the present invention relates to a process for modifying particles in an apparatus with two gaseous streams.
  • Modification of properties of particles that are used as solid process material in industrial applications is an area of science and technology which is interesting for numerous technical fields: fabrication of monolithic or composite parts, mechanics, transport (vehicle structure and motors), catalysis, energy production, microelectronics, optoelectronics, leisure industry, etc.
  • particles (P1 ) which can be made from polymer, ceramic, metal semi-conductors and metal oxides, as well as layered materials including but not limited to transition metal oxides or chalcogenides.
  • particles (P1 ) which can be made from different forms of carbon like graphite (from natural and synthetic sources), expandable (e.g. intercalated) graphite, graphite oxide, expanded graphite, carbon black, activated carbon, carbon fibers, carbon nanotubes, fullerenes, graphene, graphene nanoplatelets, coal, and coke.
  • morphological modification which can manifest in the alteration of the dimensions, aspect ratio, shape, optical appearance, or form of phase domains in substances (e.g. expansion of layered materials) and chemical modification (functionalization) altering at least one feature of the chemical constitution of a material which includes introduction of functional groups (e.g. 0-, N-, S-, P- Si-, H-, C-containing groups) and/or functional coatings to a material or introduction of heteroatoms (e.g. B or N) into the atomic structure of the materials.
  • functional groups e.g. 0-, N-, S-, P- Si-, H-, C-containing groups
  • heteroatoms e.g. B or N
  • activation of the gas phase and/or the starting material can be reached in different ways, e.g. thermal, reactive plasma, chemical, radio frequency heating, laser heating, flame pyrolysis, microwave heating, combinations thereof, etc.
  • US 2012/0145041 A1 describes plasma-treating of small particles, such as carbon nanotubes which are suspended in a rotating drum in a capacitive glow discharge.
  • US 201 1/0300056 A1 describes a process for production of nano-structures, involving providing a graphite flake comprising graphene layers, intercalating the graphite flake to form a graphite intercalation compound and exfoiliating the graphite intercalation compound by exposing it to a temperature between about 1600°C and about 2400°C such that a plurality of individual graphene layers are separated from the graphite intercalation compound.
  • US 2013/0022530 A1 describes a process for the production of exfoliated graphite, involving providing a graphite intercalation compound and exfoliating the graphite intercalation compound through a plasma which is at a of at least 6000°C to bring the graphite intercalation compound to a temperature between about 1600°C and about 3400°C.
  • These methods described in the state of the art are either suitable for low-energy plasma (e.g. capacitive glow discharge) modification at variable reaction times or for high-energy plasma modifications using plasma torches for short reaction times of usually less than one second. While in the former case no material modification is possible which requires high excitation energies, in the latter case materials can only be plasma treated during their natural flight time through the reactive zone.
  • US 2013/0022530 A1 states that the residence time of the treated materials in the reactive zone should not exceed 0.2 s. Once the material is out of the reactive zone no further modification is possible. Thus the flexibility of such methods for material treatments is limited. In particular no multistep processes are possible in the case of US 201 1/0300056 A1 and US 2013/0022530 A1 .
  • the object is achieved by a process for modifying particles (P1 ) within an apparatus (A1 ) which comprises at least two inlets for gaseous streams (G1 ) and (G2), a gas inlet zone (IZ), a reactive zone (RZ) located below the gas inlet zone (IZ), a sample holder (SH) located below the reactive zone (RZ) and an outlet (01 ) located at the bottom of (A1 ), wherein the process comprises the following steps a) to e): a) feeding a gaseous stream (G1 ), comprising at least one inert gas and/or reactive gas, into apparatus (A1 ) with a flow direction of (G1 ) inside the apparatus (A1 ) from top to bottom through the reactive zone (RZ), b) provision of particles (P1 ) on the sample holder (SH) of apparatus (A1 ), c) feeding at least one pulse of a gaseous stream (G2), comprising at least one inert gas and/or reactive gas, to carry
  • a major advantage is that morphological modification (e.g. consecutive expansion) and chemical modification can be established in the same apparatus in a combined way.
  • the combination of morphological and chemical modification in a consecutive process allows a versatile material treatment within a setup of a single apparatus and leads to a more homogeneous material treatment.
  • a further advantage is that the particles (P1 ) are more homogeneously exposed to the reactive gas phase in the reactive zone (RZ) under these conditions, since the gas flow in apparatus (A1 ) is not continuous anymore due to the pulse of (G2), so that the particles are prevented from forming porous agglomerates as described above.
  • a further advantage is that material elutriation during the pulses of the at least one gaseous stream (G2) is reduced because of the different directions of the flow.
  • the intervals between the pulses, the pulse frequency, the pulse length, the pulse strength (which can be controlled by the gas flow rate of the pulse as well as by the gas pressure of the pulse) and experiment duration are freely adjustable.
  • the excitation energy can be varied at any moment during the experiment, e.g. different excitation energy profiles can be realized, e.g. constant values, ramps, step profiles and/or pulse profiles.
  • the gas in gaseous streams (G1 ) and (G2) can be varied at any moment during the experiment.
  • Apparatus (A1 ) comprises at least two inlets for gaseous streams (G1 ) and (G2), a gas inlet zone (IZ), a reactive zone (RZ) located below the gas inlet zone (IZ), a sample holder (SH) located below the reactive zone (RZ) and an outlet (01 ) located at the bottom of (A1 ).
  • Apparatus (A1 ) and the optional apparatus (A2) according to the present invention can be seen for instance in Figures 1 and 3 and can contain optionally a pump at outlet (01 ) and/or outlet (02).
  • the reactive zone (RZ) is the area inside apparatus (A1 ) in which reactions of particles (P1 ) take place. This area can consume a large area inside apparatus (A1 ).
  • the gas inlet zone (IZ) above the reactive zone (RZ) is needed as a vacuum reservoir to accommodate the additional gas due to the gas flow and/or the gas pulses.
  • the sample holder in apparatus (A1 ) is freely adjustable to the conditions needed and can be a glass frit or anything which is suitable by any means which is known to a person skilled in the art.
  • Particles (P1 ) according to the present invention can contain but are not limited to polymers, ceramic (e.g. SiC, WC, TiN), metal, semi-conductor (e.g. Si), metal oxides (e.g. Al 2 0 3 ), layered materials (e.g. transition metal oxides, transition metal chalcogenides), different forms of carbon (e.g.
  • the particles (P1 ) are preferably natural graphite, synthetic graphite, graphite oxide, expanded graphite, expandable graphite, intercalated graphite, carbon black, activated carbon, carbon fibers, carbon nanotubes, fullerenes, graphene, coal or coke, wherein any mixtures and composites of the aforementioned materials are possible and wherein these particles (P1 ) can be used in various forms and shapes including but not limited to expandable and/or intercalated materials, spherical particles, fibers or platelets, the particles (P1 ) are preferably natural graphite, synthetic graphite, graphite oxide, expanded graphite, expandable graphite, intercalated graphite, carbon black, activated carbon, carbon fibers, carbon nanotubes, fullerenes, graphene, coal or coke, most preferably the particles (P1 ) are natural graphite, synthetic graphite, expandable or intercalated graphite.
  • intercalated graphite is obtained from graphite after an intercalation step, and can be e.g. a graphite sulfate or graphite nitrate based intercalation compound of different degrees of intercalation or graphite containing other intercalants, resulting in compounds with variable stoichiometry. This intercalated graphite is then expandable.
  • modification is defined as follows: morphological modification, which can manifest in the alteration of the dimensions, aspect ratio, shape, optical appearance, or form of phase domains in substances (e.g. expansion of layered materials) and is mainly seen as resulting in structural changes of the particles (P1 ) without substantially altering the chemical constitution.
  • Chemical modification is the altering of at least one feature of the chemical constitution of a material which includes an exchange or introduction of functional groups (e.g. 0-, N-, S-, P- Si-, H-, C- and halogen-containing functional groups) and/or functional coatings to a material or introduction of heteroatoms (e.g. O, C, S, B, halogens or N) on the surface or into the atomic structure of the materials.
  • functional groups e.g. 0-, N-, S-, P- Si-, H-, C- and halogen-containing functional groups
  • heteroatoms e.g. O, C, S, B, halogens or N
  • the gaseous stream (G2) can be fed into apparatus (A1 ) at several positions below the sample holder (SH) at the same time.
  • the gaseous streams (G1 ) and (G2) can originate from the same reservoir or from different reservoirs.
  • the gaseous streams (G1 ) and (G2) can be gas mixtures of the same composition. They can also be gas mixtures of different composition.
  • the flow of gaseous streams (G1 ) and (G2) can have up to 50000 seem, preferably up to 2000 seem, more preferably up to 500 seem and can be in different ranges for (G1 ) and (G2). In principle, there is no upper limit for the gas flows.
  • step a) feeding a gaseous stream (G1 ), comprising at least one inert gas and/or reactive gas, into apparatus (A1 ) with a flow direction of (G1 ) inside the apparatus (A1 ) from top to bottom through the reactive zone (RZ) is provided.
  • a gaseous stream comprising at least one inert gas and/or reactive gas
  • continuous flow as mentioned above can be understood as a flow (of gas) which is not pulsed and thus continuous.
  • the feeding of gaseous stream (G1 ) is continuous feeding, more preferably a continuous feeding in steps a) to d).
  • step e) where the discharging of gaseous stream (G1 ) and/or gaseous stream (G2) out of apparatus (A1 ) takes place, it is possible to switch off gaseous stream (G1 ).
  • inert gases can contain but are not limited to Ar and He.
  • reactive gases can contain but are not limited to H 2 , N 2 , C0 2 , gases that generate 0-, N-, S-, P- Si-, H-, C- or halogen containing functional groups on the particles (P1 ), a gas that introduces B or N atoms in the particles (P1 ) or a mixture thereof, preferably H 2 , N 2 or C0 2 .
  • step b) particles (P1 ) as defined above are provided on the sample holder (SH) of apparatus (A1 ).
  • step c) feeding at least one pulse of a gaseous stream (G2), comprising at least one inert gas and/or reactive gas, to carry particles (P1 ) into the reactive zone (RZ), and (G2) is fed into apparatus (A1 ) at a position below the sample holder (SH) is provided.
  • a pulse of a gaseous stream is understood to mean pulse of gas flow. Therefore, a pulse consists of a flow which is restricted by time. Such a pulse can be very short ( ⁇ 10 s) and reaching up to minutes ( ⁇ 10 min) or longer in different setups.
  • pulses not longer than 30 min are pulses not longer than 5 min, most preferred are pulses not longer than 1 minute.
  • the time between the pulses can be as long as the pulses themselves but also longer or shorter.
  • the breaks between pulses are usually not longer than 60 min, preferably shorter than 10 min, more preferably shorter than 5 min, most preferably shorter than 1 min.
  • the expression "to carry particles (P1 ) into the reactive zone (RZ)” is understood to mean that the particles are brought up into the reactive zone (RZ) through the pulse(s) of gaseous stream (G2) and holds them there and mixes them (see for instance Example 3). Another way of describing this procedure would be to fluidize the particles (P1 ) and that they are immersed into the reactive zone (RZ).
  • step d) modification of particles (P1 ) in the reactive zone (RZ) is provided. The modification takes place preferably in the reactive zone (RZ). Therefore it is important to keep the particles (P1 ) long enough in this reactive zone to achieve better and more complete results.
  • the particles (P1 ) are modified in step d) in different ways, e.g. thermal activation, plasma activation, plasma and electrical high frequency field activation, chemical reaction with an reactive gas or a combination of gases, radio-frequency heating, laser heating, flame pyrolysis, microwave heating as well as combinations thereof, preferably by plasma activation optionally including a chemical reaction with a reactive gas or a combination of gases.
  • step e) discharging the gaseous stream (G1 ) and/or the gaseous stream (G2) via the outlet (01 ) out of apparatus (A1 ) is provided.
  • the outlet (01 ) is understood to mean an opening to discharge the gaseous streams (G1 ) and (G2).
  • Outlet (01 ) can be optionally connected to a pump.
  • a reduced pressure condition within the apparatus (A1 ) is provided, wherein the process can be carried out at atmospheric pressure, preferably less than 200 mbar, more preferably less than 50 mbar, most preferably less than 10 mbar.
  • This reduced pressure condition (compared to the condition without the pump) enables to run the pump even with atmospheric pressure, since this is less pressure than the pressure present in apparatus (A1 ) which enables to discharge gaseous streams (G1 ) and (G2).
  • the outlet (02) is an optional opening through which particles and gases (e.g. after the reaction of step d)) can be transported (or e.g. blown out) to apparatus (A2) containing e.g. a reservoir, a filter, a cyclone separator for collecting the particles and/or a pump.
  • apparatus (A2) containing e.g. a reservoir, a filter, a cyclone separator for collecting the particles and/or a pump.
  • new (fresh, raw, unmodified) material can be fed into apparatus (A1 ), e.g. by a powder feeder, which is known to the person skilled in the art and which is located at the top of apparatus (A1 ), after removal of particles (P1 ) which have been modified in step d) of the process before.
  • a powder feeder which is known to the person skilled in the art and which is located at the top of apparatus (A1 ), after removal of particles (P1 ) which have been modified in step d) of the process before.
  • step a) is carried out in the gas phase and the gas phase in the reactive zone (RZ) can be activated via means of plasma.
  • the necessary energy can be transmitted to the gas phase by an electro-magnetic field either by coupling of a microwave discharge (2.45 GHz, 915 MHz or any other suitable frequency) coupled into the reactive zone or by an inductively or capacitively coupled plasma (generated from 27.12 MHz, 13.56 MHz or any other suitable frequency) and generated at the reactive zone (RZ).
  • the usable output power of the generator employed for providing the energy in order to carry out the modification under plasma activation is known to a person skilled in the art.
  • the generator is a microwave or radio-frequency generator and the energy is not limited to an upper value. If plasma activation is used, the generator power is not more than 500 kW, preferably the generator power is not more than 100 kW, more preferably the generator power is not more than 30 kW and most preferably the generator power is not more than 5 kW.
  • the lower limit of the generator power is preferably not below 1 W.
  • the electromagnetic excitation frequency can be below 100 Hz, in a low-frequency range between 100 Hz and 10 kHz, in a radiofrequency range between 10 kHz and 300 MHz, in a microwave frequency range between 300 MHz and 300 GHz and/or above 300 GHz.
  • gaseous stream (G2) can have different angles a relative to gaseous stream (G1 ) in respect of their individual flow direction.
  • the angle a cannot be higher than 180°, since 180° means that gaseous stream (G2) is in the opposite direction to gaseous stream (G1 ) (see Figure 2). Accordingly an angle a of e.g. 200° would equal an angle a of 160°.
  • the flow direction of at least one pulse of gaseous stream (G2) inside apparatus (A1 ) has an angle a of at least 50° different to the flow direction of (G1 ), preferably of between 50° and 180°, more preferably of between 80° and 120°, most preferably of 90°, different to the flow direction of gaseous stream (G1 ).
  • the pulse of gaseous stream (G2) can easily reach the particles (P1 ) on the sample holder (SH) by way of turbulence caused by gaseous streams (G1 ) and (G2) in apparatus (A1 ).
  • the freely settled/poured bulk density of a material is calculated by dividing the mass weight filled in apparatus (A1 ) by the volume filled.
  • the reaction product can consist of expanded material as well as unexpanded material.
  • the value of the freely settled/poured bulk density of the material is a combined measure for the degree of expansion (how much is a particle (P1 ) expanded) as well as for the amount of expanded material (how much of the starting material is expanded). It is used in this context to evaluate the efficiency of the three different processes (Examples 1 to 3) for the expansion of expandable intercalated graphite.
  • the freely settled/poured bulk density of the materials is determined prior and after the treatment.
  • This process is a standard fluidization process, which can be found in literature (e.g. in "Principles and applications of CVD powder technology", C. Vahlas, B. Caussat, Ph. Serp, G. Angelopoulos, Mat. Sci. Eng. Reports, 2006, 53, 1 -72).
  • the gaseous stream is supplied continuously in forward direction (which corresponds in Figure 1 to gaseous stream (G2) in a continuous flow mode), i.e. the gas flow enters the system from below the sample holder (SH) and flows upwards thus fluidizing the particles (P1 ) lying on the sample holder into the reactive zone.
  • the pumping of the gases is carried out from the top, i.e. above the sample holder (SH) and the particles (P1 ).
  • any particles (P1 ) in the system are pressed down against the sample holder (SH).
  • the pumping of the gases is carried out from below the sample holder (SH). Due to the reversed gas stream direction in comparison to Example 1 , no particle mixing takes place and only the particle surface directly exposed to the plasma is modified leaving all particles and particle areas not directly exposed to the plasma untreated.
  • Gaseous stream (G1 ) enters Apparatus (A1 ) at the top and flows downwards, i.e. the particles (P1 ) in Apparatus (A1 ) are pressed down against the sample holder (SH).
  • the pumping of the gases is carried out from below the sample holder (SH).
  • Mixing of particles (P1 ) is assured by consecutive pressure/gas flow of gaseous stream (G1 ) and impulses of gaseous stream (G2) which carries the particles (P1 ) into the reactive zone (RZ), holds them there and mixes them.
  • the downward flow (G1 ) reduces elutriation of particles (P1 ). With an increasing number of pressure impulses of gaseous stream (G2) the particles (P1 ) are expanded.
  • the freely settled bulk density of the starting material was about 570 mg/cm 3 .
  • Example 3 10 57
  • Examples 4 - 6 Multi-step experiments (consecutive expansion and chemical modification)
  • the expandable intercalated graphite is expanded in an argon plasma and then modified in the second step.
  • Example 4 the inert gas argon is used also during the chemical modification step to supply a reference sample.
  • nitrogen plasma modification is carried out after argon plasma expansion.
  • Example 6 carbon dioxide plasma modification is carried out after argon plasma expansion.
  • heteroatoms e.g. nitrogen are introduced, and/or functional groups, e.g. containing oxygen or nitrogen are formed at the material surface.
  • the inert gas argon is used for both, consecutive expansion (a morphological modification) and chemical modification. No reactive gas is used for the modification step in order to provide a reference sample.
  • Example 5 (inventive): argon plasma consecutive expansion and C0 2 plasma modification
  • Example 6 argon plasma expansion and N 2 plasma modification
  • the oxygen content of the treated material can be increased (see Table 2).
  • a modification step using a nitrogen containing plasma e.g. nitrogen plasma (example 6)
  • the nitrogen content of the material is increased (see Table 2).
  • new nitrogen functional groups not present in the starting material are formed (see Figure 4).
  • the spectra illustrate that the nitrogen plasma modification step (Example 6) not only increases the nitrogen content in the treated material but also results in the formation of new nitrogen species (which were not present in the material before the nitrogen plasma modification).

Abstract

The present invention relates to a process for modifying particles. The object is achieved by a process for modifying particles (P1) within an apparatus (Al) which comprises at least two inlets for gaseous streams (Gl) and (G2), a gas inlet zone (IZ), a reactive zone (RZ) located below the gas inlet zone (IZ), a sample holder (SH) located below the reactive zone (RZ) and an outlet (01) located at the bottom of (Al), wherein the process comprises feeding at least one pulse of a gaseous stream (G2), comprising at least one inert gas and/or reactive gas, to carry particles (P1) into the reactive zone (RZ). This pulse of a gaseous stream (G2) is fed into apparatus (Al) at a position below the sample holder (SH).

Description

Process for Modification of Particles
Description The present invention relates to a process for modifying particles in an apparatus with two gaseous streams.
Modification of properties of particles that are used as solid process material in industrial applications is an area of science and technology which is interesting for numerous technical fields: fabrication of monolithic or composite parts, mechanics, transport (vehicle structure and motors), catalysis, energy production, microelectronics, optoelectronics, leisure industry, etc.
Useful for such processes are particles (P1 ) which can be made from polymer, ceramic, metal semi-conductors and metal oxides, as well as layered materials including but not limited to transition metal oxides or chalcogenides.
Further, useful for such processes as well are particles (P1 ) which can be made from different forms of carbon like graphite (from natural and synthetic sources), expandable (e.g. intercalated) graphite, graphite oxide, expanded graphite, carbon black, activated carbon, carbon fibers, carbon nanotubes, fullerenes, graphene, graphene nanoplatelets, coal, and coke.
It is known that in these processes two kinds of particle modification can be conducted: morphological modification which can manifest in the alteration of the dimensions, aspect ratio, shape, optical appearance, or form of phase domains in substances (e.g. expansion of layered materials) and chemical modification (functionalization) altering at least one feature of the chemical constitution of a material which includes introduction of functional groups (e.g. 0-, N-, S-, P- Si-, H-, C-containing groups) and/or functional coatings to a material or introduction of heteroatoms (e.g. B or N) into the atomic structure of the materials. This can usually be conducted in the reactive zone of the apparatus used for the respective process. In the reactive zone, activation of the gas phase and/or the starting material can be reached in different ways, e.g. thermal, reactive plasma, chemical, radio frequency heating, laser heating, flame pyrolysis, microwave heating, combinations thereof, etc.
For some processes a morphological modification is desired, whereas other for processes chemical modification is desired, and again other processes even require consecutive or combined steps of morphological and chemical modification.
US 2012/0145041 A1 describes plasma-treating of small particles, such as carbon nanotubes which are suspended in a rotating drum in a capacitive glow discharge. US 201 1/0300056 A1 describes a process for production of nano-structures, involving providing a graphite flake comprising graphene layers, intercalating the graphite flake to form a graphite intercalation compound and exfoiliating the graphite intercalation compound by exposing it to a temperature between about 1600°C and about 2400°C such that a plurality of individual graphene layers are separated from the graphite intercalation compound.
US 2013/0022530 A1 describes a process for the production of exfoliated graphite, involving providing a graphite intercalation compound and exfoliating the graphite intercalation compound through a plasma which is at a of at least 6000°C to bring the graphite intercalation compound to a temperature between about 1600°C and about 3400°C. These methods described in the state of the art are either suitable for low-energy plasma (e.g. capacitive glow discharge) modification at variable reaction times or for high-energy plasma modifications using plasma torches for short reaction times of usually less than one second. While in the former case no material modification is possible which requires high excitation energies, in the latter case materials can only be plasma treated during their natural flight time through the reactive zone.
For example US 2013/0022530 A1 states that the residence time of the treated materials in the reactive zone should not exceed 0.2 s. Once the material is out of the reactive zone no further modification is possible. Thus the flexibility of such methods for material treatments is limited. In particular no multistep processes are possible in the case of US 201 1/0300056 A1 and US 2013/0022530 A1 .
In principle fluidized bed systems offer the possibility to treat particles in a selected range of excitation energies and treatment times. However, the materials to be treated have to be fluidizable which can be a serious challenge in the case of small particle sizes (micron scale or below) or lightweight mesoscale particles, for particles exhibiting high interparticle cohesive forces, agglomeration tendencies, unsuitable aspect ratios or significant morphological changes during the reaction (e.g. resulting in very fluffy particles) all leading to a bad or no fluidization at all. In that case the particles are not mixed anymore resulting in very bad and inhomogeneous material treatment. However, there is no option to combine a wide range of excitation energy, treatment time and chemical and morphological modifications (functionalizations) for a treatment of such poorly fluidizable materials available. Nowhere in the state of the art a process is disclosed which allows to carry (fluidize) particles (P1 ) into the reactive zone and hold them in the reactive zone with a pulsed gas flow for chemical and/or morphological modification offering at the same time high flexibility in the treatable materials, treatment times, activation method (and thus also activation energies) and the possibility of multi-step processes.
It is an object of the present invention to provide a novel process for modifying particles, especially graphite, intercalated graphite and expandable graphite.
The object is achieved by a process for modifying particles (P1 ) within an apparatus (A1 ) which comprises at least two inlets for gaseous streams (G1 ) and (G2), a gas inlet zone (IZ), a reactive zone (RZ) located below the gas inlet zone (IZ), a sample holder (SH) located below the reactive zone (RZ) and an outlet (01 ) located at the bottom of (A1 ), wherein the process comprises the following steps a) to e): a) feeding a gaseous stream (G1 ), comprising at least one inert gas and/or reactive gas, into apparatus (A1 ) with a flow direction of (G1 ) inside the apparatus (A1 ) from top to bottom through the reactive zone (RZ), b) provision of particles (P1 ) on the sample holder (SH) of apparatus (A1 ), c) feeding at least one pulse of a gaseous stream (G2), comprising at least one inert gas and/or reactive gas, to carry particles (P1 ) into the reactive zone (RZ), and (G2) is fed into apparatus (A1 ) at a position below the sample holder (SH), d) modification of particles (P1 ) in the reactive zone (RZ), and e) discharging the gaseous stream (G1 ) and/or the gaseous stream (G2) via the outlet (01 ) out of apparatus (A1 ).
A major advantage is that morphological modification (e.g. consecutive expansion) and chemical modification can be established in the same apparatus in a combined way. The combination of morphological and chemical modification in a consecutive process allows a versatile material treatment within a setup of a single apparatus and leads to a more homogeneous material treatment.
A further advantage is that the particles (P1 ) are more homogeneously exposed to the reactive gas phase in the reactive zone (RZ) under these conditions, since the gas flow in apparatus (A1 ) is not continuous anymore due to the pulse of (G2), so that the particles are prevented from forming porous agglomerates as described above.
Further to that, due to the pulse mode of gaseous stream (G2) the mixing of particles (P1 ) is assured, so that much more particles (P1 ) are exposed to the plasma and therefore can be modified. A further advantage is that material elutriation during the pulses of the at least one gaseous stream (G2) is reduced because of the different directions of the flow.
Another advantage is that the intervals between the pulses, the pulse frequency, the pulse length, the pulse strength (which can be controlled by the gas flow rate of the pulse as well as by the gas pressure of the pulse) and experiment duration are freely adjustable. Furthermore the excitation energy can be varied at any moment during the experiment, e.g. different excitation energy profiles can be realized, e.g. constant values, ramps, step profiles and/or pulse profiles. Furthermore the gas in gaseous streams (G1 ) and (G2) can be varied at any moment during the experiment.
The process according to the invention for modifying particles (P1 ) within an apparatus (A1 ) is defined in detail hereinafter. Apparatus (A1 ) comprises at least two inlets for gaseous streams (G1 ) and (G2), a gas inlet zone (IZ), a reactive zone (RZ) located below the gas inlet zone (IZ), a sample holder (SH) located below the reactive zone (RZ) and an outlet (01 ) located at the bottom of (A1 ). Apparatus (A1 ) and the optional apparatus (A2) according to the present invention can be seen for instance in Figures 1 and 3 and can contain optionally a pump at outlet (01 ) and/or outlet (02). All parts of apparatus (A1 ) and the optional apparatus (A2) are known to the person skilled in the art. For the sake of completeness it is mentioned that at the position of the arrows in Figures 1 and 3 the respective inlets and outlets are present. The Figures 1 and 3 only show the schematic setting of apparatus (A1 ) and the optional apparatus (A2).
Within the context of the present invention, the reactive zone (RZ) is the area inside apparatus (A1 ) in which reactions of particles (P1 ) take place. This area can consume a large area inside apparatus (A1 ).
The gas inlet zone (IZ) above the reactive zone (RZ) is needed as a vacuum reservoir to accommodate the additional gas due to the gas flow and/or the gas pulses. Furthermore, the sample holder in apparatus (A1 ) is freely adjustable to the conditions needed and can be a glass frit or anything which is suitable by any means which is known to a person skilled in the art.
Particles (P1 ) according to the present invention can contain but are not limited to polymers, ceramic (e.g. SiC, WC, TiN), metal, semi-conductor (e.g. Si), metal oxides (e.g. Al203), layered materials (e.g. transition metal oxides, transition metal chalcogenides), different forms of carbon (e.g. natural graphite, synthetic graphite, graphite oxide, expanded graphite, expandable graphite, intercalated graphite, carbon black, activated carbon, carbon fibers, carbon nanotubes, fullerenes, graphene, coal or coke, wherein any mixtures and composites of the aforementioned materials are possible and wherein these particles (P1 ) can be used in various forms and shapes including but not limited to expandable and/or intercalated materials, spherical particles, fibers or platelets, the particles (P1 ) are preferably natural graphite, synthetic graphite, graphite oxide, expanded graphite, expandable graphite, intercalated graphite, carbon black, activated carbon, carbon fibers, carbon nanotubes, fullerenes, graphene, coal or coke, most preferably the particles (P1 ) are natural graphite, synthetic graphite, expandable or intercalated graphite.
Within the context of the present invention intercalated graphite is obtained from graphite after an intercalation step, and can be e.g. a graphite sulfate or graphite nitrate based intercalation compound of different degrees of intercalation or graphite containing other intercalants, resulting in compounds with variable stoichiometry. This intercalated graphite is then expandable.
Within the context of the present invention modification is defined as follows: morphological modification, which can manifest in the alteration of the dimensions, aspect ratio, shape, optical appearance, or form of phase domains in substances (e.g. expansion of layered materials) and is mainly seen as resulting in structural changes of the particles (P1 ) without substantially altering the chemical constitution.
Chemical modification (functionalization) is the altering of at least one feature of the chemical constitution of a material which includes an exchange or introduction of functional groups (e.g. 0-, N-, S-, P- Si-, H-, C- and halogen-containing functional groups) and/or functional coatings to a material or introduction of heteroatoms (e.g. O, C, S, B, halogens or N) on the surface or into the atomic structure of the materials.
Within the context of the present invention, the gaseous stream (G2) can be fed into apparatus (A1 ) at several positions below the sample holder (SH) at the same time.
Within the context of the present invention, the gaseous streams (G1 ) and (G2) can originate from the same reservoir or from different reservoirs. Within the context of the present invention, the gaseous streams (G1 ) and (G2) can be gas mixtures of the same composition. They can also be gas mixtures of different composition. Further, the flow of gaseous streams (G1 ) and (G2) can have up to 50000 seem, preferably up to 2000 seem, more preferably up to 500 seem and can be in different ranges for (G1 ) and (G2). In principle, there is no upper limit for the gas flows.
Within the context of the present invention, in step a) feeding a gaseous stream (G1 ), comprising at least one inert gas and/or reactive gas, into apparatus (A1 ) with a flow direction of (G1 ) inside the apparatus (A1 ) from top to bottom through the reactive zone (RZ) is provided. Here, the expression "feeding a gaseous stream" is understood to mean a continuous flow of inert and/or reactive gas through the reactive zone (RZ).
Within the context of the present invention "continuous flow" as mentioned above can be understood as a flow (of gas) which is not pulsed and thus continuous. However, it is still possible to switch off gaseous stream (G1 ). This might be helpful e.g. to transport the particles into apparatus (A2). Preferably, the feeding of gaseous stream (G1 ) is continuous feeding, more preferably a continuous feeding in steps a) to d). In step e), where the discharging of gaseous stream (G1 ) and/or gaseous stream (G2) out of apparatus (A1 ) takes place, it is possible to switch off gaseous stream (G1 ).
Within the context of the present invention, inert gases can contain but are not limited to Ar and He. Within the context of the present invention, reactive gases can contain but are not limited to H2, N2, C02, gases that generate 0-, N-, S-, P- Si-, H-, C- or halogen containing functional groups on the particles (P1 ), a gas that introduces B or N atoms in the particles (P1 ) or a mixture thereof, preferably H2, N2 or C02. Within the context of the present invention, in step b) particles (P1 ) as defined above are provided on the sample holder (SH) of apparatus (A1 ).
Within the context of the present invention, in step c) feeding at least one pulse of a gaseous stream (G2), comprising at least one inert gas and/or reactive gas, to carry particles (P1 ) into the reactive zone (RZ), and (G2) is fed into apparatus (A1 ) at a position below the sample holder (SH) is provided. Here, the expression "feeding at least one pulse of a gaseous stream" is understood to mean pulse of gas flow. Therefore, a pulse consists of a flow which is restricted by time. Such a pulse can be very short (< 10 s) and reaching up to minutes (< 10 min) or longer in different setups. Preferred are pulses not longer than 30 min, more preferred are pulses not longer than 5 min, most preferred are pulses not longer than 1 minute. The time between the pulses can be as long as the pulses themselves but also longer or shorter. The breaks between pulses are usually not longer than 60 min, preferably shorter than 10 min, more preferably shorter than 5 min, most preferably shorter than 1 min.
Within the context of the present invention, the expression "to carry particles (P1 ) into the reactive zone (RZ)" is understood to mean that the particles are brought up into the reactive zone (RZ) through the pulse(s) of gaseous stream (G2) and holds them there and mixes them (see for instance Example 3). Another way of describing this procedure would be to fluidize the particles (P1 ) and that they are immersed into the reactive zone (RZ). Within the context of the present invention, in step d) modification of particles (P1 ) in the reactive zone (RZ) is provided. The modification takes place preferably in the reactive zone (RZ). Therefore it is important to keep the particles (P1 ) long enough in this reactive zone to achieve better and more complete results. Here, more than one step of modification and different kinds of modification (morphological and chemical, as defined above) are possible, which can be seen for instance in examples 4 - 6. As well it is possible to have consecutive expansion and chemical modification, for example the introduction of heteroatoms, like e.g. N, O, C, S, B or halogens. In one embodiment of the invention, the particles (P1 ) are modified in step d) in different ways, e.g. thermal activation, plasma activation, plasma and electrical high frequency field activation, chemical reaction with an reactive gas or a combination of gases, radio-frequency heating, laser heating, flame pyrolysis, microwave heating as well as combinations thereof, preferably by plasma activation optionally including a chemical reaction with a reactive gas or a combination of gases.
Within the context of the present invention, in step e) discharging the gaseous stream (G1 ) and/or the gaseous stream (G2) via the outlet (01 ) out of apparatus (A1 ) is provided.
Within the context of the present invention, the outlet (01 ) is understood to mean an opening to discharge the gaseous streams (G1 ) and (G2). Outlet (01 ) can be optionally connected to a pump. With this pump a reduced pressure condition within the apparatus (A1 ) is provided, wherein the process can be carried out at atmospheric pressure, preferably less than 200 mbar, more preferably less than 50 mbar, most preferably less than 10 mbar. This reduced pressure condition (compared to the condition without the pump) enables to run the pump even with atmospheric pressure, since this is less pressure than the pressure present in apparatus (A1 ) which enables to discharge gaseous streams (G1 ) and (G2).
Within the context of the present invention, the outlet (02) is an optional opening through which particles and gases (e.g. after the reaction of step d)) can be transported (or e.g. blown out) to apparatus (A2) containing e.g. a reservoir, a filter, a cyclone separator for collecting the particles and/or a pump.
Further, new (fresh, raw, unmodified) material (particles (P1 )) can be fed into apparatus (A1 ), e.g. by a powder feeder, which is known to the person skilled in the art and which is located at the top of apparatus (A1 ), after removal of particles (P1 ) which have been modified in step d) of the process before.
In one embodiment of the invention, step a) is carried out in the gas phase and the gas phase in the reactive zone (RZ) can be activated via means of plasma. The necessary energy can be transmitted to the gas phase by an electro-magnetic field either by coupling of a microwave discharge (2.45 GHz, 915 MHz or any other suitable frequency) coupled into the reactive zone or by an inductively or capacitively coupled plasma (generated from 27.12 MHz, 13.56 MHz or any other suitable frequency) and generated at the reactive zone (RZ).
The usable output power of the generator employed for providing the energy in order to carry out the modification under plasma activation is known to a person skilled in the art. Preferably the generator is a microwave or radio-frequency generator and the energy is not limited to an upper value. If plasma activation is used, the generator power is not more than 500 kW, preferably the generator power is not more than 100 kW, more preferably the generator power is not more than 30 kW and most preferably the generator power is not more than 5 kW. The lower limit of the generator power is preferably not below 1 W.
In one embodiment of the invention, if plasma activation is used the electromagnetic excitation frequency can be below 100 Hz, in a low-frequency range between 100 Hz and 10 kHz, in a radiofrequency range between 10 kHz and 300 MHz, in a microwave frequency range between 300 MHz and 300 GHz and/or above 300 GHz.
Within the context of the present invention, gaseous stream (G2) can have different angles a relative to gaseous stream (G1 ) in respect of their individual flow direction. The angle a cannot be higher than 180°, since 180° means that gaseous stream (G2) is in the opposite direction to gaseous stream (G1 ) (see Figure 2). Accordingly an angle a of e.g. 200° would equal an angle a of 160°. In one preferred embodiment of the present invention, the flow direction of at least one pulse of gaseous stream (G2) inside apparatus (A1 ) has an angle a of at least 50° different to the flow direction of (G1 ), preferably of between 50° and 180°, more preferably of between 80° and 120°, most preferably of 90°, different to the flow direction of gaseous stream (G1 ).
However, in any of these mentioned angles the pulse of gaseous stream (G2) can easily reach the particles (P1 ) on the sample holder (SH) by way of turbulence caused by gaseous streams (G1 ) and (G2) in apparatus (A1 ). Examples:
Starting material (particles (P1 ) for all 6 examples: intercalated expandable graphite (Graphit Kropfmuhl ES350 F5, lateral size: 80 % > 300 μηι) Examples 1 - 3: Comparison of processes
The freely settled/poured bulk density of a material is calculated by dividing the mass weight filled in apparatus (A1 ) by the volume filled. Depending on the experiments below the reaction product can consist of expanded material as well as unexpanded material.
The value of the freely settled/poured bulk density of the material is a combined measure for the degree of expansion (how much is a particle (P1 ) expanded) as well as for the amount of expanded material (how much of the starting material is expanded). It is used in this context to evaluate the efficiency of the three different processes (Examples 1 to 3) for the expansion of expandable intercalated graphite. The freely settled/poured bulk density of the materials is determined prior and after the treatment.
Example 1 (comparative)
This process is a standard fluidization process, which can be found in literature (e.g. in "Principles and applications of CVD powder technology", C. Vahlas, B. Caussat, Ph. Serp, G. Angelopoulos, Mat. Sci. Eng. Reports, 2006, 53, 1 -72). In this process one gaseous stream is used. The gaseous stream is supplied continuously in forward direction (which corresponds in Figure 1 to gaseous stream (G2) in a continuous flow mode), i.e. the gas flow enters the system from below the sample holder (SH) and flows upwards thus fluidizing the particles (P1 ) lying on the sample holder into the reactive zone. The pumping of the gases is carried out from the top, i.e. above the sample holder (SH) and the particles (P1 ).
Experimental parameters:
argon flow (G2): 100-900 ml/min
(the flow was gradually increased during the experiment to carry more starting material into the reactive zone);
reaction time: 20 min;
generator power: 1 .5 - 2 kW
(the generator power was increased in accordance with the increased gas stream).
Example 2 (comparative)
This process is a standard exposure of unagitated particles to a RF Plasma, which can be found in literature (e.g. in "Plasma-assisted simultaneous reduction and nitrogen doping of graphene oxide nanosheets", N. A. Kumar, H. Nolan, N. McEvoy, E. Rezvani, R. L. Doyle, M. E. G. Lyons and G. S. Duesberg, J. Mater. Chem. A, 2013, vol. 1 , pp. 4431-4435.). In this process only one gaseous stream is used. The gaseous stream enters the system at the top and flows downwards (which corresponds in Figure 1 to gaseous stream (G1 ) in a continuous flow mode) (e.g. in "Formation of silicon carbide and silicon carbonitride by RF-plasma CVD", H. Sachdev, P. Scheid, Diamond and Related Materials, vol. 10, issue 3-7, pp. 1 160-1 164), i.e. any particles (P1 ) in the system are pressed down against the sample holder (SH). The pumping of the gases is carried out from below the sample holder (SH). Due to the reversed gas stream direction in comparison to Example 1 , no particle mixing takes place and only the particle surface directly exposed to the plasma is modified leaving all particles and particle areas not directly exposed to the plasma untreated.
Experimental parameters:
argon flow (G1 ): 100 ml/min;
reaction time: 20 min;
generator power: 1.5 kW.
Example 3 (inventive)
The experimental arrangement is shown in Figure 1 . Gaseous stream (G1 ) enters Apparatus (A1 ) at the top and flows downwards, i.e. the particles (P1 ) in Apparatus (A1 ) are pressed down against the sample holder (SH). The pumping of the gases is carried out from below the sample holder (SH). Mixing of particles (P1 ) is assured by consecutive pressure/gas flow of gaseous stream (G1 ) and impulses of gaseous stream (G2) which carries the particles (P1 ) into the reactive zone (RZ), holds them there and mixes them. The downward flow (G1 ) reduces elutriation of particles (P1 ). With an increasing number of pressure impulses of gaseous stream (G2) the particles (P1 ) are expanded.
Experimental parameters:
argon flow (G1 ): 100 ml/min;
argon pulses (G2): 10;
reaction time: 10 min;
generator power: 1 .5 kW.
Results of Examples 1 -3
The freely settled bulk density of the starting material was about 570 mg/cm3.
Table 1 . Results of Examples 1 -3
Material freely settled bulk density of volume expansion factor
the product
(mg/cm3) (based on freely settled bulk density)
Example 1 36 16
Example 2 94 6
Example 3 10 57 Examples 4 - 6: Multi-step experiments (consecutive expansion and chemical modification)
In the first step the expandable intercalated graphite is expanded in an argon plasma and then modified in the second step.
In Example 4 the inert gas argon is used also during the chemical modification step to supply a reference sample. In Example 5, nitrogen plasma modification is carried out after argon plasma expansion. In Example 6, carbon dioxide plasma modification is carried out after argon plasma expansion.
With the chemical modification step heteroatoms, e.g. nitrogen are introduced, and/or functional groups, e.g. containing oxygen or nitrogen are formed at the material surface.
Example 4 (inventive): argon plasma consecutive expansion & argon plasma chemical modification, reference experiment
For both, consecutive expansion (a morphological modification) and chemical modification, the inert gas argon is used. No reactive gas is used for the modification step in order to provide a reference sample.
Experimental parameters for consecutive expansion (step 1 ):
argon flow (G1 ): 100 ml/min;
argon pulses (G2): 7;
reaction time: 7 min;
generator power: 1.5 kW
Experimental parameters for modification (step 2):
argon flow (G1 ): 60 ml/min;
argon pulses (G2): 8;
reaction time: 12 min;
generator power: 1 kW
Example 5 (inventive): argon plasma consecutive expansion and C02 plasma modification
Experimental parameters for consecutive expansion (step 1 ):
argon flow (G1 ): 100 ml/min;
argon pulses (G2): 7;
reaction time: 7 min;
generator power: 1 .5 kW.
Experimental parameters for consecutive expansion (step 2): carbon dioxide flow (G1 ): 60 ml/min;
argon pulses (G2): 8;
reaction time: 12 min;
generator power: 1 kW.
Example 6 (inventive): argon plasma expansion and N2 plasma modification
Experimental parameters for expansion (step 1 ):
argon flow (G1 ): 100 ml/min;
argon pulses (G2): 7;
reaction time: 7 min;
generator power: 1 .5 kW.
Experimental parameters for chemical modification (step 2):
nitrogen flow (G1 ): 60 ml/min;
argon pulses (G2): 8;
reaction time: 12 min;
generator power: 1 kW. Results of examples 4-6
By carrying out an oxidative plasma modification step, e.g. by using a C02 plasma (example 5), the oxygen content of the treated material can be increased (see Table 2). By applying a modification step using a nitrogen containing plasma, e.g. nitrogen plasma (example 6), the nitrogen content of the material is increased (see Table 2). Moreover, according to XPS, new nitrogen functional groups not present in the starting material are formed (see Figure 4).
Table 2. Results of examples 4-6. Surface elemental composition as determined by X- Ray Photoelectron Spectroscopy (XPS).
Experiment C at% O at% N at% S at% Na at%
Example 4 92,2 5,8 0,7 1 ,0 0,1
Example 5 89,4 8,3 0,8 0,9 0,4
Example 6 89,5 5,6 4,3 0,4 0,2
Further in Figure 4 is shown the N 1 s XPS detail spectra of starting materials and Examples 4 - 6. The spectra illustrate that the nitrogen plasma modification step (Example 6) not only increases the nitrogen content in the treated material but also results in the formation of new nitrogen species (which were not present in the material before the nitrogen plasma modification).

Claims

Claims
1 . A process for modifying particles (P1 ) within an apparatus (A1 ) which comprises at least two inlets for gaseous streams (G1 ) and (G2), a gas inlet zone (IZ), a reactive zone (RZ) located below the gas inlet zone (IZ), a sample holder (SH) located below the reactive zone (RZ) and an outlet (01 ) located at the bottom of (A1 ), wherein the process comprises the following steps a) to e): a) feeding a gaseous stream (G1 ), comprising at least one inert gas and/or reactive gas, into apparatus (A1 ) with a flow direction of (G1 ) inside the apparatus (A1 ) from top to bottom through the reactive zone (RZ), b) provision of particles (P1 ) on the sample holder (SH) of apparatus (A1 ), c) feeding at least one pulse of a gaseous stream (G2), comprising at least one inert gas and/or reactive gas, to carry particles (P1 ) into the reactive zone (RZ), and (G2) is fed into apparatus (A1 ) at a position below the sample holder (SH),
d) modification of particles (P1 ) in the reactive zone (RZ), and
e) discharging the gaseous stream (G1 ) and/or the gaseous stream (G2) via the outlet (01 ) out of apparatus (A1 ).
2. A process according to claim 1 , wherein the particles (P1 ) are selected from natural graphite, synthetic graphite, graphite oxide, expandable graphite, intercalated graphite, expanded graphite, carbon black, activated carbon, carbon fibers, carbon nanotubes, fullerenes, graphene, coal, coke, Al203, SiC, WC, TiN or Si, the particles (P1 ) are preferably natural graphite, synthetic graphite, graphite oxide, expanded graphite, expandable graphite, intercalated graphite, carbon black, activated carbon, carbon fibers, carbon nanotubes, fullerenes, graphene, coal or coke, most preferably the particles (P1 ) are natural graphite, synthetic graphite, intercalated graphite or expandable graphite.
3. A process according to any of claims 1 and 2, wherein the flow direction of at least one pulse of gaseous stream (G2) inside apparatus (A1 ) has an angle a of at least 50° different to the flow direction of (G1 ), preferably of between 50° and 180°, more preferably of between 80° and 120°, most preferably of 90°, different to the flow direction of gaseous stream (G1 ).
4. A process according to any of claims 1 to 3, wherein the particles (P1 ) are modified in step d) by thermal activation, plasma activation, plasma and electrical high frequency field activation, chemical reaction with an reactive gas or a combination of gases, laser heating, microwave heating, radio-frequency heating and/or flame pyrolysis, preferably by plasma activation optionally including a chemical reaction with a reactive gas or a combination of gases.
A process according to claim 4, wherein, if plasma activation is used, the generator power is not more than 500 kW, preferably the generator power is not more than 100 kW, more preferably the generator power is not more than 30 kW and most preferably the generator power is not more than 5kW.
A process according to any of claims 4 and 5, wherein if plasma activation is used the electromagnetic excitation frequency can be below 100 Hz, in a low- frequency range between 100 Hz and 10 kHz, in a radiofrequency range between 10 kHz and 300 MHz, in a microwave frequency range between 300 MHz and 300 GHz and/or above 300 GHz.
A process according to any of claims 1 to 6, wherein the flow of gaseous streams (G1 ) and (G2) can have up to 50000 seem, preferably up to 2000 seem, more preferably up to 500 seem and can be in different ranges for (G1 ) and (G2).
A process according to any of claims 1 to 7, wherein in step c) the at least one pulse of gaseous stream (G2) has a duration of not longer than 30 minutes, preferably not longer than 5 minutes, most preferably not longer than 1 minute.
A process according to any of claims 1 to 8, wherein in gaseous stream (G1 ) and/or gaseous stream (G2) the inert gas is Ar and/or He and/or the reactive gas is H2, N2, C02, a gas that generates 0-, N-, S-, P- Si-, H-, C- or halogen containing functional groups on the particles (P1 ), a gas that introduces B or N atoms in the particles (P1 ) or a mixture thereof, preferably H2, N2 or C02.
A process according to any of claims 1 to 9, wherein the outlet (01 ) of the apparatus (A1 ) is connected to a pump in order to provide a reduced pressure condition within the apparatus (A1 ), wherein the process can be carried out at atmospheric pressure, preferably less than 200 mbar, more preferably less than 50 mbar, most preferably less than 20 mbar.
A process according to any of claims 1 to 10, wherein apparatus (A1 ) connected via outlet (02) to an apparatus (A2) which comprises a reservoir, filter, a cyclone separator and/or a pump.
A process according to claim 1 1 , wherein the particles (P1 ) are transported into apparatus (A2) after being modified in step d).
13. A process according to any of claims 1 to 12, wherein fresh unmodified particles (P1 ) are fed into apparatus (A1 ) via a powder feeder located at the top of apparatus (A1 ) after removal of particles (P1 ) which have been modified in step d).
14. A process according to any of claims 1 to 13, wherein the modification of particles (P1 ) according to step d) of claim 1 comprises morphological modification and/or chemical modification.
15. A process according to claim 12, wherein the chemical modification is carried out by reaction of the particles (P1 ) with at least one reactive gas provided by gaseous streams (G1 ) and/or (G2).
16. A process according to any of claims 1 to 15, wherein the feeding of gaseous stream (G1 ) is a continuous feeding, preferably a continuous feeding in steps a) to d).
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