Fluidized bed reactor adapted for the production of biphased systems

Abstract

A fluidized bed reactor designed for in situ gas phase impregnation. The reactor comprises a tube with an upstream zone and a downstream zone, the upstream zone and the downstream zone being separated by a separation filter. A method for a controlled-deposition of a sublimated precursor onto a fluidized solid support. The method is remarkable in that it is carried out in situ within the tube of the fluidized bed reactor in accordance with the fluidized bed reactor.

Claims

1. A fluidized bed reactor, said fluidized bed reactor comprising: a gas inlet and a gas outlet being located downstream from the gas inlet; a tube made of quartz and inserted between the gas inlet and the gas outlet; and a heating part connected to the tube, wherein the tube comprises an upstream zone and a downstream zone, the upstream zone and the downstream zone being separated by a separation filter, wherein the tube is inserted inside a first seal in the gas inlet and inside a second seal in the gas outlet; and wherein at least one vibrator is connected to the tube, positioned outside the tube and distant from said tube, exclusively on a conduit between the gas inlet and the first seal.

2. The fluidized bed reactor according to claim 1, wherein the tube is made of material which is resistant to temperature of at least up to 1,000° C. and is transparent.

3. The fluidized bed reactor according to claim 1, wherein the upstream zone is delimited by the separation filter and by a first porous filter, and the downstream zone is delimited by the separation filter and by a second porous filter.

4. The fluidized bed reactor according to claim 3, wherein the first porous filter is adjacent to the first seal and the second porous filter is adjacent to the second seal.

5. The fluidized bed reactor according to claim 1, wherein the heating part is at least one of a heating cable, a heating jacket and a thermal activation source.

6. The fluidized bed reactor according to claim 1, wherein the upstream zone of the tube is configured to be loaded of at least one precursor powder to be sublimated.

7. The fluidized bed reactor according to claim 1, wherein the downstream zone of the tube is configured to be loaded with solid support.

8. The fluidized bed reactor according to claim 1, wherein the upstream zone forms a cavity to be loaded with at least one solid precursor in powder form and the downstream zone forms a cavity to be loaded with a solid support in powder form; and wherein the upstream zone is delimited by the separation filter and by a first porous filter, and the downstream zone is delimited by the separation filter and by a second porous filter, the second porous filter being structured and designed for containing inside the tube the solid support in powder form with particles of a size less than 20 μm.

9. The fluidized bed reactor according to claim 1, wherein the upstream zone is delimited by the separation filter and by a first porous filter, and the downstream zone is delimited by the separation filter and by a second porous filter.

10. The fluidized bed reactor according to claim 1, wherein the downstream zone of the tube is configured to be loaded with solid support.

11. A method for a controlled-deposition of particles onto a solid support, the method being carried out with a fluidized bed reactor and comprising the steps of: (a) fluidization of at least one solid support in powder form; and (b) impregnation of the fluidized solid support of step (a) by a sublimated precursor powder, wherein said fluidized bed reactor comprises: a gas inlet and a gas outlet being located downstream from the gas inlet; a tube made of quartz and inserted between the gas inlet and the gas outlet; and a heating part connected to the tube, wherein the tube comprises an upstream zone and a downstream zone, the upstream zone and the downstream zone being separated by a separation filter, wherein the tube is inserted inside a first seal in the gas inlet and inside a second seal in the gas outlet; and wherein at least one vibrator is connected to the tube, positioned outside the tube and distant from said tube, exclusively on a conduit between the gas inlet and the first seal.

12. The method according to claim 11, wherein the sublimated precursor powder is formed by heating a precursor powder to be sublimated.

13. The method according to claim 12, wherein the precursor powder to be sublimated is an organometallic precursor comprising a metal derivative, the metal derivative being one of titanium, vanadium, iron, chromium, ruthenium, cobalt, iridium, nickel, copper, zinc, or manganese.

14. The method according to claim 12, wherein the precursor powder to be sublimated is an organometallic precursor at least functionalized with an organic ligand.

15. The method according to claim 14, wherein the method further comprises the step of removing the organic ligand, the step of removing the organic ligand being carried out by tuning the temperature.

16. The method according to claim 11, wherein at least one of: the solid support is a powder with a mean diameter size below 20 μm, and the solid support is made of particles.

17. The method according to claim 11, wherein the step (a) is carried out with a flow of inert gas.

18. The method according to claim 11, wherein step (b) is carried out at a temperature comprised between 150° C. and 190° C. under a flow of inert gas, the flow being comprised between 50 sccm and 1,000 sccm.

Description

DRAWINGS

(1) FIG. 1 is a scheme of a fluidized bed reactor in accordance with various embodiments of the present invention.

DETAILED DESCRIPTION

(2) FIG. 1 describes the fluidized bed reactor 100 of the present invention. This device comprises a tube 2 which is transparent and resistant to high temperature, up to 1000° C., preferentially up to 1500° C. or even more. The tube 2 is preferably made of quartz. The tube 2 is inserted between a gas inlet 4 and a gas outlet 6. The gas outlet 6 is located downstream from the gas inlet 4. The connection between the tube 2 and the gas inlet 4 is sealed by a first seal 8 whose the diameter is comprised between 50 mm and 60 mm. This diameter is sufficient to insert the tube 2 inside the first seal 8. The connection between the tube 2 and the gas outlet 6 is sealed by a second seal 10 whose the diameter is comprised between 50 mm and 60 mm. This diameter is sufficient to insert the tube 2 inside the second seal 10.

(3) Furthermore, to be transparent and resistant to high temperature, the tube 2 is designed for being resistant to high vacuum and is electrically insulated.

(4) The tube 2 is divided in two zones, an upstream zone and a downstream zone, the term upstream and downstream being defined according to the direction of the gas.

(5) The upstream zone is adapted to comprise the solid precursor or the precursor powder to be sublimated 26, for example a metallic precursor or an organometallic precursor.

(6) The downstream zone is adapted to comprise a solid support 28 made of particles or a powder onto which the precursor powder to be sublimated 26 must be impregnated.

(7) The impregnation is only possible when the precursor powder to be sublimated 26 has been sublimated. This is possible by the fact that this precursor powder to be sublimated 26 is placed within the upstream zone of the tube 2 of the fluidized bed reactor, the upstream zone of the tube being connected to a heating part 18 of the fluidized bed reactor.

(8) Both zones are physically separated by a separation filter 14 which is preferentially porous.

(9) The tube 2 is further closed by a first porous filter 12 and a second porous filter 16. Those first and second porous filters are needed for containing the different materials present inside the tube 2. When the first porous filter 12 and second porous filter 16 are placed on the tube, they thus prevent the materials to exit the tube 2.

(10) The separation filter 14, the first porous filter 12 and the second porous filter 16 are completely inserted within the tube.

(11) The tube 2 is surrounded by a heating part 18, which is adapted to increase the temperature. The heating part 18 can be a heating cable, a heating jacket and/or any thermal activation source. The heating part 18 is further adjusted to the upstream zone which contains the powder precursor.

(12) It is noted that the upstream zone and the downstream zone of the tube are both surrounded by the heating part 18.

(13) The tube 2 has a cylindrical shape which is featured by a length comprised at least between 300 mm and 400 mm and by a diameter comprised at least between 25 mm and 30 mm. The thickness of the quartz layer is comprised at least between 2 mm and 4 mm.

(14) A vibrator 20 can be positioned outside the tube 2, between the gas inlet 4 and the first porous filter 12. The vibrator 20 is adapted to enhance the fluidization of the particles.

(15) A first valve 22 is positioned between the gas inlet 4 and the vibrator 20 and/or the first porous filter 12. The first valve 22 is useful for controlling the amount of gas and/or the rate of gas which is injected into the quartz tube 2.

(16) A second valve 24 is positioned between the second porous filter 16 and the gas outlet 6. The gas outlet 6 is connected to a pumping system (not shown). The second valve 24 is useful for controlling the effects of the pumping system.

(17) When functioning, the fluidized bed reactor comprises the precursor powder to be sublimated 26 in the upstream zone delimited by the first porous filter 12 and the separation filter 14. The precursor powder to be sublimated 26 is preferentially a metallic precursor. The metallic precursor is composed of a metallic derivative, preferentially functionalized with the ligand acetylacetonate. The metallic derivative is one of titanium, vanadium, iron, chromium, ruthenium, cobalt, iridium, nickel, copper, zinc or manganese.

(18) The amount of the metal precursor 26 is comprised between 1 mg and 10 mg but can be adapted as a function of the reactor volume and/or the quantity of powder to be treated.

(19) After sublimation of the precursor, preferably (organo)metallic, the sublimated powder is then condensed or impregnated on the fluidized solid support 28.

(20) The system is closed and the pumping is applied to (i) check its tightness and (ii) to reach the base pressure of about 5 mbar-20 mbar.

(21) A flow of 50 sccm-1000 sccm (standard cubic centimeters per minute) of neutral gas (N.sub.2), preferentially of 100 sccm-300 sccm, is applied to ensure the fluidization of the solid support 28.

(22) The choice of the neutral gas flow depends on the density of the fluidized powder.

(23) The solid support 28 is a powder of very thin particles (<20 μm). Preferentially, silicon oxide, aluminium oxide, diatomite particles, zeolite can be employed.

(24) Finally, the temperature is finely tuned to remove all the volatile impurities that may be produced in the course of the impregnation process. The temperature at which this step is carried out is known by the skilled person in the art as a function of the materials used in the process. For instance, the temperature is finely tune to release the volatile non-reactive part of the sublimated (organo)metallic precursor. The volatile non-reactive part is the ligand acetylacetonate.

(25) An advantage of the fluidized bed reactor in accordance with the above description is that the impregnation of nanoparticles onto the solid support can be followed by further chemical reactions in situ without opening the inert atmosphere of the reaction media, i.e. without opening the inert atmosphere of the tube. The pressure of the inert gas can be varied and reactive gas can also be introduced. An example of reactive gas is hydrogen which can be used to reduce the metal precursor and forming therefore nanoparticles thin films deposited onto the powder. Another example of reactive gas is acetylene which can be used to grow carbon nanotubes when a catalyst, such as nanoparticles, is impregnated onto a surface. Those one-pot reactions allow a smooth growth of nanoparticles in a controlled fashion. The flux of gas can be precisely controlled as well as the temperature and the time of reaction.

EXAMPLE

(26) Growth of carbon nanotubes (CNTs) on diatomite particles

(27) Diatomite particles have a mean diameter size which is comprised between 1 μm and 10 μm. Up to 5 g of diatomite powder can be treated in one experiment. The particles are thus loaded into the downstream zone of the tube 2.

(28) The fluidization efficiency is followed directly by a visual inspection through the tube 2 which is transparent. The vibrator 20 participates to the fluidization process.

(29) The fluidization process is carried out under a neutral gas, preferentially a nitrogen gas flow.

(30) The flow of neutral gas is stopped during the setting of temperature. The temperature is increased up to 150° C.-190° C. at a ramp of 2° C./min-10° C./min. As the temperature is reached, the impregnation process can start by applying a N.sub.2 gas flow of 50 sccm-100 sccm (standard cubic centimeters per minute).

(31) The process of impregnation is maintained during 1 min-30 min. At this stage, the metallic precursor 26 in the upstream zone is sublimated and the formed gas is condensed directly on the fluidized support composed of the fluidized diatomite powder 28. A homogeneous thin layer (i.e. one or two atomic layers) of metal is thus coated onto the diatomite particles.

(32) The flow of N.sub.2 gas is stopped and a ramp of temperature of 2° C./min-10° C./min is applied to reach a temperature comprised between 500° C. and 1000° C., which is necessary for CNTs growth. It is thus remarkable that this functionalization by carbon nanotubes can be achieved in situ inside the fluidized bed reactor according to the disclosure of the present invention. During this step, the metal catalyst nanoparticles are formed by a mechanism of surface migration due to the excess of thermal energy.

(33) The tube 2 is very resistant and thanks to the first seal 8 and to the second seal 10, no leakage has been detected.

(34) These elevated temperatures are perfectly supported by the tube 2, which when composed of quartz presents a melting point of 1670° C.

(35) As the temperature is reached, a H.sub.2 reduction is applied to reduce the oxide state of the metal nanocatalysts to pure metal nanoparticles. The reduction is obtained by applying a flow of H.sub.2 diluted from 5% to 30% in N.sub.2 during 5 min-30 min. Then H.sub.2 flow is stopped.

(36) After this step, the temperature is maintained constant and a flow of 20% C.sub.2H.sub.2 in N.sub.2 is applied during 10 min-45 min, allowing thus the growth of the carbon nanotubes.

(37) To end the process, a reduced N.sub.2 flow of 30 sccm-50 sccm is applied during the cooling down to room temperature.

(38) The in situ functionalization of diatomite powder by carbon nanotube has been achieved one pot, without letting air and dust to contact the diatomite powder.

(39) Furthermore, the in situ functionalization by atomic layer deposition in the fluidized bed reactor of the present invention provides the formation of a perfect coating of the thin film composed of carbon nanotube onto the substrate (in this case diatomite particles).

(40) Therefore, a biphased system (composed of a mesoporous core, i.e. diatomite particles, and of CNTs) has been produced thanks to the fluidized bed reactor and to the method of the present invention.