Chemical method catalysed by ferromagnetic nanoparticles

Abstract

A method for the heterogeneous catalysis of a chemical reaction using, in a reactor, at least one reagent and a catalytic composition that can catalyze the reaction within a given range of temperatures T. At least one reagent is brought into contact with the catalytic composition which includes a ferromagnetic nanoparticulate component whose surface is formed at least partially by a compound that is a catalyst for the reaction; the nanoparticulate component is heated by magnetic induction in order to reach a temperature within the range of temperatures T; and the reaction product(s) formed on the surface of the nanoparticulate component are recovered. A catalytic composition includes a ferromagnetic nanoparticulate component that can be heated by magnetic induction to the reaction temperature, whose surface thereof is at least partially formed by a catalyst compound for the reaction. The catalyst is heated by the effect of the magnetic field.

Claims

1. A process for the gas-solid heterogeneous catalysis of a chemical reaction of conversion of a carbon oxide, using, in a reactor, at least one reactant in a gaseous state and a solid catalytic composition for catalyzing said reaction in a given range of temperatures T, the process comprising: bringing said at least one reactant into contact with said catalytic composition, said catalytic composition comprising a ferromagnetic nanoparticulate component, the surface of which consists, at least partly, of a compound that is a catalyst for said chemical reaction, heating said nanoparticulate component by magnetic induction in order to reach a temperature within said range of temperatures T, and recovering the reaction product(s) that are formed at the surface of said nanoparticulate component.

2. The process according to claim 1, wherein said nanoparticulate component is heated by magnetic induction using a field inductor external to the reactor.

3. The process according to claim 1, wherein the magnetic field generated by induction has an amplitude of between 1 mT and 100 mT, and a frequency of between 20 kHz and 400 kHz.

4. The process according to claim 1, wherein said nanoparticulate component consists of at least one ferromagnetic metal compound which is also a catalyst for said chemical reaction.

5. The process according to claim 1, wherein said nanoparticulate component consists of at least one ferromagnetic metal compound that forms a core which is associated with a catalytic metal for said chemical reaction.

6. The process according to claim 4, wherein said ferromagnetic metal compound has a magnetic anisotropy of less than 810.sup.4 J.Math.m.sup.3.

7. The process according to claim 1, wherein the size of said ferromagnetic nanoparticulate component is such that the diameter D of said ferromagnetic nanoparticulate component, expressed in nanometers, is defined by the relationship: $D=N\sqrt{\frac{T_C}{K}}$ where 80N200, T.sub.C is the Curie temperature of the ferromagnetic material in Kelvin, and K is the magnetic anisotropy of the ferromagnetic nanoparticulate component in J.Math.m.sup.3.

8. The process according to claim 1, wherein the size of said ferromagnetic nanoparticulate component is between 5 nm and 50 nm.

9. The process according to claim 4, wherein said at least one ferromagnetic compound which is also a catalyst is selected from the group consisting of iron, cobalt, nickel, and oxides, carbides and alloys thereof.

10. The process according to claim 5, wherein said at least one ferromagnetic metal compound that forms a core is selected from the group consisting of iron and iron carbides, and said catalytic metal is completely or partly covering said core and is selected from the group consisting of ruthenium, manganese, cobalt, nickel, copper and zinc.

11. The process according to claim 1, wherein said reactor is manufactured from non-ferromagnetic materials.

12. The process according to claim 1, wherein said chemical reaction is a reaction for synthesizing a hydrocarbon by gas-solid catalysis.

13. The process according to claim 1, wherein said chemical reaction is a hydrogenation reaction of a carbon oxide in the gaseous state, catalyzed by nanoparticles heated by magnetic induction.

14. The process according to claim 1, wherein said ferromagnetic nanoparticulate component comprises at least a ferromagnetic metal compound selected from the group consisting of iron and iron carbides.

Description

(1) The present invention will be better understood, and details relating thereto will appear, owing to the description which will be given of embodiment variants, in connection with the appended figures, in which:

(2) FIG. 1 is a simplified diagram of a catalysis reactor according to the invention.

(3) FIG. 2 shows iron nanoparticles according to the invention seen by transmission electron microscopy (FIG. 2a) and x-ray diffraction (FIG. 2b).

(4) FIG. 3 is the mass spectrum of the products of a Fischer-Tropsch reaction catalyzed by iron nanoparticles according to the invention.

(5) FIG. 4 is the mass spectrum of the products of a reaction for activation of CO by H.sub.2, catalyzed by Fe/FeC/Ru nanoparticles according to the invention.

(6) FIGS. 5 and 6 are mass spectra of the products obtained after a second and third reaction for activation of CO by H.sub.2, catalyzed by the same Fe/FeC/Ru nanoparticles.

(7) FIG. 7 is the mass spectrum of the products of a reaction for activation of CO.sub.2 by H.sub.2 catalyzed by Fe/FeC/Ru nanoparticles according to the invention.

EXAMPLE 1

Reactor for Gas-Solid Heterogeneous Catalysis Process

(8) The process for catalysis of a chemical reaction according to the invention may be carried out in a furnace using at least one gaseous reactant, and a catalytic composition according to the invention. The furnace presented in FIG. 1 comprises a chamber (100), comprising an inlet (1) for reactant gases and an outlet (2) for produced gases. The chamber comprises an inner wall (5) formed from a pressure-resistant, non-magnetic, chemically inert material that is preferably electrically insulating (glass, ceramic, plastic), and preferably also a thermally insulating outer wall (6). The chamber is provided with a system for generating an electric field such as a coil (7), or an electromagnet.

(9) The chosen catalytic ferromagnetic composition (3) is introduced into the chamber. It is retained at the outlet by the grid (4) that allows the passage of the gases, but not of the nanoparticles that form said composition.

EXAMPLE 2

Synthesis of an Fe(0) Nanoparticulate Catalyst

(10) A glass Fisher-Porter bottle was used as reactor. It is loaded in a glovebox with a solution of 376.5 mg (1 mmol) of {Fe[N(SiMe.sub.3).sub.2].sub.2}.sub.2 iron complex dimer in 20 ml of mesitylene. Added to this solution are 415.5 mg (i.e. 1.5 mmol) of HDAHCl (hexadecylammonium chloride), then the solution is homogenized for 5 minutes at ambient temperature. The color changes from light green to dark yellow and then to brown. After homogenization, 483.0 mg (2 mmol) of HDA (hexadecylamine) are added. The reaction medium thus formed is heated at 150 C. for 2 days. The black powder formed is recovered by magnetic settling and washed 5 times with toluene (515 ml). Transition electron microscopy (TEM) correlated to x-ray diffraction shows the formation of purely metallic Fe(0) nanoparticles of somewhat cubic shape (presented in FIG. 2).

(11) The Curie temperature of the material is Tc=1043 K. The anisotropy of the iron nanoparticles is estimated at K=710.sup.4 J/m.sup.3, with N=88.5, the diameter D=10.8 nm with a standard deviation of 0.9 nm.

EXAMPLE 3

Fischer-Tropsch Catalysis by Fe(0) Nanoparticles

(12) A Fisher-Porter bottle is loaded under an argon atmosphere with around 10 mg of Fe(0) nanoparticles obtained in example 2. After having created a vacuum in the bottle, the latter is pressurized at ambient temperature with an equivalent amount of CO and H.sub.2 bringing the pressure of the system to 1.85 bar of gas. The pressure of the system is controlled using a manometer placed over the top of the Fisher-Porter bottle. The body of the bottle is then placed inside a coil which generates an alternating magnetic field having a frequency of 60 kHz and an amplitude of 56 mT (28 A) for a duration of 230 min (and a waiting time between the two of 10 min). The rise in temperature is rapid.

(13) At the end of the reaction, the gas contained in the bottle is analyzed by mass spectrometry. The conversion of the gas added is complete. The analysis of the spectrum shows the presence of hydrocarbons ranging from C1 to C3, residual CO and H.sub.2 and the presence of water (see FIG. 3).

EXAMPLE 4

Synthesis of Fe/FeC/Ru Nanoparticulate Catalysts

(14) A glass Fisher-Porter bottle was used as reactor. It is loaded in a glovebox with a solution of 376.5 mg (1 mmol) of {Fe[N(SiMe.sub.3).sub.2].sub.2}.sub.2 iron complex dimer in 20 ml of mesitylene. Added to this solution are 415.5 mg (i.e. 1.5 mmol) of HDAHCl (hexadecylammonium chloride), then the solution is homogenized for 5 minutes at ambient temperature. The color changes from light green to dark yellow and then to brown. After homogenization, 483.0 mg (2 mmol) of HDA (hexadecylamine) are added. The reaction medium thus formed is heated at 150 C. for 2 days. Added to this solution are 42.6 mg (0.066 mmol) of Ru.sub.3(CO).sub.12 and the reaction medium is again homogenized under magnetic stirring for 30 minutes at 90 C. Next, the solution is pressurized at ambient temperature for 10 minutes at 3 bar of hydrogen. It is then heated at 150 C. for 24 h. The black powder formed is recovered by magnetic settling and washed 5 times with toluene (515 ml).

(15) The various methods of transmission electron microscopy (TEM, HRTEM, STEM and EDX), correlated to x-ray diffraction, indicate the formation of core-shell type nanoparticles of spherical shape, comprising an Fe(0) core of around 10.0 nm (0.9 nm), and a polycrystalline shell of around 0.5 nm of iron carbides doped with 5% to 7% of ruthenium.

(16) The anisotropy of the nanoparticles thus obtained is estimated at around 5.510.sup.4 J/m.sup.3 for the FeC particles. The diameter of the particles D=11.6 nm with a standard deviation of 0.9 nm. The initial Curie temperature of the material is Tc=1043 K. The anisotropy of the FeC nanoparticles is estimated at K=5.510.sup.4 J/m.sup.3, N=84.2 and D=11.6 nm (0.9 nm).

EXAMPLE 5

Hyperthermia Properties

(17) The heat dissipated by the nanoparticles obtained in example 4 when they are placed in an alternating magnetic field is determined, in order to demonstrate their hyperthermia properties. Studies of the hyperthermia properties (SAR=power dissipated) of a system of ferromagnetic nanoparticles may be carried out by measuring the increase in the temperature of the nanoparticles under the effect of an alternating magnetic field. In order to do this, we have developed a hyperthermia measurement bench, which operates in a relatively broad range of sinusoidal magnetic field having an amplitude that varies from 0-60 mT and having a frequency of 2-100 kHz.

(18) A vial containing around 10 mg of nanoparticle powder obtained in example 3, prepared under an inert atmosphere to avoid any oxidation, is placed in a calorimeter containing 1.5 ml of water. The temperature of the water is measured by using a fiber optic temperature sensor. The measurement time is chosen at between 30 s and 100 s, as a function of the experimental parameters, so that the rise in temperature never exceeds 20 C. The rise in temperature at the end of the application of the magnetic field is measured after stirring the calorimeter to ensure the homogeneity of the temperature. The power dissipated (SAR) by the nanoparticles is then calculated, according to the formula:

(19) $\mathrm{SAR}=\frac{\underset{i}{.Math.}{C}_{\mathrm{pi}}{m}_i}{m_{\mathrm{Fe}}}\frac{T}{t}$
where C.sub.pi and m.sub.i are respectively the specific heat capacities and the masses of each component (C.sub.p=449 J.Math.kg.sup.1.Math.K.sup.1 for the Fe nanoparticles, C.sub.p=1750 J.Math.kg.sup.1.Math.K.sup.1 for mesitylene, C.sub.p=4186 J.Math.kg.sup.1.Math.K.sup.1 for water and C.sub.p=720 J.Math.kg.sup.1.Math.K.sup.1 for glass). The denominator m.sub.Fe is the metallic mass of the sample.

(20) The value of the SAR obtained at 54 KHz for the Fe/FeC/Ru nanoparticles described above is 250 W.Math.g.sup.1, power sufficient to attain the temperatures necessary for the catalysis.

EXAMPLE 6

Activation of CO by H2 by FeFeCRu Nanoparticles

(21) A glass Fisher-Porter bottle is loaded in a glovebox with around 10 mg of Fe/FeC/Ru nanoparticulate catalyst obtained in example 4. After having created a vacuum in the bottle, the latter is pressurized at ambient temperature with 1 bar of carbon monoxide and 4 bar of dihydrogen, bringing the pressure of the system to 5 bar of gas. The pressure of the system is controlled using a manometer placed over the top of the Fisher-Porter bottle. The body of the bottle is then placed inside the coil which generates the alternating magnetic field having a frequency of 60 kHz and an amplitude of 56 mT (28 A) for a duration of 5 h. The pressure inside the bottle reaches 2.1 bar at the end of the experiment, i.e. a loss of 3 bar. At the end of the reaction, the gas contained in the bottle is analyzed by mass spectrometry. The analysis of the spectrum shows the presence of hydrocarbons ranging from C1 to C4-C5, residual CO and H.sub.2 and the presence of water (FIG. 4).

(22) It is interesting to note that after the first experiment, the catalyst has been recycled and tested again under the same conditions. After 3 h of magnetic heating, a pressure loss of 2 bar (compared to 3 bar previously) and the formation again of hydrocarbons ranging from C1 to C4 (FIG. 5) are noted. The second recycling of the catalyst results in a loss of only 1 bar after 3 h of reaction and formation of hydrocarbons ranging from C1 to C3 (FIG. 6).

(23) It is thus verified that after the first catalytic cycle, the ferromagnetic and catalytic nanoparticles are still active. A layer of carbon is obtained and the catalyst is not killed. The catalyst is still living, and it can be recycled.

EXAMPLE 7

Fischer-Tropsch Catalysis by Fe(0) Nanoparticles

(24) A glass Fisher-Porter bottle is loaded under an argon atmosphere with around 10 mg of Fe/FeC/Ru nanoparticles obtained in example 4. After having created a vacuum in the bottle, the latter is pressurized at ambient temperature with an equivalent amount of CO.sub.2 and H.sub.2, bringing the pressure of the system to 4 bar of gas. The pressure of the system is controlled using a manometer placed over the top of the Fisher-Porter bottle. The body of the bottle is then placed inside a coil which generates an alternating magnetic field having a frequency of 300 kHz and an amplitude of 80 mT for a duration of 4 h.

(25) At the end of the reaction, the gas contained in the bottle is analyzed by mass spectrometry. The conversion of the gas added is complete. The analysis of the spectrum shows the presence of methane (CH.sub.4), residual CO and H.sub.2 and also the presence of water (see FIG. 7).