Catalytic assemblies containing micrometric ferromagnetic bodies and the use of said assemblies for heterogeneous catalytic reactions

Abstract

The present invention relates to a catalyst assembly for carrying out a heterogeneous catalytic reaction in a predetermined temperature range T, characterized in that it comprises at least one catalyst compound capable of catalyzing said reaction in the temperature range T and an assembly of ferromagnetic material in the form of micrometric particles and / or wires, said ferromagnetic material being heatable by magnetic induction using a field inductor. The present invention also relates to the use of said catalyst assembly for carrying out a heterogeneous catalytic reaction, such as a methanation reaction.

Description

[Technical Field]

[0001] The present invention relates to the field of heterogeneous catalysis, in particular to a catalyst assembly for carrying out gas-solid heterogeneous catalytic reactions and to its use for said catalytic reactions, in particular hydrocarbon synthesis reactions.

[0002] Gas-solid heterogeneous catalytic reactions involve contacting at least one gaseous reactant with a solid catalyst compound. These catalytic processes often require a heating step at high temperatures to carry out the reaction, and are therefore expensive and energy-intensive. Therefore, research has focused on more economical solutions, especially for reactions that are less energy-intensive. [Background technology]

[0003] Among these solutions, US Pat. No. 5,629,493 proposes a heterogeneous catalysis process in which heating is performed by magnetic induction to reach the temperature required for the reaction. More specifically, this process involves contacting the reactants with a catalyst composition containing ferromagnetic nanoparticle components whose surfaces are at least partially composed of compounds that are catalytic for the reaction. The nanoparticle components are heated by magnetic induction to reach the desired temperature range. This heating can be achieved using a field inductor external to the reactor. In this system, the nanoparticles are heated by their own magnetic moment, allowing the catalyst to heat up and the catalytic reaction to begin. In this way, heating begins quickly and with minimal energy input, right in the center of the reactor, resulting in significant savings.

[0004] However, these ferromagnetic nanoparticles require high heating power: for example, 1100-2100 W / g at 100 kHz for FeC nanoparticles (Kale et al., 2004).

[0005] Furthermore, Patent Document 1 places emphasis on optimizing the size of nanometer particles, and suggests a size of ferromagnetic nanoparticle components of 5 nm to 50 nm, with the optimal size being 20 nm in the case of iron.

[0006] The costs of these reactions therefore remain high, especially due to the heating power required and due to the cost of the nanometric catalyst particles, especially magnetic nanoparticles.

[0007] Furthermore, these nanometer-sized materials typically require careful handling.

[0008] Another problem associated with the use of nanoparticles is the change in their heating properties due to, on the one hand, their tendency to sinter during high-temperature reactions, and, on the other hand, changes over time caused by changes in the chemical order within said nanoparticles (changes in structure and local chemical composition). [Prior art documents] [Patent documents]

[0009] [Patent Document 1] International application WO2014 / 162099 [Non-patent literature]

[0010] [Non-Patent Document 1] Kale et al.,Iron carbide or iron carbide / cobalt nanoparticles for magnetically-induced CO2 hydrogenation over Ni / SiRAlOx catalysts,Catal.Sci.Technol.,2019,9,2601 Summary of the Invention

[0011] [Objective of the Invention] Therefore, a first object of the present invention is to overcome the aforementioned drawbacks by proposing a catalytic component that makes it possible to further reduce the cost of these heterogeneously catalyzed reactions while maintaining their reaction performance.

[0012] Another object of the present invention is to propose a catalytic component that makes it possible to reduce the proportion of nanometric particles in the reactor.

[0013] Another object of the present invention is to propose a catalytic component that allows the maintenance of its heating and catalytic properties over a very long period of time and at the same time is suitable for intermittent operation.

[0014] [Detailed Description of the Invention] In search of new savings, the inventors surprisingly discovered that the heating agent does not necessarily have to be in nanometric form, but can be present in the reactor in the form of a micrometric powder or micrometer diameter wires.

[0015] For this purpose, the invention proposes a catalyst assembly for carrying out heterogeneous catalytic reactions in a given temperature range T, said catalyst assembly being characterized in that it comprises a combination of: at least one catalytic compound formed of metal particles and capable of catalyzing said reaction in a temperature range T; and - at least one ferromagnetic body in the form of micrometric particles with a particle size between 1 μm and 1000 μm and / or wires based on iron or iron alloys with a wire diameter between 1 μm and 1 mm, which can be heated by magnetic induction using a field inductor.

[0016] The examples given later in this specification demonstrate the good energy efficiency of the micrometric ferromagnet as a heating agent, in particular the results obtained with the heating agent, which is no longer nanometric but is of much larger size, are comparable to those obtained with the process of WO2014 / 162099.

[0017] According to a first embodiment of the invention, the catalytic assembly is in the form of a powder comprising a mixture of at least one catalytic compound in particulate form and micrometric particles of a ferromagnetic material.

[0018] As regards the micrometric particles of ferromagnetic material, they advantageously have a particle size of 1 μm to 100 μm, preferably 1 μm to 50 μm, more preferably 1 μm to 10 μm, i.e. a size much larger than that of the nanoparticles described in WO 2014 / 162099.

[0019] With the micrometric ferromagnetic particles, which apparently sometimes tend to agglomerate, no sintering is observed and therefore the effect of heating is maintained.

[0020] Said catalyst compound is formed of catalytic metal particles (metal, metal oxide or a combination of the two) arranged on the surface of an oxide forming a support for the catalyst, such as in particular the oxides of the elements (silicon, aluminum, titanium, zirconium, cerium) that make up the catalyst-oxide compound.

[0021] The oxide supports for catalysts are, for example, Al2O3, SiO2, TiO2, ZrO2, CeO2, which constitute catalyst-oxide compounds, in the form of micrometer or nanometer sized powders, which are mixed with ferromagnetic materials in the form of micrometric powders. Thus, the mixture of these powders (catalyst-oxide compounds and particulate ferromagnetic materials) allows the heating agent and the catalyst to come into intimate contact with each other, which allows the catalytic reaction to be initiated quickly on the surface of the catalyst.

[0022] According to a second embodiment of the catalytic assembly of the present invention, the catalytic compound comprises catalytic metal particles (in the form of a metal, a metal oxide or a combination of the two) arranged on the surface of a ferromagnetic body in the form of a wire.

[0023] Advantageously, the ferromagnetic material in the form of a wire comprises steel wool, which comprises wires based on iron or iron alloys, the wire diameter being between 10 μm and 1 millimeter, preferably between 20 μm and 500 μm, more preferably between 50 μm and 200 μm.

[0024] The ferromagnetic material is advantageously based on iron or an iron alloy containing at least 50 wt% iron, preferably at least 80 wt% iron.

[0025] The ferromagnetic material may in particular consist of ultra-fine steel wool, which forms entangled wires made up of at least 90 wt % iron, the diameter of which may be between 50 μm and 100 μm.

[0026] The metal catalyst particles of the catalyst compound can be selected from manganese, iron, nickel, cobalt, copper, zinc, ruthenium, rhodium, palladium, iridium, platinum, tin, or alloys containing one or more of these metals. Preferably, the metal catalyst particles of the catalyst compound are nickel particles or ruthenium particles.

[0027] The present invention also relates to the use of said catalyst assembly for carrying out a heterogeneous catalytic reaction, comprising contacting at least one reactant with said catalyst assembly in a reactor, and heating said ferromagnetic material by magnetic induction by a field inductor external to the reactor so as to catalyze said reaction in a temperature range T.

[0028] Quite surprisingly, steel wool, an inexpensive and readily available material that can be purchased at any hardware store, has proven to be an excellent heating agent. More specifically, very fine (ultrafine) steel wool, with a wire diameter of less than 1 millimeter, is effective in enabling heating of the catalyst by magnetic induction and would also be an excellent support for the catalyst.

[0029] This material is extremely easy to use, has a very long service life, is easily recycled and does not cause pollution.

[0030] The heterogeneously catalyzed reaction is advantageously a hydrocarbon synthesis reaction, more particularly the heterogeneously catalyzed reaction is a hydrogenation reaction of gaseous carbon oxides, for example a methanation reaction starting from carbon dioxide and dihydrogen.

[0031] The invention will be clearly understood from reading the following description of non-limiting exemplary embodiments with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0032] [Figure 1A] 1A is a simplified partial view of a reactor for using a catalyst assembly according to the present invention for a gas-solid heterogeneous catalytic reaction according to the present invention under an upward gas flow, showing the positioning of the catalyst+heating agent assembly in a section of the tubular reactor surrounded by an external magnetic field inductor. [Figure 1B] 1B is a simplified partial view of a reactor for using a catalyst assembly according to the present invention for a gas-solid heterogeneous catalytic reaction according to the present invention under a downward gas flow, showing the positioning of the catalyst+heating agent assembly in a section of the tubular reactor surrounded by an external magnetic field inductor. [Figure 2] Figure 2 is a graph comparing the performance of various ferromagnetic materials (denoted as specific absorption rate (SAR); equivalent to the amount of absorbed energy per unit weight, expressed in watts per gram of material) at 100 kHz under argon, as a function of the applied alternating magnetic field strength, expressed in mT): fine iron powder with a size on the order of 3-5 μm, very fine steel wool (wire diameter greater than 1 mm), and ultra-fine steel wool (wire diameter less than 1 mm, on the order of 100 μm). [Figure 3] FIG. 3 is a graph showing the results of using a catalyst assembly according to the present invention in a methanation reaction using iron powder as the heating agent and a Ni catalyst on SiRAlOx™ (silicon aluminum oxide from SESAL). [Figure 4] Figure 4 shows histograms of CO2 and CH4 conversion (%) and selectivity as a function of time and temperature for the downflow methanation reaction in the presence of iron powder and a mixture of Ni / CeO2. [Figure 5] FIG. 5 is a histogram showing the percent conversion of CO2 and CH4 and the selectivity as a function of time and temperature for the downflow methanation reaction in the presence of a mixture of steel wool and Ni / CeO2. [Figure 6]FIG. 6 is a histogram showing the percent conversion of CO2 and CH4 and the selectivity as a function of time and temperature for the downflow methanation reaction in the presence of nickel on steel wool. [Figure 7] FIG. 7 is a graph comparing the energy efficiency (expressed in %) as a function of temperature for the three catalyst assemblies forming the catalyst beds tested in the examples shown in FIGS. [Example]

[0033] Example 1: Preparation of the catalyst Preparation of catalysts on cerium oxide supports 10 wt% nickel on cerium oxide (abbreviated as Ni(10 wt%) / CeO2) is prepared by decomposing Ni(COD)2 in the presence of CeO2 in mesitylene.

[0034] According to the conventional preparation method, 1560 mg of Ni(COD)2 was dissolved in 20 mL of mesitylene, followed by the addition of 3 g of CeO2. The resulting mixture was heated under argon atmosphere at 150 °C for 1 h with vigorous stirring. The mixture was initially milky white and turned black upon completion of the reaction. After decantation, the translucent supernatant was removed, and the resulting particles were washed three times with 10 mL of toluene. The toluene was then removed under vacuum, yielding a dense powder of Ni (10 wt%) / CeO2 (3.5 g). This was collected and stored in a glove box. Analysis using inductively coupled plasma mass spectrometry (ICP-MS) confirmed a loading of 9 wt% (target 10%) of nickel on cerium oxide. Observation by transmission electron microscopy (TEM) and EDS analysis indicated the presence of small, monodisperse particles of nickel (2–4 nm in size).

[0035] Preparation process of Ni on SiRAlOx In a Fischer-Porter bottle, under an inert atmosphere, 0.261 g of Ni(COD)2 is dissolved in 20 mL of mesitylene and 0.500 g of SiRAlOx is added. The mixture is heated to 150 °C with stirring for 1 hour. After returning to ambient temperature, the powder is allowed to settle. The supernatant is then removed and the powder is washed three times with 10 mL of THF. The powder is then dried under vacuum and stored under an inert atmosphere.

[0036] Iron powder + Ni / CeO2 mixture Two grams of iron powder are mixed with one gram of the previously prepared nickel catalyst attached to cerium oxide. Scanning electron microscopy and EDS mapping visualize the iron powder particles, which are on the order of 3-5 μm in size, and confirm that nickel is indeed present on the cerium oxide (CeO).

[0037] Example 2: Preparation of catalyst on steel wool support Ultrafine steel wool (Gerlon, purchased from Castorama). ICP-MS analysis of the ultrafine steel wool reveals that the iron composition is 94.7 wt%. EDS mapping shows the presence of numerous impurities (mainly potassium, manganese, and silicon) on the wool surface. SEM observation allows the wire diameter of the ultrafine steel wool used to be measured. It is approximately 100 μm, and the surface is rough and uneven.

[0038] The experimental procedure for depositing nickel metal onto ultrafine steel wool (tangled wires approximately 100 μm in diameter containing 94.7 wt% iron) is essentially the same as for CeO2. 1560 mg of Ni(COD)2 is dissolved in 100 mL of mesitylene, and 3 g of steel wool is completely immersed. After 1 h of rapid stirring at 150 °C under argon, the mixture is placed in a glove box and the solution (black) is drained. The steel wool itself also turns black. The steel wool is then rinsed with toluene, dried under vacuum for 30 min, and stored in the glove box. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) observations reveal that polydisperse nickel particles (100 nm to 1000 nm) are deposited on the surface of the steel wool wires.

[0039] ICP-MS analysis of three different zones shows varying nickel loadings: 1.23%, 1.44%, and 1.33% (weight percent). The differences between these loadings are very small, and the wool surface appears homogeneous. Nevertheless, the amount of deposited nickel is below the target percentage of 10 wt% Ni.

[0040] Example 3: Methanation reaction: Measurement of conversion rate and calculation of selectivity Methanation Reaction

[0041] [ka]

[0042] This is a combination of:

[0043] [ka]

[0044] and,

[0045] [ka]

[0046] This is carried out in a quartz fixed-bed tubular continuous reactor 1 (Avitec) (inner diameter: 1 cm, the height of the catalyst bed 4 varies depending on the heating element, approximately 2 cm, located on a sintered glass 3) (see Figure 1); the gas flow can be either upflow 6 (Figure 1A) or downflow 7 (Figure 1B). The coil 2 used (Five Celes) is a solenoid with an inner diameter of 40 mm and a height of 40 mm, which constitutes an external magnetic field inductor connected to a generator. The resonant frequency is 300 kHz, and the magnetic field is 10-60 mT. The coil 2 is water-cooled.

[0047] Measurement of conversion and selectivity as a function of temperature is performed by temperature servo control of the generator associated with coil 2. For this purpose, a temperature probe 5 connected to the generator is embedded in the catalyst bed (heating agent + catalyst assembly). The generator sends a magnetic field to reach a certain temperature and then pulses only to maintain this temperature. The reaction is carried out at atmospheric pressure and temperatures between 200 °C and 400 °C. Reactor 1 is supplied with H2 and CO2 (their flows are controlled by a Brooks flow meter) and is controlled by LabView software. The ratios are as follows: a total constant flow of 25 mL / min includes 20 mL / min of H2 and 5 mL / min of CO2. The feed is introduced at the top of the reactor, and the produced water condenses at the bottom of the reactor (without a condenser) and is collected in a round-bottom flask. The produced methane and remaining gases (CO2 and H2), as well as CO, are sent to a gas chromatography column (Perkin Elmer, Clarus 580 GC column). The CO2 conversion, CH4 selectivity, and CO and CH4 yields are calculated according to the following formulas:

[0048]

number

[0049] FC is the reaction coefficient of each reactant determined by reaction monitoring using a gas chromatograph. A is the area of ​​the peak as measured by chromatography.

[0050] Energy efficiency measurements: The measurement of energy efficiency is carried out simultaneously with the measurement of the conversion and selectivity of the methanation reaction. The power consumption data of Coil 2 is reconstructed using software developed in the laboratory. The energy efficiency is then calculated according to the following method:

[0051]

number

[0052] PCS (gross calorific value) represents the amount of energy released by the combustion of 1 mg of gas. The values ​​given in the literature are PCS H2 = 141.9 MJ / kg, and PCS CH4 =55.5MJ / kg. Y CH4 is the CH4 yield from the reaction. D mi is the mass flow ratio of product i. E bobine corresponds to the energy consumed by the inductor to operate (i.e., to generate the magnetic field and cool the system). In Figure 7, energy efficiency is expressed in %.

[0053] Example 4: Comparison of various ferromagnetic materials as heating agents Iron powder, extra-fine steel wool, and ultra-fine steel wool were compared. Measurements of the specific absorption rate (SAR) (corresponding to the amount of absorbed energy per unit mass, expressed in watts per gram of material, as a function of the applied alternating magnetic field strength, expressed in mT) were carried out at 100 kHz under argon. The results are summarized in Figure 2.

[0054] These results are significantly different from those obtained in a recent publication by Kale et al., "Iron carbide or iron carbide / cobalt nanoparticles for magnetically-induced CO2 hydrogenation over Ni / SiRAlOx catalysts," Catal. Sci. Technol., 2019, 9, 2601, which reports SAR values ​​of 1100–2100 W / g at 100 kHz for FeC nanoparticles. Figure 2 shows that these values ​​are 10–20 times lower for particulate ferromagnetic materials such as iron powder or steel wool.

[0055] One would expect that fine iron powder and steel wool would require a higher magnetic field than nanoparticles. However, the results in Figure 3 show that this is not the case. Iron carbide nanoparticles require a magnetic field of approximately 48 mT to achieve a yield approaching 90%. Iron powder requires only an 8 mT magnetic field once the reaction has started. A notable feature of iron powder and steel wool is that eddy currents act, reducing the magnetic field required to heat the material.

[0056] Micrometric iron powder and micrometric steel wool therefore constitute advantageous ferromagnetic materials for the in situ heating by magnetic induction of reactors carrying out gas-solid catalytic reactions, such as the methanation reaction starting from carbon dioxide and dihydrogen, as will be shown in the examples below.

[0057] Example 5: Catalyst Assembly: Iron Powder and Catalyst Mixture The catalyst bed consists of nickel particles on cerium oxide: 2 g of iron powder was mixed with 0.09 g of Ni and 0.91 g of CeO. The gas flow was downward and constant (20 mL / min H and 5 mL / min CO).

[0058] The results of the conversion of CO2 and CH4 are shown in Figure 4. This powder assembly (iron powder + Ni / CeO2) allows to obtain very satisfactory yields (Y(CH4)), reaching 100% at temperatures between 300 and 350 °C.

[0059] Example 6: Catalyst Assembly: Mixture of Steel Wool and Ni / CeO Catalyst The catalyst bed consisted of nickel particles attached to cerium oxide: Ni: 0.09 g / CeO2: 0.91 g and 0.35 g of ultrafine steel wool. The gas flow was downward and constant (20 mL / min H2 and 5 mL / min CO2).

[0060] The results of the CO2 and CH4 conversion are shown in Figure 5. This steel wool + Ni / CeO2 assembly allows to obtain very satisfactory yields (Y(CH4)), reaching 100% at temperatures between 300 and 350 °C.

[0061] Example 7: Catalyst Assembly: Ni Deposited on Steel Wool The catalyst bed consisted of 0.03 g of nickel particles attached to 2.27 g of ultrafine steel wool. The gas flow was downward and at a constant rate (20 mL / min H2 and 5 mL / min CO2).

[0062] The CO2 and CH4 conversion results are shown in Figure 6. The maximum yield (Y(CH4)) is 90% at 400 °C. This result is very encouraging as the implementation of this system has proven to be simpler.

[0063] Example 8: Energy Efficiency The energy efficiency calculations for the previous three examples (Examples 5, 6, and 7), summarized in Figure 7, show that less energy needs to be provided to reach the same temperature for a catalyst assembly containing steel wool than for a catalyst assembly containing iron powder. This difference between powder and wool is particularly observed for the steel wool + Ni / CeO2 system. The energy efficiency of the steel wool + Ni catalyst assembly is less favorable, since more wool needs to be heated, which means more energy needs to be provided to produce the same amount of methane. In the presented example, since there is little nickel attached, more steel wool had to be introduced to achieve a favorable yield (90%).

Claims

1. A catalyst assembly for carrying out a heterogeneous catalytic reaction, comprising: said catalytic assembly comprising a combination of at least one catalytic compound formed of metal particles and capable of catalyzing said reaction, and a ferromagnetic material in the form of a micrometric wire based on iron or an iron alloy, with a wire diameter between 1 μm and 1 mm; The ferromagnetic material can be heated by magnetic induction using a field inductor; A catalytic assembly characterized in that the ferromagnetic material in the form of a wire comprises steel wool comprising wires based on iron or iron alloys, the wire diameter being between 20 μm and 500 μm.

2. 2. A catalytic assembly according to claim 1, characterized in that the ferromagnetic material has micrometric particles of 1 μm to 1000 μm.

3. 3. A catalytic assembly according to claim 1 or 2, characterized in that the catalytic compound is formed of metal catalytic particles, of oxides of the elements that constitute the catalytic-oxide compound, placed on the surface of the oxides that form the support for the catalyst.

4. 10. The catalyst assembly of claim 1, wherein the catalyst compound comprises metal catalyst particles disposed on the surface of a ferromagnetic material in the form of a wire.

5. Catalyst assembly according to claim 1, characterized in that the ferromagnetic material in the form of a wire comprises steel wool, which comprises wires based on iron or iron alloys, the wire diameter being between 50 μm and 200 μm.

6. 6. A catalytic assembly according to any one of claims 1 to 5, characterized in that the ferromagnetic material is based on iron or an iron alloy containing iron.

7. 7. A catalytic assembly according to any one of claims 1 to 6, characterized in that the ferromagnetic material is made of ultrafine steel wool, comprising entangled wires made of at least 90 wt% iron, the diameter of the wires being between 50 μm and 100 μm.

8. 5. A catalytic assembly according to claim 3 or 4, characterized in that the metal catalytic particles of the catalytic compound are selected from manganese, iron, nickel, cobalt, copper, zinc, ruthenium, rhodium, palladium, iridium, platinum, tin, or alloys containing one or more of these metals.

9. 9. A catalyst assembly according to claim 8, characterized in that the metal catalyst particles of the catalyst compound are nickel or ruthenium particles.

10. Use of a catalyst assembly according to any one of claims 1 to 9 for carrying out heterogeneously catalytic reactions, comprising 1. Use comprising contacting at least one reactant with said catalyst assembly in a reactor (1), and heating said ferromagnetic material by magnetic induction with a field inductor external to the reactor so as to catalyze said heterogeneous catalytic reaction.

11. 11. Use according to claim 10, characterized in that the heterogeneously catalyzed reaction is a hydrocarbon synthesis reaction.

12. 12. The use according to claim 10 or 11, wherein the heterogeneously catalyzed reaction is the hydrogenation of gaseous carbon oxides.

13. Catalyst assembly according to claim 1, characterized in that the ferromagnetic material comprises micrometric particles with a size between 1 μm and 100 μm.

14. Catalyst assembly according to claim 1, characterized in that the ferromagnetic material comprises micrometric particles with a size between 1 μm and 50 μm.

15. Catalyst assembly according to claim 1, characterized in that the ferromagnetic material comprises micrometric particles with a size between 1 μm and 10 μm.

16. 7. A catalytic assembly according to claim 6, characterized in that the ferromagnetic material is based on iron or an iron alloy containing at least 50 wt. % iron.

17. 7. A catalytic assembly according to claim 6, characterized in that the ferromagnetic material is based on iron or an iron alloy containing at least 80 wt. % iron.

18. A catalytic assembly as claimed in claim 3, characterized in that the oxides are oxides of the following: silicon, aluminum, titanium, zirconium, cerium.

19. The use according to claim 12, wherein the heterogeneous catalytic reaction is a methanation reaction using carbon dioxide and dihydrogen as starting materials.

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