Method of heterogeneous catalysis using ferromagnetic bodies heated by magnetic induction and support for catalysts used in said method

Abstract

The present invention relates to a method for heterogeneous catalysis of a hydrogenation reaction of gaseous carbon oxides, such as a methanation reaction, using carbon dioxide and gaseous dihydrogen in a reactor (1) and at least one catalytic solid compound capable of catalyzing said reaction in a predetermined temperature range T, the method comprising contacting said gaseous reactants and said catalytic compound in the presence of a heating agent and heating said heating agent to a temperature within said temperature range T. The method is characterized in that the heating agent comprises a ferromagnetic material in the form of a micrometric powder and / or wire, said ferromagnetic material being heated by magnetic induction by a field inductor such as a coil (2) external to the reactor (1). According to one embodiment, a support for a catalyst for carrying out the method comprises a ferromagnetic material in the form of a wire with a micrometric diameter, on the surface of which metal catalyst particles are attached.

Description

[Technical Field]

[0001] The present invention relates to the field of heterogeneous catalysis, and in particular to a process of gas-solid heterogeneous catalysis comprising contacting at least one gaseous reactant with a catalytic solid compound disposed on a support. The present invention also relates to a support for said catalyst.

[0002] A great many processes require heterogeneous catalysis. These catalytic processes require a heating step, sometimes 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 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, the cost of these reactions remains high, especially due to the cost of the nanometer-sized catalyst particles, more specifically magnetic nanoparticles. Furthermore, these nanomaterials usually have to be handled with care.

[0005] 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]

[0006] [Patent Document 1] International application WO2014 / 162099 Summary of the Invention

[0007] [Objective of the Invention] Therefore, a primary object of the present invention is to overcome the aforementioned drawbacks by further reducing the cost of these heterogeneously catalyzed reactions while maintaining their reaction performance.

[0008] Another object of the invention is to propose a process that makes it possible to reduce the proportion of components in the form of nanometric particles in the reactor.

[0009] Another object of the present invention is to propose a process of heterogeneous catalysis that exhibits maintenance of heating and catalytic properties over a very long period of time, while at the same time being suitable for intermittent operation.

[0010] Another object of the present invention is to propose a process for the catalysis of gas-solid chemical reactions, more particularly hydrogenation reactions of gaseous carbon oxides, such as methanation reactions.

[0011] [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 wire.

[0012] To this end, the present invention proposes a process for heterogeneous catalysis of the hydrogenation reaction of gaseous carbon oxides, such as methanation, using carbon dioxide and gaseous dihydrogen in a reactor and at least one solid catalytic compound capable of catalyzing said reaction in a predetermined temperature range T, the process comprising contacting the gaseous reactants and the catalytic compound in the presence of a heating agent and heating the heating agent to a temperature within said temperature range T. This process is characterized in that the heating agent contains a ferromagnetic material in the form of a micrometric powder consisting of micrometric ferromagnetic particles having a size between 1 μm and 1000 μm and / or wires based on iron or iron alloys, preferably with a wire diameter between 10 μm and 1 mm. The ferromagnetic material is heated by magnetic induction using a field inductor external to the reactor, the magnetic field generated by the field inductor external to the reactor having an amplitude between 1 mT and 80 mT and a frequency between 30 kHz and 500 kHz. 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, which uses ferromagnetic nanoparticle components.

[0013] According to the first embodiment of the invention, when present in powder form, the ferromagnetic material advantageously consists of micrometric ferromagnetic particles having a size between 1 μm and 100 μm, preferably between 1 μm and 50 μm, more preferably between 1 μm and 10 μm.

[0014] With the micrometric ferromagnetic particles, which apparently sometimes tend to agglomerate, no sintering is observed and therefore the effect of heating is maintained.

[0015] As regards the catalyst compound used in the process according to the invention, said catalyst compound comprises a catalyst for heterogeneous catalytic reactions in the form of metal particles arranged on a support.

[0016] The metal catalyst particles are advantageously chosen from manganese, iron, nickel, cobalt, copper, zinc, ruthenium, rhodium, palladium, iridium, platinum, tin, or alloys containing one or more of these metals.

[0017] The metal catalyst particles are arranged on the surface of an oxide forming a support for the catalyst, for example an oxide of at least one element of silicon, cerium, aluminum, titanium or zirconium (e.g., Al2O3, SiO2, TiO2, ZrO2, CeO2), and are in the form of a powder of micrometer or nanometer size, constituting a catalyst-oxide ensemble that is mixed with a ferromagnetic material in the form of a micrometric powder. Thus, the mixing of these powders (catalyst-oxide ensemble and particulate ferromagnetic material) allows for an intimate contact between the heating agent and the catalyst, which allows for a rapid initiation of the catalytic reaction on the surface of the catalyst.

[0018] According to a second embodiment of the invention, the support for the catalyst is said ferromagnetic material in the form of a wire.

[0019] Advantageously, the ferromagnetic material in the form of a wire that is a support for the catalyst can comprise or consist essentially of steel wool, including wires based on iron or iron alloys, preferably with a wire diameter between 20 μm and 500 μm, more preferably between 50 μm and 200 μm.

[0020] In fact, 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 an excellent support for catalysts and is effective in enabling heating of the catalyst by magnetic induction.

[0021] This material is extremely easy to use, has a very long service life, is easily recycled and does not cause pollution.

[0022] The process according to the invention is advantageously a hydrocarbon synthesis reaction, more particularly a heterogeneously catalyzed reaction.

[0023] The heterogeneously catalyzed process according to the invention, the hydrogenation reaction of gaseous carbon oxides, for example the methanation reaction starting from carbon dioxide and dihydrogen, can in particular be carried out using a magnetic field having an amplitude of 1 mT to 50 mT and a frequency of 50 kHz to 400 kHz, preferably 100 kHz to 300 kHz, generated by a field inductor external to the reactor.

[0024] The present invention also relates to a catalyst support for carrying out the above-mentioned heterogeneous catalysis process, characterized in that it comprises a ferromagnetic body in the form of a wire of micrometer diameter on the surface of which metal catalyst particles are attached.

[0025] Advantageously, the ferromagnetic material is based on iron or an iron alloy, preferably containing at least 50 wt% iron, more preferably at least 80 wt% iron.

[0026] The ferromagnetic material can in particular consist of ultra-fine steel wool, which contains entangled wires made of at least 90 wt % iron and has a wire diameter of 10 μm to 1 mm, preferably 20 μm to 500 μm, more preferably 50 μm to 200 μm.

[0027] 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]

[0028] [Figure 1A] 1A is a simplified partial view of a reactor for carrying out the process of gas-solid heterogeneous catalysis according to the present invention under upward gas flow, showing the positioning of the catalyst+heating agent assembly in the section of the tubular reactor surrounded by an external magnetic field inductor. [Figure 1B] 1B is a simplified partial view of a reactor for carrying out the process of gas-solid heterogeneous catalysis according to the present invention under downward gas flow, showing the positioning of the catalyst+heating agent assembly in the section of the tubular reactor surrounded by an external magnetic field inductor. [Figure 2] FIG. 2 is a graph comparing the performance of various heating agents according to the invention, performed at 100 kHz under argon (specific absorption rate (SAR); corresponds 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): fine iron powder of the order of 3-5 μm in size, 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 a methanation process according to the present invention 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 downflow methanation reactions in the presence of iron powder and Ni / CeO2 mixtures. [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 types of catalyst beds (catalyst + heating agent) tested in the examples shown in FIGS. [Example]

[0029] 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.

[0030] 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).

[0031] 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.

[0032] 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).

[0033] 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.

[0034] 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.

[0035] 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.

[0036] Example 3: Methanation reaction: Measurement of conversion rate and calculation of selectivity Methanation Reaction

[0037] [ka]

[0038] This is a combination of:

[0039] [ka]

[0040] and,

[0041] [ka]

[0042] 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.

[0043] 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:

[0044]

number

[0045] 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.

[0046] 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:

[0047]

number

[0048] 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 %.

[0049] Example 4: Comparison of various 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] Example 5: 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).

[0054] 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.

[0055] Example 6: Mixture of steel wool and Ni / CeO2 catalyst The catalyst bed consisted of nickel particles attached to cerium oxide: Ni: 0.09 g / CeO2: 0.91 g and 0.35 g (ultrafine) steel wool. The gas flow was downward and at a constant rate (20 mL / min H2 and 5 mL / min CO2).

[0056] The results of the CO2 and CH4 conversion are shown in Figure 5. This steel wool + Ni / CeO2 assembly allows to obtain a very satisfactory yield (Y(CH4)), reaching 100% at temperatures between 300 and 350 °C.

[0057] Example 7: Ni catalyst attached to 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 flow rate (20 mL / min H2 and 5 mL / min CO2).

[0058] 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.

[0059] 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 for the steel wool system than for the iron powder system to reach the same temperature. This difference between powder and wool is particularly observed for the steel wool + Ni / CeO2 system. The energy efficiency of the steel wool + Ni system 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 examples presented, since very little nickel is deposited, a large amount of steel wool had to be introduced to achieve a favorable yield (90%).

Claims

1. 1. A process for heterogeneous catalysis of the hydrogenation reaction of gaseous carbon oxides, comprising: The hydrogenation reaction of gaseous carbon oxide is carried out in a reactor (1) using said carbon oxide and gaseous dihydrogen, and at least one catalytic solid compound capable of catalyzing said reaction in a predetermined temperature range T, contacting the gaseous reactant and the catalyst compound in the presence of a heating agent, and heating the heating agent to a temperature within the temperature range T; A process characterized by: the heating agent comprises ferromagnetic material in the form of a powder consisting of ferromagnetic particles having a size between 1 μm and 1000 μm and / or wires based on iron or iron alloys; The ferromagnetic material is heated by magnetic induction using a field inductor external to the reactor (1); and The magnetic field generated by a field inductor external to the reactor has an amplitude between 1 mT and 80 mT and a frequency between 30 kHz and 500 kHz.

2. 2. The process according to claim 1, characterized in that the ferromagnetic material in powder form consists of ferromagnetic particles having a size between 1 μm and 100 μm.

3. 3. The process according to claim 1 or 2, characterized in that the ferromagnetic material in powder form consists of ferromagnetic particles having a size between 1 μm and 50 μm.

4. 4. The process according to claim 1, wherein the catalyst compound comprises a catalyst for heterogeneous catalytic reactions in the form of metal particles arranged on a support.

5. 5. The process of claim 4, wherein the metal catalyst particles are selected from manganese, iron, nickel, cobalt, copper, zinc, ruthenium, rhodium, palladium, iridium, platinum, tin, or alloys containing one or more of these metals.

6. 6. A process according to claim 4 or 5, characterized in that the metal catalyst particles are placed on the surface of an oxide forming a support for the catalyst, for example an oxide of at least one of the elements silicon, cerium, aluminum, titanium or zirconium, constituting a catalyst-oxide aggregate in the form of a powder which is mixed with a ferromagnetic material in the form of a powder.

7. 7. The process according to any one of claims 4 to 6, characterized in that the support for the catalyst is said ferromagnetic material in the form of a wire.

8. 8. A process according to claim 7, characterized in that the ferromagnetic material in the form of wires that is a support for the catalyst comprises steel wool, including wires based on iron or iron alloys.

9. 9. The process according to any one of claims 1 to 8, characterized in that the magnetic field generated by a field inductor external to the reactor has an amplitude of between 1 mT and 50 mT.

10. 10. The process according to any one of claims 1 to 9, characterized in that the magnetic field generated by a field inductor external to the reactor has a frequency between 50 kHz and 400 kHz.

11. 11. A support for a catalyst for carrying out the process according to any one of claims 7 to 10, characterized in that it comprises a ferromagnetic material in the form of a wire based on iron or an iron alloy, with a wire diameter between 10 μm and 1 mm, on the surface of which metal catalyst particles are attached.

12. 12. The carrier according to claim 11, wherein the ferromagnetic material is based on iron or an iron alloy.

13. 13. The carrier according to claim 11 or 12, characterized in that the ferromagnetic material is made of ultra-fine steel wool containing entangled wires composed of at least 90 wt % iron, and the wire diameter is between 10 μm and 1 mm.

14. 2. The method according to claim 1, characterized in that the wire based on iron or an iron alloy has a wire diameter of between 10 μm and 1 mm.

15. 3. The process according to claim 1 or 2, characterized in that the ferromagnetic material in powder form consists of ferromagnetic particles having a size between 1 μm and 10 μm.

16. 8. The process according to claim 7, characterized in that the ferromagnetic material in the form of wires that is the support for the catalyst comprises steel wool, comprising wires based on iron or iron alloys with a wire diameter between 20 μm and 500 μm.

17. 8. The process according to claim 7, characterized in that the ferromagnetic material in the form of wires that is the support for the catalyst comprises steel wool, comprising wires based on iron or iron alloys with a wire diameter between 50 μm and 200 μm.

18. 10. The process according to any one of claims 1 to 9, characterized in that the magnetic field generated by a field inductor external to the reactor has a frequency between 100 kHz and 300 kHz.

19. 12. The carrier according to claim 11, wherein the ferromagnetic material is based on iron or an iron alloy containing at least 50 wt% iron.

20. 12. The carrier according to claim 11, wherein the ferromagnetic material is based on iron or an iron alloy containing at least 80 wt% iron.

21. 13. The carrier according to claim 11 or 12, characterized in that the ferromagnetic material is made of ultra-fine steel wool containing entangled wires composed of at least 90 wt % iron, and the wire diameter is 20 μm to 500 μm.

22. 13. The carrier according to claim 11 or 12, characterized in that the ferromagnetic material is made of ultra-fine steel wool containing entangled wires composed of at least 90 wt % iron, and the wire diameter is 50 μm to 200 μm.

23. The process of claim 1, wherein the hydrogenation reaction is a methanation reaction of carbon dioxide.

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