Method for preparing a generally spherical catalyst precursor material for a methanation reaction, spheres obtained by such a method, methanation method and device
Patent Information
- Application Number
- EP2023738703
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-07-07
- Filing Date
- 2023-07-04
- Publication Date
- 2025-05-14
Smart Images
Figure 1.1
Abstract
Description
[0001] DESCRIPTION
[0002] TITLE OF THE INVENTION: PROCESS FOR PREPARING A GENERALLY SPHERICAL MATERIAL PRECURSOR OF A CATALYST FOR A METHANATION REACTION, SPHERES
[0003] OBTAINED BY SUCH A PROCESS, PROCESS AND METHANATION DEVICE
[0004] Technical field of the invention
[0005] The present invention relates to a method and a device for preparing a precursor material for a methanation reaction catalyst, a material obtained by such a method, a method and a device for a methanation reaction. It applies, in particular, to the field of converting carbon monoxide (CO) and / or carbon dioxide (CO2), in a hydrogen-rich gas mixture, into a methane-rich mixture (CH4), preferably using a fluidized bed reactor.
[0006] State of the art
[0007] For the production of a methane-rich mixture (CH4), from the conversion of carbon monoxide (CO) and / or carbon dioxide (CO2) in a hydrogen-rich gas mixture, also called a methanation reaction, there are reactors using heterogeneous catalysis of the methanation reaction. These heterogeneous catalysis are mainly carried out by catalytic materials based on nickel (Ni) supported on an alumina (AI2O3) support. Methanation reaction reactors generally operate in a fixed catalytic bed or in a fluidized catalytic bed.
[0008] In current systems, the catalytic materials used in fluidized bed methanation reactors do not exhibit good fluidization quality and have limited attrition resistance. Indeed, during the implementation of a methanation reaction in a fluidized bed reactor, attrition of the catalytic material particles, also called degradation, takes place as a result of mechanical stresses inherent to the hydrodynamics of fluidization. In particular, the catalytic material particles form fines following attrition, which leads to a loss of catalytic performance. These mechanical stresses are due, for example, to mechanical shocks between the catalytic material particles, between these particles and the inner wall of the reactor or between these particles and elements present in the reactor, such elements corresponding, for example, to cooling tubes, baffles and / or supports.In fact, this attrition is also the result of the tearing off of angular shapes likely to be present on the catalytic particles.
[0009] Statement of the invention
[0010] The present invention aims to remedy all or part of these drawbacks.
[0011] To this end, according to a first aspect, the invention relates to a method for preparing a generally spherical precursor material for a catalyst for a methanation reaction according to claim 1.
[0012] Thanks to these provisions, the method makes it possible to obtain a generally spherical catalyst precursor material for a methanation reaction having good fluidization quality combined with limited attrition. In particular, such a sphericity factor is conditioned by the step of forming the spherical support. Furthermore, these provisions also make it possible to obtain a catalyst precursor material on an industrial scale and having a high sphericity. Thanks to the mechanical treatment step, an increase in the sphericity of the catalyst material produced by such a method allows a limitation of the angular shapes of the catalytic particles. Thus, the attrition linked to the presence of angular shapes is limited during a methanation reaction in a fluidized bed.
[0013] In embodiments, the mechanical treatment step is carried out in a fluidized bed by passing a gas in contact with the spherical support. Thanks to these arrangements, the method allows an improvement in the quality of the support by eliminating any surface defects before the step of incorporation of the nickel precursor. In particular, the fluidized bed participates in the progressive removal of surface defects from the support. The fluidization therefore achieves a dynamic polishing of the surface of the catalyst. Thus, the sphericity of the support is optimal.
[0014] In embodiments, the mechanical treatment step and the calcination step are simultaneous and preferably carried out in a fluidized bed.
[0015] In embodiments, during the mechanical treatment step carried out in a fluidized bed, the gas in contact with the spherical support is an inert gas.
[0016] In embodiments, during the mechanical treatment step carried out in a fluidized bed, the fluidization rate is at least twice the minimum fluidization speed.
[0017] In embodiments, during the mechanical treatment step carried out in a fluidized bed, the fluidization rate is preferably at least six times greater than the minimum fluidization speed.
[0018] In embodiments, during the mechanical treatment step carried out in a fluidized bed, the fluidization rate is at least ten times greater than the minimum fluidization speed.
[0019] In embodiments, downstream of the fluidized bed mechanical treatment step, the step of incorporating a nickel precursor is also carried out in the fluidized bed reactor.
[0020] In embodiments, the mechanical processing step is performed using a rotating tank configured to generate impacts between the carrier particles.
[0021] In embodiments, the generally spherical support comprises an alumina precursor in the form of a boehmite-type alumina hydrate (of formula AIOOH).
[0022] In embodiments, the incorporation step comprises a step of impregnating the support with a solution comprising the nickel precursor. Thanks to these provisions, the method allows simplified incorporation of the spherical support to be carried out using an easily prepared nickel precursor solution.
[0023] In embodiments, the step of forming the spherical support comprises a granulation step.
[0024] In embodiments, the step of forming the spherical support comprises an atomization step. Thanks to these provisions, the method makes it possible to control the size and the sphericity factor of the spherical support and therefore of the sphere of catalyst precursor material.
[0025] In embodiments, the step of forming the spherical catalytic support comprises a drop coagulation step. Thanks to these provisions, the method makes it possible to control the size and the sphericity factor of the spherical support and therefore of the sphere of catalyst precursor material. In addition, the equipment used to implement the method is less bulky and the energy consumption is reduced. Thus, the cost of carrying out the method is reduced. According to a second aspect, the invention relates to a device for preparing generally spherical catalyst precursor material for a methanation reaction, which comprises:
[0026] - a means of forming a generally spherical support comprising mesoporous alumina (AI2O3) or an alumina precursor,
[0027] - a means of incorporating a nickel precursor into the support comprising mesoporous alumina (AI2O3) or an alumina precursor, by bringing a composition comprising the nickel precursor (Ni) into contact with the support,
[0028] - a means for calcining the support incorporating the nickel precursor, configured to at least partially transform the nickel precursor into nickel oxide (NiO) and the alumina precursor into alumina, and configured to form a solid of generally spherical shape, said solid being nicknamed "sphere of precursor material of a catalyst of a methanation reaction", and a means for mechanical treatment of the spherical support, downstream of the formation of the support, to increase the sphericity factor of the spherical support.
[0029] The aims, advantages and particular characteristics of the device which is the subject of the invention being similar to those of the method which is the subject of the invention, they are not repeated here.
[0030] According to a third aspect, the invention relates to spheres of precursor material for a catalyst for a methanation reaction, obtained by the process which is the subject of the invention, which comprise nickel oxide (NiO) and mesoporous alumina (AI2O3), the respective proportions of which are, relative to the total mass of these two compounds:
[0031] - NiO: 1 to 50% by mass and
[0032] - AI2O3: 50 to 99% by mass.
[0033] Thanks to these provisions, the catalyst precursor material spheres, when activated and used in a fluidized bed methanation reaction, exhibit good hydrodynamic properties and high mechanical strength. Thus, good fluidization of the catalytic bed, limitation of sphere attrition and reduction of fines production are obtained. The catalytic activity of the metal incorporated in the spheres, during the fluidized bed methanation reaction, is therefore optimal. In addition, the increase in mechanical strength makes it possible to extend the service life of the spheres in the fluidized bed methanation reaction by reducing in particular the detachment of the active metal species from the support.
[0034] In embodiments, the catalyst precursor material spheres have a monomodal particle size with a median diameter of between 100 and 1000 pm, preferably between 200 and 800 pm and more preferably between 250 and 350 pm. Thanks to these arrangements, the monomodal particle size of the activated spheres used in a fluidized bed methanation reaction allows optimal fluidization.
[0035] In embodiments, the alumina (AI2O3) has a gamma or delta structure. Thanks to these arrangements, the alumina of the spherical support has a structure particularly suitable for implementing catalysis of a methanation reaction.
[0036] In embodiments, the alumina (AI2O3) has a mesoporosity corresponding to a median pore diameter, determined by Hg intrusion porosimetry, of between 3 and 50 nm and preferably between 5 and 25 nm.
[0037] In embodiments, the catalyst precursor material spheres have a specific surface area of between 50 and 300 m 2 / g and preferably between 100 and 250 m 2 / g. According to a fourth aspect, the invention relates to a methanation process, which comprises:
[0038] - a step of activating, at least partially, into spheres of catalytic material, spheres of catalyst precursor material which are the subject of the invention and
[0039] - a step of passing a gas comprising hydrogen (H2) and at least carbon monoxide (CO) and / or carbon dioxide (CO2) into contact with the spheres of catalytic material.
[0040] Thanks to these provisions, the method allows the use of the catalyst precursor material spheres which are the subject of the invention in a methanation reaction, after activation into catalytic material spheres.
[0041] In embodiments, the method comprises, upstream of the gas passage step, a gas constitution step comprising at least one of the following steps:
[0042] - pyrolysis of hydrocarbon materials,
[0043] - pyro-gasification of hydrocarbon materials
[0044] - gasification of hydrocarbon materials,
[0045] - co-electrolysis of CO2 / H2O,
[0046] - reaction of gas with water,
[0047] - reverse reaction of gas to water,
[0048] - a stage of production of a hydrogen-rich gas,
[0049] - a stage of production of a gas rich in CO2 and
[0050] - a step of introducing steam into the gas.
[0051] Thanks to these provisions, it is possible to recover a gas obtained during an intermediate stage.
[0052] In embodiments, during the step of passing the gas into contact with the spheres of catalytic material, the gas passes through a fluidized bed of spheres of catalytic material. Thanks to these provisions, the method allows the use of the spheres of catalyst precursor material which are the subject of the invention in a methanation reaction in a fluidized bed, after activation into spheres of catalytic material. It is noted that the spheres used in the method have the same technical advantages concerning fluidization and mechanical resistance previously stated.
[0053] According to a fifth aspect, the invention relates to a methanation device, characterized in that it comprises:
[0054] - a layer of spheres of catalytic material, obtained by activation of spheres of catalyst precursor material which are the subject of the invention and
[0055] - a means for passing a gas comprising hydrogen (H2) and at least carbon monoxide (CO) and / or carbon dioxide (CO2) into contact with the spheres of catalytic material.
[0056] The aims, advantages and particular characteristics of the device which is the subject of the invention being similar to those of the method which is the subject of the invention, they are not repeated here.
[0057] Brief description of the figures
[0058] Other advantages, aims and particular characteristics of the invention will emerge from the following non-limiting description of at least one particular embodiment of the devices and methods which are the subject of the invention, with reference to the appended drawings, in which:
[0059] Figure 1 represents, in the form of a flowchart, a first succession of particular steps of the preparation process which is the subject of the invention, Figure 2 represents, in the form of a flowchart, a second succession of particular steps of the preparation process which is the subject of the invention,
[0060] Figure 3 represents, in the form of a flowchart, a third succession of particular steps of the preparation process which is the subject of the invention,
[0061] Figure 4 represents, in the form of a flowchart, a fourth succession of particular steps of the preparation process which is the subject of the invention,
[0062] Figure 5 schematically represents a first particular embodiment of the preparation device which is the subject of the invention,
[0063] Figure 6 represents, in the form of a flowchart, a particular succession of steps of the methanation process which is the subject of the invention,
[0064] Figure 7 schematically represents a first particular embodiment of the methanation device which is the subject of the invention,
[0065] Figure 8 represents, graphically, a fluidization study during the implementation of the spheres in a methanation reaction, corresponding to the conversion rate as a function of the gas flow rate, Figure 9 represents, graphically, a first attrition study during the implementation of the spheres in attrition conditions, corresponding to the attrition speed as a function of time and
[0066] Figure 10 graphically represents a second attrition study during the implementation of the spheres under attrition conditions, corresponding to the cumulative mass as a function of time.
[0067] Description of the embodiments
[0068] This description is given without limitation, each characteristic of an embodiment being able to be combined with any other characteristic of any other embodiment in an advantageous manner.
[0069] The following definitions are recalled here:
[0070] The term "support" refers to a material alone, free of pre-catalyst or catalyst. For example, such a support includes alumina (AI2O3).
[0071] The term "catalyst precursor material", also called pre-catalyst, refers to an assembly formed by a support and a catalytic species in deactivated form, such as nickel oxide (of formula NiO), incorporated into the support.
[0072] The terms "catalytic material" or "catalyst" refer to a set formed by the catalytic support and the metallic phase incorporated into this support. In particular, the metallic phase is in activated form, also called "active phase" and corresponds to metallic nickel (of formula Ni(0)) obtained after reduction of nickel oxide (NiO). Only metallic nickel is active in the catalysis of a methanation reaction.
[0073] The terms "methanation reaction" or "methanation", also known as the Sabatier reaction, refer to the hydrogenation of carbon monoxide (formula CO) and / or carbon dioxide (formula CO2) to produce a gas containing methane (CH4). Depending on the gaseous species, CO or CO2, involved in the methanation reaction, the hydrogenation reaction equations R1 or R2 are according to the following chemical equations: 206 kj / mol (RI - CO methanation)
[0074] CO2+ 4H2t; CH4+ 2H2O AG298K = -165 kj / mol (R2 - CO2 methanation) For example, such a methanation reaction is carried out from a synthesis gas, also called "syngas", preferably purified upstream of the methanation unit. It should be noted that a synthesis gas is generally rich in CO, H2, CO2 and CP. A methanation reaction carried out from such a synthesis gas makes it possible to increase the methane content in the gas. It should be noted that a methanation carried out in the presence of a catalyst is also called "catalytic methanation".
[0075] The term "sphericity factor" refers to the ratio between the surface area of the sphere having the same volume as a given particle and the surface area of said particle.
[0076] The term "incorporation" is similar to the term functionalization, corresponding to the fixation of a species or a chemical function on a support.
[0077] The term "monomodal granulometry" corresponds to a statistical term characterizing the distribution of sphere sizes.
[0078] The terms "median diameter", also called d50, correspond to statistical terms characterizing the size of the spheres. For example, a median diameter d50 equal to 150 pm means that 50% of the particles in the distribution are smaller than 150 pm and 50% of the particles in the distribution are larger than 150 pm. Similarly, the terms d90 and d10 correspond to statistical terms characterizing the size of the spheres. For example, a diameter d10 equal to 150 pm means that 10% of the particles in the distribution are smaller than 150 pm and 90% of the particles in the distribution are larger than 150 pm. For example, a diameter d90 equal to 150 pm means that 90% of the particles in the distribution are smaller than 150 pm and 10% of the particles in the distribution are larger than 150 pm.
[0079] The term "water gas shift reaction" refers to a reaction of hydrogen production by reaction between carbon monoxide (CO) and water (formula H2O), also called "Water Gas Shift" or "WGS" reaction and with the following chemical equation R3: Water Gas Reaction (WGS)
[0080] The term "reverse gas-water reaction" refers to the reverse reaction of the gas-water reaction described above. The term "specific surface area" is similar to an active surface area of the catalytic material corresponding to a surface area of a solid catalyst in contact with gaseous reactants, such as CO2, CO and FL.
[0081] The term "fluidized bed" refers to a mixture in which a set of particles and gases form a fluidized bed. Such particles are, for example:
[0082] - support spheres,
[0083] - calcined or uncalcined catalyst precursor material spheres, or
[0084] - spheres of catalytic material.
[0085] Such a fluidized bed is, for example, implemented in a fluidized bed reactor (FBR).
[0086] The term "fines" refers to catalytic particles formed by the attrition of the catalytic material during the fluidized bed methanation process. In particular, the formation of fines results in a progressive change in the fluidization conditions of the catalytic bed. For example, a loss of catalyst surface area and a change in the particle size of the catalytic bed are obtained. All contents are, in the description, expressed as a mass percentage for solids and the contents of gases are expressed as a volume percentage on dry gas.
[0087] Throughout the description, "upper" is used to refer to everything that is at the top in the figures, which correspond to the normal configurations of use of the devices, "lower" is used to refer to everything that is at the bottom in the figures, the terms "vertical" or "height" are derived from these definitions.
[0088] Please note that the figures are not to scale.
[0089] Process for preparing a precursor material for a catalyst for a methanation reaction
[0090] Figure 1 shows, in the form of a flowchart, an embodiment of the method 100 which is the subject of the invention. The method 100 for preparing a generally spherical material which is a precursor to a catalyst for a methanation reaction comprises:
[0091] - a step 101 of forming a generally spherical support comprising mesoporous alumina (of formula AI2O3) or an alumina precursor,
[0092] - a step 102 of incorporating a nickel precursor into the support comprising mesoporous alumina (of formula AI2O3) or an alumina precursor, by bringing a composition comprising the nickel precursor into contact with the support and
[0093] - a calcination step 103 of the catalytic support incorporating the nickel precursor, to at least partially transform the nickel precursor into nickel oxide (of formula NiO) and the alumina precursor into alumina, leading to the formation of a solid of generally spherical shape, such a solid being nicknamed “sphere of catalyst precursor material of a methanation reaction”.
[0094] During the forming step 101, the support comprising mesoporous alumina (AI2O3) or the alumina precursor is shaped. This shaping consists of obtaining a generally spherical support having a sphericity factor greater than 0.75, preferably greater than 0.80 and more preferably greater than 0.85.
[0095] In embodiments, the alumina precursor is a boehmite-type alumina hydrate (of formula AIOOH).
[0096] In embodiments, the step 101 of forming a generally spherical support is performed by granulation.
[0097] In other embodiments, the step 101 of forming a generally spherical support is carried out by atomization. The atomization is applied, for example, to a suspension of boehmite (AIOOH) or alumina (AI2O3) in water. During the atomization, the suspension is sprayed into fine droplets by means of an atomization turbine, or by high-pressure injection through nozzles, in a vertical cylindrical enclosure swept by a flow of hot air. The evaporation of the water leads to the formation of a dry powder recovered in the lower part of the equipment. It is noted that the atomization parameters as well as the characteristics of the equipment used condition the particle size.
[0098] In embodiments (not shown), the step of forming the generally spherical support carried out by atomization further comprises an intermediate heat treatment step. It is noted that such an intermediate heat treatment step is carried out to consolidate the support and thus give it good mechanical strength. For example, such an intermediate heat treatment allows decomposition of any binders, loss of water of constitution and potentially a change of crystalline phase. Thus, better cohesion between the grains of material is obtained.
[0099] In other embodiments, the step 101 of forming a spherical support is carried out by drop coagulation, also called "drip-in-oil." Preferably, the drop coagulation is carried out in two successive steps, the first step consisting of shaping drops and the second step consisting of gelling the drops. For example, the drops of a suspension of boehmite (AIOOH) or alumina (AI2O3) in water are introduced into a column containing an upper phase consisting of oil and a lower aqueous phase consisting of an ammonia solution. The shaping takes place in the upper phase and the gelling in the lower phase. Preferably, the ammonia solution has its pH maintained at a value greater than approximately 9. The residence time of the drops in the ammonia is a few minutes and generally less than approximately 15 minutes.
[0100] During the incorporation step 102, the support comprising mesoporous alumina (AI2O3) or an alumina precursor is brought into contact with a composition comprising the nickel precursor. This contacting makes it possible to form a material incorporating a nickel precursor supported on the support. In embodiments, the incorporation step 102 is a step of impregnating the support with a solution comprising the nickel precursor. Preferably, the nickel precursor is a nickel salt, for example nickel(II) nitrate hexahydrate (of formula Ni(NO3)2.6H2O). Such impregnation can be carried out:
[0101] - “dry”, with the acronym “I Wl” (from the English “Incipient Wetness Impregnation”): the volume of solution containing the prepared nickel precursor is then less than or equal to the volume that can be absorbed by the support or
[0102] - in excess solvent or “wet process”: the volume of solution containing the prepared nickel precursor is then greater than the volume that can be absorbed by the support.
[0103] In embodiments, when the incorporation step is an impregnation step, the impregnation step is performed twice in succession.
[0104] In variants, the formation step 101 and the incorporation step 102 are simultaneous. Such a method makes it possible to obtain a spherical catalyst precursor material called “intermediate” in a single step. Thus, the method is simplified and therefore adaptable according to the industrial constraints present in the production unit.
[0105] In embodiments, when the formation 101 and incorporation 102 steps are simultaneous, the granulation, atomization or drop coagulation steps are carried out by incorporating into a suspension of alumina precursor, for example boehmite (AIOOH), or alumina (AI2O3), a solution comprising a nickel salt. Preferably, the nickel precursor is a nickel salt, for example nickel(II) nitrate hexahydrate, of formula Ni(NO3)2.6H2O.
[0106] During the calcination step 103, a heat treatment of the spherical support incorporating the nickel precursor is carried out. The calcination step 103 makes it possible to transform at least partially:
[0107] - the nickel precursor to nickel oxide (NiO) and
[0108] - the alumina precursor, such as boehmite-type alumina hydrate (AIOOH), into alumina (AI2O3). Thus, a sphere of catalyst precursor material for a methanation reaction is obtained at the end of this calcination step. In embodiments, the calcination step 103 is carried out at a temperature of between 300 and 500°C and preferably between 380 and 420°C and more preferably approximately equal to 400°C. In embodiments, the calcination step 103 is carried out in an atmosphere comprising oxygen, for example in air or in oxygen. In embodiments, the calcination time of the calcination step 103 is greater than 2 hours and preferably approximately equal to 4 hours.
[0109] It is noted that, in these embodiments, the steps performed downstream of the formation step 101, such as the incorporation step 102 and the calcination step 103, have a limited influence on the sphericity factor of the catalyst precursor material sphere. In other words, the final sphericity factor is essentially determined by the formation step 101.
[0110] In embodiments, such as that shown in FIG. 2, the method 200 comprises a step of mechanical treatment 202 of the spherical support downstream of the step of forming 101 of the support. During the mechanical treatment step 202, the spherical support obtained downstream of the forming step 101 undergoes mechanical stresses. For example, the support having been mechanically treated has a sphericity factor greater than 0.85. Preferably, the sphericity factor of the support is greater than 0.9.
[0111] It is noted that, during the mechanical treatment step 202 of the support, elimination of any surface defects is carried out. Thus, the quality of the support is improved, upstream, for example, of the incorporation step 102 of the nickel precursor. Furthermore, the sphericity factor of the spherical support is increased in comparison with the sphericity factor of the support obtained downstream of the formation step 101. In other words, the mechanical treatment step 202 is carried out so as to increase the sphericity factor of the spherical support. In particular, the elimination of certain surface defects present on the support limits the generation of fines, the fines being able to be generated during attrition phenomena. Preferably, the incorporation step 102 is positioned downstream of the mechanical treatment step 202.
[0112] In embodiments, the mechanical treatment step 202 is carried out in a fluidized bed by passing a gas into contact with the spherical support. The mechanical treatment step 202 carried out by fluidization of the support alone makes it possible in particular to “define”, that is to say to form fines by attrition, and to improve the surface condition of the support.
[0113] In variants, the mechanical treatment step 202 is carried out using a rotating tank configured to generate shocks between the support particles, thus surface attrition leading to an improvement in the sphericity of the support.
[0114] Preferably, such a mechanical treatment step 202 is carried out upstream of the incorporation of the nickel precursor 102. It is noted that such a mechanical treatment step 202 in a fluidized bed or in a rotating tank is carried out to reduce the losses of active phase of the catalytic material during the methanation reaction. The term “active phase” refers to the metal incorporated in the support. This mechanical treatment step 202 of the support in a fluidized bed makes it possible in particular to anticipate the formation of fines which may take place during the methanation reaction in a fluidized bed.
[0115] In embodiments, during the mechanical treatment step 202 carried out in a fluidized bed, the gas in contact with the spherical support is an inert gas. In other words, the fluidization is carried out under inert gas. For example, the inert gas consists of air or nitrogen (of formula N2). Preferably, the fluidization rate is twice the minimum fluidization speed, more preferably six times the minimum fluidization speed and even more preferably ten times the minimum fluidization speed.
[0116] In embodiments, downstream of the mechanical treatment step 202 in a fluidized bed, the step 102 of incorporation of a nickel precursor is also carried out in the fluidized bed reactor. Preferably, the incorporation step 102 comprises an impregnation step. More preferably, the incorporation step 102 comprises a dry impregnation step.
[0117] In embodiments, downstream of the incorporation step 102 carried out in the fluidized bed reactor, the calcination step 103 is also implemented in such a reactor. Preferably, during such a calcination step 103, the support is swept by hot air in the fluidized bed reactor. It is noted that the calcination temperatures cited above can be applied to this embodiment.
[0118] Preferably, in these embodiments, the gas from the calcination step 103 then undergoes a treatment to limit the quantity of NOx produced, such as a catalytic treatment or an absorption treatment, for example by washing in an absorber-neutralizer (“scrubber” in English).
[0119] In embodiments, such as that shown in Figure 3, in the method 1000, the mechanical treatment step 202 and the calcination step 103 are carried out simultaneously and preferably in a fluidized bed. In other words, in these embodiments, the method comprises the following successive steps:
[0120] - a training step 101,
[0121] - an incorporation step 102, and
[0122] - a joint step 1003 in which a mechanical treatment step 202 is simultaneous with a calcination step 103.
[0123] Preferably, in these embodiments, the gas from joint step 1003 then undergoes treatment to limit the quantity of NOx produced.
[0124] It is noted that, in these embodiments, the mechanical processing step is indirectly downstream of the formation step 101.
[0125] In embodiments, such as that shown in Figure 4, the method 300 comprises, in addition to the steps of formation 101, incorporation 102 and calcination 103, the following three additional steps:
[0126] - a first drying step 301 positioned downstream of the formation step 101 and upstream of the incorporation step 102,
[0127] - a neutralization step 302 positioned downstream of the incorporation step 102 and
[0128] - a second drying step 303 positioned downstream of the neutralization step 302 and upstream of the calcination step 103.
[0129] In embodiments, the first drying step 301 is carried out at a temperature between 60°C and 150°C. Preferably, the drying temperature is approximately equal to 80°C.
[0130] In embodiments, the drying time of the first drying step 301 is greater than 10 hours.
[0131] It is noted that the neutralization step notably reduces the formation of nitrogen oxides, also referred to as “NOx”. In embodiments, the neutralization step 302 is carried out using a neutralizing solution, for example an ammonium carbonate solution, of formula (NH4)2CO3, and having a pH of between 10 and 13. Preferably, the pH of the neutralizing solution is approximately equal to 11.
[0132] In embodiments, during the neutralization step 302, the final pH of the solution comprising the spherical support incorporating the nickel precursor is between 6 and 8.
[0133] In embodiments, the second drying step 303 is carried out at a temperature between 100°C and 150°C and preferably approximately equal to 125°C.
[0134] Device for preparing a catalyst precursor material for a methanation reaction, preferably in a fluidized bed
[0135] Figure 5 shows a schematic view of an embodiment of the device 400 which is the subject of the invention. The device 400 for preparing spherical precursor material for a catalyst for a methanation reaction comprises:
[0136] - a means 401 for forming a spherical support comprising mesoporous alumina (AI2O3) or an alumina precursor, and having a sphericity factor greater than 0.75, preferably greater than 0.80 and more preferably greater than 0.85,
[0137] - a means 402 for incorporating a nickel precursor into the support comprising mesoporous alumina (AI2O3) or an alumina precursor, by bringing a composition comprising the nickel precursor (Ni) into contact with the support and
[0138] - a means 403 for calcining the support incorporating the nickel precursor, configured to at least partially transform the nickel precursor into nickel oxide (NiO) and the alumina precursor into alumina, and configured to form a solid of generally spherical shape, said solid being nicknamed “sphere of precursor material of a catalyst for a methanation reaction”.
[0139] In embodiments (not shown), the device further comprises a means for mechanically treating the spherical support configured to increase the sphericity factor of the support. In embodiments, the mechanical treatment means comprises a fluidized bed during the mechanical treatment of the support. For example, the mechanical treatment means is a fluidized bed reactor. In embodiments, when a fluidized bed is implemented, the fluidization rate is twice the minimum fluidization speed. Preferably, the fluidization rate is six times the minimum fluidization speed and even more preferably ten times the minimum fluidization speed. It is noted that the means for mechanically treating the support obtained by the forming means 401 is configured to increase the sphericity factor of the support.Preferably, such an increase is carried out upstream of the implementation of the means of incorporation 402 of the nickel precursor.
[0140] In embodiments, the mechanical treatment means and the calcination means 403 are combined. For example, the mechanical treatment means comprises a fluidized bed having conditions allowing the calcination of the spherical support. For example, such conditions correspond to a calcination temperature. In embodiments, the mechanical treatment means comprises, for example, a rotating tank configured to generate shocks between the support particles and therefore surface attrition leading to an improvement in the sphericity of the support.
[0141] Preferably, the means of the device 400 and the associated variants are configured to implement the steps of the methods, 100, 200, 300 and / or 1000, and their embodiments as set out above and the methods 100, 200, 300 and / or 1000, as well as their different embodiments can be implemented by the means of the device 400.
[0142] Spheres of catalyst precursor material for a methanation reaction, preferably in a fluidized bed
[0143] The spheres of catalyst precursor material for a methanation reaction which are the subject of the invention are obtained from an embodiment of the process which is the subject of the invention described above. The spheres of catalyst precursor material for a methanation reaction, preferably in a fluidized bed, comprise nickel oxide (NiO) and mesoporous alumina (AI2O3), the respective proportions of which are preferably, relative to the total mass of these two compounds:
[0144] - NiO: 1 to 50% by mass, preferably 10 to 50% by mass and even more preferably 10 to 25% by mass and
[0145] - AI2O3: 50 to 99% by mass, preferably 50 to 90% by mass and even more preferably 75 to 90% by mass.
[0146] In embodiments, the alumina (AI2O3) is mesoporous and has a gamma or delta structure. In embodiments, the mesoporous alumina (AI2O3) has a mesoporosity corresponding to a median pore diameter, determined by Hg intrusion porosimetry, of between 3 and 50 nm and preferably of between 5 and 25 nm.
[0147] In embodiments, the spheres of catalyst precursor material of a methanation reaction further comprise a compound configured to trap poisons from the catalyst. Preferably, such a compound is a sacrificial catalyst or a specific poison trap. Such a compound is, for example, selected from zinc, molybdenum and tungsten oxides.
[0148] Thus, the resistance of the catalytic material spheres against organic or inorganic poisons, such as light tars (Benzene Toluene Xylenes or BTX) or sulfur compounds (e.g. H2S or COS), is increased.
[0149] In embodiments, the catalyst precursor material spheres have a pore volume, as measured by Hg intrusion porosimetry, of between 0.20 and 0.60 cm 3 / g and preferably between 0.25 and 0.40 cm 3 / g.
[0150] In embodiments, the catalyst precursor material spheres have a specific surface area of between 50 and 300 m 2 / g and preferably between 100 and 250 m 2 / g.
[0151] In embodiments, the catalyst precursor material spheres have a monomodal particle size with a median diameter of between 100 and 1000 μm (micrometer). Preferably, the median diameter of the catalyst precursor material spheres is between 200 and 800 μm. Even more preferably, the median diameter of the catalyst precursor material spheres is between 250 and 350 μm.
[0152] In embodiments, when using the catalytic material spheres in a fluidized bed methanation reaction, the particle size range is chosen, for example, as a function of a hydrodynamic state and an arrangement of the heat transfer surfaces. The hydrodynamic state is, for example, defined by a fluidization rate. In particular, during a significant increase in the quantity of synthesis gas involved in the methanation reaction, the particle size of the catalyst is adapted during the design, making it possible to avoid the use of a reactor having too large a diameter. It is noted, in this example, that such an adaptation is accompanied in particular by an adaptation also of the height of the catalytic layer initially used. This adaptation is necessary because of the exothermicity of a methanation reaction generating a release of significant thermal power.
[0153] In embodiments, the catalyst precursor material spheres have a particle size distribution of amplitude, calculated according to the ratio (d90 - d10) / d50, less than 100%, preferably less than 70%, more preferably less than 50% and even more preferably less than 20%.
[0154] In embodiments, the catalyst precursor material spheres have a particle size distribution of magnitude, calculated according to the ratio (d90 - d10) / d50, of between 40% and 70%. In variants, the particle size distribution of magnitude, calculated according to the ratio (d90 - d10) / d50, is between 60% and 70%.
[0155] In variants, the catalyst precursor material spheres have a polymodal particle size distribution. The term "polymodal particle size distribution" refers to a polymodal distribution, a term used in statistics, characterizing the particle size distribution.
[0156] Methanation process
[0157] Figure 6 shows, in the form of a flowchart, an embodiment of the method 500 which is the subject of the invention. The methanation method 500 comprises:
[0158] - a step 501 of activating, at least partially, the spheres of catalyst precursor material into spheres of catalytic material having the same characteristics as the spheres of catalyst precursor material described previously and
[0159] - a step 502 of passing a gas comprising hydrogen (H2) and at least carbon monoxide (CO) and / or carbon dioxide (CO2) into contact with the spheres of catalytic material.
[0160] It is noted that the catalyst precursor material spheres are obtained from the process for preparing catalyst precursor material which is the subject of the invention and described above. The characteristics of the catalyst precursor material spheres which are the subject of the invention are identical to the characteristics of the spheres used in the methanation process.
[0161] During the activation step 501, the catalyst precursor material spheres are activated at least partially into catalytic material spheres, following a suitable temperature profile, in contact with a reducing agent. Preferably, the reducing agent is a reducing gas, such as, for example:
[0162] - carbon monoxide (formula CO),
[0163] - hydrogen (formula H2) or
[0164] - ammonia (formula NH3) or a mixture of at least two of these gases.
[0165] In embodiments, the reducing gas is pure or diluted with an inert gas such as, for example, argon (of formula Ar), nitrogen (of formula N2) or helium (of formula He).
[0166] This activation step transforms all or part of the nickel oxide (formula NiO) into metallic nickel (formula Ni(0)) and provides all or part of the activation energy by hydrogenation of CO2, which is exothermic. Ni(0) is the active catalytic species during the catalysis of the methanation reaction.
[0167] In embodiments, the reducing gas is pure or diluted with carbon dioxide (of formula CO2) in addition to an inert gas such as, for example, argon (of formula Ar), nitrogen (of formula N2) or helium (of formula He). In embodiments, the temperature profile suitable for carrying out the activation step 501 comprises a temperature rise from the ambient to 400°C with a ramp of 2°C / min, and a 4-hour hold at 400°C in the presence of a reducing gas. Preferably, the activation step 501 is carried out at a temperature between 300 and 500°C, even more preferably between 380 and 420°C. Preferably, the reducing gas comprises hydrogen (H2), even more preferably combined with carbon dioxide (CO2). Preferably, the activation step 501 is carried out during a 4-hour period.
[0168] During the passage step 502, a gas comprising hydrogen (H2) and at least carbon monoxide (CO) and / or carbon dioxide (CO2) is brought into contact with the spheres of catalytic material. During the passage step 502, depending on the gaseous species CO or CO2 present in the gas, the reactions R1 or R2 defined previously take place. The passage of the gas thus allows the production of methane (CPU) by hydrogenation of CO and / or CO2 in the presence of H2.
[0169] In variants, the activation step 501 is finalized under a flow of syngas, followed by the step 502 of passing a gas comprising hydrogen (H2) and carbon monoxide (CO).
[0170] In variants, the activation step 501 is finalized by a gas comprising hydrogen (H2) and carbon dioxide (CO2) followed by the passage step 502.
[0171] In embodiments (not shown), the method 500 further comprises, upstream of the gas passage step, a gas constitution step comprising at least one of the following steps:
[0172] - pyrolysis of hydrocarbon materials (biomass, waste, coal),
[0173] - pyro-gasification of hydrocarbon materials (biomass, waste, coal),
[0174] - gasification of hydrocarbon materials (biomass, waste, coal),
[0175] - co-electrolysis of CO2 / H2O as described in patent application EP 16757688.3, incorporated herein by reference,
[0176] - reaction of gas with water,
[0177] - reverse reaction of gas to water described previously,
[0178] - electrolysis of water,
[0179] - a stage of production of a hydrogen-rich gas,
[0180] - a stage of production of a gas rich in CO2 and
[0181] - a steam introduction step.
[0182] For example, the hydrogen produced during the hydrogen-rich gas production step corresponds to an effluent to be treated. In particular, such an effluent comes from an ancillary process in which hydrogen constitutes a secondary product to be treated. Thus, the methanation process, coupled with the ancillary process producing a hydrogen-rich gas, allows the treatment and therefore the recovery of such a gas. In other words, the hydrogen from the ancillary process is a so-called "fatal" source for the methanation process. This example can also be transposed to CO2 corresponding to an effluent stream to be treated and produced during the CO2-rich gas production step implemented in an ancillary process.
[0183] It is noted that a “hydrogen-rich gas” is a gas having a molar percentage of hydrogen, relative to the total quantity of matter of the gas, greater than 50%. It is noted that a “CO2-rich gas” is a gas having a molar percentage of CO2, relative to the total quantity of matter of the gas, greater than 50%. In embodiments, during the step 502 of passing the gas into contact with the spheres of catalytic material, the gas passes through a layer of spheres of catalytic material. In other embodiments, during the step 502 of passing the gas into contact with the spheres of catalytic material, the gas passes through a fluidized bed of spheres of catalytic material.
[0184] It is recalled that a fluidized bed makes it possible to give a category of solids, here the spheres of catalytic material, certain properties of liquid fluids. In other words, in the case of the invention, a fluidized bed corresponds to the assembly formed by the spheres of catalytic material and the gas comprising H2 and at least CO and / or CO2. A fluidized bed allows a strong interaction between the spheres of catalytic material and the gas passing through it. The principle of the fluidized bed is to inject a pressurized gas under a layer of solid spheres of catalytic material. This gas lifts and disperses the spheres of solid catalytic material. The fluidized bed allows more efficient catalysis.
[0185] Particle agitation and hydrodynamic mixing by trains of gas bubbles create fluidized beds, volumes in which the solid spheres of catalytic material are vigorously agitated. Within the fluidized bed, the spheres of catalytic material exchange heat and matter with high efficiency, by direct contact, with a large specific surface area, with the gas or with a submerged exchanger for the recovery or elimination of the heat produced by the reaction of conversion of CO and / or CO2 into CH4. The fluidized bed then constitutes an open volume, practically isothermal, due to the high specific heat capacity of the solids compared to that of the gas, as well as by their renewal in contact with the exchange surfaces.
[0186] In embodiments (not shown), the method 500 further comprises a step of cooling the fluidized bed by at least one heat exchange tube immersed in the fluidized bed. Preferably, the step 502 of passing the gas into contact with the spheres of catalytic material and the step of cooling the layer of the fluidized bed are simultaneous.
[0187] Methanation device
[0188] Figure 7 shows a schematic view of an embodiment of the device 600 which is the subject of the invention. The methanation device 600 comprises:
[0189] - a layer of spheres of catalytic material 606, obtained by activation of spheres of catalyst precursor material, and
[0190] - a means 604 for passing a gas comprising hydrogen (H2) and at least carbon monoxide (CO) and / or carbon dioxide (CO2) over the layer of spheres of catalytic material.
[0191] It is noted that the spheres of catalyst precursor material are obtained from the method for preparing catalyst precursor material which is the subject of the invention. Preferably, such spheres are obtained from the method described above. The characteristics of the spheres of catalyst precursor material which is the subject of the invention are identical to the characteristics of the spheres used in the device 600.
[0192] Preferably, the means of the device 600 are configured to implement the steps of the method 500 and their embodiments as set out above and the method 500 as well as its different embodiments can be implemented by the means of the device 600.
[0193] It is noted, in Figure 7, that the device 600 is configured to convert a gas comprising H2 and at least CO and / or CO2 into CPU, when this gas passes over the spheres of catalytic material. In embodiments, as shown in Figure 7, the reactor 600 comprises an enclosure 601 having a lower longitudinal end 602, and a high longitudinal end 603 opposite the lower longitudinal end 602. The enclosure 601 is, for example, formed of a closed and sealed volume. The shape, internal and / or external, of the enclosure 601 is of no importance for the invention as long as the enclosure is made sealed. For example, the enclosure 601 has a tubular shape, that is to say a cylindrical shape, which may be oblong as shown in Figure 7.
[0194] It can be seen in Figure 7 that the enclosure 601 comprises, near the lower end 602, an inlet 604 for gas comprising H2 and at least CO and / or CO2. The enclosure 601 comprises, near the upper end 603, an outlet 605 for CPU or for a gas rich in CH4. For example, the inlet 604 is an injection nozzle, a nozzle, a perforated tube, a perforated plate, a porous plate (sintered metal or porous ceramic), a network of porous sleeves, a network of piping equipped with strainers. However, any fluid injection member usually used in a reactor can be used to produce the inlet 604. For example, the outlet 605 is an opening formed in the enclosure 601 connected to a methane transport pipe.
[0195] In embodiments, as shown in Figure 7, the circulating gas from the inlet 604 passes through a layer of catalytic material spheres present in the reactor 600. Preferably, the reactor 600 is a fluidized bed reactor containing the catalytic material spheres.
[0196] In embodiments, the reactor 600 comprises heat exchange tubes (not shown) immersed in the fluidized bed of the enclosure 601 and having a temperature compatible with the nominal operating temperature inside the enclosure 601 during operation of the reactor 600. The heat exchange tubes contain a circulating fluid having a lower temperature than the interior of the enclosure 601. The heat exchange tubes thus allow the temperature of the reactor 600 to be maintained by evacuating excess heat linked to the exothermicity of the reactions carried out. Preferably, this evacuated excess heat is used.
[0197] The exothermicity of the methanation reactions, indicated in formula 1, results in an increase in the temperature of the reaction medium. In embodiments, the average temperature of the reaction medium 606 is controlled and between 260°C and 350°C. This control of the average temperature of the reaction medium 606 promotes the activation and thermodynamics of the methanation reaction. Thus, the yield of the reaction is increased.
[0198] In embodiments, the pressure inside the enclosure 601 is between one bar (atmospheric pressure) and 70 bar. Preferably, the pressure is between 1 bar and 20 bar, more preferably between 1 bar and 14 bar, and even more preferably between 2 and 5 bar. These pressures optimize the conversion to methane and minimize upstream compression costs.
[0199] In embodiments, the fluidization / flow rate range is between one time the minimum fluidization speed and sixteen times the minimum fluidization speed, preferably between two times and eight times the minimum fluidization speed. The heat exchange is thus optimized. In particular, such a range corresponds to a preferred domain for:
[0200] - promote heat exchange and
[0201] - reduce mechanical stresses on the catalyst, such as attrition, and therefore reduce catalyst elutriation. Examples of preparation of spherical catalyst precursor material
[0202] Examples of preparation of the spherical catalyst are mentioned in the following description, without limitation.
[0203] In a first example, a step of forming a spherical support 101, also called “shaping the support”, comprises an atomization step. Such an atomization step is implemented in an atomizer equipped with a bi-fluid nozzle and corresponds to the atomization of a dispersion composed of:
[0204] - 50% by mass of a boehmite-type alumina hydrate,
[0205] - 50% by mass of a 2% acetic acid solution supplemented with 5% by mass of a temporary binder such as polyvinyl alcohol.
[0206] In this example, the atomizer inlet temperature is approximately 400°C and the outlet temperature is maintained at approximately 140°C. An atomized powder with a residual humidity of approximately 10.2% is thus obtained.
[0207] In this example, the step of forming the spherical support 101 may comprise, downstream of the atomization step, an intermediate heat treatment step corresponding in particular to calcination of the support at approximately 500°C for 4 hours. It is noted that such an intermediate heat treatment step is preferably carried out in order to give the support good mechanical strength.
[0208] Alternatively, in this example, a drying step 301 at 80°C for 12 hours in an oven can be carried out downstream of the step of forming the spherical support 101 without intermediate calcination and in particular downstream of the atomization step.
[0209] Then, in this example, a step 102 of incorporation of a nickel precursor comprising an excess solvent impregnation step is implemented. This impregnation step is carried out by immersing the spherical alumina support in an aqueous solution of nickel(ll) nitrate hexahydrate, of formula Ni(NO3)2.6H2O, with a mass concentration of nickel equal to 17.5% at 60°C for 1 h.
[0210] Then, a neutralization step 302 is carried out, by gradually adding to the solution containing the impregnated spherical support, a solution of ammonium carbonate, of formula (NH^COa, of pH equal to 11 and at 60°C. It is noted that the atomic ratio (NH^COs / Ni is equal to 1.75 and the volume of solution added covers the support. The pH of the final solution is approximately equal to 6.5. The final solution is removed and the support is washed with water while stirring. Preferably, the impregnation step is carried out again.
[0211] Then, in this example, the impregnated and neutralized spherical support is dried at 125°C in air for 12 hours during a second drying step 303.
[0212] Finally, in this first example, a calcination step 103 is carried out by introducing the dried spherical support into a calcination furnace at a temperature of 400°C in air and with a temperature rise ramp of between 1°C / min and 10°C / min, for 4 hours.
[0213] In a second example, downstream of the atomization step mentioned previously in the first example, a mechanical treatment step 202 is preferably carried out in a fluidized bed. In particular, the support obtained after the formation step 101 is loaded into a fluidized bed reactor. Then, in the reactor, fluidization is obtained by passing an inert gas, such as air and / or nitrogen, into contact with the spherical support. For example, the mechanical treatment step 202 preferably carried out in a fluidized bed is applied by implementing the following fluidization conditions for 3 hours: - gas: air,
[0214] - temperature: 320°C,
[0215] - pressure: atmospheric,
[0216] - fluidization gas velocity 10 times higher than the minimum fluidization velocity.
[0217] Such a mechanical treatment step 202 is implemented in order to improve the quality of the support and in particular to increase the sphericity factor.
[0218] Then, in this second example, a step 102 of incorporation of a nickel precursor comprising a dry impregnation step is carried out in the reactor.
[0219] Finally, in this second example, a calcination step 103 is implemented in the reactor by passing a flow of hot air in contact with the impregnated spheres.
[0220] In a third example, downstream of:
[0221] - the atomization step mentioned previously in the first example and
[0222] - an impregnation step, preferably dry or wet, a mechanical treatment step 202 simultaneous with a calcination step 103 is preferably carried out in a fluidized bed.
[0223] In particular, the support obtained after the impregnation step is loaded into a reactor, preferably in a fluidized bed. Then, in the reactor, fluidization is obtained by passing an inert gas, such as air and / or nitrogen and / or combustion fumes, into contact with the spherical support. For example, the mechanical treatment step 202 simultaneous with a calcination step 103 preferably carried out in a fluidized bed is applied by implementing the following fluidization conditions for 4 hours:
[0224] - gas: fumes,
[0225] - temperature: 500°C,
[0226] - pressure: atmospheric,
[0227] - fluidization gas velocity 10 times higher than the minimum fluidization velocity.
[0228] Such a mechanical treatment step 202 simultaneous with a calcination step 103 is implemented in order to improve the quality of the support and in particular to increase the sphericity factor while incorporating the nickel precursor. Thus, a sphere of precursor material for a catalyst of a methanation reaction is obtained at the end of this simultaneous mechanical treatment and calcination step.
[0229] Examples of implementation of catalyst precursor material spheres and catalytic material spheres during a fluidized bed methanation reaction.
[0230] Good fluidization quality.
[0231] The catalytic material spheres, obtained after activation of the catalyst precursor material spheres which are the subject of the invention, were used during the implementation of a fluidized bed methanation process. It is noted that Figure 8 presents results obtained during the implementation of a methanation process.
[0232] In the examples of Figure 8, the spheres of catalyst precursor material before the activation step have the following composition: 23.3% NiO, 76.7% AI2O3 and a sphericity factor equal to 0.79. It is noted, in these examples, that the spheres of catalytic material are, beforehand, obtained by reducing treatment of the spheres of precursor material of the catalyst which is the subject of the invention. This treatment is carried out under a gas flow comprising hydrogen diluted in a nitrogen flow according to an isovolumic proportion, at a temperature of 400°C for a duration of less than 10 hours. The molar proportion between hydrogen (H2) and nickel is equal to 10. The gas velocity is 6 times greater than the minimum fluidization velocity.
[0233] It is noted, in these examples, that the methanation reaction corresponds to the conversion of CO2 into CH4 in the presence of H2 and is carried out under the following conditions:
[0234] - temperature equal to 325°C,
[0235] - pressure equal to 2 bara and
[0236] - composition of the gas before methanation, in molar percentage relative to the quantity of total matter in the gas: 30% CO2 and 70% H2.
[0237] It is noted that, for each of the examples shown in Figure 8, different gas flow rates are applied to the conditions mentioned above. In particular, these different flow rates correspond to different fluidization regimes. A methanation system is thus obtained for each example.
[0238] Graph 700, shown in Figure 8, shows the gas flow rate of the fluidized bed in Nm on the abscissa 3 / h and on the ordinate the conversion rate in percentage. Note that several conversion rates are represented as a function of the gas flow rate:
[0239] - the hydrogen conversion rate (H2) represented in black circle,
[0240] - the maximum rate of H2 conversion at equilibrium represented in white triangle,
[0241] - the carbon dioxide (CO2) conversion rate shown in white circle.
[0242] Note in Figure 8 that the H2 conversion rate and the maximum H2 conversion rate at equilibrium are superimposed. Note that the conversion rates shown in Figure 8 are defined by the following ratios:
[0243] The conversion of CO2 is calculated, for example, according to the following equation: in which:
[0244] - Qco2, inlet is the molar flow rate of CO2 entering the methanation reactor and
[0245] - Qco2, output is the molar flow rate of CO2 at the outlet of the methanation reactor.
[0246] The conversion of H2 is calculated, for example, according to the following equation: in which:
[0247] - QH2, inlet is the molar flow rate of hydrogen entering the methanation reactor and
[0248] - QH2, output is the molar flow rate of hydrogen leaving the methanation reactor.
[0249] The deviation from equilibrium is calculated, for example, according to the following equation: in which:
[0250] - QH2, input is the volume flow rate of hydrogen entering the methanation reactor,
[0251] - Q SNG ex P érimental is the experimental volume flow rate of the methanation product called SNG (from the English “Substitute Natural Gas”), composed of CH4 and water, and - QsNG équilibre is the volume flow rate of the methanation product calculated at equilibrium via the Aspen HYSIS software (trade name) and XH2 is the volume fraction of hydrogen.
[0252] Note that the deviation from equilibrium indicates whether the system is close to the conversions obtained at thermodynamic equilibrium. In other words, whether the maximum conversion is reached during the methanation reaction. Thus, the closer the deviation is to 0, the closer the system will be to thermodynamic equilibrium under the operating conditions of the example.
[0253] The maximum hydrogen conversion at equilibrium is calculated, for example, according to the following equation:
[0254] Note that the equilibrium H2 conversion is the maximum hydrogen conversion that the system can achieve. Thus, the closer the experimentally obtained conversion is to the equilibrium conversion, the closer the system is to the maximum conversion that can be achieved under the operating conditions of the example.
[0255] It is noted that, in a similar way, these elements can also be calculated for the methanation of CO. It is noted that good fluidization quality corresponds to good fluidization hydrodynamics and is thus linked to high conversion.
[0256] The examples in Figure 8 highlight the performance of the catalytic material spheres during a CO2 methanation reaction carried out in a fluidized bed reactor. Indeed, it is noted that, for different fluidization regimes, i.e. at different gas flow rates, the hydrogen conversion remains above 96%, which also corresponds to the maintenance of good fluidization quality.
[0257] Thus, the systems of the different examples associated with Figure 8 achieve maximum conversion for all fluidization regimes implemented in these examples. Such maximum conversion is highlighted by the very small difference between:
[0258] - the conversion of hydrogen obtained experimentally (Conversion H2), previously described in formula 2 and
[0259] - the conversion calculated at equilibrium (Conversion H2 (equilibrium)), described previously in formula 4.
[0260] It is noted here that given a H2 / CO2 ratio (70 / 30) lower than the stoichiometric ratio, a condition imposed voluntarily, the CO2 conversion is not total. However, the CO2 conversion remains stable around 50% under the tested conditions of the examples. This experimental conversion of CO2 corresponds to the maximum conversion that can be achieved under such test conditions. Thus, for all the examples associated with Figure 8, it is noted that the use of spheres of catalytic material shows great flexibility in the conditions of use of the catalyst.
[0261] Limiting attrition
[0262] The mechanical strength of the catalyst precursor material spheres was compared to the mechanical strength of commercial catalyst precursor material particles when implementing a fluidized bed process promoting attrition phenomena. In the remainder of the description, it is noted that: - The term "spheres" designates the catalyst precursor material spheres which are the subject of the invention and
[0263] - The term “commercial particles” means commercial catalyst precursor material particles.
[0264] Note that Figures 9 and 10 present results obtained during the implementation of a methanation process for two comparative examples, one corresponding to spheres and the other to commercial particles. An attrition system is thus obtained for each example. In the comparative examples of Figures 9 and 10:
[0265] - the catalyst precursor material spheres, upstream of the implementation of the attrition conditions, have the following composition: 23.3% NiO, 76.7% AI2O3 and a sphericity factor equal to 0.79;
[0266] - commercial particles, upstream of the implementation of attrition conditions, present:
[0267] - a nickel content equal to 47% by mass and
[0268] - a sphericity factor corresponding to 0.73.
[0269] It is noted that the conditions for implementing the method for the comparative examples shown in Figures 9 and 10 are configured to generate significant mechanical stresses on both materials, spheres and particles. In particular, the attrition test examples are carried out as a function of parameters such as the fluidization temperature, the velocity of an inert fluidization gas and the water vapor content. These parameters are configured to generate mechanical stresses.
[0270] For the attrition test examples, the commercial spheres or particles are loaded into a fluidized bed reactor, which is then supplied with inert gas corresponding to air for fluidization of the commercial spheres or particles. Note that, in the examples of Figures 9 and 10, the commercial spheres and particles are subjected to the following fluidization conditions:
[0271] - temperature: 320°C for commercial particles and for spheres,
[0272] - pressure: atmospheric,
[0273] - fluidization gas velocity 10 times higher than the minimum fluidization velocity,
[0274] - duration of tests: 48 hours.
[0275] In the comparative examples shown in Figures 9 and 10, the production of fines is evaluated from the weighing of the particles recovered via a cyclone coupled to the outlet of the fluidized bed reactor.
[0276] Graph 800, shown in Figure 9, shows on the abscissa the time in hours (h) and on the ordinate the attrition rate in range per gram of bed and per hour (g / g / h) for two materials tested.
[0277] The following formula 5 is used for the calculation of the attrition rate shown in Figure 9. The attrition rate is defined by the loss of mass per unit time, for example, according to the following equation:
[0278] — 1 dmi oss jr = - - -
[0279] Tfijj dt in which:
[0280] - mb is the mass of the bed and
[0281] - m / oss.t is the attrited mass for a duration t. In these examples, the mass of the fines is determined by weighing, after stopping the attrition process, the fines formed during the implementation of such a process. The initial mass corresponds to the mass of catalyst precursor material loaded into the fluidization reactor.
[0282] Graph 900, shown in Figure 10, shows the time in hours (h) on the abscissa and the cumulative mass of fines as a percentage on the ordinate for two materials tested. The line shown on graph 900 corresponds to the delimitation of an initial heating-defining step carried out before the study of the system and by implementing the fluidization conditions mentioned above for 3 hours. It should be noted that the heating-defining step reproduces conditions implemented, for example, during a mechanical treatment step carried out in a fluidized bed.
[0283] We note, in figures 9 and 10, that each comparative example corresponds:
[0284] - to the spheres, associated with the black circles or
[0285] - to commercial particles, associated with white squares.
[0286] The comparative examples in Figures 9 and 10 highlight the limitation of sphere attrition, and thus of fines production, when implementing attrition conditions. Indeed, it is noted that for a similar duration of the attrition process, the cumulative mass lost for the spheres is lower than the cumulative mass lost for the commercial particles. In addition, the instantaneous attrition rate of the spheres is lower than the instantaneous attrition rate of the commercial particles.
[0287] From this example, it is deduced that the spheres which are the subject of the invention have better mechanical resistance compared to commercial particles.
[0288] Furthermore, as seen in the examples in Figure 9, the attrition rate is higher during the first twenty hours of the attrition process implementation. Indeed, during this period, the angular particles are mechanically treated by the fluidized bed, generating more fines. This effect is less pronounced towards the end of the attrition process implementation.
[0289] Furthermore, this effect of significant formation of fines at the start of the fluidization process was also verified in another example (not shown), for a fluidized bed methanation reactor initially loaded with approximately 100 kg of spheres of catalytic material which are the subject of the invention.
[0290] In this other example, over the first fifty hours of operation, approximately 100 g of fines were captured at a bag filter placed downstream of the methanation reactor, or 0.1% of the initial load. Then, between these first fifty hours and more than 1000 hours of operation, only about ten grams of fines were recovered. During the first hours of operation, the angular parts are slightly eroded until they form a nearly perfect sphere by mechanical treatment, thereby generating a certain quantity of fines. Once this process is complete, the attrition phenomena are almost completely eliminated with a weight loss of approximately 0.01% every 1000 hours of operation.Such a result shows the additional advantage of implementing a mechanical treatment step 202 of the support of the catalyst precursor material in order to improve the sphericity factor upstream of the incorporation step 102 of the nickel precursor, preferably in a fluidized bed.
Claims
CLAIMS 1. Method for preparing (100, 200, 300, 1000) a generally spherical material precursor of a catalyst for a methanation reaction, characterized in that it comprises: - a step of forming (101) a generally spherical support comprising mesoporous alumina (AI2O3) or an alumina precursor and having a sphericity factor greater than 0.75, preferably greater than 0.80 and more preferably greater than 0.85, - a step of incorporating (102) a nickel precursor into the support comprising mesoporous alumina (AI2O3) or an alumina precursor, by bringing a composition comprising the nickel precursor into contact with the support, - a step of calcining (103) the support incorporating the nickel precursor, to at least partially transform the nickel precursor into nickel oxide (NiO) and the alumina precursor into alumina, leading to the formation of a solid of generally spherical shape, said solid being nicknamed “sphere of precursor material of catalyst of a methanation reaction”, and - a step of mechanical treatment (202) of the spherical support, downstream of the step of forming the support, to increase the sphericity factor of the spherical support.
2. Method (200) according to claim 1, in which the mechanical treatment step (202) is carried out in a fluidized bed by passing a gas into contact with the spherical support.
3. Method (1000) according to claim 2, in which the mechanical treatment step (202) and the calcination step (103) are simultaneous and carried out in a fluidized bed.
4. Method (200) according to one of claims 2 or 3, in which during the mechanical treatment step (202) carried out in a fluidized bed, the gas in contact with the spherical support is an inert gas.
5. Method (200) according to one of claims 2 to 4, in which during the mechanical treatment step (202) carried out in a fluidized bed the fluidization rate is at least twice the minimum fluidization speed.
6. Method (200) according to one of claims 2 to 5, in which during the mechanical treatment step (202) carried out in a fluidized bed Preferably, the fluidization rate is at least six times greater than the minimum fluidization speed.
7. Method (200) according to one of claims 2 to 6, in which during the mechanical treatment step (202) carried out in a fluidized bed the fluidization rate is at least ten times greater than the minimum fluidization speed.
8. Method (200) according to one of claims 2 to 7, in which, downstream of the mechanical treatment step (202) in a fluidized bed, the step of incorporation (102) of a nickel precursor is also carried out in the fluidized bed reactor.
9. The method (200) of claim 1, wherein the mechanical processing step (202) is performed using a rotating tank configured to generate impacts between the support particles.
10. Method (200) according to one of claims 1 to 9, in which the generally spherical support comprises an alumina precursor in the form of a boehmite-type alumina hydrate (of formula AIOOH).
11. Method (100, 200, 300) according to one of claims 1 to 10, in which the incorporation step (102) comprises a step of impregnating the catalytic support with a solution comprising the nickel precursor.
12. Method (100, 200, 300) according to one of claims 1 to 11, in which the step of forming (101) the spherical catalytic support comprises a granulation step.
13. Method (100, 200, 300) according to one of claims 1 to 11, in which the step of forming (101) the spherical catalytic support comprises an atomization step.
14. Method (100, 200, 300) according to one of claims 1 to 11, in which the step of forming (101) the spherical catalytic support comprises a drop coagulation step.
15. Device (400) for preparing generally spherical material, precursor of a catalyst for a methanation reaction, characterized in that it comprises: - a means for forming (401) a generally spherical support comprising mesoporous alumina (AI2O3) or an alumina precursor and having a sphericity factor greater than 0.75, preferably greater than 0.80 and more preferably greater than 0.85, - a means of incorporating (402) a nickel precursor into the support comprising mesoporous alumina (AI2O3) or an alumina precursor, by bringing a composition comprising the nickel precursor (Ni) into contact with the support and - a means for calcining (403) the support incorporating the nickel precursor, configured to at least partially transform the nickel precursor into nickel oxide (NiO) and the alumina precursor into alumina, and configured to form a solid of generally spherical shape, said solid being nicknamed "sphere of precursor material of a catalyst of a methanation reaction", which further comprises a means for mechanical treatment of the spherical support, downstream of the formation of the support, to increase the sphericity factor of the spherical support.
16. Spheres of precursor material for a catalyst of a methanation reaction, obtained by the method (100, 200, 300) according to one of claims 1 to 14, characterized in that they comprise nickel oxide (NiO) and mesoporous alumina (AI2O3), the respective proportions of which are, relative to the total mass of these two compounds: - NiO: 1 to 50% by mass and - AI2O3: 50 to 99% by mass.
17. Spheres of catalyst precursor material according to claim 16, which have a monomodal particle size with a median diameter of between 100 and 1000 pm, preferably between 200 and 800 pm and more preferably between 250 and 350 pm.
18. Spheres of catalyst precursor material according to one of claims 16 or 17, in which the alumina (AI2O3) has a gamma or delta structure.
19. Spheres of catalyst precursor material according to one of claims 16 to 18, in which the alumina (AI2O3) has a mesoporosity corresponding to a median pore diameter, determined by Hg intrusion porosimetry, of between 3 and 50 nm and preferably between 5 and 25 nm.
20. Spheres of catalyst precursor material according to one of claims 16 to 19, which have a specific surface area of between 50 and 300 m 2 / g and preferably between 100 and 250 m 2 / g.
21. Methanation process (500), characterized in that it comprises: - a step of activating (501), at least partially, into spheres of catalytic material, spheres of catalyst precursor material according to one of claims 16 to 20 and - a step of passing (502) a gas comprising hydrogen (H2) and at least carbon monoxide (CO) and / or carbon dioxide (CO2) into contact with the spheres of catalytic material.
22. Method according to claim 21, which comprises, upstream of the gas passage step, a gas constitution step comprising at least one of the following steps: - pyrolysis of hydrocarbon materials, - pyro-gasification of hydrocarbon materials - gasification of hydrocarbon materials, - co-electrolysis of CO2 / H2O, - reaction of gas with water, - reverse reaction of gas to water, - a stage of production of a hydrogen-rich gas, - a stage of production of a CO2-rich gas and - a step of introducing steam into the gas.
23. Method according to one of claims 21 or 22, in which, during the step of passing the gas into contact with the spheres of catalytic material, the gas passes through a fluidized bed of spheres of catalytic material.
24. Methanation device (600), characterized in that it comprises: - a layer of spheres of catalytic material (606), obtained by activation of spheres of catalyst precursor material according to one of claims 16 to 20 and - a means (604) for passing a gas comprising hydrogen (H2) and at least carbon monoxide (CO) and / or carbon dioxide (CO2) into contact with the spheres of catalytic material.