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  • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen; Reversible storage of hydrogen
  • C01B3/02—Production of hydrogen; Production of gaseous mixtures containing hydrogen
  • C01B3/32—Production of hydrogen; Production of gaseous mixtures containing hydrogen by reaction of gaseous or liquid organic compounds with gasifying agents, e.g. water, carbon dioxide or air
  • C01B3/34—Production of hydrogen; Production of gaseous mixtures containing hydrogen by reaction of gaseous or liquid organic compounds with gasifying agents, e.g. water, carbon dioxide or air by reaction of hydrocarbons with gasifying agents
  • C01B3/38—Production of hydrogen; Production of gaseous mixtures containing hydrogen by reaction of gaseous or liquid organic compounds with gasifying agents, e.g. water, carbon dioxide or air by reaction of hydrocarbons with gasifying agents using catalysts
  • C01B3/40—Production of hydrogen; Production of gaseous mixtures containing hydrogen by reaction of gaseous or liquid organic compounds with gasifying agents, e.g. water, carbon dioxide or air by reaction of hydrocarbons with gasifying agents using catalysts characterised by the catalyst
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  • C10G2/00—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon
  • C10G2/30—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen
  • C10G2/32—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts
  • C10G2/33—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts characterised by the catalyst used
  • C10G2/331—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts characterised by the catalyst used containing group VIII-metals
  • C10G2/332—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts characterised by the catalyst used containing group VIII-metals of the iron-group
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  • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
  • C01B2203/02—Processes for making hydrogen or synthesis gas
  • C01B2203/0205—Processes for making hydrogen or synthesis gas containing a reforming step
  • C01B2203/0227—Processes for making hydrogen or synthesis gas containing a reforming step containing a catalytic reforming step
  • C01B2203/0238—Processes for making hydrogen or synthesis gas containing a reforming step containing a catalytic reforming step the reforming step being a carbon dioxide reforming step
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  • C01B2203/08—Methods of heating or cooling
  • C01B2203/0805—Methods of heating the process for making hydrogen or synthesis gas
  • C01B2203/0861—Methods of heating the process for making hydrogen or synthesis gas by plasma
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  • C01B2203/10—Catalysts for performing the hydrogen forming reactions
  • C01B2203/1041—Composition of the catalyst
  • C01B2203/1047—Group VIII metal catalysts
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  • C01B2203/12—Feeding the process for making hydrogen or synthesis gas
  • C01B2203/1205—Composition of the feed
  • C01B2203/1211—Organic compounds or organic mixtures used in the process for making hydrogen or synthesis gas
  • C01B2203/1235—Hydrocarbons
  • C01B2203/1241—Natural gas or methane
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  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G2400/00—Products obtained by processes covered by groups C10G9/00 - C10G69/14
  • C10G2400/04—Diesel oil
• • C—CHEMISTRY; METALLURGY
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  • C10G2400/00—Products obtained by processes covered by groups C10G9/00 - C10G69/14
  • C10G2400/30—Aromatics
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/50—Improvements relating to the production of bulk chemicals
  • Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts

Definitions

• the present invention belongs to the field of chemical conversion, in particular the conversion of a gas or a mixture of gases comprising methane (CH 4 ) to produce molecules with high added value such as hydrogen (H 2 ), carbon monoxide (CO), gaseous hydrocarbons, liquid hydrocarbons, in particular oxygenated ones (alcohols, acids, ketones, esters, ethers, aldehydes, etc.), aromatics, as well as liquid fuels.
• the invention relates in particular to the CH 4 conversion process using a catalytic system in the presence of a cold plasma.
• the invention also relates to said catalyst capable of being activated by a cold plasma, for example generated by dielectric barrier discharge (DBD), thus allowing chemical conversion via plasma-catalysis.
• DBD dielectric barrier discharge
• the invention also relates to a process for preparing such a catalyst and to the use of the catalyst to produce molecules with high added value.
• GHG valorization is an effective strategy for GHG management, particularly in the energy and industrial process sectors.
• Methane (CH 4 ) is a powerful greenhouse gas, which is capable of trapping approximately 28 times more heat in the atmosphere than carbon dioxide (CO 2 ), over a period of 100 years. This means that despite its much lower concentration in the atmosphere compared to CO 2 , CH 4 contributes significantly to climate change. Reducing or recovering CH 4 emissions is therefore crucial to combating global warming.
• Catalytic reforming of CH 4 is a process widely used in industry to convert natural gas into H 2 or synthesis gas (H 2 and CO). It is based on different processes, namely steam reforming of CH 4 (SRM), partial oxidation of CH 4 and dry reforming of CH 4 with CO 2 (DRM).
• SRM steam reforming of CH 4
• DRM dry reforming of CH 4 with CO 2
• thermal catalysis processes such as dry reforming of CH 4 (DRM) require high gas pressures as well as a significant amount of energy.
• thermal energy in particular temperatures of the order of 700°C to 1000°C, to promote the activation of the catalyst, shift the thermodynamic equilibrium and guarantee acceptable yields.
• High-temperature catalytic reactions result not only in high energy consumption, but also in potential catalyst deactivation due to sintering of metal active sites and coke formation on the catalyst surface.
• Thermal processes are generally catalyzed by noble metals, such as Ir, Pd, Pt, Rh and Ru, in stable operation and with relatively low amounts of carbon deposited on the catalysts.
• DBD dielectric barrier discharge
• NTP non-thermal plasma
• An object of the present invention is to propose a CH 4 conversion process which meets these expectations.
• the conversion process of the present invention uses a catalytic system in the presence of a cold plasma.
• the catalytic system capable of being activated by cold plasma, comprising in particular a support which is a mixture of alumina and cerium in a molar ratio of between 80/20 and 30/70.
• the article by FOO, et al. [10] describes an alumina-based catalyst (Saint Gobain Nopro, USA) which is impregnated with the following solutions: 5Co-15Ni/80AI 2 O 3 and 2.5Ce-5CO-15Ni/77.5AI 2 O 3 .
• the catalyst can thus comprise cerium.
• the catalyst comprising an alumina-based support can then be impregnated with solutions potentially comprising cerium.
• this article does not describe a catalyst in which cerium is found at the support and is present in a molar quantity greater than 20%.
• the article by NANDINI, et al. [11] describes a catalyst of formula 13.5Ni-2K/10CeO 2 -AI 2 O 3 whose support consists of alumina and 10 wt. % cerium and which is then co-impregnated with nickel and potassium. See paragraph 2.1. This article does not describe a catalyst in which the support is an alumina/cerium mixture in which cerium is present in a molar quantity greater than 20% and which is used in a cold plasma process.
• a first object of the present invention relates to a process for converting a gas or a mixture of gases comprising methane (CH4), according to the CH 4 reforming reactions (DRM or SRM), characterized in that that it is carried out in the presence of a cold plasma and a catalyst, said catalyst comprising a support comprising a mixture of alumina and cerium in a molar ratio of between 80/20 and 30/70.
• the cold plasma is a plasma generated by dielectric barrier discharge (DBD).
• a second object of the present invention is a catalytic system, also called catalyst, making it possible to convert a gas or a mixture of gases comprising methane (CH 4 ), according to the methane reforming reactions (DRM or SRM ).
• This catalytic system which can for example be activated by a DBD plasma, makes it possible to resolve all the disadvantages of the prior art present in the thermal process (high temperature and pressure) and capable of producing synthesis gas (hydrogen , CO), liquid hydrocarbons, gaseous hydrocarbons, aromatics, oxygenated compounds (including alcohols, acids, ketones, esters, ethers, aldehydes), and/or liquid fuels under atmospheric conditions with high efficiency compared to to the studies described in the prior art.
• synthesis gas hydrogen , CO
• liquid hydrocarbons gaseous hydrocarbons
• aromatics aromatics
• oxygenated compounds including alcohols, acids, ketones, esters, ethers, aldehydes
• liquid fuels including alcohols, acids, ketones, esters,
• said catalyst comprises:
• a support which is a mixture of alumina and cerium in a molar ratio of between 80/20 and 30/70;
• a third object of the present invention relates to a process for preparing such a catalyst.
• a fourth object of the present invention relates to the use of the catalyst according to the present invention for the conversion of a gas or a mixture of gases comprising methane (CH 4 ), according to the reforming reactions of CH 4 (DRM or SRM), said conversion being carried out in the presence of cold plasma.
• the conversion of methane in the context of the present invention makes it possible to produce molecules with high added value, such as hydrogen (Hz), CO, gaseous hydrocarbons, liquid hydrocarbons, aromatics, oxygenated compounds (alcohols, acids , ketones, esters, ethers, aldehydes, etc.), and/or liquid fuels.
• the present invention makes it possible to overcome all the disadvantages of traditional thermal catalysis processes, as described in the prior art, and thus to obtain high catalytic and energy yields, and is thus capable of being exploited on a large scale. ladder.
• Figure 1 PFD functional diagram of a DBD plasma reactor. Plasma catalysis reactor for dry methane reforming. Figure 1 illustrates the experimental device (PFD diagram) used in an example of dry reforming of CH4, DRM, by a DBD plasma process coupled to the catalyst of the present invention.
• Figure 2 GC-FID spectrum of the organic liquid obtained by associating the 8Ni5Co2K-CeAI200 (50-50) catalytic system with the DBD plasma catalytic reactor.
• Figure 2 illustrates a GC-FID spectrum of the liquid obtained during the reaction of CH4 and CO2 in a DBD plasma reactor coupled with the catalyst 8Ni5Co2K-CeAI200 (50-50).
• FIG. 3 GC-MS spectrum (mass spectrometer) of the organic liquid obtained by associating the 8Ni5Co2K-CeAI200 (50-50) catalytic system with the DBD plasma catalytic reactor.
• Figure 3 illustrates a GC-MS spectrum of the liquid obtained during the reaction of CH4 and CO2 in a DBD plasma reactor coupled with the catalyst 8Ni5Co2K-CeAI200 (50-50).
• Figure 4 PFD functional diagram of a DBD plasma reactor. Plasma catalysis reactor for steam methane reforming.
• Figure 4 illustrates the experimental device (PFD diagram) used in an example of steam reforming of CH4, SRM, by a DBD plasma process coupled to the catalyst of the present invention.
• [0029] [0029] Table showing the catalytic activity (i.e., conversion, selectivity) obtained for several catalysts according to the invention and comparative, tested in DBD plasma, in the dry methane reforming reaction (DRM).
• [0030] [Table 2] Table showing the catalytic activity (i.e., conversion, selectivity) obtained for several catalysts according to the invention and comparative, tested in DBD plasma, in the steam methane reforming reaction (SRM).
• DBD – Dielectric Barrier Discharge designates, in the present invention, an electrical discharge created between two electrically conductive elements separated by one or more dielectric elements.
• dielectric designates, in the present invention, an electrical insulating material which makes it possible to ensure electrical insulation between the high voltage network associated with the electrode and the electrically and thermally conductive tube connected to ground via the reactor.
• This type of electrical insulating material is also used inside the DBD cell in order to generate a plasma by Dielectric Barrier Discharge (DBD) by promoting the accumulation of electrical charges on the surface of this material.
• DBD Dielectric Barrier Discharge
• catalyst and “catalytic system” are interchangeable and designate, in the present invention, a material promoting the chemical reaction of reactive species, for example reagent fluids.
• plasma-catalysis designates, in the present invention, the process which implements an electrical discharge of plasma coupled to a catalyst.
• support designates, in the present invention, a solid material or mixture of solid materials – which can in particular be characterized by its specific surface area, on which the promoter(s) is(are) deposited.
• promoter designates, in the present invention, a solid material or mixture of solid materials added to the surface of the support material, generally in small quantities, aimed at increasing the efficiency and the performance of the catalyst.
• hydrox must be understood as meaning “dihydrogen” or “H 2 ”.
• carbon monoxide must be understood as meaning “CO”.
• DRM Dry Reforming of Methane
• SRM Steam Reforming of Methane” or “steam reforming of methane” or “reforming of a gas mixture containing methane and water vapor”.
• methane reforming or “methane reforming reactions” should be understood as covering both dry methane reforming (DRM) and both steam methane reforming (SRM).
• a first object of the present invention relates to a process for converting a gas or a mixture of gases comprising methane (CH 4 ), characterized in that it is carried out in the presence a cold plasma and a catalyst, said catalyst comprising a support comprising a mixture of alumina and cerium in a molar ratio of between 80/20 and 30/70, and preferably nickel and optionally at least one promoter.
• the cold plasma is a plasma generated by dielectric barrier discharge (DBD).
• the methane (CH) conversion process according to the invention is carried out according to steam CH reforming reactions (DRM or SRM).
• the process for converting a gas or a mixture of gases according to the present invention comprises methane (CH 4 ) and water vapor (H 2 O).
• the process generates synthesis gas (ie, H 2 and CO), liquid oxygenated compounds and/or gaseous hydrocarbons.
• synthesis gas ie, H 2 and CO
• liquid oxygenated compounds ie, H 2 and CO
• methane (CH 4 ) conversion process is carried out according to the CH 4 reforming reaction (SRM).
• the process for converting a gas or a mixture of gases according to the present invention comprises methane (CH 4 ) and carbon dioxide (CO 2 ).
• This embodiment aims to produce molecules with high added value of synthesis gas (H 2 , CO), liquid hydrocarbons, gaseous hydrocarbons, aromatics, oxygenated compounds (in particular alcohols, acids, ketones, esters, ethers, aldehydes), and/or liquid fuels.
• the methane (CH 4 ) conversion process according to this embodiment is carried out according to the dry reforming reaction of CH 4 (DRM).
• a hydrocarbon in gas form When a hydrocarbon in gas form is generated, it is preferably ethane, ethene, propane, propene, butane, butene, pentane, hexane or their mixtures.
• an alcohol When an alcohol is generated, it is preferably methanol, ethanol, propanol, butanol, phenol, their isomers and/or their mixtures, more preferably methanol or ethanol .
• an acid When an acid is generated, it is preferably formic acid, acetic acid, propanoic acid, butanoic acid, pentanoic acid, gallic acid or mixtures thereof, more preferably acetic acid.
• an ether When an ether is generated, it is preferably methyl tert-butyl ether (MTBE), ethyl tert-butyl ether ETBE, cyclic ethers, non-cyclic ethers or mixtures thereof, more preferably MTBE.
• MTBE methyl tert-butyl ether
• ETBE ethyl tert-butyl ether
• cyclic ethers cyclic ethers, non-cyclic ethers or mixtures thereof, more preferably MTBE.
• a liquid hydrocarbon When a liquid hydrocarbon is generated, it is preferably molecules of aromatic types (benzene, toluene, xylene, etc.), more complex molecules or mixtures thereof, more preferably benzene.
• aromatic types benzene, toluene, xylene, etc.
• complex molecules or mixtures thereof more preferably benzene.
• a liquid fuel is generated, it is preferably C7->C15 or mixtures thereof, more preferably C12 diesel.
• the CH 4 conversion process is therefore carried out in the presence of a catalyst, as well as a cold plasma, preferably a plasma generated by dielectric barrier discharge (DBD).
• DBD dielectric barrier discharge
• Said catalyst comprises a support comprising a mixture of alumina and cerium in a molar ratio of between 80/20 and 30/70.
• Such a catalyst also preferably comprises nickel.
• Such a catalyst optionally comprises at least one promoter.
• the catalyst is used in combination with cold plasma. It should be noted that all of the characteristics described in connection with said catalyst are applicable to the conversion process of the present invention.
• the process for converting a gas or a mixture of gases comprising methane (CH 4 ), in particular according to the reforming reactions of CH 4 (DRM or SRM), is characterized in which is carried out in the presence of a cold plasma and a catalyst, said catalyst comprising a support comprising, or consisting essentially of, a mixture of alumina and cerium in a molar ratio of between 80/20 and 30 /70.
• the catalyst also comprises nickel.
• the present invention relates to a process for converting a gas or a mixture of gases comprising methane (CH 4 ) and carbon dioxide (CO 2 ), characterized in that it is carried out in the presence of a cold plasma and a catalyst, said catalyst comprising a support comprising, or consisting essentially of, a mixture of alumina and cerium in a molar ratio of between 80/20 and 30/70.
• the catalyst also comprises nickel.
• the present invention relates to a process for converting a gas or a mixture of gases comprising methane (CH 4 ) and water (H2O), characterized in that it is carried out in the presence of a cold plasma and a catalyst, said catalyst comprising a support comprising, or consisting essentially of, a mixture of alumina and cerium in a molar ratio of between 80/20 and 30/70.
• the catalyst also comprises nickel.
• the catalyst optionally comprises at least one promoter.
• the products obtained according to these conversion processes depend in particular on the molar ratio between the CH 4 , the CO 2 and/or the water vapor used to carry out the conversion reaction, a ratio that those skilled in the art can determine by depending on the desired products.
• the reduction in the CO 2 /CH 4 ratio leads to the generation of CH3 radicals, thus promoting the formation of long-chain products, such as ethanol, and reducing the selectivity towards methanol.
• the selected and prepared catalyst is placed between the electrodes of a DBD plasma reactor, allowing gaseous species to circulate through the catalyst, and is activated by electrical discharges at high voltage (of the order of kV) with a duration of the order of nanosecond to microsecond.
• high voltage of the order of kV
• This polarization combined with adsorption, desorption and catalyst/gas interaction, gives rise to the formation of plasma, as well as its activation and the production of hydrogen.
• Electrical energy supplied to the fixed bed in the form of sinusoidal or pulsed high voltage creates multiple currents on the HV (high voltage) carrier waves, during positive and negative bias.
• the catalyst according to the invention in the case where its components are in oxidized form, is advantageously reduced in situ under cold plasma, preferably a DBD plasma, under H 2 as landfill gas.
• a strong electric field is created, which activates said catalyst, more particularly between the grains of said catalyst or nearby, upstream or downstream of the catalyst, in the gas flow.
• This strong electric field is typically between 10 3 and 10 10 V /m and can vary over time. It allows the ionization of part of the gas and the excitation of atoms and molecules present in the gas phase.
• the walls of the reactor can typically be made of a metallic material; alternatively, in the case where a DBD plasma reactor is preferentially used for implementing the process of the present invention, the walls of the reactor are made of a dielectric material such as quartz, alumina or ceramic.
• the reactor can advantageously be cylindrical in shape.
• the strong electric field created is responsible for the negative or positive polarization of the catalytic sites.
• This polarization induces adsorption and desorption reactions even at low temperatures (for example at temperatures below 450°C, or even below 400°C).
• the working temperature is higher, generally 700°C to 1000°C.
• the reactor comprises in particular at least one inlet allowing its supply of gas to be converted, comprising CH 4 and CO 2 , or CH 4 and H 2 O in the form of gas, and an outlet for evacuating the products formed, in the form of liquid and/or gas.
• the molar ratio of carbon dioxide (CO 2 ) / methane (CH 4 ) or the molar ratio of water vapor (H Z O) / methane ( CH 4 ) in the gas mixture to be converted varies between 1 and 5, for example between 1 and 4, preferably between 1 and 3.
• the catalyst of the invention is activated by a DBD plasma by providing an electrical power of less than 30-35 W/g of catalyst (namely the catalytic system present in the reactor, c 'that is to say in the catalytic bed).
• the conversion reaction is advantageously carried out at a pressure close to or equal to atmospheric pressure (10 5 Pa), for example at a pressure between 1.10 4 Pa and 3.10 5 Pa.
• the conversion reaction can be carried out under conditions pseudo-adiabatic, i.e. without thermal insulation and without external heating, or in adiabatic conditions, i.e. with thermal insulation and without external heating, or in isothermal conditions, i.e. i.e. with thermal insulation and/or external heating.
• the DBD plasma is generated by application of a voltage between the two electrodes of between 1 and 25 kV, preferably between 5 and 20 kV, in particular with a frequency of between 1 kHz to 100 kHz.
• the hourly space velocity of the gas (GHSV) is in particular between 1000 h 1 and 150,000 h 1 , preferably less than 100,000 h 1 .
• a cooling system is optionally present between the container intended to receive the products generated by the conversion reaction and the outlet of the reactor so as to condense and eliminate the liquid products which could be formed during the conversion reaction.
• a second object of the present invention relates to a catalyst for the conversion of a gas or a mixture of gases comprising methane (CH 4 ), said conversion being carried out in the presence of a cold plasma and said catalyst comprising a support comprising a mixture of alumina and cerium in a molar ratio of between 80/20 and 30/70.
• the conversion is carried out according to the CH 4 reforming reactions (DRM or SRM).
• the catalyst of the present invention does not comprise a noble metal, such as ruthenium (Ru), iridium (Ir), palladium (Pd), platinum (Pt) or rhodium (Rh).
• a noble metal such as ruthenium (Ru), iridium (Ir), palladium (Pd), platinum (Pt) or rhodium (Rh).
• the catalyst of the present invention can be activated by cold plasma, during its use in the process of the invention.
• said catalyst comprises:
• a support which comprises a mixture of alumina and cerium in a molar ratio of between 80/20 and 30/70, and
• a promoter for example of the alkali metal type, of the alkaline earth type, of the transition metal type and/or of the lanthanide type, that is to say a promoter comprises at least one chemical element belonging to metals alkaline, alkaline earth, transition metals, and/or lanthanides (including mixtures thereof).
• said catalyst essentially consists of:
• a support which comprises a mixture of alumina and cerium in a molar ratio of between 80/20 and 30/70, and
• the catalyst does not include a promoter.
• said catalyst essentially consists of:
• a support which comprises a mixture of alumina and cerium in a molar ratio of between 80/20 and 30/70
• At least one promoter of the alkali metal type, of the alkaline earth type, of the transition metal type and/or of the lanthanide type that is to say a promoter comprising at least one chemical element belonging to the alkali metals, alkaline- earths, transition metals, and/or lanthanides (including mixtures thereof).
• the catalytic system is characterized in that the support comprises a mixture of alumina and cerium.
• the support essentially consists of a mixture of alumina and cerium.
• it includes cerium-modified alumina.
• catalytic system and “catalyst” are interchangeable.
• said catalytic system is called a mono/bi/tri metal catalytic system.
• monometallic system, bimetallic system and trimetallic system concerns in particular the species present in the catalyst without taking into account the support used and the nickel. For example, when the catalyst is doped with a promoter in addition to nickel, we speak of a monometallic catalyst; when the catalyst is doped by two promoters in addition to nickel, we speak of a bimetallic catalyst; when the catalyst is doped with three promoters in addition to nickel, we speak of a trimetallic catalyst.
• the support used in the context of the present invention is chosen in particular for its capacity to adsorb the reagents and more particularly CO 2 , for its thermal stability and for its optimized specific surface area aimed at promoting the plasma-catalyst interface, which makes it possible to offer various reaction pathways in surface chemistry. It is also chosen for its dielectric properties which can impact plasma properties and modify discharge behavior of the DBD plasma, the electric field and the electron density due to the dielectric permittivity and the polarization effect which gives rise to the local electric field.
• the catalyst support comprises, in particular is constituted by or consists of, a mixture of alumina and cerium. More precisely, the support according to the invention comprises a mixture of alumina and cerium, in particular a mixed oxide AICe, and the alumina/cerium (Al/Ce) molar ratio is between 80/20 and 30/70.
• the alumina/cerium (Al/Ce) molar ratio is for example between 75/25 and 35/65, between 73/28 and 40/60 or between 71/29 and 42/58.
• the alumina/cerium ratio can, for example, be approximately 70/30 +1.
• the Al/Ce molar ratio impacts the physicochemical properties (basicity, acidity, reducibility, oxygen mobility due to the presence of inherent defects present on said surface, etc.) as well as the textural properties (volume porous, pore diameter, specific surface area, etc.) and electrical properties (permittivity, conductivity, etc.), which will in turn modulate the catalytic performance of the system.
• the inventors noted that the presence of cerium in the crystal lattices of the alumina allows a higher number of defects on the surface of the support, which promotes the mobility of oxygen on the surface of said support and thus leads to improved performance. increased catalytics.
• the support consists of a mixture of alumina oxide, for example Al 2 O 3 and cerium oxide CeO 2 .
• the alumina can have any specific surface area (expressed as BET surface m 2 /g) -
• the specific surface area of the alumina is at least 20 m 2 /g and can notably vary between 50 and 1,000 m 2 /g.
• the specific surface area of alumina is 200 m 2 /g or 260 m 2 /g.
• the catalyst comprises a support comprising alumina having a specific surface area varying between 50 and 1,000 m 2 /g, between 100 and 800 m 2 /g, between 150 and 300 m 2 /g . g or between 180 and 250 m 2 /g.
• the catalyst when it comprises nickel, it can be in any of its oxidation states and in particular in metallic form (in its oxidation state 0) or in oxide form its d state. II oxidation (eg in the form of nickel (II) oxide (NiO)).
• the mass content of nickel in the catalyst can advantageously vary between 0.1% to 50% by weight relative to the weight of the support, for example between 1% and 40% or between 2% and 30%; preferably, it is less than 25% or less than 20%.
• weight of the support we mean “weight of the support including alumina”, including when the support comprises elements other than alumina.
• the catalytic system comprises approximately 8% ⁇ 1% or 10% ⁇ 1% by weight of nickel relative to the weight of the support.
• a catalyst comprising 8% by weight of nickel relative to the weight of a support comprising alumina and cerium is designated by “8Ni-CeAI”, “8Ni-CeAI” or even “8Ni- CeAI”.
• the present invention relates to a catalyst activated by cold plasma.
• the catalytic performance of the reaction is improved, that is to say the conversion rates of CO 2 and/or CH 4 and/or the selectivity towards the desired product (liquid fuel and/or synthesis gas).
• the catalyst combination according to the invention / cold plasma advantageously makes it possible to produce such molecules in a single step from CH 4 .
• the catalytic system according to the present invention does not include a promoter.
• the catalytic system according to the present invention comprises at least one promoter, that is to say one or more promoters.
• Said at least one promoter acts as a dopant and impacts the physicochemical, textural as well as conductive properties of the catalytic system.
• the promoter according to the invention advantageously has physicochemical surface properties suitable for helping to fix the reagents as well as suitable dielectric properties which make it possible to improve the conductivity of the resulting catalytic system and which logically lead to the generation of CH3 radicals from CH 4 , thus promoting the formation of long-chain carbon products (long-chain oxygenated species and particularly long-chain liquid hydrocarbons).
• the at least one promoter may in particular comprise a chemical element selected from the group consisting of alkalis, transition metals, alkaline earths, lanthanides and their mixtures; more particularly, in the group consisting of alkalis, such as potassium (K), transition metals such as cobalt (Co), copper (Cu), zinc (Zn), manganese (Mn), yttrium (Y), and iron (Fe), alkaline earths such as magnesium (Mg), lanthanides such as yttrium or lanthanum (La), and mixtures thereof.
• the promoter is in any of its oxidation states and in particular in metallic form or in oxide form.
• the alkali metals can be selected from the group consisting of lithium, sodium, potassium, rubidium, cesium and francium.
• the promoter comprises a chemical element which is an alkali metal, this is, preferably, potassium (K) or cesium (Cs), and even more preferably, potassium (K).
• the transition metals can be selected from the group consisting of copper, cobalt, silver, iron, zinc, manganese, vanadium, manganese, chromium , yttrium, titanium and tantalum.
• the promoter comprises a chemical element which is a transition metal, this is preferably cobalt (Co) or iron (Fe), and even more preferably, cobalt (Co).
• the alkaline earths can in particular be selected from the group consisting of magnesium, barium, calcium and strontium.
• the promoter comprises a chemical element which is an alkaline earth, this is preferably magnesium (Mg).
• the lanthanides can be selected from the group consisting of lanthanum, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium.
• the promoter comprises a chemical element which is a lanthanide, this is preferably yttrium (Y) or lanthanum (La), and even more preferably, yttrium (Y).
• the promoter of the catalyst is selected from the group consisting of potassium (K), cesium (Cs), cobalt (Co), iron (Fe), magnesium (Mg), yttrium (Y), lanthanum (La), manganese (Mn) and their mixtures. More preferably, the promoter is selected from the group consisting of potassium (K), cobalt (Co), iron (Fe), yttrium (Y) and mixtures thereof.
• the mass content of promoter in the catalyst varies between 0.1% and 40% by weight relative to the weight of the support, for example between 0.2 and 30% by weight. , in particular between 0.5% and 25% by weight, preferably between 1% and 20% by weight, in particular between 1% and 15% by weight, even more preferably between 1% and 9% by weight relative to the weight of the support.
• the promoters used for the preparation of the catalysts of the present invention are found in any oxidation state, and in particular in metallic form or in oxide form. They are therefore likely to include other chemical elements, which do not enter into the calculation of the claimed mass content.
• a promoter for an 8Ni2K-CeAI catalyst, if we use 1 g of support comprising nickel, we then use 0.051 g of KNO 3 promoter (molar mass: 101.1 g/mol), which corresponds to 0.02 g of K (molar mass: 39.1 g/mol), or 2% by weight of potassium relative to the weight of the support.
• the mass content of promoter is 2% by weight relative to the weight of the support.
• the quantity of nickel and/or promoter can be adjusted depending on the nature of the promoter used and/or the type of conversion reaction implemented, that is to say according to the type of product generated by the conversion reaction, in particular reforming methane into synthesis gas and/or hydrocarbons.
• the catalyst according to the present invention is monometallic, that is to say it comprises a single promoter in addition to nickel.
• the catalyst according to the present invention comprises a single promoter which comprises potassium (K).
• the chemical element potassium can, for example, be brought into the catalyst in the form of a precursor, for example in the form of potassium nitrate KNO 3 .
• the catalyst according to the present invention comprises at least two promoters in addition to nickel, that is to say two or more promoters, for example two promoters (it is then bimetallic ) or three promoters in addition to nickel (it is then trimetallic).
• the catalyst is bimetallic, doped with two promoters in addition to nickel, one of the two promoters of which is potassium (K), its mass content in the catalytic system is preferably approximately 2% ⁇ 0.2% by weight relative to the weight of the support, while the second promoter is cobalt (Co), its mass content in the catalytic system is preferably approximately 5% ⁇ 0.5% by weight relative to the weight of the support .
• K potassium
• Co cobalt
• the catalytic system can be in different forms (balls, monoliths, powders, etc.).
• the grains forming the powder can for example have an average size of between 1 pm and 1 mm, for example between 100 pm and 1 mm, in particular between 200 pm and 800 pm, preferably around 600 pm ⁇ 20 pm.
• the grain size can in particular be adapted depending on the scale of production used.
• the catalytic system can also be found in the form of balls (in particular by compression of the powder in a mold) having an average size less than 5 cm.
• the alumina/ceria support, the nickel and optionally the promoter(s) form a homogeneous mixture.
• the nickel and the promoter(s) are distributed uniformly throughout the volume of the catalyst.
• said catalyst comprises:
• a support which comprises a mixture of alumina and cerium in a molar ratio of between 80/20 and 30/70, and
• At least one promoter selected from the group consisting of potassium (K), cesium (Cs), cobalt (Co), iron (Fe), magnesium (Mg), yttrium (Y), lanthanum (La) and mixtures thereof, preferably potassium (K) or a mixture of potassium (K) and cobalt (Co).
• the catalytic system is prepared by bringing the support into contact with a nickel precursor and at least one precursor of the promoter (or promoters). This step makes it possible to form a solid comprising the support, the nickel and the promoter (or promoters).
• This contacting step is possibly: preceded by a step of modifying the support; and/or followed by a step of calcination of the mixture thus obtained, itself being optionally followed by a step of reduction of this calcined mixture.
• the calcination step leads to the oxidation of the various components of the catalytic system (support, nickel and promoter).
• This optional calcination step can itself be optionally followed by a reduction step, so as to change the oxidation state of the nickel and the promoter (to have nickel and the metallic promoter), and possibly that of the support. .
• the reduction can be total or partial, that is to say that only part of the components of the catalytic system can be reduced.
• the reduction step can be carried out in situ in the non-thermal plasma device under hydrogen.
• the step of bringing the support into contact with a nickel precursor and a precursor of the promoter can be carried out for example by impregnation or by coprecipitation.
• the nickel precursor and the promoter precursor can be any chemical compound, or mixture of chemical compounds, containing the metal used as active metal/ promoter and more particularly may be a salt of said metal, an oxide of said metal or a mixture of these, preferably a salt of said metal or a mixture of salts of said metal.
• the salt (denotes a non-hydrated salt or a hydrated salt, or even a multi-hydrated salt) of said metal can for example be chosen from chloride, nitrate, sulfate, carbonate, acetate, acetylacetonate, tartrate, and the citrate of said metal and their mixtures, preferably the nitrate of said metal.
• the precursor can be a mixture of different types of salts and/or oxides of these metals.
• the process for preparing the catalytic system comprises a step 1) of preparing the support and a step 2) of bringing the support into contact with a nickel precursor and at least one precursor of the promoter.
• contacting is carried out by impregnation. More precisely, according to this embodiment, the method comprises the following steps:
• step a) preparation of support: a) preparation of an aqueous solution comprising a cerium precursor and an alumina oxide or comprising a cerium precursor and an alumina precursor.
• the support precursor corresponds to a cerium precursor, an alumina precursor or a mixture of 2 cerium precursors and an alumina precursor.
• a solution of cerium precursor and a solution of alumina precursor are advantageously prepared separately then mixed in a ratio making it possible to obtain the desired Al/Ce molar ratio in the mixture, in particular the final mixed oxide, cerium and alumina.
• the drying step can be carried out for example at a temperature below 150°C, typically at a temperature of around 100°C, typically for a period ranging from 7 hours to 48 hours.
• step c) The product resulting from step c) is then calcined, for example at a temperature between 300°C and 600°C.
• This calcination step can be carried out for 3 hours or more, for example for a period ranging from 3 hours to 6 hours.
• This step results in the thermal decomposition of nitrates to obtain oxides.
• step a an appropriate mass of each precursor is added to an appropriate volume of solvent, for example water.
• solvent for example water.
• suitable mass and suitable volume we mean the adequate quantities of precursors and solvent (in particular water) to obtain the desired mass contents of nickel and promoter in the final catalytic system.
• step d) recovery of the solid comprising the support, the nickel and the promoters obtained in step b) by elimination of excess water, in particular by evaporation of the water or filtration, then drying of the resulting solid.
• the drying step can be carried out for example at a temperature below 150°C, typically at a temperature of around 100°C, typically for a period ranging from 7 hours to 48 hours.
• step c) The product resulting from step c) is then calcined, for example at a temperature between 300°C and 600°C.
• This calcination step can be carried out for 3 hours or more, for example for a period ranging from 3 hours to 6 hours.
• This step results in the thermal decomposition of nitrates to obtain oxides.
• This first embodiment is also called wet impregnation process. It consists of impregnating the support with the nickel precursor and the promoter precursor.
• the process for preparing the catalytic system comprises a support preparation step and bringing the support into contact with a nickel precursor and the promoter, this contacting being carried out by co -precipitation and comprising the following steps:
• a') preparation of an aqueous solution comprising a nickel precursor and the promoter precursors (this step is identical to step 2 a) of the wet impregnation process).
• b') addition of the support to the solution resulting from step a') to give a suspension (this step is identical to step 2 b) of the wet impregnation process).
• a base is added to the suspension resulting from step b').
• This base is advantageously a hydroxide salt such as sodium or potassium hydroxide or sodium or potassium carbonate, in particular sodium hydroxide. It can be used in the form of a solution, particularly aqueous.
• Step c') is advantageously carried out at a temperature between 60°C and 100°C, in particular between 70°C and 90°C, preferably equal to approximately 80°C.
• This step aims to precipitate the nickel hydroxide and the hydroxide of the metal used as promoter on the surface of the support.
• the mixing, in particular by stirring, is advantageously carried out at a temperature between 60°C and 100°C, preferably equal to approximately 80°C. This mixing step can be carried out for a period of 2 hours or more, typically for around 3 hours.
• step e' recovery of the solid comprising the support, the nickel and the promoter obtained in step d') and its calcination to give the catalyst known as the catalytic system (this step is identical to step 2 e) of the impregnation process by wet method).
• This method makes it possible to precipitate nickel hydroxide and the hydroxide of the metal used as a promoter on the surface of the support.
• the present invention also relates to the use of the catalyst, in the presence of cold plasma for the conversion of a gas or a mixture of gases comprising CHU, according to the CHi reforming reactions (DRM or SRM), said catalyst comprising a support which is a mixture of alumina and cerium in a molar ratio of between 80/20 and 30/70.
• the cold plasma is a plasma generated by dielectric barrier discharge (DBD).
• the present invention relates in particular to the combined use of the catalyst of the present invention, as well as a cold plasma, for the conversion of a gas mixture comprising methane (CHi) and water vapor (H2O), according to the steam reforming reaction (SRM), aimed at generating syngas, liquid oxygenates and/or gaseous hydrocarbons.
• SRM steam reforming reaction
• the present invention also relates to the combined use of the catalyst of the present invention, as well as a cold plasma, for the conversion of a mixture of gases comprising methane (CH4) and carbon dioxide (CO2) , according to the dry methane reforming reaction (DRM), aimed at producing high value-added molecules from synthesis gas (hydrogen, CO), liquid hydrocarbons, gaseous hydrocarbons, aromatics, compounds oxygenated (including alcohols, acids, ketones, esters, ethers, aldehydes), and/or liquid fuels.
• synthesis gas hydrogen, CO
• liquid hydrocarbons gaseous hydrocarbons
• aromatics aromatics
• compounds oxygenated including alcohols, acids, ketones, esters, ethers, aldehydes
• the inventors have, in fact, realized that the combination of a catalyst according to the present invention, and a cold plasma, preferably a plasma generated by barrier discharge dielectric (DBD), showed increased efficiency to convert a gas mixture including methane according to methane reforming reactions (DRM or SRM).
• a cold plasma preferably a plasma generated by barrier discharge dielectric (DBD)
• DBD barrier discharge dielectric
• the catalyst is prepared by two successive impregnation sequences.
• a new step of impregnation only of the nickel and the promoter(s) this time is carried out on the catalytic system resulting from the first impregnation.
• the nickel catalysts doped with the promoter (metal M) were prepared by the method from an aqueous solution of Ni(NO3)2-6H2O (Sigma-Aldrich and one or more promoter precursors chosen among: Cu(NO 3 )2.3H 2 O, Co(NO 3 )2.6H 2 O, Mn(NO 3 ) 2.4H 2 O, La(NO 3 ) 2 .6H 2 O, Y(NO 3 ) 2 .6H 2 O, Fe(NO 3 ) 2 .9H 2 O, Mg(NO 3 ) 2 .6H 2 O, Zn(NO 3 ) 2 .6H 2 O,NaNO 3 , and KNO 3 (all commercial, Sigma-Aldrich), depending on the desired promoter.
• Ni(NO3)2-6H2O Sigma-Aldrich and one or more promoter precursors chosen among: Cu(NO 3 )2.3H 2 O, Co(NO 3 )2.6H 2 O, Mn(NO 3 ) 2.4H 2 O
• the nickel content is 8% by weight relative to the weight of the support
• that of Co promoter is 5% by weight relative to the weight of the support
• that of promoter K is 2% by weight relative to the weight of the support.
• a promoterless 10Ni-CeAI catalyst was also prepared as an inventive example according to the present invention.
• nickel salt and that of the promoter precursor(s) are dissolved in a volume of water of 50 mL, at room temperature and with stirring.
• the appropriate mass of support is added to the aqueous solution containing the mixture of metal salts and kept stirring for 2 hours.
• nickel nitrate content 8% by weight
• 0.155 g of cobalt nitrate content 5% by weight
• 0.052 g of potassium nitrate content 2% by weight
• 1 g of support are mixed according to the previous procedure.
• the mixture is then placed in a rotary evaporator for 2 hours at 65°C, in order to eliminate excess water.
• the procedure for the production of hydrogen and liquid hydrocarbons by means of a catalytic plasma reactor is as follows: 357 mg of catalyst to be tested, corresponding to a GHSV (Gas Hourly Space Velocity of 17,000 h 1 , are placed between the electrodes of the DBD reactor; the reactor is supplied with a mixture of methane and carbon dioxide (50% vol CO 2 ) with a total flow rate of 120 ml/min STP (Standard Temperature and Pressure) (60 ml/ min STP CO 2 and 60 ml/min STP CH 4 ), at atmospheric pressure and a temperature of 20°C.
• STP Standard Temperature and Pressure
• the procedure for the production of hydrogen and gaseous hydrocarbons by means of a catalytic plasma reactor is as follows: 400 mg of catalyst to be tested, and a total flow rate of 150 ml/min STP (Standard Temperature and Pressure) (75 ml/min STP H 2 O and 75 ml/min STP CH 4 ), at atmospheric pressure and at a temperature of 20°C, corresponding to a GHSV (Gas Hourly Space Velocity) of 20 00 h 1 , are placed between the electrodes of the plasma reactor DBD; the reactor is supplied with a mixture of gases containing carbon monoxide and water vapor; water is propelled first by an inert gas (Ar), then circulated through a mass flow controller, it is then vaporized and mixed with carbon monoxide using a controlled evaporation and mixing system ( Bronkhorst CEM). The gas mixture is then transported along a heated pipe to the interior of the DBD plasma reactor.
• STP Standard Temperature and Pressure
• a non-thermal electric barrier discharge (DBD) plasma was created between two electrodes: a cylindrical copper electrode placed inside an alumina tube (3 mm in diameter), surrounded by a coaxial quartz tube (10 mm internal diameter, 1 mm thick), and a steel wire wrapped around the outer surface of the quartz tube, acting as a ground electrode (grounded via an external capacitor of 2nF).
• a discharge was supported in a 2.5 mm gap, covering a length of approximately 1 cm.
• the as-synthesized catalytic systems were reduced in situ under non-thermal DBD plasma under H2 as the discharge gas for a duration of 60 min.
• Table 1 below indicates the catalysts tested and shows the results of the catalytic activity obtained in terms of conversion, selectivity and yield, from a mixture of gases comprising CH 4 and CO 2 (DRM).
• the 8Ni2K-CeAI200 catalysts according to the invention 8i, 13i and 18i, which have an Al/Ce molar ratio in the range 80/20 and 30/70, have a better catalytic efficiency in conversion of CH 4 and of CO 2 compared to a catalyst not comprising cerium (8NÎ2K-AI200 comparative test 7c), or compared to catalysts comprising cerium outside the claimed molar ratio (comparative tests 17c, 19c and 20c).
• the catalytic efficiencies in conversion of CH 4 and CO 2 of the catalysts according to the invention are significantly greater than 50%, while those of the comparative catalysts are all less than 50%.
• Table 2 indicates the catalysts tested and shows the results of the catalytic activity obtained in terms of conversion, selectivity and yield, from a mixture of gases comprising CH 4 and I' H2O (SRM).

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