Chemical reactor with MIEC membrane

Abstract

The disclosure pertains to a chemical reactor comprising a first and a second chamber, a membrane comprising an oxygen transporting mixed ionic-electronic conducting material and separating the first and second chamber, an inlet of the first chamber, an inlet of the second chamber, and an outlet of the second chamber.

Description

P134924PC00 Title: CHEMICAL REACTOR WITH MIEC MEMBRANE Field

[0001] The disclosure broadly pertains to a chemical reactor comprising a mixedionic-electronic conducting membrane, and various other embodiments. Introduction

[0002] Arratibel Plazaola et al. describe various aspects of the application of MixedIonic-Electronic Conducting (MIEC) membranes in membrane reactors (Arratibel Plazaola et al., Mixed Ionic-Electronic Conducting Membranes (MIEC) for Their Application in Membrane Reactors: A Review. Processes 2019, 7, 128, https: / / doi.org / 10.3390 / pr7030128). A further reference discussing mixed-conductor membranes, in particular for oxygen transport, is: P.-M. Geffroy et al., Chemical Engineering Science 162 (2017) 245–261.

[0003] It is desired to use electrical energy for conducting chemical reactions, aselectrical energy can be obtained from clean energy sources such as e.g. solar energy and wind energy. Summary

[0004] The disclosure pertains to a chemical reactor. The disclosure provides, in anembodiment, a chemical reactor comprising a first chamber and a second chamber, a membrane, an inlet for providing a first gas in the first chamber, an inlet for providing a second gas in the second chamber, an outlet for a gaseous product stream from the second chamber. Preferably, the membrane comprises an oxygen transporting mixed ionic-electronic conducting material. The membrane separates the first and second chamber, and the membrane is preferably configured for transport of ionic species from the first to the second chamber. The chemical reactor comprises a plasma generator for forming a plasma in the second chamber. The chemical reactor is preferably for nitrogen fixation.

[0005] The invention also provides a plant (e.g. reactor system) comprising thechemical reactor of the invention and a downstream processing unit arranged downstream of said outlet of the second chamber for processing said gaseousstream from said second chamber. The downstream processing unit is e.g. an absorption unit. The plant is e.g. a plant for producing nitric acid.

[0006] The disclosure also provides a process carried out in a chemical reactoraccording to the invention, the process comprising supplying a gaseous first reactant to the first chamber, supplying a gaseous second reactant to the second chamber, activating the second reactant in the second chamber by a plasma generated by said plasma generator, and causing transport of species of the first reactant from the first chamber through the membrane to the second chamber.

[0007] The disclosure also provides a process of producing NOx carried out in achemical reactor according to the invention. The process involves in embodiments the transport of oxygen species through the membrane from a gas phase in the first chamber to the second chamber, e.g. the process may comprise causing such transport; supplying N2 to the inlet for the second reactant and withdrawing a gas stream comprising NOx through said outlet of said second chamber.

[0008] Also provided is a nitric acid production process that comprises reacting theNOx withdrawn from the second chamber with absorbent, preferably H2O, and optionally with O2, to form nitric acid; in other words the process comprises contacting the gas stream from the second chamber with an absorption liquid.

[0009] Also provided is an ammonium nitrate production process that comprisesneutralizing the nitric acid with ammonia to form ammonium nitrate. Brief description of the drawings

[0010] Figure 1 schematically illustrates an experimental set-up for a reactor usedin Example 1.

[0011] Figures 2-7 illustrate experimental results obtained in Example 1.

[0012] Figures 8-10 illustrate process schemes used in Example 2.

[0013] Figure 11 illustrates a process schemes described in Example 3.

[0014] Figure 12 illustrates an example process scheme according to the invention.

[0015] Figure 13 illustrates an example process scheme according to the invention.

[0016] Any embodiments illustrated in the figures are examples only and do notlimit the invention.Detailed description

[0017] The chemical reactor of the invention comprises a membrane, an energysource for activating a reactant, and means for separately introducing reactants into the reactor.

[0018] The present invention is based on the judicious combination of using amixed ionic-electronic conducting (MIEC) membrane in a chemical reactor in combination with a plasma generator. A membrane indicates an element separating two chambers or zones for mass flow of at least some species, e.g. by restricting the mass flow through the membrane of at least some species, and may permit mass flow of certain species.

[0019] The MIEC membrane is, in particular, configured to introduce a firstreactant from a first chamber of the reactor through the membrane into a second chamber of the reactor. In particular, the chemical reactor is configured for transport of ionic species (e.g. oxygen ions) from the first chamber into the second chamber, or at least from the membrane surface exposed to the first chamber, through the membrane, to the membrane surface exposed to the second chamber. Hence, the chemical reactor is configured (and operated) to supply reactant through the membrane in the direction from the first to the second chamber, as distinct from withdrawing a product from the second chamber.

[0020] By introducing the first reactant into the second chamber through amembrane, the reactant is introduced in a spatially distributed manner, namely over the surface area of the membrane. This manner of introducing reactant into the second chamber can be contrasted with using a nozzle which would introduce the reactant in a point-like manner.

[0021] The plasma is generated in a plasma generator using electrical energy andcan activate a second reactant in said second chamber of the reactor and provide activated second reactant to species of the first reactant at the membrane surface that is exposed to the second chamber or in the second chamber in the vicinity of the membrane. Hence, the chemical reactor is configured for conducting the reaction between the first and the second reactant (activated) species at the membrane surface that is exposed to the second chamber or in the second chamber in the vicinity of the membrane.

[0022] The invention also provides a process carried out in a chemical reactoraccording to the invention, the process comprising supplying a gaseous first reactant to the first chamber, supplying a gaseous second reactant to the second chamber, plasma-activating the second reactant in the second chamber (i.e. activating the second reactant using a plasma) using a plasma generated by said plasma generator, and causing transport of species of the first reactant from the first chamber through the membrane to the second chamber. Advantageously, electricity can be used to create the plasma to activate the second reactant. Preferably said electricity is generated from energy sources such as, e.g., solar and wind energy, which have e.g. low CO2 emissions.

[0023] The process involves activating the second reactant by the plasma, incombination with introducing the first reactant into the reactor advantageously using the MIEC membrane.

[0024] The first reactant is, in particular, provided as a gas stream comprising O2,for example, air, enriched air, or O2 in the first chamber. Oxygen species are transported through the membrane and made available at the permeate side surface of the membrane. Here they may react with activated nitrogen species from the plasma.

[0025] The combination of a plasma and a MIEC membrane used for supply of areactant may advantageously permit the direct reaction between such oxygen species and plasma-activated species in the second chamber.

[0026] In an embodiment, the second reactant is N2 and the plasma may provideactivated nitrogen species. In this embodiment, the product formed in the second chamber is NOx. The NOx can be converted further to nitric acid, for instance downstream of a product outlet of the second chamber. Nitric acid is a valuable bulk chemical and can be used, for instance, for the production of nitrate salts by neutralization. Such nitrate salts can be used e.g. as fertilizer.

[0027] The chemical reactor is hence in a preferred embodiment suitable for, orconfigured for, nitrogen fixation, in particular nitrogen fixation in the second chamber. The same applies to the plant. The chemical reactor is preferably a NOx production unit.

[0028] In a reference industrial process for the production of nitric acid, nitric acidis produced by the Ostwald process, based on the catalytic oxidation of NH3 to formNO and H2O, followed by the conversion of NO into NO2 and into HNO3. Embodiments of the present invention allow for the production of HNO3 from N2 and O2, e.g. provided as air, and H2O; without the need for the production of NH3. This may contribute to providing a flexible process for the production of HNO3 using electricity as energy supply. By way of background reference, Patil et al., Plasma N2-fixation: 1900–2014, Catalysis Today, 256(1) p.49-66 (2015) provides a review of plasma nitric oxide synthesis.

[0029] Using O2 as a reactant is thermodynamically advantageous compared to aprocess using H2O as reactant in view of the enthalpy of formation.

[0030] Using a MIEC membrane allows to deliver oxygen species to the plasma orto a zone downstream of the plasma generator in a spatially selective way, i.e. to maintain a concentration gradient of oxygen in the second chamber, yet distributed over the membrane surface. In this way, the oxygen species are not transported directly through the plasma, thereby limiting or avoiding the activation of oxygen species on the permeate side of the membrane by the plasma. Moreover, the products formed on or in the vicinity of the membrane have an exposure to the N2 that is activated by the plasma in the plasma-generating zone that is spaced apart from the membrane, which can contribute to selectivity compared to air plasma. Furthermore, without wishing to be bound by way of theory, the plasma activated nitrogen species may react with oxygen active species (ions and radicals) that are formed by the membrane.

[0031] Overall, an embodiment of the process of the invention advantageouslyprovides for a green process for producing NOx using electricity to plasma activate N2.

[0032] An embodiment of the invention provides a chemical reactor. The reactorcomprises a plasma generator and a membrane comprising a mixed ionic-electronic conducting material.

[0033] The reactor also comprises a first and a second chamber. The first and thesecond chamber are delimited by respective walls of the reactor. The membrane provides a separation between the first and the second chamber.

[0034] The reactor comprises an inlet for providing a first gas in the first chamber,and a separate inlet for providing a second gas in the second chamber. The reactor also comprises at least an outlet for a gaseous stream, e.g. a gaseous productstream, i.e. a gaseous stream comprising a gaseous product, from the second chamber. Note that the gaseous product may be reacted further. The gaseous product is in particular the product of a chemical reaction carried out in the second chamber. The reactor may also comprise a gas outlet of the first chamber.

[0035] The chemical reactor is preferably configured for nitrogen fixation, inparticular for nitrogen fixation in the second chamber. The chemical reactor is configured for transport of ions, in particular O2-ions, through the membrane from the membrane surface exposed to the first chamber to the membrane surface exposed to the second chamber.

[0036] The plasma generator is configured for forming a plasma in the secondchamber. The plasma is preferably of the non-thermal type. Alternatively, the plasma generator forms a plasma of the thermal type.

[0037] Known types of plasma generators can be used. The plasma generator forinstance comprises one or more selected from the group consisting of: a laser induced plasma generator, an arc plasma generator (e.g. DC / AC arc plasma torch and gliding arc plasma generator), a radio frequency plasma generator, a microwave plasma generator, a dielectric barrier discharge plasma generator, and a glow discharge plasma generator. This list is non-exhaustive. In an embodiment, the plasma generator for instance comprises one or more selected from the group consisting of: a radio frequency plasma generator, a microwave plasma generator, and a dielectric barrier discharge plasma generator. In some embodiments, a single type of plasma generator is used. One or more plasma generators can be used; for instance two or more plasma generators are used in parallel or in series. The plasma generator may comprise, or consist of, elements that are external of the second chamber and that are not directly in contact with the gas in the second chamber. Preferably, the second chamber comprises a zone (plasma formation zone) that is in the vicinity of the plasma generator, in which zone plasma is generated in operation. Preferably, the plasma generator is configured for creating a plasma in a plasma generation zone of the second chamber.

[0038] The second chamber is for instance provided with a gas flow direction fromthe gas inlet to the gas outlet, through or along the first the plasma formation zone and subsequently along the membrane. For instance, one or more tubular membranes are provided in the second chamber and the gas flows through thesecond chamber along the membrane tubes from the plasma formation zone to the gas outlet.

[0039] For example, the projection of the plasma generator perpendicular to thegas flow direction through the second chamber provides the plasma formation zone, e.g. in case of microwave plasma and dielectric barrier discharge.

[0040] In some embodiments, the membrane is contacted with the plasma. In someembodiments, the membrane is contacted with the afterglow zone of the plasma. In some embodiments, the membrane is arranged downstream, with respect to the gas flow, of the afterglow of the plasma and spaced from the zone wherein the afterglow is provided. Spacing, in operation, between the plasma or plasma generator, and the membrane can vary over a wide range, e.g. from at least 0.10 mm and / or up to 50 cm.

[0041] For example, a gas flow is supplied through the plasma generation zone andfrom this zone to the membrane and subsequently the flow will go to the outlet of the second chamber. The plasma generation zone and the membrane are for example spaced apart and provide an intermediate zone between them, which zone in operation receives a gas flow comprising plasma-activated species; and gas is withdrawn from this zone through the product outlet. This intermediate zone is typically comprised in the second chamber.

[0042] For instance in operation, a gas flow comprising plasma-activated speciesimpinges on the membrane or is in contact with the membrane, in particular with a permeate side of the membrane.

[0043] Preferably, the plasma generator is configured and arranged to create aplasma in a plasma generation zone in the second chamber, which plasma generation zone is downstream of the gas inlet and upstream of said membrane; i.e. downstream respectively upstream with respect to the gas flow. Preferably, in operation, plasma-activated species are transported from the plasma generation zone to the membrane, in particular to the permeate side of the membrane, before reaching the outlet.

[0044] Operation of the reactor involves oxygen transport through the membranefrom the first chamber to the second chamber; accordingly the first chamber is at a retentate side (also called feed side) of the membrane and the second chamber is at a permeate side of the membrane.

[0045] The membrane is in an embodiment symmetrical, and optionally theretentate side (feed side) and permeate side of the membrane do not differ in composition or structure if the reactor is not operated. In an embodiment with a symmetrical MIEC membrane, the membrane is e.g. a single layer of MIEC material having a thickness of e.g. 0.20 to 2.0 mm, such as 0.4 to 1.5 mm, e.g. about 1.0 mm.

[0046] In a further embodiment, the MIEC membrane is a multilayer membrane,and comprises for instance a plurality of stacked layers, these layers being non- identical. Multilayer meaning at least two, and preferably at most 6 layers, more preferably at most 4 layers. For instance, two layers are stacked. For instance, the MIEC membrane comprises a dense membrane stacked on a porous membrane; with the dense layer at the permeate side to provide for oxygen ions or radicals at the dense layer which may react with activated nitrogen species.

[0047] The dense and porous layer can be defined relative to each other, i.e. themultilayer MIEC membrane has a retentate side layer that has a greater porosity than the permeate side layer.

[0048] In an embodiment, the multilayer membrane is asymmetric in having twoexposed surfaces (and edges), the surfaces being different from each other in one or more properties, such as porosity. Preferably, the chemical composition of the layers is the same, e.g. when a multi-layer membrane is used, the layers differing e.g. in porosity. This provides the advantage of the layers having the same chemical composition and thermal coefficient of expansion minimizing the risk of separation of the layers upon heating / cooling, and the advantage that bonding between the layers is simplified.

[0049] Porous MIEC layers can be prepared from a slurry containing a additionalparticles that are dissolved afterwards. A reference for a suitable preparation method for the MIEC membrane with a porous layer and a dense layer is: W. He et al., Journal of Membrane Science 452 (2014) 294–299.The MIEC membrane has conductivity for ions, in particular O2–ions, and for electrons. The MIEC membrane is e.g. single phase or a dual-phase. In a dual-phase MIEC membrane, a first material phase transports ions and a second material phase transports electrons in operation.

[0050] The membrane and the chemical reactor are preferably configured fortransport of ions, in particular O2–ions, from the first chamber to the second chamber.

[0051] The shape of the MIEC membrane is not particularly limited and is e.g. asheet, or tubular, or the membrane is e.g. a hollow fiber membrane. The membrane is for instance a supported or unsupported thin film, wherein the film is e.g. a sheet or tubular.

[0052] The term ‘membrane’ is used in this application to refer to a separatorbetween the first and second chamber that is selectively permeable to mass transport of chemical species, in particular a reactant species in the disclosed reactor and process, and for the specified MIEC membrane, to oxygen transport. The membrane provides a selective barrier between the first and second chamber.

[0053] In operation, the O2 partial pressure (proportion of O2 multiplied by thesystem pressure) is typically higher at the retentate side (feed side) of the membrane than at the permeate side of the membrane, thereby supplying a driving force for oxygen permeation through the MIEC membrane.

[0054] The membrane for example comprises a solid oxide, for instance a metaloxide. The membrane comprises for example a perovskite material; and for instance substantially consists of, or consists of, a solid oxide, in particular a metal oxide, e.g. a perovskite material. Fluorites, brownmillerite, and pyrochlores are further example materials that can be used for the membrane. In particular the oxygen transporting mixed ionic-electronic conducting material comprises preferably a metal oxide, e.g. a perovskite material, or e.g. flourite, brownmillerite, or pyrochlore material.

[0055] Example MIEC materials (i.e. oxygen transporting mixed ionic-electronicconducting material) for use in the membrane include, without limitation and by way of non-exhaustive list:d. YSZ (Yttria-Stabilized Zirconia) composites: Example: YSZ0.6 – (In90Pr10)0.4 e. [(Bi2O3)0.74(SrO)0.26]0.6-Ag0.4 f. [(Bi2O3)0.75(Er2O3)0.25]0.6-Ag0.4 g. [(Bi2O3)0.75(CaO)0.25]0.6-Ag0.4h. (Bi1.5Y0.3Sm0.2O3 )0.6-Ag0.4 i. CPO Ce0.9Pr0.1O2-δ j. PSFO Pr0.6Sr0.4Fe2O3-δ k. LSFO La0.9Sr0.1FeO3-δ l. Samaria doped ceria (SDC) Sm0.2Ce0.8O2-δ m. YCCC Y0.8Ca0.2Cr0.8Co0.2O3 n. BYS Bi1.5Y0.3Sm0.2O3 o. Ce0.9Gd0.1O2-δ p. (Pr0.9La0.1)2(Ni0.74Cu0.21Ga0.05)O4-δ q. Ba0.5Sr0.5Co0.8Fe0.1Ni0.1O3-δ r. Ba0.9Co0.7Fe0.2Nb0.1O3-δ

[0056] In an embodiment, the membrane additionally comprises a catalyst. Thecatalyst is, for instance, applied on the membrane surface exposed to the first chamber, on the membrane surface exposed to the second chamber, or on both membrane surfaces.

[0057] The catalyst is for instance Pt, Pd or Ir, preferably Pt. The catalyst is forinstance applied as a coating on a surface of the membrane. The catalyst, or metallic materials such as Pt, Pd, or Ir, can also be distributed through the membrane, in some optional embodiments.

[0058] Without wishing to be bound by way of theory, such catalysts (or metals)may enhance the flux of oxygen species from the first chamber to the permeate side membrane surface and / or to the second chamber, for instance by enhancing O2 dissociation.

[0059] The reactor for example comprises no electrodes connected to themembrane. This allows for an advantageous simple construction.

[0060] The invention also pertains to a plant (reactor system) comprising thedescribed chemical reactor (in turn comprising the MIEC membrane and the plasma generator), and downstream of that chemical reactor, one or more downstream processing units, for processing of a gaseous stream withdrawn from the second chamber. In particular, in the one or more downstream processing units, an intermediate product formed in the second chamber is e.g. further converted (reacted) into a final product in one or more reactions.

[0061] The plant is configure for a supplying first and second reactant to the firstrespectively second chamber, and transport of the first reactant species through the membrane in the direction from the first to the second chamber, and a reactionof the reactant species in the second chamber or on the membrane surface exposed to the second chamber.

[0062] The term plant, as used herein, does not imply a certain minimum size ofthe equipment, or a certain minimum capacity, and the plant can also be referred to as a chemical production system or chemical production unit or a reactor system.

[0063] The plant (reactor system) preferably comprises an inlet and / or supply linefor introducing an oxygen-containing stream, such as an air stream, into the process gas stream that is withdrawn from the second chamber. This can be used to convert NO in the process gas stream into NO2 in the gas phase. This is especially useful in case of a nitric acid plant.

[0064] The plant (reactor system) for instance comprises, as a downstreamprocessing unit, an absorption unit arranged downstream of the gas outlet of the second chamber. The absorption unit is configured for contacting the gas stream from the second chamber with an absorbent, for example configured for counter- current contact between an absorption liquid, e.g. an aqueous liquid stream, and the gas stream from the second chamber which comprises NO and NO2 with preferably the formation of an aqueous nitric acid stream in the absorption unit. Non-condensed gas from the absorption unit, e.g. tail gas from the absorption column, typically contains N2 and O2 and is e.g. supplied to an ASU comprised in the plant.

[0065] For example, the absorption unit is an absorption tower for absorbing NO2into H2O with formation of nitric acid, as that reaction is typically described in the art (see, e.g., Ullmann’s Encyclopedia, chapter Nitric Acid, 2012, page 179, reaction (3), 3 NO2 + H2O → 2 HNO3 + NO). The plant is therefore, preferably, a nitric acid production plant.

[0066] An example plant according to the invention is, therefore, as illustrated inFig. 12, a nitric acid production plant (100) comprising the chemical reactor (101) that comprises the first chamber (1), the second chamber (2), the membrane (3), and the plasma generator (4). The second chamber has an outlet for a gas stream (5) which outlet is positioned to withdraw, from the second chamber, the gaseous product formed at or near the permeate surface of the membrane that is exposed to the second chamber. The second chamber comprises an inlet for a second reactant, e.g. N2 (6). The first chamber comprises an inlet for a firstreactant, e.g. O2 (7) and an outlet for a retentate stream (8). This retentate stream is, e.g., added to the as stream (5) from the second chamber.

[0067] The plant also comprises an absorption column (9) having an inlet for anaqueous absorption liquid (10), a tail gas outlet (11) at the top, and a nitric acid outlet (12) at the bottom. The tail gas outlet is connected to e.g. an inlet of an ASU of the plant. The plant also comprises a supply for O2-containing gas (22) that is mixed with the gas stream from the second chamber (2) upstream of the absorption column (9) and optionally the plant also comprises one or more coolers (not shown) for cooling gas (5) in the gas flow line from the second chamber to the absorption unit (absorption column).

[0068] Continuing the general discussion, the absorption unit for instance alsocomprises cooling elements, e.g. for indirect heat exchange with a cooling fluid. The absorption unit comprises e.g. plates, trays and / or or a packed bed.

[0069] The absorption unit comprises e.g. a gas inlet for said gas stream from thesecond chamber, optionally through a cooler, an inlet for absorbent, e.g. absorption liquid, a first outlet for gas, and a separate second outlet. The absorption unit is e.g. an absorption column, with a top gas outlet and a bottom liquid outlet, and the gas inlet in a lower part.

[0070] In an example embodiment, the absorption unit is an absorption columnthat has a gas inlet at a bottom part, a tail gas outlet at an upper part, a nitric acid outlet at the bottom part, and a process water inlet at the upper part, and is for instance provided with vertically spaced horizontal plates (trays). For example, the absorption column also comprises cooling elements. However, other types of absorption units are also possible. A non-limiting example absorption column is shown in Fig. 12.

[0071] Optionally, one or more coolers are provided for cooling the gas flow fromthe second compartment, for example upstream of the absorption unit. These coolers are for instance heat exchangers for heat exchange between the gas stream and cooling fluid, e.g. boiler feed water.

[0072] As said, suitably, an oxygen-combining gas stream is added to the gasstream from the second chamber upstream of the absorption unit, in particular to oxidize NO formed in the second chamber into NO2. The NO2 can be absorbed inthe (aqueous) absorption liquid in the absorption unit (in practice through N2O4, see Ullmann’s Nitric Acid, page 185, rection (20).

[0073] Preferably the plant (reactor system) comprises an air separation unit(ASU). The ASU has a first outlet for an oxygen-enriched stream and a second outlet for a nitrogen-rich stream. The second outlet is connected to the second chamber. The ASU typically has an inlet for air.

[0074] For instance, the oxygen enriched stream comprises more than 22 mol.% O2,e.g. more than at least 25 mol.% oxygen. The nitrogen-rich stream comprises e.g. at least 90 vol.% N2, or at least 99 vol.% N2.

[0075] As an example illustrated in Fig. 12, the plant comprises the ASU (13)having a second outlet for a nitrogen-rich stream (6) connected to the second chamber. Optionally, a first part of the nitrogen-rich stream may be supplied to the second chamber and a second part (6a) is supplied e.g. to an ammonia synthesis unit. The ASU (13) also has an air supply line (14) and receives optionally tail gas (11) (not shown). The outlet of the ASU for the oxygen-enriched stream (7) is connected for example to the first chamber.

[0076] The first chamber has a gas outlet. Optionally, the gas outlet of the firstchamber is connected to an inlet of the ASU. In an embodiment, the first outlet of the ASU for an oxygen enriched stream is connected to first chamber, in particular to the inlet of the first chamber or to an additional inlet of the first chamber. Preferably an air supply line is connected to the ASU and / or to the first chamber.

[0077] In a further, preferred, embodiment, the plant comprises a waterelectrolysis unit having an inlet for water, and a first outlet for an O2 stream that is connected to an inlet of the first chamber. Preferably, the first chamber only receives the O2 stream from the water electrolysis unit. The high purity of the oxygen stream from water electrolysis may provide the advantage of a relatively smaller MIEC membrane surface being necessary (for a given NOx production rate). The water electrolysis unit has a second outlet for H2 that is preferably supplied to an ammonia synthesis loop where it is reacted with nitrogen, e.g. the nitrogen rich stream from the ASU.

[0078] The resulting ammonia may in part or entirely be used in a neutralizationunit for neutralizing nitric acid produced from the NOx that is produced in the chemical reactor. Preferably, the plant also comprises the neutralization unit, andthe plant is for the production of ammonium nitrate. In the neutralization unit the HNO3 product and ammonia, preferably from an ammonia synthesis unit, are combined and reacted to form ammonium nitrate.

[0079] For example, as shown in Fig. 12, the plant comprises the neutralizationunit (15) that receives the nitric acid (12) and an ammonia stream (16) to form ammonium nitrate (17). The neutralization unit is an independent preference to the ASU (13).

[0080] Also provided is an ammonium nitrate plant comprising the nitric acid plant(which comprises the chemical reactor with the first and second chamber), the neutralization unit, and an ammonia synthesis unit. The plant accordingly comprises the chemical reactor, the absorption unit downstream of the second chamber, and the neutralization unit receiving nitric acid from the absorption unit. The plant further comprises a flow line for ammonia from the ammonia synthesis unit to the neutralization unit, where ammonium nitrate is produced. The plant also comprises a water electrolysis unit having an outlet for H2 connected to an inlet of the ammonia synthesis unit, and the water electrolysis unit also has an outlet for O2 connected to, e.g., the first chamber of the chemical reactor,. Alternatively, the O2 outlet of the water electrolysis unit may be connected to another unit in the plant, e.g. to the absorption unit. The O2 outlet of the water electrolysis unit may be connected to two or more units in the plant, e.g. to the first chamber of the chemical reactor and to the absorption unit.

[0081] The plant also comprises an air separation unit (ASU), having an outlet foran N2 gas stream connected to an inlet of the ammonia synthesis unit and an outlet for an oxygen-enriched air stream connected to, typically, the reactor system, e.g., the first chamber of the chemical reactor and / or e.g. to the gas flow line from the second chamber to the absorption unit, or the absorption unit. Advantageously, this plant does not rely on combustion of NH3 to produce the nitric acid that is in turn used to make ammonium nitrate, AN.

[0082] As illustrated in the example plant of Fig. 12, the ammonia (16) is producedin an ammonia synthesis unit (18) that receives an N2-comprising feed, for example from the ASU as a part (6a) of the nitrogen-rich stream (6) and receives a H2 feed stream (19), for example from a water electrolysis unit (20) that also has an outlet for an O2 stream (21) as well as an inlet for water (23).

[0083] In a preferred embodiment of the ammonium nitrate plant, the waterelectrolysis unit and ASU are used in combination.

[0084] In a preferred embodiment schematically shown in Fig. 13, the oxygenstream (21) from the water electrolysis unit (20) is supplied to the inlet (7) of the first chamber (1). Optionally, the oxygen-enriched stream (22a) from the ASU (13) is introduced, as (a part of) the oxygen-comprising stream (22), in the gas (5) from the second chamber upstream of the absorption column (9), to cause NO oxidation in the gas (5) from the second chamber.

[0085] The invention also pertains to an ammonium nitrate production processcarried out in said plant, comprising producing NOx in the chemical reactor, converting the NOx into nitric acid in the absorption unit, reacting the nitric acid with ammonia in the neutralization unit to form AN; and further comprises producing the ammonia feed for the neutralization unit in the ammonia synthesis unit, using H2 from the water electrolysis unit and N2 from the ASU.

[0086] The ammonia synthesis unit comprises, e.g. a synthesis loop comprising areactor and a condenser and a recycle compressor, as well as a compressor for compressing the feed gas mixture introduced into the synthesis loop.

[0087] Preferences for the components of the chemical reactor also apply to theplant comprising the chemical reactor. The inventive plants are preferably suitable for the corresponding inventive process, for example, the nitric acid plant is preferably suitable for the inventive nitric acid production process, the inventive ammonium nitrate plant is preferably suitable for the inventive ammonium nitrate production process. The inventive processes are preferably carried out in the (corresponding) inventive plant.

[0088] The invention also pertains to a process carried out in a chemical reactoraccording to the invention, comprising supplying a gaseous first reactant to the first chamber, supplying a gaseous second reactant to the second chamber, plasma- activating the second reactant in the second chamber using a plasma generated by said plasma generator, and causing transport of species of the first reactant from the first chamber through the membrane to the second chamber; and reacting the membrane-transported species, whether free or in membrane-bound form, with the plasma-activated species. Thereby a product is formed in the second chamber, in particular a gaseous product. The process involves withdrawing the product fromthe gas outlet of the second chamber. The process may involve reacting the product further in a downstream processing unit.

[0089] The invention also provides a process of producing NOx (NO and / or NO2)carried out in a reactor or in a reactor system according to the invention. The process is typically a continuous process.

[0090] The process comprises: transport of oxygen species through the membranefrom a gas phase in the first chamber to the second chamber; generating a nitrogen-comprising plasma with said plasma generator in said second chamber; and withdrawing a gas stream comprising NOx through said outlet of said second chamber. Preferably, the process is an embodiment of said inventive process carried out in the inventive chemical reactor. The nitrogen-comprising plasma is a plasma comprising nitrogen (nitrogen species) and is obtained from a gas comprising N2, such as, e.g. air, nitrogen-enriched air, or a mixture of N2 and another gas, or from N2 gas.

[0091] Preferably, the plasma is a non-thermal plasma.

[0092] A non-thermal plasma indicates a plasma which is not in thermodynamicequilibrium, because the electron temperature is much hotter than the temperature of heavy species (ions and electrically neutral atoms and molecules).

[0093] In the process, preferably a gas stream supplied to the first chamber and / orthe first gas has a higher partial pressure of O2 than a gas stream supplied to the second chamber and / or the second gas.

[0094] More preferably, the total gas stream supplied to the first chamber has ahigher partial pressure of O2 than the total gas stream supplied to the second chamber. The difference in partial pressure can be provided by difference in O2 concentration, a difference in absolute pressure, or a combination thereof. Preferably, the difference in O2 partial pressure is at least 0.10 bar or, preferably at least 0.20 bar. The difference in partial pressure provides a driving force for transport of oxygen through the membrane.

[0095] Preferably the gas stream supplied to the second chamber and to the plasmagenerating unit comprises N2, preferably comprises at least 10 vol.% N2, or more preferably, at least 30 vol.% N2, or at least 50 vol.% N2, or at least 70 vol.% N2, or, suitably, at least 80 vol.% N2, or at least 90 vol.% N2, or at least 99 vol.% N2; and / orpreferably less than 20 vol.% O2, or more preferably less than 10 vol.% O2, or even more preferably less than 1.0 vol.% O2, or less than 0.1 vol.% O2. Optionally, the gas stream comprises at least 10 vol.% of a third gaseous component, other than N2 and O2, that is e.g. inert with respect to the plasma.

[0096] These preferred compositions apply in particular to the total gas receivedby the plasma generating unit; in case of a gas flow through the plasma generating unit at the upstream part of the plasma generating unit with respect to said gas flow. Hence, the compositions relate to the total gas supplied to the plasma generating unit by one or more inlets.

[0097] Preferably, the gas stream in which the plasma is formed, contains at least70 vol.% N2 or at least 80 vol.% N2 or at least 90 vol.% N2; and preferably less than 10 vol.% O2 or less than 1.0 vol.% O2 or less than 0.1 vol.% O2. By generating the plasma in nitrogen-rich gas that is also low in oxygen, the plasma energy is advantageously used efficiently and selectively for generating plasma-activated nitrogen species.

[0098] Optionally, the second gas is obtained in part or entirely as nitrogen-richgas stream from an air separation unit (ASU) or nitrogen generation unit (NGU).

[0099] It is noted that the process typically involves withdrawal of gas from thesecond chamber.

[0100] Preferably the gas stream supplied to the first chamber comprises at least 5vol.% O2 or at least 10 vol.% O2, and preferably at least 20 vol.% O2, and is for example air or oxygen-enriched air. Oxygen-enriched air is preferred, with e.g. at least 25 vol.% O2 or at least 30 vol% O2, or at least 50 vol% O2; higher concentrations are also possible. High oxygen concentrations of the gas in the first chamber promote oxygen transport through the MIEC membrane.

[0101] Herein, the mentioned compositions preferably refer to the total feedstocksupplied to the first chamber, and to the compositions of the gas in the first chamber.

[0102] Preferably, the transport of oxygen species (species comprising O atoms)through the membrane is carried out without electrolysis of water on the retentate side surface of the membrane. Preferably, the membrane is not provided with ananode and cathode. It is observed that YSZ (yttria stabilized zirconia) is such is a pure ionic conductor and is not a MIEC membrane.

[0103] Preferably, the gas in the first chamber comprises at least 30 vol.% O2, or atleast 50 vol.% O2, or at least 80 vol.% O2, or at least 90 vol.%, or at least 95 vol.% O2, or at least 99 vol.% O2, with higher concentrations O2 being preferred as permitting the use of a relatively smaller MIEC membrane.

[0104] The balance of the gas in the first chamber is e.g. an inert gas (inert at theretentate side), such as N2.

[0105] The source of the gas in the first chamber is e.g. at least in part, e.g. for atleast 50 mol.%, or e.g. entirely, an oxygen stream from a water electrolysis unit. Such gas streams typically contain at least 95 mol.% O2 or even at least 99 mol.% O2.

[0106] The absolute pressure of the gas in the first chamber is e.g. at least 1.0 bar,e.g.1.0 – 5.0 bar, preferably with said higher concentrations of O2.

[0107] The gas stream withdrawn from the first chamber is in an exampleembodiment oxygen-depleted air containing more than 80 vol.% N2. Preferably this gas stream is supplied directly or indirectly from the first chamber to the second chamber, in particular to the gas inlet of the second chamber upstream of the zone where plasma is generated in operation, e.g. the zone of the second chamber in vicinity to the plasma generator. In this embodiment, for example air is supplied to the first chamber, or for example air is supplied to an ASU (air separation unit) and oxygen-enriched air is supplied from the ASU to the first chamber. A nitrogen rich stream from the ASU is for instance supplied to the second chamber.

[0108] In an embodiment wherein a gas stream comprising N2 and O2 is supplied tothe first chamber, the gas stream from the first chamber is preferably supplied to an air separation unit (ASU) which has an outlet for a nitrogen-enriched stream connected to the second chamber. The oxygen-enriched stream from the ASU is supplied preferably to the first chamber. Air is supplied preferably to the ASU, or to the first chamber. The advantages of this embodiment, with gas from the first chamber supplied through the ASU to the second chamber, are indicated in Example 2. The nitrogen-rich (or enriched) stream from the ASU has a higher concentration (vol.%) of N2 than the oxygen-rich (or enriched) stream from the ASU.

[0109] Preferably, the reactor system is suitable for this process and comprises agas flow connection from a gas outlet of the first chamber directly or indirectly to a gas inlet of the second chamber. Preferably, the reactor system comprises an ASU. The ASU has a first outlet for an oxygen-rich stream and a second outlet for a nitrogen-rich stream, wherein the second outlet is connected to the second chamber. Preferably, the gas outlet of the first chamber is connected to an inlet of the ASU. Preferably a first outlet of the ASU for an oxygen-rich stream is connected to an inlet of the first chamber. Preferably, an air supply line is connected to the ASU and / or first chamber. The air supply line optionally comprises a dust filter to remove dust from the air. Preferably, the process is carried out in this preferred reactor system.

[0110] In the process, an activated nitrogen species formed in the plasma isallowed to react in the second chamber and / or on the surface of the membrane exposed to the second chamber with oxygen species that are derived from O2 provided in the first chamber to form a product, in particular NOx, which is withdrawn with a gaseous product stream from the second chamber.

[0111] Preferably, N2 is activated by the plasma to allow reaction with oxygenspecies transported through the membrane.

[0112] In a preferred embodiment, the MIEC membrane is operated with atemperature in the range of at least 300ºC, or at least 400ºC, or at least 500ºC and / or up to 1100 °C. A temperature above 300ºC, such as above 500ºC, can be used to increase oxygen transport through the membrane. A combination of the heating by the plasma and a pre-heating of the feed to the first chamber is e.g. used.

[0113] Preferably, the process involves cooling the gas stream from the secondchamber, for instance by indirect heat exchange with a cooling fluid, such as boiler feed water.

[0114] Preferably, the method is for nitric acid production and comprises reactingthe NOx withdrawn from the second chamber with an absorbent (e.g. absorption liquid), that preferably comprises H2O, and optionally with additional O2, to form nitric acid.

[0115] Preferably, the process involves contacting the gas stream from the secondchamber, optionally after cooling, with a liquid, more preferably with an absorption liquid; preferably with counter-current contact of the gas and the liquid. Thesecond gas is for instance contacted with an aqueous liquid to form nitric acid. The gas stream may also be contacted with a liquid to absorb NOx from the gas into the liquid, after which the NOx species, in particular NO2 can be reacted with H2O to form nitric acid.

[0116] Preferably, the nitric acid production process comprises adding an oxygen-containing gas stream, e.g. from the first chamber, to the gas stream withdrawn from the second chamber, preferably the gases are mixed upstream of the absorption unit. Optionally, an oxygen-containing gas stream is also supplied to the absorption unit, e.g. to the absorption column.

[0117] Also provided is an ammonium nitrate production process, comprising:producing nitric acid with the inventive nitric acid process, and neutralizing the nitric acid with ammonia in a neutralization unit. Preferably the process is carried out in an inventive ammonium nitrate plant. Preferably the process further comprises, as upstream steps, producing the NH3 feed for the neutralization unit in the ammonia synthesis unit and producing the H2 feed for the ammonia synthesis unit in the water electrolysis unit. The preferably used water electrolysis unit also gives an O2 stream. Preferably the process comprises suppling at least a part of the O2 stream from the water electrolysis unit to the first chamber. Examples

[0118] The invention will now be further illustrated by the following non-limitingexamples. The examples do not limit the invention and does not limit the claims. Example 1

[0119] The experimental set-up for this reactor is schematically depicted in Fig. 1.

[0120] Air at slightly above 1 bar absolute was supplied from the compartment (A)of the reactor (as in Fig.1) to the MIEC membrane provided as hollow fiber membrane, to the inside of the fibers (B). The MIEC material was BSCF (Ba0.5Sr0.5Co0.8Fe0.2O3-d). A dual layer MIEC membrane was used with a porous retentate side layer and a dense permeate side layer.

[0121] Nitrogen-enriched air was removed from the left compartment. The MIECmembrane was operated at 600ºC. A heater (C) was used.

[0122] Pure N2 gas was supplied to the quartz reactor (right compartment) at5 mbar and was activated using a plasma generated with a radio-frequency (RF) coil (D). The skilled person understands that also higher pressure plasmas can be used. The spacing between the membrane and the RF coil is approximately 20 cm in this example. The projection of the RF coil over the diameter of the tube (perpendicular to the horizontal gas flow) defines the plasma formation zone in the tube.

[0123] Fig. 2 shows the dependence of the oxygen amount (nmol / s) in the vacuumcompartment (permeate side) of the plasma membrane reactor on the supplied air flow (µmol / s) (air at 1 atm) using a single BSCF membrane tube with two different spacings between the membrane and the coil. In the example with an extension, the spacing between the membrane and the RF coil was decreased by 6 cm by installing a spacer of 6 cm at the membrane inlet. Oxygen was successfully transported across the membrane and air separation was achieved.

[0124] Fig. 3 shows the O2 level on the permeate side (nmol / s) as a function of theair flow (µmol / s) (1 atm, 600ºC, without extension) using 3 hollow fiber BSCF membranes in parallel.

[0125] Fig. 4 shows the oxygen concentration (ppmv) on the permeate side as afunction of the air flow rate (ml / min at STP), for a pristine BSCF membrane and for a BSCF membrane coated with Pt on the permeate side. STP conditions, as used herein, are 0ºC and 1 atm.

[0126] Fig. 5 shows NOx production (ppmv) by reaction of plasma activated N2 withoxygen species transported through the MIEC membrane as a function of plasma power for a single BSCF hollow fiber membrane; with air flow 50 cm³STP / min and N2 flow 50 cm³ STP / min with 5 mbar pressure on the permeate side.

[0127] Fig. 6 shows NO synthesis (nmol / s) as a function of plasma power (W) andN2 flow rate (from left to right, A-D, 100, 50, 30, 10 cm³ STP / min) with a single BSCF hollow fiber membrane. Here we see and advantage of the membrane where the selectivity towards NO, or alternatively the NO / N2O ratio, can be influenced positively.

[0128] Fig. 7 shows NO concentration (ppmv) as a function of plasma power (W)for, from left to right, CT, CT-E, UCT, UCT-E, and MUT (at each plasma power level). Herein, CT is covered membrane tube: the BSCF hollow fiber membranetube was partially covered by an alumina tube such that only 6 cm of non-covered membrane length was exposed to the plasma. UCT is the tube without such cover. E indicates extension: a spacer of 6 cm was installed at the membrane inlet to reduce the spacing between the plasma and the membrane by 6 cm, from about 20 cm to about 14 cm. MUT indicates three tubes in parallel (only without extension). Example 2

[0129] Three process schemes (configurations) were modelled, as indicated below.Fig. 8 shows Scheme 1, Fig. 9 shows Scheme 2, Fig. 10 shows Scheme 3.

[0130] It can be concluded that Scheme 2 is advantageous in at least one respectover Scheme 1, as the required ASU will be smaller (compare stream 100). Moreover, Scheme 3 is advantageous in at least one respect over Scheme 2, as the purge - and therefore energy losses - will be smaller (compare stream 300). Configuration 1:

[0131] As shown in Fig. 8, gas from the first chamber is vented. Results are shownin Table 1. In Fig. 8, 1 is the first chamber, 2 is the second chamber, separated by the membrane, and ASU is the air separation unit. In practice, the plasma source can be arranged to define a plasma formation zone in the second chamber. Table 1 COMPONENT: O2 N2 N2* NO NO2 SUMSTREAM: kmol / h100 21.0 79.0 0.0 0.0 0.0 100.0110 20.9 65.1 0.0 0.0 0.0 86.0120 0.1 13.9 0.0 0.0 0.0 14.0130 0.1 7.0 7.0 0.0 0.0 14.0210 20.3 65.1 0.0 0.0 0.0 85.4230 0.1 13.6 0.0 0.3 0.3 14.4O2 FLUX 0.525 0.0 0.0 0.0 0.0 0.5Configuration 2:

[0132] As shown in Fig. 9, gas from the first chamber is supplied to the ASU, andthe oxygen-rich gas from the ASU is combined with air and supplied to the first chamber. Results are shown in Table 2 (flow rates in kmol / h). Stream 100 issmaller than in Configuration 1, so that the ASU can be smaller in Configuration 2. Table 2 O2 N2 N2* NO NO2 SUMSTREAM kmol / h090 5.9 22.3 0.0 0.0 0.0 28.2100 21.0 33.4 0.0 0.0 0.0 54.4110 20.9 19.5 0.0 0.0 0.0 40.4115 26.8 41.7 0.0 0.0 0.0 68.5120 0.1 13.9 0.0 0.0 0.0 14.0130 0.1 7.0 7.0 0.0 0.0 14.0210 26.3 41.7 0.0 0.0 0.0 68.0230 0.1 13.6 0.0 0.3 0.3 14.4300 5.3 8.3 0.0 0.0 0.0 13.6O20.525 0.0 0.0 0.0 0.0 0.5FLUX Configuration 3:

[0133] As shown in Fig. 10, gas from the first chamber is supplied to the ASU,which also receives air, and the oxygen-rich gas from the ASU is supplied to the first chamber. Results are shown in Table 3. Scheme 3 is advantageous in at least one respect over Scheme 2, as the purge - and therefore energy losses - will be smaller (compare stream 300). Table 3 COMPONENT O2 N2 N2* NO NO2 SUMSTREAM: kmol / h090 4.7 17.8 0.0 0.0 0.0 22.5100 21.0 33.4 0.0 0.0 0.0 54.4110 20.9 19.5 0.0 0.0 0.0 40.4120 0.1 13.9 0.0 0.0 0.0 14.0130 0.1 7.0 7.0 0.0 0.0 14.0210 20.3 19.5 0.0 0.0 0.0 39.8220 16.3 15.6 0.0 0.0 0.0 31.9230 0.1 13.6 0.0 0.3 0.3 14.4300 4.1 3.9 0.0 0.0 0.0 8.0O2 FLUX 0.525 0.0 0.0 0.0 0.0 0.5Example 3

[0134] An illustrative example process scheme is shown in Fig. 11. In this scheme,a gas stream comprising N2 and O2 is supplied to the first chamber, which is separated from the second chamber by the membrane. N2-containing gas is supplied to a zone where plasma is generated, shown schematically as a separate block. The gas stream from the plasma, comprising activated N species, is contacted with the permeate side of the membrane in the second chamber. Gas is withdrawn from the second chamber, which gas contains NOx, N2, and O2. Preferably, the gas is cooled and supplied to the inlet of an absorption unit, shown as a column with trays by way of example, where it is absorbed in an aqueous stream to form aqueous nitric acid withdrawn from the bottom. Tail gas is withdrawn from the absorption unit. Example 4

[0135] In a configuration 4, the first chamber (retentate side of the MIECmembrane) receives an oxygen-enriched gas stream from an ASU with 10.67 kmol / hr N2 and 5.62 kmol / hr O2. The pressure in the first chamber was slightly above 1 bar absolute and the temperature was 900ºC. The pressure in the second chamber (permeate side of the membrane) was also slightly above 1 bar absolute.

[0136] The first chamber has an outlet for a gas stream (retentate) that isoptionally further used in the process. Example 5

[0137] In configuration 5, the first chamber received only a stream with 0.39kmol / hr O2, modelled as pure O2. This stream is produced by water electrolysis. The configuration was otherwise the same as in configuration 4.

[0138] Simulations show that for equal O2 transport through the MIEC membrane(0.31 kmol / hr), the MIEC membrane surface area can be significantly smaller, up to about 50% smaller in configuration 5 than in configuration 4.

Claims

Claims 1. A plant comprising a chemical reactor (101) comprising a first chamber (1) and a second chamber (2), a membrane (3) comprising an oxygen transporting mixed ionic-electronic conducting material and separating the first and second chamber, an inlet (7) for providing a first gas in the first chamber, an inlet (6) for providing a second gas in the second chamber, an outlet (5) for a gaseous stream from the second chamber, and a plasma generator (4) for forming a plasma in the second chamber, and a downstream processing unit arranged downstream of said outlet of the second chamber for processing said gaseous stream from said second chamber.

2. A plant according to claim 1, wherein in the chemical reactor, the oxygen transporting mixed ionic-electronic conducting material comprises a metal oxide; wherein the oxygen transporting mixed ionic-electronic conducting material preferably comprises a perovskite material.

3. A plant according to claim 2, wherein in the chemical reactor, the mixed ionic-electronic conducting material of the membrane comprises BSCF (Ba0.5Sr0.5Co0.8Fe0.2O3-δ).

4. A plant according to any of the preceding claims, wherein in the chemical reactor, the plasma generator comprises one or more selected from the group consisting of a laser-induced plasma generator, a arc plasma generator, a radio frequency plasma generator, a microwave plasma generator, a dielectric barrier discharge plasma generator, and a glow discharge plasma generator.

5. A plant according to any of the preceding claims, wherein in the chemical reactor, the plasma generator is provided for forming a plasma in said second chamber in a zone of said second chamber downstream of said gas inlet and upstream of said membrane; preferably wherein in the chemical reactor, said membrane is a sheet, tubular, or a hollow fiber membrane.

6. A plant according to any of the preceding claims, wherein in the chemical reactor, the membrane is a multilayer MIEC membrane having a porous retentateside layer exposed to the first chamber and a dense permeate side layer exposed to the second chamber.

7. The plant according to any of the preceding claims, wherein the plant further comprises an air separation unit (ASU) (13), the ASU having a first outlet for an oxygen-enriched stream (7) and a second outlet for a nitrogen-rich stream (6), wherein the second outlet of the ASU is connected to the second chamber, wherein the first chamber has a gas outlet, and the gas outlet of the first chamber is connected to an inlet of the ASU or to the gas flow line for gas (5) from the second chamber to the absorption unit (9), and wherein the first outlet of the ASU for an oxygen-enriched stream is connected to the first chamber, and wherein an air supply line is connected to the ASU and / or first chamber.

8. The plant according to any of the preceding claims, wherein the plant comprises a water electrolysis unit (20) having an outlet for an oxygen stream (21) connected to an inlet of the first chamber; preferably wherein the first chamber is connected to receive only said oxygen stream from the water electrolysis unit.

9. A plant according to any of claims 1-8, which is a nitric acid plant, wherein the downstream processing unit is an absorption unit (9) arranged downstream of said outlet of the second chamber for contacting said gaseous stream from said second chamber with an absorption liquid (10) to form nitric acid.

10. An ammonium nitrate production plant, comprising the nitric acid plant according to claim 9, and further comprising: - an ammonia synthesis unit (18) connected to receive H2 (19) from the water electrolysis unit (20), and - a neutralization unit (15) connected to receive ammonia (16) from the ammonia synthesis unit (18) and nitric acid (12) from the absorption unit (9) and having an outlet (17) for a stream comprising ammonium nitrate.

11. A process carried out in a chemical reactor comprising a first and a second chamber, a membrane comprising an oxygen transporting mixed ionic-electronic conducting material and separating the first and second chamber, an inlet for providing a first gas in the first chamber, an inlet for providing a second gas in thesecond chamber, an outlet for a gaseous product stream from the second chamber, and a plasma generator for forming a plasma in the second chamber, the process comprising supplying a gaseous first reactant to the first chamber, supplying a gaseous second reactant to the second chamber, activating the second reactant in the second chamber by a plasma generated by said plasma generator, and causing transport of species of the first reactant from the first chamber through the membrane to the second chamber; preferably wherein the chemical reactor has the features defined in any of claims 2-6.

12. A process of producing NOx carried out in a chemical reactor comprising a first and a second chamber, a membrane comprising an oxygen transporting mixed ionic-electronic conducting material and separating the first and second chamber, an inlet for providing a first gas in the first chamber, an inlet for providing a second gas in the second chamber, an outlet for a gaseous product stream from the second chamber, and a plasma generator for forming a plasma in the second chamber, the process comprising: - transport of oxygen species through the membrane from a gas phase in the first chamber to the second chamber; - supplying N2 to the inlet for the second gas in the second chamber; and - withdrawing a gas stream comprising NOx through said outlet of said second chamber; wherein preferably the chemical reactor has the features defined in any of claims 2-6.

13. The process according to claim 12, wherein a gas stream supplied to the first chamber has a higher partial pressure of O2 than a gas stream supplied to the second chamber.

14. The process according to claim 12-13, wherein the membrane is a BSCF (Ba0.5Sr0.5Co0.8Fe0.2O3-δ) membrane.

15. The process according to any of claims 12-14, wherein the plasma is a non- thermal plasma.

16. The process according to any of claims 12-15, comprising supplying a gas stream comprising at least 20 vol.% O2 to the first chamber and supplying a gasstream comprising at least 50 vol.% N2 and less than 1.0 vol.% O2 to the second chamber.

17. The process according to any of claims 12-16, comprising supplying a gas stream comprising at least 99 vol.% O2 to the first chamber.

18. The process according to any of claims 12-17, wherein the membrane is operated with a temperature in the range of 500ºC to 1100°C.

19. The process according to any of claims 12-18, wherein a gas stream from the first chamber is supplied to an Air Separation Unit (ASU), which provides an oxygen enriched stream that is supplied to first chamber and an nitrogen-rich stream that is supplied to the second chamber; preferably wherein air is supplied to the ASU.

20. A nitric acid production process, comprising: - producing NOx with the process according to any of claims 12-19 for , and - reacting the NOx withdrawn from the second chamber with absorbent, preferably H2O, and optionally with O2, to form nitric acid; preferably carried out in a nitric acid production plant comprising the chemical reactor and an absorption unit (9) downstream of said outlet of the second chamber for contacting said gaseous stream from said second chamber with an aqueous absorption liquid (10) to form nitric acid.

21. The process according to claim 20, comprising adding an oxygen-containing gas stream, e.g. from the first chamber, to the gas stream withdrawn from the second chamber and preferably upstream of the absorption unit.

22. An ammonium nitrate production process, comprising: - producing nitric acid with the process according to claim 20 or 21 for producing ammonium nitrate, and - neutralizing the nitric acid with ammonia in a neutralization unit (15); wherein preferably the process is carried out in an ammonium nitrate plant according to claim 10.

23. The process according to claim 22, wherein the process further comprises: - producing the NH3 feed for neutralization unit in the ammonia synthesis unit (18) and - producing the H2 feed for the ammonia synthesis unit (18) in the water electrolysis unit (20) also giving an O2 stream (21).

24. The process according to claim 23, wherein the O2 stream (21) from the water electrolysis unit (20) is supplied at least in part to the first chamber (1) of the chemical reactor.

25. A chemical reactor, preferably for nitrogen fixation, comprising a first and a second chamber, a membrane comprising an oxygen transporting mixed ionic-electronic conducting material and separating the first and second chamber, an inlet for providing a first gas in the first chamber, an inlet for providing a second gas in the second chamber, an outlet for a gaseous product stream from the second chamber, and a plasma generator for forming a plasma in the second chamber; wherein the reactor preferably has the features defined in any of claims 2-6.

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