Process for decoupled production of hydrogen and carbon monoxide

Abstract

The present application relates to an advanced process for the decoupled production of hydrogen and carbon monoxide from hydrocarbons and carbon dioxide. This process combines the catalytic decomposition of hydrocarbons with the gasification of a solid carbon intermediate to separately produce and store hydrogen and carbon monoxide. From an industrial perspective, this process allows for an easy and highly flexible subsequent mixture of the two products that is critical for downstream processes.

Description

PROCESS FOR DECOUPLED PRODUCTION OF HYDROGEN AND CARBON MONOXIDE

[0001] This application relates to a process for decoupled production of hydrogen and carbon monoxide from hydrocarbons and carbon dioxide.

[0002] Synthesis gas (syngas), a mixture of hydrogen (H₂) and carbon monoxide (CO) is a pivotal intermediate in the production of various chemicals, fuels, and energy sources. Traditionally, syngas is produced through steam reforming of hydrocarbons (e.g., methane, ethane, ethylene, propane, propylene and butane) or partial oxidation processes. Steam reforming involves reacting hydrocarbons with steam at high temperatures (700 °C to 1000 °C) over a catalyst, usually nickel based. However, steam reforming consumes significant amounts of steam and produces large amounts of carbon dioxide (CO2) as a by-product. Partial oxidation involves reacting hydrocarbons with oxygen, producing syngas and CO2. It is less energy-intensive but suffers from incomplete conversion and low selectivity. Alternatively, dry reforming of hydrocarbons is an alternative method that offers the potential to utilize CO2as a feedstock, thereby addressing some of the environmental concerns associated with traditional methods. This process involves the reaction of hydrocarbons with CO2to produce syngas in one stage, thus requiring downstream purification processes to achieve desired syngas compositions. Compared to steam reforming, it does not require production or use of large amounts of steam and uses CO2instead as oxidizing agent. Despite its advantages, dry reforming presents several challenges, including catalyst deactivation (mainly by coke formation), low conversion rates and fixed hydrogen to carbon ratios in the final syngas composition.

[0003] Previous art method (EP3077099B1) reports a technology for hydrocarbon dry reforming in two separate stages for the decoupled production of hydrogen and carbon monoxide using a plasma-based process. The enthalpic needs for both reactions are ensured by electrodes or spark plugs put inside a reactor vessel that heat up gas feed streams using DC current. The heating elements heat up either the reactants or a mixture of them with an inert gas. The latter is more common for safety reasons but require additional separation units to remove the inert gases downstream. This invention promotes the reactions solely at the tip of the plasma torch where the flow gas is exposed to very high temperatures ofca.2000 °C. Since most of the reactor volume is not exposed to the reaction temperature, the process energy density is much lower than those using conventional fixed or fluidized bed reactors. Moreover, the high process temperatures make the process very energy intensive and require expensive reactor components to withstand the harsh process conditions.

[0004] Another approach (KR102257026B1) relates to a method for producing hydrogen from hydrocarbons, which can continuously produce high-purity hydrogen at a high yield by regenerating a deactivated metal catalyst to produce a regenerated metal catalyst. The document reports a method comprising two steps: (Step 1) performing a catalytic decomposition reaction of hydrocarbon; and (Step 2) performing a gasification reaction of the metal catalyst having the solid carbon deposited thereon with an oxidizing gas to produce carbon monoxide and a regenerated metal catalyst. The process operates at high temperatures (800 ºC to 900 ºC). While the patent claims the catalyst is "regenerated," it doesn't fully account for sintering caused by thermal stress; Repeatedly swinging between decomposition (carbon-forming) and gasification (carbon-removing) at high temperature causes the metal particles (nickel) to migrate and clump together. The 40% loss of hydrogen yield between cicle 1 and cicle 9 clearly shows that the catalytic stability is fairway from that necessary for industrial operation. This is caused by insufficient solid carbon gasification, still covering the Ni active sites, or by Ni particle migration / coalescence that reduces the active surface area, or by the formation of nickel aluminate that is catalytically inactive. Likely, this reason is behind the need to use the extremely high contact time ofca.25 gcath ml-1, leading to loss of efficiency and throughput.

[0005] The present invention relates to a process for the decoupled production of hydrogen and carbon monoxide comprising at least two separate stages:

[0006] - A catalytic decomposition stage carried out in a catalytic reactor wherein a hydrocarbon containing feed stream is contacted with a catalyst to undergo a decomposition reaction, yielding hydrogen and solid carbon in a stoichiometric ratio; wherein the solid carbon is formed at the surface of the catalyst;

[0007] - A gasification stage carried out in the same catalytic reactor in the presence of the same catalyst, wherein the solid carbon previously formed is contacted with a stream comprising CO2, yielding CO in a molar between ratio 0.01:1 and 1:2 of carbon dioxide to carbon monoxide;

[0008] wherein in both stages the reaction temperature is maintained between 500 °C and 1200 °C, and the reaction pressure is maintained between 10 to 3000 kPa.General Description

[0009] The present invention relates to the field of chemical engineering and, more specifically, to a novel process to produce hydrogen and carbon monoxide via catalytic decomposition of hydrocarbons followed by the gasification of solid carbon by carbon dioxide. This process leverages an optimized catalytic system and process design to produce hydrogen and carbon monoxide in two separate stages, thus enabling the adjustment of the product composition with high precision and flexibility. The invention is particularly suitable in downstream synthetic fuels production, petrochemical processing, and carbon capture and utilization. The dry reforming of hydrocarbons can be split into two separate stages to produce hydrogen and carbon monoxide in a stoichiometric but decoupled process herein described.

[0010] The decomposition stage comprises the catalytic decomposition of hydrocarbons to produce hydrogen and solid carbon by the following reactions:

[0011] CH4→ 2H2+ C; C2H6→ 3H2+ 2C; C2H4→ 2H2+ 2C; C3H8→ 4H2+ 3C; C3H6→ 3H2+ 3C; C4H10→ 5H2+ 4C.

[0012] These reactions are endothermic, and for example, in the case of methane as starting feedstock, the enthalpy change (ΔH°) isca.75 kJ mol-1at standard conditions, meaning energy input is required to drive the reaction forward.

[0013] Typical process temperatures for catalytic methane decomposition (CMD) range from 500 °C to 1200 °C or higher. This reaction is 100 % selective but high temperatures are typically necessary to overcome the activation energy of methane decomposition and to achieve reasonable reaction conversion, as the reaction is thermodynamically more favoured at elevated temperatures. This is the reason why most methane decomposition or pyrolysis technologies are based on plasma processes. Typical process pressures range from 0.1 – 3 MPa. Similar conditions are also found in the decomposition of other longer chain hydrocarbons (for example, ethane, ethylene, propane, propylene, butane, etc.).

[0014] At high temperatures, the equilibrium conversion of methane tends to approach completion, with hydrogen being the only gas-phase product. However, equilibrium conversion can vary depending on the system's operating conditions, particularly temperature and pressure. At temperatures close to 1000 °C and below 1 MPa, the equilibrium hydrocarbon conversion is nearly 100%, but lower temperatures reduce the reaction rate significantly requiring catalysts with high activity.

[0015] Metallic catalysts, typically made from metals like nickel, iron, or cobalt, are essential to lower the activation energy and enhance both conversion and selectivity. These catalysts can quickly deactivate (reversibly or permanently) over time due to carbon deposition, a challenge that requires careful management of process conditions or the development of more robust catalyst materials.

[0016] The formation of solid carbon at the surface of the catalyst typically follows two different reaction mechanisms: tip-growth or base-growth. It is common to observe a competition between both. In the tip-growth, carbon intermediates penetrate in the interior of catalyst particles and lift atoms that remain of the top of the carbon structure while it grows during the decomposition of more hydrocarbon. In contrast, the base-growth mechanism means that the carbon structure starts growing at the surface of the catalyst without the penetration in the catalyst particle and the ripening of metal atoms does not take place.

[0017] CMD is an attractive process because of its high selectivity for hydrogen production, with no CO or CO2formation in an ideal process, as the only by-product is solid carbon, which can be collected or used for industrial purposes. However, the production of solid carbon depends on the reaction stoichiometry. The mass balance of the reaction dictates that 4 kg of decomposed CH4originates 1 kg of H2and 3 kg of (solid) C. Depending on the process conditions, different carbon allotropes can be produced. Amorphous carbon black is typically produced in high temperature processes (≥ 1000 °C), including plasma or uncatalyzed processes. CMD at low temperature (550 – 1000 °C) can be enabled using metallic catalysts and special reactor designs. The most typical carbon by-products are carbon nanotubes, fibers or graphene.

[0018] Considering that 40% of the energy content of CH4gets trapped in the solid carbon by-product, it becomes obvious that the carbon needs to be handled and valorised commercially to make CMD an economically viable technology.

[0019] However, most of the several methane decomposition / pyrolysis technologies being developed aim at producing large amounts of clean hydrogen to compete with the conventional steam reforming and water electrolysis. If the global hydrogen demand in 2023 (ca.80 million tons) would be delivered by methane decomposition / pyrolysis technologies, 240 million tons of solid carbon would be produced as a by-product. In 2023, the global demand for carbon black was lower than 16 million tons (most produced from recycled carbon or incomplete combustion of hydrocarbons) and for carbon nanotubes it did not exceed 5000 tons.

[0020] To overcome this huge market barrier, it is critical to valorise the solid carbon by-product with a different strategy and produce another molecule that has an immediate and intensive market demand. The resulting solid carbon from CMD can be completely gasified by carbon dioxide through the reverse Boudouard reaction to enable the decoupled production of hydrogen and carbon monoxide in two separate stages, C + CO2→ 2CO.

[0021] This reaction typically occurs from 700 °C to 1200 °C. The enthalpy change for this reaction is endothermic,ca.172 kJ mol-1, which underscores the need the use of catalysts to drive the reaction forward and achieve favourable conversion rates. Group I and II elements are known to be excellent promoters for this reaction, considering the acidity of the CO2molecule. The basicity of these metals can create sites for carbon dioxide adsorption, thereby favouring its reaction with the solid carbon.

[0022] Equilibrium conversion rates for this gasification process are influenced by temperature, pressure, and the presence of catalysts, which can enhance the reaction kinetics. Under optimal conditions, high selectivity for CO can be achieved, often exceeding 90% in well-designed catalytic systems. The use of bi-functional catalysts not only facilitates the reaction but also helps to mitigate the formation of unwanted by-products, thus improving the overall efficiency of the process.

[0023] The present invention provides a sophisticated and efficient catalytic process for decoupled production of hydrogen and carbon monoxide from the decomposition of hydrocarbons followed by the gasification of the resulting solid carbon using carbon dioxide. It then becomes possible to precisely adjust on-stream hydrogen to carbon ratios that are crucial for increasing the efficiency of downstream processes (e.g. Fischer-Tropsch, methanol synthesis, etc.).

[0024] The presently disclosed process addresses the limitations of conventional methods by using precise process conditions that are cyclically changed to maximize the conversion and catalytic activity in both reaction stages. This enables then to use catalysts, and reactor designs already used in the common dry reforming process.

[0025] 1 - Catalyst Composition: A catalyst suitable to promote a base-growth mechanism for carbon growth at the catalyst surface.

[0026] 2 - Process Conditions: Optimized and tuneable operational parameters, including temperature, pressure, contact times and feed ratios.

[0027] 3 - Reactor Design: A fluidized bed reactor suitable to maximize contact between reactants and catalyst, ensuring efficient conversion without getting clogged be solid carbon intermediate.

[0028] For easier understanding of this application, figures are attached in the annex that represent the preferred forms of implementation which nevertheless are not intended to limit similar elements and in which:Fig.1

[0029] shows a process flow diagram of one embodiment of the present invention.Fig.2

[0030] shows the catalytic performance of the process at 750 °C and 0.1 MPa using a Ni / SiO2-Al2O3catalyst.Fig.3

[0031] shows the conversion of CH4in the decomposition stage.Fig.4

[0032] shows the concentration of reactants as a function of time at the outlet stream mixed with 100 ml min-1, needed for the analysis.Fig.5

[0033] shows the reaction conversion of each stage in the first 20 cycles.

[0034] Now, preferred embodiments of the present application will be described in detail with reference to the annexed drawings. However, they are not intended to limit the scope of this application.

[0035] The present invention is related to a process that combines the catalytic decomposition of hydrocarbons with the gasification of the solid carbon intermediate to produce and store hydrogen and carbon monoxide, which are the main components of syngas, in at least two separate stages. From an industrial perspective, the process allows for an easy and highly flexible mixture of the two compounds that is critical for downstream processes like Fischer-Tropsch or methanol synthesis that require accurate and tuneable H2 / CO ratios to be efficient and cost-competitive.

[0036] Moreover, this invention eliminates the need for purification steps or water-gas-shift reactors needed in the most typical steam reforming technologies. Like for the conventional dry reforming, this process does not require the continuous use of steam, and it is not favoured by operation at high pressure, ≥ 30 bar (3 MPa). This makes it especially attractive for decentralized biogas plants or to valorise the off gas from petrochemical plants. In both cases, gas feeds are already at low pressure and there is no need to compress them to 10 MPa – 20 MPa to achieve high conversion rates and high energy efficiencies, like needed for the steam reforming processes.

[0037] In one embodiment, when using biogas feedstock, it can be pre-treated to separate biomethane and biogenic CO2through a pressure swing adsorption (PSA) unit. Desulfurization coupled with dehumidifier units are used upstream to remove sulphur and water before feeding the biogas to PSA columns packed with a carbon molecular sieve adsorbent. The biogas is fed at 1 MPa – 3 MPa and the resulting CH4and CO2can then be stored to be used in a suitable reactor to carry out the presently disclosed process in two separate stages.

[0038] In another embodiment, the production of H2and CO by the presently disclosed process can be compensated with a proton conducting ceramic (PCC) electrolyser or a solid oxide electrolyser (SOEC), to produce hydrogen to be later mixed with syngas and reach average molar compositions of 2:1 H2 / CO suitable for a Fischer-Tropsch reactor to produce fuels. The high temperature electrolyser (550 – 950 °C) is fed by the steam produced from the Fischer-Tropsch process. The resulting products include C8–C12hydrocarbons later separated to produce jet fuel and diesel.

[0039] In another embodiment, the production of H2 and CO by the presently disclosed process can be compensated with a PCC electrolyser, or a solid oxide electrolyser, to produce hydrogen to be later mixed with syngas and reach average molar compositions of 2:1 H2 / CO suitable for methanol synthesis.

[0040] In another embodiment, the heat produced the above-mentioned processes can be used to pre-heat the feed streams of the presently disclosed process. In another embodiment, additional heat can be provided by heating elements, such as electrical resistances but not limited to, powered by electricity.

[0041] 1. Catalyst Composition

[0042] The process employs a catalyst suitable to significantly improve the efficiency and stability of the dry reforming process herein disclosed. The catalyst comprises:

[0043] Support Material: High-surface-area materials selected from metal oxides such as alumina (Al₂O₃), zirconia (ZrO₂), silica (SiO₂), or ceria (CeO2), or mixtures thereof. These materials provide a stable support for the active metals and enhance the dispersion of the metal components.

[0044] Active Metal Component: Metals selected from nickel (Ni), cobalt (Co), or iron (Fe), or mixtures thereof. Nickel is particularly suitable due to its high activity for hydrocarbon decomposition at lower temperatures. The metal component is typically present in a range between 5% to 80% by weight of the total catalyst.

[0045] In one embodiment, the catalyst can be prepared using methods such as impregnation, co-precipitation, or sol-gel techniques. For instance, a nickel-based catalyst can be prepared by impregnating a silica support with a nickel nitrate solution, followed by drying and calcination at high temperatures.

[0046] 2. Reaction Conditions

[0047] The process is carried out under carefully controlled conditions to maximize performance of the decomposition and gasification. The key parameters include:

[0048] Temperature: In both stages, the reaction temperature is maintained between 500 °C and 1200 °C. Higher temperatures increase the reaction rate and mainly the equilibrium conversion but may also lead to greater catalyst deactivation.

[0049] Pressure: In both stages, the reaction pressure is maintained between 10 kPa and 3000 kPa (0.0001 and 3 MPa). Elevated pressures can improve the reaction rate but the equilibrium conversions of the hydrocarbon decomposition and reverse Boudouard reaction are unfavoured.

[0050] Feed Ratios: The molar ratio of CO2to hydrocarbons is critical. A CO2:Hydrocarbons molar ratio between 0.005:1 and 5:1 is maintained to ensure a balanced reaction and minimize side reactions.

[0051] 3. Reactor Design

[0052] The reactor design plays a crucial role in enhancing the efficiency of the process. The reactor features:

[0053] Fluidized-Bed Configuration: The reactor is configured with a fluidized-bed, where the catalyst is packed in a fluidized manner within the reactor. This design ensures effective contact between the reactants and the catalyst while ensuring free volume to allow for carbon growth without destroying the catalyst structure.

[0054] Thermal Management: The reactor can be equipped with a thermal management system to maintain a uniform temperature distribution and to compensate the endothermic nature of both reactions. This system may include heating elements or external heat exchangers.

[0055] Flow Distribution: The reactor can comprise mechanisms to ensure even distribution of reactants across the catalyst bed. In one embodiment, this can be achieved by programming a dynamic flowrate of the reactant streams to exceed the minimum fluidization velocity during a complete reaction stage.

[0056] 4. Process Flow

[0057] The process flow is as follows:

[0058] Feed Preparation: In one embodiment, Hydrocarbons and CO2 can be independently pre-treated to remove impurities. This step may involve purification and / or compression of gaseous feeds.

[0059] Reaction: Hydrocarbons and CO2 are independently fed to the suitable reactor, where they contact the catalyst and undergo dry reforming. The reactions are carried out under the optimized conditions described above.

[0060] Product separation: In one embodiment, after the process, the independently obtained H2 and CO are separated from other by-products such as unreacted CO2, methane, and carbon monoxide. In one embodiment, this step may involve conventional separation techniques such as pressure swing adsorption (PSA) or membrane separation.

[0061] shows one embodiment of the Process Flow Diagram, wherein the reference numbers are:

[0062] hydrocarbon containing feed stream (1);

[0063] Carbon dioxide stream (2);

[0064] Catalytic reactor (3);

[0065] Carbon monoxide (4);

[0066] Hydrogen (5);

[0067] On-off valves (6)(7)(8)(9).

[0068] A catalytic reactor (3) carries out the stages of the process. The decomposing of hydrocarbons is carried out in one stage, while in a subsequent stage the solid carbon formed in the previous stage is gasified into carbon monoxide. In one embodiment, the process can carry on with a subsequent decomposition stage followed by another gasification stage as the catalytic reactor (3) can operate continuously alternating between the stages in a looping mode where solid carbon is a product of hydrocarbon decomposition but turns into a reactant in its gasification with CO2.

[0069] In the embodiment depicted in, in the decomposition stage of the process, an on-off valve (6) is opened to feed a hydrocarbon containing feed stream (1) to reactor (3), and an on-off valve (9) is opened to collect and store the hydrogen (5) produced.

[0070] After the decomposition stage on-off valves (6) and (9) are closed, and the gasification stage is carried out, where on-off valve (7) of opened to feed a carbon dioxide stream (2) to reactor (3) and on-off valve (8) is opened to collect and store the carbon monoxide (4) produced.

[0071] The process for the decoupled production of hydrogen and carbon monoxide herein disclosed comprises at least two separate stages:

[0072] - A catalytic decomposition stage carried out in a catalytic reactor wherein a hydrocarbon containing feed stream is contacted with a catalyst to undergo a decomposition reaction, yielding hydrogen and solid carbon in a stoichiometric ratio; wherein the solid carbon is formed at the surface of the catalyst;

[0073] - A gasification stage carried out in the same catalytic reactor in the presence of the same catalyst, wherein the solid carbon previously formed is contacted with a stream comprising CO2, yielding CO in a molar between ratio 0.01:1 and 1:2 of carbon dioxide to carbon monoxide;

[0074] wherein in both stages the reaction temperature is maintained between 500 °C and 1200 °C, and the reaction pressure is maintained between 10 to 3000 kPa.

[0075] In one embodiment, the contact time set for the process is between 0.01 and 1 gcath ml-1.

[0076] The units of contact time are given in grams of catalyst, per hour, per ml of reactant (i.e., hydrocarbon).

[0077] By catalyst is understood as the active metal phase and the support (i.e., support material selected from metal oxides).

[0078] The contact time (often the inverse of space velocity) is the primary indicator of how long the reactants are in direct contact with the catalyst surface. It serves as a vital metric to monitor reaction progress, product quality, and the health of the catalyst itself. Within a constant reactor volume, a reduction in residence time necessitates an increase in the superficial fluid velocity. This shift directly impacts the hydrodynamic state of the system, potentially driving a transition from a laminar regime, characterized by low velocities and extended contact times, toward transitional or turbulent flow states. Fluidized bed reactors operation faraway from laminar flow enhance mass and heat transfer between reactants and products, thus promoting complete solid carbon gasification that is critical to reach industrial-grade catalytic stability.

[0079] In one embodiment, the hydrogen and solid carbon molar ratio ranges from 1:1 to 2:1.

[0080] In one embodiment, the hydrocarbon containing feed stream is in the form of gas or liquid.

[0081] In one embodiment, the hydrocarbon containing feed stream and the stream comprising CO2are fed to the catalytic reactor at a temperature between 700ºC and 950ºC.

[0082] In one embodiment, in both stages the reaction temperature is maintained between 500 °C and 800 °C.

[0083] In one embodiment, in both stages the reaction temperature is maintained between 700 °C and 800 °C.

[0084] In one embodiment, in both stages the reaction temperature is maintained between 500 °C and 750 °C.

[0085] In one embodiment, in both stages the reaction temperature is maintained between 700 °C to 950 °C.

[0086] In one embodiment, in both stages the reaction temperature is maintained between 750 °C to 900 °C.

[0087] In one embodiment, in both stages the reaction pressure is maintained between 100 to 3000 kPa.

[0088] In one embodiment, in both stages the reaction pressure is maintained between 10 to 1000 kPa.

[0089] In one embodiment, in both stages the reaction pressure is maintained between 100 to 1000 kPa.

[0090] In one embodiment, the reaction pressure is maintained between 300 kPa and 1000 kPa.

[0091] The hydrogen produced during the decomposition stage exits the catalytic reactor before the gasification stage. In one embodiment, the hydrogen produced is stored for further use.

[0092] In one embodiment, the hydrocarbon containing feed stream comprises at least one hydrocarbon with a main chain comprising between 1 and 60 carbons, wherein said at least one hydrocarbon is saturated or unsaturated, with a linear or branched chain, or cyclic, or aromatic, or substituted.

[0093] In one embodiment, the at least one hydrocarbon is selected from, but not limited to, methane, ethane, ethylene, propane, propylene, butane, or mixtures thereof.

[0094] In one embodiment, the at least one hydrocarbon, or mixtures thereof, are sourced from, but not limited to, biogas, natural gas, off-gas, flue gas and shale gas.

[0095] In one embodiment, the catalyst comprises:

[0096] - a support material selected from metal oxides such as alumina, zirconia, silica, or ceria, or mixtures thereof;

[0097] - an active metal component selected from nickel, cobalt, or iron, or mixtures thereof, in a range between 5% to 80% by weight of the total catalyst.

[0098] In one embodiment, the average particle size of the catalyst’s active metal is > 2 nm.

[0099] In one embodiment, the average particle size of the catalyst’s active metal is between 2 nm and 2 µm.

[0100] In one embodiment, the average particle size of the catalyst is between 50 nm and 5 mm.

[0101] In one embodiment, the catalyst is in the form of pellets or powder.

[0102] In one embodiment, the catalyst is reducedin-situbefore the start of the decomposition stage to activate the metal active sites. In one embodiment, this activation step is carried out in inert atmosphere for a time between 15 and 180 min and a temperature between 500 and 1200 ºC. In one embodiment, the inert atmosphere comprises 1:1 H2 / N2, and the activation stage is carried out for 1 hour at 750 °C.

[0103] In one embodiment, the CO2:hydrocarbon molar ratio is from 0.005:1 to 5:1.

[0104] In one embodiment, the catalytic reactor is a fluidized-bed reactor. The fluidized bed comprises the catalyst suspended and mixed with the feed streams fluid inside the reactor. In the context of the present invention, a fluid is understood as a gas or a liquid.

[0105] In one embodiment, the catalytic reactor is a fluidized-bed membrane reactor. In in embodiment, the fluidized-bed membrane reactor is suitable to shift the thermodynamic equilibrium towards the formation of products below 1200ºC and below 100 kPa.

[0106] In one embodiment, the catalytic reactor is optionally purged with an inert gas, such as N2, before introducing the gaseous stream comprising CO2.

[0107] In one embodiment, the individual streams of hydrocarbon containing feed stream and of stream comprising CO2are pre-treated to remove impurities. In one embodiment, the pre-treatment is selected from a PSA or membrane separation.

[0108] In one embodiment, the hydrocarbon containing feed stream is a biogas feedstock, that is pre-treated to separate biomethane and CO2via PSA. In one embodiment, this pre-treatment comprises upstream steps of desulfurization coupled with dehumidification to remove sulphur and water before the PSA. In this embodiment, the biogas is fed at a pressure between 1 MPa – 3 MPa and the resulting CH4and CO2are used in the presently disclosed process.

[0109] In another embodiment, the process can further comprise a step carried out by a proton conducting ceramic electrolyser to produce hydrogen suitable to be mixed with the syngas produced in the presently disclosed process to reach an average molar composition of 2:1 H2 / CO suitable for a Fischer-Tropsch reaction. In this embodiment, a high temperature electrolyser, at a temperature between 550 and 950 °C, is fed by the steam produced from the Fischer-Tropsch process. The resulting products include C8–C12hydrocarbons which are suitable to produce jet fuel and diesel.

[0110] In another embodiment, the heat produced in the downstream step can be used to pre-heat the gaseous hydrocarbon containing feed stream and the gaseous stream comprising CO2of the presently disclosed process. In another embodiment, additional heat can be provided by heating elements, such as electrical resistances powered by renewable electricity, but not limited to.Examples

[0111] Example 1: Dry Reforming of CH4with CO2at 550 °C in a membrane reactor

[0112] 200 mg of 40 wt.% Ni supported on SiO2was loaded in the catalytic reactor (3) (). The reactor (3) was operated in a test station suitable for automatic operation and programming the time and operation conditions for the decomposition and gasification stages. Outlet gas compositions were analysed with an infra-red gas analyser, then used to calculate catalytic activity and the reaction conversion. The catalyst was first reducedin-situto activate the Ni active sites in an atmosphere of 1:1 H2 / N2, during 1 hour at 750 °C. The experiment was then carried out at 550 °C by feeding 50 ml min-1of CH4(1) to the catalyst during cycles of 1 hour (decomposition). The H2produced at this stage permeated through a Pd membrane (dead-ended operation), going beyond equilibrium-limited conversions.

[0113] The catalytic reactor (3) was then optionally purged with N2and then CO2(2) was introduced at 50 ml min-1to start the gasification reaction and convert the formed solid carbon to CO (4). The gasification stage was maintained until no CO was detected at the catalytic reactor (3) exit.

[0114] The catalytic performance of the catalytic reactor (3) at 550 ºC is shown inIn each stage the average catalytic activity wasca.3 gH2gNi-1h-1and, 9 gCOgNi-1h-1respectively. In the decomposition stage, the conversion of CH4wasca. 100% ().

[0115] Example 2:Dry Reforming of CH4 with CO2 at 750 °C

[0116] 150 mg of 20 wt.% Ni supported on Al2O3 was loaded in the catalytic reactor (3) (). The catalytic reactor (3) was operated in a test station suitable for automatic operation and programming the time and operation conditions for the decomposition and gasification stages. Outlet gas compositions were recorded with an infra-red gas analyser using 100 ml min-1 of N2 as sweep gas, then used to calculate catalytic activity and the reaction conversion. The catalyst was first reduced in-situ to activate the Ni active sites in an atmosphere of 1:1 H2 / N2, during 1 hour at 750 °C. The experiment was then carried out at 750 °C by feeding 50 ml min-1 of CH4 (1) to the catalyst during cycles of 2 min (decomposition). The H2 produced at this stage was stored and solid carbon was formed on the surface of the catalyst.

[0117] The catalytic reactor (3) was then optionally purged with N2and then CO2(2) was introduced at 50 ml min-1to start the gasification reaction and convert the formed carbon to CO (4). The gasification stage was maintained until no CO was detected at the reactor exit.

[0118] The catalytic performance of the catalytic reactor (3) at 750 °C is shown inIn each stage the average catalytic activity wasca.120 gH2gNi-1h-1and, 70 gCOgNi-1h-1respectively. The conversion of CH4 was 60 % in the decomposition stage and 30 % of CO2 in the gasification stage ().

Claims

A process for the decoupled production of hydrogen and carbon monoxide comprising at least two separate stages:- A catalytic decomposition stage carried out in a catalytic reactor wherein a hydrocarbon containing feed stream is contacted with a catalyst to undergo a decomposition reaction, yielding hydrogen and solid carbon in a stoichiometric ratio; wherein the solid carbon is formed at the surface of the catalyst;A gasification stage carried out in the same catalytic reactor in the presence of the same catalyst, wherein the solid carbon previously formed is contacted with a stream comprising CO2, yielding CO in a molar between ratio 0.01:1 and 1:2 of carbon dioxide to carbon monoxide;wherein in both stages the reaction temperature is maintained between 500 °C and 1200 °C, and the reaction pressure is maintained between 10 to 3000 kPa.Process according to the previous claim, wherein in both stages the reaction temperature is maintained between 500 °C and 800 °C.Process according to the previous claim, wherein the contact time set for the process is between 0.01 and 1 gcath ml-1.Process according to any of the previous claims, wherein the hydrocarbon containing feed stream is in the form of gas or liquid.Process according to any of the previous claims, wherein the hydrogen and solid carbon molar ratio ranges from 1:1 to 2:1.Process according to any of the previous claim, wherein the hydrocarbon containing feed stream comprises at least one hydrocarbon with a main chain comprising between 1 and 60 carbons, wherein said at least one hydrocarbon is saturated or unsaturated, with a linear or branched chain, or cyclic, or aromatic, or substituted.Process according to any of the previous claim, wherein the hydrocarbon containing feed stream comprises a hydrocarbon selected from methane, ethane, ethylene, propane, propylene, butane, or mixtures thereof.Process according to any of the previous claim, wherein the CO2:Hydrocarbons molar ratio is between 0.005:1 and 5:1.Process according to any of the previous claim, wherein the reaction pressure is maintained between 100 kPa and 3000 kPa.Process according to any of the previous claim, wherein the catalyst comprises:- a support material selected from metal oxides such as alumina, zirconia, silica, or ceria or mixtures thereof;- an active metal component selected from nickel, cobalt, or iron, or mixtures thereof, in a range between 5% to 80% by weight of the total catalyst;wherein the average particle size of the active metal is > 2 nm.Process according to any of the previous claim, wherein the average particle size of the catalyst’s active metal is between 2 nm and 2 µm.Process according to any of the previous claim, wherein the catalyst is in the form of pellets or powder.Process according to any of the previous claim, wherein the catalytic reactor is a fluidized-bed reactor.Process according to any of the previous claim, wherein the catalytic reactor is a fluidized-bed membrane reactor.Process according to any of the previous claim, wherein the individual streams of hydrocarbon containing feed stream and of stream comprising CO2are pre-treated via PSA or membrane separation.

Images