EP4337601A1 - Process for the conversion of co2 - Google Patents

Abstract

The present invention concerns a process for the conversion of CO₂, pure or contained in gaseous streams of various types via the use of an E-RWGS (Electrified Reverse Water Gas Shift) reactor. More specifically, the innovative process subject of the present invention reports a solution for the conversion of gases containing CO₂ into gases containing carbon monoxide (CO) and hydrogen (H₂), molecules that provide the building blocks for important activities in the production of chemicals, fertilizers and fuels.

Description

PROCESS FOR THE CONVERSION OF CO₂

DESCRIPTION

The present invention concerns a process for the conversion of pure CO₂ or various gaseous streams containing CO₂ by using an Electrified Reverse Water Gas Shift (E-RWGS) reactor. The electrified reactors that can be expediently used in the process include, for example, resistance-heated reactors (Science 364, (2019), 756-759) and induction-heated reactors (Ind. Eng. Chem. Res., 56 (2017) 14006-14013).

More specifically, the innovative process subject of the present invention refers to a solution for the transformation of gases containing CO₂ into gases containing carbon monoxide (CO) and hydrogen (H₂), molecules that provide the building blocks for important activities in the production of chemicals, fertilizers and fuels. This solution therefore aims to help reduce the concentration of GHG (Greenhouse Gases) by removing and transforming their main component, CO₂, and re- introducing it into the production cycle.

DESCRIPTION OF THE STATE OF THE ART

Reducing the atmospheric concentration of GHG, the main components of which are carbon dioxide (CO₂) and methane (CH₄), requires a more efficient use of the primary energy sources, an increase in the share of renewable energies and a reduction in the use of hydrocarbon sources. The increase in production of electrical energy obtained from renewable sources will lead to the promotion of water electrolysis processes, making available large quantities of H₂ for use in production chains both as an energy vector and as a chemical reactant . There will be a parallel development in conditions for the industrial use of electrified reactor solutions that replace the thermal reactors. CO₂, which is primarily generated by the combustion of hydrocarbons, has reached a concentration of 415 ppm in the atmosphere and is the most abundant GHG component. Its use as a source of carbon and oxygen is therefore one of the most important issues to be tackled in order to improve the sustainability of human activities and avoid increasing the temperature of the anthroposphere.

The problem was already evident in the 1980s and 1990s. The work described in Energy & Fuels (1996, 10, 305-325) can be cited, for example, which includes an extensive analysis of the ways in which CO₂ can be used, considering both: i) its physical properties (for example for supercritical extractions, Enhanced Oil Recovery, use as an inert gas in fire management and in other safety applications); ii) its chemical transformations (for example in the production of acids, alcohols and derivatives, urea and derivatives, polycarbonates).

However, even today, much less than 1% of the world production of CO₂ is re-used.

Even one of the most interesting ways of using CO₂, namely by integrating it in the production of methanol (MeOH), which can be used both in industrial chemistry production chains and in chains for the production of energy (see for example WO 2020/058859 A1) in internal combustion engines, has still not been developed.

Clearly the main difficulty is thermodynamic, as CO₂ is the end product of most human activities: i) those necessary for life (breathing emits one kilogram of CO₂ every day, equivalent to 2.5 billion tons emitted by the entire human race every year), ii) those dedicated to industrial processes for the production and use of energy, iii) those relating to chemical industry production. Overall these last two types of activity produce approximately 40.5 billion tons of CO₂ per year (see, for example https://www,ispionline.it/it//pubblicazione/co2--da·-- problema-risorsa-29423) . However, this situation can be changed by defining specific solutions for the use of CO₂ emissions .

In particular the intensive development of solutions that will make available significant quantities of electrical energy produced from renewable sources (sun, wind and hydroelectric power) has been initiated. Also the

European Union (EU Green Deal https://ec .europa.eu/commission/presscorner/detail/it/IP_ 19_6691) targets the use of electrical energy produced from renewable sources via the electrolysis of water and therefore for the production and use of H₂. However, it must also be said that, parallel to this, the reduction of GHG will have to take into consideration both the reduction of CO₂ emissions and separation and re-use of CO₂.

These solutions can follow either the Carbon Capture and Sequestration (or Storage, CCS) approach or the Carbon Capture and Utilization (CCU) approach.

Although CCS can become economically attractive when the carbon tax exceeds threshold values, the solution of storing this molecule underground in oil or gas fields that are depleted or becoming depleted, does not guarantee, in the majority of situations, permanent removal of the molecule and a significant reduction in emissions.

CCS is therefore a transitional solution, suitable for specific contexts in which storage solutions are available and also the possibility of recovering the CO₂ from industrial emissions, which is not always feasible. SUMMARY OF THE PRESENT INVENTION

The Applicant believes that the CCU solutions in which the CO₂ is re-used in the production cycle are much more effective and widely applicable and, among other things, can be more effectively integrated with activities for the production and use of H₂, in particular activities that produce it via water electrolysis processes.

In this regard, it should be noted that the production of hydrogen and use of it in reactions with CO₂ can be geared to the production of: i) Synthetic Natural Gas (SNG); ii) Methanol (MeOH) and its derivatives; iii) Ammonia/Urea; iv) Liquid hydrocarbons.

However, it must be pointed out that the direct hydrogenation of CO₂ into SNG, MeOH and liquid hydrocarbons is not particularly effective and not particularly selective in energy terms (for example, approximately 30-40% v/v of the hydrogen used in the synthesis of MeOH from CO₂ is transformed into H₂O and, to a lesser extent, into CH₄) and as regards the production of MeOH and liquid hydrocarbons, the solutions used are still at the prototype stage. On the other hand, a rapid development is predicted in the solutions that use electrolytic hydrogen in the synthesis of ammonia/urea.

In further detail, if the production of MeOH and hydrocarbon compounds is desired, the Applicant has found, and it is the subject of the present invention, that it is preferable to introduce into the production chain an E-RWGS (Electrified Reverse Water Gas Shift) phase and produce synthesis gas (a mixture containing mainly H₂ and CO) much more effectively via the reactions [1] and [2] instead of the sole reaction [3].

The combined process of the reactions [1] and [2] can furthermore employ widely used industrial solutions with well-known technical and economic feasibility. CO₂ + H₂ → CO + H₂O (DH = 42 kJ/mol) [1]

CO + 2 H₂ → CH₃OH (DH = - 89 kJ/mol) [2] C0₂ + 3 H₂ → CH₃OH + H₂O (DH = -48 kJ/mol) [3] CO₂ + 4 H₂ → CH₄ + 2H₂0 (DH = - 164 kJ/mol) [4] CO + 3 H₂ → CH₄ + H₂O (DH = - 206 kJ/mol) [5]

The present invention therefore concerns a process for the conversion of pure CO₂ or various gaseous streams containing CO₂ by using chemical processes that include the use of an Electrified Reverse Water Gas Shift (E- RWGS) reactor.

More specifically, the innovative process subject of the present invention refers to a solution for converting gases containing CO₂ into gases containing carbon monoxide (CO) and hydrogen (H₂), molecules that provide the building blocks for important activities in the production of chemicals, fertilizers and fuels.

In one aspect, the present invention provides a process, as defined previously, in which transformation of the CO₂ that takes place in the E-RWGS reactor uses, as a reactant, H₂ produced by electrolysis processes or made available as a by-product from various industrial processes.

In a further aspect, the present invention provides a process, as previously defined, in which the electricity necessary for the E-RWGS and/or electrolysis processes is produced from renewable sources.

In another aspect, the present invention provides a process, as defined previously, in which the E-RWGS reactor is integrated into process schemes: for the production of MeOH and its derivatives usable in the chemical and energy sectors;

- into process schemes which include a Fischer-Tropsch step for the production of liquid hydrocarbons usable in the chemical and energy sectors;

- into process schemes that use biogas for MeOH production from CO₂ and Bio-CH_4;

- into process schemes for the production of methanol, its derivatives and/or liquid hydrocarbon compounds, using acid natural gas (rich in CO₂₎ and/or other high CO₂ content off-gases of industrial processes;

- into process schemes for the production of blue-H₂ via the production of synthesis gases using the technologies of Steam Reforming (SR), Autothermal Reforming (ATR), Combined Reforming (CR) and in particular Catalytic Partial Oxidation (CPO); followed by a Water Gas Shift (WGS) step and separation of the H₂ from the stream containing the CO₂ which can be used to feed an E-RWGS step and re integrated in a cycle for the production of chemical or energy products;

- into process schemes for the production of MeOH or liquid hydrocarbons, via the Fischer-Tropsch process, using synthesis gas production processes such as Steam Reforming (SR), AutoThermal Reforming (ATR), Combined Reforming (CR) and in particular Catalytic Partial Oxidation (CPO) which make available, as a by-product, concentrated streams of CO₂.

In the process of the present invention, the E-RWGS reactor is operated at pressures between 10 and 100 atm (1.10 MPa and 10.13 MPa) and preferably at pressures between 30 and 80 atm (3.04 MPa and 8.11 MPa) and temperatures between 500 and 1000°C and preferably at temperatures between 650 and 950°C.

BRIEF DESCRIPTION OF THE FIGURES

Further characteristics and advantages of the process of the present invention will appear clearer from the following description, provided with reference to the attached figures which illustrate at least one non limiting embodiment example thereof.

In particular: figure 1 illustrates a simplified block diagram that integrates the unitary operations of E-RWGS, production of H₂ via water electrolysis processes (Solid Oxide Electrolysis Cell - SOEC, Alkaline Electrolyzer - AE, Polymer Electrolyte Membrane Electrolyzer - PEME) and synthesis of MeOH according to the present invention; figure 2 illustrates a simplified block diagram that integrates the unitary operations of E-RWGS, production of H₂ via water electrolysis processes (Solid Oxide Electrolysis Cell - SOEC, Alkaline Electrolyzer - AE, Polymer Electrolyte Membrane Electrolyzer - PEME) and synthesis of liquid hydrocarbons via the Fischer-Tropsch process; figure 3 illustrates a simplified block diagram of the CAMERE process described in Ind. Eng. Chem. Res. 1999, 38, 1808-1812; figure 4 illustrates a simplified block diagram of a process that allows the production, from biogas, of Bio- CH₄ and MeOH obtained from renewable sources and which, except for the CO₂ produced to obtain electrical energy, is configured as a CO₂ negative emission process; figure 5 illustrates a simplified block diagram of a process that allows hydrogen to be obtained via the CPO (Catalytic Partial Oxidation) process and a stream of CO₂ which by means of the E-RWGS unit is converted into synthesis gas that is used in the production of MeOH; this process, except for the CO₂ produced to obtain electrical energy, is configured as a CO₂ negative emission process; figure 6 illustrates a simplified block diagram of a process that allows hydrogen to be obtained via the CPO process and a stream of CO₂ which by means of the E-RWGS unit is converted into a synthesis gas with the appropriate composition to obtain the production of liquid hydrocarbons via the Fischer-Tropsch synthesis and which, except for the CO₂ produced to obtain electrical energy, is configured as a CO₂ negative emission process; figure 7 shows a process flow diagram of the production process of Example 1, sheet 1, in which:

• C-01: is the H₂ feed compressor;

• R-01: is the RWGS electrified reactor;

• HX-03: is the low temperature heat recovery exchanger;

• HX-04 is the syngas final cooler;

• C-02 is the CO₂ feed compressor;

• HX-01 is the RWGS reactor feed/product recuperator; • V-01 is the first H₂O separator;

• V-02 is the second H₂O separator;

• HX-02 is the high pressure steam generator;

• HS is High Pressure Steam;

• LS is Low Pressure Steam;

• HW is High Pressure Boiler Feed Water;

• LW is Low Pressure Boiler Feed Water;

• CWS is Cooling Water supply;

• CWR is Cooling Water Return;

• PW is Produced Water; figure 8 shows a process flow diagram of the production process of Example 1, sheet 2, in which:

• HX-05 is the MeOH product feed recuperator;

• R-02 is the MeOH synthesis reactor;

• C-03 is the recirculation compressor;

• HX-06 is the MeOH condenser;

• V-03 is the MeOH high pressure separator;

• V-04 is the MeOH low pressure separator;

• HG is High Pressure Steam;

• HW is High Pressure Boiler Feed Water;

• CWS is Cooling Water Supply;

• CWR is Cooling Water Return.

DETAILED DISCLOSURE OF THE PRSESENT INVENTION

Before describing in detail the preferred embodiments of the present invention or details thereof, it is useful to specify that the relative protective scope is not limited to the particular embodiments described below. The disclosure and description in the present document are illustrative and explanatory of one or more embodiments and variations currently preferred, and it will be clear to persons skilled in the art that various changes in the design, organization, order of operation, operation means, structures of the equipment and position, methodology and use of mechanical equivalents can be made without departing from the spirit of the invention.

Since many different distinct embodiments can be made within the scope of the concepts taught here, and since multiple modifications can be made to the embodiments described here, the details provided below shall be interpreted as non-limiting illustrations of the spirit of the invention.

Again with reference to figure 1, the block diagram describes for example one of the innovative conceptual solutions subject of the present invention. In this case a gaseous stream containing CO₂ is mixed with hydrogen produced by an electrolyzer and is sent to an electrified reactor in which the E-RWGS reaction takes place so as to produce a mixture of syngas suitable for synthesis of the methanol .

Analogously figure 2 describes a process solution in which the E-RWGS reactor is integrated in a scheme in which liquid hydrocarbons are produced by means of Fischer-Tropsch (FT) synthesis. Also in this case, a gaseous stream containing the CO₂ is mixed with hydrogen produced electrolytically and sent to the E-RWGS reactor so as to obtain a syngas with a composition suited to the Fisher-Tropsch synthesis and therefore to the production of liquid hydrocarbons.

In one aspect of the present invention, the electrified reactors that can be expediently used in the process include the resistance-heated reactors in which the catalyst is heated by Joule effect as described, for example, in the article published in Science 364, (2019), 756-759. This solution allows the radial temperature gradients through the catalyst layer to be significantly reduced, with much more effective transfer than in the SR thermal reactors - which use furnaces that are strong emitters of CO₂ - of the heat from the area where the strongly endothermic reactions occur, as in [6] below.

CH₄ + H₂O CO + 3H₂ (DH = 206 kJ/mol) [6]

In further detail, it is reported that the effectiveness of the heat transfer in the electrified reactors increases from approximately 50% (typical value of the thermal reactors) to over 90% depending on the solutions adopted. At the same time, the possibility of avoiding heating furnaces allows a drastic reduction in the dimensions of the reactors and the emissions of CO₂ into the atmosphere.

The electrified reactors that can be expediently used in the process of the present invention include induction- heated reactors which exploit the electromagnetic induction heating of an electrically conductive object through the heat generated inside the object itself by eddy currents. This type of reactor is described for example in the publication Ind. Eng. Chem. Res., 56 (2017) 14006-14013, which experimentally demonstrates the possibility of carrying out the SR reactions in a reactor containing nickel-cobalt nanoparticle-based catalysts. The co-component of the catalyst with a high Curie temperature is in this case able to transfer the necessary heat to the reaction environment.

These solutions adopted, for example for the SR reaction which requires high temperatures and pressures, can be extended and developed even more advantageously for the E-RWGS processes in which the chemical reactions require approximately 1/5 of the heat necessary for the SR processes.

Table 1 reports, in short, the comparison values between consumption and emissions per ton of methanol produced using: i) the Best Available Technologies (BAT) that use natural gas; ii) the CO₂ direct hydrogenation processes that use H₂ produced by electrolysis of H₂O; iii) the methanol production processes with the process of the present invention in which an E- RWGS intermediate step is included (see Example 1) and H₂ produced by the electrolysis of H₂O is used .

TABLE 1

(A) BAT - Best Available Technologies (i)

CHEMSYSTEMSPERP PROGRAM Methanol 07/08-2 November 2008 revised and updated and (ii) Methanol: The Basic Chemical and Energy Feedstock of the Future, Asinger's Vision Today, Editors: Bertau, M., Offermanns, H., Plass, L.,

Schmidt, F., Wernicke, H.-J. (Eds.)

(B) E-MeOH via direct hydrogenation of CO₂ (Appl. Energy

233-234 (2018) 1078-1093)

(C) MeOH via E-RWGS (see Example 1)

From the table it can be seen that the process of the present invention offers a considerable advantage in terms of carbon efficiency values (moles of carbon introduced into the process/moles of carbon converted into MeOH) with respect to the production of MeOH obtained by direct hydrogenation of CO₂ using electrolytically produced hydrogen (also called E-MeOH processes) and also with respect to the production processes of MeOH from natural gas. The process of the present invention also allows CO₂ emissions to be reduced by more than one order of magnitude compared to those of the other technological reference solutions.

The Energy Efficiency and Carbon Efficiency values are influenced mainly by the quantity and quality of electrical energy consumed in the electrolysis processes (see Example 1) and obviously make the technological solution more advantageous in contexts in which a surplus of electrical energy is used that would be otherwise difficult to use and/or in contexts in which renewable electrical energy is available.

The process of the present invention is compared with a known solution, developed from the end of the 1990s and called CAMERE (CO₂ Hydrogenation to form Methanol via a Reverse-Water-Gas-Shift Reaction; published in Ind. Eng. Chem. Res. 38 (1999) 1808-1812). The process, illustrated in Figure 3, is composed of two sections; in the first, a mixture containing CO₂ and H₂ enters a RWGS thermal reactor at approximately 500°C and 10 atm (1.01 MPa) producing CO and H₂O according to the equation previously described [1]. The water is subsequently separated and 40% of the gaseous mixture is recycled, while the remaining 60% v/v, which must have a composition in which the ratio (H₂-CO₂)/(CO+CO₂) is approximately equal to 2 v/v, is sent to the following section for compression and then synthesis of the MeOH which in the CAMERE process is carried out at a temperature of 250°C and pressure of 30 atm (3.04 MPa).

However, the CAMERE process only reached the pilot plant stage and has never been developed on an industrial scale. Industrially the RWGS thermal reactor should operate preferably at high temperature (above 700°C) and low pressure (below 15 atm) to discourage the methanation parasite reactions previously described in equations [4- 5].

The industrial thermal reactor would therefore require the use of a furnace that would use the combustion of hydrocarbons and which would therefore emit the very CO₂ that is intended to be converted. On the other hand, the synthesis of MeOH is favoured by high pressures (P > 50 atm) and by relatively low reaction temperatures (approximately 250°C). The syngas produced at low pressure in the RWGS would then have to be cooled and compressed, entailing a high energy expenditure.

For these reasons, as already mentioned, the CAMERE process was tested, operating the RWGS thermal reactor at approximately 500°C and 10 atm and then compressing the synthesis gas obtained to 30 atm and carrying out synthesis of the MeOH at 250°C. The hydrogen was produced from non-renewable sources.

Overall the CAMERE process does not lead to improvements in terms of CO₂ emissions, carbon efficiency and energy efficiency compared to the "conventional" MeOH production processes that use Natural Gas (NG) and entail the production of synthesis gas using the Steam Reforming (SR), AutoThermal Reforming (ATR), Combined Reforming (CR) and non-Catalytic Partial Oxidation (POx) technologies described for example in:

"Technologies for large-scale gas conversion", Aasberg-Petersen, K., BakHansen, J. -H., Christensen, T. S., Dybkjaer, I., Christensen, P. Seier, Stub Nielsen, C., Winter Madsen, S. E. L., Rostrup-Nielsen, J. R., Applied Catalysis A: General, 221 (1-2), p.379, Nov 2001;

"Synthesis Gas production by Steam Reforming", Dybkjaer,lb; Seier Christtensen P.; Lucassen Hansen V.; Rostrup-Nielsen J.R., EP1097105A1;

J.R. Rostrup-Nielsen, J. Sehested and J.K. Noskov, Adv. Catal. 47 (2002), pp. 65-139;

"Catalytic Steam Reforming"; Rostrup-Nielsen J.R.; pg 1-117, Catalysis Vol. 5, Edited by John R. Anderson and Michel Boudart.

The process, subject of the present invention, clearly exceeds the limits of the known CAMERE process, using an E-RWGS reactor that can operate at high temperature, ranging from 650°C to 1000°C (in conditions that inhibit the methanation reaction [4-5]) and preferably between 700°C and 950°C and at high pressure ranging from 25 to 100 atm (2.53 MPa and 10.13 MPa) and preferably between 30 and 80 atm (3.04 MPa and 8.11 MPa).

Furthermore, the process subject of the present invention entails the use of sources of hydrogen (AE, SOEC, PEME) produced via hydrolysis processes that preferably use renewable energy or surplus of electrical energy or energy coming from other industrial processes that do not use hydrogen directly.

The process of the present invention also entails the possibility of using CO₂ separated from various hydrocarbon sources (for example biogas and acid gases) or obtained as a by-product of different industrial processes (for example those from which blue-hydrogen can be obtained).

For example, Figure 4 shows a diagram in which the stream of treated CO₂ comes from the biogas which in this way allows a stream of biomethane (Bio-CH₄) and Bio-MeOH to be obtained from renewable sources.

More in particular the diagram of Figure 4 allows a production of Bio-CH₄ and Bio-MeOH to be obtained with negative emissions of CO₂ except for that emitted in the production of electrical energy. If the latter is obtained completely or at least partly from renewable sources or if it is taken from a situation that produces it in excess, the scheme configures a process with negative emissions of CO₂.

Figure 5 shows a simplified block diagram in which a production process of Blue-Hydrogen (like the one described in US2012/031391 A1 in which a stream of hydrogen and a high concentration stream of CO₂ is obtained) is integrated with a step of E-RWGS and synthesis of the MeOH.

Figure 6 shows a simplified block diagram in which a production process of Blue-Hydrogen (like the one described in US2012/031391 A1), in which a current of hydrogen and a high concentration current of CO₂ is obtained, is integrated with a step of E-RWGS and Fischer Tropsch (F-T) synthesis of the liquid hydrocarbons.

The schemes of Figures 5 and 6 include, in particular, a technology of Catalytic Partial Oxidation (CPO)(the following pages include the references of 16 patents and 5 publications that describe the technology) with low contact time which allows the production of syngas without using pre-heating furnaces, therefore making the technology particularly suitable for confining all the CO₂ emissions within the process gas from which it can be entirely recovered.

The use of this CO₂ according to the process of the present invention, in particular in the schemes shown in figures 5 and 6, which include an E-RWGS reactor, allows all or part of the CO₂ emissions to be converted into a chemical product or into a fuel of renewable origin and therefore also the corresponding share of H₂ to be shifted from blue to green.

The schemes shown in figures 5 and 6 also entail using the production of O2 associated with the production of H₂ in water electrolysis to feed the CPO process, with a further improvement in overall process efficiency.

The schemes of Figures 5 and 6 can be developed obtaining the production of H₂ also via the processes of Steam Reforming (SR), AutoThermal Reforming (ATR) and Combined Reforming (CR) but the use of the CPO technology makes them far more efficient and drastically reduces the CO₂ emissions as it allows all the process furnaces to be eliminated.

The CPO technology referred to is described in numerous documents in literature, including:

W02020058859 (Al), WO2016016257 (Al), WO2016016256 (Al), W02 016016253 (Al), W02016016251 (Al), WO 2011151082, WO 2009065559, WO 2011072877, US 2009127512, WO 2007045457, WO 2006034868, US 2005211604, WO 2005023710, WO 9737929, EP 0725038, EP 0640559;

"Issues in H₂ and synthesis gas technologies for refinery, GTL and small and distributed industrial needs"; Basini, Luca, Catalysis Today, 106 (1-4), p.34, Oct 2005;

"Fuel rich catalytic combustion: Principles and technological developments in short contact time (SCT) catalytic processes"; Basini, L.; Catalysis Today, 117(4), 384-393; DOI: 10.1016/j.cattod.2006.06.043 Published: OCT 152006;

"Natural Gas Catalytic Partial Oxidation: A Way to Syngas and Bulk Chemicals Production | IntechOpen"; G. Iaquaniello, E. Antonetti, B. Cucchiella, E. Palo, A. Salladini, A. Guarinoni, A. Lainati and L. Basini; http://dx.doi.org/10.5772/48708;

"Short Contact Time Catalytic Partial Oxidation (SCT-CPO) for Synthesis Gas Processes and Olefins Production"; L.E. Basini, A. Guarinoni, Ind. Eng. Chem. Res. 2013, 52, 17023-17037; https://dor .org/10.1021/ie402463m.

Example 1

Conversion process of CO₂ to MeOH

There are 15,000 European plants that produce biogas, a mixture containing approximately 50% of CPU and 50% of CO₂, via the process of anaerobic digestion. The biomethane obtained after the removal of CO₂ is injected into the natural gas network and used, for example, for fuelling motor vehicles or producing electricity. This solution is widely applied throughout Europe and receives state subsidies. However, the drop in the production costs of renewable energy will favour the development of new solutions, in particular solutions that include process units dedicated to the re-use of CO₂. Due to the small dimensions of the European plants, the available CO₂ flow rates are between 100 and 500 Nm³/hour, with the mean value being 300 Nm³/hour associated with a biogas plant that produces 1.2 MW of electricity.

The process exemplified combines flows of CO₂ coming from the biogas and green H₂ obtained via electrolysis, for the production of MeOH.

In particular a technical-economic study has been developed in which approximately 300 Nm³/hour of CO₂ and 938 Nm³/hour of H₂ produced by Polymer Electrolyte Membrane Electrolyzer (PEME) are used. The study was developed using the Aspen Plus V10 software, simulating the performances in literature of the unit operations of RWGS and synthesis of MeOH.

Process scheme

The flowsheet used is shown in Figures 7 and 8. In the scheme adopted, both the CO₂ and the H₂ are compressed to approximately 50 bar and the hydrogen is then split into two flows. The first is mixed with the CO₂, and the mixture is heated to 650°C before entering the E-RWGS reactor which it is assumed operates at 950°C. The stream flowing out of the reactor containing CO₂, H₂, CO, H₂O and CH₄ is cooled to 20°C to remove the water produced by the E-RWGS reaction. The gaseous stream thus obtained is mixed with the hydrogen to adjust the methanol module (SN) of the syngas SN = (H₂-CO₂)/(CO+CO₂)

The syngas thus obtained is mixed with the recycle stream of the MeOH synthesis section and heated to 250°C before entering the MeOH synthesis reactor which operates at approximately 50 bar. The reaction product is cooled to 25°C to separate the mixture of water and MeOH from the species that remain gaseous. 10% v/v of the gaseous stream is purged to avoid the accumulation of by-products (e.g. CH₄) while the remainder is recycled to the MeOH synthesis reactor. E-RWGS unit

The reactor operates at equilibrium at 950°C and 50 atm using a Ni/Al2C>3 catalyst and a gas hour space velocity (GHSV) equal to 5000 NL/(kg x hour). The feed uses a ratio H₂/CO₂ = 2 v/v.

The electrification of the reactor is designed with a 90% transfer efficiency of heat generated by Joule effect. The generation of heat in situ in the reaction environment minimizes heat transfer limitations. This situation is obtained by using, for example, as a support in the catalytic bed, a FeCrAl monolith in the form of high resistivity knitted gauze on the surface of which the active phase is deposited.

The resistivity within the catalytic bed is maximized by dispersing the networks among ceramic materials that avoid electric short circuits and at the same time allow the reaction mixture to cross the catalytic bed. The power load is obtained by minimizing the current flow using a low voltage and a high amperage.

MeOH synthesis reactor

The reactor operates at 50 bar and at an isothermal temperature of 250°C and was simulated as an equilibrium reactor with approach temperatures of 10°C. The results of the simulation were compared with those of an industrial reactor that uses a commercial catalyst based on Cu/Zn0/Al₂O₃ and that operates with a GHSV of 8,000 NL/ (kg x hour). The purge on the recycle gas was obtained by inserting a Pressure Swing Adsorption (PSA) unit that allows 90% of the hydrogen to be recovered and re introduced into the synthesis loop.

Results

Tables 2-9 include indications on the material and energy balances and on the main process conditions.

Table 10 includes the overall consumption of material and energy for two cases:

Case A: no purge is used in the methanol synthesis loop, 7.5% v/v of methane at the inlet and 9.5% v/v of methane at the outlet (preferred situation).

Case B: 10% v/v of the recycle gas of the methanol synthesis loop is purged, 5.6% v/v of methane at the inlet, 7.1% v/v of methane at the outlet. The purge is burnt to produce thermal energy which is used by an Organic Rankine Cycle.

Claims

1. Process for the conversion of pure CO₂ or various gaseous streams containing CO₂ by using an Electrified Reverse Water Gas Shift reactor (E-RWGS) co-fed with a gaseous stream containing H₂ and integrated in process schemes leading to fuels and chemicals productions.

2. Process according to claim 1, wherein the CO₂ conversion takes place in the electrified E-RWGS reactor utilizing a hydrogen reactant produced by an electrolytic process.

3. Process according to claim 1, in which CO₂ conversion takes place in an electrified E-RWGS reactor which uses as a reactant a stream containing Hydrogen which is made available as a by-product from various industrial processes.

4. Process according to claims 1-3, in which the energy necessary for the E-RWGS and/or electrolysis processes is produced from renewable sources.

5. Process according to claims 1-4, in which the electrified E-RWGS reactor is integrated into process schemes for MeOH production.

6. Process according to claims 1-4, in which the electrified E-RWGS reactor is integrated into process schemes which include a Fischer-Tropsch step for the liquid hydrocarbons production usable in the chemical and energy sectors.

7. Process according to claims 1-6, in which the E-RWGS reactor is operated at pressures between 10 and 100 atm and preferably at pressures between 30 and 80 atm and temperatures between 500 and 1000°C and preferably at temperatures between 650 and 950°C.

8. Process according to claims 1-7, wherein the electrified E-RWGS reactor is integrated into process schemes that use Bio-Gas for the MeOH production from CO₂ and Bio-CH₄.

9. Process according to claims 1-7, in which the electrified reactor of E-RWGS is integrated into Methanol or liquid hydrocarbon compounds production processes, using CO₂-enriched Acid Natural Gas, and/or other high CO₂ content off-gases of industrial processes.

10. Process according to claims 1-7, in which the electrified E-RWGS reactor is integrated into process schemes for the H₂ and MeOH co-production in which synthesis gas production processes is performed such as Steam Reforming, Autothermal Reforming, Combined Reforming and in particular with Catalytic Partial Oxidation.

11. Process according to claim 10, wherein the electrified RWGS reactor is integrated into process schemes for H₂ and liquid hydrocarbons co-production, in which synthesis gas production processes is performed such as Steam Reforming, AutoThermal Reforming, Combined Reforming and in particular with Catalytic Partial Oxidation and the liquid hydrocarbons are obtained by the Fischer-Tropsch process.