Method for methanol production

Abstract

The current invention relates to a method for methanol production, wherein the method comprises the steps of: (a) supplying one or more gaseous input streams to a plasma reactor, wherein the one or more gaseous input streams comprise at least CO2, H2O and CH4, (b) igniting a plasma in the plasma reactor, thereby allowing the CO2, H2O and CH4 to react and form syngas comprising CO and H2, (c) supplying said syngas to a methanol reactor, wherein said CO and H2 in the syngas are at least partially converted to methanol in said methanol reactor.

Description

[0001] METHOD FOR METHANOL PRODUCTION

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a method for optimizing syngas for use in methanol production.

[0004] BACKGROUND

[0005] The dry reforming of methane (DRM) in an atmospheric plasma reactor has been studied as a promising alternative to traditional methods. However, the resulting syngas from DRM has a low H2 / CO ratio, which limits its use for fuel production.

[0006] WO2020223789 describes a process wherein carbon dioxide, methane, and steam react at high temperatures (bi-reforming of methane), to form a syngas, which can then be used in a methanol production plant. However it has been found that the disclosure of WO2020223789 does not sufficiently solve the above issues.

[0007] Further, the implementation of this process in a plasma reactor has not been fully explored. The type of plasma reactor and the power level it operates at can significantly influence the performance and energy efficiency of the process.

[0008] SUMMARY OF THE INVENTION

[0009] The present invention and embodiments thereof serve to provide a solution to one or more of above-mentioned disadvantages. To this end, the present invention relates to a method according to claim 1. Preferred embodiments of the device are shown in any of the claims 2 to 15.

[0010] The invention relates to a method for methanol production using a plasma reactor. The method involves supplying gaseous input streams comprising CO2, H2O and CH4to the plasma reactor, igniting a plasma to allow the gases to react and form syngas. The inventors have found that in order to obtain an optimal syngas for fuel production, a total amount of H2O in the input gas stream of at least 40 % by volume is advantageous.

[0011] This particular ratio is significant as it optimizes the formation of syngas, thus enhancing the subsequent production of methanol. The syngas, in this case, is an advantageous mixture for methanol synthesis, due to the volume ratio of H2and CO approaching 2 without soot formation, which is an ideal condition for the production of methanol. The method, therefore, presents an innovative approach to the production of methanol, utilizing a plasma reactor and a specific ratio of gaseous inputs to optimize the process.

[0012] The invention provides a method that is efficient, cost-effective, and resourceoptimizing. By utilizing waste biogas as the single gaseous input stream and bypassing the need for biogas upgrading steps, the invention turns waste into value and contributes to a more sustainable and circular economy.

[0013] The method for methanol production described in the embodiments offers a sustainable and efficient solution to convert greenhouse gases into valuable commodity precursors.

[0014] The invention's method of producing methanol offers several advantages over traditional methods. The use of biogas as a source not only provides a renewable and sustainable method for methanol production but also reduces the environmental impact associated with conventional fossil fuel-based methods. By skipping the separation stage typically required in traditional methods, the invention also reduces the energy consumption and costs associated with methanol production.

[0015] DETAILED DESCRIPTION OF THE INVENTION

[0016] Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, term definitions are included to better appreciate the teaching of the present invention.

[0017] As used herein, the following terms have the following meanings:

[0018] The expressions "gliding arc (GA)", "glow discharge (GD)", "radiofrequency plasma (RF)",

[0019] "microwave plasma (MW)", "inductively coupled plasma (ICP)", "capacitive coupled plasma (COP)" and "dielectric barrier discharge (DBD)", as used in the text, refer to plasma generating means as would be understood by those in the art. "A", "an", and "the" as used herein refers to both singular and plural referents unless the context clearly dictates otherwise. By way of example, "a compartment" refers to one or more than one compartment.

[0020] "About" as used herein referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of + / - 20% or less, preferably + / -10% or less, more preferably + / -5% or less, even more preferably + / -1% or less, and still more preferably + / -0.1% or less of and from the specified value, in so far such variations are appropriate to perform in the disclosed invention. However, it is to be understood that the value to which the modifier "about" refers is itself also specifically disclosed.

[0021] "Comprise", "comprising", and "comprises" and "comprised of" as used herein are synonymous with "include", "including", "includes" or "contain", "containing", "contains" and are inclusive or open-ended terms that specifies the presence of what follows e.g. component and do not exclude or preclude the presence of additional, non-recited components, features, element, members, steps, known in the art or disclosed therein.

[0022] Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order, unless specified. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

[0023] The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within that range, as well as the recited endpoints.

[0024] The expression "% by weight", "weight percent", "%wt" or "wt%", here and throughout the description unless otherwise defined, refers to the relative weight of the respective component based on the overall weight of the formulation. The same applies for "volume%", "vol%", "% by volume".

[0025] Whereas the terms "one or more" or "at least one", such as one or more or at least one member(s) of a group of members, is clear per se, by means of further exemplification, the term encompasses inter alia a reference to any one of said members, or to any two or more of said members, such as, e.g., any >3, >4, >5,

[0026] >6 or >7 etc. of said members, and up to all said members.

[0027] Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, definitions for the terms used in the description are included to better appreciate the teaching of the present invention. The terms or definitions used herein are provided solely to aid in the understanding of the invention.

[0028] Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments. Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

[0029] In a first aspect the invention relates to a method for hydrocarbon production, preferably methanol production.

[0030] The method comprises the steps of: a. supplying one or more gaseous input streams to a plasma reactor, wherein the one or more gaseous input streams comprise at least CO2, H2O and CH4, and b. igniting a plasma in the plasma reactor, thereby allowing the CO2, H2O and CH4to react and form syngas comprising CO and H2.

[0031] In a preferred embodiment, said one or more gaseous input streams comprise

[0032] - a total amount of H2O of at least 40 % by volume; or - a total amount of H2O of at least 30 % by volume, wherein the specific energy input of the plasma reactor is at least 200 kJ / mol.

[0033] In a preferred embodiment, said gaseous input streams comprise a total amount of CH4and a total amount of CO2in a volume ratio of at least 1.8, preferably at least 2, preferably at least 2.5.

[0034] The syngas obtained from this method has been proven to be ideal for methanol production. It is therefore that in a further preferred embodiment, the method comprises the step of c) supplying said syngas to a Fischer-Tropsch reactor, preferably a methanol reactor.

[0035] In a particularly preferred embodiment, the method comprises the steps of: a. supplying one or more gaseous input streams to a plasma reactor, wherein the one or more gaseous input streams comprise at least CO2, H2O and CH4, b. igniting a plasma in the plasma reactor, thereby allowing the CO2, H2O and CH4to react and form syngas comprising CO and H2, c. supplying said syngas to a Fischer-Tropsch reactor, preferably a methanol reactor.

[0036] The ignition of the plasma in the plasma reactor allows the CO2, H2O and CH4to react and form syngas. It has been shown that the conversion of CO2and CH4(dry reforming of methane (A)) in a plasma reactor results in a syngas with CO and H2of low quality: the ratio between H2and CO molecules is only 0.5-0.6, which limits its use for fuel production.

[0037] CH4+ CO2-► 2CO + 2H2

[0038] By adding water vapor (gas phase) into the gas mixture, the inventors have been able to alter this H2 / CO ratio. With water in the mixture, steam reforming of methane (B) also occurs along with dry reforming of methane. This combination is called BRM (bi-reforming of methane (C)).

[0039] CH4+ H2O -> CO + 3H2(B)

[0040] 3CH4+ 2H2O + CO2-► 4CO + 8H2(C)

[0041] When the resulting syngas is preferentially used for the production of methanol according to reaction (D), a molar ratio of CO and H2of 1:2 in the syngas is optimal. co + 2H2-► CH3OH (D) Reaction (D) shows that a molar ratio of CO and H2of 1:2 is the optimal mixture for methanol synthesis. Although, reaction (C) indicates that a molar ratio of methane, water vapor (gas phase) and carbon dioxide of 3:2: 1 (stoichiometric ratio) should be used to obtain the molar ratio of CO and H2of 1:2, the inventors have now found that a stoichiometric ratio of 3:2: 1 (16.6% CO2- 50% CH4- 33.3% H2O) results in too much soot formation.

[0042] The inventors have found that the soot formation can be reduced either by increasing the specific energy input (SEI), i.e., either higher power or lower flow rate, or by increasing the amount of water vapor supplied to the plasma reactor.

[0043] In an embodiment, the method comprises the steps of: a. supplying one or more gaseous input streams to a plasma reactor, wherein the one or more gaseous input streams comprise at least CO2, H2O and CH4, b. igniting a plasma in the plasma reactor, thereby allowing the CO2, H2O and CH4to react and form syngas comprising CO and H2, c. supplying said syngas to a Fischer-Tropsch reactor, preferably a methanol reactor, wherein said one or more gaseous input streams comprise a total amount of H2O of at least 40 % by volume.

[0044] In an embodiment, the method comprises the steps of: a. supplying one or more gaseous input streams to a plasma reactor, wherein the one or more gaseous input streams comprise at least CO2, H2O and CH4, b. igniting a plasma in the plasma reactor, thereby allowing the CO2, H2O and CH4to react and form syngas comprising CO and H2, c. supplying said syngas to a Fischer-Tropsch reactor, preferably a methanol reactor, wherein said one or more gaseous input streams comprise a total amount of H2O of at least 30 % by volume, and wherein the specific energy input (SEI) of the plasma reactor is at least 200 kJ / mol.

[0045] In an embodiment, said one or more gaseous input streams comprise a total amount of H2O of at least 20 vol%, preferably at least 25 vol%, more preferably at least 30 vol%, even more preferably at least 35 vol%, even more preferably at least 40 vol%, and even more preferably at least 45 vol%.

[0046] In an embodiment, said one or more gaseous input streams comprise a total amount of H2O of between 20 and 70 vol%, preferably between 25 and 65 vol%, more preferably between 30 and 50 vol%, even more preferably of between 35 and 50 vol%, even more preferably between 40 and 50 vol%.

[0047] In an embodiment, said one or more gaseous input streams comprise a total amount of H2O of between 20 and 70 vol%, preferably between 25 and 65 vol%, more preferably between 30 and 50 vol%, even more preferably of between 30 and 45 vol%, even more preferably between 30 and 40 vol%.

[0048] This particular input optimizes the formation of syngas, thus enhancing the subsequent production of methanol. The syngas, in this case, is an advantageous mixture for methanol synthesis, due to the volume ratio of H2and CO approaching 2 without soot formation, which is an ideal condition for the production of methanol. The method, therefore, presents an approach to the production of methanol, utilizing a plasma reactor and a specific ratio of gaseous inputs to optimize the process.

[0049] The system facilitates the direct and instant conversion of primary inputs, namely CO2, H2O and CH4, into syngas. This omits any requirement for prior steps or temporary storage, boosting the efficiency of the process and uninterrupted flow in the entire procedure. The performance benefits have been seen to surpass those achieved with stoichiometric ratios, translating into an enhanced, flexible and environmentally friendly alternative to traditional gas reforming methods.

[0050] In a preferred embodiment, said one or more gaseous input streams comprise a total amount of CH4of at least 10 vol%, preferably at least 20 vol%, more preferably at least 30 vol%, even more preferably at least 35 vol%, even more preferably at least 40 vol%.

[0051] In a preferred embodiment, said one or more gaseous input streams comprise a total amount of CH4of between 10 and 70 vol%, preferably between 20 and 60 vol%, more preferably between 30 and 50 vol%, even more preferably of between 35 and 45 vol%, even more preferably between 40 and 45 vol%. In a preferred embodiment, said one or more gaseous input streams comprise a total amount of CO? of at least 5 vol%, preferably at least 10 vol%..

[0052] In a preferred embodiment, said one or more gaseous input streams comprise a total amount of CO2 of between 5 and 50 vol%, preferably between 10 and 40 vol%, more preferably between 10 and 30 vol%, even more preferably between 10 and 20 vol%.

[0053] In a preferred embodiment, said one or more gaseous input streams comprise a total amount of H2O and a combined total amount of CO2 and CH4in a volume ratio of at least 0.4, preferably at least 0.6, more preferably at least 0.8.

[0054] In a particularly preferred embodiment, the method comprises the steps of: a. supplying one or more gaseous input streams to a plasma reactor, wherein the one or more gaseous input streams comprise at least CO2, H2O and CH4, b. igniting a plasma in the plasma reactor, thereby allowing the CO2, H2O and CH4to react and form syngas comprising CO and H2, c. supplying said syngas to a Fischer-Tropsch reactor, preferably a methanol reactor, wherein said gaseous input streams comprise a total amount of CH4and a total amount of CO2 in a volume ratio of at least 1.8, preferably at least 2, preferably at least 2.5, and wherein said one or more gaseous input streams comprise a total amount of H2O and a combined total amount of CO2 and CH4in a volume ratio of at least 0.4, preferably at least 0.8.

[0055] In a particularly preferred embodiment, said one or more gaseous input streams comprise a total amount of CO2, a total amount of CH4, and a total amount of H2O in a volume ratio of 0.9-1.1 :2.8-3.0:3.1-3.3 or 0.9-1.1: 1.8-2.0:2.3-2.5.

[0056] In a particularly preferred embodiment, the method comprises the steps of: a. supplying one or more gaseous input streams to a plasma reactor, wherein the one or more gaseous input streams comprise at least CO2, H2O and CH4, b. igniting a plasma in the plasma reactor, thereby allowing the CO2, H2O and CH4to react and form syngas comprising CO and H2, c. supplying said syngas to a Fischer-Tropsch reactor, preferably a methanol reactor, wherein said gaseous input streams comprise a total amount of CH4of between 35 and 45 vol%, a total amount of CO? of between 10 and 20 vol%, and a total amount of H2O of 40 and 50 vol%.

[0057] In a particularly preferred embodiment, one gaseous input stream is supplied to the plasma reactor, wherein said gaseous input stream is biogas. In this embodiment, the methane, carbon dioxide and water vapor are all present in said biogas and supplied to the plasma reactor.

[0058] The biogas input stream is a renewable energy source, typically produced from raw materials such as bio waste, manure, municipal waste, sewage, green waste, etc. This biogas is produced through a process of anaerobic digestion by microorganisms inside a bio chamber or a bio-reactor. The resulting gas composition is a mixture of primarily CH4, CO2, and traces of H2O, H2S, and H2. Within this preferred embodiment, the biogas used may vary in its composition, but typically consists of a mixture of primarily CH4, CO2, with traces of H2O.

[0059] Typically, the gas mixture is purified by a separation stage, such as a distillation stage or a pressure-swing adsorption stage. In this way, the undesirable products such as CO2 and H2O are removed. This solution adds costs, as the separation process can be energy intensive. Moreover, CO2 gas is discharged, which is undesirable. The CO2 gas can be captured, but this will further increase the price of the CH4product.

[0060] The inventors have now found a method that resolves this problem by skipping the separation stage and replacing it with a specific plasma reactor, which facilitates dry reforming and steam reforming reactions of the methane, also known as bireforming of methane.

[0061] In this preferred embodiment, the method is thus characterized by the supply of a single gaseous input stream in step a, which is specifically a biogas. This embodiment is particularly advantageous in terms of efficiency and resource optimization. The invention allows for the direct utilization of biogas, thereby improving the overall efficiency of the process. It bypasses the need for biogas upgrading steps, which typically require significant energy input and add to the production costs. By eliminating these steps, the invention not only saves energy but also reduces the overall cost of methanol production. Furthermore, the invention turns waste biogas into valuable methanol, leading to greater resource optimization. Biogas, which is typically composed of methane, carbon dioxide, and traces of water, hydrogen sulfide, and hydrogen, is often considered a waste product. However, with this invention, such a waste product is transformed into a valuable chemical compound, methanol, which has numerous industrial applications. This not only adds value to the biogas but also contributes to waste reduction and promotes a circular economy.

[0062] It is to be understood that in this specific embodiment, wherein a single gaseous input stream in step a, which is specifically a biogas, is supplied to the plasma reactor, the above mentioned ratios and compositions of the one or more gaseous input streams apply equally. For example, "wherein said gaseous input streams comprise a total amount of H2O of at least 30 % by volume" would be equal to "wherein said biogas comprises a total amount of H2O of at least 30 % by volume".

[0063] In a particularly preferred embodiment, the method comprises the steps of: a. supplying a gaseous input stream to a plasma reactor, wherein the gaseous input stream is a biogas, and wherein the gaseous input stream comprise at least CO2, H2O and CH4, b. igniting a plasma in the plasma reactor, thereby allowing the CO2, H2O and CH4to react and form syngas comprising CO and H2, c. supplying said syngas to a Fischer-Tropsch reactor, preferably a methanol reactor.

[0064] The biogas used in this embodiment preferably has a relatively high water content compared to typical biogases which only comprise traces of H2O. Preferably, said biogas comprises a total amount of H2O of at least 30% by volume, or even at least 40% by volume.

[0065] Biogas with a high water content can be produced from feedstocks or waste materials that have a high moisture content. The water content in the biogas is largely influenced by the moisture content of the substrate used in the anaerobic digestion process.

[0066] In a preferred embodiment, the biogas is produced from food waste, sewage sludge, agricultural waste, animal manure, or aquatic biomass. Food Waste: Food scraps and waste from households, restaurants, and food processing industries often have high moisture levels. When anaerobically digested, the resulting biogas can contain significant amounts of water vapor.

[0067] Sewage Sludge: The anaerobic digestion of sewage sludge, which is the semi-solid material that remains after sewage treatment, can also produce biogas with a high water content. This is because sewage sludge typically contains a high percentage of water.

[0068] - Agricultural Waste: Certain types of agricultural waste, such as vegetable waste, green plant material, and fruit waste, have high moisture contents. When these materials undergo anaerobic digestion, the produced biogas tends to have a higher water vapor content.

[0069] - Animal Manure: Manure from livestock such as cows, pigs, and poultry contains a significant amount of water. Anaerobic digestion of these materials not only produces methane-rich biogas but also biogas with considerable water vapor due to the initial moisture present in the manure.

[0070] - Aquatic Biomass: Materials such as algae and aquatic plants have high water content. When these biomasses are used as feedstock for biogas production, the resulting gas can have a high level of water vapor.

[0071] In another or a further particularly preferred embodiment, two or more gaseous input streams are supplied to the plasma reactor, wherein one gaseous input stream is biogas, and one gaseous input stream is pure CO2 or pure H2O. The expression "pure" needs to be understood as being "made substantially of". Water, comprising a small amount of contaminants is as such still "pure H2O". Preferably, "pure" refers to at least 85 vol%, preferably at least 90 vol%, more preferably at least 95 vol%, most preferably at least 99 vol%.

[0072] This embodiment provides the advantage of allowing the addition of supplementary CO2or H2O streams to achieve the desired chemical balances, potentially leading to more effective and efficient methanol production. This embodiment offers a significant advantage in terms of method flexibility, as it is capable of accommodating multiple gaseous input streams. This is particularly advantageous as it allows for the optimization of the yield and quality of syngas.

[0073] This embodiment is specifically interesting when the biogas has a water or carbon dioxide content that is too low. The inventors have found that the addition of water vapor results in the bi-reforming of methane, resulting in more beneficial syngas compositions for subsequent fuel production.

[0074] In the event that the biogas source contains too much CH4for efficient operation, additional CO? can be introduced from a capture stage. Conversely, if the biogas source does not contain sufficient H2O, additional H2O can be introduced.

[0075] In a particularly preferred embodiment, the method comprises the steps of: a. supplying two or more gaseous input streams to a plasma reactor, wherein the gaseous input stream comprise at least CO2, H2O and CH4, and wherein one gaseous input stream is a biogas and one gaseous input stream is CO2or H2O, preferably H2O, b. igniting a plasma in the plasma reactor, thereby allowing the CO2, H2O and CH4to react and form syngas comprising CO and H2, c. supplying said syngas to a Fischer-Tropsch reactor, preferably a methanol reactor.

[0076] In a particularly preferred embodiment, two or more gaseous input streams are supplied to the plasma reactor, wherein one gaseous input stream is biogas, and one gaseous input stream is pure H2O (water vapor). The inclusion of pure H2O as a separate gaseous input stream in this embodiment contributes to the optimization of the syngas yield and quality. Biogas comprises typically only traces of water, but the inventors have found that higher amounts of steam are preferred to achieve an optimal syngas composition.

[0077] The water is preferentially introduced in the reactor in the form of water vapor, which can come from a water tank or an equivalent water source. The water can be supplied by a heated line. In a preferred embodiment of the invention, the method involves the use of H2O sourced from a liquid water tank. The liquid water from this tank is converted into steam, for example by a boiler and / or a heated steam line.

[0078] The size of the tank can vary depending on the scale of the operation, but it is preferable that the tank is large enough to hold sufficient water for continuous operation. The tank can be constructed from any suitable material that can withstand the heat and pressure involved in the conversion process.

[0079] In a preferred embodiment, the pure H2O is dry steam (>100°C), but alternatively operation is also possible with wet steam (about 100°C). It is to be understood that in this specific embodiment, wherein pure steam or carbon dioxide, together with a biogas, is supplied in step a, the above mentioned ratios and compositions of the one or more gaseous input streams apply equally. For example, "wherein said one or more gaseous input streams comprise a total amount of H2O and a combined total amount of CO2and CH4in a volume ratio of at least 0.3" would refer to the combined total amount of these components in these two streams.

[0080] Various types of plasma reactors for performing plasma-based gas conversion exist in the art. The plasma reactor according to the present disclosure is designed for efficient and stable operation in a glow discharge regime, which is generally characterized by lower plasma temperatures when compared to the arc discharge regime. More specifically, the plasma reactor according to the present disclosure is designed to generate a stable glow discharge plasma for obtaining a high gas conversion performance, for instance for the conversion of greenhouse gases. As discussed above, a reaction of particular interest is the DRM process for converting at the same time carbon dioxide and methane. Although the plasma reactor according to the present disclosure is particularly suited for operating in a glow discharge regime, depending on particular operational settings, e.g. power supply used, and gas flow regimes, the plasma reactor might also operate in an spark, arc or transitional discharge regime.

[0081] The plasma reactors that are used in the present invention, are preferably atmospheric pressure plasma reactors as they typically operate at atmospheric pressure.

[0082] In a preferred embodiment, the plasma reactor operates at atmospheric pressure.

[0083] In another or a further embodiment, the plasma reactor operates at a temperature to between 2500K and 5000K, more preferably between 3000K and 4500K, and most preferably around 3500K. This high temperature is preferred for facilitating the reactions that lead to the formation of syngas.

[0084] In a preferred embodiment, the plasma reactor comprises plasma generating means, said means chosen from the list of:

[0085] - gliding arc (GA)

[0086] - glow discharge (GD) radiofrequency plasma (RF) microwave plasma (MW) inductively coupled plasma (ICP)

[0087] - capacitive coupled plasma (CCP) dielectric barrier discharge (DBD).

[0088] In a more preferred embodiment, the plasma reactor comprises plasma generating means, said means chosen from the list of:

[0089] - gliding arc (GA)

[0090] - glow discharge (GD) radiofrequency plasma (RF) microwave plasma (MW) dielectric barrier discharge (DBD).

[0091] Each of these reactor types possesses unique characteristics that can be harnessed to enhance the efficiency and effectiveness of the bi-reforming of methane (BRM) process. In an even more preferred embodiment, the plasma reactor comprises plasma generating means, said means being gliding arc (GA). The gliding arc reactor has the ability to maintain a stable discharge even at high flow rates. This characteristic is particularly advantageous in the context of BRM, where the flow rates of the gas mixtures can be adjusted to optimize the production of syngas.

[0092] In another more preferred embodiment, the plasma reactor comprises plasma generating means, said means selected from gliding arc (GA) or glow discharge (GD). These plasma types are particularly well-suited for direct plasma-driven gas reforming processes, including dry reforming of methane (DRM), oxy-reforming of methane, and bi-reforming of methane (BRM). Their ability to operate efficiently at atmospheric pressure while maintaining stable plasma conditions enables high conversion of methane and carbon dioxide into syngas. Gliding arc and glow discharge plasmas promote effective electron-driven dissociation of CH4 and CO2, facilitating syngas production across different reforming pathways without requiring catalysts. These plasma systems provide a versatile approach to reforming reactions, allowing for optimized syngas composition by adjusting CO2, O2, or H2O content in the input stream while maintaining high process efficiency and scalability. Preferably, the plasma reactor is a contained plasma reactor. A contained plasma reactor ensures that the plasma discharge is confined within a controlled reaction environment, preventing unwanted interactions with external surfaces and maintaining consistent reaction conditions. More preferably, the plasma reactor is a contained, atmospheric gliding arc or contained, atmospheric glow discharge reactor. These reactor configurations have demonstrated significantly higher conversions under direct-plasma, non-catalytic conditions compared to other plasma reactor types. The atmospheric operation eliminates the need for vacuum systems, simplifying reactor design while reducing energy consumption and maintenance requirements.

[0093] Furthermore, gliding arc (GA) and glow discharge (GD) plasma reactors offer several advantages over radiofrequency (RF) and microwave (MW) plasma reactors. Specifically, GA and GD reactors exhibit much simpler operational setups, requiring fewer specialized components, such as complex impedance matching networks or waveguides, which are essential for RF and MW plasma systems. This simplicity translates to lower capital costs, easier scalability, and enhanced robustness for continuous operation. Moreover, GA and GD plasmas inherently generate moderate electron temperatures, which can drive the DRM reaction efficiently without excessive energy losses, improving process sustainability.

[0094] By utilizing a contained, atmospheric gliding arc or glow discharge plasma reactor, the present invention achieves an optimal balance between conversion efficiency, process stability, and system simplicity. These reactors enable a robust and scalable approach to direct-plasma DRM, mitigating the known challenges associated with plasma-catalytic systems and maximizing the advantages of non-catalytic syngas production.

[0095] In a preferred embodiment, the plasma reactor is a contained atmospheric glow discharge or gliding arc reactor, wherein the cathode-anode distance, defined as the shortest distance between the cathode and the anode, is at least 10 mm, more preferably at least 20 mm, even more preferably at least 30 mm, even more preferably at least 40 mm, even more preferably at least 50 mm, even more preferably at least 60 mm, and most preferably at least 80 mm. In another preferred embodiment, the cathode-anode distance is at most 100 mm, more preferably at most 90 mm, even more preferably at most 80 mm, even more preferably at most 70 mm, even more preferably at most 60 mm, and most preferably at most 50 mm. Increasing the distance between the anode and the cathode raises the breakdown voltage in the plasma reactor, resulting in higher energy consumption per molecule of reformed gas. This increased energy input enhances the dissociation of CH4 and CO2, leading to improved conversion efficiency and a higher syngas yield. A longer cathode-anode distance also extends the interaction time of the gas within the plasma zone, which positively influences the formation of CO and H2. However, an excessive distance can cause instability in the plasma discharge and increased electrode wear. By maintaining the cathode-anode distance within the optimized range of 50 mm to 80 mm, a balance is achieved between energy consumption, conversion efficiency, and plasma reactor stability, contributing to a robust and scalable reforming process.

[0096] In a preferred embodiment, the method involves operating the plasma reactor at a flow rate between 1 and 106L / min.

[0097] The plasma reactor, in this embodiment, is designed to handle a wide range of gas flow rates, thereby enabling the adaptability of the system. The flow rate is a parameter in the operation of the plasma reactor that directly affects the residence time of the gas in the reactor and therefore, the efficiency of the reforming reactions. The ability to operate at low flow rates, such as 1 L / min, allows for the method to be used in small-scale operations where the production of the incoming gas streams, such as biogas, is limited. Conversely, the ability to operate at high flow rates, up to 106L / min, allows for the method to be used in large-scale operations where large volumes of incoming gas streams, such as biogas, are produced.

[0098] In a more preferred embodiment, the plasma reactor is operated at a flow rate between 103and 105L / min, which provides balance between the residence time of the gas in the reactor and the efficiency of the reforming reactions.

[0099] The ability to operate the plasma reactor at different flow rates allows for the method to be adaptable to the varying composition of the incoming streams, for example biogas. The composition of the biogas can vary depending on the source of the biogas and the anaerobic digestion process. By adjusting the flow rate, the method can accommodate these variations and still produce syngas with the desired composition. This adaptability makes the method a versatile solution for the production of methanol from biogas.

[0100] In a preferred embodiment, the specific energy input of the plasma reactor is at least 150 kJ / mol, preferably at least 200 kJ / mol.

[0101] In a preferred embodiment of the invention, the method is optimized by ensuring that the syngas resulting from the bi-reforming process has a CO to H2volume ratio of between 1.5 and 2.5, preferably between 1.9 and 2.1. This optimal ratio is advantageous not only for the effectiveness of the methanol synthesis but also for the overall efficiency and environmental impact of the process. In a preferred embodiment of the invention, the method is optimized by ensuring that the syngas resulting from the dry reforming process has a H2 to CO volume ratio of between 1.0 and 3.0, preferably between 1.2 and 2.8, more preferably between 1.5 and 2.5, even more preferably between 1.7 and 2.3, even more preferably between 1.8 and 2.2, even more preferably between 1.85 and 2.15, and most preferably between 1.9 and 2.1. This optimal range is crucial for ensuring the efficiency of methanol synthesis and other hydrocarbon conversion processes, as well as for optimizing the overall energy balance and environmental impact of the reforming process.

[0102] At the broader end of the range, with H2 / CO ratios between 2.5 and 3.0, the syngas contains an excess of hydrogen, which may lead to suboptimal carbon utilization and favor side reactions such as methane formation via the Sabatier reaction. While a higher hydrogen content can be advantageous for hydrogenation reactions, it generally necessitates additional CO supplementation or recycling to achieve the correct stoichiometry for methanol production.

[0103] Conversely, when the H2 / CO ratio falls below 1.5, the syngas becomes hydrogendeficient, which can lead to incomplete methanol synthesis and an increased fraction of unreacted CO in the output stream.

[0104] The bi-reforming process, as previously described, involves the reaction of methane and carbon dioxide in the presence of steam in a plasma reactor. The resulting syngas, a mixture of carbon monoxide and hydrogen, is then preferably used in the production of methanol. The optimal ratio for methanol synthesis is generally considered to be around 2: 1, because of reaction (D).

[0105] The syngas produced from this process is of higher value than can be obtained by the method of WO2020223789. Because it is of higher value, it can be directly used for the synthesis of fuel products, such as methanol, thereby reducing the need for additional processing stages. This efficient use of syngas not only improves the overall productivity of the method but also reduces the operational costs.

[0106] Bi-reforming of methane (BRM) can be enhanced through the use of catalysts that promote the conversion of methane, carbon dioxide, and water into syngas (H2 and CO). Suitable catalysts for BRM typically include transition metal-based catalysts such as nickel (Ni), cobalt (Co), iron (Fe), and noble metals such as platinum (Pt), palladium (Pd), rhodium (Rh), and ruthenium (Ru), often supported on materials like alumina (AI2O3), ceria (CeO2), zirconia (ZrO2), or magnesium oxide (MgO). These catalysts aid in lowering the activation energy of the reaction, improving conversion efficiency, and enhancing selectivity toward syngas formation. While noble metals generally offer higher stability and resistance to carbon deposition, they are expensive, making nickel-based catalysts a more common choice due to their cost-effectiveness despite their susceptibility to deactivation.

[0107] Preferably, no catalysts are present in the plasma reactor itself. In a particularly preferred embodiment, the plasma reactor does not comprise a fixed-bed catalyst. In a further preferred embodiment, the plasma reactor does not comprise a catalyst. Plasma-based BRM operates through highly energetic conditions that facilitate the dissociation of methane, carbon dioxide, and water without the need for catalysts. A known limitation of catalytic BRM is catalyst deactivation, which can occur due to carbon deposition (coking), sintering of active metal sites, or poisoning by sulfur or other contaminants. While the presence of water in BRM helps mitigate coking by promoting oxidation pathways that convert deposited carbon into CO and H2, catalyst deactivation remains a significant issue that can lead to continuous fluctuations in the resulting H2 / CO ratio of the syngas. Such fluctuations have a profound impact on downstream processes, particularly in methanol synthesis, where precise control over the syngas composition is crucial. Additionally, while plasma-catalytic reactors hold significant potential in terms of reaction enhancement, they are extremely challenging to operate continuously in a stable, controlled, and scalable manner due to the complex interactions between plasmagenerated species and the catalyst surface.

[0108] More preferably, if a catalyst is employed, it is used downstream of the plasma reactor to optimize syngas composition post-plasma conversion. Even more preferably, the plasma is contained separately from the catalyst to ensure a stable and controlled process, minimizing the risk of catalyst degradation caused by direct plasma exposure. The present application seeks to overcome the known issues of catalytic BRM by focusing on direct plasma BRM. This approach eliminates the constraints associated with catalyst deactivation in the primary conversion step, providing a more robust and stable method for syngas production. The challenges linked to plasma-catalytic reactors can be partially mitigated by employing a two- stage system where direct plasma BRM is followed by a catalytic reactor in series. In this configuration, the catalytic BRM reactor is primarily utilized to refine conversion efficiency and improve selectivity toward the desired syngas composition. Furthermore, more preferably, a liquid trap is included between the plasma reactor and the catalytic reactor. This feature aids in reducing catalyst deactivation by capturing condensed water, heavy hydrocarbons, or other contaminants that could poison the catalyst. Advantageously, the majority of BRM is conducted in a non-catalytic environment, which significantly prolongs catalyst lifetime and ensures a more stable and predictable syngas output. In a preferred embodiment, the syngas produced in the plasma reforming step preferably comprises CH4, CO2, CO, H2, and H2O in a combined amount of at least 90 vol%, more preferably at least 95 vol%, even more preferably at least 98 vol%, even more preferably at least 99.0 vol%, even more preferably at least 99.5 vol%, and most preferably up to 99.9 vol%. More preferably, the syngas essentially consists of CH4, CO2, CO, H2, and H2O, and even more preferably, it essentially consists of CO, H2, and H2O, minimizing the presence of unreacted CH4 and CO2. In a further preferred embodiment, the amount of byproducts, including heavier hydrocarbons and oxygenated compounds, is at most 2 wt.%, more preferably at most 1 wt.%, even more preferably at most 0.5 wt.%, even more preferably at most 0.2 wt.%, even more preferably at most 0.1 wt.%, and most preferably at most 0.05 wt.%. Reforming reactors typically generate byproducts such as higher hydrocarbons and oxygenated hydrocarbons. In the two-stage reactor setup of the present invention, these byproducts should be minimized as much as possible to prevent operational issues in downstream processing. In particular, the formation of hydrocarbons such as ethyne (C2H2) and ethene (C2H4) should be avoided, as these compounds contribute significantly to coking and reactor fouling, leading to instability in both the plasma reactor and the subsequent Fischer-Tropsch (FT) or methanol reactor. Advantageously, the inventors have found that direct-plasma BRM in gliding arc and glow discharge reactors can maintain the total amount of hydrocarbons and unwanted byproducts below 1%, significantly reducing the risk of carbon deposition and improving reactor longevity. The presence of water in BRM further aids in limiting coke formation by promoting oxidation pathways that remove deposited carbon. This low byproduct formation allows for seamless coupling with downstream FT reactors or methanol reactors, ensuring stable operation and high syngas conversion efficiency. By carefully controlling plasma conditions and the water-to-carbon ratio, the present invention enables a clean, high-purity syngas composition optimized for further processing, while minimizing process inefficiencies associated with undesired side reactions.

[0109] In step c) of the method, the obtained syngas is supplied to a Fischer-Tropsch reactor (FT reactor).

[0110] A "Fischer-Tropsch reactor" or "FT reactor" refers to a chemical reactor used for conducting the Fischer-Tropsch synthesis, a process that converts syngas— a mixture of carbon monoxide (CO) and hydrogen (H2)— into liquid hydrocarbons, ranging from light fuels like gasoline to heavier waxy substances. This reactor is designed to facilitate the catalytic reaction under controlled conditions of temperature and pressure, optimizing the conversion of syngas to hydrocarbons.

[0111] In a particularly preferred embodiment, the FT reactor is a methanol reactor, such that in step b) the obtained syngas is supplied to a methanol reactor, wherein said CO and H2in the syngas are at least partially converted to methanol in said methanol reactor.

[0112] In a particularly preferred embodiment, the method comprises the steps of: a. supplying one or more gaseous input streams to a plasma reactor, wherein the one or more gaseous input streams comprise at least CO2, H2O and CH4, b. igniting a plasma in the plasma reactor, thereby allowing the CO2, H2O and CH4to react and form syngas comprising CO and H2, c. supplying said syngas to a methanol reactor, wherein said CO and H2in the syngas are at least partially converted to methanol in said methanol reactor.

[0113] The FT reactor is designed to operate at conditions that favor the conversion of syngas to the desired fuel products, such as methanol. The temperature in the FT reactor is preferably between 150°C and 350°C, more preferably between 200°C and 300°C, and most preferably between 220 and 300°C. The pressure in the methanol reactor can be between 20 and 200 bar, more preferably between 50 and 100 bar.

[0114] In another preferred embodiment, the heat produced from the FT reactor is used to generate and maintain water vapor. The FT reactor can be equipped with a heat exchanger or a water jacket that generates water vapor directly. This reduces costs by avoiding the use of a heated line and a boiler. Alternatively, waste heat can also be recovered from the plasma reactor by equivalent means.

[0115] In a preferred embodiment, the method involves the use of H2O sourced from a liquid water tank. In the current embodiment, the liquid water from this tank is converted into water vapor by utilizing the recuperated heat from the FT reactor. This embodiment offers a significant advantage in terms of energy efficiency, as it repurposes the heat generated by the FT reactor, which would otherwise be wasted, to convert water into water vapor. This reduces the total energy consumption of the process and contributes to a more sustainable and environmentally friendly method of methanol production. The use of recuperated heat from the FT reactor for this conversion process eliminates the need for additional energy input, which would be necessary if the water vapor were generated separately. This leads to significant energy savings and enhances the overall efficiency of the process.

[0116] In a preferred embodiment, the heat recuperated from the methanol reactor is transferred to the water in the tank, raising its temperature and causing it to vaporize into water vapor. The water vapor is then introduced into the plasma reactor where it participates in the bi-reforming reactions.

[0117] In another preferred embodiment, the liquid water tank is connected to the methanol reactor via a heat exchanger or similar device that facilitates the transfer of heat from the reactor to the water. The heat exchanger can be designed to maximize heat transfer efficiency and minimize heat loss to the environment. This further contributes to the energy efficiency of the system and the overall sustainability of the methanol production process.

[0118] The present invention is particularly directed toward a two-step process for methanol production, wherein the first step comprises plasma bi-reforming of methane (BRM) to produce syngas comprising CO, H2, and H2O, and the second step involves feeding the syngas to a separate Fischer-Tropsch reactor, preferably a methanol reactor, to convert the syngas into methanol. This two-reactor setup provides significant advantages over single-reactor configurations, particularly in terms of process flexibility, efficiency, and product separation.

[0119] A key advantage of this two-step approach is the ability to independently optimize the operating conditions of each reactor. Plasma bi-reforming of methane is most effectively conducted at or near atmospheric pressure, as higher pressures can destabilize plasma formation and reduce conversion efficiency. In contrast, the methanol reactor operates optimally at elevated pressures, preferably above 50 bar, to enhance methanol synthesis kinetics and increase single-pass conversion rates. By maintaining separate reactors, each stage can be individually finetuned to achieve maximum efficiency without compromising the conditions required for the other step. Additionally, the inclusion of water in the bi-reforming step allows for greater flexibility in tuning the H2 / CO ratio, further optimizing the syngas composition to suit downstream methanol production requirements.

[0120] Another major benefit is the improved ability to separate and recycle unreacted gases. The methanol reactor produces both liquid-phase methanol and a gaseous fraction comprising unreacted CO, H2, and byproducts such as CO2 and H2O. In the present invention, the output stream of the methanol reactor can be efficiently separated into liquid and gaseous phases, allowing the gaseous fraction to be recycled back to the methanol reactor to further increase conversion efficiency. This type of gas recycling is not feasible in a single-reactor setup, where plasma bireforming and methanol synthesis would occur in the same environment, leading to inefficient reactant utilization and product dilution.

[0121] Furthermore, separating the plasma bi-reforming step from the methanol synthesis step provides greater operational stability and scalability. The two-reactor system allows for better control of syngas composition, reducing fluctuations in the H2 / CO ratio that could negatively impact methanol yield. Additionally, by decoupling these two stages, each reactor can be designed with materials and configurations that best suit its respective reaction conditions, leading to improved reactor longevity and reduced maintenance requirements. The presence of water in BRM further aids in limiting carbon deposition, reducing fouling in both reactors and enhancing longterm system stability. This modular approach ultimately enhances process efficiency, improves methanol yield, and provides a more robust and scalable pathway for sustainable methanol production.

[0122] In another or further preferred embodiment, the method incorporates a recovery step, wherein water is recovered and reused from the fuel production process itself for the bi-reforming in the biogas reactor. The preferred embodiment of the method, which incorporates the recovery and reuse of water from the methanol production process for the bi-reforming of biogas, presents a significant advancement in the field of sustainable chemical processing. This approach not only enhances the efficiency of the process but also contributes to the conservation of water resources and the reduction of operational costs. In another preferred embodiment, the system optionally comprises a liquid-trap or separation drum fluidly connected between the plasma bi-reforming (BRM) reactor and the methanol reactor. More preferably, the syngas passes through from the plasma reactor to the methanol reactor, while the minor liquid fraction is separated. The inclusion of such a separation stage serves to remove liquid-phase components and solid impurities prior to introducing the syngas into the methanol reactor. Preferably, the liquid-trap or separation drum is configured to separate condensed water, unreacted hydrocarbons, and any entrained particulates that may form during plasma bireforming. More preferably, the separation drum is designed to operate passively, relying on differences in phase behavior rather than requiring additional energyintensive separation processes.

[0123] Advantageously, this intermediate separation step reduces the accumulation of liquid and solid impurities within the methanol production loop, thereby limiting the buildup of undesirable byproducts that could otherwise require complex downstream purification. While BRM inherently includes water in the reforming process, excess liquid water may negatively impact methanol synthesis conditions. By removing excess condensed water before the syngas enters the methanol reactor, this embodiment ensures that the H2 / CO ratio remains within the preferred range for methanol synthesis while preventing fluctuations in reactor conditions that could lead to catalyst deactivation. Additionally, separating any entrained hydrocarbons or solid impurities reduces reactor fouling, extends catalyst lifetime, and minimizes deactivation risks associated with the deposition of coke or heavy hydrocarbons. These benefits are achieved without necessitating a full-scale gas cleanup stage, thereby avoiding the high energy costs typically associated with conventional gasliquid separation units. As a result, the incorporation of a liquid-trap or separation drum provides an efficient, low-energy solution to maintaining reactor performance, ensuring process stability, and improving overall methanol production efficiency in a BRM-based system.

[0124] In a preferred embodiment, the FT reactor, more preferably methanol reactor is a fixed-bed catalytic reactor configured for the hydrogenation of carbon monoxide and carbon dioxide into methanol. The reactor preferably comprises a reaction chamber containing a heterogeneous catalyst, wherein said catalyst is preferably selected from copper-based catalysts, more preferably Cu / ZnO / AhOs, even more preferably a modified Cu / ZnO-based catalyst with enhanced thermal stability and resistance to deactivation. The methanol reactor is preferably designed to operate under elevated pressures to optimize conversion efficiency and maintain catalyst performance over extended operational periods.

[0125] In a preferred embodiment, the methanol reactor is operated at a pressure of at least 50 bar, more preferably at least 70 bar, even more preferably at least 80 bar, even more preferably at least 90 bar, and most preferably between 90 and 100 bar. Operating at high pressures enhances the conversion of syngas to methanol by shifting the reaction equilibrium toward methanol synthesis, thereby improving single-pass efficiency. In a further preferred embodiment, the methanol reactor is operated at a temperature of at least 150°C, more preferably at least 180°C, even more preferably at least 200°C, even more preferably at least 220°C, and most preferably between 220°C and 280°C. These temperatures ensure optimal catalytic activity while minimizing undesirable side reactions, such as excessive water formation or catalyst sintering.

[0126] The invention could, in a second aspect, be described as a method for optimizing syngas. Herein the embodiments of step a) and b) as described above correspond to the embodiments of this method.

[0127] The method comprises the steps of: a. supplying one or more gaseous input streams to a plasma reactor, wherein the one or more gaseous input streams comprise at least CO2, H2O and CH4, and b. igniting a plasma in the plasma reactor, thereby allowing the CO2, H2O and CH4to react and form syngas comprising CO and H2.

[0128] In a particularly preferred embodiment, said one or more gaseous input streams comprise a total amount of H2O of at least 40 % by volume.

[0129] The syngas has preferably a CO to H2volume ratio of between 1.5 and 2.5.

[0130] The present invention will be now described in more details, referring to examples that are not limitative.

[0131] EXAMPLES AND DESCRIPTION OF FIGURES

[0132] With as a goal illustrating better the properties of the invention the following presents, as an example and limiting in no way other potential applications, a description of a number of preferred applications of the method for examining the state of the grout used in a mechanical connection based on the invention, wherein:

[0133] Figure 1 schematically describes an embodiment of the invention.

[0134] Water vapor, methane and carbon dioxide are supplied to a plasma reactor 101, wherein the bi-reforming of methane is carried out following reaction (C), and a syngas 102 comprising CO and H2is obtained.

[0135] 3CH4+ 2H2O + CO2-► 4CO + 8H2(C)

[0136] When the resulting syngas is preferentially used for the production of methanol according to reaction (D), a molar ratio of CO and H2of 1 :2 in the syngas is optimal. CO + 2H2-► CH3OH (D)

[0137] Reaction (D) shows that a molar ratio of CO and H2of 1:2 is the optimal mixture for methanol synthesis. Reaction (B) indicates that a molar ratio of methane, water vapor (gas phase) and carbon dioxide of 3:2: 1 should be used to obtain the molar ratio of CO and H2of 1:2.

[0138] However, the inventors have found that a stoichiometric ratio of 3:2: 1 (16.6% CO2- 50% CH4- 33.3% H2O) results in too much soot formation.

[0139] Materials and methods

[0140] CH4and CO2(both 99.9 vol%) were purchased from Air Liquide, and the flow rates of both gases are regulated through Bronkhorst thermal mass flow controllers. Both gases are mixed with de-ionized water before entering the plasma reactor. The H2O container is heated by a silicon oil bath positioned over a hotplate stirrer (IKA RCT basic). The exact flow rate of H2O vapor (and hence its input fraction) is regulated through keeping the oil bath at a specific temperature. The calculations for the flow rates of H2O vapor (in mol / min) are provided in the SI (section SI). For each selected oil bath & H2O vapor temperature, the stainless steel gas line between the H2O container and the reactor inlet is heated up to a temperature approx. 10 °C higher than the oil bath temperature to avoid condensation of H2O and to allow the introduction of a homogeneous CO2-CH4-H2O gas mixture into the plasma. This is also why we refer to the H2O input as "vapor", and not as "steam": no heterogeneous H2O droplets enter the plasma reactor. The output gas mixture is led into a cold trap and carbon filter before entering a heated sample gas line, connected to an Agilent two-channel 990 MicroGC, which is used for analysis of the dry gas mixture.

[0141] 1. Soot formation & plasma stability

[0142] Table 1 clearly indicates that at the current conditions, a CH4fraction above ca. 42 vol% (comp ex. 1, ex. 4, 5, 8, 9) is accompanied with extensive soot formation. However, also the specific energy input (SEI, i.e. power divided by total input flow rate) has an influence. Specifically, we also tested the 14-41-45 (CO2-CH4-H2O) mixture with the same total input flow rate (3 Ls / min) but a higher plasma power (400 W instead of 300 W). At these conditions, the plasma was significantly more stable.

[0143] TABLE 1

[0144] At the same CH4input fraction, we also observed a difference in stability depending on the CO2:H2O ratio. For example, two mixtures in table 1 have 36 vol% CH4, yet the mixture with only 19 vol% CO2and 45 vol% H2O (ex. 12) was visibly more stable (no soot observed at reactor walls, stable plasma power at constant current and inter-electrode distance), while combined with 36 vol% CO2and only 28 vol% H2O (ex. 3), soot formation (and its effect on the plasma power) was clearly visible. Hence, this is highly beneficial compared to DRM (at CH4fractions > 35 vol%), where only in very specific cases (e.g. below atmospheric pressure and reverse vortex flow dynamics) soot formation can be inhibited.

[0145] 2. Effect of CO2:CH4ratio

[0146] Reference is made to figure 7, wherein (a) Conversion and yield (%), and (b) conversion and production rate (mmol / min) of the reactants and products, respectively, as a function of the CO2:CH4input ratio at a 45 vol% H2O input fraction.

[0147] CXHYstands for the combined yields and production rates of the small hydrocarbons detected, consisting of (in decreasing order) C2H2, C2H4, C2H6and CsHs (i.e. n- propane). In terms of yields and production rates, there is a visible decrease for CO and increase for H2. This is of course explained by the higher conversion rate of CH4and H2O and the lower CO2conversion rate. As a consequence, the syngas ratio (SR, H2 / CO) rises up to 2.03 (cf. Figure 6b), more than twice compared to the value at 1.86 CO2:CH4input ratio, and reaching the desired target for further downstream production of value-added oxygenates, e.g. methanol.

[0148] It is clear that changing the CO2:CH4ratio towards higher CH4amounts is beneficial, the best results are reached for almost all performance metrics (except CO2conversion) at the highest CH4fraction, and the most important targets (i.e., SR of 2 and energy cost below 412 kJ / mol) are achieved. The ideal stoichiometric BRM reaction dictates a 1-3-2 CO2-CH4-H2O mixture as input, while our best results are obtained for this 1-2.9-3.2 ratio. However, a drop in H2O content from 45 to 33 vol% (as dictated by the optimal stoichiometry), compromises the plasma stability due to too extensive soot formation (see Table 1: conditions in red).

[0149] Table 2 demonstrates that a higher SEI greatly improves the conversions and product yields, while the SR, EC and EE are only slightly worse. However, a SR of 1.94 it is still at a sufficiently high level for further methanol synthesis.

[0150] TABLE 2

[0151] Compared to pure DRM, the addition of H2O helps in counteracting soot formation, and thus in creating more stable plasma conditions. A mixture of 14-41-45 vol% (CO2-CH4-H2O) leads to the overall best results in terms of stable plasma and performance metrics. Specifically, at a SEI of 210 kJ / mol, we obtained a CO2and CH4conversion of 49 % and 74 %, respectively, at an EC of 390 kJ / mol converted reactants, which is below the target defined for plasma-based syngas production to be competitive with other technologies. Moreover, we reached CO and H2yields of 59 % and 49 %, and a SR of 2, which is ideal for further synthesis into methanol. In a specific embodiment of the invention, as depicted in figure 2, the incoming gaseous input stream is a biogas input stream. Biogas typically comprises methane, carbon dioxide and water. An exemplary biogas mixture is given in table 3.

[0152] TABLE 3

[0153] Typically in the prior art, biogas is purified by a separation stage, such as a distillation stage or a pressure-swing adsorption stage. In this way, the undesirable products such as CO? and H2O are removed. This method adds costs, as the separation process can be energy intensive. Moreover, CO2gas is discharged, which is undesirable. The CO2 gas could be captured, but this would further increase the price of the CH4product.

[0154] The inventors have now found a way to resolve this problem by skipping the separation stage and replacing it with a plasma reactor, as depicted in figure 2, which facilitates dry reforming and steam reforming reactions of the methane, also known as bi-reforming of methane according to reaction (1). Figure 2 shows a biogas input stream 203, comprising methane, carbon dioxide and water, being supplied to a plasma reactor 201. The resulting output gas mixture is a syngas 202, comprising H2and CO. The ratio of these products in the syngas is preferentially about 2.

[0155] The plasma reactor is preferably an atmospheric pressure reactor that brings the gas temperature to 3000K-5000K, more preferably 2500K-3500K, more preferably 2600K. The advantage of the plasma system is in the complete electrification of the process and the direct heating of the gas.

[0156] A further preferred embodiment of the invention is shown in figure 3. The inventors found that, although the biogas often comprises water, addition of another water source is beneficial. Typically biogas comprises water in the range of 0-10 vol%, but the inventors, however, have found that a higher amount is preferable. Preferably the gaseous input stream comprises water in an amount of between 30 and 50 vol%, more preferably between 35 and 50 vol%, most preferably about 45 vol%. The water can be introduced in the plasma reactor 301 in the form of steam, coming from a water tank or an equivalent water source 304. The water can be persevered in the steam form via a heated line 305, which can be built upon a resistive heated wire. It is most preferable to work with dry steam (>100 C, water vapor), but operation is also possible with wet steam (~100 C). The biogas 303 is simultaneously supplied to the plasma reactor 301, wherein syngas 302 is formed comprising H2and CO. The ratio of these products in the syngas is preferentially about 2. In another preferred embodiment the water source 304 could be a chemical process that produces waste steam.

[0157] In an even further preferred embodiment of the invention, the syngas stream can be converted directly to fuels or olefins 407 via a Fischer-Tropsch reactor 406. This is shown in figure 4, wherein numbers 401 to 405 correspond to numbers 301 to 305. Production of methanol (MeOH) is particularly attractive for the chemical and maritime shipping industry.

[0158] Moreover, producing fuels via an electrified reactor, entirely with biogas opens the possibility to designate the product as bio-fuel or e-fuel. This is a considerable advantage regarding market fit in the light of fossil reduction efforts.

[0159] In another or further preferred embodiment of the invention, as shown in figure 5, the heat produced from the FT reactor 506 can be used to generate and maintain steam. The FT reactor 506 can be equipped with a heat exchanger or a water jacket 509 that generates steam directly. The water can be supplied cold 508, heated 509 and supplied to the plasma reactor via a heated line 505. In this way, another cost is reduced in the sense of avoiding the use of a boiler. In figure 5 numbers 501 to 504 and 507 correspond to numbers 401 to 404 and 407. Alternatively, waste heat can also be recovered from the plasma reactor by equivalent means.

[0160] In another or further preferred embodiment of the invention, the water can be extracted from the FT reactor 606 itself. Water is a known by-product of the FT process, usually containing traces of hydrocarbons. Typically, the water is separated from the hydrocarbon components via a distillation column 610 and heated via a heat exchanger 611 with heat from the FT reactor 606. This is shown in figure 6 as an example. This embodiment is especially useful where water is less available. In figure 6 numbers 601 to 603 and 607 and 609 correspond to numbers 501 to 503 and 507 and 509.

[0161] The present invention is in no way limited to the embodiments described in the examples and / or shown in the figures. On the contrary, methods according to the present invention may be realized in many different ways without departing from the scope of the invention.

Claims

CLAIMS1. A method for methanol production, wherein the method comprises the steps of: a. supplying one or more gaseous input streams to a plasma reactor, wherein the one or more gaseous input streams comprise at least CO2, H2O and CH4, b. igniting a plasma in the plasma reactor, thereby allowing the CO2, H2O and CH4to react and form syngas comprising CO and H2, c. supplying said syngas to a methanol reactor, wherein said CO and H2in the syngas are at least partially converted to methanol in said methanol reactor, characterized in that, said one or more gaseous input streams comprise a total amount of H2O of at least 40 % by volume.

2. Method for methanol production according to claim 1, wherein the specific energy input of the plasma reactor is at least 150 kJ / mol, preferably at least 200 kJ / mol.

3. Method for methanol production according to any of the previous claims, wherein said one or more gaseous input streams comprise a total amount of CH4and a total amount of CO2 in a volume ratio of at least 2, preferably at least 3.

4. Method for methanol production according to any of the previous claims, wherein said one or more gaseous input streams comprise and a total amount of H2O and a combined total amount of CO2 and CH4in a volume ratio of at least 0.4, preferably at least 0.8.

5. Method for methanol production according to any of the previous claims, wherein said one or more gaseous input streams comprise a total amount of CO2, a total amount of CH4, and a total amount of H2O in a volume ratio of 0.9-1.1 :2.8-3.0:3.1-3.3.

6. Method for methanol production according to any of the previous claims, wherein the plasma reactor is an atmospheric pressure glow discharge plasma reactor.

7. Method for methanol production according to any of the previous claims, wherein the plasma reactor is operated at a power level between 300W and 500 MW.

8. Method for methanol production according to any of the previous claims, wherein said syngas has a H2to CO volume ratio of between 1.9 and 2.1.

9. Method for methanol production according to claim 1, wherein said one or more gaseous input streams comprise a total amount of CO2, a total amount of CH4, and a total amount of H2O in a volume ratio of 0.9-1.1:2.8-3.0:3.1- 3.3, wherein the specific energy input of the plasma reactor is at least 200 kJ / mol, and wherein the plasma reactor is an atmospheric pressure glow discharge plasma reactor.

10. Method for methanol production according to any of the previous claims, wherein one gaseous input stream is supplied in step a, and wherein said one gaseous input stream is a biogas.

11. Method for methanol production according to any of the previous claims, wherein two or more gaseous input streams are supplied in step a, wherein one gaseous input stream is a biogas, and one gaseous input stream is pure CO2 or pure H2O.

12. Method for methanol production according to any of the previous claims, wherein two or more gaseous input streams are supplied in step a, wherein one gaseous input stream is a biogas, and one gaseous input stream is pure H2O.

13. Method for methanol production according to claim 12, wherein said H2O comes from a liquid water tank, wherein said liquid water is converted to water vapor by using recuperated heat from the methanol reactor.

14. Method for methanol production according to claim 12, wherein said H2O comes from a liquid water tank, wherein said liquid water is converted to water vapor by using recuperated heat from the plasma reactor.

15. Method for methanol production according to claim 12, wherein said H2O is recovered from the methanol production process.

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