Process for production of methanol from pyrolysis of hydrogen

Abstract

The invention relates to a process for producing methanol by (a) pyrolyzing and hydrogenating a feed stream (I) containing light hydrocarbons and optionally carbon oxides and sulfur compounds into (al) a crude pyrolyzed gaseous product stream (III) containing hydrogen, residual methane and optionally carbon oxides and hydrogen sulfide and (ail) solid carbon (IV); (b) separating solid carbon (IV) from the crude pyrolysis gaseous product stream (III); (c) optionally separating hydrogen sulfide from the crude pyrolysis gaseous product stream (III), producing (ci) a crude pyrolysis gaseous product stream (VI) containing hydrogen, residual methane and optionally carbon oxides and (cii) optionally adsorbed sulfur (V); (d) converting the crude pyrolysis gaseous product stream (III) or (VI) with a carbon oxide (II) to crude methanol (VII); (e) separating an uncondensed gas stream, i.e. A purge gas (XII), from the crude methanol (VII), thereby obtaining a methanol stream (VIII); (f) purifying the methanol stream (VIII); (g) separating hydrogen (XIV) from the purge gas (XII); (h) recycling the hydrogen (XIV) to the methanol synthesis unit of stage (d).

Description

Method for preparing methanol from pyrolysis hydrogen

[0001] This invention relates to a method for preparing methanol by means of the following manner

[0002] (a) Pyrolyze and hydrogenate a feed stream (I) containing light hydrocarbons and optional carbon oxides and sulfur compounds into (ai) a crude pyrolysis gaseous product stream (III) and (aii) solid carbon (IV) containing hydrogen, residual methane and optional carbon oxides and hydrogen sulfide.

[0003] (b) Separating solid carbon (IV) from the crude pyrolysis gaseous product stream (III);

[0004] (c) Optionally, hydrogen sulfide is separated from the crude pyrolysis gaseous product stream (III) to produce (ci) a crude pyrolysis gaseous product stream (VI) containing hydrogen, residual methane and optional carbon oxides and (cii) optional adsorbed sulfur (V);

[0005] (d) The crude (or raw) pyrolysis gaseous product stream (III) or (VI) is converted with carbon oxides (II) into crude methanol (VII);

[0006] (e) The uncondensed gas stream, i.e. the purge gas (XII), is separated from the crude methanol (VII) to obtain a methanol stream (VIII);

[0007] (f) Purify the methanol stream (VIII);

[0008] (g) Separating hydrogen (XIV) from the purge gas (XII);

[0009] (h) The hydrogen (XIV) is recycled to the methanol synthesis unit in stage (d).

[0010] Methanol (MeOH), produced with a low product carbon footprint (PCF), is needed as an important synthetic feedstock for the chemical industry, for example, in the synthesis of formaldehyde, acetic acid, methyl tert-butyl ether, dimethyl terephthalate, methyl methacrylate, and methylamine, as an important solvent and, in particular, as an alternative fuel and energy carrier in the challenge of reducing greenhouse gas emissions such as CO2.

[0011] To date, on an industrial scale, methanol has been produced from syngas in a reactor in the presence of a methanol synthesis catalyst. Syngas primarily contains hydrogen and carbon monoxide and / or carbon dioxide, water, and inert gases such as methane, nitrogen, or argon.

[0012] Hydrogen feedstocks can, in principle, come from a variety of different sources. Examples include hydrogen supplies from other production facilities where hydrogen is formed as a byproduct (e.g., from steam crackers or refining units, from syngas processing, from hydrocarbon cracking, or from water electrolysis).

[0013] With hydrogen gaining global attention as a key element of the energy transition, the demand for hydrogen, especially low-CO2 hydrogen, is expected to grow exponentially. Therefore, there is a strong need for resource-efficient and more effective methods to utilize hydrogen as a basic chemical feedstock (educt).

[0014] Syngas used in classic methanol synthesis is typically obtained from natural gas or other hydrocarbon-containing streams. Standard preparation processes include steam reforming, autothermal reforming, combinations thereof, or partial oxidation.

[0015] Syngas should be substantially free of metals, semi-metals, phosphorus, halogens, and sulfur compounds. Catalytic methanol processes are highly sensitive to sulfur impurities in the feedstock. Therefore, the feed gas needs to be pre-desulfurized before methanol synthesis. Desulfurization typically involves two steps: a) converting all sulfur-containing impurities to H2S via hydrogenation; b) removing H2S via gas scrubbing (e.g., via ZnO, CuZnO, Fe(OH)3, zeolite, MOF). In most chemical plants, pipeline natural gas is pre-desulfurized. These processing steps can be expensive and imply feedstock loss.

[0016] In hydrocarbon pyrolysis (primarily known as methane pyrolysis), hydrogen is obtained from methane, which typically originates from natural gas, synthetic methane, industrial waste gases (such as cracker exhaust), biogas / biomethane, or wastewater gas. However, unlike reforming, it does not produce gaseous carbon dioxide; instead, it produces solid, high-purity carbon as a byproduct. The simultaneous production of high-purity carbon has a positive impact on economic efficiency. Therefore, methane pyrolysis is considered a promising sustainable technology for future hydrogen production. However, to date, commercial methane pyrolysis processes are rare.

[0017] The general term methane pyrolysis encompasses a wide range of processes. Among the most well-known and advanced of these processes are: plasma pyrolysis, metal melting / metal salt melting, moving bed processes, fluidized bed catalytic processes, and partial combustion. These processes differ in the form of energy used (heat, electricity, etc.), process conditions (temperature, pressure, etc.), catalysts and / or auxiliary materials used, process flow, and technology readiness level (TRL).

[0018] US5767165 describes a method for producing methanol from natural gas, comprising the thermal decomposition of methane and a subsequent reaction of the resulting hydrogen with carbon dioxide in methanol synthesis. The heat required for the decomposition is provided by the combustion of natural gas or hydrogen. Details regarding the purification steps required for the natural or pyrolytic hydrogen are not given.

[0019] EP2684842 describes the production of syngas by the following steps: (i) a hydrocarbon decomposition step, wherein hydrocarbons are decomposed to produce hydrogen and nanocarbon, the crude pyrolysis gas is purified by pressure swing adsorption (PSA) and transferred to a syngas mixing device; (ii) a carbon dioxide reduction step, wherein some of the produced nanocarbon is reacted with carbon dioxide to produce carbon monoxide; and (iii) a mixing step, wherein the purified hydrogen and the produced carbon monoxide are mixed in a predetermined ratio to obtain syngas.

[0020] WO 2018 / 229729 also describes a combination of gasification and catalytic decomposition for the production of hydrogen and syngas from hydrocarbons. A gaseous C1-s hydrocarbon stream is contacted with a hydrocarbon decomposition catalyst under conditions suitable for producing a carbon-coated decomposition catalyst and a product stream containing at least 50 mol.% H2. In some embodiments, the product stream is passed through a gas separation unit to produce a product stream having 100 mol.% H2. The carbon-coated hydrocarbon decomposition catalyst is contacted with water under conditions sufficient to oxidize the carbon and produce a syngas stream and a regenerated hydrocarbon decomposition catalyst. The syngas stream is mixed with a hydrogen stream and optionally used for the production of methanol.

[0021] WO 2013 / 4391 and WO 2014 / 95661 describe methods for producing syngas by reacting natural gas, blast furnace gas, related gases, and / or biogas / biomethane and carbon dioxide in a carbon-containing solid bed in a reaction chamber to obtain a gaseous product stream containing hydrogen and carbon monoxide, wherein said bed is guided through the reaction chamber as a moving bed. Such syngas can be used as a feedstock for methanol production. No details are given regarding any purification steps for natural or pyrolytic hydrogen.

[0022] WO 91 / 05734 relates to a method for converting a carbonaceous feedstock into particulate carbon and methanol, the method comprising (i) hydropyrolysis of a carbonaceous material such as bituminous coal or lignite to obtain a methane-rich gas stream, (ii) methane pyrolysis of said stream to obtain a hydrogen-rich and carbon monoxide-rich stream, and (iii) methanol conversion of said stream. After condensing the crude methanol-rich stream, a residual gas stream, namely a purge gas, is obtained, containing 40% to 90% hydrogen, 0% to 40% carbon monoxide, 10% to 30% methane, 0% to 10% carbon dioxide, 0% to 3% methanol, and 0% to 15% water. A majority of said purge stream is recycled to hydropyrolysis and the remainder of said purge stream is removed to prevent the accumulation of inert components in the recycled stream. Optionally, said remainder may be burned as needed to provide additional heat energy.

[0023] Task

[0024] The objective of this invention is to find a resource-efficient and more efficient method for producing methanol. Another objective is to find a resource-efficient and more efficient methanol method, particularly regarding hydrogen. A further objective is to find a methanol method with lower costs than existing technologies, such as smaller reactors, apparatus, and devices. A further objective is to find a methanol method with a lower carbon footprint compared to existing technologies. A further objective is to improve existing methanol methods using hydrogen feedstock with a low carbon footprint.

[0025] This problem is solved by the present invention, which relates to a method for preparing methanol by:

[0026] (a) Pyrolyze and hydrogenate a feed stream (I) containing light hydrocarbons and optional carbon oxides and sulfur compounds into (ai) a crude pyrolysis gaseous product stream (III) and (aii) solid carbon (IV) containing hydrogen, residual methane and optional carbon oxides and hydrogen sulfide.

[0027] (b) Separating solid carbon (IV) from the crude pyrolysis gaseous product stream (III);

[0028] (c) Optionally, hydrogen sulfide is separated from the crude pyrolysis gaseous product stream (III) to produce (ci) a crude pyrolysis gaseous product stream (VI) containing hydrogen, residual methane and optional carbon oxides and (cii) optional adsorbed sulfur (V);

[0029] (d) The crude pyrolysis gaseous product stream (III) or (VI) is converted into crude methanol (VII) with carbon oxides (II);

[0030] (e) The uncondensed gas stream, i.e., the purge gas (XII), is separated from the crude methanol (VII); thereby obtaining a methanol stream (VIII);

[0031] (f) Purify the methanol stream (VIII);

[0032] (g) Separating hydrogen (XIV) from the purge gas (XII);

[0033] (h) The hydrogen (XIV) is recycled to the methanol synthesis unit in stage (d).

[0034] Phase a)

[0035] In stage (a), a feed stream (I) containing light hydrocarbons and optionally carbon oxides and sulfur compounds is fed into a methane pyrolysis unit, and is pyrolyzed and hydrogenated to (ai) a crude pyrolysis gaseous product stream (III) containing hydrogen, residual methane, and optionally carbon oxides and hydrogen sulfide, and (aii) solid carbon (IV). Preferably, the feed stream (I) containing light hydrocarbons, sulfur compounds, and optionally carbon oxides is fed into a methane pyrolysis unit, and is pyrolyzed and hydrogenated to (ai) a crude pyrolysis gaseous product stream (III) containing hydrogen, residual methane, hydrogen sulfide, and optionally carbon oxides, and (aii) solid carbon (IV).

[0036] Raw material feed flow

[0037] Feed streams (I) containing light hydrocarbons, preferably gaseous C2-C4 alkanes, and even more preferably methane, are preferably natural gas, related gases, industrial waste gases, and / or biogas / biomethane. Such feed streams typically contain light hydrocarbons such as methane, ethane, ethylene, propane, propylene, and butane, carbon monoxide and carbon dioxide, inert gases such as nitrogen, and sulfur components.

[0038] Depending on the gas reservoir, natural gas typically has the following composition: 60% to 99% Vol.-% methane, 1% to 15% Vol.-% C2-C4 alkanes, up to 20% Vol.-% sulfur, and up to 30% inert gases, especially nitrogen. Depending on the pipeline specifications, up to 20% Vol.-% hydrogen can be added to the natural gas.

[0039] The relevant gases typically include methane, ethane, ethylene, propane, propylene, and butane, and have the following composition: 75% to 85% methane by volume, 1% to 10% ethane by volume, 1% to 10% propane by volume, 1% to 10% butane by volume, 0.1% to 5% nitrogen by volume, 0.1% to 10% sulfur compounds by volume, and 0% to 1% carbon dioxide by volume.

[0040] Biogas / biomethane typically has the following composition: 50% to 75% methane by volume, 25% to 50% CO2 by volume, 0% to 10% sulfur compounds by volume, and 0% to 10% N2 by volume.

[0041] Depending on the composition of the feed stream (I), additional carbon oxides (II) may be required for methanol synthesis. The amount of carbon oxides (II) to be fed is determined by the mass balance of the stream supplied to and removed from the methanol synthesis unit (C). The additional carbon oxide stream (II) may preferably be mixed with the feed stream (I) and / or fed separately into the methane pyrolysis unit (A).

[0042] Using carbon dioxide and hydrogen instead of syngas has the following advantages: Carbon dioxide is generally readily available as a byproduct or waste. For example, carbon dioxide can be readily obtained from sources such as fossil-based power plants, steelmaking, cement industries, chemical production complexes, or direct air capture. When using biogas / biomethane as a feedstock and carbon dioxide as a carbon source, the methanol process can be converted to CO2 neutral or even negative CO2.

[0043] Hydrocarbon pyrolysis processes, particularly non-metallic catalytic methane pyrolysis, do not require pre-desulfurization. All sulfur-containing impurities are converted / hydrogenated to hydrogen sulfide during the pyrolysis reaction without affecting the methane conversion rate. Hydrogen sulfide can preferably be removed via a one-step gas scrubbing step after the methane pyrolysis unit.

[0044] Therefore, the method of the present invention does not require the common two-step desulfurization; the first desulfurization step of hydrogenation can be included in the pyrolysis step.

[0045] Methane pyrolysis technology

[0046] In the methane pyrolysis stage (a), methane is decomposed into solid carbon and hydrogen. The methane pyrolysis process is also known as methane decomposition. Pyrolysis can be carried out in various ways known to those skilled in the art: catalytic or thermal, and by inputting heat via plasma, resistance heating, liquid metal processes, or autothermal processes (see, for example, N. Muradov and T. Veziroglu: “Green” path from fossil-based to hydrogen economy: An overview of carbon-neutral technologies, International Journal Hydrogen Energy 33 (2008) 6804-6839; HFAbbas and WMA Wan Daud: Hydrogen production by methane decomposition: Areview, International Journal Hydrogen Energy 35 (2010) 1160-1190); R. Dagle et al.: An Overview of Natural Gas Conversion Technolgies for Co-Production of Hydrogen and Value-Added Solid Carbon Products, Report by Report from Argonne National Laboratory and Pacific Northwest National Laboratory (ANL-17 / 11, PNNL-26726), November 2017.

[0047] Therefore, the general term methane pyrolysis encompasses a wide range of processes. Among the most well-known and advanced of these processes are plasma pyrolysis, metal melting / metal salt melting, moving bed processes, and fluidized and fixed bed catalytic processes. These processes differ in the form of energy used (heat, electricity, etc.), process conditions (temperature, pressure, etc.), catalysts and / or auxiliary materials used, and process flow.

[0048] The type of solid carbon produced in methane pyrolysis depends on the reaction conditions, reactor, and heating technology. An example is...

[0049] - Carbon black from plasma processing

[0050] - Carbon powder from liquid metal processing

[0051] - Particulate carbon from pyrolysis in stationary, moving, or fluidized bed reactors.

[0052] Plasma pyrolysis

[0053] For plasma pyrolysis (see, for example, WO 2015116797, WO 2015116800), plasma >3000°C is generated and mixed with ethane-rich natural gas or ethane-rich waste gas, which is then pyrolyzed. The gas mixture exits the reactor at a temperature between 1500°C and 2000°C. The reaction produces solid carbon in the form of carbon black, which is discharged from the reactor along with the gas and then separated. Various techniques, such as electric arc, microwave, and gas plasma technologies, can be used for this purpose.

[0054] Partial combustion process or pulsed reaction process

[0055] For partial or pulsed combustion processes, the heat for the pyrolysis reaction is supplied via pulsed combustion (see, for example, WO 2020118417 and US 20220185664). The combustible gas (containing hydrocarbons and an oxidant) is premixed in a mixing chamber before the feedstock (containing hydrocarbons) is separated into hydrogen and solid carbon in the combustion chamber. The reaction occurs in the combustion chamber when the gas mixture is heated to 1350 K and reaches a pressure exceeding 20 bar. The products leaving the reactor are separated into gaseous and solid carbon for further processing.

[0056] Molten metal / molten metal salt

[0057] Pyrolysis processes using molten metal or molten metal salts (see, for example, WO 2020161192, WO2021183959) utilize heat from the melt for pyrolysis. Alternatively, metals with catalytic effects can be selected, allowing pyrolysis to occur at relatively low temperatures of approximately 800°C–1200°C. Ethane-rich natural gas or ethane-rich waste gas is fed into the molten metal; bubbles formed in this process rise upwards in the reactor, thereby decomposing hydrocarbons and primarily forming methane, hydrogen, and solid carbon. Depending on the process and metal used, carbon floats on the melt and is either skimmed off or leaves the reactor with the gas stream and is then separated. In both cases, the carbon is characterized by a very small particle size and bulk density. Due to the adhesion of carbon particles to the melt, carbon purification may be necessary for some processes and applications.

[0058] Catalytic process

[0059] Catalysts can also be used to lower high reaction temperatures (see, for example, WO 2011029144, WO2016154666). For hydrocarbon pyrolysis, a very cost-effective alternative is to use iron oxide catalysts. Reaction temperatures of approximately 700°C to 1000°C can be achieved. To achieve the best possible heat and mass transfer, the reaction occurs, for example, in a fluidized bed, where the catalyst acts as the fluidizing material. Hydrocarbons decompose on the catalytic surface.

[0060] Fixed bed or moving bed process

[0061] The hydrocarbon pyrolysis in stage (a) is carried out in a moving bed or fixed bed reactor—wherein the bed preferably contains carbon materials, metals, ceramics, and mixtures thereof as a substrate—preferably at a temperature ranging from 500°C to 2000°C, more preferably from 1000°C to 1600°C, and even more preferably from 1200°C to 1500°C, and at a pressure ranging from 1 bar to 100 bar, preferably from 5 bar to 50 bar.

[0062] Pyrolysis can be carried out in a fixed bed manner, preferably in a circulating operation mode (preferably including production and regeneration modes as described, for example, in WO 2018 / 083002), or in a moving bed (as described, for example, in US 2982622, WO 2019 / 145279 and WO 2020 / 200522).

[0063] The pyrolysis process is preferably carried out electrically, and even more preferably by resistance heating (Joule heating) of the substrate material (as described, for example, in US 2982622, WO 2019 / 145279 and WO 2020 / 200522).

[0064] Preferably, the pyrolysis process is located at an existing chemical production site, especially an existing methanol production site, or at a gas well.

[0065] Preferred process conditions: moving bed

[0066] Preferably, the substrate is guided through the reaction chamber in the form of a moving bed, wherein methane and / or other light hydrocarbons are advantageously passed through the substrate in a countercurrent manner.

[0067] For this purpose, the reaction chamber is preferably rationally designed as a vertical reactor, meaning that the movement of the moving bed is gravity-driven. The flow occurs advantageously and homogeneously through the moving bed (see, for example, WO 2013 / 004398, WO 2019 / 145279 and WO 2020 / 200522). Methane and / or other light hydrocarbons are preferably introduced via the bottom of the reactor, preferably at a temperature of 10°C to 200°C. The substrate is preferably introduced via the top of the reactor, preferably at a temperature of 10°C to 200°C. Hydrogen preferably exits via the top of the reactor, preferably at a temperature of 10°C to 200°C. The produced particulate pyrolytic carbon is preferably deposited on the solid substrate and removed via the bottom of the reactor along with the substrate, preferably at a temperature of 10°C to 200°C.

[0068] The discharged carbon is preferably at least partially recycled and reintroduced into the reactor, using it as the substrate for the moving bed. As a result, a continuous moving bed process is achieved.

[0069] The flow rate of the substrate is advantageously in the range of 0.005 to 0.5 cm / s. The flow rate of the gas stream is advantageously in the range of 0.025 to 2 m / s.

[0070] The residence time of the gas in the reactor is advantageously between 0.5 and 50 s, preferably between 1 and 20 s. The residence time of the substrate is preferably between 0.5 and 15 hours, more preferably between 1 and 10 hours, and even more preferably between 2 and 8 hours.

[0071] substrate

[0072] The substrate can be a stationary carrier / substrate (pre-installed component) in the reactor or a granular carrier / substrate material. A preferred substrate is a carbon-containing substrate, such as pyrolytic carbon itself. The preferred substrate particle size is in the range of 0.1 to 10 mm, preferably 0.3 to 8 mm.

[0073] Preferably, the substrate is a carbonaceous material as the macroscopic structure, wherein the porosity of the carbonaceous material is in the range of 30 to 70 vol.-%, and relative to the total mass of the solid carbonaceous material, the carbonaceous material contains 98 wt.-% to 100 wt.-%, preferably 99 wt.-% to 100 wt.-%, even more preferably 99.5 wt.-% to 100 wt.-%, and 0 to 2 wt.-%, preferably 0 to 1 wt.-%, even more preferably 0 to 0.5 wt.-%, of alkaline earth metals, transition metals, and metalloids (see WO 2023 / 057242).

[0074] The BET surface area of ​​the substrate is preferably between 0.1 and 100 m² / g, more preferably between 0.1 and 50 m² / g, and particularly between 0.1 and 30 m² / g.

[0075] Preferably, the true density of the substrate is in the range of 1.5 to 2.5 g / cc (true density in xylene, ISO 8004). Preferably, the bulk density of the substrate is in the range of 0.5 to 1.5 g / cc.

[0076] Particulate pyrolytic carbon (IV)

[0077] Typically, the true density of particulate pyrolytic carbon (IV) produced via the methane pyrolysis process of stage (a) is in the range of 1.5 to 2.5 g / cc, preferably 2.0 to 2.3 g / cc (true density in xylene, ISO 8004). Typically, the bulk density of particulate pyrolytic carbon (IV) is in the range of 0.5 to 1.5 g / cc, more preferably 0.7 to 1.3 g / cc.

[0078] Typically, the ash content of the particulate pyrolytic carbon (IV) composition is in the range of 0.001 to 1 wt% of the composition, preferably 0.01 to 0.2 wt%.

[0079] Typically, the carbon content of the particulate pyrolytic carbon (IV) composition is in the range of 98 to 100 wt%, more preferably 99.5 to 100 wt%, even more preferably 99.75 to 100 wt%, even more preferably 99.9 to 100 wt%.

[0080] Typically, impurities in particulate pyrolytic carbon (IV) are: S in the range of 0 to 0.5 wt%, more preferably 0 to 0.1 wt%; Fe in the range of 0 to 1000 ppm, preferably 0 to 500 ppm; Ni in the range of 0 to 250 ppm, preferably 0 to 100 ppm; V in the range of 0 to 250 ppm, more preferably 0 to 100 ppm; and Na in the range of 0 to 200 ppm, preferably 0 to 100 ppm. Oxygen is in the range of 0 to 100 ppm, preferably below the detection limit.

[0081] Typically, 95% by weight, preferably 98% by weight, of the particulate pyrolytic carbon (IV) is unfunctionalized, where carbon functionalization refers to the reaction in which carbon-carbon bonds are broken and replaced by carbon-X bonds (where X is typically hydrogen, oxygen, sulfur, phosphorus, nitrogen, halogen and / or metal).

[0082] Typically, the cation exchange capacity (CEC) of particulate pyrolytic carbon (IV) is about 0.01 to 1.5 cmol / kg, preferably 0.025 to 0.75 cmol / kg.

[0083] Typically, the particle size of particulate pyrolytic carbon (IV) produced directly from the pyrolysis of gaseous hydrocarbons (without any agglomeration step) is in the range of 0.3 mm (d10) to 8 mm (d90), preferably 0.5 mm (d10) to 5 mm (d90), and more preferably 1 mm (d10) to 4 mm (d90).

[0084] Typically, the porosity of particulate pyrolytic carbon (IV) is between 0% and 15%, preferably between 0.2% and 10%, and most preferably between 0.2% and 5% (Hg porosity determination method, DIN 66133).

[0085] Typically, the specific surface area of ​​particulate pyrolytic carbon (IV), as measured by the Hg porosity determination method (DIN66133), is in the range of 0.001 to 10 m2 / g, preferably 0.001 to 5 m2 / g, and even more preferably 0.05 to 2 m2 / g.

[0086] Preferred reactor

[0087] Preferably, the reactor for the methane pyrolysis unit (A) for carrying out methane pyrolysis—where hydrogen (III) and particulate pyrolysis carbon (IV) are produced from hydrocarbons, preferably methane—comprises:

[0088] -The reactor surrounding the interior of the reactor

[0089] The reactor is configured to provide a gravity-driven moving bed within a reaction zone, the moving bed comprising a plurality of solid substrates. The reactor is also configured to guide methane into the reaction zone. To heat the methane, the reactor is configured to heat the solid substrates in the reaction zone by generating an electric current in the solid substrates between a pair of first and second electrodes, such that heat is transferred from the solid substrates to the methane.

[0090] - Methane in the reaction zone can be heated to the reaction temperature to produce hydrogen and particulate pyrolytic carbon.

[0091] The reactor further includes a first thermal integration zone in which heat from hydrogen produced in the reaction zone can be transferred to a solid substrate in the reaction zone via a gravity-driven moving bed. The reactor also includes a second thermal integration zone in which heat from the solid substrate of the gravity-driven moving bed in the reaction zone can be transferred to methane for preheating. The reaction zone is arranged between the pair of first and second electrodes, with the first thermal integration zone positioned above the first electrode and the second thermal integration zone positioned below the second electrode.

[0092] Preferably, the electrode comprises or is formed of a mesh.

[0093] Preferred moving bed method

[0094] Preferably, the moving bed technology is used for the methane pyrolysis in stage (a), the moving bed technology comprising:

[0095] - Multiple solid substrates (XVIII) are guided into the first thermal integration zone and from there into the reaction zone.

[0096] -Heating the solid substrate in the reaction zone

[0097] - The solid substrate is guided from the reaction zone to the second thermal integration zone and then removed from the second thermal integration zone.

[0098] Methane (I) is introduced into a second thermally integrated zone and from there into a reaction zone, wherein the methane in the second thermally integrated zone is heated by a solid substrate from the reaction zone, wherein the solid substrate is cooled, and wherein the methane is brought into contact with the heated solid substrate in the reaction zone, wherein heat from the heated solid substrate is transferred to the methane to heat the methane in the reaction zone, wherein the methane is decomposed into hydrogen and particulate pyrolytic carbon in the reaction zone.

[0099] - The produced hydrogen is guided from the reaction zone to the first thermal integration zone, where the solid substrate in the first thermal integration zone is preheated using the hydrogen from the reaction zone, where the hydrogen is cooled, and where

[0100] - Remove hydrogen (III) from the first thermal integration zone

[0101] - The produced granular pyrolytic carbon (IV) is deposited on a solid substrate and removed together with the substrate.

[0102] - The removed substrate is preferably at least partially processed, recycled, and introduced into the reactor.

[0103] - The extracted hydrogen gas is preferably at least partially recycled and introduced into the reactor.

[0104] Stage (b): Separation of solid carbon (IV)

[0105] The separation of solid carbon (IV) depends on the pyrolysis technique chosen and is known to those skilled in the art.

[0106] As described above, for example in plasma pyrolysis, solid carbon in the form of carbon black is discharged from the reactor along with gas and then separated, for example, by a cyclone separator. The solid carbon can be post-treated, such as agglomerated. Depending on the process and metal used in molten metal pyrolysis, carbon floats on the melt and is skimmed off or leaves the reactor with the gas stream, and is then separated (e.g., by a filter / cyclone separator). Additionally, purification steps to remove residual metals from the carbon may be required, such as washing or evaporation. In catalytic pyrolysis technologies, as well as fixed-bed and moving-bed technologies, solid carbon is deposited on the surface of the catalyst and / or support / substrate and leaves the reactor via the catalyst and / or support / substrate.

[0107] Crude pyrolysis gaseous product stream (III)

[0108] Depending on the hydrocarbon feed used, the crude pyrolysis gaseous product stream contains hydrogen, residual methane, and optionally carbon oxides and hydrogen sulfide. Typically, the crude pyrolysis gaseous product stream has the following composition: 10 vol.% to 98 vol.% hydrogen, preferably 20 to 95 vol.% hydrogen, most preferably 50 to 95 vol.% hydrogen, 0.1 to 30 vol.% methane, up to 10 vol.% hydrogen sulfide, and up to 30 vol.% inert gas, especially nitrogen. If biogas / biomethane is used as the hydrocarbon feed or carbon oxides are added to the hydrocarbon feed, the crude pyrolysis gaseous product stream also contains carbon oxides, preferably 20 to 50 vol.% carbon oxides.

[0109] Stage c: Separation of gaseous hydrogen sulfide

[0110] Hydrogen sulfide can preferably be removed from the crude gaseous product stream via gas cleaning / washing (e.g., via ZnO, CuZnO, Fe(OH)3, zeolite, MOF, as known in the art). Typical process conditions for gas cleaning are 60°C to 180°C and 1 bar to 100 bar.

[0111] If a gas compressor is required prior to methanol synthesis, it is preferable to embed the gas cleaning process within the compressor unit. Preferably, the inlet temperature of the absorber bed can be provided by the heat of compression between compressor stages.

[0112] Stage d: Convert the crude gaseous product stream (III) or (VI) into a crude methanol stream (VII).

[0113] The crude pyrolysis gaseous product stream (III) or (VI) is mixed with recycled hydrogen (XIV) (described further below in conjunction with stage h) and fed into the methanol synthesis unit (C).

[0114] Alternatively, other carbon oxide streams (II) may be added to the crude pyrolysis gaseous product stream (VI). The amount of carbon oxide stream (II) to be added is determined by the mass balance of the streams supplied to the methanol synthesis unit (C) and removed from the methanol synthesis unit.

[0115] The conversion of carbon oxides and hydrogen to methanol is preferably carried out at a temperature of 150°C to 300°C and a pressure of 3 to 10 MPa in the presence of a methanol synthesis catalyst (see, for example, Ullmann's Encyclopedia of Industrial Chemistry, "Methanol" chapter, 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany, or WO 2021 / 148262, especially pp. 8 to 10).

[0116] The complex reaction mixture (VII), i.e. the crude methanol stream, typically contains methanol, water, dimethyl ether, carbon monoxide, carbon dioxide, hydrogen, and methane.

[0117] Stage e: Separating the uncondensed gas stream, i.e., the purge gas, from the crude methanol.

[0118] To separate methanol (VIII), the crude methanol stream is typically first condensed in a methanol separation unit (D) to produce a purge feed stream (XII) and a degassed methanol stream (VIII).

[0119] The uncondensed gas stream (XII) contains, in particular, unconverted carbon dioxide, carbon monoxide and hydrogen feedstock, as well as methane.

[0120] Preferably, a portion of the uncondensed gas stream (XII) is recycled as recirculated gas (XV) back to the methanol synthesis unit. This recycling increases the utilization of feedstocks containing carbon oxides and hydrogen.

[0121] Stage f: Purifying the methanol

[0122] In stage (f) of the method of the present invention, the degassed methanol stream (VIII) obtained in stage (e) is separated by distillation in the methanol purification unit (E) into a low-boiling stream (XI) containing carbon dioxide and dimethyl ether, methanol (IX) and a high-boiling stream (X), the high-boiling stream containing water and other components with boiling points higher than methanol, such as acetic acid, higher alcohols, higher esters, higher ethers or alkanes.

[0123] Stage g: Separating hydrogen from the purge gas

[0124] In stage (g), hydrogen (XIV) is separated from the purge gas (XII) in the hydrogen recovery unit (F).

[0125] In principle, any device suitable for separating hydrogen from a gas stream containing carbon dioxide, carbon monoxide, hydrogen, and methane can be used to remove hydrogen from the purge gas (XII). Relevant devices are common knowledge to those skilled in the art, such as pressure swing adsorption or permeation.

[0126] Typically, the separated hydrogen stream (XIV) usually has a relatively high purity. Preferred pressure swing adsorption provides hydrogen that is typically separated with a purity of 90% to 100 vol.-%, preferably ≥ 95 vol.-%, more preferably ≥ 99 vol.-%, and most preferably ≥ 99.5 vol.-%.

[0127] Optional: Combustion and CO2 recovery (see Figures 3 through 6)

[0128] The exhaust gas stream (XIII) from the hydrogen recovery unit (F) is preferably fed into the combustion unit (G) and combusted therein with an oxygen-containing gas (XX) having a preferred oxygen content of 30% to 100 vol.% to form a carbon dioxide-containing flue gas (XVI).

[0129] Since the valuable methane and dimethyl ether components in the exhaust gas stream (XIII), along with other carbonaceous byproducts present therein, cannot be directly used as reactants in methanol synthesis in their current form, they must first be chemically converted to a suitable form. Therefore, it is preferable to burn these components in the combustion unit (G) to form carbon dioxide-containing flue gas (XVI). This conversion to carbon dioxide also allows the valuable components methane, dimethyl ether, and other carbonaceous byproducts to be reused as reactants in methanol synthesis.

[0130] Typically, the carbon dioxide-containing flue gas (XVI) discharged from the combustion unit (G) has a carbon dioxide content of 25% to 90 vol.-%, preferably ≥ 70 vol.-%, and more preferably ≤ 80 vol.-%.

[0131] Preferably, the combustion unit (G) includes a condenser in addition to the combustion chamber, in which water is condensed from the combustion gases and guided away as a stream (XXI).

[0132] Preferably, all three waste gas streams, namely waste gas (XI) from the methanol purification unit (E), waste gas (XIII) from the hydrogen recovery unit (F), and waste gas (XIX) from the carbon treatment unit (J), are directed to the combustion unit (G).

[0133] Then, preferably in a carbon dioxide recovery unit (H), a carbon dioxide-rich stream (XVII) is separated from the carbon dioxide-containing flue gas (XVI) to form an exhaust gas stream (XXII), preferably containing condensate. The corresponding apparatus and methods are known to those skilled in the art. A general overview of possible apparatus and methods can be found, for example, in the following literature: Ullmann's Encyclopedia of Industrial Chemistry, "Carbon Dioxide" chapter, Section 13.3 "CCS-related Separation Technologies", 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany.

[0134] Preferably, the carbon dioxide-rich stream (XVII) separated in the carbon dioxide recovery unit (H) is then recycled to the methanol synthesis unit (C) of stage (d), for example by introducing the separated carbon dioxide-rich stream (XVII) into the crude pyrolysis gaseous product stream (VI).

[0135] Stage h: The hydrogen (XIV) is recycled to the methanol synthesis unit (C) in stage (d).

[0136] The separated hydrogen stream (XIV) from the hydrogen recovery unit (F) is recycled to the methanol synthesis unit (C) of stage (d), for example by introducing the separated hydrogen stream (XIV) into the crude pyrolysis gaseous product stream (VI).

[0137] Uses of methanol

[0138] The methanol obtained can be used for fuel applications such as the production of MTBE / TAME, gasoline blending, dimethyl ether production, and biodiesel production; for the production of formaldehyde, acetic acid, olefins, sodium methoxide, methylated products (such as dimethylphenol); and for the production of dimethyl terephthalate and methanethiol.

[0139] The formaldehyde obtained from the methanol of the present invention can be further used, for example, to produce polyoxymethylene, butanediol, methylene diphenyl diisocyanate, neopentyl glycol, methacrylic acid, phenol-formaldehyde resin, urea condensation resin, melamine resin, and acetone resin.

[0140] The acetic acid obtained from the methanol of the present invention can be further used, for example, to produce chloroacetic acid, acetate, methyl isopropyl ketone, and acetic anhydride.

[0141] The methanethiol obtained from the methanol of the present invention can be further used, for example, to produce methyl mercaptopropionaldehyde, dimethyl disulfide, and methanesulfonic acid.

[0142] Advantages of the present invention

[0143] The advantages of this invention are reduced H2 demand for methanol synthesis, resulting in a resource-saving and more efficient methanol process. Additionally, the size of the hydrogen recovery unit (F) can be reduced, leading to lower OPEX and CAPEX costs. Furthermore, desulfurization can be integrated into the combined methane pyrolysis and methanol process, eliminating the need for hydrogenation and desulfurization steps on the hydrocarbon feedstock to methane pyrolysis. A CO2-free process is possible through an additional combustion step; correspondingly, the process is also carbon-negative by using biogas / biomethane.

[0144] Figure 1 shows a block diagram of a general embodiment of the method of the present invention.

[0145] Figure 2 shows a block diagram of a general embodiment in which a portion of the uncondensed gas stream (XII) is recycled as recirculated gas (XV) to the methanol synthesis unit.

[0146] Figure 2a illustrates Examples 1 and 3 of the present invention as described in the Examples section.

[0147] Figure 3 shows a block diagram of a general embodiment in which exhaust gas (XIII) from a hydrogen recovery unit (F) is combusted to form a carbon dioxide-containing flue gas (XVI), and a carbon dioxide-rich stream (XVII) is separated from the carbon dioxide-containing flue gas (XVI) in a carbon dioxide recovery unit (H) and recycled to a methanol synthesis unit (C).

[0148] Figure 3a illustrates Examples 2 and 4 of the present invention as described in the Examples section.

[0149] Figure 4 shows comparative examples 1 and 2 as described in the Examples section.

[0150] Figure 5 shows a block diagram of a general embodiment in which a portion of the solid carbon is recycled to the pyrolysis unit.

[0151] Figure 6 shows a block diagram of a general embodiment in which all three exhaust gas streams, namely exhaust gas (XI) from the methanol purification unit (E), exhaust gas (XIII) from the hydrogen recovery unit (F) and exhaust gas (XIX) from the carbon treatment unit (J), are directed to the combustion unit (G).

[0152] The markings in the attached diagram have the following meanings:

[0153] A hydrocarbon pyrolysis unit

[0154] B Desulfurization Unit

[0155] C Methanol Synthesis Unit

[0156] D Methanol Separation Unit

[0157] E Methanol Purification Unit

[0158] F Hydrogen recovery unit

[0159] G Combustion Unit

[0160] H Carbon Oxide Recycling Unit

[0161] J Carbon Processing Unit

[0162] I contains hydrocarbon stream

[0163] II. Carbon oxide-containing flow

[0164] III. Crude Pyrolysis Gaseous Product Stream

[0165] IV. Solid Carbon

[0166] V sulfur

[0167] VI. Crude pyrolysis gaseous product stream and makeup gas stream

[0168] VII. Crude Methanol Flow

[0169] VIII Degassed Methanol Flow.

[0170] IX Methanol

[0171] X water and high-boiling-point logistics

[0172] XI waste gas stream, low-boiling stream from methanol distillation

[0173] XII contains a purge gas stream of carbon dioxide, carbon monoxide, hydrogen, and methane.

[0174] XIII is the exhaust gas stream from hydrogen recovery.

[0175] XIV comes from the recycled hydrogen stream.

[0176] XV containing carbon oxides flow

[0177] XVI contains a recirculated gas stream of carbon dioxide, carbon monoxide, hydrogen, and methane.

[0178] XVII contains a recirculated gas stream rich in carbon dioxide.

[0179] XVIII Carbon Support / Substrate Recycling

[0180] XIX Carbon Treatment of Waste Gas

[0181] XX oxygen-containing gas

[0182] XXI water flow from the combustion unit, including the condenser

[0183] XXII Exhaust gas flow from the carbon dioxide recovery unit

[0184] Process Description

[0185] The process conditions for a single unit are given in the examples.

[0186] Figure 2 / Figure 2a (Example of the present invention):

[0187] Natural gas (I) is fed into a methane pyrolysis unit (A) and pyrolyzed into a crude H2 stream (III) and solid carbon (IV). The crude H2 stream (III) from the methane pyrolysis unit (A) is then hydrogenated and desulfurized in a desulfurization unit (B). Preferably, the desulfurization unit (B) is located between two compressor stages of the compressor required to achieve the desired pressure for methanol synthesis. The inlet temperature of the reactor in the desulfurization unit is regulated at the outlet of the compressor stage and the fixed-bed catalytic absorber. In the reactor, all double and triple bond components are hydrogenated to alkanes, and H2S is absorbed in the copper phase of the catalytic absorber material. At the reactor outlet, the inlet temperature of the next compressor stage is regulated. Existing methanol synthesis loops operate with a water-cooled fixed-bed reactor (C) and a recirculated gas (XV).

[0188] The crude methanol-water mixture (VII) is separated in the crude methanol separation section (VIII) by cooling and condensation. The vapor phase consists of the recirculated gas stream (XV) and the purge gas stream (XII).

[0189] To maintain the ratio of makeup gas (VI) to recycle gas (XV), and thus the GHSV (gas hourly space velocity) and inert component concentration on the methanol synthesis catalyst, the synthesis loop is operated with a purge gas stream (XII). H2 is recovered from this purge gas stream (XII) via a hydrogen recovery section (F). The hydrogen recovery section (F) can be, for example, a pressure swing absorption unit, a membrane process, or a cold box. The recovered H2 is then fed back into the methanol synthesis loop.

[0190] The make-up gas stream (VI) is a mixture of crude H2 from the methane pyrolysis (A) and desulfurization section (B), recovered H2 from the hydrogen recovery unit (F), CO, and / or CO2 (II). This make-up gas stream (VI) is the feed stream for the methanol synthesis loop before being mixed with the recirculated gas stream (XV).

[0191] In the existing methanol purification section (E), the crude methanol-water mixture is depressurized from the methanol synthesis loop pressure to a lower 10 bar (absolute pressure) and fractionated into a waste gas stream (XI), a pure methanol stream (IX), and a water and high-boiling-point stream (X).

[0192] Figure 3 / Figure 3a (Example of the invention, concept with no CO2 emissions)

[0193] Natural gas (I) is fed into a methane pyrolysis unit (A) and pyrolyzed into a crude H2 stream (III) and solid carbon (IV). The crude H2 stream (III) from the methane pyrolysis unit (A) is hydrogenated and desulfurized in a desulfurization unit (B). Preferably, the desulfurization unit (B) is located between two compressor stages of the compressor required to achieve the desired pressure for methanol synthesis. The inlet temperature of the reactor in the desulfurization unit is regulated at the outlet of the compressor stage and the fixed-bed catalytic absorber. In the reactor, all double and triple bond components are hydrogenated to alkanes, and H2S is absorbed in the copper phase of the catalytic absorber material. At the outlet of the reactor, the inlet temperature of the next compressor stage is regulated. The prior art methanol synthesis loop operates with a water-cooled fixed-bed reactor (C) and a recirculated gas (XV).

[0194] The crude methanol-water mixture (VII) is separated in the crude methanol separation section (VIII) by cooling and condensation. The vapor phase consists of the recirculated gas stream (XV) and the purge gas stream (XII).

[0195] To maintain the ratio of makeup gas (VI) to recycle gas (XV), and thus the concentrations of GHSV and inert components on the methanol synthesis catalyst, the synthesis loop is operated with a purge gas stream (XII). H2 is recovered from this purge gas stream (XII) via a hydrogen recovery section (F). The hydrogen recovery section (F) can be, for example, a pressure swing absorption unit, a membrane process, or a cold box. The recovered H2 is then fed back into the methanol synthesis loop.

[0196] In the existing methanol purification section (E), the crude methanol-water mixture is depressurized from the methanol synthesis loop pressure to a lower 10 bar (absolute pressure) and fractionated into a waste gas stream (XI), a pure methanol stream (IX), and a water and high-boiling-point stream (X).

[0197] The exhaust gas stream (XIII) from the hydrogen recovery section (F) is mixed with the exhaust gas stream (XI) from the methanol purification section (E) and then sent to the combustion (oxygen fuel) section (G).

[0198] In the combustion (oxygen fuel) (G) section, the combined exhaust gas is burned into CO2-rich flue gas using pure O2.

[0199] In the CO2 recovery unit (H), CO2 is separated from the flue gas (XVI) and recycled back into the methanol synthesis loop. The exhaust gas (XXII) is released into the atmosphere and contains inert components such as N2.

[0200] The supplementary gas stream (VI) is a mixture of crude H2 from methane pyrolysis (A) after the desulfurization section (B), recovered H2 and CO from the hydrogen recovery unit (F), and recycled CO2 (XVII) from the CO2 recovery unit (H). This supplementary gas stream (VI) is the feed stream of the methanol synthesis loop before it is mixed with the recycled gas stream (XV).

[0201] Figure 4 (Comparative Examples)

[0202] The first process step is the pre-desulfurization (B) of natural gas (I). In a hydrogenation reactor, all double and triple bond components are hydrogenated to alkanes using catalysts such as CoMo or NiMo on Al2O3, and the sulfur-containing components are hydrogenated to H2S. The generated H2S is absorbed onto ZnO absorber material. The desulfurized natural gas (Ia) is fed into a methane pyrolysis unit (A) and pyrolyzed into a crude H2 stream (III') and solid carbon (IV). The crude H2 stream (III') is purified in a hydrogen recovery section (F). The hydrogen recovery section (F) can be, for example, a pressure swing absorption unit, a membrane process, or a cold box.

[0203] The feed stream for the methanol unit is a makeup gas stream (VI), which is a mixture of crude H2 stream (III') and CO and / or CO2 (II). This makeup gas stream (VI) is then mixed with a recirculated gas stream (XV).

[0204] Existing methanol synthesis loops operate with a water-cooled fixed-bed reactor (C) and a recirculated gas (XV).

[0205] The crude methanol-water mixture is separated in the crude methanol separation section (VIII) by cooling and condensation. The vapor phase consists of the recirculated gas stream (XV) and the purge gas stream (XII).

[0206] In order to maintain the ratio of makeup gas (VI) to recirculated gas (XV), and thus maintain the GHSV and inert component concentrations on the methanol synthesis catalyst, the synthesis loop is operated with the minimum purge gas flow (XII).

[0207] In the existing methanol purification section (E), the crude methanol-water mixture is depressurized from the methanol synthesis loop pressure to a lower 10 bar (absolute pressure) and fractionated into a waste gas stream (XI), a pure methanol stream (IX), and a water and high-boiling-point stream (X).

[0208] Example:

[0209] The ASPEN Plus™ V11 simulation software was used in combination with a kinetic model to simulate a method for producing methanol from pyrolysis of hydrogen, CO, and CO2, in order to calculate the conversion rates of CO and CO2 in the methanol synthesis reactor.

[0210] The general conditions for methane pyrolysis are shown in Table 1:

[0211]

[0212] For the examples and comparative examples of this invention, the parameters of a moving bed reactor are used.

[0213] The general conditions for methanol synthesis are shown in Table 1.

[0214] Table 1:

[0215]

[0216] For both the present invention and the comparative examples, these parameters for methanol synthesis remain unchanged. For methanol synthesis, a commercially available methanol catalyst based on Cu / ZnO / Al2O3 is used.

[0217] For the example of methanol production from H2, CO, and CO2, the reactor inlet temperature is 193°C, but for the example of methanol production from H2, and mainly CO2, a reactor inlet temperature of 220°C is used.

[0218] The catalyst is cooled by boiling water, with a temperature of 212°C used to produce methanol from H2, CO and CO2, and a temperature of 240°C used to produce methanol from H2, and mainly CO2.

[0219] In all cases, the reactor inlet pressure was 73 bar (absolute). For all embodiments of the invention using crude H2, the concentration of inert components at the methanol synthesis reactor was 30 vol%. For comparative examples with purified H2 as feed, the concentration of inert components at the methanol synthesis reactor was < 2.0 vol%. The inert components were N2, CH4, and C2H6. The gas hourly space velocity (GHSV) was maintained at Nm. 3 / (m 3 Kat. The constant value for h is 6127 1 / h.

[0220] The stoichiometric constant Ks is 3.4 for all instances.

[0221]

[0222] To adjust the amounts of GHSV and inert components, a sufficient amount of recycle gas is removed from and purged from the methanol synthesis loop.

[0223] The H2 yield of the H2 recovery section was 83% in all instances. The CH4 slip through the H2 recovery section was 0.1%.

[0224] Work examples

[0225] In the following examples: there is a comma after the integer, and thousands are separated by a dot.

[0226] Example 1 (This Invention)

[0227] The selected components used for flows III, VI, XII, XIV, XIII, and XI+X are summarized in Table 3. Example 1 of the present invention is shown in Figure 2a.

[0228] Table 3:

[0229]

[0230] In Example 1 of the present invention, methanol synthesis is carried out using a mixture of reactive components, H2, CO and CO2.

[0231] The crude H2 (stream III) is desulfurized at a Cu / ZnO catalytic absorber. H2S is converted into very stable NiS, so the sulfur concentration after the Cu / ZnO catalytic absorber is below 0.1 vol. ppm. This low sulfur content in the syngas is beneficial to the activity and lifetime of the methanol synthesis catalyst. To prepare a suitable makeup gas (stream VI) for methanol synthesis, the desulfurized crude H2 is mixed with H2 from the H2 recovery unit. This mixture is rich in CO2 and CO, with a CO2 concentration of 3.5 vol.-% and a CO concentration of 26.7 vol.-%. The required stoichiometric constant Ks for the makeup gas stream (VI) is 2.050 to ensure that Ks is 3.4 before the methanol synthesis reactor.

[0232] Under these conditions, in order to maintain the inert content level and GHSV, 233 Nm is removed from the methanol synthesis loop. 3 / t MeOH The purge gas stream (XII) (containing 50.5 vol.% H2) is fed into the H2 recovery section. 97 Nm³ is recovered from this stream. 3 / t MeOH Almost pure H2 (with an H2 content of 99.9 vol.-%) is fed back to the inlet of the methanol synthesis loop into the make-up gas stream.

[0233] The exhaust gas from the H2 recovery section and the exhaust gas from the methanol purification section are sent together to a heat source for combustion.

[0234] Tables 4 and 5 below show a compilation of the most important results of all the examples and comparative examples of the present invention:

[0235] Table 4:

[0236]

[0237] Table 5:

[0238]

[0239] The carbon yield is 87.1% and the crude H2 demand is 1595 Nm³. 3 / t MeOH Due to the combustion of all exhaust gases, CO2 emissions are 0.200 t. CO2 / t MeOH .

[0240] Carbon yield is the ratio of all carbon fed into the process (including inert components like CH4 and C2H4) to the carbon in the valuable product methanol.

[0241] Example 2 (This invention)

[0242] The selected components used for flows III, VI, XII, XIV, XIII, and XI+X are summarized in Table 6. Example 2 of the present invention is shown in Figure 3a.

[0243] Table 6:

[0244]

[0245] In Example 2 of the present invention, methanol synthesis is carried out using a reactive component mixture of H2, CO and CO2 without CO2 emissions.

[0246] The crude H2 (stream III) is desulfurized at a Cu / ZnO catalytic absorber. H2S is converted into very stable NiS, so the sulfur concentration after the Cu / ZnO catalytic absorber is less than 0.1 vol.ppm. This low sulfur content in the syngas is beneficial to the activity and lifetime of the methanol synthesis catalyst. To prepare a suitable makeup gas (stream VI) for methanol synthesis, the desulfurized crude H2 is mixed with H2 from the H2 recovery unit. This mixture is rich in CO, with a CO concentration of 25.6 vol.-%. The CO2 produced by the oxy-fuel combustion and CO2 recovery section is quantitatively reused for methanol synthesis. The CO2 content in the makeup gas stream (VI) is 4.4 vol.-%, slightly higher than the 3.5 vol.-% in the first example of the invention.

[0247] The required stoichiometric constant Ks for the supplemental gas stream (VI) is 2.047 to ensure that Ks is 3.4 prior to the methanol synthesis reactor.

[0248] Under these conditions, in order to maintain the inert content level and GHSV, 242 Nm was removed from the methanol synthesis loop. 3 / t MeOH The purge gas stream (XII) (containing 50.9 vol.% H2) is fed into the H2 recovery section. 102 Nm³ is recovered from this stream. 3 / t MeOH Almost pure H2 (with an H2 content of 99.9 vol.-%) is fed back to the inlet of the methanol synthesis loop into the make-up gas stream.

[0249] The exhaust gas from the H2 recovery section and the methanol purification section are sent together to the oxy-fuel combustion section. 107 Nm³ is recovered from the flue gas in the oxy-fuel combustion section. 3 / t MeOH CO2 is fed back into the methanol synthesis loop and mixed in the supplementary gas stream VI.

[0250] The carbon yield (Table 3) is 100%, and the crude H2 demand is 1617 Nm³. 3 / t MeOH This is better than the first example of the invention (which has 1595 Nm). 3 / t MeOH The concentration is slightly higher, which is due to the slightly higher CO2 content in the makeup gas. Here, carbonaceous components in the makeup gas (such as CH4 and C2H6) are also converted into methanol.

[0251] Because all CO2 is recovered from the combustion of all exhaust gases, CO2 emissions are 0.0 t. CO2 / t MeOH .

[0252] Example 3 (Invention)

[0253] The selected components used for flows III, VI, XII, XIV, XIII, and XI+X are summarized in Table 7. Example 3 of the present invention is shown in Figure 2a.

[0254] Table 7:

[0255]

[0256] In Example 3 of the present invention, methanol synthesis is carried out using a reactive component mixture of only H2 and CO2, without adding additional CO to the make-up gas (stream VI).

[0257] The crude H2 (stream III) is desulfurized at a Cu / ZnO catalytic absorber. H2S is converted into very stable NiS, therefore the sulfur concentration after the Cu / ZnO catalytic absorber is below 0.1 vol. ppm. This low sulfur content in the syngas is beneficial to the activity and lifetime of the methanol synthesis catalyst. To prepare a suitable makeup gas (stream VI) for methanol synthesis, the desulfurized crude H2 is mixed with H2 from the H2 recovery unit. This mixture is rich in CO2, with a CO2 concentration of 22.8 vol.-%. The required stoichiometric constant Ks for the makeup gas stream (VI) is 2.145 to ensure that Ks is 3.4 before the methanol synthesis reactor.

[0258] Under these conditions, in order to maintain the inert content level and GHSV, 430 Nm was removed from the methanol synthesis loop. 3 / t MeOH The purge gas stream (XII) (containing 56.7 vol.% H2) is fed into the H2 recovery section. 202 Nm³ is recovered from this stream. 3 / t MeOHAlmost pure H2 (with an H2 content of 99.9 vol.-%) is fed back to the inlet of the methanol synthesis loop into the make-up gas stream.

[0259] The exhaust gas from the H2 recovery section and the exhaust gas from the methanol purification section are sent together to a heat source for combustion.

[0260] The carbon yield is 82.0% and the crude H2 demand is 2301 Nm³. 3 / t MeOH Due to the combustion of all exhaust gases, CO2 emissions are 0.297 t. CO2 / t MeOH .

[0261] Example 4 (This Invention)

[0262] The selected components used for flows III, VI, XII, XIV, XIII, and XI+X are summarized in Table 8. Example 4 of the present invention is shown in Figure 3a.

[0263] Table 8:

[0264]

[0265] In Example 4 of the present invention, methanol synthesis is carried out using a reactive component mixture of only H2 and CO2, without adding additional CO to the make-up gas (stream VI) and achieving zero CO2 emissions.

[0266] The crude H2 (stream III) is desulfurized at a Cu / ZnO catalytic absorber. H2S is converted into very stable NiS, therefore the sulfur concentration after the Cu / ZnO catalytic absorber is below 0.1 Vol.ppm. This low sulfur content in the syngas is beneficial to the activity and lifetime of the methanol synthesis catalyst. To prepare a suitable makeup gas (stream VI) for methanol synthesis, the desulfurized crude H2 is mixed with H2 from the H2 recovery unit.

[0267] The mixture is rich in CO2, containing both external CO2 and CO2 produced by oxy-fuel combustion and the CO2 recovery section. This CO2 stream is quantitatively reused for methanol synthesis. The required stoichiometric constant Ks for the makeup gas stream (VI) is 2.145 to ensure that Ks is 3.4 before the methanol synthesis reactor.

[0268] Under these conditions, in order to maintain the inert content level and GHSV, 430 Nm was removed from the methanol synthesis loop. 3 / t MeOH The purge gas stream (XII) (containing 56.7 vol.% H2) is fed into the H2 recovery section. 202 Nm³ is recovered from this stream. 3 / tMeOH Almost pure H2 (with an H2 content of 99.9 vol.-%) is fed back to the inlet of the methanol synthesis loop into the make-up gas stream.

[0269] The exhaust gas (XIII) from the H2 recovery section (F) and the exhaust gas (XI) from the methanol purification section (E) are sent together to the oxy-fuel combustion section. 151 Nm³ of the flue gas from the oxy-fuel combustion section is recovered. 3 / t MeOH CO2 is fed back into the methanol synthesis loop and mixed in the supplementary gas stream VI.

[0270] The crude H2 requirement is 2301 Nm 3 / t MeOH .

[0271] The H2 demand is the same as in Example 3 of the present invention because recycled CO2 from the oxygen fuel combustion section and the CO2 recovery section replaces the fresh CO2, and the carbon production rate at Example 4 of the present invention (Table 4) is 100%.

[0272] Because all CO2 is recovered from the combustion of all exhaust gases, CO2 emissions are 0.0 t. CO2 / t MeOH .

[0273] contrast:

[0274] Example 1 (Comparison)

[0275] The selected components used for flows III', VI, XII, and XI+X are summarized in Table 9. See Figure 4 for comparative example 1.

[0276] Table 9:

[0277]

[0278] In Comparative Example 1, methanol synthesis was carried out using a mixture of reactive components, H2, CO, and CO2.

[0279] Compared to Examples 1 to 4 of the present invention, in the comparative examples, the separation of inert components from crude H2 (F) is located before the methanol unit (C). Therefore, the methanol synthesis loop operates with almost no inert components (like N2, CH4, and C2H6) and requires no or minimal purge gas flow (XII).

[0280] Compared to Examples 1 to 4 of the present invention, in the comparative examples, natural gas is pre-desulfurized at a Cu / ZnO catalytic absorber. H2S is converted into very stable NiS, therefore the sulfur concentration after the Cu / ZnO catalytic absorber is less than 0.1 Vol.ppm. This low sulfur content in the syngas is beneficial to the activity and lifetime of the methanol synthesis catalyst.

[0281] Desulfurized natural gas (Ia) is fed into the methane pyrolysis unit (A) and pyrolyzed into crude H2 stream (III') and solid carbon (IV). The crude H2 (stream III') is purified from inert components (such as N2, CH4, and C2H6). The H2 concentration is then 99.9 vol.-%, similar to the H2 from the H2 recovery section in Examples 1-4 of this invention.

[0282] To prepare a suitable makeup gas (stream VI) for methanol synthesis, the purified H2 stream from desulfurization was enriched with CO2 and CO, with a CO2 concentration of 3.5 vol.% and a CO concentration of 29.3 vol.%.

[0283] The required stoichiometric constant Ks for the supplemental gas stream (VI) is 1.946 to ensure that Ks is 3.4 prior to the methanol synthesis reactor.

[0284] Under these conditions and GHSV, only 0.2 Nm is extracted from the methanol synthesis loop. 3 / t MeOH The purge gas stream (XII) contained 86.2 vol.% H2.

[0285] The exhaust gas (XIII) from the front-end H2 recovery section (F) and the exhaust gas (XI) from the methanol purification section (E) are sent together to a heat source for combustion.

[0286] The carbon yield is 86.6% and the crude H2 demand is 1896 Nm³. 3 / t MeOH Due to the combustion of all exhaust gases, CO2 emissions are 0.208 t. CO2 / t MeOH .

[0287] Summarize

[0288] The crude H2 requirement of Comparative Example 1 is greater than that of Example 1 of the present invention (which has 1595 Nm). 3 / t MeOH ) 19% higher. In Comparative Example 1, the entire H2 stream to the methanol synthesis loop was purified (1898 Nm³). 3 / t MeOH It has 93.0 vol.-% H2), and in Example 1 of the present invention, it comes only from the purge gas stream (233 Nm).3 / t MeOH H2 with a vol.% H2 content must be recycled.

[0289] Although the purge gas flow was avoided in Comparative Example 1, the carbon yield was 86.6%.

[0290] Example 2 (Comparison)

[0291] The selected components used for flows III', VI, XII, and XI+X are summarized in Table 10. See Figure 4 for comparative example 2.

[0292] Table 10:

[0293]

[0294] In Comparative Example 2, methanol synthesis was carried out using a reactive component mixture of only H2 and CO2, without adding additional CO to the make-up gas (stream VI).

[0295] Compared to Examples 1 to 4 of the present invention, in the comparative examples, the separation of inert components from crude H2 is located before the methanol unit (C). Therefore, the methanol synthesis loop operates with almost no inert components (like N2, CH4, and C2H6) and requires no purge gas stream (XII) or only a minimal purge gas stream.

[0296] Compared to Examples 1 to 4 of the present invention, in the comparative examples, natural gas is pre-desulfurized at a Cu / ZnO catalytic absorber. H2S is converted into very stable NiS, therefore the sulfur concentration after the Cu / ZnO catalytic absorber is less than 0.1 Vol.ppm. This low sulfur content in the syngas is beneficial to the activity and lifetime of the methanol synthesis catalyst.

[0297] Desulfurized natural gas (Ia) is fed into the methane pyrolysis unit (A) and pyrolyzed into crude H2 stream (III') and solid carbon (IV). The crude H2 (stream III') is purified from inert components (such as N2, CH4, and C2H6). The H2 concentration is then 99.9 vol.-%, similar to the H2 from the H2 recovery section in Examples 1-4 of this invention.

[0298] To prepare a suitable makeup gas (stream VI) for methanol synthesis, the purified and desulfurized H2 feed stream was mixed only with CO2, without adding CO to the makeup gas stream (VI). The CO2 concentration was 25.3 vol.%.

[0299] The required stoichiometric constant Ks for the supplemental gas stream (VI) is 1.949 to ensure that Ks is 3.4 prior to the methanol synthesis reactor.

[0300] Due to the relatively high solubility of CO2 in the crude methanol-water mixture, more CO2 leaves the synthesis loop and is lost, thus becoming unusable for conversion into methanol.

[0301] Under these conditions and GHSV, only 0.3 Nm is extracted from the methanol synthesis circuit. 3 / t MeOH The purge gas stream (XII) contained 85.6 vol.% H2.

[0302] The exhaust gas (XIII) from the front-end H2 recovery section (F) and the exhaust gas (XI) from the methanol purification section (E) are sent together to a heat source for combustion.

[0303] The carbon yield is 82.6% and the crude H2 demand is 2721 Nm³. 3 / t MeOH Due to the combustion of all exhaust gases, CO2 emissions are 0.284 t. CO2 / t MeOH .

[0304] Summarize:

[0305] The crude H2 requirement of Comparative Example 2 is greater than that of Example 3 of the present invention (which has 2301 Nm). 3 / t MeOH The concentration was 18% higher. In Comparative Example 2, the entire H2 stream to the methanol synthesis loop was purified (2721 Nm³). 3 / t MeOH (with 93.0 vol.-% H2), and in Example 3 of the present invention, it comes only from the purge gas stream (430 Nm). 3 / t MeOH H2 with a vol.% H2 content must be recycled.

[0306] Although the purge gas flow was avoided in Comparative Example 1, the carbon yield was 82.6%.

Claims

1. A method for preparing methanol by (a) pyrolyzing and hydrogenating a feed stream (I) containing light hydrocarbons and optionally carbon oxides and sulfur compounds to (aii) a crude pyrolysis gaseous product stream (III) containing hydrogen, residual methane, and optionally carbon oxides and hydrogen sulfide, and (aii) solid carbon (IV); (b) separating the solid carbon (IV) from the crude pyrolysis gaseous product stream (III); (c) optionally separating hydrogen sulfide from the crude pyrolysis gaseous product stream (III) to produce (ci) a crude pyrolysis gaseous product stream (VI) containing hydrogen, residual methane, and optionally carbon oxides, and (cii) optionally adsorbed sulfur (V); (d) converting the crude pyrolysis gaseous product stream (III) or (VI) with carbon oxides (II) into crude methanol (VII); and (e) removing an uncondensed gas stream, i.e., purge gas (XII), from the crude methanol (VII). (f) Separate the methanol stream (VIII) from the purge gas (XII); (g) purify the methanol stream (VIII); separate hydrogen (XIV) from the purge gas (XII); and (h) recycle the hydrogen (XIV) to the methanol synthesis unit in stage (d).

2. The method according to claim 1, wherein, The hydrogen gas (XIV) was separated to a purity of ≥ 95 vol.-% to 100 vol.-%.

3. The method according to claims 1 to 2, wherein, The pyrolysis in stage (a) is heated electrically.

4. The method according to any one of claims 1 to 3, wherein, The pyrolysis in stage (a) is nonmetallic catalytic hydrocarbon pyrolysis.

5. The method according to any one of claims 1 to 4, wherein, The pyrolysis in stage (a) is carried out in a moving bed reactor—in which the bed contains carbon materials, metals, ceramics and / or mixtures thereof as substrates—at a temperature ranging from 500°C to 2000°C and a pressure ranging from 1 bar to 100 bar, and wherein the substrate is guided in a countercurrent manner to the feed stream (I).

6. The method according to any one of claims 1 to 5, wherein, The feed stream (I) containing light hydrocarbons and optionally carbon oxides and sulfur compounds is introduced via the bottom of the moving bed reactor at a temperature of 10°C to 200°C, and the substrate is introduced via the top of the moving bed reactor at a temperature of 10°C to 200°C.

7. The method according to any one of claims 1 to 6, wherein, The crude pyrolysis gaseous product stream (III) preferably exits via the top of the moving bed reactor at a temperature of 10°C to 200°C, and the solid carbon (IV) is taken out via the bottom of the moving bed reactor at a temperature of 10°C to 200°C.

8. The method according to any one of claims 1 to 7, wherein, The solid carbon produced in stage (a) has a true density in the range of 1.5 to 2.5 g / cc, a bulk density in the range of 0.5 to 1.5 g / cc, and a particle size in the range of 0.3 mm (d10) to 8 mm (d90).

9. The method according to any one of claims 1 to 8, wherein, This method The process includes the following stages: (i) a portion of the uncondensed gas stream (XII) is recycled as recirculated gas (XV) to the methanol synthesis unit in stage (d).

10. The method according to any one of claims 1 to 9, wherein, This method The process includes the following stages: (j) burning the exhaust gas from hydrogen recovery to form carbon dioxide-containing flue gas (XVI), and separating a carbon dioxide-rich stream (XVII) from the carbon dioxide-containing flue gas (XVI) in a carbon oxide recovery unit (H) and recycling the separated carbon dioxide-rich stream (XVII) to the methanol synthesis in stage (d).

11. The method according to any one of claims 1 to 10, wherein, This method It includes the following stages: (k) supplying carbon oxide feedstock (II) to the crude pyrolysis gaseous product stream (VI), the crude pyrolysis gaseous product stream (III), the feed stream (I), the methane pyrolysis unit (A) of stage (a), and / or the methanol synthesis unit (C) of stage (d).

12. The method according to any one of claims 1 to 11, wherein, Carbon dioxide and hydrogen are converted into methanol.

13. The method according to any one of claims 1 to 12, wherein, A portion of the solid carbon is processed and recycled back to the pyrolysis unit as the substrate for the moving bed.

14. The method according to any one of claims 1 to 13, wherein, The three waste gas streams, namely waste gas (XI) from the methanol purification unit (E), waste gas (XIII) from the hydrogen recovery unit (F), and waste gas (XIX) from the carbon treatment unit (J), are directed to the combustion unit (G).

15. The method according to any one of claims 1 to 14, wherein, The feed stream (I) containing light hydrocarbons contains up to 10 vol.% sulfur compounds.

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