Process for preparing methanol through carbon dioxide hydrogenation coupled with carbon dioxide capture

Abstract

The invention discloses a process for preparing methanol through carbon dioxide hydrogenation coupled with carbon dioxide capture. The process comprises the following steps: continuously adding an aqueous solution of organic amine into a primary reactor, continuously pumping carbon dioxide or enriched gas of the carbon dioxide through a Venturi ejector, and conveying the organic amine solution rich in the carbon dioxide into a secondary reactor; in the second-stage reactor, besides the organic amine solution rich in carbon dioxide, a solvent containing a catalyst is continuously introduced, hydrogen is continuously pumped in through a Venturi ejector, and a reaction solution is conveyed to the next-stage reactor; the reaction liquid of the n-stage reactor is conveyed to a three-phase separator for oil-water separation, and an oil phase and a water phase are respectively rectified to obtain methanol. According to the invention, the problem of gas-liquid mass transfer limitation in the process of carbon dioxide absorption by organic amine and methanol preparation by carbon dioxide hydrogenation is solved by using the jet loop reactor, and the homogeneous catalyst is combined, so that the reaction rate is greatly increased, and the process is continuous at the same time.

Description

Technical Field

[0001] The invention relates to a process for preparing methanol by hydrogenating carbon dioxide using a multi-stage series jet loop reactor, and belongs to the technical field of carbon dioxide capture, storage and utilization (CCUS). Background Art

[0002] In recent years, the global temperature has gradually risen, leading to an increase in extreme weather events, which also endangers human health. After industrialization, people have adopted large-scale mechanization for farming and production, and used a large amount of oil and diesel, which has led to a gradual increase in greenhouse gases. Among them, carbon dioxide is the main greenhouse gas, and its rising concentration is part of the reason for the intensification of the greenhouse effect.

[0003] At present, CO2 capture, storage and utilization (CCUS) technology is the most effective method for CO2 emission reduction, which refers to separating CO2 from the atmosphere or exhaust gas, and then directly utilizing or transporting it to a storage site for storage. CCUS technology is the basis for decarbonization of fossil energy and one of the technical combinations for achieving the goals of the Paris Climate Agreement. The EU has listed CCUS technology as one of its energy strategic technologies.

[0004] The utilization of carbon dioxide is an important part of CCUS technology. The economic value generated by the utilization of carbon dioxide can reduce the cost of the entire CCUS technology. Among them, MeOH prepared by CO2 hydrogenation is an important raw material for the production of formaldehyde, dimethyl ether, acetic acid and olefins. It can also be used as a solvent, fuel and gasoline additive. It is one of the important ways to realize the resource utilization of CO2.

[0005] The technical route for preparing green methanol from CO2 is divided into two parts: the capture and recovery of carbon dioxide (high-purity carbon dioxide is obtained after capture and purification of low-concentration carbon dioxide), and the hydrogenation of CO2 to synthesize methanol. At present, the common carbon dioxide capture technology in industry is the organic amine absorption method, and the main technical route for synthesizing methanol from CO2 hydrogenation is the synthesis of methanol by the catalytic reaction of carbon dioxide and hydrogen in a fixed bed reactor under high temperature and high pressure through heterogeneous catalysts. This technology has the following problems: since the desorption process in the carbon capture process is an endothermic process, the large heat capacity of water leads to high energy required for vaporization, and the desorption of carbon dioxide by the absorption liquid in the solvent recovery tower consumes a lot of heat energy, resulting in poor economic efficiency; since the preparation of green methanol from CO2 is an exothermic reaction during the synthesis process, it is constrained by thermodynamic equilibrium at high temperature, the single-pass conversion rate of CO2 is low, and the reverse water gas reaction to generate CO is an endothermic reaction, resulting in low reaction selectivity, which is difficult to meet the needs of industrial applications. In addition, both carbon dioxide and hydrogen in this process need to be pressurized to a very high pressure by a compressor to meet the overall energy consumption.

[0006] US1149230282 and US10961173 reported a method for producing green methanol by in-situ catalytic hydrogenation using a classic heterogeneous catalyst Cu / ZnO / Al2O3 coupled alcohol-tertiary amine system to capture carbon dioxide; CN 118026814A discloses a technology for preparing methanol by hydrogenating carbon dioxide through a heterogeneous catalyst in a low eutectic solvent absorbent formed by a composite of acetylguanidine and ethylene glycol; CN118406091A provides a novel catalyst for coupling carbon dioxide capture and catalytic hydrogenation to produce green methanol, and directly catalytic hydrogenation of carbon dioxide-enriched liquid to synthesize green methanol; CN117654402A discloses a green methanol preparation system and method coupled with direct air carbon capture and utilization, including a direct air carbon capture unit, a water electrolysis unit, a green methanol preparation unit, and an energy ladder utilization control unit, wherein the direct air carbon capture unit adopts a K-Ca cyclic absorption process constructed with KOH and Ca(OH)2 as the core; although the process of coupling carbon dioxide capture and catalytic hydrogenation to synthesize green methanol has been reported, there has been no research report on the continuous process and device for coupling industrial amine carbon capture and hydrogenation to produce green methanol, and there are also few reports on the mild process (low temperature and low pressure) using homogeneous catalysts.

[0007] Therefore, in response to the above-mentioned technical problems, it is urgent to develop a new methanol synthesis process and equipment to achieve efficient and continuous production of methanol under mild conditions based on the coupled carbon capture process, while improving product yield and reducing overall energy consumption. Summary of the invention

[0008] The problem to be solved by the present invention is to provide a continuous process and device for preparing methanol by coupling carbon capture and carbon dioxide hydrogenation homogeneous catalysis, so as to avoid the problems of high energy consumption for carbon dioxide desorption, high reaction temperature, low single-pass conversion rate, etc. in the traditional gas-solid reaction process, and the catalyst, solvent and absorbent can be recycled.

[0009] In order to solve the above problems, the present invention provides the following technical solutions:

[0010] A process for producing methanol by hydrogenation of carbon dioxide coupled with carbon dioxide capture comprises the following steps:

[0011] Step 1): an aqueous solution of an organic amine is continuously added to a primary reactor and carbon dioxide or a carbon dioxide-enriched gas is continuously pumped in through a venturi ejector. The outlet of the primary reactor is cooled through a condenser and then returned to the primary reactor. The outlet of the primary reactor is used to transport the organic amine solution rich in carbon dioxide to a secondary reactor.

[0012] Step 2): In addition to the organic amine solution rich in carbon dioxide, the secondary reactor also continuously introduces a solvent containing a catalyst, and continuously draws in hydrogen through a venturi ejector. One outlet of the secondary reactor is heated by a heater and then returns to the secondary reactor, and the other outlet transports the reaction liquid to the tertiary reactor; the reaction process from the tertiary reactor to the n-stage reactor is the same as that of the secondary reactor, wherein one outlet of the n-stage reactor is heated by a heater and then returns to the n-stage reactor, and the other outlet transports the reaction liquid to the three-phase separator;

[0013] Step 2): The reaction liquid entering the three-phase separator is separated into oil and water, the oil phase is distilled by the oil phase distillation tower to obtain methanol at the top of the tower, the solvent containing the catalyst is obtained at the bottom of the tower and returned to the secondary reactor to continue the reaction, the water phase is distilled by the water phase distillation tower to obtain methanol at the bottom of the tower, the aqueous solution of organic amine is obtained at the top of the tower and returned to the primary reactor to continue carbon capture.

[0014] Preferably, the organic amine is pentaethylenehexamine (PEHA), triethylenetetramine (TETA), triethylenediamine (TEDA), diethylenetriamine (DETA), tetraethylenepentamine (TEPA), diethanolethylenediamine (DEEDA), preferably pentaethylenehexamine (PEHA); the concentration of the aqueous solution of the organic amine is 15 to 45wt%, preferably 30wt%.

[0015] Preferably, the catalyst is a Schiff base ruthenium complex (structural formula A1) or a Schiff base ruthenium complex (structural formula A2, preferably A2):

[0016]

[0017] Preferably, the solvent is 2-methyltetrahydrofuran (2-MTHF), cyclopentane methyl ether (CPME), 2,5-dimethyltetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, preferably 2-methyltetrahydrofuran (2-MTHF); the concentration of the catalyst in the solvent is 5 to 100 mmol / L, preferably 50 mmol / L.

[0018] Preferably, the molar ratio of the solvent to the aqueous solution is 0.5 to 3, preferably 1.

[0019] Preferably, the liquid linear velocity at the nozzle of the Venturi injector in the n-stage reactor is controlled at 40-100 m / s, preferably 75 m / s.

[0020] Preferably, the flow ratio of the reaction liquid at the outlet of the first reactor returning to the first reactor and being transported to the second reactor is 2 to 6:1, preferably 3:1; the flow ratio of the reaction liquid from the outlet of the second reactor to the n-stage reactor entering the heat exchanger and being transported to the next-stage reactor or the three-phase separator is 2 to 8:1, preferably 4.5:1.

[0021] Preferably, the absorption pressure of the primary reactor is controlled to be 0.05-0.9 MPaG, preferably 0.75 MPaG; the absorption temperature of the primary reactor is controlled to be 20-40°C, preferably 30°C; the reaction temperature of the primary reactor is controlled to be 150-180°C, preferably 160°C; the pressure of the secondary reactor to the nth reactor is controlled to be 1.5-4 MPaG, preferably 2.5 MPaG.

[0022] The present invention also provides a device for preparing methanol by hydrogenating carbon dioxide coupled with carbon dioxide capture, which comprises n reactors connected in series, which are first-stage reactor to n-stage reactor in order of reaction, and each reactor is provided with a venturi ejector; the outlet of the first-stage reactor is divided into two paths by a circulating pump, one path is connected to the first-stage reactor through a condenser to form a loop, and the other path is connected to the second-stage reactor; the outlets of the second-stage reactor to the n-1-stage reactor are divided into two paths by a circulating pump, one path is connected to the corresponding reactor through a heater to form a loop, and the other path is connected to the next-stage reactor; the outlet of the n-stage reactor is divided into two paths by a circulating pump, one path is connected to the n-stage reactor through a heater to form a loop, and the other path is connected to a three-phase separator through a cooler; the gas phase outlet of the three-phase separator is connected to an exhaust gas pipeline; the water phase outlet of the three-phase separator is connected to a water phase distillation tower, and the bottom of the water phase distillation tower is connected to the second-stage reactor through a delivery pump 1; the oil phase outlet of the three-phase separator is connected to the oil phase distillation tower, and the bottom of the oil phase distillation tower is connected to the first-stage reactor through a delivery pump 2; the tops of the water phase distillation tower and the oil phase distillation tower are connected to a storage tank.

[0023] Preferably, the number of reactors is 2-6, preferably 3; the reactor is a jet loop reactor; the height-to-diameter ratio of the reactor is 3-9:1, preferably 5:1; the outlet of each reactor is divided into two pipelines by a circulating pump, and a regulating valve and a flow meter are provided on the pipeline.

[0024] Preferably, the ratio of the opening inner diameter of the inlet section of the Venturi ejector, the nozzle inner diameter, the air chamber closing inner diameter, the mixing section length, and the diffusion section length is 25:1-4:2-6:10-80:400-800, preferably 25:2:4:50:500; the opening angle of the diffusion section is 10-40°, preferably 20°; the bottom insertion position of the Venturi ejector is located at 5-20% of the height of the entire reactor, preferably 15%.

[0025] The present invention solves the problem of limited gas-liquid mass transfer in the process of organic amine absorption of carbon dioxide and carbon dioxide hydrogenation to methanol by using a jet loop reactor, and combines the use of a homogeneous catalyst to greatly improve the reaction rate while realizing the continuity of the process.

[0026] The present invention repeatedly calculates the reaction rate through a large number of experiments to determine the optimal Venturi ejector structural parameters, thereby achieving the optimal reaction rate and the maximum catalyst utilization rate, and controls the circulation loop to achieve continuous and stable output of the product, which can effectively save costs and achieve green energy saving.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The present invention uses an organic amine aqueous solution to absorb carbon dioxide and hydrogenates it with a solvent to form a two-phase system to prepare methanol, thereby avoiding the problem of high energy consumption for carbon dioxide desorption in the traditional gas-solid phase reaction process;

[0029] 2. The present invention uses a homogeneous catalyst that can be dissolved in a solvent to catalyze the carbon dioxide hydrogenation reaction under mild conditions (low temperature and low pressure), which effectively alleviates the problem of increased side reactions caused by high temperature and improves the yield of methanol.

[0030] 3. The jet loop reactor is used as the key process equipment for carbon dioxide capture and carbon dioxide hydrogenation reaction to continuously produce methanol. By optimizing the structural design of the Venturi ejector, the gas-liquid mass transfer process is promoted, the reaction speed is accelerated, the reaction efficiency is improved, the reaction time is shortened, and the use of high-pressure gas compressors is avoided, saving energy consumption in the production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A schematic diagram of a device for producing methanol by hydrogenation of carbon dioxide coupled with carbon dioxide capture provided in Example 1;

[0032] Figure 2 Schematic diagram of the structure of the Venturi ejector. DETAILED DESCRIPTION

[0033] In order to make the present invention more clearly understood, preferred embodiments are described in detail below with reference to the accompanying drawings.

[0034] The invention provides a device for preparing methanol by hydrogenating carbon dioxide coupled with carbon dioxide capture, comprising n reactors connected in series, which are first-stage reactor to n-stage reactor in order of reaction, and each reactor is provided with a venturi ejector; the outlet of the first-stage reactor is divided into two paths by a circulation pump, one path is connected to the first-stage reactor through a condenser to form a loop, and the other path is connected to the second-stage reactor; the outlets of the second-stage reactor to the n-1-stage reactor are divided into two paths by a circulation pump, one path is connected to the corresponding reactor through a heater to form a loop, and the other path is connected to the next-stage reactor; the outlet of the n-stage reactor is divided into two paths by a circulation pump, one path is connected to the n-stage reactor through a heater to form a loop, and the other path is connected to a three-phase separator through a cooler; the gas phase outlet of the three-phase separator is connected to an exhaust gas pipeline; the water phase outlet of the three-phase separator is connected to a water phase distillation tower, and the bottom of the water phase distillation tower is connected to the second-stage reactor through a first delivery pump; the oil phase outlet of the three-phase separator is connected to the oil phase distillation tower, and the bottom of the oil phase distillation tower is connected to the first-stage reactor through a second delivery pump; the tops of the water phase distillation tower and the oil phase distillation tower are connected to a storage tank.

[0035] The number of reactors is 2-6, preferably 3; the reactor adopts a jet loop reactor; the height-to-diameter ratio of the reactor is 3-9:1, preferably 5:1; the outlet of each reactor is divided into two pipelines by a circulation pump and a regulating valve and a flow meter are provided.

[0036] The ratio of the opening inner diameter of the inlet section of the Venturi ejector, the nozzle inner diameter, the closing inner diameter of the air chamber, the length of the mixing section, and the length of the diffusion section is 25:1-4:2-6:10-80:400-800, preferably 25:2:4:50:500; the opening angle of the diffusion section is 10-40°, preferably 20°; the bottom insertion position of the Venturi ejector is located at 5-20% of the height of the entire reactor, preferably 15%.

[0037] The present invention provides a process for producing methanol by hydrogenating carbon dioxide coupled with carbon dioxide capture, comprising the following steps:

[0038] Step 1): an aqueous solution of an organic amine is continuously added to a primary reactor and carbon dioxide or a carbon dioxide-enriched gas is continuously pumped in through a venturi ejector. The outlet of the primary reactor is cooled through a condenser and then returned to the primary reactor. The outlet of the primary reactor is used to transport the organic amine solution rich in carbon dioxide to a secondary reactor.

[0039] Step 2): In addition to the organic amine solution rich in carbon dioxide, the secondary reactor also continuously introduces a solvent containing a catalyst, and continuously draws in hydrogen through a venturi ejector. One outlet of the secondary reactor is heated by a heater and then returns to the secondary reactor, and the other outlet transports the reaction liquid to the tertiary reactor; the reaction process from the tertiary reactor to the n-stage reactor is the same as that of the secondary reactor, wherein one outlet of the n-stage reactor is heated by a heater and then returns to the n-stage reactor, and the other outlet transports the reaction liquid to the three-phase separator;

[0040] Step 2): The reaction liquid entering the three-phase separator is separated into oil and water, the oil phase is distilled by the oil phase distillation tower to obtain methanol at the top of the tower, the solvent containing the catalyst is obtained at the bottom of the tower and returned to the secondary reactor to continue the reaction, the water phase is distilled by the water phase distillation tower to obtain methanol at the bottom of the tower, the aqueous solution of organic amine is obtained at the top of the tower and returned to the primary reactor to continue carbon capture.

[0041] The organic amine is pentaethylenehexamine (PEHA), triethylenetetramine (TETA), triethylenediamine (TEDA), diethylenetriamine (DETA), tetraethylenepentamine (TEPA), diethanolethylenediamine (DEEDA), preferably pentaethylenehexamine (PEHA); the concentration of the aqueous solution of the organic amine is 15-45wt%, preferably 30wt%.

[0042] The catalyst is a Schiff base ruthenium complex (with the structural formula A1) or a Schiff base ruthenium complex (with the structural formula A2, preferably A2).

[0043] Wherein, the preparation method of Schiff base ruthenium complex is:

[0044] A certain amount of nail compound 1 (C 46 H 65 Cl2NzPRu, molecular weight: 848.97) was added to anhydrous pyridine and stirred to dissolve the solid. The reaction mixture was stirred at room temperature for 5.0 hours. At this time, the solution turned dark green. Stirring was stopped and the reaction mixture was added dropwise to the petroleum ether solvent, and stirred vigorously. During this process, green precipitates were slowly precipitated from the reaction solution. After the reaction was completed, the reaction solution was filtered to obtain a green solid. The solid was washed three times with petroleum ether to remove the adsorbed pyridine, and vacuum dried to obtain the product catalyst A1. The above compound 1 was purchased from Adamas Company, and the specific reaction equation is shown below:

[0045]

[0046] The preparation method of Schiff base ruthenium complex is:

[0047] An ethanol solution (20 mL) of 1-phenyl-2,3-dimethyl-4-aminopyrazol-5-one (4-aminoantipyrine) was added to an ethanol solution of salicylaldehyde. After stirring, a yellow solid intermediate product 2 appeared, which was recrystallized and filtered out from ethanol. The solid intermediate product 2 was added to an ethanol solution of o-phenylenediamine. After the mixture was refluxed for about 30 hours, a brown solid product (Schiff base B) appeared. It was recrystallized and filtered out from ethanol.

[0048] Schiff base B dissolved in hot ethanol is added to the hot ethanol solution of ruthenium trichloride and refluxed for 30 minutes. The resulting solution is heated and evaporated to one-third, then filtered, and finally washed with hot ethanol to obtain catalyst A2. The raw materials 4-aminoantipyrine and salicylaldehyde in the above method are purchased from Merck, and the specific reaction equation is shown below:

[0049]

[0050] The solvent is 2-methyltetrahydrofuran (2-MTHF), cyclopentane methyl ether (CPME), 2,5-dimethyltetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, preferably 2-methyltetrahydrofuran (2-MTHF); the concentration of the catalyst in the solvent is 5 to 100 mmol / L, preferably 50 mmol / L.

[0051] The molar ratio of the solvent to the aqueous solution is 0.5 to 3, preferably 1.

[0052] The liquid linear velocity at the nozzle of the Venturi ejector in the n-stage reactor is controlled at 40-100 m / s, preferably 75 m / s.

[0053] The reaction liquid at the outlet of the first reactor returns to the first reactor and is transported to the second reactor at a flow ratio of 2 to 6:1, preferably 3:1; the reaction liquid from the outlet of the second reactor to the n-stage reactor enters the heat exchanger and is transported to the next reactor or the three-phase separator at a flow ratio of 2 to 8:1, preferably 4.5:1.

[0054] The absorption temperature of the first reactor is controlled at 20-40°C, preferably 30°C; the reaction temperature of the first reactor is controlled at 150-180°C, preferably 160°C; the pressure of the second reactor to the nth reactor is controlled at 1.5-4MPaG, preferably 2.5MPaG.

[0055] The test method used in Examples 1-5 is:

[0056] Test instrument: Agilent 8860GC (chromatographic column J&W DB-FATWAX, 30m×0.25×0.25mm, FID detector);

[0057] Test conditions: carrier gas helium, 1 mL / min, column temperature 70°C (10 min) -10°C / min -150°C (0 min), detector 250°C.

[0058] Example 1

[0059] The device used in this embodiment is as follows Figure 1 As shown, it includes three reactors connected in series, which are, in order of reaction, a primary reactor 1 (with a Venturi ejector 2), a secondary reactor 5 (with a Venturi ejector 6), and a tertiary reactor 9 (with a Venturi ejector 10); the outlet at the bottom of the primary reactor 1 is divided into two paths by a circulating pump 4, one path is connected to the top of the primary reactor 1 through a condenser 3 to form a loop, and the other path is connected to one side of the middle of the secondary reactor 5; the outlet at the bottom of the secondary reactor 5 is divided into two paths by a circulating pump 8, one path is connected to the top of the secondary reactor 5 through a heater 7 to form a loop, and the other path is connected to one side of the middle of the tertiary reactor 9; the outlet of the tertiary reactor 9 is divided into two paths by a circulating pump 3 12, one path is connected to the top of the tertiary reactor 9 through a heater 11 to form a loop, and the other path is connected to a three-phase separator 13 through a cooler 18. The gas phase outlet of the three-phase separator 13 is connected to the tail gas pipeline; the water phase outlet is connected to the upper part of the water phase distillation tower 15, and the bottom of the water phase distillation tower 15 is connected to the top of the secondary reactor 5 through the delivery pump 1 16; the oil phase outlet is connected to the upper part of the oil phase distillation tower 14, and the bottom of the oil phase distillation tower 14 is connected to the top of the primary reactor 1 through the delivery pump 2 17; the tops of the water phase distillation tower 15 and the oil phase distillation tower 14 are respectively connected to a cooler, one of the cooler outlets is connected to the storage tank, and the other is connected to the corresponding water tank distillation tower 15 or the upper part of the oil phase distillation tower 14. The outlets of the delivery pump 1 16 and the delivery pump 2 17 are also provided with a parallel branch that is connected to the lower part of the corresponding water tank distillation tower 15 or the oil phase distillation tower 14 through the cooler.

[0060] The reactor adopts a jet loop reactor; the outlet of each reactor is divided into two pipelines by a circulation pump, and a regulating valve and a flow meter are provided on each of the pipelines. The volume of the three reactors is 50L.

[0061] The venturi ejectors in each reactor (such as Figure 2 The liquid linear velocity at the nozzle of the venturi ejector is 75m / s, and the detailed design dimensions are as follows: the ratio of the inlet section opening inner diameter, nozzle inner diameter, air chamber closing inner diameter, mixing section length, and diffusion section length is 25:2:4:15:500, and the diffusion section opening angle is 20°. The bottom insertion position of the venturi ejector is located at 15% of the height of the entire reactor. When the reaction system is in steady state, the reactor liquid level is stable at 75±5% of the height of the entire reactor. The height-to-diameter ratio of the reactor is 5:1.

[0062] The preparation process is:

[0063] Add 30wt% PEHA (pentaethylenehexamine) aqueous solution to the primary reactor until the reactor liquid level is 50% of the height, and add 30wt% PEHA aqueous solution and a solvent containing Schiff base ruthenium complex A2 (the molar ratio of the solvent to the aqueous solution is 1:1, and the concentration of Schiff base ruthenium complex A2 is 50mmol / L) to the subsequent two reactors until the liquid level of the two reactors is 50% of the height. After sealing, introduce carbon dioxide into the primary reactor until the system pressure is 0.5MPa, introduce hydrogen into the subsequent two reactors, and start the circulation pump to replace the air in the reactor six times. After the replacement is completed, the pressure of the primary reactor (carbon capture system) is adjusted to 0.75MPa by injecting carbon dioxide, and the operating temperature is maintained below 30°C. The secondary reactor and the tertiary reactor (both hydrogenation reaction systems) are adjusted to a system pressure of 2.5MP by injecting hydrogen, and the temperature is raised to a reaction temperature of 160°C, which is recorded as the reaction start time. During the reaction, the absorption pressure of the carbon capture system is constant at 0.75MPa, the pressure of the hydrogenation reaction system is constant at 2.5MPa, and the molar ratio of carbon dioxide and hydrogen entering the entire reaction system is 1:3. The flow ratio from the bottom of the first reactor to the condenser and the second reactor is 3:1 through flow control, the flow ratio from the bottom of the second reactor to the heater one and the third reactor is 4.5:1 through flow control, and the flow ratio from the bottom of the third reactor to the heater two and the three-phase separator is 4.5:1 through flow control. The reaction liquid is cooled to 60°C through the condenser and enters the 100L three-phase separator. The three-phase separator is equipped with a polymer structure to enhance the separation effect, and the operating pressure is controlled at 0.2MPa. After passing through the three-phase separator, the reaction liquid is divided into oil and water phases. The oil phase is discharged from the right outlet of the separator baffle, the water phase is discharged from the left outlet, and the excess gas is discharged from the top. The aqueous product enters the aqueous distillation tower, which uses corrugated metal plate structured packing, with a packing height of 1m and a total tower length of 1.5m. The top pressure is controlled at 0.03MPa, the top temperature is 71°C, the bottom temperature is 111°C, and the reflux ratio is 2. Finally, methanol products are obtained at the top of the tower, and PEHA solution is obtained at the bottom of the tower. The oil phase product enters the oil phase distillation tower, which uses corrugated metal plate structured packing, with a packing height of 1.5m and a total tower length of 2m. The top pressure is controlled at 0.03MPa, the top temperature is 71°C, the bottom temperature is 87°C, and the reflux ratio is 5. Finally, methanol products are obtained at the top of the tower, and 2-MTHF solvent is obtained at the bottom of the tower. The PEHA solution and 2-MTHF solvent obtained from the two towers are transported back to the primary reactor and the secondary reactor respectively, and the flow rate of the solvent circulation and the flow rate of the PEHA solution circulation are controlled to be 1:1.

[0064] During the reaction, it was detected that the average CO2 capture rate was 520L (STP) / h, the average H2 gas consumption rate was 1450L (STP) / h, the carbon dioxide conversion rate was 93%, the methanol yield was 90%, the formate yield was 3%, and the final methanol product purity was >99.9%.

[0065] Example 2

[0066] The difference between this embodiment and embodiment 1 is that Schiff ruthenium complex A1 is used as a catalyst, and the other conditions are the same as those of embodiment 1.

[0067] During the reaction, it was detected that the average CO2 capture rate was 511L (STP) / h, the average H2 gas consumption rate was 1349L (STP) / h, the carbon dioxide conversion rate was 88%, the methanol yield was 82%, the formate yield was 6%, and the final methanol product purity was >99.9%.

[0068] Example 3

[0069] The difference between this embodiment and embodiment 1 is that the number of reactors connected in series is two, namely, one is used as a carbon capture absorption jet loop reactor, and the other is used as a hydrogenation jet loop reactor. The other conditions are the same as those in embodiment 1.

[0070] During the reaction, it was detected that the average CO2 capture rate was 509L (STP) / h, the average H2 gas consumption rate was 839L (STP) / h, the carbon dioxide conversion rate was 55%, the methanol yield was 49%, the formate yield was 6%, and the final methanol product purity was >99.9%.

[0071] Example 4

[0072] The difference between this embodiment and embodiment 1 is that the concentration of the catalyst in the solvent is 10 mmol / L, and the other conditions are the same as those in embodiment 1.

[0073] During the reaction, it was detected that the average CO2 capture rate was 504L (STP) / h, the average H2 gas consumption rate was 992L (STP) / h, the carbon dioxide conversion rate was 65%, the methanol yield was 55%, the formate yield was 10%, and the final methanol product purity was >99.9%.

[0074] Example 5

[0075] The difference between this embodiment and Embodiment 1 is that the liquid linear velocity at the nozzle of Venturi injector 2 is 45 m / s, and the detailed design dimensions are that the ratio of the inlet section opening inner diameter, the nozzle inner diameter, the air chamber closing inner diameter, the mixing section length, and the diffusion section length is 25:3.75:5.5:20:600, the diffusion section opening angle is 10°, and the other conditions are the same as those in Embodiment 1.

[0076] During the reaction, it was detected that the average CO2 capture rate was 401L (STP) / h, the average H2 gas consumption rate was 1297L (STP) / h, the carbon dioxide conversion rate was 85%, the methanol yield was 80%, the formate yield was 5%, and the final methanol product purity was >99.9%.

Claims

1. A process for producing methanol by hydrogenation of carbon dioxide coupled with carbon dioxide capture, characterized in that: The following steps are involved: Step 1): an aqueous solution of an organic amine is continuously added to a primary reactor and carbon dioxide or a carbon dioxide-enriched gas is continuously pumped in through a venturi ejector. The outlet of the primary reactor is cooled through a condenser and then returned to the primary reactor. The outlet of the primary reactor is used to transport the organic amine solution rich in carbon dioxide to a secondary reactor. Step 2): In addition to the organic amine solution rich in carbon dioxide, the secondary reactor also continuously introduces a solvent containing a catalyst, and continuously draws in hydrogen through a venturi ejector. One outlet of the secondary reactor is heated by a heater and then returns to the secondary reactor, and the other outlet transports the reaction liquid to the tertiary reactor; the reaction process from the tertiary reactor to the n-stage reactor is the same as that of the secondary reactor, wherein one outlet of the n-stage reactor is heated by a heater and then returns to the n-stage reactor, and the other outlet transports the reaction liquid to the three-phase separator; Step 2): The reaction liquid entering the three-phase separator is separated into oil and water, the oil phase is distilled by the oil phase distillation tower to obtain methanol at the top of the tower, the solvent containing the catalyst is obtained at the bottom of the tower and returned to the secondary reactor to continue the reaction, the water phase is distilled by the water phase distillation tower to obtain methanol at the bottom of the tower, the aqueous solution of organic amine is obtained at the top of the tower and returned to the primary reactor to continue carbon capture.

2. The process for producing methanol by hydrogenation of carbon dioxide coupled with carbon dioxide capture according to claim 1, characterized in that: The organic amines are pentaethylenehexamine, triethylenetetramine, triethylenediamine, diethylenetriamine, tetraethylenepentamine and diethanolethylenediamine; the concentration of the aqueous solution of the organic amines is 15-45wt%.

3. The process for producing methanol by hydrogenation of carbon dioxide coupled with carbon dioxide capture according to claim 1, characterized in that: The catalyst is a Schiff base ruthenium complex (structural formula A1) or a Schiff base ruthenium complex; the solvent is 2-methyltetrahydrofuran, cyclopentane methyl ether, 2,5-dimethyltetrahydrofuran, diethylene glycol dimethyl ether, and triethylene glycol dimethyl ether; and the concentration of the catalyst in the solvent is 5 to 100 mmol / L.

4. The process for producing methanol by hydrogenation of carbon dioxide coupled with carbon dioxide capture according to claim 1, characterized in that: The molar ratio of the solvent to the aqueous solution is 0.5-3.

5. The process for producing methanol by hydrogenation of carbon dioxide coupled with carbon dioxide capture according to claim 1, characterized in that: The liquid linear velocity at the nozzle of the Venturi ejector in the n-stage reactor is controlled at 40-100 m / s.

6. The process for producing methanol by hydrogenation of carbon dioxide coupled with carbon dioxide capture according to claim 1, characterized in that: The reaction liquid at the outlet of the first reactor returns to the first reactor and is transported to the second reactor at a flow ratio of 2 to 6:1; the reaction liquid from the outlet of the second reactor to the n-stage reactor enters the heat exchanger and is transported to the next reactor or the three-phase separator at a flow ratio of 2 to 8:

1.

7. The process for producing methanol by hydrogenation of carbon dioxide coupled with carbon dioxide capture according to claim 1, characterized in that: The absorption pressure of the first reactor is controlled at 0.05-0.9 MPaG; the absorption temperature of the first reactor is controlled at 20-40°C; the reaction temperature of the first reactor is controlled at 150-180°C; and the pressure of the second to n-stage reactors is controlled at 1.5-4 MPaG.

8. A device for producing methanol by hydrogenation of carbon dioxide coupled with carbon dioxide capture, characterized in that: The invention comprises n reactors connected in series, which are first-stage reactor (1) to n-stage reactor in order of reaction, and each reactor is provided with a venturi ejector; the outlet of the first-stage reactor (1) is divided into two paths through a circulation pump, one path is connected to the first-stage reactor (1) through a condenser (3) to form a loop, and the other path is connected to the second-stage reactor (5); the outlet of the second-stage reactor to the n-1-stage reactor is divided into two paths through a circulation pump, one path is connected to the corresponding reactor through a heater to form a loop, and the other path is connected to the next-stage reactor; the outlet of the n-stage reactor is divided into two paths through a circulation pump, one path is connected to the n-stage reactor through a heater A loop is formed, and the other is connected to the three-phase separator (13) through a cooler (18); the gas phase outlet of the three-phase separator (13) is connected to the tail gas pipeline; the water phase outlet of the three-phase separator (13) is connected to the water phase distillation tower (15), and the bottom of the water phase distillation tower (15) is connected to the secondary reactor (5) through a delivery pump 1 (16); the oil phase outlet of the three-phase separator (13) is connected to the oil phase distillation tower (14), and the bottom of the oil phase distillation tower (14) is connected to the primary reactor (1) through a delivery pump 2 (17); the tops of the water phase distillation tower (15) and the oil phase distillation tower (14) are connected to the storage tank.

9. The device for producing methanol by hydrogenation of carbon dioxide coupled with carbon dioxide capture according to claim 8, characterized in that: The number of reactors is 2-6; the reactor adopts a jet loop reactor; the height-to-diameter ratio of the reactor is 3-9:1; the outlet of each reactor is divided into two pipelines by a circulation pump and both are provided with a regulating valve and a flow meter.

10. The device for producing methanol by hydrogenation of carbon dioxide coupled with carbon dioxide capture according to claim 8, characterized in that: The ratio of the opening inner diameter of the inlet section of the venturi ejector, the nozzle inner diameter, the closing inner diameter of the air chamber, the length of the mixing section, and the length of the diffusion section is 25:1-4:2-6:10-80:400-800; the opening angle of the diffusion section is 10-40°; and the bottom insertion position of the venturi ejector is located at 5-20% of the height of the entire reactor.

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