Method and device for preparing methanol by using carbon dioxide

Abstract

The invention provides a method and a device for preparing methanol by using carbon dioxide, and the method comprises the following steps in sequence: (1) introducing carbon dioxide gas and hydrogen into a mixer, and mixing in the mixer to obtain mixed gas; (2) downwards introducing the mixed gas into a reactor with a catalyst, and contacting the mixed gas with the catalyst in the reactor, so that carbon dioxide gas and hydrogen in the mixed gas react in the presence of the catalyst to obtain a product containing methanol; and (3) condensing the product containing methanol to realize gas-liquid separation, so as to prepare liquid containing methanol and condensed gas. The method provided by the invention can realize good carbon dioxide conversion rate and methanol selectivity at low temperature, low pressure, low hydrogen consumption and short reaction time.

Description

Technical Field

[0001] The present invention relates to the field of carbon reduction in the metallurgical industry, and in particular to a method and device for producing methanol by utilizing carbon dioxide. Background Art

[0002] With global warming and other environmental issues becoming increasingly severe, reducing CO2 emissions has become a common challenge facing humanity. Since the steel industry accounts for over 15% of total CO2 emissions, steel companies will face immense pressure to reduce carbon emissions over the long term. Currently and for a considerable period of time to come, the blast furnace-converter process will remain the primary process in steel production. Within this process, blast furnace ironmaking accounts for over 80% of CO2 emissions and over 70% of energy consumption, respectively. Therefore, blast furnace ironmaking is key to reducing energy consumption and CO2 emissions in the steel industry.

[0003] As we all know, traditional blast furnaces must use carbon-containing materials to produce molten iron, which generates large amounts of carbon dioxide during the reduction of iron ore. This carbon dioxide, when released into the air, pollutes the environment and contributes to the greenhouse gas effect. Therefore, controlling carbon dioxide emissions from steel production is currently a major challenge. Various capture methods can be used to separate the carbon dioxide from blast furnace exhaust gases, but how to dispose of this separated carbon dioxide remains a key issue. Currently, common methods are to use carbon dioxide to flood oil, thereby increasing oil production and generating revenue, or to store the carbon dioxide underground. However, these methods require large investments and pose significant safety risks.

[0004] In addition, using CO2 as raw material to produce high-value-added fine chemical products is also an important direction of CO2 emission reduction research. For example, using carbon dioxide and hydrogen to react to produce methanol.

[0005] Methanol can be used to produce a variety of organic products, including methyl chloride, methylamine, and dimethyl sulfate. It is also a raw material for pesticides (insecticides, acaricides) and pharmaceuticals (sulfonamides, synamycins, etc.), and is one of the raw materials for the synthesis of dimethyl terephthalate, methyl methacrylate, and methyl acrylate. Methanol can also be used to produce formaldehyde, which is used in the production of adhesives primarily for the wood processing industry, and as a treatment agent for molding compounds, coatings, textiles, and paper. Another major use of methanol is the production of acetic acid. Acetic acid consumption accounts for approximately 7% of global methanol demand and is used to produce vinyl acetate, cellulose acetate, and acetate esters, which are used in coatings, adhesives, and textiles. Methanol can also be used to produce methylamine, an important aliphatic amine that includes monomethylamine, dimethylamine, and trimethylamine and is a fundamental chemical raw material. Methanol is also used to produce growth promoters, which can significantly increase crop yields, keep branches and leaves fresh, lush, and wither in summer, and significantly reduce irrigation water consumption, benefiting the growth of dryland crops. In short, methanol is widely used, and using carbon dioxide to produce methanol has very broad application scenarios.

[0006] Patent CN201110043854.4 proposes a method for producing methanol using the hydrogenation reaction of carbon dioxide. However, the catalyst used in this method has a long preparation process, poor catalytic performance, and a selectivity of only about 30%, making it unsuitable for widespread use and large-scale production. Patent CN201810245030.7 discloses a method and system for fixing carbon dioxide produced by coal-to-methanol production. The method mainly uses coal to produce methanol and then uses microalgae to absorb and separate the carbon dioxide in the gas. However, it does not propose a suitable carbon dioxide utilization path. Therefore, there is still a need to develop an economical and efficient method for producing methanol using carbon dioxide. Summary of the Invention

[0007] In order to solve the above problems, the present invention provides a method for producing methanol using carbon dioxide, wherein the method comprises the following steps performed in sequence:

[0008] (1) introducing carbon dioxide gas and hydrogen gas into a mixer and mixing them in the mixer to obtain a mixed gas;

[0009] (2) passing the mixed gas downward into a reactor having a catalyst and contacting the mixed gas with the catalyst in the reactor, so that the carbon dioxide gas in the mixed gas reacts with the hydrogen gas in the presence of the catalyst to obtain a product containing methanol; and

[0010] (3) condensing the product containing methanol to achieve gas-liquid separation, thereby obtaining a liquid containing methanol and a condensed gas;

[0011] The catalyst is selected from a CuFe alloy catalyst and a CuZn alloy catalyst. The CuFe alloy catalyst is composed of Cu and Fe, and the mass ratio of Cu to Fe is 1:1 to 3:2; the CuZn alloy catalyst is composed of Cu and Zn, and the mass ratio of Cu to Zn is 5:6 to 4:3.

[0012] Preferably, the catalyst has a porosity of 40-55%, a particle size of 0.5-1 mm, and a sponge-like three-dimensional porous structure. Preferably, the sponge-like three-dimensional porous structure is as follows Figure 2 The specific structure of the catalyst used in the present invention can ensure that the catalyst has a certain toughness, while ensuring a large contact area between the catalyst and the reactants, and can also make the catalyst have a certain strength, thereby facilitating the use and loading and unloading of the catalyst during the reaction process.

[0013] In the present invention, the porosity and particle size of the catalyst are measured using a surface area and porosity analyzer (Nova 600BET from Anton Paar) using the BET method according to ASTM D6761-22. The catalyst of the present invention can be prepared using Fe, Zn, and CuCl2 as raw materials via a conventional physicochemical composite method, i.e., by reducing iron or zinc in a cupric chloride solution to obtain the desired CuFe alloy catalyst or CuZn alloy catalyst.

[0014] Preferably, the method further comprises a step (1') between step (1) and step (2): preheating the mixed gas obtained in step (1); preferably, the preheating temperature is 60-70°C and the preheating time is 4-5 minutes; preferably, the preheating is achieved by heating the mixed gas in a pipe that passes the mixed gas into the reactor. Preheating can enable the gas to reach the reaction temperature in a short time, thereby extending the life of the reaction equipment and improving the manufacturing efficiency of the product.

[0015] Preferably, in the present invention, the reaction in step (2) is carried out at a pressure of 3 MPa or above; since high-pressure conditions may lead to safety risks and increased costs of manufacturing equipment and safety control, the reaction is preferably carried out under low-pressure conditions of 3-10 MPa, more preferably 3-8 MPa, and even more preferably 3-5 MPa. Good technical effects can be obtained under the above pressures (for example, methanol selectivity ≥75%; carbon dioxide conversion ≥22%).

[0016] Preferably, in the present invention, the reaction in step (2) is carried out at a reaction temperature of 200°C or higher. Since high temperature conditions can lead to safety risks and increased manufacturing equipment and safety control costs, the reaction is preferably carried out at 200-250°C, more preferably 200-220°C. Good technical effects can be achieved within this temperature range (e.g., methanol selectivity ≥75%; carbon dioxide conversion ≥22%). Compared to the reaction temperature of conventional methanol production, the reaction of the present invention is carried out at this lower temperature, which is beneficial to reactor design and production process operation, and significantly reduces equipment and production costs.

[0017] In certain embodiments, the reaction temperature in the reactor is controlled by heating the reactor using a silicon carbon rod heating furnace.

[0018] In certain embodiments, the reaction pressure in the reactor is controlled by a pressure reducing valve.

[0019] Preferably, in the present invention, the reaction time in step (2) (i.e., the residence time of the gas in the reactor) is more than 2 minutes; extending the reaction time is beneficial to improving the selectivity of methanol and the conversion rate of carbon dioxide, but extending the reaction time will lead to increased energy consumption, thereby increasing production costs. Therefore, it is preferred to set the reaction time to 2-10 minutes, such as 2-8 minutes, such as 2-5 minutes, such as 2-3 minutes. The reaction is continued for the above reaction time to obtain good technical effects (for example, methanol selectivity ≥75%; carbon dioxide conversion ≥22%).

[0020] The carbon dioxide gas used in the present invention does not need to be pure carbon dioxide. The carbon dioxide gas can be carbon dioxide gas captured from industrial tail gas generated during steelmaking, wherein impurities other than carbon dioxide are permitted. The volume percentage of carbon dioxide can be greater than 95%, for example, 98-100%. The hydrogen gas used in the present invention can be any hydrogen gas that meets industrial standards, and the volume percentage of hydrogen is preferably 100%.

[0021] Preferably, in step (1), the flow rate of the carbon dioxide gas is 100-150 ml / min, preferably, the flow rate of the carbon dioxide gas is 130-150 ml / min; the flow rate of the hydrogen gas is 350-400 ml / min, preferably, the flow rate of the hydrogen gas is 380-400 ml / min; for example, the flow rate of the carbon dioxide gas is 100 ml / min, and the flow rate of the hydrogen gas is 350 ml / min; for example, the flow rate of the carbon dioxide gas is 110 ml / min, and the flow rate of the hydrogen gas is 370 ml / min; for example, the flow rate of the carbon dioxide gas is 130 ml / min, and the flow rate of the hydrogen gas is 380 ml / min; for example, the flow rate of the carbon dioxide gas is 100 ml / min, and the flow rate of the hydrogen gas is 350-400 ml / min. By setting the flow rate of carbon dioxide gas to 100-150 ml / min and the flow rate of hydrogen to 350-400 ml / min, good technical results (for example, methanol selectivity ≥75%; carbon dioxide conversion rate ≥22%) can be achieved while reducing the amount of hydrogen used, thereby reducing costs.

[0022] Preferably, in step (1), the pressure of the carbon dioxide gas is 8-10 MPa; preferably, the pressure of the hydrogen gas is 9-11 MPa. This ensures that the two groups of gases can be more fully mixed, which is more conducive to the next reaction.

[0023] Preferably, step (1) further comprises introducing an inert gas into the mixer to mix the inert gas with carbon dioxide gas and hydrogen; preferably, the flow rate of the inert gas is 50-100 ml / min; preferably, the pressure of the inert gas is 9-11 MPa; the inert gas can be selected from argon, nitrogen, helium, neon, krypton, tritium and xenon, preferably, the inert gas is nitrogen, and adding the inert gas can better adjust and ensure the required pressure of the mixed gas.

[0024] Preferably, the reactor in step (2) is a vertical reactor, and the gas from step (1) is passed downwardly into the vertical reactor through a pipeline, so that it can more fully contact and react with the catalyst in the vertical reactor. Preferably, a gas distribution plate with circular holes is provided in the vertical reactor, and the catalyst is provided on the gas distribution plate; preferably, the gas distribution plate is hemispherical to increase the contact area between the gas and the catalyst; preferably, the pore diameter of the circular holes is 0.05-0.08 mm; preferably, the circular holes are of equal size; preferably, the distribution density of the circular holes on the gas distribution plate is 13000-13500 / cm 2Preferably, the circular holes are evenly distributed on the gas distribution plate; preferably, the gas distribution plate is located in the middle of the vertical reactor; and preferably, the mass of the catalyst disposed on the gas distribution plate is 3-5 grams. The provision of the gas distribution plate ensures uniform distribution of the reaction gas, prevents gas short-circuiting, and thereby increases effective contact between the gas and the catalyst, thereby improving gas reaction efficiency and yield.

[0025] Preferably, the method further comprises step (4): treating the gas obtained after condensation as tail gas or recycling it, and detecting the content of methanol in the liquid. The content of methanol can be detected by liquid chromatography.

[0026] In the method of the present invention, the methanol selectivity is ≥70%; preferably, the methanol selectivity is ≥75%, for example, the methanol selectivity is 76-89%; the carbon dioxide conversion rate is ≥20%; preferably, the carbon dioxide conversion rate is ≥22%, for example, the carbon dioxide conversion rate is 22-33%. The methanol selectivity is the mass of the methanol produced divided by the mass of the product (composed of the liquid and CO in the gas obtained after cooling, where CO can be obtained by measuring the composition of the outlet gas). The carbon dioxide conversion rate refers to the single-pass conversion rate of carbon dioxide, which is the amount of carbon dioxide reacted (i.e., the amount of carbon dioxide initially introduced minus the amount of unreacted carbon dioxide) divided by the amount of carbon dioxide initially introduced.

[0027] On the other hand, the present invention also provides a device for producing methanol, which includes a mixer, a reactor and a condenser connected in sequence, wherein the mixer is used to mix carbon dioxide gas, hydrogen and an optional inert gas to obtain a mixed gas; the reactor is equipped with a catalyst, and in the reactor, the carbon dioxide gas and hydrogen in the mixed gas react in the presence of the catalyst to obtain a product containing methanol; and in the condenser, the product containing methanol is condensed to achieve gas-liquid separation to obtain a liquid containing methanol and a condensed gas.

[0028] Preferably, the device satisfies one or more of the following conditions:

[0029] 1) The mixed gas in the mixer is passed downward into the reactor through a pipe, and a heating belt is set in the pipe to heat the mixed gas in the pipe to 60-70°C;

[0030] 2) The reactor is a vertical reactor. Preferably, a gas distribution plate with circular holes is provided in the vertical reactor, and the catalyst is provided on the gas distribution plate; preferably, the gas distribution plate is hemispherical; preferably, the diameter of the circular holes is 0.05-0.08 mm; preferably, the circular holes are of equal size; preferably, the distribution density of the circular holes on the gas distribution plate is 13,000-13,500 / cm 2 ; Preferably, the circular holes are evenly distributed on the gas distribution plate; preferably, the gas distribution plate is arranged in the middle of the vertical reactor; preferably, the mass of the catalyst arranged on the gas distribution plate is 3-5 grams;

[0031] 3) The catalyst is selected from a CuFe alloy catalyst and a CuZn alloy catalyst, wherein the CuFe alloy catalyst is composed of Cu and Fe, and the mass ratio of Cu to Fe is 1:1 to 3:2; the CuZn alloy catalyst is composed of Cu and Zn, and the mass ratio of Cu to Zn is 5:6 to 4:3; preferably, the catalyst has a porosity of 40-55%, a particle size of 0.5-1 mm, and a sponge-like three-dimensional porous structure;

[0032] 4) The reaction is carried out at a pressure of 3 MPa or more (preferably 3-10 MPa) and a temperature of 200° C. or more (preferably 200-250° C.) for more than 2 minutes, preferably 2-10 minutes.

[0033] The method of producing methanol from carbon dioxide of the present invention has the following beneficial effects compared with the prior art:

[0034] 1. The present invention utilizes carbon dioxide and hydrogen as raw materials, controls the gas flow and pressure of the two gases, and then introduces them into a mixer for mixing. The mixture is then introduced downward into a reactor equipped with a granular catalyst. In the reactor, carbon dioxide and hydrogen react chemically in the presence of a catalyst to ultimately produce methanol. This method utilizes greenhouse gas carbon dioxide in large quantities, providing an effective method for the utilization of carbon dioxide. In particular, the method of the present invention can utilize carbon dioxide captured by steel mills to react with industrial hydrogen to produce industrial methanol products, achieving high-value utilization of carbon dioxide generated in industrial manufacturing processes, and providing a new path for the solidification of carbon dioxide, especially for carbon dioxide emission reduction in steel enterprises. The method of the present invention can realize the industrial production of methanol using waste gas carbon dioxide, reduce carbon dioxide emissions from coking and ironmaking processes, and has good environmental and economic benefits.

[0035] 2. The alloy catalyst used in the present invention has excellent catalytic performance and is inexpensive. By controlling the structure of the alloy catalyst, the reaction can be promoted to proceed more efficiently, thereby reducing the amount of catalyst used under the same reaction conditions, thereby effectively reducing the cost of the entire manufacturing process; in addition, the reaction process of the present invention can be carried out at low temperature and low pressure, thereby simplifying the control of the reaction process, reducing the safety risks brought by high temperature and high pressure as well as the equipment design and safety control costs, and can also control the gas flow rates of carbon dioxide and hydrogen within a reasonable range, reducing the amount of hydrogen used (thereby reducing costs), while achieving the excellent technical effects of methanol selectivity ≥70% and carbon dioxide conversion rate ≥20%.

[0036] 3. In the method of the present invention, the mixed gas is preheated before it is introduced into the reactor, so that the gas reaches the reaction temperature in a short time, further increasing the life of the reaction equipment and improving the manufacturing efficiency of the product.

[0037] 4. The reactor of the present invention is provided with a gas distribution plate with circular holes. By providing the gas distribution plate, the uniform distribution of the reaction gas can be ensured, and the gas short circuit can be prevented, thereby increasing the effective contact between the gas and the catalyst, and increasing the gas reaction efficiency and output. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Shown is a schematic diagram of an apparatus for implementing a method for producing methanol using carbon dioxide according to one embodiment of the present invention.

[0039] Figure 2 Shown is a sponge-like three-dimensional porous structure of a catalyst according to one embodiment of the present invention, which was photographed using a Cai EVO15 electron microscope at a field of view of 2000 times. DETAILED DESCRIPTION

[0040] The present invention is described below through specific embodiments, and those skilled in the art can understand the advantages and effects of the present invention from the contents disclosed in the present invention. Although the present invention will be introduced in conjunction with a preferred embodiment in the present invention, this does not mean that the features of the present invention are limited to this embodiment. On the contrary, the purpose of introducing the invention in conjunction with the embodiment is to cover other options or modifications that may be expanded based on the claims of the present invention. In order to provide a deep understanding of the present invention, the following description will include many specific details. The implementation of the present invention may also not use these details. In addition, in order to avoid confusion or obscuring the focus of the present invention, some specific details will be omitted in the description. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0041] Example

[0042] Example 1

[0043] The carbon dioxide used in this embodiment is carbon dioxide captured during steel production, wherein the carbon dioxide content is 98%, the hydrogen used is industrial hydrogen, wherein the hydrogen content is 100%, and the nitrogen used is industrial nitrogen, wherein the nitrogen content is 100%.

[0044] First, hydrogen, carbon dioxide and nitrogen are introduced into the mixer. The flow rate of hydrogen is 350ml / min and the pressure is 10Mpa. The flow rate of carbon dioxide is 100ml / min and the pressure is 9Mpa. The flow rate of nitrogen is 50ml / min and the pressure is 10Mpa. The mixed gas flows from top to bottom through the pipeline and enters the vertical reactor for reaction. The gas is preheated in the pipeline before entering the reactor using a heating belt. The preheating temperature is 60°C and the preheating time is 4 minutes. A gas distribution plate is provided in the middle of the vertical reactor. The distribution plate is hemispherical, with uniformly sized circular holes evenly distributed on the surface. The aperture of the circular hole is 0.05mm, and the distribution density of the circular holes on the gas distribution plate is 13,000 / cm 2 . A catalyst is installed on top of the distribution plate. The catalyst is located on the upper surface of the entire gas distribution plate, and the mass of the catalyst is 3 grams. The catalyst in the reactor is a CuFe alloy catalyst, which is composed of Cu and Fe. The mass ratio of Cu and Fe is 1:1. The porosity of the catalyst is 40%. The structure of the catalyst is a sponge-like three-dimensional porous structure. The particle size of the catalyst is 0.5mm. The reactor is heated by a silicon carbon rod heating furnace, and the temperature of the reactor is controlled to 200°C. The pressure is controlled by a pressure reducing valve. The pressure of the reactor is 3Mpa. The residence time of the gas in the reactor is 2 minutes. The gas after the reaction is passed into the condenser for condensation at a condensation temperature of about 50°C. The condensed gas is treated as exhaust gas or can be recycled, thereby saving gas consumption and increasing the reaction conversion efficiency of the gas. The condensed liquid is tested by chromatography to detect the methanol content and calculate the methanol selectivity and carbon dioxide conversion rate of the gas reaction process. The test results are: methanol selectivity: 89%, carbon dioxide conversion rate (single pass): 22%.

[0045] Example 2

[0046] The carbon dioxide used in this embodiment is carbon dioxide captured during steel production, wherein the carbon dioxide content is 99%, the hydrogen used is industrial hydrogen, wherein the hydrogen content is 100%, and the nitrogen used is industrial nitrogen, wherein the nitrogen content is 100%.

[0047] First, hydrogen, carbon dioxide and nitrogen are introduced into the mixer. The flow rate of hydrogen is 370ml / min and the pressure is 10Mpa. The flow rate of carbon dioxide is 110ml / min and the pressure is 9Mpa. The flow rate of nitrogen is 70ml / min and the pressure is 10Mpa. The mixed gas flows from top to bottom through the pipeline and enters the vertical reactor for reaction. The gas is preheated with a heating belt in the pipeline before entering the reactor. The preheating temperature is 65°C and the preheating time is 4.5min. A gas distribution plate is provided in the middle of the vertical reactor. The distribution plate is hemispherical, and circular holes of uniform size are evenly distributed on the surface. The aperture of the circular hole is 0.06mm, and the distribution density of the circular holes on the gas distribution plate is 13,000 / cm 2 A catalyst is installed above the gas distribution plate, covering the entire upper surface of the gas distribution plate. The catalyst weighs 3.5 grams. The catalyst in the reactor is a CuZn alloy catalyst, composed of Cu and Zn in a mass ratio of 5:6. The catalyst has a porosity of 42%, a sponge-like three-dimensional porous structure, and a particle size of 0.6 mm. The reactor is heated in a silicon carbide heating furnace at 220°C. The pressure is controlled by a pressure reducing valve at 4 MPa. The gas residence time in the reactor is 3 minutes. The reacted gas is passed into a condenser for condensation at approximately 50°C. The condensed gas is treated as exhaust gas or recycled, thereby saving gas usage and increasing gas reaction conversion efficiency. The condensed liquid is tested using chromatography to detect the methanol content and calculate the methanol selectivity and carbon dioxide conversion rate of the gas reaction process. The test results are: methanol selectivity: 84%, carbon dioxide conversion rate (single pass): 24%.

[0048] Example 3

[0049] The carbon dioxide used in this embodiment is carbon dioxide captured during steel production, wherein the carbon dioxide content is 100%, the hydrogen used is industrial hydrogen, wherein the hydrogen content is 100%, and the nitrogen used is industrial nitrogen, wherein the nitrogen content is 100%.

[0050] First, hydrogen, carbon dioxide and nitrogen are introduced into the mixer. The flow rate of hydrogen is 380ml / min and the pressure is 10Mpa. The flow rate of carbon dioxide is 130ml / min and the pressure is 9Mpa. The flow rate of nitrogen is 80ml / min and the pressure is 10Mpa. The mixed gas flows from top to bottom through the pipeline and enters the vertical reactor for reaction. The gas is preheated in the pipeline before entering the reactor using a heating belt. The preheating temperature is 65°C and the preheating time is 4.5min. A gas distribution plate is provided in the middle of the vertical reactor. The distribution plate is hemispherical, with circular holes of uniform size evenly distributed on the surface. The aperture of the circular hole is 0.07mm, and the distribution density of the circular holes on the gas distribution plate is 13500 / cm 2 A catalyst is installed on top of the distribution plate, located on the entire upper surface of the gas distribution plate, and has a mass of 4 grams. The catalyst in the reactor is a CuFe alloy catalyst, composed of Cu and Fe with a mass ratio of 3:2. The porosity of the catalyst is 50%, the structure of the catalyst is a sponge-like three-dimensional porous structure, and the particle size of the catalyst is 0.8 mm. The reactor is heated by a silicon carbon rod heating furnace, and the reactor temperature is controlled to 240°C. The pressure is controlled by a pressure reducing valve, and the pressure of the reactor is 5 MPa. The residence time of the gas in the reactor is 3 minutes. The reacted gas is passed into a condenser for condensation at a condensation temperature of approximately 50°C. The condensed gas is treated as exhaust gas or can be recycled, thereby saving gas consumption and increasing the reaction conversion efficiency of the gas. The condensed liquid is tested by chromatography to detect the methanol content and calculate the methanol selectivity and carbon dioxide conversion rate of the gas reaction process. The test results are: methanol selectivity: 79%, carbon dioxide conversion rate (single pass): 28%.

[0051] Example 4

[0052] The carbon dioxide used in this embodiment is carbon dioxide captured during steel production, wherein the carbon dioxide content is 100%, the hydrogen used is industrial hydrogen, wherein the hydrogen content is 100%, and the nitrogen used is industrial nitrogen, wherein the nitrogen content is 100%.

[0053] First, hydrogen, carbon dioxide and nitrogen are introduced into the mixer. The flow rate of hydrogen is 400ml / min and the pressure is 10Mpa. The flow rate of carbon dioxide is 150ml / min and the pressure is 9Mpa. The flow rate of nitrogen is 100ml / min and the pressure is 10Mpa. The mixed gas flows from top to bottom through the pipeline and enters the vertical reactor for reaction. The gas is preheated in the pipeline before entering the reactor using a heating belt. The preheating temperature is 70°C and the preheating time is 5min. A gas distribution plate is provided in the middle of the vertical reactor. The distribution plate is hemispherical, with circular holes of uniform size evenly distributed on the surface. The aperture of the circular hole is 0.08mm, and the distribution density of the circular holes on the gas distribution plate is 13500 / cm 2 A catalyst is installed on top of the distribution plate, located on the entire upper surface of the gas distribution plate, and has a mass of 5 grams. The catalyst in the reactor is a CuZn alloy catalyst, composed of Cu and Zn with a mass ratio of 4:3. The porosity of the catalyst is 55%, the structure of the catalyst is a sponge-like three-dimensional porous structure, and the particle size of the catalyst is 1 mm. The reactor is heated by a silicon carbon rod heating furnace, and the reactor temperature is controlled at 250°C. The pressure is controlled by a pressure reducing valve at a pressure of 5 MPa. The gas residence time in the reactor is 3 minutes. The reacted gas is passed into a condenser for condensation at a temperature of approximately 50°C. The condensed gas is treated as exhaust gas or can be recycled, thereby saving gas consumption and increasing the gas reaction conversion efficiency. The condensed liquid is tested using chromatography to detect the methanol content and calculate the methanol selectivity and carbon dioxide conversion rate of the gas reaction process. The test results are: methanol selectivity: 76%, carbon dioxide conversion rate (single pass): 33%.

[0054] Example 5

[0055] The present embodiment is carried out in the manner of Example 1, except that: the temperature of the reactor is controlled to 190 ℃, the pressure is controlled by a pressure reducing valve, the pressure of the reactor is 1.5 MPa, the residence time of the gas in the reactor is 1.5 min, the content of methanol is detected after the reaction, and the methanol selectivity and carbon dioxide conversion of the gas reaction process are calculated. The test results are: methanol selectivity: 70%, carbon dioxide conversion (one way): 20%. This result shows that under non-preferred low temperature and low pressure and reaction time conditions, the technical effect of the present invention (methanol selectivity: 70%, carbon dioxide conversion (one way): 20%) can also be achieved, although the effect is better in Example 1.

[0056] Comparative Example 1

[0057] This comparative example was conducted in the same manner as Example 2, except that the catalyst used in the reactor was a conventional ZnZrOx solid solution catalyst having a porosity of 38%, a powdered catalyst, and a particle size of 0.4 mm. After the reaction, the methanol content was measured, and the methanol selectivity and carbon dioxide conversion rate during the gas reaction were calculated. The test results were: methanol selectivity: 62%, and carbon dioxide conversion rate (single pass): 13%.

[0058] Comparative Example 2

[0059] This comparative example was conducted in the same manner as Example 3, except that the catalyst used in the reactor had a porosity of 58% and a particle size of 1.2 mm. The methanol content was measured after the reaction, and the methanol selectivity and carbon dioxide conversion during the gas reaction were calculated. The test results were: methanol selectivity: 68%, and carbon dioxide conversion (single pass): 18%.

[0060] Comparative Example 3

[0061] This comparative example was conducted in the same manner as Example 3, except that the catalyst used in the reactor had a porosity of 35% and a particle size of 0.4 mm. The methanol content was measured after the reaction, and the methanol selectivity and carbon dioxide conversion during the gas reaction were calculated. The test results showed a methanol selectivity of 65% and a carbon dioxide conversion (single-pass) of 12%.

[0062] It should be noted that all technical features described in the present invention can be freely combined or combined in any way unless there is a contradiction between them. Various modifications and variations can be made to the present invention without departing from the scope of the present invention, which will be apparent to those skilled in the art. For example, a feature shown or described as part of one embodiment can be used together with another embodiment to produce yet another embodiment. Therefore, the present invention is intended to cover these modifications that fall within the scope of the appended claims and their equivalents.

Claims

1. A method for producing methanol using carbon dioxide, wherein: The method comprises the following steps performed in sequence: (1) introducing carbon dioxide gas and hydrogen gas into a mixer and mixing them in the mixer to obtain a mixed gas; (2) passing the mixed gas downward into a reactor having a catalyst and contacting the mixed gas with the catalyst in the reactor, so that the carbon dioxide gas and hydrogen in the mixed gas react in the presence of the catalyst to obtain a product containing methanol; as well as (3) condensing the product containing methanol to achieve gas-liquid separation, thereby obtaining a liquid containing methanol and a condensed gas; Wherein, the catalyst is selected from CuFe alloy catalyst and CuZn alloy catalyst, the CuFe alloy catalyst is composed of Cu and Fe, and the mass ratio of Cu to Fe is 1:1 to 3:2; the CuZn alloy catalyst is composed of Cu and Zn, and the mass ratio of Cu to Zn is 5:6 to 4:3; preferably, the catalyst has a porosity of 40-55%, a particle size of 0.5-1 mm, and a sponge-like three-dimensional porous structure.

2. The method according to claim 1, wherein The method further comprises a step (1') between step (1) and step (2): preheating the mixed gas obtained in step (1); preferably, the preheating temperature is 60-70°C, and the preheating time is 4-5 minutes; preferably, the preheating is achieved by heating the mixed gas in a pipe that passes the mixed gas into the reactor.

3. The method according to claim 1 or 2, wherein: In the step (2), the reaction is carried out under the following conditions: reaction pressure ≥3 MPa, preferably 3-10 MPa; reaction temperature ≥200° C., preferably 200-250° C.; reaction time ≥2 min, preferably 2-10 min.

4. The method according to any one of claims 1 to 3, wherein In step (1), the flow rate of the carbon dioxide gas is 100-150 ml / min, preferably, the pressure of the carbon dioxide gas is 8-10 MPa, and preferably, the volume percentage content of carbon dioxide in the carbon dioxide gas is more than 95%; the flow rate of the hydrogen gas is 350-400 ml / min, preferably, the pressure of the hydrogen gas is 9-11 MPa; preferably, the volume percentage content of the hydrogen gas is 100%.

5. The method according to any one of claims 1 to 4, wherein The step (1) further comprises introducing an inert gas into the mixer to mix the inert gas with carbon dioxide gas and hydrogen; preferably, the flow rate of the inert gas is 50-100 ml / min; preferably, the pressure of the inert gas is 9-11 MPa; preferably, the inert gas is nitrogen.

6. The method according to any one of claims 1 to 5, wherein The reactor in step (2) is a vertical reactor; preferably, a gas distribution plate with circular holes is provided in the vertical reactor, and the catalyst is provided on the gas distribution plate; preferably, the gas distribution plate is a hemispherical distribution plate; preferably, the aperture of the circular holes is 0.05-0.08 mm; preferably, the circular holes are of equal size; preferably, the mass of the catalyst is 3-5 grams.

7. The method according to any one of claims 1 to 6, wherein The method further comprises step (4): treating the gas obtained after condensation as tail gas or recycling it, and detecting the content of methanol in the liquid.

8. The method according to any one of claims 1 to 7, wherein The selectivity of methanol is ≥70%, preferably, the selectivity of methanol is ≥75%; the conversion rate of carbon dioxide is ≥20%, preferably, the conversion rate of carbon dioxide is ≥22%.

9. A device for producing methanol, comprising a mixer, a reactor and a condenser connected in sequence, wherein: The mixer is used to mix carbon dioxide gas, hydrogen and an optional inert gas to obtain a mixed gas; the reactor is equipped with a catalyst, and in the reactor, the carbon dioxide gas in the mixed gas reacts with the hydrogen in the presence of the catalyst to obtain a product containing methanol; and in the condenser, the product containing methanol is condensed to achieve gas-liquid separation, thereby obtaining a liquid containing methanol and a condensed gas.

10. The device according to claim 9, wherein The device satisfies one or more of the following conditions: 1) The mixed gas in the mixer is passed downward into the reactor through a pipe, and a heating belt is set in the pipe to heat the mixed gas in the pipe to 60-70°C; 2) The reactor is a vertical reactor, wherein a gas distribution plate with circular holes is provided in the vertical reactor, and the catalyst is provided on the gas distribution plate; preferably, the gas distribution plate is a hemispherical distribution plate; preferably, the diameter of the circular holes is 0.05-0.08 mm; preferably, the circular holes are of equal size; preferably, the mass of the catalyst is 3-5 grams; 3) The catalyst is selected from a CuFe alloy catalyst and a CuZn alloy catalyst, wherein the CuFe alloy catalyst is composed of Cu and Fe, and the mass ratio of Cu to Fe is 1:1 to 3:2; the CuZn alloy catalyst is composed of Cu and Zn, and the mass ratio of Cu to Zn is 5:6 to 4:3; preferably, the catalyst has a porosity of 40-55%, a particle size of 0.5-1 mm, and a sponge-like three-dimensional porous structure; 4) The reaction is carried out at a pressure of 3 MPa or more, preferably 3-10 MPa, and a temperature of 200° C. or more, preferably 200-250° C., for more than 2 minutes, preferably 2-10 minutes.

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