A method and system for producing methanol by electrolysis of water-coal slurry coupled with CO2 electrolysis reduction

Abstract

The present invention discloses a method and system for producing methanol by electrolyzing water-coal slurry coupled with CO2 electrolytic reduction, belonging to the technical field of methanol preparation. The method comprises the preparation of water-coal slurry, electrolysis of water-coal slurry, and electrolytic reduction of CO2. Compared with the traditional coal-to-methanol method, the reaction conditions of this method are relatively mild, which reduces the requirements for equipment, and reduces the floor space and investment costs. On the one hand, the carbon dioxide generated during the electrolysis of water-coal slurry can be effectively utilized to avoid its direct discharge into the atmosphere; on the other hand, through the coupling system, the electrolysis of water-coal slurry can reduce the energy consumption of the anode reaction, while utilizing carbon dioxide reduction to achieve the conversion from greenhouse gas to useful energy and chemicals, with zero CO2 product, providing a new and effective way to solve environmental problems and energy crises.

Description

Technical Field

[0001] The present invention belongs to the technical field of methanol preparation, and in particular relates to a method and system for preparing methanol by coupling electrolysis of water-coal slurry with CO2 electrolysis reduction. Background Art

[0002] Methanol, as an important chemical raw material, has a wide range of applications in the energy, chemical, and pharmaceutical sectors. It can be used as a fuel for vehicles, ships, and other transportation vehicles, and as a chemical raw material for the production of chemicals such as formaldehyde and acetic acid. Furthermore, methanol has significant economic and social value as a solvent and antifreeze agent.

[0003] Due to my country's distinct resource characteristics of being "poor in oil, low in natural gas, and rich in coal," coal has long been a core component of its energy structure. Traditional methanol production methods primarily utilize coal and include the following steps: First, coal gasification, where coal reacts with a gasifying agent (such as oxygen or water vapor) at high temperatures to produce a crude gas primarily composed of carbon monoxide (CO) and hydrogen (H2); followed by synthesis gas purification, where the crude gas is treated to remove impurities such as sulfides and carbon dioxide; followed by synthesis gas shift, where carbon monoxide is converted to carbon dioxide through a shift reaction while increasing the hydrogen content to meet the requirements for methanol synthesis; followed by methanol synthesis, where the purified synthesis gas is contacted with a catalyst at a specific temperature and pressure to undergo a methanol synthesis reaction. The resulting methanol gas is cooled and condensed to produce liquid methanol; finally, methanol distillation, where the liquid methanol is distilled to remove impurities and moisture, resulting in a high-purity methanol product.

[0004] Chinese invention patent application No. 202311047619.3 discloses a coal-to-methanol production system, specifically comprising a gasification unit, a shift converter, a low-temperature methanol scrubber, and a sulfur recovery unit. The gasification unit includes a sealed water pump and gasification equipment; the sulfur recovery unit includes a sulfur recovery scrubber; and the shift converter includes a spray water cooler and a shift converter separator. This invention addresses the issues of ammonia nitrogen separation and wastewater treatment in shift converter gas without requiring additional equipment.

[0005] Chinese invention patent application No. 202310662322.1 discloses a coal-to-methanol device and method, specifically utilizing a coal gasification unit, a scrubbing and cooling unit, a water-gas shift unit, a low-temperature methanol scrubbing unit, and a first methanol synthesis unit. The coal inlet of the coal gasification unit is connected to a coal source, the oxygen inlet of the coal gasification unit is connected to an oxygen source, the carbon dioxide gas outlet of the low-temperature methanol scrubbing unit is connected to a reforming system, and the carbon dioxide gas inlet of the carbon dioxide dry reforming unit in the reforming system is connected to the carbon dioxide gas outlet of the low-temperature methanol scrubbing unit, and the outlet is connected to a scrubbing and purification unit. The outlet of the scrubbing and purification unit is connected to a second methanol synthesis unit. By introducing methane-carbon dioxide dry reforming, utilizing natural gas energy and captured carbon dioxide for a reforming reaction, and then combining it with green hydrogen produced from renewable energy to reconstitute the synthesis gas and produce methanol, the carbon dioxide generated in the traditional coal-to-methanol process is utilized as a resource, significantly reducing carbon dioxide emissions and increasing methanol production.

[0006] As mentioned above, existing methanol production methods primarily rely on coal. However, traditional coal-to-methanol methods have several drawbacks. First, the production conditions and processes are complex, requiring harsh reaction conditions such as high temperature and high pressure, and involving multiple process steps, making them difficult to operate. Second, the equipment required for this method occupies a large area, resulting in high investment costs. Furthermore, the traditional coal-to-methanol process is energy-intensive and consumes a lot of energy, making it unsuitable for sustainable development. Summary of the Invention

[0007] To address the complex production process, large equipment footprint, high investment costs, and high energy consumption associated with traditional coal-to-methanol methods, this invention provides a method for producing methanol by electrolyzing coal-water slurry coupled with CO2 electrolytic reduction. This method not only avoids CO2 emissions from electrolyzing coal-water slurry but also achieves low-energy CO2 conversion, producing a high-value-added product.

[0008] The purpose of the present invention is achieved through the following technical solutions:

[0009] A method for producing methanol by electrolysis of water-coal slurry coupled with CO2 electrolytic reduction comprises the following steps:

[0010] Step 1: Preparation of coal water slurry

[0011] (1) Crushing, grinding, and screening raw coal to obtain fine coal powder;

[0012] (2) dissolving coal powder in an acid solution to obtain a coal-water slurry;

[0013] In this step, the raw coal is lignite;

[0014] In this step, the particle size of the coal powder is below 200 mesh (74 μm);

[0015] In this step, the acid solution is a sulfuric acid solution with a concentration of 0.5-3 mol / L, preferably 1 mol / L. If the concentration is too low, the current density is low, and if the concentration is too high, the corrosion to the electrode is high.

[0016] In this step, the coal slurry content of the water-coal slurry is 25-50 g / L;

[0017] Step 2: Electrolysis of water-coal slurry

[0018] (1) Using the water-coal slurry in step 1 as the anolyte, and an acid solution as the catholyte, a proton exchange membrane (PEM) and an H-type electrolytic cell are used to form an electrolytic hydrogen production device;

[0019] (2) Electrolysis is carried out under the conditions of an electrolysis voltage of less than 1.23 V, a temperature of 60 to 80° C., and a stirring rate of 400 to 800 r / min.

[0020] In this step, the proton exchange membrane is a Nafion 177 proton exchange membrane;

[0021] In this step, the temperature control method is water bath heating, oil bath heating or platform contact heating;

[0022] In this step, the stirring method is magnetic stirring or mechanical stirring;

[0023] In this step, the cathode material used can be Cu2O, RuO2, TiO2, MOF material, etc.

[0024] Step 3: Electrolytic reduction of CO2

[0025] As the reaction in step 2 proceeds, the CO2 produced at the anode or the added CO2 is introduced into the cathode, and the CO2 is reduced to methanol under the action of the electrode.

[0026] In this step, the collected CO2 produced by the anode is introduced into the cathode electrolyte through an air pump;

[0027] In this step, CO2 can also be directly added into the cathode electrolyte.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. Reduced reaction condition requirements: Compared with the traditional coal-to-methanol process, the reaction conditions of this technology are mild, and no high temperature and high pressure operation is required, which reduces the requirements for equipment, investment costs and floor space.

[0030] 2. Reduced energy consumption: By coupling the electrolysis of water-coal slurry with the reduction of CO2 to methanol, the energy consumption of the anode reaction can be reduced, and the CO2 resources generated during the electrolysis process can be rationally utilized, thereby improving the reaction efficiency and significantly reducing the total energy consumption of methanol synthesis.

[0031] 3. Realize the recycling of CO2: This method not only avoids the direct emission of CO2 into the atmosphere, but also uses CO2 as a reactant to generate methanol, realizing the recycling of CO2, converting greenhouse gases into high-value-added energy and chemicals, and solving the carbon emission problem.

[0032] 4. Reduced environmental pollution: During the reaction, CO2 is no longer emitted as waste gas. Instead, it is reduced to methanol, eliminating environmental pollution. Furthermore, some of the carbon in the coal remains as organic products, while elements such as nitrogen and sulfur are precipitated as acids, reducing pollution emissions and enhancing environmental friendliness.

[0033] 5. Wide adaptability to coal quality: This technology has low requirements on coal quality and can be applied to a variety of coal types (such as oil shale, low-rank coal, lignite, medium-rank coal, etc.), which increases the applicability of the process and further enhances the operability and promotion potential of the technology.

[0034] 6. Sustainable development and economic benefits: This method not only reduces dependence on traditional fossil fuels, but also efficiently converts resources into useful products, with long-term sustainability and economic benefits.

[0035] Through these beneficial effects, this technology provides new directions and effective solutions for the efficient, clean and sustainable utilization of coal. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0037] Figure 1 Schematic diagram of the method for producing methanol by electrolyzing water-coal slurry coupled with CO2 electrolytic reduction provided by the present invention.

[0038] Among them, 1-H type electrolytic cell, 2-proton exchange membrane, 3-anode, 4-cathode. DETAILED DESCRIPTION

[0039] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0040] Example 1: A method for producing methanol by electrolysis of coal-water slurry coupled with CO2 electrolysis and reduction

[0041] The specific steps are:

[0042] Step 1: Preparation of fine coal powder: crush, grind and screen the raw coal in sequence to obtain fine coal powder with a particle size of less than 200 mesh.

[0043] Step 2: Preparation of anolyte: Dissolve 2.4 g of fine coal powder obtained in step 1 in 80 ml of 1 mol / L sulfuric acid solution and ultrasonicate for 30 min to obtain water-coal slurry as anolyte.

[0044] Step 3: Preparation of catholyte: Take 80 mL of sulfuric acid solution with the same concentration as in step 2 as the catholyte.

[0045] Step 4: Electrolysis of water-coal slurry: Add the anolyte and catholyte into the anode chamber and cathode chamber of the electrolytic cell respectively, using a 1×1 cm 2 The platinum electrode was used as the anode, 1×1 cm 2 The Cu2O sheet was used as the cathode, and electrolysis was carried out under the conditions of electrolysis voltage less than 1.23V, temperature of 70-80℃, and stirring rate of 400-800r / min.

[0046] The experiment found that when the electrolysis voltage is greater than 1.23, an electrolysis reaction of water will occur; when the temperature is low, the reaction rate is greatly reduced, and the proton exchange membrane is not resistant to high temperatures, so the temperature should not be exceeded; if the stirring rate is too low, the stirring effect is poor and the dispersion effect cannot be achieved. After reaching 400r / min, different stirring rates have little effect on the reaction.

[0047] Step 5, CO2 reduction: The CO2 generated at the anode in step 4 is transferred to the cathode electrolyte through a gas pump, and CO2 is reduced to methanol under the action of the electrode.

[0048] In step 4, the CO2 content produced at the anode is more than 90%, containing a small amount of CO. CO will also be partially converted into methanol at the cathode and does not need to be separated.

[0049] Steps 4 and 5 are performed simultaneously and continuously.

[0050] When methanol is prepared by this method, the conversion rate of CO2 into methanol is about 80%.

[0051] Example 2: Method for producing methanol by electrolyzing coal-water slurry coupled with CO2 electrolytic reduction provided in Example 1

[0052] In step 1, the raw coal is one or more of lignite, bituminous coal, and anthracite, meaning the method is applicable to all types of coal. Comparative experiments have shown that the type of coal has little impact on the conversion rate, remaining around 80%. Lower-cost coal types, such as low-rank coal, are prioritized.

[0053] Example 3: A system for producing methanol by electrolysis of coal-water slurry coupled with CO2 electrolysis reduction

[0054] like Figure 1 As shown, the device comprises an H-type electrolytic cell 1, a proton exchange membrane 2 disposed within the H-type electrolytic cell 1, an anode 3, and a cathode 4. The proton exchange membrane 2 separates the electrolytic cell into a cathode cell and an anode cell. The cathode cell contains a sulfuric acid solution as the catholyte, while the anode cell contains a water-coal slurry as the anolyte. Platinum is used as the anode material; a Cu2O electrode is used as the cathode material. A temperature control system is included to control the electrolyte temperature. The proton exchange membrane is a Nafion 177 proton exchange membrane; and a stirring device is included to stir the electrolyte.

[0055] Example 4: The platinum electrode in the system for producing methanol by electrolysis of water-coal slurry coupled with CO2 electrolysis reduction provided in Example 2 can be replaced by electrodes made of other materials that undergo hydrogen evolution reaction.

[0056] Example 5: A system for producing methanol by coupling electrolysis of water-coal slurry with CO2 electrolysis reduction provided in Example 2

[0057] In this embodiment, the temperature control system can be a water bath device, electric heating tape, oil bath or electric heating wire, etc., and the temperature of the electrochemical reaction device is controlled by water bath heating, heating tape heating, oil bath heating or platform contact heating.

[0058] Example 6: A system for producing methanol by coupling electrolysis of water-coal slurry with CO2 electrolysis and reduction provided in Example 2

[0059] The stirring method is a magnetic stirring device or a mechanical stirring device respectively arranged in the anode pool and the cathode pool.

[0060] Example 7: A system for producing methanol by coupling electrolysis of water-coal slurry with CO2 electrolysis and reduction provided in Example 2

[0061] The Cu2O electrode can be replaced by electrodes made of other materials that undergo CO2 reduction reaction, such as RuO2, TiO2, MOF materials, etc.

[0062] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for producing methanol by electrolysis of coal-water slurry coupled with CO2 electrolytic reduction, characterized in that: The steps include: Step 1: Preparation of coal-water slurry: (1) Crushing, grinding and screening the raw coal to obtain fine coal powder; (2) dissolving coal powder in an acid solution to obtain a water-coal slurry; Step 2: Electrolysis of water-coal slurry: (1) Using the water-coal slurry in step 1 as the anolyte, and an acid solution as the catholyte, a proton exchange membrane and an H-type electrolytic cell are used to form an electrolytic hydrogen production device; (2) electrolysis is performed under the conditions of an electrolysis voltage of less than 1.23 V, a temperature of 60 to 80° C., and a stirring rate of 400 to 800 r / min; Step 3: Electrolytic reduction of CO2: As the reaction in step 2 proceeds, the CO2 produced at the anode is passed into the cathode, and the CO2 is reduced to methanol under the action of the electrode.

2. The method according to claim 1, characterized in that In step 1, the raw coal is selected from one or more of lignite, bituminous coal, and anthracite.

3. The method according to claim 1, characterized in that In step 1, the particle size of the coal powder is below 200 mesh.

4. The method according to claim 1, wherein In step 1, the acid solution is a sulfuric acid solution with a concentration of 0.5-3 mol / L.

5. The method according to claim 1, characterized in that In step 1, the coal slurry content of the water-coal slurry is 25-50 g / L.

6. The method according to claim 1, characterized in that In step three, the collected CO2 generated at the anode is introduced into the cathode electrolyte through an air pump.

Images