Method for silicon dioxide reinforced gas-liquid micro-interface carbon dioxide reduction

Abstract

The invention belongs to the field of CO2 resource utilization, and relates to a silicon dioxide reinforced gas-liquid micro-interface carbon dioxide reduction method. According to the method, a stable gas-liquid micro-interface is constructed between gas-phase CO2 and dispersion liquid containing nano silicon dioxide, so that a gas-liquid-solid three-phase interface with high reaction activity is formed. On the interface, CO2, electrons and hydroxyl groups on the surface of silicon dioxide are subjected to hydrogenation reaction, and efficient reduction of CO2 at normal temperature and normal pressure is achieved. The technology obviously enhances the adsorption, activation and hydrogenation efficiency of CO2, and realizes efficient conversion to generate C1 and C2 high value-added chemicals, such as formic acid, acetic acid, methanol and ethanol. The method does not need high-temperature and high-pressure conditions, is simple to operate, low in energy consumption, green and environment-friendly, and has a good application prospect.

Description

Technical Field

[0001] The present invention belongs to CO 2 The invention relates to the field of resource utilization and relates to a method for reducing carbon dioxide at a gas-liquid microinterface enhanced by silicon dioxide. Background Art

[0002] CO 2 Emissions are increasing year by year, leading to global warming, ocean acidification and other problems. 2 Hydrogenation conversion can not only alleviate environmental problems, but also produce high value-added products through hydrogenation resources. 2 Thermodynamically highly stable, often requires harsh conditions such as high temperature and high pressure, resulting in high operating costs and additional energy consumption. 2 Hydrogenation can be used to activate CO at room temperature using an external electric field 2 , producing a variety of products with industrial value, such as formic acid, etc. However, the high overpotential and large mass transfer resistance reduce the energy efficiency.

[0003] The strong electric field at the gas-liquid interface of microdroplets provides a new electrochemical environment for charged droplets, making them an emerging platform for chemical reactions. Compared with the main liquid phase solution, micron-sized droplets can significantly accelerate gas-liquid interface reactions, and some reaction rates can be accelerated to one million times the original. The main reason is the unique physical and chemical properties of the gas-liquid microinterface, such as: ultra-high electric field, oriented reaction molecules / intermediate species, etc. Without adding any catalysts and without an external electric field, molecules can be induced to undergo oxidation or reduction reactions. In recent years, researchers have also conducted research on gas-water microbubbles, producing gas-liquid microinterfaces with similar effects.

[0004] Gas-liquid microinterfaces have been shown to enable CO 2 Hydrogenation reduction. Using high purity CO 2 As carrier gas, nebulize 1,2,3-triazole aqueous solution, CO 2 It can be captured by triazole enriched on the interface and then reduced to formic acid by hydrogenation; the atomized metal-based molecular catalyst Cu II (phen) 2 aqueous solution, which can promote the multi-electron CO 2 Reduction and CC coupling synthesize multi-carbon products such as ethanol. 2 It shows great potential in reduction, but is still in its early stages of development and faces challenges such as low hydrogenation yield. Summary of the invention

[0005] The present invention provides a silicon dioxide enhanced gas-liquid micro-interface CO 2 This method involves reducing 2A stable gas-liquid micro-interface is constructed between the nano-silicon dioxide dispersion and the dispersion to form a highly reactive gas-liquid-solid three-phase interface. 2 The hydrogenation reaction occurs with electrons and the hydroxyl groups on the surface of silica to achieve CO 2 Highly efficient reduction at room temperature and pressure. This technology effectively improves CO 2 The adsorption, activation and hydrogenation efficiency can efficiently generate C 1 and C 2 It can produce a variety of high value-added chemicals, such as formic acid, acetic acid, methanol and ethanol, while having the advantages of being green, environmentally friendly, easy to operate and low energy consumption.

[0006] The technical solution of the present invention:

[0007] A method for silicon dioxide-enhanced gas-liquid microinterface carbon dioxide reduction, wherein the method comprises the following steps: 2 A stable gas-liquid micro-interface is constructed between the dispersion containing nano-sized silica, thereby forming a highly active gas-liquid-solid three-phase interface with an ultra-high specific surface area. 2 The hydrogenation reaction occurs with electrons and the polyhydroxyl groups on the surface of silicon dioxide to achieve CO 2 Efficient reduction at room temperature and pressure to generate C 1 and C 2 A variety of high value-added chemicals such as formic acid, acetic acid, methanol and ethanol.

[0008] The preparation method of the liquid phase silica dispersion is as follows: adding silica particles into a dispersion medium, breaking agglomeration by stirring or ultrasonic treatment, wherein the silica configuration mass fraction is 0-20%; the average size of the silica particles is 1-1000nm; the dispersion medium includes one or more of water, ethanol, methanol, isopropanol, acetonitrile, acetone, and ethyl acetate;

[0009] The silicon dioxide particles include crystalline silicon dioxide, amorphous or semi-amorphous silicon dioxide, functionalized silicon dioxide (such as doped or surface-modified silicon dioxide), and natural minerals containing silicon dioxide (such as quartz, opal, diatomaceous earth, montmorillonite, kaolin, illite, chlorite, etc.);

[0010] The gas-liquid micro-interface is generated in two ways: one is through a micro-droplet generation device, in the gas phase CO 2 One method is to generate micron-sized droplets in a liquid phase silica dispersion by a microbubble generating device; the size of the microdroplets or microbubbles is 0.1-1000μm; the generating device supports the regulation of the size and number of the microdroplets or microbubbles.

[0011] The micro-droplet generation methods include: pneumatic spray, ultrasonic atomization, electrostatic spray, condensation atomization; the micro-bubble generating device includes a reactor and a CO placed at the bottom of the reactor. 2 Nebulizer, CO 2 The gas enters the liquid through the atomizer, which can produce micro bubbles with high specific surface area;

[0012] The carbon dioxide reduction reaction can be further improved by optimizing the reaction conditions. 2 The reaction conditions include: solution pH, silica concentration and size, reaction gas purity, micro-droplet or micro-bubble size and quantity, reaction time, reaction temperature, electrolyte type and concentration.

[0013] The beneficial effects of the present invention are:

[0014] By coupling nano-silicon dioxide with the gas-liquid micro-interface, a gas-liquid-solid three-phase interface with ultra-high specific surface area and high reactivity is constructed to make CO 2 Highly efficient hydrogenation reduction is achieved at room temperature and pressure to generate C 1 and C 2 High value-added chemicals such as CO 2 Unlike the silica used as a catalyst carrier in hydrogenation technology, the hydroxyl groups on the surface of silica in this method can provide hydrogen free radicals (H·) to directly participate in the CO 2 This method overcomes the traditional CO 2 The technical bottlenecks of the hydrogenation process are large mass transfer resistance and high energy consumption. The entire reaction process is green and environmentally friendly, energy-saving and highly efficient, showing good prospects for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The ultrasonic atomization CO used in Example 1 of the present invention 2 Diagram of the hydrogenation unit.

[0016] Figure 2 This is the mass spectrum of the product after 1 hour of reaction in Example 1 of the present invention.

[0017] Figure 3 It is the total product concentration at different reaction times in Example 1 of the present invention. DETAILED DESCRIPTION

[0018] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0019] Embodiment 1:

[0020] An ultrasonic atomization device was used to generate micro droplets, with an ultrasonic frequency of 3.0 MHz and a power of 20 W. The reaction liquid was a nano-silicon dioxide (~100 nm)-ultrapure water dispersion. 30.04 mg of nano-silicon dioxide powder was mixed with 500 mL of ultrapure water and ultrasonicated for about 15 minutes to evenly disperse the silicon dioxide in the ultrapure water to form a 1.0 mmol / L dispersion. 10 mL was taken as the reaction liquid. After the reaction liquid was added to the reactor, the device was sealed, and the gas in the reactor was extracted and filled with high-purity CO by alternating multiple times. 2 , complete the gas replacement, so that the reactor is filled with high-purity CO 2 . Turn on the ultrasonic atomizer power supply to form highly active micro droplets, CO 2 A reduction reaction occurs at the gas-liquid microinterface at room temperature and pressure. After 0.5 hours, 1 hour, 2 hours, 3 hours, 7 hours, 9 hours, and 10 hours of reaction, the atomizer was turned off and the solution was taken out for product detection. Mass spectrometry results showed that the products included methanol, ethanol, formic acid, and acetic acid. The results of ion chromatography and gas chromatography showed that as the reaction time increased to 1 hour, the total concentration of the product quickly rose to 218.89 μmol / L, of which formic acid was 108.67 μmol / L, acetic acid was 45.93 μmol / L, methanol was 32.12 μmol / L, and ethanol was 32.17 μmol / L. Further increasing the reaction time to 7 hours, the total concentration slowly increased to 243.71 μmol / L.

[0021] Comparative Example 1:

[0022] Ultrasonic atomization device was used to generate micro droplets, with an ultrasonic frequency of 3.0 MHz and a power of 20 W. Ultrapure water was used as the reaction liquid. After 10 mL of reaction liquid was added to the reactor, the reactor was sealed and the gas in the reactor was extracted and filled with high-purity CO by alternating multiple times. 2 , complete the gas replacement, so that the reactor is filled with high-purity CO 2 . Turn on the ultrasonic atomizer power supply to form highly active micro droplets, CO 2 The reduction reaction began to occur at the gas-liquid microinterface. After 1 hour of reaction, the atomizer was turned off and the reaction solution was taken out for testing. The results of ion chromatography showed that the formic acid content was 3.78 μmol / L and the acetic acid content was 4.85 μmol / L; the results of gas chromatography showed that the methanol content was 1.64 μmol / L and the ethanol content was 1.07 μmol / L. The total product concentration was only 11.34 μmol / L.

[0023] Figure 2 The mass spectrum of the product after 1 hour of reaction in Example 1 of the present invention. When the nano-silicon dioxide-ultrapure water dispersion is used as the atomizing solution, formic acid, acetic acid, methanol and ethanol can be produced. Figure 3It is the total product concentration at different reaction times in Example 1 of the present invention. It can be seen that as the reaction time increases to 1 h, the total product concentration increases rapidly to 218.89 μmol / L, and further increases the reaction time to 7 hours, and the total concentration slowly increases to 243.71 μmol / L.

[0024] Embodiment 2:

[0025] An ultrasonic atomization device was used to generate micro droplets, with an ultrasonic frequency of 2.4 MHz and a power of 15 W. The reaction liquid was a montmorillonite-ultrapure water dispersion. Montmorillonite powder containing silicon dioxide (particle diameter 0.5-1.25 mm) was mixed with ultrapure water and ultrasonicated for about 20 minutes to form a uniform dispersion of 100.0 mmol / L. 10 mL was taken as the reaction liquid. After the reaction liquid was added to the reactor, the reactor was sealed, and the gas in the reactor was extracted and filled with high-purity CO by alternating multiple times. 2 , complete the gas replacement, so that the reactor is filled with high-purity CO 2 . Turn on the ultrasonic atomizer power supply to form highly active micro droplets, CO 2 A reduction reaction occurred at the gas-liquid microinterface at room temperature and pressure. After 40 minutes of reaction, the atomizer was turned off and the product was tested. The results of ion chromatography showed that the formic acid content was 52.44 μmol / L and the acetic acid content was 128.81 μmol / L.

[0026] Embodiment 3:

[0027] Using CO 2 The atomizer produces microbubbles in the liquid phase, and the reaction liquid is a nano-silicon dioxide (~100nm)-ultrapure water dispersion with a concentration of 10mmol / L. 2 The nebulizer was installed at the bottom of the 100 mL reactor and connected to the CO 2 25 mL of reaction solution was added to the reactor, and then the CO 2 The gas cylinder is adjusted to 0.1 MPa by the pressure reducing valve. The atomizer begins to produce a large amount of micron-sized CO in the solution. 2 Bubbles. CO is continuously introduced into the reactor. 2 After 3 hours of reaction, stop introducing gas, wait until the bubbles disappear completely, take out the solution for product detection. The results of ion chromatography showed that the concentration of formic acid was 3.33 μmol / L and the concentration of acetic acid was 113.93 μmol / L.

[0028] The above embodiments are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions and reaction devices belonging to the present invention belong to the protection scope of the present invention. For ordinary technicians, improvements and modifications without departing from the principles and experimental schemes of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for reducing carbon dioxide at a gas-liquid microinterface enhanced by silicon dioxide, characterized in that: By constructing a stable gas-liquid microinterface between gaseous CO2 and a dispersion containing nano-sized silica, a highly active gas-liquid-solid three-phase interface with an ultra-high specific surface area is formed; at this three-phase interface, CO2 undergoes hydrogenation reaction with electrons and the polyhydroxy groups on the surface of silica, achieving efficient reduction of CO2 at room temperature and pressure to generate C1 and C2 high-value-added chemicals.

2. The method for reducing carbon dioxide at a gas-liquid microinterface enhanced by silicon dioxide as claimed in claim 1, characterized in that: The preparation method of the liquid phase silica dispersion is as follows: adding silica particles into a dispersion medium, breaking agglomeration by stirring or ultrasonic treatment, the silica configuration mass fraction is 0-20%; the average size of the silica particles is 1-1000nm; the dispersion medium includes one or more of water, ethanol, methanol, isopropanol, acetonitrile, acetone, and ethyl acetate.

3. The method for reducing carbon dioxide at a gas-liquid microinterface enhanced by silicon dioxide as claimed in claim 2, characterized in that: The silicon dioxide particles include crystalline silicon dioxide, amorphous or semi-amorphous silicon dioxide, functionalized silicon dioxide, and natural minerals containing silicon dioxide.

4. The method for reducing carbon dioxide at a gas-liquid microinterface enhanced by silicon dioxide as claimed in claim 1, characterized in that: The gas-liquid micro-interface is generated in two ways: one is to generate micron-sized droplets in gas phase CO2 through a micro-droplet generating device; the other is to generate micron-sized bubbles in liquid phase silica dispersion through a micro-bubble generating device; the size of the micro-droplets or micro-bubbles is 0.1-1000μm; the generating device supports the regulation of the size and quantity of the micro-droplets or micro-bubbles.

5. The method for reducing carbon dioxide at a gas-liquid microinterface enhanced by silicon dioxide as claimed in claim 4, characterized in that: The micro-droplet generation methods include: pneumatic spray, ultrasonic atomization, electrostatic spray, and condensation atomization; the micro-bubble generating device includes a reactor and a CO2 atomizer placed at the bottom of the reactor, and the CO2 gas enters the liquid through the atomizer to generate micro-bubbles with a high specific surface area.

6. The method for reducing carbon dioxide at a gas-liquid microinterface enhanced by silicon dioxide as claimed in claim 3, characterized in that: The functionalized silicon dioxide is selected from doped or surface-modified silicon dioxide.

7. The method for reducing carbon dioxide at a gas-liquid microinterface enhanced by silicon dioxide as claimed in claim 3, characterized in that: The natural minerals containing silicon dioxide are selected from quartz, opal, diatomaceous earth, montmorillonite, kaolin, illite and chlorite.

8. The method for reducing carbon dioxide at a gas-liquid microinterface enhanced by silicon dioxide as claimed in claim 1, characterized in that: The carbon dioxide reduction reaction further improves the hydrogenation efficiency of CO2 by optimizing the reaction conditions; the reaction conditions include: solution pH, silica concentration and size, reaction gas purity, microdroplet or microbubble size and number, reaction time, reaction temperature, electrolyte type and concentration.

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