METHOD AND SYSTEM FOR METHANOL SYNTHESIS VIA PLASMA-OXYGEN CARRIER-CATALYSIS COUPLING

Abstract

A method and a system for methanol synthesis via plasma-oxygen carrier-catalysis coupling provided. CO.sub.2 is activated and decomposed using an enhanced vibrational-state atmospheric-pressure plasma jet, while H.sub.2O is dissociated by utilizing the heat generated in the plasma environment. An integrated oxygen carrier captures the O.sub.2 produced from the decomposition of CO.sub.2 and H.sub.2O, facilitating forward reactions and enabling the in-situ capture of O.sub.2 from the gas products. This process yields oxygen-free syngas (CO and H.sub.2), which is then efficiently and selectively converted into methanol over a NiGa catalyst at atmospheric pressure. This configuration achieves an orderly conversion of carbon and hydrogen from CO.sub.2 and H.sub.2O into liquid methanol under atmosphere pressure, characterized by high reactant conversion and energy efficiency. Additionally, this method and system support the use of intermittent and distributed renewable energy sources due to their fast on-off capability, high reaction rate, and simple design features.

Claims

1. A method for methanol synthesis by plasma-oxygen carrier-catalysis coupling, comprising: CO.sub.2 decomposition: activating CO.sub.2 using an enhanced vibrational-state atmospheric-pressure plasma jet, so that the CO.sub.2 is decomposed into O.sub.2 and CO; H.sub.2O decomposition: decomposing H.sub.2O into O.sub.2 and H.sub.2 by the high temperature generated in the plasma working environment; Capturing O.sub.2 by an oxygen carrier: using a high-temperature oxygen carrier to absorb the decomposition product O.sub.2 in a CO.sub.2 decomposition reaction zone and a H.sub.2O decomposition reaction zone respectively, so as to separate the O.sub.2 from the decomposition product and obtain oxygen-free CO and H.sub.2 respectively; Synthesis of methanol: using a NiGa catalyst to facilitate the selective synthesis of methanol from oxygen-free CO and H.sub.2 at atmospheric pressure.

2. The method for methanol synthesis by plasma-oxygen carrier-catalysis coupling according to claim 1, wherein in the step of CO.sub.2 decomposition, a temperature of the plasma jet is 800-1300 C.

3. The method for methanol synthesis by plasma-oxygen carrier-catalysis coupling according to claim 1, wherein in the step of CO.sub.2 decomposition, the plasma is cooled by H.sub.2O during the H.sub.2O decomposition step.

4. The method for methanol synthesis by plasma-oxygen carrier-catalysis coupling according to claim 1, wherein in the step of O.sub.2 capture by the oxygen carrier, a suitable working temperature of the oxygen carrier is within the plasma jet temperature range of 800-1300 C.

5. The method for methanol synthesis by plasma-oxygen carrier-catalysis coupling according to claim 1, wherein in the step of O.sub.2 capture by the oxygen carrier, the oxygen carrier is a cerium-perovskite composite oxygen carrier prepared by a sol-gel method.

6. The method for methanol synthesis by plasma-oxygen carrier-catalysis coupling according to claim 1, wherein in the step of synthesis of methanol, the NiGa catalyst is prepared by an incipient wetness impregnation method.

7. A system for methanol synthesis by plasma-oxygen carrier-catalysis coupling for implementing the method of claim 1, wherein a main part of the system is an enhanced vibrational-state plasma jet reaction device; A lower part of the enhanced vibrational-state plasma jet reaction device is provided with a plasma jet formation zone formed by an external electrode, an internal electrode, a base, and a CO.sub.2 gas flow inlet; a middle part is a two-layer sleeve structure, a space between inner wall and outer wall forms an oxygen carrier H.sub.2O decomposition reaction zone, and an inner space of the inner wall is communicated with the plasma jet formation zone to form a plasma-oxygen carrier-water cooled CO.sub.2 decomposition reaction zone; The external electrode is located at the lower part of the reaction device, has a sleeve-type hollow structure and is fixed on the base; the inner electrode has a conical structure, is arranged at a lower-middle position in the hollow structure of the outer electrode and is integrally formed by a lower cylinder and an upper frustum, and bottom of the inner electrode is fixed on the base; an upper-middle position of the hollow structure of the external electrode has a structure of a tapered outlet; the CO.sub.2 gas flow inlet is arranged at bottom of the reaction device, and CO.sub.2 gas flow enters tangentially from the bottom of the reaction device through the CO.sub.2 gas flow inlet to form a rotating gas flow inside, which drives an arc between the electrodes to rotate and rise, and is ejected in a form of plasma jet under the action of the tapered outlet; An H.sub.2O inlet is arranged below the outer wall of the middle part of the reaction device, and through which H.sub.2O is introduced into the oxygen carrier H.sub.2O decomposition reaction zone, absorbs heat provided by the plasma jet in the inner wall, and is decomposed by the oxygen carrier to output oxygen-free H.sub.2; the plasma-oxygen carrier-water cooled CO.sub.2 decomposition reaction zone outputs oxygen-free CO; Output gases of two parts of the middle sleeve are mixed at a top of the reaction device, and a CO hydrogenation methanol synthesis reaction zone and a methanol outlet are provided; oxygen-free CO and H.sub.2 are selectively synthesized into methanol at atmospheric pressure over NiGa catalyst, and the methanol passes out of the reaction device through the methanol outlet.

8. The system according to claim 7, wherein the external electrode and the internal electrode are connected to a frequency-adjustable high-voltage AC power supply, and the power supply has an adjustable frequency of 5-40 kHz, a maximum output voltage of 20 kV and a maximum power of 1 kW.

9. The system according to claim 7, further comprising a CO.sub.2 supply system, comprising a CO.sub.2 gas bottle, a mass flow controller, and a CO.sub.2 gas valve, wherein the CO.sub.2 gas bottle is used for storing CO.sub.2, the mass flow controller is used for controlling flow of CO.sub.2 gas, and the CO.sub.2 gas valve is connected with the CO.sub.2 gas flow inlet.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0032] FIG. 1 is a schematic diagram of the steps of a method for methanol synthesis by plasma-oxygen carrier-catalysis coupling;

[0033] FIG. 2 is a schematic diagram of a system for methanol synthesis by plasma-oxygen carrier-catalysis coupling.

DESCRIPTION OF EMBODIMENTS

[0034] The present disclosure will be further described in detail with the attached drawings and specific embodiments.

[0035] As shown in FIG. 1, the present disclosure provides a method for methanol synthesis by plasma-oxygen carrier-catalysis coupling, which includes the following steps: [0036] main reaction step 1CO.sub.2 decomposition: activating CO.sub.2 using an enhanced vibrational-state atmospheric-pressure plasma jet, so that the CO.sub.2 is decomposed into O.sub.2 and CO; [0037] main reaction step 2H.sub.2O decomposition: decomposing H.sub.2O into O.sub.2 and H.sub.2 by the high temperature generated in the plasma working environment; [0038] capturing O.sub.2 by an oxygen carrier: using a high-temperature oxygen carrier to absorb the decomposition product O.sub.2 in a CO.sub.2 decomposition reaction zone and a H.sub.2O decomposition reaction zone respectively, so as to separate the O.sub.2 from the decomposition product and obtain oxygen-free CO and H.sub.2 respectively; [0039] main reaction step 3synthesis of methanol: using a NiGa catalyst to facilitate the selective synthesis of methanol from oxygen-free CO and H.sub.2 at atmospheric pressure.

[0040] In the main reaction step 1, the reaction temperature is 800-1300 C., which is within the temperature of the plasma jet; by optimizing the electrode structure and electrical parameters, the reduced electric field is adjusted and controlled to enhance the vibrational-state level of the plasma jet. The electron energy distribution and vibrational/rotational-state energy level of plasma are determined by in-situ optical emission spectroscopy (OES) diagnosis, the spatial distribution of the temperature field of the plasma jet is measured by a thermocouple, and the plasma discharge characteristics, jet morphology and jet propulsion mechanism are determined by electrical signals and optical signals. By obtaining the above plasma parameters and characteristics, the enhanced vibrational state plasma in the reaction process is effectively regulated.

[0041] In the main reaction step 1, the specific detection methods of plasma parameters and characteristics mentioned in the previous paragraph are as follows: using a monochromator equipped with ICCD to obtain the spectrum of the discharge process, and then calculating the electron density according to the Stark broadening method, calculating the electron excitation temperature and vibration temperature according to the Boltzmann curve slope method, and calculating the rotation temperature according to the rotation line fitting method; using an oscilloscope to study the characteristics of discharge electrical parameters, and analyzing the pulse characteristics such as volt-ampere characteristics, pulse frequency and pulse amplitude, and calculating the characteristic parameters such as arc power, conductivity and electric field intensity by combining the obtained temperature and electrical parameters, calculating the reduced electric field (E/N); obtaining the spatial distribution of the axial temperature field of the plasma jet by using mobile thermocouple; recording the motion images of arc and jet by high-speed camera, and obtaining the arc motion characteristics and jet propulsion mechanism.

[0042] In the main reaction step 1, CO.sub.2 is decomposed based on the cascade vibration excitation path, which generates low and high-energy vibrational excited molecules of CO.sub.2*(.sup.1.sup.+) and CO.sub.2*(B.sub.2) in turn through the initial electron collision excitation and subsequent VV relaxation processes, among which CO.sub.2*(.sup.3B.sub.2) is highly reactive and easily decomposed under the collision of electrons or other particles. This path only needs 5.5 eV energy, which avoids energy waste and has high decomposition efficiency.

[0043] In the main reaction step 1, the spatial dynamic distribution of atomic concentrations of CO, CO.sub.2, O.sub.2 and O along the axial direction of the jet is detected based on in-situ molecular beam mass spectrometry and OES, respectively. In the plasma jet-carrier coupling system, the reaction effect, the concentration of the product O.sub.2 and oxygen capture rate of the oxygen carrier are controlled by controlling the spatial position of the carrier, interface temperature, reaction time, gas flow rate and airspeed.

[0044] In the main reaction step 1, the specific detection means of the parameters and characteristics of the gas/oxygen carrier mentioned in the previous paragraph are as follows: a two-stage differential pumping system is adopted to generate a sampling molecular beam, so that high-activity chemical components can be frozen in situ by entering an ultra-low pressure environment, and then quantitative detection is carried out by quadrupole mass spectrometry equipped with electron ionization to obtain the spatial dynamic distribution of the concentrations of CO, CO.sub.2 and O.sub.2 along the axial direction of the jet; the characteristic spectral lines of O atoms at different axial positions are collected by emission spectroscopy system, and the axial spatial distribution of the O atom density is obtained by combining the intensity of atomic spectral lines and spectral parameters of components with known concentrations.

[0045] At the label I, the oxygen carrier used is a cerium-perovskite (LaFeO.sub.3-) composite oxygen carrier prepared by a sol-gel method. The preparation process is as follows: Ce(NO.sub.3).sub.3, La(NO.sub.3).sub.3 and Fe(NO.sub.3).sub.3 hydrates were dissolved in deionized water to prepare a 0.25 mol/L solution, which was stirred in a water bath at 30 C. for 30 min, and citric acid was added, wherein the citric acid/cation (mol) ratio was 3/1; then the mixture was stirred in a water bath at 50 C. for 30 min to form a chelate, ethylene glycol was added, wherein the ratio of ethylene glycol to cation (mol) was 2/1; then the mixture was stirred in a water bath at 80 C. for 2 hours to form a gel, which was dried at 110 C. for 24 hours, ground into powder, roasted at 400 C. for 4 hours, and then roasted at 900 C. for 6 hours to prepare CeO.sub.2LaFeO.sub.3 cerium-based perovskite composite material, followed by granulation and reduction to complete the preparation.

[0046] At the label II, the water cooling intensity is adjusted by controlling the water flow rate, so as to realize the selective adjustment of the plasma jet temperature in the main reaction step 1 and weaken the reverse reaction of CO.sub.2 decomposition, thus realizing the adjustment of CO.sub.2 decomposition effect; at the same time, the temperature of water heated by heat exchange is controlled by electric auxiliary heating in the main reaction step 2, and oxygen-free H.sub.2 is obtained by efficient decomposition of oxygen carrier.

[0047] At the label III, the flow rates of CO and H.sub.2 are controlled respectively, and the high temperature is kept after the main reaction step 3 to prevent liquid products such as methanol from condensing. Then, some product gases can be extracted and analyzed quantitatively in an online gas chromatograph, and indicators such as reactant conversion rate, methanol selectivity and by-product generation amount can be obtained. These indicators can be used to adjust system parameters such as catalyst type, reactant flow rate and ratio, reaction speed and space velocity, so as to optimize whole system.

[0048] At the label IV, the NiGa catalysts used can be divided into two types according to the different carriers used. The first method uses ZrO.sub.2 or CeO.sub.2 as the carrier, and its preparation method is as follows: taking a certain amount of ZrO(NO.sub.3).sub.2.Math.5H.sub.2O and Ce(NO.sub.3).sub.3.Math.6H.sub.2O, respectively, adding deionized water and stirring until they were completely dissolved, dripping a NH.sub.4OH solution, stirring, filtering, uniformly dispersing the obtained solid in a NH.sub.4OH solution again, then drying at 70 C. for 24 h and calcining at 500 C. for 4 h to obtain CeO.sub.2 or ZrO.sub.2 carrier. A certain amount of a mixed solution of nickel nitrate and gallium nitrate was impregnated on the carrier with a high specific surface area, dried in air at 100 C. for 24 h, and reduced in high purity hydrogen at 700 C. for 2 h. The second method uses SiO.sub.2 as the carrier, and its preparation method is as follows: a certain amount of hydrate of nickel nitrate and gallium nitrate was dissolved in deionized water to obtain a mixed solution, which is then incipient-wetness impregnated on the carrier with a high specific surface area, dried in the air atmosphere of 100 C. for 24 h, and reduced for 2 h in a high-purity hydrogen flow of 700 C.

[0049] As shown in FIG. 2, the embodiment of the present disclosure provides a system for synthesizing methanol by plasma-oxygen carrier-catalysis coupling, and the main part of the system is a plasma jet reaction device;

[0050] A lower part of the enhanced vibrational-state plasma jet reaction device is provided with a plasma jet formation zone formed by an external electrode, an internal electrode, a base and a CO.sub.2 gas flow inlet; a middle part is a two-layer sleeve structure, a space between inner and outer walls forms an oxygen carrier H.sub.2O decomposition reaction zone, and an inner space of the inner wall is communicated with the plasma jet formation zone to form a plasma-oxygen carrier-water cooled CO.sub.2 decomposition reaction zone;

[0051] The external electrode is located at the lower part of the reaction device, has a sleeve-type hollow structure and is fixed on the base; the inner electrode has a conical structure, is arranged at a lower-middle position in the hollow structure of the outer electrode and is integrally formed by a lower cylinder and an upper frustum, and the bottom of the inner electrode is fixed on the base; an upper-middle position of the hollow structure of the external electrode has a structure of a tapered outlet; the external electrode and the internal electrode are connected to a frequency-adjustable high-voltage AC power supply, and the power supply has an adjustable frequency of 5-40 kHz, a maximum output voltage of 20 kV and a maximum power of 1 kW; the CO.sub.2 gas flow inlet is positioned at the bottom of the reaction device, and CO.sub.2 gas flow enters tangentially from the bottom of the device through the CO.sub.2 gas flow inlet to form a rotating gas flow inside, which drives an arc between the electrodes to rotate and rise, and the arc is ejected in a form of plasma jet under the action of the tapered outlet;

[0052] An H.sub.2O inlet is arranged below the outer wall of the middle part of the reaction device, and through which H.sub.2O is introduced into the oxygen carrier H.sub.2O decomposition reaction zone, absorbs the heat provided by the plasma jet in the inner wall, and is decomposed by the oxygen carrier to output oxygen-free H.sub.2; the plasma-oxygen carrier-water cooled CO.sub.2 decomposition reaction zone outputs oxygen-free CO;

[0053] The output gases of the two parts of the middle sleeve are mixed at a top of the reaction device, and a CO hydrogenation methanol synthesis reaction zone and a methanol outlet are provided; oxygen-free CO and H.sub.2 are selectively synthesized into methanol at atmospheric pressure over NiGa catalyst, and the methanol passes out of the reaction device through the methanol outlet.

[0054] Further, a CO.sub.2 supply system may be provided, and the CO.sub.2 supply system includes a CO.sub.2 gas bottle, a mass flow controller and a CO.sub.2 gas valve, wherein the CO.sub.2 gas bottle is used for storing CO.sub.2, the mass flow controller is used for controlling the flow of CO.sub.2 gas, and the CO.sub.2 gas valve is connected with the CO.sub.2 gas flow inlet.

[0055] The above is only the preferred embodiment of the present disclosure, and although the present disclosure has been disclosed in the above with preferred embodiments, it is not intended to limit the present disclosure. Any person familiar with the field can make many possible changes and modifications to the technical solution of the present disclosure by using the methods and technical contents disclosed above, or modify it into equivalent embodiments with equivalent changes without departing from the scope of the technical solution of the present disclosure. Therefore, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present disclosure without departing from the content of the technical solution of the present disclosure still fall within the scope of protection of the technical solution of the present disclosure.