Method for preparing high-added-value product through non-thermal plasma coupling carbonate reduction

Abstract

The invention discloses a method for preparing a high-added-value product through non-thermal plasma coupling carbonate reduction. According to the method, the decomposition temperature is reduced to 25-550 DEG C from 600 DEG C or above through synergistic catalysis of the plasma and the catalyst, carbonate hydrogenation reduction is carried out under normal pressure, so that preparation of high-added-value products is achieved, meanwhile, reduction of energy consumption and equipment maintenance, operation and safety cost in the whole process is facilitated, and high economic benefits and environmental benefits are achieved. In addition, the catalyst contains a dielectric component with a high dielectric constant, so that uniform and concentrated discharge of plasmas is facilitated, and the carbonate reduction conversion efficiency and the energy utilization efficiency are improved.

Description

Technical Field

[0001] This invention belongs to the field of carbonate reduction refining technology, specifically, it relates to a method for preparing high value-added products by non-thermal plasma coupled carbonate reduction. Background Technology

[0002] Cement, steel, and non-ferrous metallurgy, among other industries with high emissions, are crucial pillars of the national economy. Carbonates, including limestone (CaCO3), siderite (FeCO3), magnesite (MgCO3), and dolomite (CaMg(CO3)2), are commonly used raw materials or precursors in these industries. These often require thermal decomposition to convert them into metal oxides before being used in subsequent production. Thermal decomposition involves high temperatures and high carbon dioxide emissions, classifying it as a heavy emission process. Carbon dioxide emissions from related industrial processes account for over 30% of the total industrial carbon emissions nationwide. Therefore, reducing energy consumption and carbon emissions from carbonate thermal decomposition remains a critical challenge for the carbonate refining industry.

[0003] Carbonate reduction refining technology fundamentally changes the traditional production process of carbonates by calcining them in air. By introducing hydrogen-donating gases (such as CH4, H2, etc.), the carbon in carbonates (adsorbed CO2) is catalytically reduced into high-value-added carbon-containing chemicals such as syngas and methanol. Simultaneously, solid metal oxides are produced. This process completely eliminates CO2 emissions while yielding metal oxide products and high-value-added carbon-containing chemicals, achieving the dual goals of carbon reduction and efficiency improvement in the carbonate industry. However, existing carbonate catalytic hydrogenation technologies still face some challenges in practical applications: although the operating temperature is lower than that of traditional pyrolysis processes, the stable chemical properties of the hydrogen-donating molecules and the CO2 bonded in the carbonate, coupled with limitations imposed by reaction kinetics and thermodynamics, mean that the required reaction temperature remains high. For example, the catalytic hydrogenation of calcium carbonate still requires a reduction temperature above 600℃. Furthermore, high-temperature conditions often lead to problems such as low reaction efficiency, poor selectivity of the target product, easy catalyst deactivation, and limited safety.

[0004] Plasma, an ionized gas composed of high-energy electrons, ions, neutral molecules, and free radicals, has been widely used in the catalysis of chemical processes in recent years. The high-energy electrons and active ions in plasma can directly participate in chemical reactions, significantly increasing reaction rates and controlling reaction pathways. While there are reports on using plasma to catalyze the hydrogenation reduction of carbonates, these methods still largely rely on high-temperature conditions and have not completely overcome the various problems associated with these conditions.

[0005] Therefore, there is still an urgent need to develop a more efficient, stable, and mild plasma-catalyzed process for the hydrogenation reduction of carbonates. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, this invention provides a method for preparing high-value-added products by non-thermal plasma-coupled carbonate reduction. Unlike thermal plasma, non-thermal plasma operates at lower temperatures, typically below 823 K. High-energy electrons can be accelerated to very high temperatures or energies (1-10 eV) by a strong electric field, exhibiting strong reactivity. Simultaneously, the background atmosphere and ion temperatures are much lower than the high-energy electron temperatures, resulting in all particles being in a non-equilibrium state. This characteristic gives non-thermal plasma unique advantages in reducing reaction temperature and energy consumption. Based on this, this invention utilizes the ability of non-thermal plasma to excite high-energy electrons and promote free radical generation, inducing the breaking of carbon-oxygen bonds in carbonates and the activation of carbon-hydrogen bonds in hydrogen-donating molecules. The aim is to achieve relatively low-temperature activation of carbonates and hydrogen-containing molecules, thereby achieving low-energy consumption, high selectivity, and high-efficiency catalytic reduction of carbonates.

[0007] In one aspect, the present invention provides a catalyst comprising a catalytically active component, a dielectric component, and a support; the catalytically active component is selected from at least one of magnesium, aluminum, calcium, barium, titanium, manganese, vanadium, niobium, tungsten, molybdenum, chromium, iron, cobalt, nickel, copper, zinc, tin, gallium, zirconium, lanthanum, cerium, ruthenium, gold, palladium, and platinum; the dielectric constant of the dielectric component is 10 to 7000; the support is selected from at least one of alumina, zirconium oxide, silica, cerium oxide, activated carbon, silicon carbide, and molecular sieves; wherein the mass fraction of the catalytically active component in the catalyst is 1 to 50%, the mass fraction of the dielectric component is 30 to 90%, and the mass fraction of the support is 5 to 30%.

[0008] Preferably, in the catalyst, the mass fraction of the catalytically active component is 5-30%, the mass fraction of the dielectric component is 40-80%, and the mass fraction of the support is 5-30%.

[0009] Preferably, the catalytically active component is selected from CuZn, FeCo, NiRu, Fe5C2, CuCe, RhNi, FeNi, FeMnK, ZnMg and PdZn.

[0010] Preferably, the dielectric component is selected from at least one of barium titanate, strontium titanate, titanium dioxide, aluminum oxide, quartz sand, and cerium oxide.

[0011] In another aspect, the present invention provides a method for preparing a catalyst as described in any embodiment herein, the method being selected from at least one of volume impregnation, over-volume impregnation, ion exchange, coprecipitation, and sol-gel methods.

[0012] Preferably, the method is a volume impregnation method.

[0013] In another aspect, the present invention provides the use of a catalyst as described in any embodiment herein in the catalytic reduction of carbonates, said catalyst being used in conjunction with plasma for the catalytic reduction of carbonates.

[0014] In another aspect, the present invention provides a method for reducing carbonates, the method comprising using nonthermal plasma and a catalyst as described in any embodiment herein to synergistically catalyze the reduction of carbonates; the reactants include carbonate feedstock and gaseous feedstock.

[0015] Preferably, the particle size of the carbonate raw material is 10–500 μm.

[0016] In one or more embodiments, the non-thermal plasma is generated by a plasma generator, which includes a high-voltage power supply and high-voltage electrodes; the input power of the plasma generator is 1–300W, and the input frequency is 1–15kHz; the output power of the non-thermal plasma is 1–300W, the voltage waveform is a sine wave, and the peak-to-peak voltage is 1–30kV.

[0017] Preferably, the waveform of the current of the non-thermal plasma is a pulse wave containing positive and negative pulses, wherein the duration and amplitude of the positive and negative pulses of the pulse wave are the same.

[0018] Preferably, the input power is 80–280W. More preferably, the input power is 100–240W.

[0019] Preferably, the input frequency is 3 to 12 kHz. More preferably, the input frequency is 5 to 10 kHz.

[0020] Preferably, the output power is 60–250W. More preferably, the output power is 80–220W.

[0021] Preferably, the peak-to-peak voltage is 5–20 kV. More preferably, the peak-to-peak voltage is 9–16 kV.

[0022] Preferably, the reaction is carried out in a reactor, and the high-voltage electrode is embedded inside the reactor; the reactor is made of at least one material selected from corundum ceramic, quartz, aluminum nitride ceramic, zirconium oxide, polytetrafluoroethylene, and polyimide.

[0023] More preferably, the reactor is made of corundum ceramic.

[0024] Preferably, the non-thermal plasma is generated by a method selected from dielectric barrier discharge, corona discharge, microwave discharge, glow discharge, sliding arc discharge, and radio frequency.

[0025] More preferably, the non-thermal plasma is generated by dielectric barrier discharge.

[0026] More preferably, the dielectric barrier discharge structure is selected from at least one of the following: parallel plate type, coaxial cylindrical type, surface discharge type, porous electrode type, and packed bed type. Even more preferably, the dielectric barrier discharge structure is a coaxial cylindrical discharge structure.

[0027] Preferably, the high-voltage electrode is made of at least one material selected from stainless steel, copper, nickel-based alloys, tungsten, platinum, gold, and graphite. More preferably, the high-voltage electrode is made of stainless steel.

[0028] Preferably, the catalyst is packed in the reactor, and the packing method is selected from at least one of ball milling mixing, electrode coating doping, reactor wall packing, and dual-bed packing. More preferably, the packing method is reactor wall packing.

[0029] In one or more embodiments, the reaction temperature is 25–600°C.

[0030] Preferably, the reaction temperature is 100–580°C. More preferably, the reaction temperature is 200–550°C.

[0031] In one or more embodiments, the carbonate raw material is selected from at least one of potassium carbonate, sodium carbonate, calcium carbonate, magnesium carbonate, ferric carbonate, manganese carbonate, ferrous carbonate, sodium bicarbonate, potassium bicarbonate, calcium bicarbonate, dolomite, calcite, limestone, magnesite, and siderite; the reducing gas is selected from at least one of hydrogen, ammonia, water vapor, methane, and ethane.

[0032] In one or more embodiments, the gaseous feedstock further includes an inert gas, wherein the volume fraction of the reducing gas in the gaseous feedstock is 1-95%, and the volume fraction of the inert gas is 0-95%.

[0033] Preferably, the volume fraction of the reducing gas in the gaseous raw material is 40-90%. More preferably, the volume fraction of the reducing gas in the gaseous raw material is 50-80%.

[0034] In one or more embodiments, the molar ratio of the gaseous feedstock to the carbonate feedstock is 2 to 50.

[0035] Preferably, the molar ratio of gaseous feedstock to carbonate feedstock is 8 to 40.

[0036] Preferably, the carbonate raw material is at least one of calcium carbonate, limestone, calcite, and dolomite, the reaction temperature is 300–600°C, and the molar ratio of gaseous raw material to carbonate raw material is 10–20.

[0037] Preferably, the carbonate raw material is at least one of magnesium carbonate and magnesite, the reaction temperature is 200-400°C, and the molar ratio of gaseous raw material to carbonate raw material is 2-30.

[0038] Preferably, the carbonate raw material is at least one of ferrous carbonate, manganese carbonate, and siderite, the reaction temperature is 250–400°C, and the molar ratio of gaseous raw material to carbonate raw material is 2–40.

[0039] Preferably, the carbonate raw material is at least one of potassium carbonate and sodium carbonate, the reaction temperature is 150-300°C, and the molar ratio of gaseous raw material to carbonate raw material is 2-20.

[0040] Preferably, the carbonate raw material is at least one of potassium bicarbonate and sodium bicarbonate, the reaction temperature is 10-100°C, and the molar ratio of gaseous raw material to carbonate raw material is 2-20.

[0041] Preferably, the carbonate raw material is copper carbonate, the reaction temperature is 50-150°C, and the molar ratio of gaseous raw material to carbonate raw material is 5-30.

[0042] In one or more embodiments, the products of the reaction are selected from at least one of metal oxides, syngas, methane, alcohols, low-carbon alkanes, and low-carbon olefins.

[0043] Preferably, the low-carbon alkane or low-carbon olefin has 2 to 4 carbon atoms.

[0044] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0045] (1) The method provided by this invention replaces the traditional single thermal-driven carbonate hydrogenation reaction with a non-thermal plasma coupled catalyst reduction process. The plasma reaction device can excite active substances (such as high-energy electrons, free radicals, etc.) under mild conditions. By constructing a strong coupling active site of "plasma-catalyst-carbonate", the traditional thermal-driven high-temperature carbonate hydrogenation reaction path is changed, breaking through the traditional thermodynamic limitations and realizing the synergistic catalysis of plasma and catalyst. The decomposition temperature is reduced from above 600℃ to 200-550℃, and carbonate hydrogenation reduction is carried out under normal pressure to achieve the preparation of metal oxides and C1 fuels or high-value C2+ products. At the same time, it is beneficial to reduce the energy consumption of the whole process and the equipment maintenance, operation and safety costs, which has high economic and environmental benefits.

[0046] (2) To address the problems of uneven discharge and easy sintering of catalysts in non-thermal plasma reaction processes, the method of this invention adds dielectric components with high dielectric constants, such as barium titanate, to the catalyst. High dielectric constant materials can undergo strong polarization under the action of an electric field, transforming the discharge mode from a small amount of concentrated arc discharge to a large amount of uniform, concentrated micro-discharge. Simultaneously, the high dielectric material can act as a micro-electric field enhancer, generating an extremely strong non-uniform local electric field around it, enhancing the energy density and electron collision frequency in the plasma reaction device, significantly reducing the gas breakdown voltage, and enabling the input energy to be used more efficiently to generate high-energy electrons and active species, rather than being converted into Joule heat. Therefore, it can significantly improve the carbonate reduction conversion efficiency and energy efficiency. Attached Figure Description

[0047] Figure 1 This is the voltage curve of carbonate in the plasma catalysis process.

[0048] Figure 2 This is the current curve of carbonate in the plasma catalysis process.

[0049] Figure 3 This is the Lissajous curve of carbonate in the plasma catalysis process.

[0050] Figure 4 The voltage and current curves of plasma discharge for Example 1 and Comparative Example 2 are shown.

[0051] Figure 5 The voltage and current curves of plasma discharge for Example 1 and Comparative Example 3 are shown.

[0052] Figure 6 The Lissajous curves are for plasma discharge in Example 1 and Comparative Example 3.

[0053] Figure 7 The graph shows the carbonate decomposition rate, product selectivity, and carbon dioxide emission reduction rate for Example 1 and Comparative Examples 1-3. Detailed Implementation

[0054] In the following embodiments, the calculation methods for the relevant parameters or indicators are as follows:

[0055] Where m is the mass of unconverted carbonate after the reaction, and m0 is the mass of calcium carbonate at the beginning of the reaction.

[0056] Where n g n is the total molar amount of gas. c This represents the molar amount of carbonate.

[0057] Among them, F outt is the volume fraction of carbon dioxide in the product gas, t is the reaction time, M is the relative molecular mass of the carbonate, and m0 is the initial mass of the carbonate.

[0058] The target product selectivity refers to the ratio of the volume fraction of the target product (gas) in the product gas to the volume fraction of all detectable conversion products (gases) in the product gas. For example, when methanol is the target product, Where q CH3OH q represents the volume fraction of the target product methanol in the product gas. CO q CH4 and q C2+ These represent the volume fractions of detectable gaseous byproducts in the product gas: carbon monoxide, methane, and low-carbon olefins.

[0059] Plasma discharge power P out (W)=f×C M ×k×k x ×k y ×A, where f is the plasma discharge frequency (Hz); C M The sampling capacitor in the circuit is 4.7 × 10⁻⁶. -7 (F); k x k y is the scaling factor of the high-voltage probe, all taken as 1; k is the attenuation factor of the sampling voltage, taken as 1000; A is the integral area of ​​the Lissajous figure.

[0060] Among them, P out P is the plasma discharge power (W). in The plasma input power is (W).

[0061] In the following embodiments, the gas in the conversion product is detected by gas chromatography, and the solid in the conversion product is detected by X-ray diffraction or thermogravimetric analysis.

[0062] In the following embodiments, "reactor wall packing" refers to the catalyst components being directly loaded onto the inner wall surface of the reactor by means of slurry coating; "ball milling and mixing packing" refers to the catalyst components being mixed by ball milling and then filled into the reactor; "electrode coating and doping packing" refers to the catalyst components being uniformly loaded onto the electrode surface to form an electrode film by vapor deposition; and "dual-bed packing" refers to the catalyst components being packed into the reactor in layers.

[0063] In the following examples, "low-carbon olefin" refers to an olefin with 4 or fewer carbon atoms.

[0064] In the following embodiments, for the carbonate hydrogenation reduction reaction, the components of the product gas are detected in real time by gas chromatography, and the degree of completion of the reaction is calculated by carbon balance. The reaction can be considered to be completed when the carbon balance of the whole process approaches 1.

[0065] Example 1

[0066] Taking the target product syngas as an example, the raw materials and process for the synergistic catalytic reduction of carbonates by non-thermal plasma and catalyst are as follows:

[0067] The coaxial reactor is uniformly filled with a catalyst in the form of reactor wall packing, which uses Al2O3 as support, bimetallic CuZn as catalytic active component and BaTiO3 as dielectric component, wherein the mass fraction of catalytic active component is 10% and the mass fraction of BaTiO3 is 60%; the catalyst is prepared by initial wet impregnation method.

[0068] The carbonate feedstock is calcium carbonate with a particle size of 80-110 μm. The feedstock gas consists of a reducing gas and an inert gas; the reducing gas is hydrogen, and the inert gas is argon, with a hydrogen volume fraction of 50%. The gas-solid molar ratio of the feedstock gas to the carbonate feedstock is 15.

[0069] After feeding, the reactor is heated to 550°C, and the plasma high-voltage power supply is adjusted to an input power of 216W and a frequency of 5.4kHz to generate plasma by discharging the high-voltage electrode, which synergistically catalyzes the hydrogenation reduction of carbonates with the catalyst. The plasma discharge parameters are recorded by an oscilloscope connected in parallel in the plasma discharge circuit.

[0070] As shown in Table 1, based on oscilloscope recordings, analysis of the product gas components, and further calculations, the decomposition rate of calcium carbonate was 100%, and the CO2 emission reduction rate was 98%. The solid phase product was calcium oxide, and the selectivity of syngas in the gaseous phase products was 98.6%. Figures 1-4 As shown in Figure 6, when calcium carbonate is used as the carbonate raw material, the plasma voltage waveform during discharge is a stable sine wave with a peak-to-peak value of 8.5 kV; the current waveform is a pulsed discharge with equal discharge intensity at the positive and negative electrodes. The plasma output power is 198 W, and the energy efficiency is 91.78%.

[0071] Example 2

[0072] Taking methanol as the target product, the raw materials and process for the synergistic catalytic reduction of carbonate by non-thermal plasma and catalyst are as follows:

[0073] The coaxial reactor is uniformly filled with a catalyst consisting of ZrO2 as a support, bimetallic FeCo as the catalytic active component, and TiO2 as the dielectric component, using a ball milling and mixing method. The mass fraction of the catalytic active component is 20%, and the mass fraction of TiO2 is 60%. The catalyst is prepared by an over-volume impregnation method.

[0074] The carbonate feedstock is magnesium carbonate with a particle size of 80-110 μm. The feedstock gas consists of a reducing gas and an inert gas; the reducing gas is water vapor and the inert gas is argon, with a water vapor volume fraction of 50%. The gas-solid molar ratio of the feedstock gas to the carbonate feedstock is 15.

[0075] After feeding, the reactor is heated to 250°C, and the plasma high-voltage power supply is adjusted to an input power of 120W and a frequency of 6.3kHz to generate plasma by discharge of the high-voltage electrode, which synergistically catalyzes the reduction of carbonates with the catalyst. The plasma discharge parameters are recorded by an oscilloscope connected in parallel in the plasma discharge circuit.

[0076] As shown in Table 1, based on oscilloscope recordings, analysis of the product gas components, and further calculations, the decomposition rate of calcium carbonate was 100%, and the CO2 emission reduction rate was 98%. The solid product was magnesium oxide, and the selectivity for methanol in the gaseous products was 97.8%. Figures 1-3 As shown, when magnesium carbonate is used as the carbonate raw material, the plasma voltage waveform during discharge is a stable sine wave with a peak-to-peak value of 9kV; the current waveform is a pulsed discharge with equal discharge intensity at both positive and negative electrodes. The plasma output power is 109W, and the energy efficiency is 91.02%.

[0077] Example 3

[0078] Taking the target product methane as an example, the raw materials and process for the synergistic catalytic reduction of carbonates by non-thermal plasma and catalyst are as follows:

[0079] The coaxial reactor is uniformly filled with a catalyst using CeO2 as a support, bimetallic NiRu as the catalytic active component, and SrTiO3 as the dielectric component in the form of ball milling and mixing. The mass fraction of the catalytic active component is 5%, and the mass fraction of SrTiO3 is 80%. The catalyst is prepared by coprecipitation.

[0080] The carbonate feedstock is ferrous carbonate with a particle size of 80-100 μm; the feed gas consists of a reducing gas and an inert gas; the reducing gas is ammonia, and the inert gas is helium, with the ammonia volume fraction in the feed gas being 70%. The gas-solid molar ratio of the feed gas to the carbonate feedstock is 12.

[0081] After feeding, the reactor is heated to 300°C, and the plasma high-voltage power supply is adjusted to an input power of 108W and a frequency of 7.5kHz to generate plasma by discharge of the high-voltage electrode, which synergistically catalyzes the reduction of carbonates with the catalyst. The plasma discharge parameters are recorded by an oscilloscope connected in parallel in the plasma discharge circuit.

[0082] As shown in Table 1, based on oscilloscope recordings, analysis of the product gas components, and further calculations, the decomposition rate of calcium carbonate was 100%, and the CO2 emission reduction rate was 94.7%. The solid phase product was iron oxide, and the selectivity for methane in the gaseous phase products was 98.7%. Figures 1-3 As shown, when ferrous carbonate is used as the carbonate raw material, the voltage waveform of the plasma during the discharge process is a stable sine wave with a peak-to-peak value of 9kV; the current waveform is a pulse discharge with equal discharge intensity at the positive and negative poles, the plasma output power is 96W, and the energy efficiency is 89.28%.

[0083] Example 4

[0084] Taking the target product, low-carbon olefins, as an example, the raw materials and process for the synergistic catalytic reduction of carbonates by non-thermal plasma and catalyst are as follows:

[0085] The coaxial reactor is uniformly filled with a catalyst consisting of ZrO2 as a support, Fe5C2 as the catalytic active component, and SiO2 as the dielectric component, in the form of electrode coating and doping filling. The mass fraction of the catalytic active component is 30%, and the mass fraction of SiO2 is 50%. The catalyst is prepared by ion exchange.

[0086] The carbonate feedstock is magnesite with a particle size of 70-90 μm. The feed gas consists of a reducing gas and an inert gas; the reducing gas is methane, and the inert gas is helium, with methane comprising 80% by volume. The gas-solid molar ratio of the feed gas to the carbonate feedstock is 18.

[0087] After feeding, the reactor is heated to 250°C, and the plasma high-voltage power supply is adjusted to an input power of 140W and a frequency of 6.5kHz to generate plasma by discharge of the high-voltage electrode, which synergistically catalyzes the reduction of carbonates with the catalyst. The plasma discharge parameters are recorded by an oscilloscope connected in parallel in the plasma discharge circuit.

[0088] As shown in Table 1, based on oscilloscope recordings, analysis of the product gas components, and further calculations, the decomposition rate of calcium carbonate was 100%, and the CO2 emission reduction rate was 97%. The solid phase product was magnesium oxide, and the selectivity for low-carbon olefins in the gaseous phase products was 89.5%. Figures 1-3As shown, when magnesite is used as the carbonate raw material, the voltage waveform of the plasma during the discharge process is a stable sine wave with a peak-to-peak value of 9kV; the current waveform is a pulse discharge with equal discharge intensity at the positive and negative poles, the plasma output power is 128W, and the energy efficiency is 91.4%.

[0089] Example 5

[0090] Taking methanol as the target product, the raw materials and process for the synergistic catalytic reduction of carbonate by non-thermal plasma and catalyst are as follows:

[0091] The coaxial reactor is uniformly filled with a catalyst consisting of ZrO2 as a support, CuCe bimetal as the catalytic active component, and BaTiO3 as the dielectric component, in the form of electrode coating and doping filling. The mass fraction of the catalytic active component is 30%, and the mass fraction of BaTiO3 is 60%. The catalyst is prepared by ion exchange.

[0092] The carbonate feedstock is sodium carbonate with a particle size of 120-140 μm; the feed gas consists of a reducing gas and an inert gas; the reducing gas is hydrogen, and the inert gas is helium, with a hydrogen volume fraction of 80%. The gas-solid molar ratio of the feed gas to the carbonate feedstock is 25.

[0093] After feeding, the reactor is heated to 250°C, and the plasma high-voltage power supply is adjusted to an input power of 100W and a frequency of 6kHz to generate plasma by discharge of the high-voltage electrode, which synergistically catalyzes the reduction of carbonates with the catalyst; the plasma discharge parameters are recorded by an oscilloscope connected in parallel in the plasma discharge circuit.

[0094] As shown in Table 1, based on the oscilloscope recordings, the detection of the product gas components, and further calculations, the decomposition rate of calcium carbonate was 100%, and the CO2 emission reduction rate was 97%. The solid product was sodium hydroxide, and the selectivity of methanol in the gaseous product was 91.5%. During the discharge process, the plasma voltage waveform was a stable sine wave with a peak-to-peak value of 9kV; the current waveform was a pulsed discharge with equal discharge intensity at both positive and negative electrodes; the plasma output power was 88W, and the energy efficiency was 88%.

[0095] Example 6

[0096] Taking the target product, low-carbon olefins, as an example, the raw materials and process for the synergistic catalytic reduction of carbonates by non-thermal plasma and catalyst are as follows:

[0097] The coaxial reactor is uniformly filled in a dual-bed configuration with a catalyst consisting of Al2O3 as the support, RhNi bimetal as the catalytic active component, and SrTiO3 as the dielectric component. The mass fraction of the catalytic active component is 5%, and the mass fraction of SrTiO3 is 70%. The catalyst is prepared by the sol-gel method.

[0098] The carbonate feedstock is manganese carbonate with a particle size of 110-130 μm; the feed gas consists of a reducing gas and an inert gas; the reducing gas is methane and the inert gas is argon, with a methane volume fraction of 80%. The gas-solid molar ratio of the feed gas to the carbonate feedstock is 15.

[0099] After feeding, the reactor is heated to 300°C, and the plasma high-voltage power supply is adjusted to an input power of 180W and a frequency of 6.5kHz to generate plasma by discharge of the high-voltage electrode, which synergistically catalyzes the reduction of carbonates with the catalyst. The plasma discharge parameters are recorded by an oscilloscope connected in parallel in the plasma discharge circuit.

[0100] As shown in Table 1, based on oscilloscope recordings, the detection of product gas components, and further calculations, the decomposition rate of calcium carbonate was 100%, and the CO2 emission reduction rate was 97%. The solid phase product was manganese oxide, and the selectivity of low-carbon olefins in the gas phase products was 95%. During the discharge process, the plasma voltage waveform was a stable sine wave with a peak-to-peak value of 9.5 kV; the current waveform was a pulsed discharge with equal discharge intensity at both positive and negative electrodes; the plasma output power was 160 W, and the energy efficiency was 89%.

[0101] Example 7

[0102] Taking the target product methane as an example, the raw materials and process for the synergistic catalytic reduction of carbonates by non-thermal plasma and catalyst are as follows:

[0103] The coaxial reactor is uniformly filled with a catalyst in the form of reactor wall packing, which uses Al2O3 as support, FeNi bimetal as catalytic active component and BaTiO3 as dielectric component, wherein the mass fraction of catalytic active component is 1% and the mass fraction of BaTiO3 is 90%; the catalyst is prepared by coprecipitation method.

[0104] The carbonate feedstock is ferrous carbonate with a particle size of 170-190 μm; the feed gas consists of a reducing gas and an inert gas; the reducing gas is water, and the inert gas is helium, with water accounting for 80% by volume. The gas-solid molar ratio of the feed gas to the carbonate feedstock is 40.

[0105] After feeding, the reactor is heated to 300°C, and the plasma high-voltage power supply is adjusted to an input power of 200W and a frequency of 6kHz to generate plasma by discharge of the high-voltage electrode, which synergistically catalyzes the reduction of carbonates with the catalyst; the plasma discharge parameters are recorded by an oscilloscope connected in parallel in the plasma discharge circuit.

[0106] As shown in Table 1, based on the oscilloscope recordings, the detection of product gas components, and further calculations, the decomposition rate of calcium carbonate was 100%, and the CO2 emission reduction rate was 97%. The solid phase product was iron oxide, and the selectivity of methane in the gas phase product was 98%. During the discharge process, the plasma voltage waveform was a stable sine wave with a peak-to-peak value of 16 kV; the current waveform was a pulsed discharge with equal discharge intensity at both positive and negative electrodes; the plasma output power was 178 W, and the energy efficiency was 89%.

[0107] Example 8

[0108] Taking the target product syngas as an example, the raw materials and process for the synergistic catalytic reduction of carbonates by non-thermal plasma and catalyst are as follows:

[0109] The coaxial reactor is uniformly filled with a catalyst using CeO2 as a support, FeMnK alloy as the catalytic active component, and SiO2 as the dielectric component in the form of ball milling and mixing. The mass fraction of the catalytic active component is 15%, and the mass fraction of SiO2 is 80%. The catalyst is prepared by coprecipitation.

[0110] The carbonate feedstock is dolomite with a particle size of 270-290 μm; the feedstock gas consists of a reducing gas and an inert gas; the reducing gas is hydrogen, and the inert gas is argon, with a hydrogen volume fraction of 80%. The gas-solid molar ratio of the feedstock gas to the carbonate feedstock is 20.

[0111] After feeding, the reactor is heated to 550°C, and the plasma high-voltage power supply is adjusted to an input power of 240W and a frequency of 10kHz to generate plasma by discharge of the high-voltage electrode, which synergistically catalyzes the reduction of carbonates with the catalyst; the plasma discharge parameters are recorded by an oscilloscope connected in parallel in the plasma discharge circuit.

[0112] As shown in Table 1, based on oscilloscope recordings, detection of product gas components, and further calculations, the decomposition rate of calcium carbonate was 100%, and the CO2 emission reduction rate was 97%. The solid phase products were magnesium oxide and calcium oxide, while the selectivity of syngas in the gas phase products was 95%. During the discharge process, the plasma voltage waveform was a stable sine wave with a peak-to-peak value of 14 kV; the current waveform was a pulsed discharge with equal intensity at both positive and negative electrodes; the plasma output power was 220 W, and the energy efficiency was 92%.

[0113] Example 9

[0114] Taking methanol as the target product, the raw materials and process for the synergistic catalytic reduction of carbonate by non-thermal plasma and catalyst are as follows:

[0115] The coaxial reactor is uniformly filled with a catalyst in the form of reactor wall packing, which uses CeO2 as support, ZnMg bimetal as catalytic active component and BaTiO3 as dielectric component, wherein the mass fraction of catalytic active component is 10% and the mass fraction of BaTiO3 is 80%; the catalyst is prepared by coprecipitation method.

[0116] The carbonate feedstock is potassium bicarbonate with a particle size of 70-90 μm; the feed gas consists of a reducing gas and an inert gas; the reducing gas is hydrogen, and the inert gas is argon, with a hydrogen volume fraction of 80%. The gas-solid molar ratio of the feed gas to the carbonate feedstock is 25.

[0117] After feeding, the reactor is heated to 25°C, and the plasma high-voltage power supply is adjusted to an input power of 100W and a frequency of 6.3kHz to generate plasma by discharge of the high-voltage electrode, which synergistically catalyzes the reduction of carbonates with the catalyst; the plasma discharge parameters are recorded by an oscilloscope connected in parallel in the plasma discharge circuit.

[0118] As shown in Table 1, based on the oscilloscope recordings, the detection of product gas components, and further calculations, the decomposition rate of calcium carbonate was 100%, and the CO2 emission reduction rate was 98%. The solid phase product was iron oxide, and the selectivity of methanol in the gas phase product was 94.8%. During the discharge process, the plasma voltage waveform was a stable sine wave with a peak-to-peak value of 9.2 kV; the current waveform was a pulsed discharge with equal discharge intensity at both positive and negative electrodes; the plasma output power was 95 W, and the energy efficiency was 95%.

[0119] Example 10

[0120] Taking methanol as the target product, the raw materials and process for the synergistic catalytic reduction of carbonate by non-thermal plasma and catalyst are as follows:

[0121] The coaxial reactor is uniformly filled with a catalyst using a ball milling and mixing method. The catalyst has ZrO2 as a support, PdZn bimetal as the catalytic active component, and TiO2 as the dielectric component. The mass fraction of the catalytic active component is 10%, and the mass fraction of TiO2 is 80%. The catalyst is prepared by the sol-gel method.

[0122] The carbonate feedstock is copper carbonate with a particle size of 90-110 μm. The feedstock gas consists of a reducing gas and an inert gas; the reducing gas is hydrogen, and the inert gas is nitrogen, with a hydrogen volume fraction of 60%. The gas-solid molar ratio of the feedstock gas to the carbonate feedstock is 20.

[0123] After feeding, the reactor is heated to 100°C, and the plasma high-voltage power supply is adjusted to an input power of 120W and a frequency of 6.3kHz to generate plasma by discharge of the high-voltage electrode, which synergistically catalyzes the reduction of carbonates with the catalyst. The plasma discharge parameters are recorded by an oscilloscope connected in parallel in the plasma discharge circuit.

[0124] As shown in Table 1, based on the oscilloscope recordings, the detection of product gas components, and further calculations, the decomposition rate of calcium carbonate was 100%, and the CO2 emission reduction rate was 98%. The solid phase product was iron oxide, and the selectivity of methanol in the gas phase product was 94.8%. During the discharge process, the plasma voltage waveform was a stable sine wave with a peak-to-peak value of 9.6 kV; the current waveform was a pulsed discharge with equal intensity at both positive and negative electrodes; the plasma output power was 109 W, and the energy efficiency was 91.02%.

[0125] Table 1: Parameters and process evaluation indicators for Examples 1-8

[0126]

[0127]

[0128] Comparative Example 1

[0129] This comparative example uses the method and conditions of Example 1 for the reaction, but differs from Example 1 in that the high-voltage power supply is turned off and no plasma is generated.

[0130] As shown in Table 2, based on oscilloscope recordings, detection of product gas components, and further calculations, the decomposition rate of calcium carbonate was 16.8%, and the CO2 emission reduction rate was 43%. The solid product was calcium oxide, while the selectivity of syngas in the gaseous product was only 41%.

[0131] It is evident that without plasma-assisted catalysis, the carbonate decomposition is incomplete at the same reaction temperature (550℃), and the carbon dioxide emission reduction rate remains at a low level. This may be due to the chemical inertness of the carbonate itself. Furthermore, without plasma-assisted catalysis, the reaction process within the system is limited by a high activation energy barrier, making it impossible to achieve carbonate decomposition and efficient carbon dioxide conversion at lower temperatures. Consequently, efficient carbonate conversion and carbon resource recycling cannot be achieved.

[0132] Comparative Example 2

[0133] This comparative example uses the method and conditions of Example 1 for the reaction, the difference being that no catalyst is used.

[0134] As shown in Table 2, based on oscilloscope recordings, analysis of the product gas components, and further calculations, the decomposition rate of calcium carbonate was 45.5%, and the CO2 emission reduction rate was 58%. The solid phase product was calcium oxide, and the selectivity of syngas in the gaseous phase products was 66%. Figure 4 As shown, the voltage waveform of the plasma during the discharge process is a sine wave with a peak-to-peak value of 9.12 kV; the current waveform is a pulse discharge, the plasma output power is 172 W, and the energy efficiency is 80.56%.

[0135] Depend on Figure 4 As can be seen, in the comparative example, no catalyst was added to the plasma-catalyzed system, resulting in a significant difference in the intensity of the filamentary discharge pulses during the positive and negative half-cycles. This led to low carbonate conversion and low energy efficiency. This may be due to the inability to construct a strongly coupled active site between the plasma and the catalyst, preventing the directional reduction of carbonates by numerous free radicals and high-energy groups in the gas phase, thus causing relaxation reactions and radical quenching. In contrast, Example 1, due to the addition of a catalyst, exhibited a significant change in the discharge current waveform: the intensity of the filamentary discharge pulses during the positive and negative half-cycles became closer, indicating enhanced symmetry and periodic stability of the discharge process. Simultaneously, the current pulse amplitude was significantly reduced, and the pulse distribution was more uniform. The discharge mode was a stable, uniformly distributed surface discharge mode, achieving a synergistic catalytic effect between plasma and the catalyst, thus improving CO2 conversion.

[0136] Comparative Example 3

[0137] The comparative example used the same catalyst, carbonate, feed gas and gas-solid ratio as in Example 1, and controlled the reaction temperature and plasma discharge parameters in the same way as in Example 1 to carry out the carbonate hydrogenation reaction. The difference was that no dielectric component was added to the catalyst.

[0138] As shown in Table 1, based on oscilloscope recordings, analysis of the product gas components, and further calculations, the decomposition rate of calcium carbonate was 75%, and the CO2 emission reduction rate was 85%. The solid phase product was calcium oxide, while the selectivity of syngas in the gaseous phase products was only 85.6%. Figure 5 As shown, the plasma voltage waveform during discharge is sinusoidal with a peak-to-peak value of 9.6 kV; the current waveform is pulsed discharge; the plasma output power is 145 W, and the energy efficiency is 67.53%. The Lissajous curve of the plasma discharge is shown below. Figure 6 As shown.

[0139] Depend on Figure 5 and Figure 6It is evident that when there is no dielectric component in the plasma-co-catalyzed system, the pulse current intensity increases significantly, and the difference in discharge intensity between the positive and negative cycles increases, resulting in uneven discharge between the positive and negative electrodes during the discharge cycle. Charge accumulation occurs on the positive electrode, affecting the stability and uniformity of the entire discharge process. This causes the plasma discharge characteristics to change from uniform surface discharge to local spark discharge or arc discharge. The Lissajous figure shows that the amount of charge transferred and energy injected within a single cycle increases significantly, leading to increased heat loss. Furthermore, due to the lack of strong coupling sites on the surface with high dielectric components, the free radical lifetime in the gas phase drops sharply, resulting in a decrease in the carbon dioxide emission reduction rate.

[0140] Comparison of carbonate decomposition rate, carbon dioxide emission reduction rate, and target product selectivity between Example 1 and Comparative Examples 1-3 Figure 7 As shown, Comparative Examples 1-3, due to the lack of plasma, catalyst, and dielectric components, respectively, could not simultaneously achieve the high carbonate decomposition rate, high carbon dioxide emission reduction rate, and high target product selectivity of Example 1.

[0141] Comparative Example 4

[0142] This comparative example uses the method and conditions of Comparative Example 1 for the reaction. The difference from Comparative Example 1 is that it uses a reaction temperature (750°C) that enables the carbonate decomposition rate and carbon dioxide emission reduction rate to reach the same level as in Example 1.

[0143] As shown in Table 1, based on the oscilloscope recordings, the detection of the product gas components, and further calculations, the decomposition rate of calcium carbonate was 100%, and the CO2 emission reduction rate was 70%. The solid product was calcium oxide, and the selectivity of syngas in the gaseous product was 68%.

[0144] As can be seen, in this comparative example, since there is no plasma-assisted catalysis in the carbonate hydrogenation process, and due to the limitation of thermodynamic equilibrium, to simultaneously achieve complete carbonate decomposition and a high carbon dioxide emission reduction rate, the reaction temperature needs to be increased from 550°C in Example 1 with plasma-assisted catalysis to 750°C. In Example 1, plasma participates in assisted catalysis, and complete carbonate decomposition and a high carbon dioxide emission reduction rate can be achieved at a relatively low temperature. The reason for this may be that there are a large number of high-energy active species (such as high-energy electrons and active free radicals) in the system. These active species can catalyze the decomposition and transformation of carbonate through surface reactions or gas-phase reactions, thus overcoming the limitations of thermodynamic equilibrium.

[0145] Table 2: Parameters and process evaluation indicators for Comparative Examples 1-4

[0146]

[0147]

[0148] In summary, the non-thermal plasma-coupled carbonate reduction method provided by this invention can efficiently co-produce corresponding metal oxides and various high-value-added carbon chemicals from different types of carbonates at relatively low temperatures. This provides a promising new approach for energy conservation, emission reduction, and efficiency improvement in industries such as cement, refractory materials, steel, and chemicals, and has significant advanced features and application value.

Claims

1. A catalyst characterized in that, The catalyst comprises a catalytically active component, a dielectric component and a carrier; the catalytically active component is selected from at least one of magnesium, aluminum, calcium, barium, titanium, manganese, vanadium, niobium, tungsten, molybdenum, chromium, iron, cobalt, nickel, copper, zinc, tin, gallium, zirconium, lanthanum, cerium, ruthenium, gold, palladium and platinum; the dielectric component has a dielectric constant of 10-7000; the carrier is selected from at least one of alumina, zirconia, silica, ceria, activated carbon, silicon carbide and molecular sieve; in the catalyst, the mass fraction of the catalytically active component is 1-50%, the mass fraction of the dielectric component is 30-90%, and the mass fraction of the carrier is 5-30%.

2. A process for the preparation of a catalyst as claimed in claim 1, characterized in that, The method is selected from at least one of volume impregnation method, super volume impregnation method, ion exchange method, coprecipitation method and sol-gel method.

3. Use of the catalyst according to claim 1 for catalytic reduction of carbonates, characterized in that, The catalyst is used for synergistically catalyzing reduction of carbonates with plasma.

4. A method of reducing carbonate, characterized by, The method comprises a reaction of synergistically catalyzing reduction of carbonates using a non-thermal plasma and the catalyst according to claim 1; the raw materials of the reaction comprise carbonate raw materials and gas raw materials.

5. The method of claim 4, wherein, The non-thermal plasma is generated by a plasma generator comprising a high-voltage power supply and a high-voltage electrode; the input power of the plasma generator is 1-300 W, and the input frequency is 1-15 kHz; the output power of the non-thermal plasma is 1-300 W, the waveform of the voltage is a sine wave, and the peak-to-peak value of the voltage is 1-30 kV.

6. The method of claim 4, wherein, The reaction temperature of the reaction is 25-600℃.

7. The method of claim 4, wherein, The carbonate raw materials are selected from at least one of potassium carbonate, sodium carbonate, calcium carbonate, magnesium carbonate, iron carbonate, manganese carbonate, ferrous carbonate, sodium bicarbonate, potassium bicarbonate, calcium bicarbonate, dolomite, calcite, limestone, magnesite and siderite; the reducing gas is selected from at least one of hydrogen, ammonia, water vapor, methane and ethane.

8. The method of claim 4, wherein, The gas raw materials further comprise an inert gas; in the gas raw materials, the volume fraction of the reducing gas is 1-95%, and the volume fraction of the inert gas is 0-95%.

9. The method of claim 4, wherein, The molar ratio of the gas raw materials to the carbonate raw materials is 2-50.

10. The method of claim 4, wherein, The product of the reaction is selected from at least one of metal oxides, synthesis gas, methane, alcohols and low-carbon olefins.

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