Device and method for producing hydrogen by catalyzing light alkane through ternary liquid metal based on electromagnetic induction

Abstract

The invention discloses a device and a method for producing hydrogen by catalyzing light alkane through ternary liquid metal based on electromagnetic induction. The device comprises an electromagnetic induction coil, a bubbling bed reactor and a gas distributor, the electromagnetic induction coil is arranged around the bubbling bed reactor, and the central axis of the electromagnetic induction coil coincides with or is perpendicular to the central axis of the bubbling bed reactor; the gas distributor is fixedly mounted at the gas inlet end of the bubbling bed reactor; the bubbling bed reactor is filled with a ternary liquid catalyst; according to the method, a nickel bismuth-indium compound is used as a ternary liquid metal catalyst, electromagnetic induction heating is used as a heating mode to directly heat the ternary liquid metal catalyst, and light alkane is introduced into the ternary liquid metal catalyst for cracking hydrogen production. The invention can solve the technical problems of low catalytic activity of the liquid metal catalyst, low methane conversion rate, low energy utilization rate in the reaction process and the like in the existing methane cracking hydrogen production method.

Description

Technical Field

[0001] The present invention relates to the technical field of metal catalytic hydrogen production, and more specifically to a device and method for producing hydrogen from light alkanes using ternary liquid metal catalysis based on electromagnetic induction. Background Art

[0002] Hydrogen is a pollution-free, clean, efficient and long-storable energy source. Under the national goal of "carbon peak and carbon neutrality", hydrogen energy will play a pivotal role in the future energy system. According to the amount of carbon emissions in the production process of hydrogen energy, hydrogen can be divided into three categories: "gray hydrogen", which will emit a large amount of carbon dioxide during the production process; "blue hydrogen" can achieve low-carbon hydrogen production; "green hydrogen" uses renewable energy to produce hydrogen, which theoretically has no carbon emissions, so it has a large room for development. At present, my country's hydrogen is mainly gray hydrogen, so how to achieve green production of hydrogen has become a technical problem that needs to be solved urgently.

[0003] Steam methane reforming (SMR) technology and water-gas shift reaction are currently the most common large-scale hydrogen production processes. Despite decades of commercial optimization, the endothermic SMR process is still expensive. In addition, the hydrogen production process produces a large amount of CO2, so CO2 needs to be stored or decarbonized, which will bring additional costs. Although SMR has basic economic and environmental limitations, other hydrogen production pathways, including water electrolysis, are still not comparable to the SMR process on a production scale, so a new hydrogen production method is urgently needed. For example, methane cracking technology is a feasible method for producing hydrogen without producing CO2, but there are still certain technical bottlenecks. During the reaction of methane cracking, the solid carbon particles generated will be deposited on the surface of the solid catalyst, resulting in rapid deactivation of the catalyst; although the liquid catalyst has good durability, it is still in its infancy. Affected by the "cage effect" of the liquid metal solvent on the active site, the catalyst activity is low and the required reaction conditions are relatively harsh.

[0004] In addition to the activity of the catalyst itself, the overall performance of the liquid metal-catalyzed hydrogen production from light alkanes is also severely affected by the poor mass transfer at the gas-liquid interface, due to reasons such as the low solubility of light alkanes in liquid metals, poor convective flow conditions, and strong surface tension effects of liquid metals. Generally, attempts to enhance mass transfer in bubbling bed reactors require strict reaction conditions. For example, increasing the reaction pressure is a common strategy to improve gas solubility, but in the light alkane hydrogen production reaction, according to Le Chatelier's principle, this is not conducive to the production of hydrogen, resulting in a trade-off between mass transfer and thermodynamics in this type of reaction. Therefore, how to simultaneously enhance the intrinsic activity and mass transfer of methane chemical reactions remains an ongoing challenge. Summary of the invention

[0005] To this end, the technical problem to be solved by the present invention is to provide a device and method for producing hydrogen from light alkanes using a ternary liquid metal catalyst based on electromagnetic induction, so as to solve the technical problems of low catalytic activity of the liquid metal catalyst, low methane conversion rate and low energy utilization rate during the reaction when methane is cracked to produce hydrogen, so as to enhance the mass transfer and inherent activity of the methane cracking chemical reaction.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] The device for producing hydrogen from light alkanes using ternary liquid metal catalysts based on electromagnetic induction comprises an electromagnetic induction coil, a bubbling bed reactor and a gas distributor; the electromagnetic induction coil is arranged around the bubbling bed reactor, and the central axis of the electromagnetic induction coil coincides with or is perpendicular to the central axis of the bubbling bed reactor, that is, the direction of the magnetic field generated by the electromagnetic induction coil is parallel or perpendicular to the movement direction of the light alkanes in the bubbling bed reactor; the gas distributor is fixedly installed at the gas inlet end of the bubbling bed reactor; the bubbling bed reactor is filled with a ternary liquid catalyst.

[0008] Theoretically, when the central axis of the electromagnetic induction coil is perpendicular to the central axis of the bubbling bed reactor (i.e., a horizontal magnetic induction coil), it is more conducive to the light alkane cracking hydrogen production reaction, because the upward movement direction (vertical direction) of the bubbles formed by the light alkanes will cause the ternary liquid metal catalyst to have a greater flow in the vertical direction relative to the horizontal direction. According to the principle of the generation of the Lorentz force, a greater Lorentz force will be generated when the movement direction (vertical) is perpendicular to the magnetic field direction (horizontal), making the bubbles easier to break. However, relatively speaking, the device design of the horizontal magnetic induction coil is more difficult. If the catalyst bed is not located inside the horizontal magnetic induction coil, the heating effect is not good. If the catalyst bed is located inside the horizontal magnetic induction coil, the parameters of the reactor and the horizontal magnetic induction coil are greatly limited.

[0009] The above-mentioned device for producing hydrogen from light alkanes by ternary liquid metal catalysis based on electromagnetic induction, the gas distributor includes at least one metal tube and micron-sized pores, and the micron-sized pores are distributed on the tube wall of the metal tube; the open end of the metal tube faces the gas inlet of the bubbling bed reactor, and the closed end of the metal tube faces the gas outlet of the bubbling bed reactor. The light alkane raw gas enters the tubular gas distributor from the lower opening of the metal tube, penetrates from the micron-sized pores to the outside (in the bubbling bed reactor), and the external bubbling bed reactor is filled with the ternary liquid metal catalyst; compared with the traditional lower gas distributor, the bubbles entering the ternary liquid metal catalyst are more and smaller in diameter, which greatly reduces the weakening of the chemical reaction process caused by the reduction of specific surface area caused by the growth of bubbles during the floating process of bubbles, and bubbles penetrate into the ternary liquid metal catalyst throughout the length of the catalyst bed of the bubbling bed reactor, thereby enhancing the utilization rate of the ternary liquid metal catalyst.

[0010] In the above-mentioned electromagnetic induction-based ternary liquid metal catalytic light alkane hydrogen production device, the metal tube is cylindrical, conical or pyramidal; in addition to the cylindrical gas distributor, the present invention changes the shape of the gas distributor for optimization, for example, considering that the pressure at the bottom of the liquid metal catalyst is higher than that at the top, a conical / pyramidal shape with a wide bottom and a narrow top is designed, so that the bubbles are evenly distributed and seeped throughout the height of the catalyst bed, and the design of a wide bottom and a narrow top can effectively avoid the wall effect (the bubbles float faster on the smooth wall, and the time in the catalyst is shortened, which is not conducive to the reaction);

[0011] In order to enhance the contact area between the gas distributor and the ternary liquid metal catalyst, that is, the gas permeation area; the tube wall of the metal tube may be in the shape of a solenoid, which can greatly enhance the surface area of ​​the gas distributor; or, from the closed end of the metal tube to the open end of the metal tube, the tube wall of the metal tube may be alternately concave and convex. This design can enhance the surface area of ​​the gas distributor while enhancing the roughness of the tube wall, thereby reducing the floating speed of the bubbles.

[0012] From the closed end of the metal tube to the open end of the metal tube: the diameters of the micron-sized pores are equal, and the micron-sized pores are evenly distributed on the tube wall of the metal tube;

[0013] Alternatively, from the closed end to the open end of the metal tube: the diameter of the micron-sized pores gradually increases; this design has the following advantages: (1) more uniform gas distribution: the gas flow rate entering from the open end of the gas distributor is higher, and the larger aperture of the open end can ensure that the gas enters the internal pipeline of the gas distributor at a suitable flow rate, thereby effectively reducing the unevenness of the gas flow; at the open end, the larger aperture design can help the gas to enter the internal pipeline of the gas distributor or the bubbling bed reactor evenly; (2) balance of pressure loss: usually when gas enters liquid, the gas flow rate will decrease, and the relatively small aperture of the closed end can cause the gas flow rate to gradually slow down, which can reduce the pressure drop when the gas flows into the liquid and avoid the gas flow penetrating the liquid layer too quickly, resulting in excessive bubbles or uneven gas flow; (3) avoid bubble aggregation or poor gas flow: if the aperture of the open end is too small, the gas may not be able to flow in smoothly, causing blockage or uneven gas flow; while the smaller aperture of the closed end is conducive to the refinement and distribution of bubbles, preventing excessive bubbles from reducing mass transfer efficiency;

[0014] Alternatively, from the closed end to the open end of the metal tube: the distribution density of the micron-sized pores on the tube wall of the metal tube gradually decreases; this design enables the open end of the gas distributor to adapt to the high pressure of the external ternary liquid metal catalyst; and this gradual design can ensure that the flow rate and pressure loss of the gas in the entire distributor are balanced, avoiding local gas flow that is too fast or too slow; since the influence of the high pressure at the open end is compensated, while avoiding excessive or too small gas flow at the closed end, the gas distribution in the entire bubbling bed reactor is more uniform.

[0015] Alternatively, from the closed end of the metal tube to the open end of the metal tube: the diameter of the micron-sized pores gradually increases, and the distribution density of the micron-sized pores on the tube wall of the metal tube gradually decreases.

[0016] In the above-mentioned device for producing hydrogen from light alkanes using ternary liquid metal catalysts based on electromagnetic induction, the aperture of the micron-sized pores is 100-750 μm (due to the high viscosity of the ternary liquid catalyst, when the aperture on the gas distributor is 100-750 μm, the backflow of the ternary liquid metal catalyst can be prevented); the ratio of the height of the metal tube to the bubbling bed reactor is 1:1-10; the ratio of the sum of the outer diameters of the widest parts of all the metal tubes to the inner diameter of the bubbling bed reactor is 1:1-1.2; the gas distributor of this size can make the light alkanes in the ternary liquid catalyst in the bubbling bed reactor The metal tube can be made of titanium alloy material (titanium alloy has strong corrosion resistance and can generate induced current in the alternating magnetic field to achieve eddy current heating, thereby achieving preliminary preheating of the gas entering the gas distributor. In the present invention, the gas distributor made of titanium alloy material can initially heat the internal gas to 100-200°C, which is beneficial to improving the catalytic cracking efficiency of the subsequent entry into the ternary liquid catalyst). The metal tube can also be made of other alloy materials that can achieve eddy current heating in the alternating magnetic field.

[0017] In the above-mentioned device for producing hydrogen from light alkanes using ternary liquid metal catalysts based on electromagnetic induction, the magnetic field generated by the electromagnetic induction coil is an alternating magnetic field, and the frequency range of the alternating magnetic field is 100 to 1000 kHz; or, the magnetic field generated by the electromagnetic induction coil is a pulsed magnetic field, and the pulse frequency of the pulsed magnetic field is 100 to 1000 Hz.

[0018] Traditional external heating methods such as electric heating furnaces mainly use heat conduction to heat the catalyst bed area. The reactor wall (mostly made of materials such as quartz) has a large thermal resistance, which produces a large inverse temperature gradient in the radial direction, resulting in a large amount of heat loss; and because the liquid metal catalyst is corrosive, if a metal with high thermal conductivity is used as a reactor, its durability will be greatly reduced under long-term high-temperature reactions. Compared with industrial fire heating and traditional external heating methods such as electric heating furnaces, the present invention uses electromagnetic induction heating as a heating method to directly heat the ternary liquid metal catalyst, and uses eddy current heating (using the high conductivity of the nickel-bismuth-indium ternary liquid metal) and hysteresis heating (nickel in the ternary liquid metal catalyst is a ferromagnetic metal element, and indium has weak ferromagnetism and antiferromagnetism, both of which will produce hysteresis thermal effects) to directly heat the catalyst, which not only avoids a large amount of heat loss in the heat transfer process, but also eliminates carbon dioxide emissions.

[0019] Alternating magnetic fields are more conducive to the cracking of light alkanes to produce hydrogen. First of all, in terms of the heating mechanism (heat transfer), a constant magnetic field cannot heat spontaneously. Alternating magnetic fields and pulsed magnetic fields can use the Faraday electromagnetic induction principle to induce current to flow in the ternary liquid metal catalyst, thereby producing the effect of Joule heating and achieving the purpose of heating. A constant magnetic field requires an additional heat source in the form of external heating. However, due to the relatively concentrated instantaneous energy release of the pulsed magnetic field, local overheating may occur, especially when the pulse frequency is high. The pulsed magnetic field may cause uneven heating, especially when the material is not completely cooled between multiple pulses. A large temperature gradient is prone to occur. In comparison, alternating magnetic fields are suitable for continuous and uniform heating.

[0020] For mass transfer, the frequency of the alternating magnetic field determines the rate of change of the induced current. Usually, a high-frequency alternating magnetic field will lead to a strong eddy current effect, which causes the bubbles in the liquid to be subjected to a strong force, which may cause the bubbles to produce complex movement phenomena in the liquid metal and be easier to break. The Lorentz force in a constant magnetic field is relatively weak and usually does not change the shape of the bubbles, but only slightly affects the movement trajectory of the bubbles. The effect of the pulsed magnetic field on the bubbles is mainly reflected in the instantaneous and strong change of the Lorentz force generated during the pulse process, which causes the bubbles to vibrate rapidly, change their shape or partially rupture.

[0021] In general, the alternating magnetic field maintains a high degree of stability and controllability in both heat transfer and mass transfer, which is more conducive to methane cracking to produce hydrogen, but the pulsed magnetic field also has great development potential.

[0022] The above-mentioned device for producing hydrogen from light alkanes using ternary liquid metal catalysts based on electromagnetic induction also includes an infrared thermometer, a gas chromatograph and a data acquisition system; the temperature probe of the infrared thermometer is aimed at the ternary liquid catalyst in the bubbling bed reactor, and the signal output end of the infrared thermometer is signal-connected to the temperature signal input end of the data acquisition system; the gas input end of the gas chromatograph is fluid-connected to the gas outlet end of the bubbling bed reactor, and the signal output end of the gas chromatograph is signal-connected to the chromatographic signal input end of the data acquisition system.

[0023] The invention discloses a method for producing hydrogen from light alkanes by ternary liquid metal catalysis based on electromagnetic induction. The method adopts the above-mentioned ternary liquid metal catalysis light alkane hydrogen production device based on electromagnetic induction, uses nickel bismuth-indium complex (NiBi-In) as a ternary liquid metal catalyst, uses electromagnetic induction heating as a heating method to directly heat the ternary liquid metal catalyst, and introduces light alkanes into the ternary liquid metal catalyst for cracking and hydrogen production.

[0024] The above-mentioned method for producing hydrogen from light alkanes using ternary liquid metal catalysts based on electromagnetic induction, and the method for preparing the ternary liquid metal catalyst nickel bismuth-indium complex comprise the following steps:

[0025] Step (1), adding a calcined product obtained by calcining a nickel salt in an air atmosphere into deionized water and dispersing the mixture uniformly to obtain a dispersion A;

[0026] Step (2), adding bismuth salt to dispersion A and performing ultrasonic mixing to obtain dispersion B;

[0027] Step (3), placing the dispersion B in a vacuum drying oven to remove moisture to obtain a solid mixture A;

[0028] Step (4), calcining the solid mixture A in an air atmosphere to obtain a catalyst precursor;

[0029] Step (5), grinding the catalyst precursor and mixing it evenly with metal indium particles to obtain a solid mixture B;

[0030] Step (6), placing the solid mixture B in a reducing atmosphere for reduction reaction, and naturally cooling to room temperature after the reduction reaction is completed, thereby obtaining a ternary liquid metal catalyst nickel bismuth-indium complex.

[0031] Compared with solid metal catalysts of transition metals (Ni, Co, Fe, etc.), the present invention uses a ternary liquid metal catalyst NiBi-In for catalytic dehydrogenation. Due to the high density of the liquid catalyst, the solid carbon generated during the catalytic process will float to the surface of the catalyst bed, which is convenient for removal at any time, thereby effectively avoiding the reduction of catalyst activity or even deactivation caused by carbon deposition and coking of traditional solid metal catalysts; and the generated byproduct solid carbon can be collected and reprocessed and applied to light industry, batteries and other fields. Therefore, the ternary liquid metal catalyst NiBi-In prepared by the present invention has the triple function of "heating-catalysis-decarbonization". Compared with the existing binary liquid metal catalyst (a single solute element is generally unable to be distributed at the gas-liquid reaction interface), the ternary liquid metal catalyst NiBi-In prepared by the method of the present invention can give full play to the synergistic effect between the metal elements (especially the regulation effect of the Bi element on the electronic distribution and spatial interface distribution of the Ni element) and effectively enhance the distribution of catalytic active sites at the gas-liquid reaction interface of the two-phase flow, thereby significantly improving the catalytic cracking activity of NiBi-In for light alkanes.

[0032] In the above-mentioned method for producing hydrogen from light alkanes using ternary liquid metal catalysts based on electromagnetic induction, in step (1), the nickel salt is one or a mixture of two or more of nickel acetate, nickel nitrate and nickel sulfate; the calcination conditions of the nickel salt are: calcination at a temperature of 400 to 600° C. for 2 to 3 hours; compared with commercially available nickel oxide, the nickel oxide particles prepared by calcining the nickel salt under the above-mentioned calcination conditions have a moderate size, which is conducive to the subsequent composite with bismuth salt and indium particles to obtain a ternary liquid metal catalyst NiBi-In with high catalytic activity; the concentration of nickel element in the dispersion A is 0.5 to 1.0 mol / L;

[0033] In step (2), the bismuth salt is one or a mixture of two or more of bismuth acetate, bismuth chloride and bismuth nitrate; in dispersion B, the molar ratio of nickel element to bismuth element is 2 to 4:1; and the ultrasonic mixing time is 10 to 20 minutes;.

[0034] In step (3), the vacuum drying conditions are: drying at a temperature of 110 to 120° C. for 10 to 12 hours;

[0035] In step (4), the calcination conditions are: calcination at a temperature of 400 to 600° C. for 2 to 3 hours;

[0036] In step (5), the particle size of the catalyst precursor after grinding is 10 to 100 μm; the particle size of the metal indium particles is 1 to 2 mm; if the catalyst precursor obtained by calcination is not ground, it will affect its full mixing with the metal indium particles, thereby affecting the subsequent reduction effect; controlling the size of the catalyst precursor and the metal indium particles within the above range is conducive to ensuring the uniformity of the mixing of the two; in the solid mixture B, the molar ratio of nickel element to indium element is 1:10 to 12; when preparing the ternary liquid catalyst NiBi-In, if the nickel content is too high, the finally prepared NiBi-In cannot form a stable liquid alloy, and may form a partial solid alloy, which not only fails to make the by-product carbon float but also If the nickel content is too low, the active sites will be too few, resulting in low catalytic activity of the ternary liquid catalyst. In addition, bismuth is a low melting point metal. If the amount of bismuth is too much, a solvent cage effect will be formed, which will hinder the interfacial distribution of the active sites of the prepared ternary liquid catalyst. However, if the amount of bismuth is too little, the regulating effect of Bi on Ni will be limited, which will affect the catalytic activity of the ternary liquid catalyst. The present invention strictly controls the ratio of nickel, bismuth and indium, so that the three elements can fully exert their synergistic effect and improve the catalytic activity of NiBi-In for hydrogen production by cracking light alkanes.

[0037] In step (6), the reducing atmosphere is a mixed gas formed by hydrogen and argon in a ratio of 1 to 2:1 (at this ratio, the mixed gas has a better reducing effect on the solid mixture B and has a lower safety hazard); the conditions for the reduction reaction are: heating from room temperature to 700 to 800°C at a heating rate of 3 to 5°C / min, and maintaining at a reduction temperature of 700 to 800°C for 2 to 3 hours. The melting point of the liquid alloy is low. If the temperature is raised too fast during the reduction reaction, the liquid metal may not be able to effectively dissolve the Ni and Bi elements. However, at a heating rate of 3 to 5°C / min, NiO and Bi2O3 can be reduced and dissolved in the liquid metal; if the reduction temperature is too low, the reduction is insufficient and the activity of the catalyst is affected. If the reduction temperature is too high, the nickel will agglomerate and the activity of the catalyst will also be affected. The present invention strictly controls the heating rate, reduction temperature and reduction time of the reduction reaction, so that nickel, bismuth and indium are combined to form a ternary liquid catalyst with an ideal active site interface distribution.

[0038] In the above-mentioned method for producing hydrogen from light alkanes using ternary liquid metal catalysts based on electromagnetic induction, in step (1), the nickel salt is nickel nitrate hexahydrate, and the calcination conditions are: calcination at 500° C. for 2 h (if the calcination temperature is lower than 500° C., the nickel nitrate hexahydrate will be insufficiently calcined, and nitrate will remain in the calcined product, which will affect the subsequent compounding of the ternary liquid catalyst; if the calcination temperature is higher than 500° C., the particle size of the calcined product will be too large, which will affect the subsequent preparation of the ternary liquid catalyst and further affect its catalytic activity); the content of nickel element in the dispersion A is 0.66 mol / L;

[0039] In step (2), the bismuth salt is bismuth nitrate pentahydrate; the ultrasonic mixing time is 20 minutes; in dispersion B, the molar ratio of nickel element to bismuth element is 3:1;

[0040] In step (3), the vacuum drying conditions are: drying at 120° C. for 10 h;

[0041] In step (4), the calcination conditions are: calcination at 500°C for 2h;

[0042] In step (5), the particle size of the catalyst precursor after grinding is 100 μm; the particle size of the metal indium particles is 1 to 2 μm; in the solid mixture B, the molar ratio of nickel element to indium element is 1:10;

[0043] In step (6), the reducing atmosphere is a mixture of hydrogen and argon in a ratio of 2:1; the conditions for the reduction reaction are: heating from room temperature to 700°C at a heating rate of 3°C / min, and maintaining the reduction temperature at 700°C for 2h.

[0044] Existing liquid metal catalysts are mostly prepared by directly mixing metal elements in alloy proportions and then heating them under an inert gas or hydrogen atmosphere. However, the present invention premixes the solute elements Ni and Bi evenly by a method of synthesizing precursors, so that when the solvent element In is incorporated, the Bi element can fully exert its regulatory effect (regulating the electronic distribution of the active element Ni and the spatial interface distribution). Otherwise, uneven mixing may cause phase segregation of the elements, thereby affecting the synergistic effect between the elements in the ternary liquid metal catalyst NiBi-In, and further affecting its catalytic activity. The present invention adjusts the ratio of the three metal elements Ni, Bi and In within a specific range, so that the ternary liquid metal catalyst NiBi-In not only exhibits a higher and more stable catalytic activity when catalyzing light alkanes, but also significantly improves its magneto-thermal-chemical conversion efficiency using electromagnetic energy in a high-frequency magnetic field (100 to 1000kHz).

[0045] In the above-mentioned method for producing hydrogen from light alkanes by ternary liquid metal catalysis based on electromagnetic induction, the frequency range of electromagnetic induction heating is 100-1000kHz (preferably 400-800kHz); the reaction temperature is 700-900°C, and the reaction space velocity is 10-10000h -1 (Preferably 200 to 1200 hours -1 ), the flow rate of the light alkane is 1 to 100 mL / min (preferably 2 to 10 mL / min), and the reaction pressure is greater than or equal to standard atmospheric pressure; the light alkane is one or a mixture of two or more of methane, ethane or propane.

[0046] When light alkanes are used to produce hydrogen, the raw gas in the bubbling bed reactor enters from the lower inlet of the reactor, and the reaction products are discharged from the upper outlet of the reactor. Since the bubble floating process is a process of bubble growth and aggregation, the bubble volume of the raw gas bubbles increases and the specific surface area decreases during the floating process, which is not conducive to the contact between the raw gas and the liquid metal catalyst, thereby affecting the conversion rate of the cracking reaction. However, in a high-frequency magnetic field, the liquid metal catalyst is squeezed by the Lorentz force, and the bubbles are deformed or even broken, and the specific surface area increases, thereby enhancing mass transfer and chemical reactions. The present invention controls the frequency of electromagnetic induction heating within the range of 100 to 1000 kHz, so that the prepared ternary liquid metal catalyst NiBi-In can fully squeeze and crush the bubbles formed in the floating process of light alkanes (methane, ethane or propane) under the action of the Lorentz force of the magnetic field, thereby greatly reducing the diameter size of the floating bubbles, thereby promoting the mass transfer process of the two-phase flow, and improving the conversion rate and reaction rate of the light alkanes; and, when the reaction temperature is 700 to 900°C and the reaction space velocity is 200 to 1200h -1Under the reaction conditions of "the flow rate of light alkane is 2 to 10 mL / min, and the reaction pressure is greater than or equal to standard atmospheric pressure", the ternary liquid metal catalyst prepared by the present invention can effectively reduce the generation of local hot spots after the light alkane is introduced, and the cracking reaction of the light alkane in the reactor is more uniform, thereby effectively reducing the occurrence of side reactions (side reactions will generate substances such as ethane, ethylene, acetylene, and aromatic hydrocarbons, which not only affect the conversion rate of light alkanes but also pollute the catalyst and affect the catalyst activity).

[0047] The technical solution of the present invention achieves the following beneficial technical effects:

[0048] 1. The method for producing hydrogen from light alkanes using a ternary liquid metal catalyst based on electromagnetic induction of the present invention uses a synthesized ternary liquid metal catalyst NiBi-In as a heating medium, and adopts an electromagnetic induction heating method as a heat source for dehydrogenation of light alkanes to directly heat the ternary liquid metal catalyst; during the entire catalytic reaction process, Ni is used as an active metal, Bi is used as a regulating metal, and In is used as a solvent metal, and the various metal elements work synergistically, which significantly improves the distribution of catalytic active sites at the gas-liquid reaction interface of the two-phase flow, so that the catalytic effect of the ternary liquid metal catalyst can be fully exerted, thereby improving the conversion rate of light alkanes.

[0049] 2. The NiBi-In complex synthesized by the method of the present invention is used as a ternary liquid metal catalyst to catalyze hydrogen production from methane. After 100 hours of experimental testing, the reaction temperature is 800°C, 1atm (standard atmospheric pressure) and 240h. -1 Under the reaction conditions of space velocity, when the electric heating furnace is used as the heating method, it has 0.097mL H2 g -1 min -1 When electromagnetic induction heating is used as the heating method, the hydrogen generation rate can reach 0.227mL H2 g -1 min -1 , which is five times that of the best liquid metal catalyst NiMo-Bi (0.046mL H2 g -1 min -1 The present invention further optimizes the space velocity conditions and finds that the electromagnetic induction driven ternary liquid catalyst NiBi-In catalyzes methane cracking to produce hydrogen at a reaction temperature of 800°C, 1atm (standard atmospheric pressure) and 1150h -1 Under the reaction conditions, the catalytic hydrogen generation rate can reach 0.497mL H2 g -1 min -1This shows that there is still a lot of room for optimization in the process of electromagnetic induction-driven ternary liquid catalyst NiBi-In catalytic methane cracking to produce hydrogen; for example, the greater the pressure, the higher the reaction efficiency; the higher the catalytic bed, the longer the gas passes through the catalyst, and the more complete the reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 Schematic diagram of the reaction system for producing hydrogen from methane using ternary liquid metal catalysis based on electromagnetic induction in Example 1 of the present invention;

[0051] Figure 2 Schematic diagram of a ternary liquid metal catalytic methane hydrogen production device based on electromagnetic induction in Example 1 of the present invention;

[0052] Figure 3 A schematic diagram of a gas distributor in a ternary liquid metal catalytic methane hydrogen production device based on electromagnetic induction in Example 1 of the present invention;

[0053] Figure 4 Schematic diagram of a ternary liquid metal catalytic methane hydrogen production device based on electromagnetic induction in other embodiments of the present invention;

[0054] Figure 5 Schematic diagram of the electromagnetic induction coil of the ternary liquid metal catalytic methane hydrogen production device based on electromagnetic induction in other embodiments of the present invention;

[0055] Figure 6 A schematic diagram of a gas distributor in a ternary liquid metal catalytic methane hydrogen production device based on electromagnetic induction in Example 4 of the present invention;

[0056] Figure 7 Schematic diagram of the tube wall of the gas distributor in the ternary liquid metal catalytic methane hydrogen production device based on electromagnetic induction in other embodiments of the present invention;

[0057] Figure 8 A comparison chart of hydrogen generation rate and methane conversion rate of the ternary liquid metal catalytic methane hydrogen production method based on electromagnetic induction in Example 1 of the present invention;

[0058] Fig. 9 Actual picture of the size of bubbles formed by methane in electromagnetic induction heating in Example 1 of the present invention;

[0059] Fig.10 Actual photo of the size of bubbles formed by methane in the external electric heating method in Comparative Example 1 of the present invention;

[0060] Fig.11 A comparison chart of the hydrogen generation rate of the ternary liquid metal catalytic methane hydrogen production method based on electromagnetic induction in some embodiments of the present invention and the existing hydrogen production method;

[0061] Fig.12CFD simulation test results of the size of bubbles formed by methane in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0062] Example 1

[0063] The schematic diagram of the device for producing hydrogen from methane using ternary liquid metal catalysis based on electromagnetic induction in this embodiment is shown in Figure 1 , comprising an electromagnetic induction coil, a bubbling bed reactor and a gas distributor; the electromagnetic induction coil is arranged around the bubbling bed reactor, and the central axis of the electromagnetic induction coil coincides with the central axis of the bubbling bed reactor; the gas distributor is fixedly installed at the gas inlet end of the bubbling bed reactor; the bubbling bed reactor is filled with a ternary liquid catalyst.

[0064] like Figure 2 and Figure 3 As shown, the gas distributor includes a metal tube and micron-sized pores, and the micron-sized pores are distributed on the tube wall of the metal tube; the open end of the metal tube faces the gas inlet of the bubbling bed reactor, and the closed end of the metal tube faces the gas outlet of the bubbling bed reactor; the metal tube is cylindrical, the diameters of the micron-sized pores are equal, and the micron-sized pores are evenly distributed on the tube wall of the metal tube. The pore diameter of the micron-sized pores is 500μm; the ratio of the height of the metal tube to the bubbling bed reactor is 1:2; the ratio of the outer diameter of the metal tube to the inner diameter of the bubbling bed reactor is 1:1.2; the metal tube is made of titanium alloy material.

[0065] In some other embodiments, the reaction system further comprises an infrared thermometer, a gas chromatograph and a data acquisition system; the temperature probe of the infrared thermometer is aimed at the ternary liquid catalyst in the bubbling bed reactor, and the signal output end of the infrared thermometer is signal-connected to the temperature signal input end of the data acquisition system; the gas input end of the gas chromatograph is fluid-connected to the gas outlet end of the bubbling bed reactor, and the signal output end of the gas chromatograph is signal-connected to the chromatographic signal input end of the data acquisition system (see Figure 4 ).

[0066] This embodiment is a method for producing hydrogen from methane using a ternary liquid metal catalyst based on electromagnetic induction. A nickel-bismuth-indium complex is used as a ternary liquid metal catalyst, and electromagnetic induction heating is used as a heating method to directly heat the ternary liquid metal catalyst. Methane is introduced into the ternary liquid metal catalyst to crack and produce hydrogen. The solid carbon generated by the reaction floats to the surface of the catalytic bed of the ternary liquid metal catalyst, which is convenient for removal, recycling and reuse.

[0067] In some other embodiments, the magnetic induction coil may be arranged horizontally so that the central axis of the electromagnetic induction coil is perpendicular to the central axis of the bubbling bed reactor. Figure 5 As shown. However, if the entire catalyst bed is to be placed inside the magnetic induction coil (in the middle), the outer diameter of the bubbling bed reactor should be less than half of the pitch, and its height should be less than the diameter of the magnetic induction coil. This method has high requirements for the size of the bubbling bed reactor and the parameters of the magnetic induction coil. However, if the entire catalyst bed is located outside the magnetic induction coil (placed in parallel), the magnetic field strength outside the coil is weak, the magnetic effect is low, and heating is difficult.

[0068] The preparation method of the ternary liquid metal catalyst (NiBi-In complex) in this embodiment is:

[0069] 1.92g of nickel nitrate hexahydrate (NiN2O6·6H2O) was weighed and calcined for 2h in an air atmosphere at 500℃ to generate nickel oxide. After cooling naturally, it was taken out and evenly dispersed in 10mL of deionized water. Then 1.07g of bismuth nitrate pentahydrate (BiN3O9·5H2O) was added to the water and ultrasonically mixed for 20min. After the ultrasonication, it was placed in a vacuum drying oven at 120℃ for 10h to remove moisture, and the obtained solid mixture was calcined for 2h in an air atmosphere at 500℃ to obtain a catalyst precursor. The catalyst precursor was ground to a particle size of 100 μm, physically mixed with 7.65 g of metal indium (In) with a particle size of 1 to 2 mm, and reduced in an atmosphere of hydrogen and argon (the volume ratio of hydrogen to argon is 2:1). The temperature was increased from room temperature to 700°C at a heating rate of 3°C / 1min, and maintained at the reduction temperature of 700°C for 2 hours. After natural cooling, the catalyst was taken out to obtain a ternary liquid metal catalyst (NiBi-In complex).

[0070] The reaction conditions of this embodiment are: the frequency of electromagnetic induction heating is 400kHz; the reaction temperature is 800°C, and the reaction space velocity is 240h -1 (The flow rate of methane is 4 mL / min, without carrier gas), and the reaction pressure is 1 atm (standard atmospheric pressure).

[0071] Example 2

[0072] The only difference between this embodiment and embodiment 1 is that when preparing the ternary liquid metal catalyst (NiBi-In complex), the dosage ratio of nickel nitrate hexahydrate, bismuth nitrate pentahydrate and metallic indium is changed so that the molar ratio of the three elements Ni-Bi-In in the finally prepared ternary liquid metal catalyst is 5:1:65.

[0073] The other process steps, process parameters, raw materials and equipment are exactly the same as those in Example 1.

[0074] Example 3

[0075] The only difference between this embodiment and embodiment 1 is: the preparation method of the ternary liquid metal catalyst (NiBi-In complex): nickel oxide, metal bismuth powder and metal indium powder are mixed in a molar ratio of 3:1:30 of the three elements of Ni-Bi-In, placed in a hydrogen reducing atmosphere at 700°C for 2h, and cooled to room temperature after the reaction to obtain the ternary liquid metal catalyst (NiBi-In complex).

[0076] The other process steps, process parameters, raw materials and equipment are exactly the same as those in Example 1.

[0077] Example 4

[0078] The difference between this embodiment and embodiment 1 is only that:

[0079] 1. The gas distributor used in the reaction system is as follows: Figure 6 In some other embodiments, the ternary liquid metal catalytic methane hydrogen production device based on electromagnetic induction can also use a tube wall such as Figure 7 The gas distributor shown can achieve better catalytic reaction effects.

[0080] 2. The reaction conditions for methane cracking to produce hydrogen are: the frequency of electromagnetic induction heating is 400kHz; the reaction temperature is 800℃, and the reaction space velocity is 1150h -1 (The flow rate of methane is 4 mL / min, and the flow rate of carrier gas nitrogen is 14 mL / min), and the reaction pressure is 1 atm (standard atmospheric pressure).

[0081] The other process steps, process parameters, raw materials and equipment are exactly the same as those in Example 1.

[0082] Comparative Example 1

[0083] In the method for producing hydrogen from methane using liquid metal catalysts in this comparative example, a NiBi-In complex is used as a ternary liquid metal catalyst, an external electric heating furnace is used as a heating method to indirectly heat the ternary liquid metal catalyst, and methane is introduced into the ternary liquid metal catalyst for cracking and producing hydrogen. The preparation method of the ternary liquid metal catalyst NiBi-In complex in this comparative example is exactly the same as that in Example 1.

[0084] The reaction conditions of this comparative example are: reaction temperature is 800°C, reaction space velocity is 240h -1 (The flow rate of methane is 4 mL / min, without carrier gas), and the reaction pressure is 1 atm (standard atmospheric pressure).

[0085] The other process steps, process parameters, raw materials and equipment are exactly the same as those in Example 1.

[0086] Comparative Example 2

[0087] The method for producing hydrogen from methane using liquid metal catalysis in this comparative example uses a NiMo-Bi complex as a ternary liquid metal catalyst, uses an external electric heating furnace as a heating method to indirectly heat the ternary liquid metal catalyst, and introduces methane into the ternary liquid metal catalyst for cracking and producing hydrogen. The preparation method of the NiMo-Bi complex is as follows: nickel oxide, molybdenum oxide and bismuth particles are mixed and placed in a hydrogen atmosphere for heating (700° C.) reduction for 2 hours; the mass fraction of bismuth in the NiMo-Bi complex is 96.4wt%, and the molar ratio of nickel to molybdenum is 3:1.

[0088] The reaction conditions of this comparative example are: reaction temperature is 800°C, reaction space velocity is 240h -1 (The flow rate of methane is 4 mL / min, without carrier gas), and the reaction pressure is 1 atm (standard atmospheric pressure).

[0089] The other process steps, process parameters, raw materials and equipment are exactly the same as those in Example 1.

[0090] The catalytic performance and energy utilization of the hydrogen production methods of Examples 1 to 3 and Comparative Examples 1 to 2 were tested for 100 hours. The results are shown in Tables 1 and Figure 8 .

[0091] Table 1

[0092]

[0093] The power utilization rate in Table 1 is used to evaluate the electrical (magnetic)-thermal-chemical conversion efficiency of the methane hydrogen production reaction system. Fig. 9 and Fig.10 ), as can be seen from the figure, using 400kHz electromagnetic induction heating to directly heat the ternary liquid metal catalyst (NiBi-In complex) can significantly reduce the size of bubbles formed during the methane floating process.

[0094] Fig.11 This is a comparison chart of some hydrogen generation rates in Table 1. Fig.11 In addition to the hydrogen generation rates of Example 1 [NiBi-In(IH)], Comparative Example 1 [NiBi-In(EH)] and Comparative Example 2 [NiMo-Bi], the catalytic activities of some existing common liquid metal catalysts are also experimentally compared. In view of the significantly poor catalytic effects exhibited by these catalysts, they are not listed here one by one.

[0095] The CFD simulation of the size of methane in the reaction system in Example 1 and Comparative Example 1 is as follows: Fig.12 As shown. Fig.11It can be seen that the ternary liquid metal in the high-frequency magnetic field (400kHz) is subjected to the intensified movement of the Lorentz force, and the bubble interface is subjected to the liquid metal Lorentz force (F L ) is squeezed, when the bubble surface tension (F S ) is not enough to resist, resulting in bubble rupture and small bubble size.

[0096] The method of the above embodiment can also be used for cracking light alkanes such as ethane or propane to produce hydrogen. The factors affecting the hydrogen generation rate are similar to those in the above embodiment for cracking methane, and no examples are given here.

[0097] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. A device for producing hydrogen from light alkanes using ternary liquid metal catalysis based on electromagnetic induction, characterized in that: It comprises an electromagnetic induction coil, a bubbling bed reactor and a gas distributor; the electromagnetic induction coil is arranged around the bubbling bed reactor, and the central axis of the electromagnetic induction coil coincides with or is perpendicular to the central axis of the bubbling bed reactor, that is, the direction of the magnetic field generated by the electromagnetic induction coil is parallel to or perpendicular to the movement direction of the light alkanes in the bubbling bed reactor; the gas distributor is fixedly installed at the gas inlet end of the bubbling bed reactor; the bubbling bed reactor is filled with a ternary liquid catalyst.

2. The device for producing hydrogen from light alkanes using ternary liquid metal catalysis based on electromagnetic induction according to claim 1 is characterized in that: The gas distributor includes at least one metal tube and micron-sized pores, wherein the micron-sized pores are distributed on the tube wall of the metal tube; the open end of the metal tube faces the gas inlet of the bubbling bed reactor, and the closed end of the metal tube faces the gas outlet of the bubbling bed reactor.

3. The device for producing hydrogen from light alkanes using ternary liquid metal catalysis based on electromagnetic induction according to claim 2 is characterized in that: The metal tube is cylindrical, conical or pyramidal; or, the tube wall of the metal tube is in the shape of a solenoid; or, from the closed end to the open end of the metal tube, the tube wall of the metal tube is alternately concave and convex; From the closed end of the metal tube to the open end of the metal tube: the diameters of the micron-sized pores are equal, and the micron-sized pores are evenly distributed on the tube wall of the metal tube; Alternatively, from the closed end of the metal tube to the open end of the metal tube: the diameter of the micrometer-sized pores gradually increases; Alternatively, from the closed end of the metal tube to the open end of the metal tube: the distribution density of the micrometer-sized pores on the tube wall of the metal tube gradually decreases; Alternatively, from the closed end of the metal tube to the open end of the metal tube: the diameter of the micron-sized pores gradually increases, and the distribution density of the micron-sized pores on the tube wall of the metal tube gradually decreases.

4. The device for producing hydrogen from light alkanes using ternary liquid metal catalysis based on electromagnetic induction according to claim 2 is characterized in that: The aperture of the micron-sized pores is 100 to 750 μm; the ratio of the height of the metal tube to the bubbling bed reactor is 1:1 to 10; the ratio of the sum of the outer diameters of the widest parts of all the metal tubes to the inner diameter of the bubbling bed reactor is 1:1 to 1.2; and the metal tube is made of titanium alloy material.

5. The device for producing hydrogen from light alkanes using ternary liquid metal catalysis based on electromagnetic induction according to any one of claims 1 to 4, characterized in that: The magnetic field generated by the electromagnetic induction coil is an alternating magnetic field, and the frequency range of the alternating magnetic field is 100 to 1000 kHz; Alternatively, the magnetic field generated by the electromagnetic induction coil is a pulsed magnetic field, and the pulse frequency of the pulsed magnetic field is 100 to 1000 Hz.

6. The device for producing hydrogen from light alkanes using ternary liquid metal catalysis based on electromagnetic induction according to any one of claims 1 to 4, characterized in that: It also includes an infrared thermometer, a gas chromatograph and a data acquisition system; the temperature probe of the infrared thermometer is aimed at the ternary liquid catalyst in the bubbling bed reactor, and the signal output end of the infrared thermometer is signal-connected with the temperature signal input end of the data acquisition system; the gas input end of the gas chromatograph is fluid-connected with the gas outlet end of the bubbling bed reactor, and the signal output end of the gas chromatograph is signal-connected with the chromatographic signal input end of the data acquisition system.

7. A method for producing hydrogen from light alkanes using ternary liquid metal catalysis based on electromagnetic induction, characterized in that: The electromagnetic induction-based ternary liquid metal catalytic light alkane hydrogen production device as claimed in claim 1 is used, a nickel-bismuth-indium complex is used as a ternary liquid metal catalyst, the ternary liquid metal catalyst is directly heated by electromagnetic induction heating as a heating method, and light alkanes are introduced into the ternary liquid metal catalyst for cracking and hydrogen production.

8. The method for producing hydrogen from light alkanes using ternary liquid metal catalysis based on electromagnetic induction according to claim 7, characterized in that: The preparation method of the nickel bismuth-indium composite comprises the following steps: Step (1), adding a calcined product obtained by calcining a nickel salt in an air atmosphere into deionized water and dispersing the mixture uniformly to obtain a dispersion A; Step (2), adding bismuth salt to dispersion A and performing ultrasonic mixing to obtain dispersion B; Step (3), placing the dispersion B in a vacuum drying oven to remove moisture to obtain a solid mixture A; Step (4), calcining the solid mixture A in an air atmosphere to obtain a catalyst precursor; Step (5), grinding the catalyst precursor and mixing it evenly with metal indium particles to obtain a solid mixture B; Step (6), placing the solid mixture B in a reducing atmosphere for reduction reaction, and naturally cooling to room temperature after the reduction reaction is completed, thereby obtaining a ternary liquid metal catalyst nickel bismuth-indium complex.

9. The method for producing hydrogen from light alkanes using ternary liquid metal catalysis based on electromagnetic induction according to claim 8, characterized in that: In step (1), the nickel salt is one or a mixture of two or more of nickel acetate, nickel nitrate and nickel sulfate; the calcination conditions of the nickel salt are: calcination at a temperature of 400 to 600° C. for 2 to 3 hours; the concentration of nickel element in the dispersion A is 0.5 to 1.0 mol / L; In step (2), the bismuth salt is one or a mixture of two or more of bismuth acetate, bismuth chloride and bismuth nitrate; in dispersion B, the molar ratio of nickel element to bismuth element is 2 to 4:1; and the ultrasonic mixing time is 10 to 20 minutes; In step (3), the vacuum drying conditions are: drying at a temperature of 110 to 120° C. for 10 to 12 hours; In step (4), the calcination conditions are: calcination at a temperature of 400 to 600° C. for 2 to 3 hours; In step (5), the particle size of the catalyst precursor after grinding is 10 to 100 μm; the particle size of the metal indium particles is 1 to 2 mm; in the solid mixture B, the molar ratio of nickel element to indium element is 1:10 to 12; In step (6), the reducing atmosphere is a mixture of hydrogen and argon in a ratio of 1 to 2:1; the conditions for the reduction reaction are: heating from room temperature to 700 to 800°C at a heating rate of 3 to 5°C / min, and maintaining the reduction temperature of 700 to 800°C for 2 to 3h.

10. The method for producing hydrogen from light alkanes using ternary liquid metal catalysis based on electromagnetic induction according to any one of claims 7 to 9, characterized in that: The frequency range of electromagnetic induction heating is 100 to 1000kHz; The reaction temperature is 700-900°C, and the reaction space velocity is 10-10000h -1 The flow rate of the light alkane is 1-100 mL / min, and the reaction pressure is greater than or equal to standard atmospheric pressure; the light alkane is one or a mixture of two or more of methane, ethane or propane.

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