CN117299137A - Shell-core structure catalyst for preparing synthesis gas by reforming methane and carbon dioxide, and preparation method and application thereof - Google Patents

Shell-core structure catalyst for preparing synthesis gas by reforming methane and carbon dioxide, and preparation method and application thereof Download PDF

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CN117299137A
CN117299137A CN202311039607.6A CN202311039607A CN117299137A CN 117299137 A CN117299137 A CN 117299137A CN 202311039607 A CN202311039607 A CN 202311039607A CN 117299137 A CN117299137 A CN 117299137A
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catalyst
carbon
shell
core
carbon dioxide
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刘大伟
许明
裴思佳
洪传勋
刘小凤
徐龙
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NORTHWEST UNIVERSITY
Shaanxi Xixian New Area Environmental Group Co ltd
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Shaanxi Xixian New Area Environmental Group Co ltd
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Abstract

The invention discloses a shell-core structure catalyst for preparing synthesis gas by reforming methane and carbon dioxide, and a preparation method and application thereof, and belongs to the technical field of catalysts. The method of the invention adopts an atomic layer deposition method or an immersion method to load metal on the surface of nano-sized silicon oxide, prepares the carbonaceous catalyst with a core-shell structure through a Pickering emulsion template method, and finally prepares a finished product through simple processes of filtering, washing, drying, etching and roasting, wherein the finally prepared catalyst consists of nickel, auxiliary metal and carbon. The invention adopts nickel, carbon and other raw materials, has wide sources and low cost. The method has the advantages of simple process, simple equipment and low production cost; the prepared product has high catalytic activity and high conversion rate of methane and carbon dioxide; good carbon deposit resistance and stability, etc. The catalyst can be widely used as a catalyst for preparing synthesis gas by reforming methane and carbon dioxide.

Description

Shell-core structure catalyst for preparing synthesis gas by reforming methane and carbon dioxide, and preparation method and application thereof
Technical Field
The invention belongs to the technical field of catalysts, in particular to the technical field of catalyst preparation for preparing synthesis gas by reforming methane and carbon dioxide, and more particularly relates to a shell-core structure catalyst for preparing synthesis gas by reforming methane and carbon dioxide, and a preparation method and application thereof.
Background
CO 2 Is widely regarded as the basic source of global climate warming and realizes CO 2 The method is converted and utilized, so that the method becomes a sustainable C1 resource, and has profound significance for improving global climate problems. Currently, CO 2 One of the chemical conversion pathways of (a) is CO 2 And CH (CH) 4 Catalytic reforming to produce synthesis gas, the reaction not only can realize simultaneous conversion of CH 4 And CO 2 These two greenhouse gases and the reaction system generates H 2 The synthesis gas with the pressure of/CO being approximately equal to 1 can be directly used as a raw material for oxo synthesis and Fischer-Tropsch synthesis.
CH 4 -CO 2 The reforming catalyst is mainly a supported catalyst, and a catalyst using non-noble metal Ni as an active component is widely used. However, ni-based catalysts are susceptible to deactivation in long-term high temperature reactions, mainly because of two points: (1) Carbon deposition on the surface of the catalyst, and carbon species which are difficult to eliminate by oxidation can block catalyst gaps, so that the activity of the catalyst is reduced or even deactivated; (2) The Ni active component is sintered at high temperature so that the specific surface area and the number of active sites of the active component are significantly reduced to cause deactivation. Encapsulation of Ni nanoparticles inside a support has been widely recognized as a strategy for preparing methane dry reforming catalysts with excellent anti-sintering and anti-carbon properties. However, these shell-and-core structured catalyst supports are mainly oxides such as alumina, silica, zirconia, molecular sieves, and the like, and carbonaceous supports have various advantages over oxide supports. For example, the carbon material has the advantages of developed pore structure, excellent mechanical strength, high thermal stability, acid and alkali corrosion resistance and the like. More importantly, the carbonaceous carrier is not afraid of sulfur poisoning, has good adaptability to raw gas, can be applied to reforming systems such as shale gas, oilfield associated gas, coke oven gas, gasified gas and the like, and does not need to carry out pre-desulfurization treatment on the gas. However, the existing carbon nano material composite catalyst with a shell-core structure has the problems that the catalyst forming technology is complex, and the requirements of catalyst particle size, strength and the like based on a reaction device such as a fixed bed or a fluidized bed at a higher reaction temperature are difficult to meet.
CN103816913a discloses a catalyst which uses active carbon as carrier and cobalt, zirconium and molybdenum polymetallic substances as active components, the active carbon accounts for 80-89%, and the cobalt, zirconium and molybdenum polymetallic active substances account for 11-20%. The invention firstly takes corncob and lignite as raw materials, prepares the mixed active carbon through potassium carbonate activation, then adopts an ultrasonic impregnation method to load multi-metal active components, and has the advantages of uniform active component distribution and carbon deposit resistance. However, due to the weak interaction between the active component and the activated carbon support, sintering of the active metal at high temperatures is difficult to avoid.
The Chinese patent application with publication number of CN103566936A discloses a method for preparing a synthesis gas carbon-based catalyst by reforming methane and carbon dioxide, the catalyst also belongs to a carbon-based supported metal catalyst, a carrier of the catalyst is obtained by a series of treatments of lignite, the specific treatment process is that the lignite is carbonized at 600-800 ℃ to obtain lignite semicoke, and the lignite semicoke is activated for 3-5 hours under the action of supercritical water to prepare lignite activated carbon; the lignite active carbon and ammonia water are mixed, soaked in a closed way and placed in a closed pressurized temperature-controlled reaction kettle, and the hydrothermal reaction is carried out under the conditions that the reaction temperature is 800-1200 ℃ and the reaction pressure is 1-6 MPa. The catalyst is prepared by immersing ammonia water modified lignite activated carbon in a cobalt nitrate solution by high-pressure (3-5 MPa) ultrasonic waves, drying and roasting. The preparation process of the catalyst is complex, and particularly, the modification condition of the carrier needs high temperature and high pressure and is very harsh, thus being not beneficial to popularization and application. In addition, the catalyst also has to be loaded with metal Co to react at 950 ℃ so as to have good catalytic activity.
Chinese patent application publication No. CN104984769B discloses a method for preparing a carbon-based catalyst for synthesis gas by reforming methane with carbon dioxide, which comprises mixing a direct coal liquefaction residue with a composite modifier according to a ratio of 1: mixing and grinding uniformly according to the mass ratio of (1-3); the composite modifier comprises 90-98% of alkali and 2-10% of nitrate by mass fraction; heating the mixture which is uniformly ground in an inert atmosphere for carbonization treatment; then cooling the carbonized mixture, and washing to neutrality; the mixture washed to neutrality is dried to obtain the carbon-based catalyst. Since the carbon-based catalyst does not contain a metal active component, the stability of continuous reaction is not high, and the catalyst formation is difficult.
It can thus be seen that the catalysts prepared as described above are either difficult to shape or the reaction conditions employed are severe, making the methane carbon dioxide reforming process lacking a suitable catalyst.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a shell-core structure catalyst for preparing synthesis gas by reforming methane and carbon dioxide, a preparation method and application thereof, wherein the CH is realized by mainly utilizing a special limited space of a shell-core structure and regulating and controlling the structure and the composition of the catalyst 4 -CO 2 The reforming reaction efficiency is improved, and the problems that active components of the nickel-based catalyst are easy to sinter, carbon is easy to accumulate, and a carbon carrier is difficult to form are solved.
In order to achieve the purpose, the invention is realized by adopting the following technical scheme:
the preparation method of the shell-core catalyst for preparing the synthesis gas by reforming the methane and the carbon dioxide comprises the following steps:
step 1, attaching metal nickel and metal oxide on the surface of hydrophilic silicon dioxide nanospheres by an atomic deposition method or an immersion method to obtain Ni-M x O y /SiO 2 A bimetallic composite;
step 2, dissolving hydrophilic silica nanospheres in toluene, adding triethylamine and methyltrimethoxysilane, condensing, refluxing and centrifuging, and drying a centrifuged product to obtain amphiphilic silica nanosphere particles;
step 3, ni-M x O y /SiO 2 Dissolving the bimetal composite material and a carbon source in water to obtain an aqueous phase solution; dissolving amphiphilic silica nanosphere particles in an emulsion oil phase to obtain an oil phase solution; mixing the aqueous phase solution and the oil phase solution, stirring to obtain a Pickering solution with the oil phase in water phase, and carrying out hydrothermal reaction on the Pickering solution to obtain the metal Ni and M encapsulated x O y Polymer spheres of (2); the polymer ball is of a multi-core shell structure, the multi-core shell structure is formed by wrapping a plurality of small balls in a big ball, and metal Ni and M are packaged in each small ball x O y ；
Step 4, encapsulating the metal Ni and M x O y Drying the polymer spheres, etching, and calcining the etched product to obtain Ni-M x O y A catalyst @ C; ni-M x O y The big spheres and the small spheres in the catalyst at the temperature of C are both porous carbon with a hollow structure.
The invention further improves that:
preferably, in step 1, ni-M is prepared by atomic deposition or immersion x O y /SiO 2 In the process of the bimetal composite material, ni is prepared from nickel metal salt, and metal oxide is prepared from corresponding metal salt.
Preferably, the emulsion oil phase in step 3 is a mixture of any one or more of benzene, toluene, hexane or octane.
Preferably, the carbon source in step 3 is a biomass carbon source.
Preferably, in the step 2, the mass ratio of the hydrophilic silica nanospheres to the toluene solution is 1:5; the molar ratio of the hydrophilic silica nanospheres to the triethylamine to the methyltrimethoxysilane is 5:1:1.
Preferably, in step 3, ni-M x O y /SiO 2 The mass ratio of the bimetal composite material to the oil phase to the carbon source is 1:20:9.
a shell-core structure catalyst for preparing synthesis gas by reforming methane and carbon dioxide is of a multi-core shell structure, wherein the multi-core shell structure is formed by wrapping a plurality of pellets in a large sphere, and each pellet is encapsulated with metal Ni and M x O y The big ball and the small ball are porous hollow carbon balls.
Preferably, the mass percent of carbon in the multi-core shell structure is 75-94 wt%, the mass percent of metal Ni is 5-15wt%, and M x O y The mass percentage of (2) is 1-10wt%.
Preferably, the catalyst has a bond index G RI Up to 95, strength SI 4 25 >95%, thermal stability TS +6 >95％。
The application of the shell-core structure catalyst for preparing the synthesis gas by reforming methane and carbon dioxide is used for catalyzing methane and carbon dioxide to prepare the synthesis gas.
Compared with the prior art, the invention has the following beneficial effects:
the invention discloses a preparation method of a shell-core structure catalyst for preparing synthesis gas by reforming methane and carbon dioxide, and belongs to the technical field of catalyst preparation for preparing synthesis gas by reforming methane and carbon dioxide. The method of the invention adopts an atomic layer deposition method or an immersion method to load metal on the surface of nano-sized silicon oxide, prepares the carbonaceous catalyst with a core-shell structure through a Pickering emulsion template method, and finally prepares a finished product through simple processes of filtering, washing, drying, etching and roasting, wherein the finally prepared catalyst consists of nickel, auxiliary metal and carbon. The invention adopts nickel, carbon and other raw materials, has wide sources and low cost. The method has the advantages of simple process, simple equipment and low production cost; the prepared product has high catalytic activity and high conversion rate of methane and carbon dioxide; good carbon deposit resistance and stability, etc. The catalyst can be widely used as a catalyst for preparing synthesis gas by reforming methane and carbon dioxide.
Preparing a metal/silicon oxide composite material with high dispersion and hydrophilicity on the surface of a hydrophilic silicon dioxide template with rich silicon hydroxyl groups by an impregnation method or an atomic layer deposition method, constructing a micron-sized carbon spherical shell layer by taking an oil-water interface of Pickering emulsion as a template, and guiding and assembling the composite material as a hard template into an internal nanometer-sized polymer spherical structure; forming big ball-packed small ball, and encapsulating metal Ni and M in the small ball x O y The components of the big ball and the small ball are polymers; after the hydrothermal reaction is finished, preparing micro/nano hollow carbon spheres which encapsulate metal and have a multi-hollow core structure (yolk-shell-shell) by etching and high-temperature calcination, namely, corresponding catalysts; the catalyst can be subjected to synchronous carbothermic reduction in the calcining process, the polymer is carbonized to form carbon, and the encapsulated active metal carbonaceous shell-core structure composite metal catalyst obtained by the preparation method has high thermal stability and high sintering resistance, and has high catalytic activity, selectivity and carbon deposit resistance in methane carbon dioxide reforming catalytic reaction.
The invention also discloses a catalyst with a shell-core structure for preparing the synthesis gas by reforming the methane and the carbon dioxide, the catalyst has a core-shell structure as a whole, and is formed by wrapping small balls in the big balls, and metal Ni particles and M are packaged in the small balls x O y The structure of the particles, and the big spheres and the small spheres are porous carbon spheres. The structure encapsulates nickel in a core-shell structure, and the core-shell structure is a limited space, so that the nickel can be limited, and sintering and coking formation aggregation of active metal nano particles in a high-temperature reaction in a later application catalysis process can be inhibited. If carbon deposition occurs on the surface of the nickel particles, oxygen provided by the metal oxide can react with the carbon on the surface of the nickel particles, and the generated gas is discharged from the pore canal of the shell, so that carbon deposition on the surface of the nickel particles is avoided. The size of the large sphere is in the micron or sub-millimeter level, and the size of the small sphere is in the nanometer or sub-micron level, so that the catalyst can play a catalytic role in the subsequent application process in a certain size.
Furthermore, the whole catalyst is in a sphere structure, and the sphere structure has a regular geometric structure and low flow resistance, so that the catalytic effect is ensured.
The invention also discloses application of the shell-core structure catalyst for preparing the synthesis gas by reforming the methane and the carbon dioxide, and the catalyst has the following advantages in the application process:
1. methane and CO 2 The conversion rate of (2) is high. The catalyst prepared by the invention is subjected to online reaction detection on a catalyst online evaluation device, and CH is detected 4 /CO 2 The volume ratio is 1, the reaction temperature is 700 ℃, the pressure is normal, and the gas space velocity is 2500h -1 The conversion rate of methane is up to 95%, and the conversion rate of carbon dioxide is up to 94%.
2. The carbon deposit resistance and stability are good. The catalyst prepared by the invention has no obvious reduction of catalytic activity after 120 hours of reaction.
3. Wide raw material source and low cost. The invention adopts Ni, carbon and other non-noble metal raw materials, has wide sources and greatly reduces the cost;
4. the preparation process is simple and the production quantity is large. The required catalyst carbon carrier can be rapidly prepared by silica through a Pickering emulsion method, and the process is simple;
5. the equipment is simple and the investment is small. The method only uses simple common instruments such as a constant-temperature water bath, a drying oven, a tube furnace and the like, and if the method is applied to industrial production, only needs simple constant-temperature water bath and heating equipment, has small investment and is convenient to popularize and use.
The invention can be widely used as a catalyst for preparing the synthesis gas by reforming methane and carbon dioxide, and the adopted preparation method breaks the mode of the traditional preparation method.
Drawings
Fig. 1 is a schematic flow chart of a preparation method of a methane carbon dioxide reforming encapsulated active metal carbonaceous core-shell structure composite metal catalyst according to an embodiment of the application.
Fig. 2 is a schematic structural diagram of a methane carbon dioxide reforming encapsulated active metal carbonaceous core-shell structure composite metal catalyst according to an embodiment of the present application.
Fig. 3 is a Scanning Electron Microscope (SEM) image of the catalyst.
Detailed Description
The invention is described in further detail below with reference to the attached drawing figures and to specific examples:
the invention provides a methane carbon dioxide reforming catalyst which is prepared by taking a carbon material as a carrier to load active metal; the catalyst has a shell-core structure, the carbon sphere material accounts for 75-94 wt% of the catalyst, the nickel active component accounts for 5-15wt% of the catalyst, and the active auxiliary agent metal component accounts for 1-10 wt%.
The methane carbon dioxide reforming catalyst is a micro/nano hollow carbon sphere internally encapsulated with metal and provided with a porous hollow core structure (yolk-shell-shell), namely the catalyst is a micro/nano hollow carbon sphere as shown in figure 2, the internal structure is a large sphere internally wrapped with small spheres, the large sphere and the small sphere are both porous hollow carbon spheres, and the inside of the small sphere is provided with nano nickel particles and M which are compounded together x O y Particles; m is magnesium, calcium, cerium or lanthanum.
The carbon microsphere is an internal micrometer or nanometer-sized carbon microsphere material assembled by taking a hydrophilic silicon oxide composite material as a hard template through a Pickering emulsion method.
Further, the catalyst has a bond index G RI Up to 95, strength SI 4 25 >95%, thermal stability TS +6 >95％。
As shown in fig. 1, one of the embodiments of the present invention discloses a preparation method of a methane carbon dioxide reforming catalyst, which comprises the following steps:
s101, loading Ni and additive metal M on the surfaces of hydrophilic silicon oxide nanospheres with different sizes by an atomic layer deposition method or an immersion method to prepare Ni-M x O y /SiO 2 Bimetallic composite, wherein M x O y Is an oxide formed of an additive metal. When the catalyst is prepared by adopting an impregnation method, a nickel source and an auxiliary metal salt are co-dissolved in an aqueous solution, silicon dioxide is added, and the two metals are attached to the surface of the commercial silicon dioxide in an isovolumetric impregnation mode. When the catalyst is prepared by adopting an atomic layer deposition method, the nickel-metal organic complex of the dicyclopentadienyl and the auxiliary agent is deposited on the surface of silicon dioxide, thus preparing Ni-M x O y /SiO 2 A bimetallic composite.
The nickel source and silica ratio ultimately results in a catalyst with Ni loading of between 5 and 15 wt%.
The nickel source is nickel metal salt, and specifically is any one or a mixture of a plurality of nickel chloride, nickel acetylacetonate, nickel oxalate, nickel dichloride, nickel nitrate or nickel acetate.
Wherein, the mass ratio of the nickel source to the auxiliary metal salt is 15:1-1:2.
wherein the auxiliary metal salt is any one or more of magnesium nitrate, calcium nitrate, cerium chloride or metal organic coordination compounds such as Ce (thd) 4 and La (acac) 3.
Wherein, the silicon dioxide material is commercial hydrophilic spherical silicon dioxide with the size of 20-500 nm.
Preferably, ni-M x O y /SiO 2 The bimetal composite material is prepared by an atomic layer deposition method, is prepared by the atomic layer deposition method, and can adjust the composite morphology and distance of two metals on the surface of silicon dioxide by process control.
S102, hydrophilic silicon oxide nanospheres with specific sizes are selected, the hydrophilic silicon oxide nanospheres are dissolved in toluene solution, and the mass ratio of the hydrophilic silicon oxide nanospheres to the toluene solution is 1:5; adding a proper amount of triethylamine and methyltrimethoxysilane as cross-linking agents, condensing and refluxing, centrifuging, and drying to obtain amphiphilic silica nanosphere particles, namely the hydrophilic and lipophilic silica particles are generated.
In the process, after the surface of a material is subjected to hydrophobic modification, amphiphilic silicon dioxide is dispersed in an emulsion oil phase, the hydrophilic silicon dioxide is subjected to modification operation by using a cross-linking agent, hydrophobic methyl is grafted on the hydrophilic silicon dioxide, so that the water contact angle of the hydrophilic silicon dioxide is between 90 and 120 ℃, the modified amphiphilic silicon dioxide can be used as solid active particles for stabilizing an oil-water interface, and can be used as interface active particles, so that the pickering emulsion is stabilized when the pickering emulsion is prepared in the next step.
Further, the amounts of triethylamine and methyltrimethoxysilane used are determined according to the hydrophilic silica content of the modification operation as needed. For example: 5mol of hydrophilic silica requires the addition of 1mol of triethylamine, 1mol of methyltrimethoxysilane, which is proportionally increased.
S103, taking the emulsion oil phase as a solvent of the oil phase, and adding the amphiphilic silicon dioxide nanosphere particles prepared in the step S102 into the solvent; will dissolve Ni-M x O y/ SiO 2 Taking the composite material and the aqueous solution of the carbon source as water phases; mixing the oil phase and the water phase, and mechanically stirring to obtain the pickering emulsion of the oil phase and the water phase, namely the pickering solution of the water-in-oil type. Placing Pickering emulsion in a hydro-thermal reaction kettle with tetrafluoroethylene lining, and standing at 100deg.C for 24 hr to obtain metal Ni and M encapsulated x O y Micro/nano-sized polymer spheres of the polynuclear shell structure, where micro/nano-sized stands for micro-sized or nano-sized. The most productThe final collection was performed by washing with water and ethanol. Ni-M x O y/ SiO 2 Composite material: an oil phase: carbon source = 1:20:9.
further, pickering emulsions are composed of an aqueous phase and an oil phase, where the emulsion oil phase is the oil phase, and only after mixing with water does pickering emulsion form. The amphiphilic silicon dioxide modified in the step is an amphiphilic silicon dioxide material because of grafting a hydrophobic group methyl, and the material has interfacial activity, can be dispersed at the oil-water interface of the Pickering emulsion, and plays a role in stabilizing the oil-water interface of the Pickering emulsion. The formed Pickering emulsion has the characteristic of good stability, and an oil-water interface is used as a template to construct a micron-sized carbon sphere shell layer. Composite hard template material (i.e., ni-M) x O y /SiO 2 ) Can be used as a hard template for growing microsphere inner nanospheres, guiding and assembling inner nano-sized carbon sphere shells to finally generate regular shell-core structures, and preparing packaging metals (Ni and M) x O y ) And has a micro/nano-sized carbon sphere with a multi-core shell structure.
Composite hard template material (i.e. Ni-M x O y /SiO 2 ) As a template for growing the internal nanospheres, firstly, a carbon source can be polymerized and grown on the surface of the template, and the thickness of a shell layer of the carbon sphere on the surface of the template gradually becomes larger along with the progress of polymerization, and core-shell structures with different shell layer thicknesses can be obtained through a control process.
The oil-water interface of Pickering emulsion can be used as a template for growing microsphere shell layers, and a water-soluble carbon source is polymerized in water and continuously migrates to the oil-water interface to reach the interface for further polymerization to obtain the microsphere shell layers.
Further, the carbon source is a mixture of biomass carbon sources such as glucose, fructose, maltose, sucrose and the like, and any one or more of melamine and urea.
Further, the Pickering emulsion is stable, and the emulsion is water-in-oil sphere, ni-M x O y/ SiO 2 The composite material and the carbon source are polymerized and grown in water. Because the oil-water interface of the Pickering emulsion is stableAnd the oil-water phase cannot flow, so that a stable limited-domain water phase spherical space is formed. So that the carbon spherical shell layer can be constructed after the water phase substance grows at the oil-water interface. In the process, the carbon source is polymerized and grown in the water phase, and Ni-M is added in the growth process x O y /SiO 2 The composite material is wrapped inside.
Further, 10wt% ni supported catalyst preparation: 1mol carbon source+0.6. 0.6gNi-M x O y /SiO 2 Composite material
Through the step, a large ball-coated small ball is formed, a core-shell structure of nickel particles and metal oxides is arranged in the small ball, the shell of the core-shell structure is a high-molecular polymer, and the substance of the polymer is determined by the substance of a carbon source. For example, if the carbon source is glucose, the high molecular polymer is a glucose-based polymer, and if the carbon source is fructose, the fructose-based polymer.
S104, encapsulating the metals Ni and M x O y And the polymer spheres with the micro/nano size and the polynuclear shell structure are subjected to drying, calcining and carbonizing treatment. The method comprises the following specific steps: drying the encapsulated metal polymer spheres prepared in the step S103 for 12-24 hours at the temperature of 100 ℃, etching the dried product by sodium hydroxide, drying, placing the dried product in a tube furnace for calcining and carbonizing treatment, introducing inert gas in the calcining process, and calcining and carbonizing treatment at a proper temperature to prepare the nickel-based catalyst Ni-M of the invention x O y Catalyst @ C.
Further, drying at 100℃for 12-24 hours is to dry the above-mentioned hydrothermal synthesized product, since the product is collected by washing with water and ethanol, and drying moisture is required.
Further, nitrogen and argon are introduced in the calcining process, and the calcining temperature is between 500 and 900 ℃. The S103 product needs to be carbonized at high temperature.
One of the embodiments of the invention discloses an application of a methane carbon dioxide reforming nickel-based catalyst in preparing synthesis gas, which takes methane and carbon dioxide as raw materials to prepare the synthesis gas under the catalysis of the methane carbon dioxide reforming nickel-based catalyst.
Wherein the reaction temperature of methane and carbon dioxide is 550-850 ℃, which is the setting and screening of the reaction temperature gradient. The catalyst with the multi-core shell structure in the invention. Firstly, the hollow internal structure is favorable for the diffusion mass transfer of gas reactant molecules; secondly, the microstructure of the confinement region is conducive to the enrichment of reactants, and the concentration of local reactants can be increased; both of these points can improve the efficiency of the catalyst. Finally, due to the existence of the metal oxide auxiliary agent around Ni, the problem of carbon deposition of the catalyst can be effectively inhibited.
Further description will be provided below in connection with specific examples.
Example 1
The catalyst for preparing the synthesis gas by reforming methane and carbon dioxide comprises the following components in percentage by mass:
nickel (Ni) 9.8%
Cerium oxide (CeO) 2 ) 5.3％
Carbon (C) 84.9%
The preparation method of the catalyst for preparing the synthesis gas by reforming methane and carbon dioxide comprises the following specific steps: step S101, selecting a 20nm commercial hydrophilic spherical silicon dioxide template, and loading metal Ni and CeO on the surface of silicon oxide by adopting an impregnation method 2 Preparing Ni-CeO 2 /SiO 2 A bimetallic composite; the method comprises the steps of preparing 20mL of aqueous solution (containing 8.6g of nickel nitrate and 2.8g of cerium nitrate) from the precursor salt by adopting an isovolumetric impregnation method, using nickel nitrate as a precursor of nickel and cerium nitrate as a precursor of cerium oxide, directly impregnating 10g of hydrophilic silicon dioxide into the aqueous solution, drying at 120 ℃ for 12h, and roasting in air at 550 ℃ for 4h.
Step S102, commercial hydrophilic spherical silica with the wavelength of 60nm is selected for surface hydrophobic modification. Dispersing 3g of hydrophilic silicon oxide nanospheres in 16mL of toluene solution for 20min by ultrasonic treatment, adding 0.9138g of triethylamine and 1.2273g of methyltrimethoxysilane as a cross-linking agent, condensing and refluxing for 4h at 120 ℃, selecting 12000r/min for centrifugation for 5min, drying for 12h at 110 ℃, and using the solution to stabilize Pickering emulsion;
step S103, 0.4g of hydrophilic silica composite (Ni-CeO) 2 /SiO 2 ) 3.68g glucose was dissolved in 5mL water and stirred at 60℃until completely dissolved. 0.4g of hydrophobic SiO 2 Nanospheres were dispersed in 10mL toluene solution with ultrasound for 20 min. Mixing the above solutions, placing in a homogenizing emulsifier, and stirring at 12000r/min for 3min to obtain water-in-oil Pickering emulsion. Placing the emulsion in a tetrafluoroethylene lined high pressure reactor, standing at 100deg.C for 24 hr to obtain encapsulated metals (Ni and CeO) 2 ) And has a multi-core structure.
Step S104, drying the encapsulated metal polymer spheres prepared in the step S103 at 100 ℃ for 24 hours, etching the dried product by 50mL of 0.1M sodium hydroxide for 3 hours, drying, placing the dried product in a tube furnace, heating from 20 ℃ to 350 ℃ at 2 ℃/min under a nitrogen atmosphere of 0.1MPa, maintaining at 350 ℃ for 2 hours, heating from 350 ℃ to 600 ℃ at 2 ℃/min, and maintaining at 600 ℃ for 3 hours for carbonization treatment. The Ni-CeO catalyst of the invention can be prepared after carbonization treatment 2 Catalyst @ C.
FIG. 3 is an SEM characterization of a catalyst having 9.8wt% Ni, 5.3wt% CeO, and 84.9wt% carbon, as in example 1, and having a micron-sized shell-core structure carbon microsphere with Ni-M inside the spherical shell x O y The hollow pellets with the composite structure as the core are stacked.
Example 2:
the catalyst for preparing the synthesis gas by reforming methane and carbon dioxide comprises the following components in percentage by mass:
nickel (Ni) 8%
Cerium oxide (CeO) 2 ) 3％
Carbon (C) 89%
The preparation method of the catalyst for preparing the synthesis gas by reforming methane and carbon dioxide comprises the following specific steps:
step S101, selecting a 40nm commercial hydrophilic spherical silicon dioxide template, and loading metal Ni and CeO on the surface of silicon oxide by adopting an impregnation method 2 Preparing Ni-CeO 2 /SiO 2 A bimetallic composite; the nickel nitrate is used as nickel by an isovolumetric impregnation methodThe precursor salt is prepared into 20mL of aqueous solution (containing 7g of nickel nitrate and 1.2g of cerium chloride), 10g of hydrophilic silicon dioxide is directly immersed into the aqueous solution, dried for 12h at 120 ℃, and baked for 4h at 550 ℃ in the air.
Step S102, selecting 80nm commercial hydrophilic spherical silicon dioxide to carry out surface hydrophobic modification, taking 3g hydrophilic silicon oxide nanospheres to carry out ultrasonic 20min to disperse in 16mL toluene solution, adding 0.9138g triethylamine and 1.2273g methyltrimethoxysilane as cross-linking agents, condensing and refluxing for 4h at 120 ℃, selecting 12000r/min for centrifugation for 5min, drying for 12h at 110 ℃, and taking the hydrophilic silicon oxide nanospheres as interface active particles to stabilize Pickering emulsion;
step S103, 0.4g of hydrophilic silica composite (Ni-CeO) 2 /SiO 2 ) 4.6g glucose was dissolved in 5mL water and stirred at 60℃until completely dissolved. 0.4g of hydrophobic SiO 2 Nanospheres were dispersed in 10mL toluene solution with ultrasound for 20 min. Mixing the above solutions, placing in a homogenizing emulsifier, and stirring at 12000r/min for 3min to obtain water-in-oil Pickering emulsion. Placing the emulsion in a tetrafluoroethylene lined high pressure reactor, standing at 100deg.C for 24 hr to obtain encapsulated metals (Ni and CeO) 2 ) And has a multi-core structure.
Step S104, drying the encapsulated metal polymer spheres prepared in the step S103 at 100 ℃ for 24 hours, etching the dried product by 50mL of 0.1M sodium hydroxide for 3 hours, drying, placing the dried product in a tube furnace, heating from 20 ℃ to 350 ℃ at 2 ℃/min under a nitrogen atmosphere of 0.1MPa, maintaining at 350 ℃ for 2 hours, heating from 350 ℃ to 600 ℃ at 2 ℃/min, and maintaining at 600 ℃ for 3 hours for carbonization treatment. The Ni-CeO catalyst of the invention can be prepared after carbonization treatment 2 Catalyst @ C.
Example 3:
the catalyst for preparing the synthesis gas by reforming methane and carbon dioxide comprises the following components in percentage by mass:
nickel (Ni) 15%
Cerium oxide (CeO) 2 ) 10％
Carbon (C) 75%
The preparation method of the catalyst for preparing the synthesis gas by reforming methane and carbon dioxide comprises the following specific steps:
step S101, selecting a 80nm commercial hydrophilic spherical silicon dioxide template, and loading metal Ni and CeO on the surface of silicon oxide by adopting an impregnation method 2 Preparing Ni-CeO 2 /SiO 2 A bimetallic composite; the method comprises the steps of preparing 20mL of aqueous solution (containing 13g of nickel nitrate and 4g of cerium nitrate) from the precursor salt by adopting an isovolumetric impregnation method, using nickel nitrate as a precursor of nickel and cerium chloride as a precursor of cerium oxide, directly impregnating 10g of hydrophilic silicon dioxide into the aqueous solution, drying at 120 ℃ for 12 hours, and roasting in air at 550 ℃ for 4 hours.
Step S102, selecting 80nm commercial hydrophilic spherical silicon dioxide to carry out surface hydrophobic modification, taking 3g hydrophilic silicon oxide nanospheres to carry out ultrasonic 20min to disperse in 16mL toluene solution, adding 1.8138g triethylamine and 1.9273g methyltrimethoxysilane as cross-linking agents, condensing and refluxing for 4h at 120 ℃, selecting 12000r/min for centrifugation for 5min, drying for 12h at 110 ℃, and taking the hydrophilic silicon oxide nanospheres as interface active particles to stabilize Pickering emulsion;
step S103, 0.4g of hydrophilic silica composite (Ni-CeO) 2 /SiO 2 ) 7.6g glucose was dissolved in 5mL water and stirred at 60℃until completely dissolved. 0.4g of hydrophobic SiO 2 Nanospheres were dispersed in 10mL toluene solution with ultrasound for 20 min. Mixing the above solutions, placing in a homogenizing emulsifier, and stirring at 12000r/min for 3min to obtain water-in-oil Pickering emulsion. Placing the emulsion in a tetrafluoroethylene lined high pressure reactor, standing at 100deg.C for 24 hr to obtain encapsulated metals (Ni and CeO) 2 ) And has a multi-core structure.
Step S104, drying the encapsulated metal polymer spheres prepared in the step S103 at 100 ℃ for 24 hours, etching the dried product by 50mL of 0.1M sodium hydroxide for 3 hours, drying, placing the dried product in a tube furnace, heating from 20 ℃ to 350 ℃ at 2 ℃/min under a nitrogen atmosphere of 0.1MPa, maintaining at 350 ℃ for 2 hours, heating from 350 ℃ to 600 ℃ at 2 ℃/min, and cooling to the temperature of 600 ℃ at the temperature of 350 DEG CAnd maintaining the temperature at 600 ℃ for 3 hours to carry out carbonization treatment. The Ni-CeO catalyst of the invention can be prepared after carbonization treatment 2 Catalyst @ C.
Example 4:
the catalyst for preparing the synthesis gas by reforming methane and carbon dioxide comprises the following components in percentage by mass:
nickel (Ni) 5%
Cerium oxide (CeO) 2 ) 1％
Carbon (C) 94%
The preparation method of the catalyst for preparing the synthesis gas by reforming methane and carbon dioxide comprises the following specific steps:
step S101, selecting a 200nm commercial hydrophilic spherical silicon dioxide template, and loading metal Ni and CeO on the surface of silicon oxide by adopting an Atomic Layer Deposition (ALD) technology 2 Preparing Ni-CeO 2 /SiO 2 A bimetallic composite; using commercial heat type atomic layer deposition equipment, using nickel-base as nickel precursor, ce (thd) 4 as cerium oxide precursor, deposition temperature being 200deg.C, depositing Ni-CeO 2 The preparation method adopts an ALD (atomic layer deposition) circulation method, the pulse time of the nickel precursor is 40 circulation, the helium gas cleaning time is 120s, and finally the auxiliary metal precursor is deposited on the surface of the carrier for 10 circulation.
Step S102, selecting 100nm commercial hydrophilic spherical silicon dioxide to carry out surface hydrophobic modification, taking 3g hydrophilic silicon oxide nanospheres to carry out ultrasonic 20min to disperse in 16mL toluene solution, adding 0.7218g triethylamine and 1.3728g methyltrimethoxysilane as cross-linking agents, condensing and refluxing for 4h at 120 ℃, selecting 12000r/min for centrifugation for 5min, drying for 12h at 110 ℃, and taking the hydrophilic silicon oxide nanospheres as interface active particles to stabilize Pickering emulsion;
step S103, 0.4g of hydrophilic silica composite (Ni-CeO) 2 /SiO 2 ) 2.26g of glucose was dissolved in 5mL of water and stirred at 60℃until completely dissolved. 0.4g of hydrophobic SiO 2 Nanospheres were dispersed in 10mL toluene solution with ultrasound for 20 min. Mixing the above solutions, placing in a homogenizing emulsifier, and stirring at 12000r/min for 3min to obtain water-in-oil Pickering emulsion.Placing the emulsion in a tetrafluoroethylene lined high pressure reactor, standing at 100deg.C for 24 hr to obtain encapsulated metals (Ni and CeO) 2 ) And has a multi-core structure.
Step S104, drying the encapsulated metal polymer spheres prepared in the step S103 at 100 ℃ for 24 hours, etching the dried product by 50mL of 0.1M sodium hydroxide for 3 hours, drying, placing the dried product in a tube furnace, heating from 20 ℃ to 350 ℃ at 2 ℃/min under a nitrogen atmosphere of 0.1MPa, maintaining at 350 ℃ for 2 hours, heating from 350 ℃ to 600 ℃ at 2 ℃/min, and maintaining at 600 ℃ for 3 hours for carbonization treatment. The Ni-CeO catalyst of the invention can be prepared after carbonization treatment 2 Catalyst @ C.
Example 5:
in this embodiment, the catalyst comprises the following components in percentage by mass:
nickel (Ni) 15
Magnesium oxide (MgO) 2.5
Carbon (C) 82.5
Step S101, selecting a 20nm commercial hydrophilic spherical silicon dioxide template, and loading metal Ni and MgO on the surface of silicon oxide by adopting an impregnation method to prepare Ni-MgO/SiO 2 A bimetallic composite; the method comprises the steps of preparing 20mL of aqueous solution (containing 10g of nickel oxalate and 2.47g of magnesium nitrate) from precursor salt of nickel oxalate serving as a precursor of nickel and magnesium nitrate serving as a precursor of Mg by adopting an isovolumetric impregnation method, directly impregnating 10g of hydrophilic silicon dioxide into the aqueous solution, drying at 120 ℃ for 12 hours, and roasting in air at 550 ℃ for 4 hours.
Step S102, commercial hydrophilic spherical silica with the wavelength of 60nm is selected for surface hydrophobic modification. Dispersing 3g of hydrophilic silicon oxide nanospheres in 16mL of toluene solution for 20min by ultrasonic treatment, adding 0.9138g of triethylamine and 1.2273g of methyltrimethoxysilane as a cross-linking agent, condensing and refluxing for 4h at 120 ℃, selecting 12000r/min for centrifugation for 5min, drying for 12h at 110 ℃, and using the solution to stabilize Pickering emulsion;
step S103, 0.4g of hydrophilic silica composite (Ni-MgO/SiO) 2 ) 2.4g fructose was dissolved in 5mL water at 60 ℃Stirred until completely dissolved. 0.4g of hydrophobic SiO 2 Nanospheres were dispersed in 10mL toluene solution with ultrasound for 20 min. Mixing the above solutions, placing in a homogenizing emulsifier, and stirring at 12000r/min for 3min to obtain water-in-oil Pickering emulsion. The emulsion is placed in a tetrafluoroethylene-lined high-pressure reaction kettle and placed at 100 ℃ for 24 hours, and micron-sized polymer spheres which encapsulate metals (Ni and MgO) and have a polynuclear structure are obtained.
Step S104, drying the encapsulated metal polymer spheres prepared in the step S103 at 100 ℃ for 24 hours, etching the dried product by 50mL of 0.1M sodium hydroxide for 3 hours, drying, placing the dried product in a tube furnace, heating from 20 ℃ to 350 ℃ at 2 ℃/min under a nitrogen atmosphere of 0.1MPa, maintaining at 350 ℃ for 2 hours, heating from 350 ℃ to 600 ℃ at 2 ℃/min, and maintaining at 600 ℃ for 3 hours for carbonization treatment. The Ni-MgO@C catalyst of the nickel-based catalyst can be prepared after carbonization treatment.
Example 6:
in this embodiment, the catalyst comprises the following components in percentage by mass:
nickel (Ni) 10
Calcium oxide (CaO) 5
Carbon (C) 85
S101, selecting a 20nm commercial hydrophilic spherical silicon dioxide template, and loading metal Ni and CaO on the surface of silicon oxide by adopting an impregnation method to prepare Ni-CaO/SiO 2 A bimetallic composite; the method comprises the steps of preparing 20mL of aqueous solution (containing 6.67g of nickel oxalate and 2.38g of calcium nitrate) from precursor salt of nickel oxalate serving as a reaction precursor of nickel and calcium nitrate serving as a precursor of Ca by adopting an isovolumetric impregnation method, directly impregnating 10g of hydrophilic silicon dioxide into the aqueous solution, drying at 120 ℃ for 12h, and roasting in air at 550 ℃ for 4h.
Step S102, commercial hydrophilic spherical silica with the wavelength of 60nm is selected for surface hydrophobic modification. Dispersing 3g of hydrophilic silicon oxide nanospheres in 16mL of toluene solution for 20min by ultrasonic treatment, adding 0.9138g of triethylamine and 1.2273g of methyltrimethoxysilane as a cross-linking agent, condensing and refluxing for 4h at 120 ℃, selecting 12000r/min for centrifugation for 5min, drying for 12h at 110 ℃, and using the solution to stabilize Pickering emulsion;
step S103, taking 0.4g of hydrophilic silica composite (Ni-CaO/SiO) 2 ) 2.32g of sucrose was dissolved in 5mL of water and stirred at 60℃until completely dissolved. 0.4g of hydrophobic SiO 2 Nanospheres were dispersed in 10mL toluene solution with ultrasound for 20 min. Mixing the above solutions, placing in a homogenizing emulsifier, and stirring at 12000r/min for 3min to obtain water-in-oil Pickering emulsion. The emulsion is placed in a tetrafluoroethylene-lined high-pressure reaction kettle and placed at 100 ℃ for 24 hours to obtain micron-sized polymer spheres which encapsulate metals (Ni and CaO) and have a polynuclear structure.
Step S104, drying the encapsulated metal polymer spheres prepared in the step S103 at 100 ℃ for 24 hours, etching the dried product by 50mL of 0.1M sodium hydroxide for 3 hours, drying, placing the dried product in a tube furnace, heating from 20 ℃ to 350 ℃ at 2 ℃/min under a nitrogen atmosphere of 0.1MPa, maintaining at 350 ℃ for 2 hours, heating from 350 ℃ to 600 ℃ at 2 ℃/min, and maintaining at 600 ℃ for 3 hours for carbonization treatment. The Ni-CaO@C catalyst of the nickel-based catalyst can be prepared after carbonization treatment.
Example 7:
in this embodiment, the catalyst comprises the following components in percentage by mass:
nickel (Ni) 5
Lanthanum oxide (La) 2 O 3 ) 2
Carbon (C) 93
Step S101, selecting a 20nm commercial hydrophilic spherical silicon dioxide template, and loading metal Ni and La on the surface of silicon oxide by adopting an Atomic Layer Deposition (ALD) technology 2 O 3 Preparing Ni-La 2 O 3 /SiO 2 A bimetallic composite; using commercial thermal atomic layer deposition equipment, using nickel-dicyanoxide as a precursor of nickel, la (acac) 3 As a precursor of lanthanum oxide, ni-La is deposited at a deposition temperature of 200 DEG C 2 O 3 The preparation method adopts an ALD (atomic layer deposition) super-circulation method, the pulse time of the nickel precursor is 40 circulations, the helium cleaning time is 120s, and finally the auxiliary metal precursor is carriedThe bulk surface was deposited for 15 cycles.
Step S102, commercial hydrophilic spherical silica with the wavelength of 60nm is selected for surface hydrophobic modification. Dispersing 3g of hydrophilic silicon oxide nanospheres in 16mL of toluene solution for 20min by ultrasonic treatment, adding 0.9138g of triethylamine and 1.2273g of methyltrimethoxysilane as a cross-linking agent, condensing and refluxing for 4h at 120 ℃, selecting 12000r/min for centrifugation for 5min, drying for 12h at 110 ℃, and using the solution to stabilize Pickering emulsion;
step S103, 0.4g of hydrophilic silica composite (Ni-La 2 O 3 /SiO 2 ) 3.24g of fructose was dissolved in 5mL of water and stirred at 60℃until completely dissolved. 0.4g of hydrophobic SiO 2 Nanospheres were dispersed in 10mL toluene solution with ultrasound for 20 min. Mixing the above solutions, placing in a homogenizing emulsifier, and stirring at 12000r/min for 3min to obtain water-in-oil Pickering emulsion. The emulsion is placed in a tetrafluoroethylene-lined high-pressure reaction kettle and placed at 100 ℃ for 24 hours to obtain micron-sized polymer spheres with multi-core structures and encapsulating metals (Ni and MnO).
Step S104, drying the encapsulated metal polymer spheres prepared in the step S103 at 100 ℃ for 24 hours, etching the dried product by 50mL of 0.1M sodium hydroxide for 3 hours, drying, placing the dried product in a tube furnace, heating from 20 ℃ to 350 ℃ at 2 ℃/min under a nitrogen atmosphere of 0.1MPa, maintaining at 350 ℃ for 2 hours, heating from 350 ℃ to 600 ℃ at 2 ℃/min, and maintaining at 600 ℃ for 3 hours for carbonization treatment. The nickel-based catalyst Ni-La of the invention can be prepared after carbonization treatment 2 O 3 Catalyst @ C.
TABLE 1 catalyst Activity at different component levels
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention.

Claims (10)

1. The preparation method of the shell-core catalyst for preparing the synthesis gas by reforming methane and carbon dioxide is characterized by comprising the following steps of:
step 1, attaching metal nickel and metal oxide on the surface of hydrophilic silicon dioxide nanospheres by an atomic deposition method or an immersion method to obtain Ni-M x O y /SiO 2 A bimetallic composite; m is M x O y M in (2) is magnesium, calcium, cerium or lanthanum;
step 2, dissolving hydrophilic silica nanospheres in toluene, adding triethylamine and methyltrimethoxysilane, condensing, refluxing and centrifuging, and drying a centrifuged product to obtain amphiphilic silica nanosphere particles;
step 3, ni-M x O y /SiO 2 Dissolving the bimetal composite material and a carbon source in water to obtain an aqueous phase solution; dissolving amphiphilic silica nanosphere particles in an emulsion oil phase to obtain an oil phase solution; mixing the aqueous phase solution and the oil phase solution, stirring to obtain a Pickering solution with the oil phase in water phase, and carrying out hydrothermal reaction on the Pickering solution to obtain the metal Ni and M encapsulated x O y Polymer spheres of (2); the polymer ball is of a multi-core shell structure, the multi-core shell structure is formed by wrapping a plurality of small balls in a big ball, and metal Ni and M are packaged in each small ball x O y ；
Step 4, encapsulating the metal Ni and M x O y Drying the polymer spheres, etching, and calcining the etched product to obtain Ni-M x O y A catalyst @ C; ni-M x O y The big spheres and the small spheres in the catalyst at the temperature of C are both porous carbon with a hollow structure.
2. The method for preparing a shell-core catalyst for preparing synthesis gas by reforming methane and carbon dioxide according to claim 1, wherein in step 1, ni-M is prepared by an atomic deposition method or an impregnation method x O y /SiO 2 In the process of the bimetal composite material, ni is prepared from nickel metal salt, and metal oxide is prepared from corresponding metal salt.
3. The method for preparing a shell-core catalyst for reforming methane and carbon dioxide to prepare synthesis gas according to claim 1, wherein the emulsion oil phase in the step 3 is any one or more of benzene, toluene, hexane or octane.
4. The method for preparing a shell-core catalyst for reforming methane and carbon dioxide to prepare synthesis gas according to claim 1, wherein the carbon source in step 3 is a biomass carbon source.
5. The method for preparing a shell-core catalyst for preparing synthesis gas by reforming methane and carbon dioxide according to claim 1, wherein in the step 2, the mass ratio of hydrophilic silica nanospheres to toluene solution is 1:5; the molar ratio of the hydrophilic silica nanospheres to the triethylamine to the methyltrimethoxysilane is 5:1:1.
6. The method for preparing a shell-core catalyst for reforming methane and carbon dioxide to prepare synthesis gas according to claim 1, wherein in step 3, ni-M x O y /SiO 2 The mass ratio of the bimetal composite material to the oil phase to the carbon source is 1:20:9.
7. a shell-core structure catalyst for preparing synthesis gas by reforming methane and carbon dioxide is characterized by having a multi-core shell structure, wherein the multi-core shell structure is formed by wrapping a plurality of pellets in a large pellet, and each pellet is encapsulated with metal Ni and M x O y The big ball and the small ball are porous hollow carbon balls.
8. The catalyst of claim 7, wherein the catalyst comprises a multi-core shell structure in mass percent75-94 wt% of carbon, 5-15wt% of metal Ni and M x O y The mass percentage of (2) is 1-10wt%.
9. The catalyst of claim 7, wherein the catalyst has a bond index G RI Up to 95, strength SI 4 25 >95%, thermal stability TS +6 >95％。
10. Use of a shell-and-core catalyst according to claim 7 for the carbon dioxide reforming of methane to produce synthesis gas.
CN202311039607.6A 2023-06-25 2023-08-17 Shell-core structure catalyst for preparing synthesis gas by reforming methane and carbon dioxide, and preparation method and application thereof Pending CN117299137A (en)

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