CN113750991B

CN113750991B - Catalyst of carbon-coated nickel oxide, preparation method and application thereof

Info

Publication number: CN113750991B
Application number: CN202110077407.4A
Authority: CN
Inventors: 于鹏; 徐国标; 荣峻峰; 谢婧新; 宗明生; 吴耿煌; 林伟国; 纪洪波
Original assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Current assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Priority date: 2020-06-05
Filing date: 2021-01-20
Publication date: 2023-07-14
Anticipated expiration: 2041-01-20
Also published as: CN113750991A

Abstract

Providing a carbon-coated nickel oxide catalyst, and a preparation method and application thereof, wherein the preparation method comprises the steps of providing a carbon-coated nickel nanocomposite as raw powder, adding a binder into the raw powder, and mixing to obtain wet dough; drying the wet dough and then performing first roasting treatment in an inert atmosphere; preparing a second metal salt solution, uniformly mixing the product after the first roasting treatment with the second metal salt solution, and stirring to obtain a solid-liquid mixture; drying the solid-liquid mixture and then carrying out shaping treatment; performing second roasting treatment on the molded product in air to obtain a catalyst of carbon-coated nickel oxide; the second metal salt solution is selected from alkali metal salt solutions and/or alkaline earth metal salt solutions. The nano composite material is used as raw powder, the second metal oxide is used as an auxiliary agent to prepare a catalyst, and the catalyst is processed by a specific process, so that the specific surface, the pore volume and the pore diameter of the catalyst can be adjusted, the catalyst has higher catalytic activity and mechanical strength, and has better effect on the catalytic decomposition of nitrous oxide.

Description

Catalyst of carbon-coated nickel oxide, preparation method and application thereof

Technical Field

The invention relates to the field of catalysts, in particular to a carbon-coated nickel oxide catalyst, and a preparation method and application thereof.

Background

The transition metal oxide has excellent catalytic performance and photoelectromagnetic performance, and is a research hot spot in the field of inorganic materials. The carbon material has good conductivity, good chemical/electrochemical stability and high structural strength. The carbon material is used for coating the nano particles of the active metal or the metal oxide, so that the conductivity and the stability of the nano material can be effectively improved, and the nano particles are not easy to agglomerate due to the limited domain effect of the nano particles. In recent years, the carbon-coated metal nano material not only has wide application in the fields of electrocatalysis, super capacitor materials, lithium ion battery anode materials, bioengineering and the like, but also has good application prospect in the field of catalytic science, and particularly has excellent catalytic activity in oxidation, reduction, cracking and other reactions.

Generally, the carbon-coated nanomaterial is small in particle size, powdery, and poor in self-moldability. However, in industrial applications, particularly in the case of fixed bed processes, not only are certain activities and selectivities required for the catalysts, but also certain properties such as particle size and mechanical strength are required. If the catalyst is not strong enough and disintegrated and pulverized, the catalyst is easy to carry loss or block the device in the reaction process, the pressure drop of the catalyst bed is greatly increased, and even the device is forced to stop. Therefore, the carbon-coated nano material needs to be subjected to forming treatment to meet the industrial reaction requirements of pressure drop, compressive strength, stability and the like after filling. The molding process is a process of forming solid particles having a certain size, shape, specific surface area, pore volume and mechanical strength by mutually aggregating raw materials such as a catalyst raw powder and a molding aid by an external force. The forming process can have influence on the activity, strength and other performances of the catalyst to a certain extent. For example, the mechanical strength of the catalyst tends to be increased with a decrease in the specific surface area and pore volume, whereas the mechanical strength tends to be decreased with an increase in the specific surface area and pore volume. In industrial production, the surface area and the pore volume of the catalyst are improved as much as possible under the premise that the mechanical strength and the pressure drop of the catalyst allow, the adsorption, desorption, inner diffusion, outer diffusion and the like of reactants and products are facilitated, and the catalytic action of active components of the catalyst is facilitated. How to solve the balance among the specific surface area, the pore volume, the strength and other properties, and not affecting the activity as much as possible while improving the strength is the research focus of the carbon-coated nano material forming method.

N ₂ O is an important greenhouse gas, and its Global Warming Potential (GWP) is CO ₂ 310 times of CH ₄ 21 times of (2); in addition, N ₂ The average life of O in the atmosphere is about 150 years, also known as NO in the stratosphere _x The main source of the composition is not only capable of seriously destroying the ozone layer, but also has strong greenhouse effect.

The domestic adipic acid production mainly adopts a cyclohexanol nitric acid oxidation method, and the cyclohexanol is subjected to nitric acid oxidation to produce adipic acid, the technology of the method is mature, the product yield and purity are relatively high, but the nitric acid consumption is large, and a large amount of N is produced in the reaction process ₂ O, and the tail gas discharged in the production process is concentrated, the wave quantity is large, and the concentration is high (36% -40%). At present, 15 ten thousand tons of adipic acid and N are produced annually by adopting a cyclohexanol nitric acid oxidation method ₂ O (O)The annual discharge amount can reach 4.5 ten thousand tons. Therefore, the tail gas of the adipic acid purifying device can effectively control and eliminate N ₂ O has become a research hotspot in the field of environmental catalysis today.

The direct catalytic decomposition method can decompose N ₂ O is decomposed into nitrogen and oxygen to eliminate N ₂ O is the most effective and clean technique. Wherein, the catalyst is the technical core of the direct catalytic decomposition method. Decomposition N reported in the current study ₂ The catalyst of O mainly comprises a noble metal catalyst, an ion-exchange molecular sieve catalyst and a transition metal oxide catalyst. Noble metal catalysts (e.g., rh and Ru) on N ₂ The O catalytic decomposition has higher low-temperature catalytic activity (the temperature is 250-350 ℃ and N can be efficiently decomposed) ₂ O), the expensive price limits the large-scale use of noble metal catalysts. Molecular sieve-type catalysts and transition metal oxide catalysts are significantly less expensive than noble metals, but currently these two types of catalysts are relatively more expensive than noble metals for N ₂ The activity of O catalytic decomposition is low, and the high-efficiency decomposition temperature is 450-550 ℃. Thus, new materials catalyst pair N was developed that are new non-noble metals, low cost and efficient ₂ The emission reduction of O has important significance.

It is noted that the information disclosed in the foregoing background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.

Disclosure of Invention

The invention aims to overcome at least one defect of the prior art, and provides a catalyst of carbon-coated nickel oxide doped with alkali metal and/or alkaline earth metal, a preparation method and application thereof, which uses nano composite material of carbon-coated nickel as raw powder, adopts a specific process to process the raw powder, can adjust the specific surface, pore volume and pore diameter of the catalyst to obtain the catalyst of carbon-coated nickel oxide with unique structure and composition, has better effect on catalyzing and decomposing nitrous oxide, and is helpful for solving the problem of high concentration N generated in the production process of adipic acid factories, nitric acid factories and the like ₂ The elimination of O waste gas is a great environmental protection and reductionThe air pollution has important significance and has good industrial application prospect.

In order to achieve the above purpose, the present invention adopts the following technical scheme:

the invention provides a preparation method of a catalyst of carbon-coated nickel oxide, which comprises the following steps: providing a carbon-coated nickel nanocomposite as raw powder, adding a binder into the raw powder, and mixing to obtain a wet dough; drying the wet dough and then performing first roasting treatment in an inert atmosphere; preparing a second metal salt solution, uniformly mixing the product after the first roasting treatment with the second metal salt solution, and stirring to obtain a solid-liquid mixture; drying the solid-liquid mixture and then carrying out shaping treatment; performing second roasting treatment on the molded product in air to obtain a catalyst of carbon-coated nickel oxide; wherein the second metal salt solution is selected from alkali metal salt solutions and/or alkaline earth metal salt solutions.

According to one embodiment of the present invention, the carbon-coated transition metal nanocomposite has a pickling loss of not more than 60%, may not more than 40%, may not more than 30%, may not more than 20%, and may not more than 10%.

According to an embodiment of the present invention, the molding process further includes: and carrying out one or more times of third roasting treatment on the dried solid-liquid mixture in air so as to regulate and control the pore morphology of the catalyst.

According to one embodiment of the invention, the third roasting treatment comprises heating the product after the first roasting treatment to 300-400 ℃ at a heating rate of 1-20 ℃ per minute and keeping the temperature constant for 0.5-10 hours.

According to one embodiment of the present invention, the first firing process includes: heating the dried wet dough to 400-800 ℃ at a heating rate of 1-20 ℃/min, and keeping the constant temperature for 1-10 h; the second firing treatment includes: heating the product after the molding treatment to 300-400 ℃ at a heating rate of 1-20 ℃/min, and keeping the temperature for 4-10 h.

According to one embodiment of the invention, the binder is an aluminum sol, a silica sol or a silica-alumina sol.

According to one embodiment of the invention, the binder is prepared from pseudo-boehmite and a peptizing agent, wherein the peptizing agent is selected from one or more of aqueous nitric acid, aqueous hydrochloric acid and aqueous citric acid, and the mass of the peptizing agent is 1% -5%, preferably 2% -3% of the mass of the pseudo-boehmite.

According to one embodiment of the invention, the binder further comprises a lubricant, namely the binder is prepared from pseudo-boehmite, a peptizing agent and a lubricant, wherein the lubricant is selected from one or more of sesbania powder, citric acid, starch and carboxymethyl cellulose, and the mass of the lubricant is 1-6% of the mass of the raw powder.

According to one embodiment of the invention, the liquid-solid mass ratio in the wet dough is 0.8-1.5, and the raw powder accounts for 20% -80% of the solid mass in the wet dough; the mass of the lubricant is 1-6% of the mass of the raw powder.

According to one embodiment of the invention, the second metal salt solution is selected from one or more of an organic acid salt solution of an alkali metal and/or an alkaline earth metal, a carbonate solution, a basic carbonate solution, a nitrate solution and a sulfate solution.

According to one embodiment of the invention, the wet dough is dried at a temperature of 20 ℃ to 100 ℃ for a drying time of 3 hours to 24 hours, and the drying atmosphere is an inert atmosphere or an air atmosphere.

According to one embodiment of the invention, the shaping treatment is selected from one or more of extrusion, rolling, tabletting and granulation.

According to one embodiment of the invention, the carbon-coated nickel nanocomposite comprises a core-shell structure having a shell layer and an inner core, wherein the shell layer is a graphitized carbon layer, the inner core is nickel nanoparticles, the carbon content is 15-60 wt% and the nickel content is 40-85 wt% based on the weight of the carbon-coated nickel nanocomposite.

The invention also provides a catalyst of the carbon-coated nickel oxide, which is prepared by the method.

According to one embodiment of the invention, the catalyst comprises a carrier and an active component loaded on the carrier, wherein the active component is a carbon-coated nickel oxide nanocomposite, the nanocomposite comprises a nuclear membrane structure with an outer membrane and an inner core, the outer membrane is a graphitized carbon membrane, the inner core comprises nickel oxide nanoparticles, the nanocomposite further comprises a second metal, the second metal is an alkali metal and/or an alkaline earth metal, and the molar ratio of the second metal to the nickel is 0.01-0.3.

According to one embodiment of the invention, the nickel oxide content is 40% to 90%, the support content is 10% to 60%, and the carbon content is not more than 2%, preferably 0.1% to 1%, based on the weight of the catalyst.

The specific surface area of the catalyst according to one embodiment of the invention is 90m ² /g～180m ² Per gram, pore volume of 0.14cm ³ /g～0.24cm ³ And/g, the crushing strength is 80N/cm-160N/cm.

The invention also provides a method for catalyzing the decomposition of nitrous oxide, which comprises the step of adopting the catalyst to contact with nitrous oxide for catalyzing the decomposition reaction to generate nitrogen and oxygen.

According to one embodiment of the invention, in the catalytic decomposition reaction, the reaction temperature is 300-420 ℃, the reaction space velocity is 500-3000 ml of reaction gas/(hour g of catalyst), and the volume concentration of nitrous oxide is 30-40%.

According to the technical scheme, the beneficial effects of the invention are as follows:

according to the preparation method of the carbon-coated nickel oxide catalyst, the nano composite material of the carbon-coated nickel is used as raw powder, and the specific surface, the pore diameter, the pore volume and the strength of the catalyst can be adjusted by adopting a specific roasting and forming process for processing the raw powder. In general, different catalytic reactions have different requirements on adsorption, desorption, mass transfer and diffusion due to different reaction conditions, and the specific surface, pore diameter and pore volume of the catalyst are regulated to be beneficial to improving the catalytic performance. The preparation method of the invention is adopted to obtain the catalyst of the carbon-coated nickel oxide with unique structure and composition, and the catalyst is doped with a second metal, namely alkali metal and/or alkaline earth metal, which catalyzes N ₂ The O decomposition reaction may be characterized by further improvement in catalytic activity. Must be compared with the existing catalystN in industrial waste gas ₂ O is diluted and then treated, the catalyst can directly catalyze and decompose high-concentration nitrous oxide waste gas generated in industrial production at a lower temperature, the decomposition rate can reach more than 99%, and the catalyst has great significance in protecting environment and reducing atmospheric pollution and has good industrial application prospect.

Drawings

The following drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate the invention and together with the description serve to explain the invention, without limitation to the invention.

FIG. 1 is a flow chart of a process for preparing a catalyst of carbon-coated nickel oxide according to one embodiment of the present invention;

FIG. 2 is an X-ray diffraction chart of the product obtained in the step (2) of example 1;

FIG. 3 is a transmission electron micrograph of the product obtained in step (2) of example 1;

FIG. 4 is an X-ray diffraction chart of the product obtained in the step (2) of example 2;

FIG. 5 is a transmission electron micrograph of the product obtained in step (2) of example 2;

FIG. 6 is an X-ray diffraction pattern of the nanocomposite of comparative example 1;

FIG. 7 is a transmission electron microscope image of the nanocomposite of comparative example 1;

FIG. 8 is a Raman spectrum of the nanocomposite of comparative example 1;

FIG. 9 is an X-ray diffraction pattern of the nanocomposite of comparative example 2;

FIG. 10 is a transmission electron microscope image of the nanocomposite of comparative example 2;

FIG. 11 is a Raman spectrum of the nanocomposite of comparative example 2.

Detailed Description

The following provides various embodiments or examples to enable those skilled in the art to practice the invention as described herein. These are, of course, merely examples and are not intended to limit the invention from that described. The endpoints of the ranges and any values disclosed in the present invention are not limited to the precise range or value, and the range or value should be understood to include values close to the range or value. For a range of wave values, one or more new ranges of wave values may be obtained in combination with each other between the endpoints of each range, between the endpoints of each range and the individual point values, and between the individual point values, and these ranges of wave values should be considered as specifically disclosed herein.

The term "nuclear membrane structure" in the present invention refers to a nuclear membrane structure having an outer membrane, which is a graphitized carbon membrane, and an inner core comprising nickel oxide nanoparticles. The composite material formed by coating the graphitized carbon film with the nickel oxide nano particles is spherical or spheroidic.

The term "graphitized carbon film" refers to a thin film structure composed mainly of graphitized carbon.

The term "graphitized carbon layer" refers to a carbon structure in which a layered structure is clearly observed under a high resolution transmission electron microscope, not an amorphous structure, and the interlayer spacing is about 0.34nm. The composite material formed by coating transition metal nano particles with the graphitized carbon layer is spherical or spheroidic.

The term "carbon element content determined by X-ray photoelectron spectroscopy" refers to the relative content of carbon elements on the surface of a material, which is measured by performing element quantitative analysis by using an X-ray photoelectron spectrometer as an analysis tool.

The term "carbon element content determined in elemental analysis" refers to the relative content of total carbon elements of a material as measured by elemental quantitative analysis using an elemental analyzer as an analysis tool.

The term "pore morphology" refers to the morphology features of pore size, specific surface, volume, wave volume, spacing, shape, etc. of the surface of the catalyst material.

FIG. 1 is a flow chart of a process for preparing a catalyst of carbon-coated nickel oxide according to one embodiment of the present invention. As shown in fig. 1, the invention provides a preparation method of a carbon-coated nickel oxide catalyst, which comprises the following steps: providing a carbon-coated nickel nanocomposite as a raw powder, adding a binder into the raw powder, and mixing to obtain a wet dough; drying the wet dough and then performing first roasting treatment in an inert atmosphere; preparing a second metal salt solution, uniformly mixing the product obtained after the first roasting treatment with the second metal salt solution, and stirring to obtain a solid-liquid mixture; drying the solid-liquid mixture and then carrying out shaping treatment; and performing second roasting treatment on the formed product in air to obtain a catalyst of carbon-coated nickel oxide; wherein the second metal salt solution is selected from alkali metal salt solutions and/or alkaline earth metal salt solutions.

First, a carbon-coated nickel nanocomposite is provided. The carbon-coated nickel nanocomposite can be prepared by the following method:

placing a nickel source and carboxylic acid in a solvent and mixing to form a homogeneous solution; removing the solvent in the homogeneous solution to obtain a precursor; and pyrolyzing the precursor in inert atmosphere or reducing atmosphere to obtain the carbon-coated nickel nanocomposite.

Specifically, the precursor is a water-soluble mixture, which is obtained by dissolving a nickel source and carboxylic acid in a solvent such as water, ethanol, etc. to form a homogeneous solution, and then directly evaporating the solvent to remove the nickel. The aforementioned temperature and process of evaporating the solvent may be any available prior art technique, for example, spray drying at 80-120 ℃, or drying in an oven.

In some embodiments, the nickel source is selected from one or more of a soluble organic acid salt, a basic carbonate, a hydroxide, and an oxide of nickel, the carboxylic acid is selected from one or more of citric acid, maleic acid, trimesic acid, terephthalic acid, gluconic acid, and malic acid, and the mass ratio of the nickel source to the carboxylic acid is 1 (0.1-10). In addition, other organic compounds than the two above may be added together to form a homogeneous solution, and the other organic compounds may be any organic compound that can supplement the carbon source required in the product and that does not contain other doping atoms. Organic compounds which are not volatile, such as organic polyols, lactic acid, etc., are preferred. In some embodiments, the mass ratio of nickel source, carboxylic acid, and other organic compounds is 1:0.1-10:0-10, preferably 1:0.5-5:0-5, more preferably 1:0.8-3:0-3.

In some embodiments, pyrolysis comprises: heating the precursor to a constant temperature section in an inert atmosphere or a reducing atmosphere, and keeping the constant temperature in the constant temperature section; wherein the heating rate is 0.5-30 ℃/min, such as 2.5 ℃/min, 4.5 ℃/min, 5 ℃/min, 6.5 ℃/min, 7 ℃/min, 8.5 ℃/min, 9 ℃/min, 10 ℃/min, 20 ℃/min, etc.; the constant temperature section temperature is 400-800 ℃, preferably 500-700 ℃, such as 500 ℃, 550 ℃, 570 ℃, 610 ℃, 660 ℃, 680 ℃, and the like; the constant temperature is maintained for 20 min-600 min, preferably 30 min-300 min, such as 30min, 45min, 55min, 70min, 86min, 97min, 100min, 180min, 270min, 300min, etc.; the inert atmosphere is nitrogen or argon, the reducing atmosphere is a mixed gas of inert gas and hydrogen, for example, a small amount of hydrogen is doped in the inert atmosphere.

The carbon-coated nickel nanocomposite can be obtained by the method, and comprises a core-shell structure with a shell layer and an inner core, wherein the shell layer is a graphitized carbon layer, the inner core is nickel nano particles, the carbon content is 15-60 wt% and the nickel content is 40-85 wt% based on the weight of the carbon-coated nickel nanocomposite. The particle size of the core-shell structure is 1-100 nm, preferably 2-40 nm. Of course, other methods may be used to prepare the carbon-coated nickel nanocomposite, and the invention is not limited thereto.

In some embodiments, the invention further comprises acid washing the carbon-coated nickel nanocomposite obtained after the pyrolysis described above. The nanocomposite is a nickel-coated graphitized carbon layer nanocomposite. The term "graphitized carbon layer" refers to a carbon structure in which a layered structure is clearly observed under a high resolution transmission electron microscope, not an amorphous structure, and the interlayer spacing is about 0.34nm. The nano composite material with the graphitized carbon layer coated with nickel is a composite material composed of nickel nano particles tightly coated with the graphitized carbon layer (not in contact with the outside), nickel nano particles capable of being in contact with the outside and limited in domain and a carbon material with a mesoporous structure. After pickling treatment, nickel in the composite material has a certain loss, and can be characterized by a pickling loss rate. That is, "pickling loss" refers to the loss ratio of nickel after pickling of the finished carbon-coated nickel nanocomposite product. Reflecting how tightly the graphitized carbon layer coats the nickel. If the graphitized carbon layer does not cover the nickel tightly, the nickel of the inner core is dissolved by the acid after the acid treatment and is lost. The higher the acid washing loss rate, the lower the tightness degree of the graphitized carbon layer on the nickel coating is, and the lower the acid washing loss rate is, the higher the tightness degree of the graphitized carbon layer on the nickel coating is.

In general, specific conditions for the acid washing treatment are: 1g of the sample was added in a proportion of 20mL of an aqueous sulfuric acid solution (1 mol/L), the sample was treated at 90℃for 8 hours, then washed with deionized water to neutrality, dried, weighed, analyzed, and the acid washing loss rate was calculated as follows.

The calculation formula is as follows: the pickling loss rate= [1- (mass wavelet of nickel in the composite after pickling×mass of the composite after pickling)/(mass wavelet of nickel in the composite to be treated×mass of the composite to be treated) ]×100%.

In some embodiments, the composite material generally has a pickling loss of 60% or less, may be 40% or less, may be 30% or less, may be 20% or less, and may be 10% or less.

Then, the obtained carbon-coated nickel nanocomposite is used as raw powder, and a binder is added and mixed to obtain a wet dough.

In some embodiments, the binder is an aluminum sol, a silica sol, or a silica alumina sol.

In some embodiments, the binder further comprises a lubricant including, but not limited to, one or more of sesbania powder, citric acid, starch, and carboxymethyl cellulose.

In some embodiments, the binder is made of pseudo-boehmite and a peptizing agent, and may also include other substances, such as lubricants, to which the present invention is not limited. The peptizing agent includes, but is not limited to, one or more of aqueous nitric acid, aqueous hydrochloric acid, and aqueous citric acid, and the lubricant includes, but is not limited to, one or more of sesbania powder, citric acid, starch, and carboxymethyl cellulose. The mass of the peptizing agent is 1-5% of that of pseudo-boehmite, preferably 2-3%.

In some embodiments, the liquid to solid mass ratio in the wet dough is 0.8 to 1.5, for example 0.8, 0.9, 1, 1.2, etc., preferably 0.85 to 1. The raw powder accounts for 20% -80% of the solid mass in the wet dough, such as 20%, 25%, 31%, 47%, 56%, 60%, 75% and the like. The mass of the lubricant is 1% to 6% of the mass of the raw powder, for example, 1%, 2%, 4%, 5%, 6% and the like, preferably 2% to 3%.

After the wet dough having a desired composition is obtained, the wet dough is dried at a drying temperature of 20 to 100 ℃, for example, 20 ℃, 25 ℃, 30 ℃, 45 ℃, 50 ℃, 65 ℃, 70 ℃, 72 ℃, 82 ℃, 88 ℃, and the like. The drying time is 3h to 24h, for example 3h, 4h, 6h, 7h, 10h, 12h, 13h, 17h, 20h, 24h, etc. The drying atmosphere is an inert atmosphere or an air atmosphere.

Further, the wet dough after drying is subjected to a first roasting treatment. The purpose of this first calcination treatment is to adjust the carbon content before the shaping treatment, because the carbon content in the raw powder is high enough to consume a part of the oxidation. If the carbon content is not regulated before molding, only the primary air after molding is roasted, pore formation under the conditions that the specific surface and the pore diameter are not easy to control can lead to the strength reduction of the molded catalyst, and under the micro-reverse evaluation condition of a laboratory, the strength reduction can not greatly influence the catalyst performance, but the strength reduction can influence the industrial application effect of the catalyst. In contrast, the strength, specific surface area and pore volume of the obtained catalyst are better in comprehensive performance after the carbon content is adjusted by air roasting before forming.

In general, the first calcination treatment is carried out under an inert atmosphere, taking as an example a binder made of pseudo-boehmite, gamma-Al formed after calcination of pseudo-boehmite ₂ O ₃ The carrier has larger specific surface area, higher strength and moderate pore volume, and can be used as the carrier of active components. The temperature rising rate of the first roasting treatment is 1 to 20 ℃ per minute, preferably 2.5 to 10 ℃ per minute, for example 2.5, 3.5, 4, 5, 6, 8, 10, etc. When the temperature is raised to the roasting temperature of 400-800 ℃, keeping the constant temperature for 1-10 h, wherein the preferable roasting temperature is 450-600 ℃, and the constant temperature time is 3-8 h.

Further, the invention also comprises the steps of uniformly mixing the product after the first roasting treatment with the second metal salt solution and stirring for 1-4 hours to obtain a solid-liquid mixture, wherein the second metal salt is doped into the product after the first roasting treatment through impregnation in the process. The solvent of the second metal salt solution is water, and the second metal salt solution is one or more selected from an organic acid salt solution, a carbonate solution, a basic carbonate solution, a nitrate solution and a sulfate solution of alkali metal and/or alkaline earth metal, preferably, a potassium nitrate solution or a potassium carbonate solution.

The obtained solid-liquid mixture is dried at a drying temperature of 20 to 100 ℃, for example, 20 ℃, 25 ℃, 30 ℃, 45 ℃, 50 ℃, 65 ℃, 70 ℃, 72 ℃, 82 ℃, 88 ℃, etc. The drying time is 3h to 24h, for example 3h, 4h, 6h, 7h, 10h, 12h, 13h, 17h, 20h, 24h, etc. The drying atmosphere is an inert atmosphere or an air atmosphere. Then, further, the dried product is subjected to a molding treatment. Wherein the molding treatment method is one or more of extrusion, rolling, tabletting and granulation, and the invention is not limited thereto.

After the molding treatment, the molded product is further subjected to a second baking treatment, in which case the second baking treatment is performed in air. Generally, the temperature rise rate of the second calcination treatment is 1 to 20℃per minute, preferably 2.5 to 10℃per minute, for example, 2.5℃per minute, 3.5℃per minute, 4℃per minute, 5℃per minute, 6℃per minute, 8℃per minute, 10℃per minute, etc. Heating to 300-400 ℃, for example 320 ℃, 350 ℃, 370 ℃ and the like at the temperature rising rate, and keeping the constant temperature for 4-10 hours, for example 4 hours, 5 hours, 7 hours, 8 hours, 9 hours, 10 hours and the like.

It is known to those skilled in the art that carbon generates gas by oxidation reaction after contact with oxygen at high temperature, however, the inventors of the present invention have unexpectedly found that the oxygen-treated material burns out most of the carbon while the nickel of the core is oxidized and a small portion of the carbon remains. As described above, the XPS and Raman spectrum detection analysis prove that the part of carbon is a graphitized carbon film layer coated on the surface of nickel oxide, and the film carbon layer further has a plurality of excellent properties, so that the nanocomposite has great application potential in catalytic materials, energy storage materials and electromagnetic materials.

By utilizing the mechanism, the inventor further discovers that as part of carbon is burned off during the roasting treatment, the amorphous carbon matrix around the core-shell structure can actually act as a pore-forming agent in the mild oxidation process, so that abundant pore structures or cavities can be formed around the graphite carbon coated nickel oxide and the shell structure, which is very beneficial to catalyzing chemical reactions. Moreover, the carbon content in the material can be more precisely controlled by roasting the material one or more times before and after the forming treatment, so that the pore morphology, such as pore size, wave volume, pore spacing, shape and the like, of the obtained catalyst can be regulated and controlled to realize the optimization of the catalyst performance, and the catalyst is suitable for catalyzing various chemical reactions.

Specifically, the invention also comprises a third roasting treatment of one or more times of the dried solid-liquid mixture in air before the forming treatment so as to regulate the pore morphology of the catalyst. The temperature rising rate of the third roasting treatment is 1 to 20 ℃ per minute, preferably 2.5 to 10 ℃ per minute, for example 2.5, 3.5, 4, 5, 6, 8, 10, etc. Heating to 300-400 ℃, such as 310 ℃, 320 ℃, 370 ℃ and the like at the temperature rising rate, and keeping the constant temperature for 0.5-10 h, such as 0.5h, 1h, 1.5h, 2h, 3h, 4h, 5h, 7h, 8h, 9h, 10h and the like.

In summary, the catalyst of the carbon-coated nickel oxide is obtained by the method, and the catalyst comprises a carrier and an active component loaded on the carrier, wherein the active component is a nano composite material of the carbon-coated nickel oxide, the nano composite material comprises a nuclear membrane structure with an outer membrane and an inner core, the outer membrane is a graphitized carbon membrane, the inner core comprises nickel oxide nano particles, the formed catalyst further comprises a second metal, the second metal is an alkali metal and/or alkaline earth metal, the molar ratio of the second metal to the nickel is 0.01-0.3, preferably 0.01-0.2, for example 0.01, 0.05, 0.08, 0.1, 0.13, 0.15, 0.17, 0.18, 0.2 and the like.

In some embodiments, the foregoing catalyst support is alumina. The content of nickel oxide is 40% -90%, for example 40%, 43%, 50%, 55%, 57%, 67%, 79%, 80%, 85% etc., and the content of the carrier is 10% -60%, for example 10%, 16%, 22%, 31%, 35%, 40%, 50%, 60% etc., based on the weight of the catalyst. The carbon content is not more than 2%, preferably 0.1% to 1%, for example 1%, 0.8%, 0.5%, 0.3%, 0.2%, 0.1% etc. of the catalyst.

In some embodiments, the ratio of the carbon element in the catalyst as determined by X-ray photoelectron spectroscopy to the carbon element content as determined by elemental analysis is not less than 10 in terms of mass ratio. As described above, the carbon element content determined by the X-ray photoelectron spectroscopy refers to the relative content of carbon element on the surface of the material measured by performing elemental quantitative analysis using the X-ray photoelectron spectrometer as an analysis tool. The carbon element content determined in the elemental analysis refers to the relative content of the total carbon element of the material measured by elemental quantitative analysis using an elemental analyzer as an analysis tool. When the ratio of the carbon element determined by the X-ray photoelectron spectroscopy to the carbon element content determined by the elemental analysis is larger, it is shown that most of carbon is concentrated on the surface of the material in the whole catalyst, a carbon film layer is formed, and the nuclear film structure is formed.

In some embodiments, the catalyst of the invention is located at 1580cm in the Raman spectrum ^-1 G peak intensity in the vicinity and at 1320cm ^-1 The ratio of nearby D peak intensities is greater than 2. As known to those skilled in the art, the D peak and the G peak are Raman characteristic peaks of C atom crystals, the D peak represents a defect of a carbon atom lattice, and the G peak represents a C atom sp ² Hybrid in-plane stretching vibration. It will be appreciated that a greater ratio of G-peak intensity to D-peak intensity indicates that more graphitic carbon is present in the catalyst than amorphous carbon. That is, the carbon element in the catalyst of the present invention exists mainly in the form of graphitic carbon. The graphite carbon has better oxidation resistance, and can synergistically increase catalytic activity with nickel oxide nano particles of the inner core, thereby improving the performance of the whole catalyst.

In some embodiments, the specific surface area of the foregoing catalyst is 90m ² /g～180m ² Per g, exampleSuch as 100m ² /g、120m ² /g、145m ² /g、159m ² /g、170m ² /g、180m ² /g, etc.; pore volume of 0.14cm ³ /g～0.24cm ³ /g, e.g. 0.14cm ³ /g、0.16cm ³ /g、0.18cm ³ /g、0.20cm ³ /g、0.22cm ³ /g、0.24cm ³ /g; the crushing strength is 80N/cm to 160N/cm, for example 80N/cm, 90N/cm, 100N/cm, 120N/cm, 140N/cm, 160N/cm, etc.

In summary, the invention adopts the nano composite material of the carbon-coated nickel oxide as an active component and loads the active component on the carrier through a specific process, so that the obtained catalyst not only has higher catalytic activity, but also has certain mechanical strength, is not easy to crack and pulverize in the reaction process, can meet the requirements of actual industrial production, and can be reflected as further improvement of catalytic performance after being doped with alkali metal and/or alkaline earth metal, in particular to catalyzing N ₂ The method has good application prospect in the reaction of the acidic oxides such as O and the like.

Specifically, the invention provides a method for catalyzing nitrous oxide decomposition, which comprises the step of carrying out catalytic decomposition reaction by contacting nitrous oxide with the catalyst to generate nitrogen and oxygen.

In some embodiments, the catalytic decomposition reaction is at a temperature of 300 ℃ to 420 ℃, preferably 360 ℃ to 420 ℃. The space velocity of the catalytic decomposition reaction is 500-3000 ml of reaction gas/(hr.g of catalyst). The high reaction space velocity allowed by the invention indicates that the catalyst has high activity and high device processing capacity when the reaction is applied.

According to the invention, as previously described, the decomposition N reported in the current research ₂ The catalyst of O mainly comprises a noble metal catalyst, an ion-exchange molecular sieve catalyst and a transition metal oxide catalyst. Noble metal catalysts, although having a low decomposition temperature, are not suitable for large-scale industrial production at an expensive price; the high-efficiency decomposition temperature of other molecular sieve catalysts and transition metal oxide catalysts is 450-550 ℃, and the high temperature required by the reaction greatly improves the industrial cost.

The inventors of the present invention have found that the nanocomposite material of the carbon-coated nickel oxide of the present invention can effectively decompose nitrous oxide into nitrogen and oxygen as a catalyst, and exhibits excellent stability of catalytic activity in the reaction. In addition, when the existing catalyst is used for catalyzing and decomposing nitrous oxide, the high-concentration nitrous oxide obtained in industrial production is generally required to be diluted to about 0.5% -2%, and the catalyst can be directly decomposed to reach a high decomposition rate without dilution. Namely, the volume concentration of the nitrous oxide is 30% -40%, the catalytic decomposition reaction can be carried out, and the decomposition rate can reach more than 99%, so that the industrial cost is greatly reduced, and the method has good industrial application prospect.

The invention will be further illustrated by the following examples, but the invention is not limited thereby. Unless otherwise indicated, all reagents used in the present invention were analytically pure.

The invention detects the elements on the surface of the material by an X-ray photoelectron spectroscopy (XPS). The X-ray photoelectron spectroscopy analyzer used was an ESCALab220i-XL type radiation electron spectroscopy manufactured by VG scientific company and equipped with Avantage V5.926 software, and the X-ray photoelectron spectroscopy analysis test conditions were: the excitation source is monochromized A1K alpha X-ray with power of 330W and basic vacuum of 3X 10 during analysis and test ^-9 mbar。

Analysis of carbon (C) was performed on a Elementar Micro Cube elemental analyzer, which was used mainly for analysis of four elements, carbon (C), hydrogen (H), oxygen (O), and nitrogen (N), with the following specific methods and conditions: 1 mg-2 mg of sample is weighed in a tin cup, is put into an automatic sample feeding disc, enters a combustion tube through a ball valve for combustion, the combustion temperature is 1000 ℃ (in order to remove atmospheric interference during sample feeding, helium is adopted for blowing), and then reduction copper is used for reducing the burnt gas to form nitrogen, carbon dioxide and water. The mixed gas is separated by three desorption columns and sequentially enters a TCD detector for detection. The analysis of oxygen element is to convert oxygen in the sample into CO by pyrolysis under the action of a carbon catalyst, and then detect the CO by TCD. The raw powder carbon-coated nickel only contains carbon, hydrogen, oxygen and metallic nickel, so the total content of the metal can be known by the content of the carbon, hydrogen and oxygen elements.

The ratio of the different metal oxides in the catalyst is measured by an X-ray fluorescence spectrum analyzer (XRF), and the content of the different metal oxides in the composite material is calculated by the known content of carbon elements. The model of the X-ray fluorescence spectrum analyzer (XRF) adopted by the invention is Rigaku 3013X-ray fluorescence spectrum analyzer, and the X-ray fluorescence spectrum analysis test conditions are as follows: the scan time was 100s and the atmosphere was air.

The Raman detection of the invention adopts a LabRAM HR UV-NIR laser confocal Raman spectrometer manufactured by HORIBA company of Japan, and the laser wavelength is 325nm.

The model of the high-resolution transmission electron microscope (HRTEM) adopted by the invention is JEM-2100 (HRTEM) (Japanese electronics Co., ltd.) and the test conditions of the high-resolution transmission electron microscope are as follows: the acceleration voltage was 200kV.

The model of the XRD diffractometer adopted by the invention is XRD-6000 type X-ray powder diffractometer (Shimadzu), and XRD testing conditions are as follows: cu target, ka radiation (wavelength λ=0.154 nm), tube voltage 40kV, tube current 200mA, scan speed 10 ° (2θ)/min.

The invention detects the pore structure property of the material by a BET test method. Specifically, the specific surface area, the pore volume and the average pore diameter of the catalyst are measured by a Quantachrome AS-6B type analyzer, and the pore diameter is the most probable.

The crushing strength of the invention refers to the pressure of each catalyst when being crushed, the strength is measured by adopting a ZQJ-III intelligent particle strength tester of a large-connection intelligent tester factory, and the catalyst is pressed into tablets under the condition of 2.5MPa, and the diameter of a die is 10mm. The crushing strength test is carried out on 20 samples randomly extracted from the same batch of catalyst, after the maximum value and the minimum value are removed, the arithmetic average value is taken as a Newton value F (N) when single particles are crushed, and the radial crushing strength sigma (N/cm) of the single particles is calculated according to a formula sigma=F/L, wherein L is the length (cm) of the single particles of the catalyst.

Example 1

This example is illustrative of the preparation of the catalyst of the present invention

(1) 10g of nickel carbonate and 10g of citric acid are weighed into a beaker containing 100mL of deionized water, stirred at 70 ℃ to obtain a homogeneous solution, and continuously heated and evaporated to dryness to obtain a solid precursor.

(2) And (3) placing the solid precursor obtained in the step (1) in a porcelain boat, then placing the porcelain boat in a constant temperature area of a tube furnace, introducing nitrogen with the flow of 100mL/min, heating to 600 ℃ at the speed of 4 ℃/min, stopping heating after keeping the temperature for 2 hours, and cooling to room temperature in the nitrogen atmosphere to obtain the carbon-coated nickel nanocomposite. The elemental analysis shows that the mass percentages of the elements contained in the carbon-coated nickel nanocomposite are respectively as follows: 26.14% of carbon, 0.42% of hydrogen, 0.91% of oxygen and 72.53% of nickel.

As can be seen from fig. 2, the nickel in the material is present in a reduced form. Fig. 3 is a TEM image of a nanocomposite of the material, which can be seen to be a carbon-coated nickel nanocomposite, with a graphitized carbon layer coating the outer layer of the nickel nanoparticle, with a core-shell structure.

(3) At room temperature, uniformly mixing pseudo-boehmite with the mass of 50% of the total powder mass and the product obtained in the step (2), adding sesbania powder with the mass of 1.5% of the mass of the raw powder mass, uniformly mixing, preparing nitric acid with the mass of 2.5% of the mass of the pseudo-boehmite into a nitric acid aqueous solution with the mass of 1mol/L, dropwise adding, and continuously stirring until the materials are uniformly mixed to obtain wet dough.

(4) Placing the wet dough in an 80 ℃ oven, drying for 12 hours, then placing in a tube furnace, introducing nitrogen, heating to 550 ℃ at a speed of 5 ℃/min, keeping the temperature for 4 hours, stopping heating, cooling to room temperature under nitrogen atmosphere, and adding K ₂ CO ₃ The aqueous solution, in which the molar ratio of potassium to nickel was 0.01, was stirred for 2 hours, placed in an 80 ℃ oven and dried for 12 hours.

(5) And (3) placing the product obtained in the step (4) in a tube furnace, introducing air, heating to 300 ℃ at a speed of 5 ℃/min, keeping the temperature for 2.0h, stopping heating, and cooling to room temperature under the air atmosphere.

(6) And (3) crushing the product obtained in the step (5), sieving with a 100-mesh sieve, tabletting with powder with the granularity smaller than 100 meshes in a tablet press, putting the tabletting product in a tubular furnace, introducing air, heating to 350 ℃ at the speed of 5 ℃/min, keeping the temperature for 6 hours, stopping heating, and cooling to room temperature under the air atmosphere to obtain the formed catalyst. As is clear from XRF and elemental analysis, the molded catalyst had a carbon content of 0.51 wt%, a potassium oxide content of 0.42 wt%, a nickel oxide content of 53.91 wt% and an alumina content of 45.16 wt%.

The specific surface area, pore volume, pore size and crush strength of the catalyst are shown in Table 1.

Example 2

(1) 10g of nickel acetate and 10g of citric acid are weighed into a beaker containing 100mL of deionized water, stirred at 70 ℃ to obtain a homogeneous solution, and continuously heated and evaporated to dryness to obtain a solid precursor.

(2) And (3) placing the solid precursor obtained in the step (1) in a porcelain boat, then placing the porcelain boat in a constant temperature area of a tube furnace, introducing nitrogen with the flow of 100mL/min, heating to 650 ℃ at the speed of 2 ℃/min, stopping heating after keeping the temperature for 2 hours, and cooling to room temperature in the nitrogen atmosphere to obtain the carbon-coated nickel nanocomposite. Elemental analysis shows that the mass percentages of the elements contained in the carbon-coated nickel nanocomposite are respectively as follows: 24.29% of carbon, 0.47% of hydrogen, 0.96% of oxygen and 74.28% of nickel. As can be seen from fig. 4, the nickel in the material is present in a reduced form. Fig. 5 is a TEM image of a nanocomposite of the material, which can be seen to be a carbon-coated nickel nanocomposite, with a graphitized carbon layer coating the outer layer of the nickel nanoparticle, with a core-shell structure.

(3) Uniformly mixing pseudo-boehmite accounting for 25% of the total powder mass and the product obtained in the step (2) at room temperature, adding sesbania powder accounting for 1.5% of the mass of the raw powder mass, uniformly mixing, preparing nitric acid accounting for 2.5% of the mass of the pseudo-boehmite into 1mol/L nitric acid aqueous solution, dropwise adding, and continuously stirring until the materials are uniformly mixed; wet dough is obtained.

(4) Placing the wet dough in an 80 ℃ oven, drying for 12 hours, then placing in a tube furnace, introducing nitrogen, heating to 550 ℃ at a speed of 5 ℃/min, keeping the temperature for 4 hours, stopping heating, cooling to room temperature under nitrogen atmosphere, addingK ₂ CO ₃ The aqueous solution, in which the molar ratio of potassium to nickel was 0.1, was stirred for 2 hours, placed in an 80 ℃ oven and dried for 12 hours.

(6) And (3) crushing the product obtained in the step (5), sieving with a 100-mesh sieve, tabletting with powder with the granularity smaller than 100 meshes in a tablet press, putting the tabletting product in a tubular furnace, introducing air, heating to 350 ℃ at the speed of 5 ℃/min, keeping the temperature for 6 hours, stopping heating, and cooling to room temperature under the air atmosphere to obtain the formed catalyst. As is clear from XRF and elemental analysis, the molded catalyst had a carbon content of 0.72 wt%, a potassium oxide content of 4.22 wt%, a nickel oxide content of 75.96 wt% and an alumina content of 19.10 wt%.

Example 3

(1) Uniformly mixing pseudo-boehmite accounting for 25% of the total powder mass and the carbon-coated nickel nanocomposite obtained in the step (2) of the embodiment 1 at room temperature, adding sesbania powder accounting for 1.5% of the raw powder mass, uniformly mixing, preparing nitric acid accounting for 2.5% of the pseudo-boehmite mass into 1mol/L nitric acid aqueous solution, dropwise adding, and continuously stirring until the materials are uniformly mixed to obtain wet dough;

(2) Placing the wet dough in an 80 ℃ oven, drying for 12 hours, then placing in a tube furnace, introducing nitrogen, heating to 550 ℃ at a speed of 5 ℃/min, keeping the temperature for 4 hours, stopping heating, cooling to room temperature under nitrogen atmosphere, and adding K ₂ CO ₃ The aqueous solution, in which the molar ratio of potassium to nickel was 0.1, was stirred for 2 hours, placed in an 80 ℃ oven and dried for 12 hours.

(3) Crushing the product obtained in the step (2), sieving with a 100-mesh sieve, tabletting with powder with granularity smaller than 100 meshes in a tablet press, placing the tabletted product in a tube furnace, introducing air, heating to 350 ℃ at a speed of 5 ℃/min, keeping the temperature for 8 hours, stopping heating, and cooling to room temperature under an air atmosphere to obtain the formed catalyst. As is clear from XRF and elemental analysis, the carbon content of the molded catalyst was 0.76 wt%, the potassium oxide content was 4.09 wt%, the nickel oxide content was 76.02 wt%, and the alumina content was 19.13 wt%. The specific surface area, pore volume, pore size and crush strength of the catalyst are shown in Table 1.

Comparative example 1

Placing the carbon-coated nickel nanocomposite obtained in the step (2) in the embodiment 1 in a porcelain boat, placing the porcelain boat in a constant temperature area of a tube furnace, introducing standard gas with the flow rate of 100mL/min (the volume wave of oxygen is 15 percent, and nitrogen is balance gas), heating to 350 ℃ at the speed of 2 ℃/min, keeping the temperature for 8 hours, stopping heating, and cooling to room temperature under the atmosphere of the standard gas to obtain the carbon-coated nickel oxide nanocomposite.

As can be seen from fig. 6, the nickel in the resulting nanocomposite is present as an oxide after the mild oxidation treatment. Fig. 7 is a Transmission Electron Microscope (TEM) image of the nanocomposite of comparative example 1, and it was observed that the material had a carbon layer film on the surface, and the particle size was approximately 5 to 20 nm.

The nanocomposite material had a carbon content of 0.64 wt% and a nickel oxide content of 99.36 wt% as determined by elemental analysis. As is known from X-ray photoelectron spectroscopy (XPS) analysis, carbon, oxygen, and nickel are detected in the surface layer elements of the nanocomposite. Wherein the ratio of the carbon element content of the surface layer to the total carbon element content is 32.7/1. It can be seen that the carbon in the nanocomposite is mainly present at the surface of the nuclear membrane structure. FIG. 8 shows a Raman spectrum of the nanocomposite, wherein the G peak (1580 cm ^-1 ) Intensity of (C) and intensity of D peak (1320 cm) ^-1 ) The ratio of (2) to (1) is 2.2. It can be seen that the carbon in this material is mostly graphitic carbon.

Comparative example 2

Placing the carbon-coated nickel nanocomposite obtained in the step (2) in the example 2 in a porcelain boat, placing the porcelain boat in a constant temperature area of a tube furnace, introducing standard gas with the flow rate of 100mL/min (the volume wave of oxygen is 15 percent, and nitrogen is balance gas), heating to 330 ℃ at the speed of 2 ℃/min, keeping the temperature for 8 hours, stopping heating, and cooling to room temperature under the atmosphere of the standard gas to obtain the carbon-coated nickel oxide nanocomposite.

As can be seen from fig. 9, after the mild oxidation treatment, the nickel in the resulting nanocomposite is present in the form of an oxide. Fig. 10 shows a transmission electron microscope image of the nanocomposite of comparative example 2, and it can be seen that the material surface has a carbon layer film with a particle diameter of about 5 to 20 nm.

The nanocomposite material was found to have a carbon content of 0.91 wt% and a nickel oxide content of 99.09 wt% as determined by X-ray fluorescence spectroscopy (XRF) and elemental analysis. As is known from X-ray photoelectron spectroscopy (XPS) analysis, carbon, oxygen, and nickel are detected in the surface layer elements of the nanocomposite. Wherein the ratio of the carbon element content of the surface layer to the total carbon element content is 22.4/1. It can be seen that the carbon in the nanocomposite is mainly present at the surface of the nuclear membrane structure. FIG. 11 shows a Raman spectrum of the nanocomposite, wherein the G peak (1580 cm ^-1 ) Intensity of (C) and intensity of D peak (1320 cm) ^-1 ) The ratio of (2) to (1) is 2.4. It can be seen that the carbon in this material is mostly graphitic carbon.

Comparative example 3

(1) The wet dough obtained in the step (3) of the example 2 is placed in an oven at 80 ℃ for drying for 12 hours, then placed in a tube furnace, nitrogen is introduced, the temperature is raised to 550 ℃ at a speed of 5 ℃/min, the temperature is kept for 4 hours, the heating is stopped, and the wet dough is cooled to room temperature under the nitrogen atmosphere.

(2) And (3) placing the product obtained in the step (1) in a tube furnace, introducing air, heating to 300 ℃ at a speed of 5 ℃/min, keeping the temperature for 2.0h, stopping heating, and cooling to room temperature under the air atmosphere.

(3) Crushing the product obtained in the step (2), sieving with a 100-mesh sieve, tabletting with powder with granularity smaller than 100 meshes in a tablet press, putting the tabletting product in a tube furnace, introducing air, heating to 350 ℃ at a speed of 5 ℃/min, keeping the temperature for 6 hours, stopping heating, and cooling to room temperature under the air atmosphere to obtain the formed catalyst. As is clear from XRF and elemental analysis, the carbon content of the molded catalyst was 0.79 wt%, the nickel oxide content was 78.31 wt%, and the alumina content was 20.90 wt%. The specific surface area, pore volume, pore size and crush strength of the catalyst are shown in Table 1.

Application example 1

Crushing the tablets, sieving to obtain 0.5 g of catalyst particles of 20-40 meshes, placing the catalyst particles in a continuous flow fixed bed reactor, wherein the composition of reaction gas is 38.0% N ₂ O, nitrogen was used as an equilibrium gas, and the flow rate of the reaction gas was 15ml/min. The activity evaluation temperature is 300-500 ℃ and the N is catalytically decomposed ₂ The conversion of O is shown in Table 2.

Application example 2

Application example 3

Crushing the tablets, sieving to obtain 0.5 g of catalyst particles of example 3 with 20-40 meshes, placing the catalyst particles in a continuous flow fixed bed reactor, and making the composition of reaction gas be 38.0% N ₂ O, nitrogen was used as an equilibrium gas, and the flow rate of the reaction gas was 15ml/min. The activity evaluation temperature is 300-500 ℃ and the N is catalytically decomposed ₂ The conversion of O is shown in Table 2.

Comparative application example 1

0.5 g of the catalyst of comparative example 1 was placed in a continuous flow fixed bed reactor, and the reaction gas composition was 38.0% N ₂ O, nitrogen was used as an equilibrium gas, and the flow rate of the reaction gas was 15ml/min. The activity evaluation temperature is 300-500 ℃ and the N is catalytically decomposed ₂ The conversion of O is shown in Table 2.

Comparative application example 2

0.5 g of the nanocomposite of comparative example 2 was placed as a catalyst in a continuous flow fixed bed reactor with a reaction gas composition of 38.0% N ₂ O, nitrogen was used as an equilibrium gas, and the flow rate of the reaction gas was 15ml/min. The activity evaluation temperature is 300-500 ℃ and the N is catalytically decomposed ₂ The conversion of O is shown in Table 2.

Comparative application example 3

Crushing the tablets, sieving to obtain 0.5 g of catalyst particles of comparative example 3 with 20-40 meshes, placing the catalyst particles in a continuous flow fixed bed reactor, wherein the composition of reaction gas is 38.0% N ₂ O, nitrogen was used as an equilibrium gas, and the flow rate of the reaction gas was 15ml/min. The activity evaluation temperature is 300-500 ℃ and the N is catalytically decomposed ₂ The conversion of O is shown in Table 2.

TABLE 1

TABLE 2

As can be seen from tables 1 and 2 above, the shaped catalyst prepared by the method of the present invention can be adjusted in specific surface, pore volume and pore diameter by calcination in air, the mechanical strength of the obtained shaped catalyst is moderate, and the doping of alkali metal and/or alkaline earth metal further improves N ₂ The O catalytic decomposition performance can meet the requirements of industrial application and can efficiently eliminate N at 360-420 DEG C ₂ O. When the formed catalyst provided by the invention is applied to the waste gas treatment in the adipic acid production process, the reaction temperature can be greatly reduced, the energy consumption is reduced, the activity is high, and the stability is good.

It will be appreciated by persons skilled in the art that the embodiments described herein are merely exemplary and that various other alternatives, modifications and improvements may be made within the scope of the invention. Thus, the present invention is not limited to the above-described embodiments, but only by the claims.

Claims

1. The preparation method of the carbon-coated nickel oxide catalyst is characterized by comprising the following steps:

providing a carbon-coated nickel nanocomposite as a raw powder, adding a binder into the raw powder, and mixing to obtain a wet dough;

drying the wet dough and then performing first roasting treatment in an inert atmosphere;

preparing a second metal salt solution, uniformly mixing the product obtained after the first roasting treatment with the second metal salt solution, and stirring to obtain a solid-liquid mixture;

drying the solid-liquid mixture and then carrying out shaping treatment; a kind of electronic device with high-pressure air-conditioning system

Performing second roasting treatment on the molded product in air to obtain a catalyst of carbon-coated nickel oxide;

wherein the second metal salt solution is selected from alkali metal salt solutions and/or alkaline earth metal salt solutions;

the catalyst comprises a carrier, an active component and an auxiliary agent, wherein the active component and the auxiliary agent are loaded on the carrier, the active component is a carbon-coated nickel oxide nanocomposite, the nanocomposite comprises a nuclear membrane structure with an outer membrane and an inner core, the outer membrane is a graphitized carbon membrane, the inner core comprises nickel oxide nano particles, the auxiliary agent comprises a second metal oxide, the second metal oxide is an oxide of alkali metal and/or alkaline earth metal, and the molar ratio of the second metal to the nickel is 0.01-0.3;

Based on the weight of the catalyst, the content of the nickel oxide is 40% -90%, the content of the carrier is 10% -60%, the carbon content is 0.1% -1%, and the sum of the contents of all components in the catalyst is 100%;

the ratio of the carbon element determined by the X-ray photoelectron spectroscopy to the carbon element content determined by elemental analysis in the catalyst is not less than 10 in terms of mass ratio;

the Raman spectrum of the catalyst is positioned at 1580cm ^-1 G peak intensity in the vicinity and at 1320cm ^-1 The ratio of nearby D peak intensities is greater than 2;

the carrier is alumina.

2. The method according to claim 1, wherein the molding process further comprises: and carrying out one or more times of third roasting treatment on the dried solid-liquid mixture in air so as to regulate and control the pore morphology of the catalyst.

3. The production method according to claim 2, wherein the third baking treatment comprises heating the product after the first baking treatment to 200 ℃ to 500 ℃ at a heating rate of 1 ℃/min to 20 ℃/min, and keeping the temperature constant for 0.5h to 10h.

4. The method of manufacturing according to claim 1, wherein the first firing treatment includes: heating the dried wet dough to 400-800 ℃ at a heating rate of 1-20 ℃/min, and keeping the temperature constant for 1-10 h; the second firing treatment includes: and heating the product after the molding treatment to 200-500 ℃ at a heating rate of 1-20 ℃/min, and keeping the temperature for 4-10 hours.

5. The method of claim 1, wherein the binder is an aluminum sol, a silica sol, or a silica alumina sol.

6. The preparation method of claim 1, wherein the binder is prepared from pseudo-boehmite and a peptizing agent, and the mass of the peptizing agent is 1% -5% of the mass of the pseudo-boehmite; the peptizing agent is selected from one or more of aqueous nitric acid, aqueous hydrochloric acid and aqueous citric acid.

7. The preparation method according to claim 6, wherein the mass of the peptizing agent is 2% -3% of the mass of the pseudo-boehmite.

8. The preparation method according to claim 6, wherein the binder further comprises a lubricant, the lubricant is selected from one or more of sesbania powder, citric acid, starch and carboxymethyl cellulose, and the mass of the lubricant is 1% -6% of the mass of the raw powder.

9. The preparation method of claim 1, wherein the mass ratio of liquid to solid in the wet dough is 0.8-1.5, and the raw powder accounts for 20% -80% of the mass of solid in the wet dough.

10. The method of claim 1, wherein the second metal salt solution is selected from one or more of the alkali metal and/or alkaline earth metal organic acid salt solutions, carbonate solutions, basic carbonate solutions, nitrate solutions, and sulfate solutions.

11. The preparation method according to claim 1, wherein the wet dough is dried at 20 ℃ to 100 ℃ for 3h to 24h in an inert atmosphere or an air atmosphere.

12. The method of claim 1, wherein the shaping process is selected from one or more of extrusion, rolling, tabletting, and granulation.

13. The method of claim 1, wherein the carbon-coated nickel nanocomposite comprises a core-shell structure having a shell layer and an inner core, the shell layer is a graphitized carbon layer, the inner core is nickel nanoparticles, the carbon content is 15wt% to 60wt% and the nickel content is 40wt% to 85wt% based on the weight of the carbon-coated nickel nanocomposite.

14. A carbon-coated nickel oxide catalyst prepared by the method of any one of claims 1-13.

15. A method of catalyzing the decomposition of nitrous oxide comprising contacting nitrous oxide with the catalyst of claim 14 to produce nitrogen and oxygen.

16. The method according to claim 15, wherein in the catalytic decomposition reaction, the reaction temperature is 300-420 ℃, the reaction space velocity is 500-3000 ml of reaction gas/(hour.g of catalyst), and the volume concentration of the nitrous oxide is 30-40%.