Preparation method and application of nitrogen-doped activated carbon for ruthenium catalyst carrier

Abstract

The invention provides a preparation method and application of nitrogen-doped activated carbon for a ruthenium catalyst carrier, and the preparation method comprises the following steps: carrying out in-situ polymerization on aniline on the surface of nanocellulose by adopting an oxidative polymerization method to generate polyaniline, so as to obtain polyaniline-coated nanocellulose; the preparation method comprises the following steps: reacting phenol, an aminophenol derivative and a formaldehyde solution serving as raw materials under the action of a base catalyst to obtain modified A-stage phenolic resin; and uniformly mixing the polyaniline-coated nano cellulose with the modified resol, curing, crushing, carbonizing, activating, graphitizing, grinding and sieving to obtain the nitrogen-doped carrier activated carbon. The nanocellulose contains carbon, hydrogen and oxygen elements, gas can be generated in the preparation process of the activated carbon, and the pore structure of the activated carbon is expanded along with gas escape; a nitrogen-doped activated carbon pore wall is generated in situ by polyaniline around the occupation space of the nanocellulose, and the nitrogen element is beneficial to adjusting the size of active metal ruthenium particles and improving the activity and stability of the ammonia synthesis supported ruthenium catalyst prepared from the nitrogen-doped activated carbon pore wall.

Description

Technical Field

[0001] The present invention belongs to the technical field of ruthenium-based catalyst activated carbon carriers, and particularly relates to a preparation method and application of nitrogen-doped activated carbon for ruthenium-based catalyst carriers. Background Art

[0002] The ammonia synthesis industry is a large-tonnage, high-energy-consuming and low-yield industry. Today, with the increasingly tense energy situation, the classic high-energy-consuming Haber-Bosch ammonia synthesis with iron as the catalyst has shown its huge deficiencies. In 1971, researchers developed a supported ruthenium-based catalyst with activated carbon as the carrier and alkali metal potassium as the promoter, and found that at normal pressure and 250 °C, the activity of the supported ruthenium-based catalyst (Ru-K / AC catalyst) was 10-20 times higher than that of the double-promoted fused iron (Fe-Al2O3-K2O) catalyst under the same conditions. The supported ruthenium-based catalyst shows relatively high activity and low energy consumption compared to iron during the ammonia synthesis process, and the supported ruthenium-based catalyst is insensitive to carbon oxides, has high stability, long service life, and the noble metal ruthenium can be recycled, and is hailed as the ideal "second-generation ammonia synthesis catalyst".

[0003] The supported ruthenium-based catalyst generally consists of a ruthenium metal precursor, a carrier, and various additives, which are loaded on the carrier by an impregnation method and converted into active components after reduction activation under certain conditions. There are interactions between ruthenium and the carrier, ruthenium and the additives, and the additives and the carrier in the catalyst. Among them, the carrier plays a role in dispersing, stabilizing, and regulating the performance in the catalyst. The type, structure, surface properties, etc. of the carrier have the greatest influence on the ammonia synthesis catalytic performance of the catalyst. Common carriers of supported ruthenium-based catalysts include activated carbon carriers, oxide carriers, zeolite molecular sieves, carbon-coated alumina, etc. Activated carbon has a high specific surface area, fast electron transfer rate, good electrical conductivity and heat resistance, strong adsorption capacity and developed pore structure, and the preparation raw materials are rich in sources and low in cost, and have been widely used as carriers for supported ruthenium-based catalysts.

[0004] As for the preparation method of the activated carbon carrier for ruthenium-based ammonia synthesis catalyst disclosed in Patent CN1260005C, the activated carbon after being treated at a high temperature of 1600-2500 °C is subjected to pore expansion treatment with a mixed gas of water vapor, oxygen-containing gas, nitrogen and / or Group 0 noble gas at a temperature of 250-500 °C for a treatment time of 2-36 hours. This technology overcomes the problem of the reduction of specific surface area and specific pore volume caused by high-temperature graphitization treatment by treating the high-temperature graphitized activated carbon with a mixed gas, and the porosity of the activated carbon is restored to varying degrees. However, some micropores or mesopores originally suitable for ruthenium loading may be expanded into macropores, the effective loading site density is relatively reduced, and ruthenium is unevenly dispersed, resulting in low catalytic performance of the ruthenium-based catalyst prepared with it as a carrier. Patent CN105396623B discloses a columnar activated carbon, its preparation method and a carrier for ruthenium-based ammonia synthesis catalyst, including the following steps: kneading a mixed aqueous solution containing coconut shell powder, binder, pore-expanding agent and activator to obtain a kneaded material; shaping the kneaded material into a columnar material, and carbonizing and activating the columnar material in an atmosphere furnace to obtain columnar activated carbon. This technology adds an appropriate amount of pore-expanding agent during the preparation of activated carbon, so that the obtained activated carbon has a macroporous structure from the source, and the problem of sharp decline in specific surface area and specific pore volume during graphitization will not occur. However, there is still room for improvement in terms of the particle size, dispersion of metal ruthenium particles and the activity of the catalyst.

[0005] In summary, it is necessary to develop an activated carbon carrier with a macroporous structure, which is also suitable for uniform dispersion of ruthenium, flexibly adjusting the particle size of metal ruthenium particles, and enabling the supported ruthenium-based catalyst to have high catalytic activity. Summary of the Invention

[0006] To solve the above technical problems, the present invention provides a preparation method and application of nitrogen-doped activated carbon for ruthenium-based catalyst carriers. First, using aniline and nanocellulose as raw materials, polyaniline-coated nanocellulose is prepared by chemical oxidative in-situ polymerization method. It is blended with a modified resol resin prepared from phenol, aminophenol derivatives and formaldehyde solution, and then nitrogen-doped supported activated carbon is prepared through curing, crushing, high-temperature carbonization, activation and graphitization. Since nanocellulose contains a large amount of carbon, hydrogen and oxygen elements, a large amount of gas will be generated during the preparation of activated carbon. As the gas escapes, pores are left inside the activated carbon, realizing the expansion of the pore structure of the activated carbon. In addition, nitrogen-doped activated carbon pore walls are in-situ generated around the space occupied by nanocellulose by polyaniline. The strongly electronegative nitrogen element helps to efficiently adjust the particle size of active metal ruthenium particles, and improve the activity and stability of the ammonia synthesis supported ruthenium-based catalyst prepared with it.

[0007] To achieve the above object, the following technical solutions are adopted:

[0008] A preparation method of nitrogen-doped activated carbon for ruthenium-based catalyst support, comprising the following steps:

[0009] 1) In-situ polymerize aniline on the surface of nanocellulose by oxidative polymerization to generate polyaniline-coated nanocellulose;

[0010] 2) Use phenol, aminophenol derivatives, and formaldehyde solution as raw materials, and react under the action of an alkali catalyst to obtain a viscous modified resole resin;

[0011] 3) Mix the polyaniline-coated nanocellulose and the modified resole resin evenly, and carry out curing, crushing, carbonization, activation, graphitization, grinding, and sieving to obtain nitrogen-doped supported activated carbon.

[0012] In step 1), the average diameter of the nanocellulose is 10 - 50 nm and the length is 100 - 250 nm. The mass ratio of the aniline to the nanocellulose is 3:0.25 - 0.35.

[0013] In step 1), the in-situ polymerization process is as follows: ultrasonically disperse the nanocellulose and aniline in a hydrochloric acid solution, add a surfactant and stir to form a stable suspension, dropwise add a mixture of an oxidant and the hydrochloric acid solution, control the temperature and react to obtain polyaniline-coated nanocellulose.

[0014] The ultrasonic dispersion power is 500 - 800 W, the frequency is 50 - 80 kHz, and the time is 10 - 30 min. The oxidant is selected from one or a combination of two or more of ammonium persulfate, hydrogen peroxide, and ferric chloride. The concentration of the hydrochloric acid solution is 0.4 - 0.6 mol / L. The surfactant is selected from one or a combination of two or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and sodium octadecyl sulfate. The stirring speed is 500 - 800 rpm, and the stirring time is 20 - 40 min. The mass ratio of the aniline, the surfactant, and the hydrochloric acid solution is 1 - 3:0.15 - 0.2:100. The molar ratio of the aniline to the oxidant is 1:1 - 1.1. The mass ratio of the oxidant to the hydrochloric acid solution in the mixture is 1 - 1.2:20. The dropping time of the mixture is 30 - 50 min. The temperature control is to control at 0 - 5 °C, and the reaction time is 3 - 5 h. After the reaction, it also successively includes suction filtration, alternate washing with alcohol and dilute hydrochloric acid, and vacuum drying. The concentration of the dilute hydrochloric acid is 0.2 - 0.4 mol / L. The number of washing times is 1 - 3 times. The alcohol is selected from one or a combination of two or more of methanol, ethanol, and propanol.

[0015] In step 2), the reaction is specifically as follows: uniformly mix phenol, aminophenol derivatives, and a catalyst, add formaldehyde solution and heat up to react, and after the reaction, carry out vacuum dehydration and cool to room temperature.

[0016] To improve the dispersion uniformity of polyaniline-coated nanocellulose in novolac resin, an appropriate amount of aminophenol derivative is needed to replace phenol, and the obtained modified novolac resin also has the effect of synergistically regulating the dispersion degree of ruthenium metal.

[0017] The temperature rise is to rise to 60-75°C and react for 3-5 h. The vacuum dehydration is to dehydrate for 1-3 h under the conditions of a vacuum degree of 0.01-0.09 MPa and a temperature of 40-60°C. The concentration of the formaldehyde solution is 30-37 wt%. The catalyst is an alkali solution with a concentration of 30-40 wt%, selected from one or a combination of two or more of sodium hydroxide solution, barium hydroxide solution, and potassium hydroxide solution. The aminophenol derivative is selected from one or a combination of two or more of p-aminophenol, o-aminophenol, and m-aminophenol, and preferably p-aminophenol. The mass ratio of phenol, aminophenol derivative, and formaldehyde solution is 1:0.2-0.3:1.3-1.5. The catalyst is 1-2 wt% of the sum of the masses of phenol and aminophenol derivative.

[0018] In step 3), the mass ratio of the polyaniline-coated nanocellulose to the modified novolac resin is 0.1-0.3:1, preferably 0.15-0.2:1. The curing is to cure at a temperature of 60-70°C for 0.5-1 h, then raise the temperature to 90-100°C and cure for 0.5-1 h, and finally cure at 160-180°C for 1-2 h. The mixing is to ultrasonically treat for 0.5-3 h under the conditions of a power of 500-800 W and a frequency of 20-40 kHz. The carbonization is a treatment of heating to 800-1000°C at a heating rate of 0.5-3°C / min in an inert atmosphere and then maintaining the temperature for 1-3 h. The activation is to perform an activation treatment with steam at a flow rate of 1-5 mL / min and a temperature of 200-330°C for 1-2 h. The graphitization is to perform a treatment at 2000-2500°C in an inert atmosphere for 0.5-2 h. The crushing is to crush to an average particle size of 0.5-1.5 cm. The grinding is to grind to an average particle size of 12-16 mesh. The mesh number of the sieve is 12-16 mesh.

[0019] The specific surface area of the nitrogen-doped activated carbon used as the ruthenium-based catalyst support obtained by the above preparation method is 1000-1500 m 2 / g, the mesopore volume is 0.6-1.05 mL / g, and the average pore diameter is 2-4 nm.

[0020] The present invention also provides an ammonia synthesis supported ruthenium-based catalyst, including the above nitrogen-doped activated carbon used as the ruthenium-based catalyst support, and based on the nitrogen-doped activated carbon used as the ruthenium-based catalyst support, the loading amount of ruthenium metal is 2-10 wt%, the loading amount of alkali metal is 10-20 wt%, and the loading amount of alkaline earth metal is 4-16 wt%.

[0021] A preparation method of a supported ruthenium-based catalyst for ammonia synthesis, which is prepared by an impregnation method.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] The present invention first uses aniline and nanocellulose as raw materials, and prepares polyaniline-coated nanocellulose by a chemical oxidation in-situ polymerization method. It is blended with a modified resol resin prepared from phenol, aminophenol derivatives, and formaldehyde solution, and then undergoes curing, crushing, high-temperature carbonization, activation, and graphitization to prepare nitrogen-doped carrier activated carbon. Since nanocellulose contains a large amount of carbon, hydrogen, and oxygen elements, a large amount of gas will be generated during the preparation of activated carbon. As the gas escapes, pores are left inside the activated carbon, realizing the expansion of the pore structure of the activated carbon. In addition, nitrogen-doped activated carbon pore walls are in-situ generated from polyaniline around the occupied space of nanocellulose. The strongly electronegative nitrogen element helps to efficiently regulate the size of active ruthenium metal particles, improving the activity and stability of the supported ruthenium-based catalyst for ammonia synthesis prepared therefrom. Description of the Drawings

[0024] Figure 1 It is the pore size distribution diagram of the nitrogen-doped carrier activated carbon in Example 1. Detailed Embodiments

[0025] The following further illustrates the present invention with specific examples, but is not limited to the content in the specification. Unless otherwise specified, the "parts" mentioned in the embodiments of the present invention are all parts by weight. The reagents used are all commercially available reagents in the art.

[0026] The average diameter of the nanocellulose is 15 nm, the length is 200 nm, and the brand is S-VCF-01, purchased from Seebio Technology (Shanghai) Co., Ltd.

[0027] Example 1

[0028] 1) Disperse 0.25 kg of nanocellulose S-VCF-01 and 3 kg of aniline in 100 kg of hydrochloric acid solution with a concentration of 0.6 mol / L by ultrasonic wave at a power of 500 W and a frequency of 75 KHz for 10 min. Add 0.15 kg of sodium dodecylbenzenesulfonate and stir to form a stable suspension. Dropwise add a mixture composed of ammonium persulfate with an equal molar amount to aniline and hydrochloric acid solution with a concentration of 0.6 mol / L at a mass ratio of 1:20. Finish dropping in 50 min and control the temperature at 0 °C for reaction for 5 h. After the reaction, filter by suction, wash alternately with ethanol and dilute hydrochloric acid with a concentration of 0.2 mol / L for 3 times, and vacuum dry at 60 °C and 0.07 MPa for 8 h to obtain polyaniline-coated nanocellulose;

[0029] 2) Mix 1 kg of phenol, 0.3 kg of p-aminophenol, and 0.026 kg of 32 wt% sodium hydroxide solution evenly, add 1.5 kg of 37 wt% formaldehyde solution, heat up to 75 °C and react for 5 h. After the reaction, dehydrate for 2 h under a vacuum of 0.075 MPa and at 60 °C, and then cool to room temperature to obtain a viscous modified resole resin.

[0030] 3) Ultrasonically mix 0.2 kg of polyaniline-coated nanocellulose and 1 kg of modified resole resin evenly for 3 h under the conditions of a power of 800 W and a frequency of 20 kHz. Cure at 70 °C for 0.5 h, raise the temperature to 100 °C and cure for 1 h, and cure at 180 °C for 2 h. Crush the cured product into particles with an average particle size of 1.5 cm, perform carbonization treatment in a nitrogen atmosphere by heating to 1000 °C at a heating rate of 3 °C / min and then keeping it at a constant temperature for 2 h, activate with water vapor at a flow rate of 3 mL / min and a temperature of 300 °C for 2 h, and then perform graphitization treatment at 2200 °C in a nitrogen atmosphere for 1.5 h. Finally, grind it to an average particle size of 16 mesh and sieve it through a 16-mesh sieve to obtain nitrogen-doped supported activated carbon.

[0031] Figure 1 Figure 7 is the pore size distribution diagram of the nitrogen-doped supported activated carbon in Example 1. It can be seen that the nitrogen-doped supported activated carbon prepared by the present invention belongs to activated carbon with a relatively high mesopore ratio.

[0032] 4) Take 1 kg of nitrogen-doped supported activated carbon and impregnate it with a mixed aqueous solution of Ba(NO3)2 and KNO3. Based on the weight of the carbon carrier, control the Ba content of the carrier to be 4 wt% and the K content to be 12 wt%. Evaporate the solvent in a water bath, dry it at 110 °C to remove water, and then impregnate the dried carrier modified with Ba(NO3)2 and Mg(NO3)2 with an aqueous RuCl3 solution. Based on the nitrogen-doped supported activated carbon, control the Ru content to be 4 wt%. Evaporate the solvent in a water bath, dry it at 110 °C to remove water, and then reduce it with hydrogen at normal pressure and 450 °C for 6 h to reduce RuCl3 to metallic ruthenium. After cooling to room temperature, obtain a supported ruthenium-based catalyst for ammonia synthesis.

[0033] Example 2

[0034] The rest is the same as in Example 1, except that in step 1), the dosage of nanocellulose S-VCF-01 is 0.35 kg.

[0035] Example 3

[0036] The rest is the same as in Example 1, except that in step 2), the dosage of p-aminophenol is 0.2 kg.

[0037] Example 4

[0038] The rest is the same as in Example 1, except that in step 3), the amount of polyaniline-coated nanocellulose used is 0.1 kg.

[0039] Example 5

[0040] The rest is the same as in Example 1, except that in step 3), the amount of polyaniline-coated nanocellulose used is 0.15 kg.

[0041] Example 6

[0042] The rest is the same as in Example 1, except that in step 3), the amount of polyaniline-coated nanocellulose used is 0.3 kg.

[0043] Example 7

[0044] 1) Disperse 0.35 kg of nanocellulose S-VCF-01 and 3 kg of aniline in 100 kg of hydrochloric acid solution with a concentration of 0.6 mol / L by ultrasonic wave at a power of 500 W and a frequency of 75 KHz for 10 min. Add 0.2 kg of sodium dodecylbenzenesulfonate and stir to form a stable suspension. Dropwise add a mixture composed of ammonium persulfate with an equimolar amount to aniline and hydrochloric acid solution with a concentration of 0.6 mol / L in a mass ratio of 1.2:20. Finish dropping in 50 min and control the temperature at 0 °C for reaction for 5 h. After the reaction, filter by suction, wash alternately with ethanol and dilute hydrochloric acid with a concentration of 0.2 mol / L for 3 times, and dry in vacuum at 60 °C and 0.07 MPa for 8 h to obtain polyaniline-coated nanocellulose.

[0045] 2) Mix 1 kg of phenol, 0.3 kg of p-aminophenol, and 0.026 kg of 32 wt% sodium hydroxide solution evenly, add 1.5 kg of 37 wt% formaldehyde solution, heat up to 75 °C and react for 5 h. After the reaction, dehydrate at a vacuum degree of 0.075 MPa and 60 °C for 2 h, and cool to room temperature to obtain a viscous modified resole resin.

[0046] 3) Mix 0.15 kg of polyaniline-coated nanocellulose and 1 kg of modified resole resin evenly by ultrasonic wave at a power of 800 W and a frequency of 20 kHz for 3 h, cure at a temperature of 70 °C for 0.5 h, raise the temperature to 100 °C and cure for 1 h, and cure at 180 °C for 2 h. Crush the cured product into particles with an average particle size of 1.5 cm, under a nitrogen atmosphere, heat to 1000 °C at a heating rate of 3 °C / min and then keep it at a constant temperature for 2 h for carbonization treatment, activate with water vapor with a flow rate of 5 mL / min and a temperature of 200 °C for 2 h, and then carry out graphitization treatment at 2200 °C under a nitrogen atmosphere for 1.5 h. Finally, grind to an average particle size of 16 mesh and sieve through a 16-mesh sieve to obtain nitrogen-doped supported activated carbon.

[0047] 4) Take 1 kg of nitrogen-doped supported activated carbon and impregnate it with an aqueous solution of a mixture of Ba(NO3)2 and KNO3. Based on the weight of the carbon support, control the Ba content of the support to be 4 wt% and the K content to be 12 wt%. Evaporate the solvent in a water bath, dry it at 110 °C to remove water, and then impregnate the dried support modified with Ba(NO3)2 and Mg(NO3)2 with an aqueous solution of RuCl3. Based on the nitrogen-doped supported activated carbon, control the Ru content to be 4 wt%. Evaporate the solvent in a water bath, dry it at 110 °C to remove water, and then reduce it with hydrogen at normal pressure and 450 °C for 6 h to reduce RuCl3 to metallic ruthenium. After cooling to room temperature, a supported ruthenium-based catalyst for ammonia synthesis is obtained.

[0048] Comparative Example 1

[0049] The rest is the same as in Example 1, except that in step 2), an equal mass of phenol is used to replace the aminophenol derivative.

[0050] Comparative Example 2

[0051] The rest is the same as in Example 1, except that polyaniline and nanocellulose are added to the modified resole resin in a direct blending manner:

[0052] 1) Disperse 3.25 kg of aniline in 1000 kg of a hydrochloric acid solution with a concentration of 0.6 mol / L by ultrasonic wave at a power of 500 W and a frequency of 75 KHz for 10 min. Add 0.15 kg of sodium dodecylbenzenesulfonate and stir to form a stable suspension. Dropwise add a mixture composed of ammonium persulfate with an equimolar amount to aniline and a hydrochloric acid solution with a concentration of 0.6 mol / L in a mass ratio of 1:20. Finish dropping in 50 min, control the temperature at 0 °C and react for 5 h. After the reaction, filter by suction, and wash alternately with ethanol and a dilute hydrochloric acid solution with a concentration of 0.2 mol / L for 3 times. Dry at 60 °C and 0.07 MPa in vacuum for 8 h to obtain polyaniline microspheres;

[0053] 2) Mix 1 kg of phenol, 0.3 kg of p-aminophenol, and 0.026 kg of a 32 wt% sodium hydroxide solution evenly, add 1.5 kg of a 37 wt% formaldehyde solution, heat up to 75 °C and react for 5 h. After the reaction, dehydrate at a vacuum degree of 0.075 MPa and 60 °C for 2 h, and cool to room temperature to obtain a viscous modified resole resin;

[0054] 3) Mix 0.185 kg of polyaniline microspheres, 0.015 nanocellulose and 1 kg of modified resole evenly by ultrasonic treatment for 3 h under the conditions of a power of 800 W and a frequency of 20 kHz. Cure at 70 °C for 0.5 h, raise the temperature to 100 °C and cure for 1 h, and cure at 180 °C for 2 h. Crush the cured product into particles with an average particle size of 1.5 cm, carry out carbonization treatment by heating to 1000 °C at a heating rate of 3 °C / min under a nitrogen atmosphere and then keeping the temperature constant for 2 h, activate with steam with a flow rate of 3 mL / min and a temperature of 300 °C for 2 h, and then carry out graphitization treatment at 2200 °C under a nitrogen atmosphere for 1.5 h. Finally, grind to an average particle size of 16 mesh and sieve through a 16-mesh sieve to obtain nitrogen-doped supported activated carbon.

[0055] 4) Take 1 kg of nitrogen-doped supported activated carbon and impregnate it with an aqueous solution of Ba(NO3)2 and KNO3. Based on the weight of the carbon carrier, control the Ba content of the carrier to be 4 wt% and the K content to be 12 wt%. Evaporate the solvent in a water bath, dry at 110 °C to remove water, and then impregnate the dried carrier modified with Ba(NO3)2 and Mg(NO3)2 with an aqueous solution of RuCl3. Based on the nitrogen-doped supported activated carbon, control the Ru content to be 4 wt%. Evaporate the solvent in a water bath, dry at 110 °C to remove water, and then reduce with hydrogen at normal pressure and 450 °C for 6 h to reduce RuCl3 to metallic ruthenium. After cooling to room temperature, obtain a supported ruthenium-based catalyst for ammonia synthesis.

[0056] Perform the following performance tests on the nitrogen-doped supported activated carbon or supported ruthenium-based catalyst for ammonia synthesis prepared in the above examples and comparative examples:

[0057] Nitrogen-doped supported activated carbon

[0058] Specific surface area and pore structure: Measured by a NOVA 1000e type pore structure and specific surface area tester. The sample is degassed at 350 °C for 2 h, and liquid nitrogen is used as the adsorption medium. N2 adsorption is measured at 77 K and within the range of relative pressure (P / P0) of 10 -6 -1. The specific surface area and pore size distribution are calculated by the BET equation and the BJH equation respectively.

[0059] Supported ruthenium-based catalyst for ammonia synthesis

[0060] Evaluation of catalytic activity and stability: The catalytic activity evaluation is carried out in a NH3-CMAT9000 high-pressure reaction device. The inner diameter of the reactor is a fixed bed of 14 mm. The catalyst particles are 16 mesh, the packed volume is 2 mL, and the catalyst is loaded in the isothermal zone of the reactor. The reaction gas is a mixture of nitrogen and hydrogen, and the volume ratio of H2 to N2 is 3:1. The reaction temperature is 425 °C, and the space velocity is 10000 h -1, ammonia synthesis was carried out under the condition of a pressure of 10 Mpa, and the initial activity of the catalyst was recorded after stabilization; after the above catalyst was heat-treated at 520 °C and 1.0 Mpa for 36 h, ammonia synthesis was carried out under the same conditions (temperature of 425 °C, space velocity of 10000 h -1 , under the condition of a pressure of 10 Mpa), the catalytic activity of the catalyst was recorded after stabilization, and the catalytic activity decay rate after heat aging treatment at 520 °C was calculated. The catalyst activity was expressed as the volume percentage of ammonia in the reactor outlet gas.

[0061] Ru particle size and dispersion: The dispersion and particle size of metallic ruthenium were determined by CO pulse chemisorption method. 0.2 g of the supported ruthenium-based ammonia synthesis catalyst was placed in the quartz reaction tube of a Micromeritics AutoChem 2910 chemisorption instrument, reduced at 400 °C in a H2 atmosphere for 4 h, switched to He purge for 1.5 h, cooled to room temperature, and after the baseline was stable, a CO pulse adsorption experiment was carried out until the pulse peak area remained unchanged. The dispersion of Ru was calculated from the amount of adsorbed CO. The larger the dispersion, the more uniform the dispersion.

[0062] Table 1 Performance test results

[0063]

[0064] It can be seen from the specific surface area and pore structure test results of Example 1, Examples 4-6 in Table 1 that polyaniline-coated nanocellulose has the effect of expanding pores: as the amount of polyaniline-coated nanocellulose increases, the average pore diameter of the activated carbon shows an increasing trend, and the mesopore volume first increases and then decreases; when the amount of polyaniline-coated nanocellulose is 0.15 - 0.2 kg, the activated carbon can provide a spatial structure conducive to material transport and loading, and the catalytic activity of the catalyst can be as high as 23.6%. From the catalytic activity decay rate, it can be seen that polyaniline-coated nanocellulose also has an obvious effect of improving the catalyst stability. After heat treatment at 520 °C, the catalytic activity is basically not lost. It shows that the catalyst prepared by the present invention has the advantages of both high catalytic activity and good catalytic stability.

[0065] It can be seen from Example 1, Example 3, and Comparative Example 1 in Table 1 that aminophenol derivatives have little effect on the pore structure of activated carbon, but have a more obvious effect on the dispersion of metallic ruthenium. It is speculated that aminophenol derivatives have a significant effect on the distribution of polyaniline-coated nanocellulose in the resin.

[0066] It can be seen from Example 1 and Comparative Example 2 that only when polyaniline and nanocellulose are used in the form of polyaniline-coated nanocellulose can activated carbon with excellent pore structure, most conducive to uniform loading of metal materials and particle size adjustment be prepared.

[0067] The above detailed description is a specific description of one of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification without departing from the present invention shall be included within the scope of the technical solution of the present invention.

Claims

1. A method for preparing nitrogen-doped activated carbon for a ruthenium-based catalyst carrier, characterized in that: The steps include: 1) using an oxidative polymerization method to in-situ polymerize aniline on the surface of nanocellulose to generate polyaniline, thereby obtaining polyaniline-coated nanocellulose; 2) using phenol, aminophenol derivatives and formaldehyde solution as raw materials, reacting under the action of an alkali catalyst to obtain a viscous modified resol phenolic resin; 3) The polyaniline-coated nanocellulose and the modified resol phenolic resin are uniformly mixed, and then solidified, crushed, carbonized, activated, graphitized, ground, and sieved to obtain nitrogen-doped carrier activated carbon.

2. The method for preparing nitrogen-doped activated carbon for ruthenium-based catalyst carrier according to claim 1, characterized in that: In step 1), the average diameter of the nanocellulose is 10-50 nm and the length is 100-250 nm; the mass ratio of aniline to nanocellulose is 3:0.25-0.

35.

3. The method for preparing nitrogen-doped activated carbon for ruthenium-based catalyst carrier according to claim 1, characterized in that: In step 1), the in-situ polymerization process is: ultrasonically dispersing nanocellulose and aniline in a hydrochloric acid solution, adding a surfactant and stirring to form a stable suspension, dripping a mixture of an oxidant and a hydrochloric acid solution, and controlling the temperature to react to obtain polyaniline-coated nanocellulose.

4. The method for preparing nitrogen-doped activated carbon for ruthenium-based catalyst carrier according to claim 3, characterized in that: The mass ratio of the aniline, surfactant and hydrochloric acid solution is 1-3:0.15-0.2:100; the molar ratio of the aniline to the oxidant is 1:1-1.1; and the mass ratio of the oxidant to the hydrochloric acid solution in the mixture is 1-1.2:

20.

5. The method for preparing nitrogen-doped activated carbon for ruthenium-based catalyst carrier according to claim 1, characterized in that: In step 2), the reaction is specifically as follows: phenol, aminophenol derivatives and catalyst are uniformly mixed, formaldehyde solution is added and the temperature is raised for reaction, vacuum dehydration is performed after the reaction is completed, and the mixture is cooled to room temperature.

6. The method for preparing nitrogen-doped activated carbon for ruthenium-based catalyst carrier according to claim 5, characterized in that: The mass ratio of the phenol, the aminophenol derivative and the formaldehyde solution is 1:0.2-0.3:1.3-1.5; the aminophenol derivative is selected from one or a combination of two or more of p-aminophenol, o-aminophenol and m-aminophenol, preferably p-aminophenol.

7. The method for preparing nitrogen-doped activated carbon for ruthenium-based catalyst carrier according to claim 5, characterized in that: The temperature is raised to 60-75°C for reaction for 3-5h; the vacuum dehydration is performed at a vacuum degree of 0.01-0.09MPa and a temperature of 40-60°C for dehydration for 1-3h; the concentration of the formaldehyde solution is 30-37wt%; the catalyst is an alkali solution with a concentration of 30-40wt%, selected from one or a combination of two or more of a sodium hydroxide solution, a barium hydroxide solution, and a potassium hydroxide solution; the catalyst is 1-2wt% of the sum of the mass of phenol and an aminophenol derivative.

8. The method for preparing nitrogen-doped activated carbon for ruthenium-based catalyst carrier according to claim 1, characterized in that: In step 3), the mass ratio of the polyaniline-coated nanocellulose to the modified resol phenolic resin is 0.1-0.3:1, preferably 0.15-0.2:

1.

9. A supported ruthenium catalyst for ammonia synthesis, characterized in that: It includes the nitrogen-doped activated carbon for a ruthenium-based catalyst carrier as described in any one of claims 1-8, and a loading amount of 2-10wt% of metallic ruthenium, a loading amount of 10-20wt% of alkali metal, and a loading amount of 4-16wt% of alkaline earth metal based on the nitrogen-doped activated carbon for a ruthenium-based catalyst carrier.

10. A method for preparing the supported ruthenium catalyst for ammonia synthesis according to claim 9, characterized in that: Prepared by dipping method.

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