Supported carbon-based catalyst as well as preparation method and application thereof

Abstract

The invention relates to a supported carbon-based catalyst, a preparation method and application, the supported carbon-based catalyst catalyzes a hydroxylamine nitrate solution to decompose to obtain a liquid-phase product and a gas-phase product; the loading amount of metal elements in the loaded carbon-based catalyst is 0.1-15 wt%; the metal element is selected from one of Pt, Ru, Rh and Pd; a carrier of the supported carbon-based catalyst is coconut shell activated carbon; the supported carbon-based catalyst is selected from at least one of Pt / C, Ru / C, Rh / C and Pd / C; the liquid phase product is selected from at least one of NH4 < + >, H < + >, NO3 <-> and NO2 <->; the gas phase product is selected from at least one of N2O, N2, NO and NO2. The supported carbon-based catalyst adopted by the invention is suitable for catalytic decomposition of low-concentration HAN, and can realize qualitative or quantitative analysis of gas-phase products and liquid-phase products generated by decomposition.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of catalysis, and particularly relates to a supported carbon-based catalyst, a preparation method and application thereof. BACKGROUND

[0002] Hydroxylammonium nitrate (HAN) is a new type of high-energy ionic liquid material, which has many advantages. It provides high energy density, fast and stable decomposition characteristics, complete combustion without residue, clean emissions, large volume gas generation, low signature characteristics, and non-toxicity. HAN can be used as a gas generating agent material, an ionic liquid explosive, a low signature high-energy oxidizer, and can also be used as a raw material for synthesizing other high-energy ionic liquids, and its application range covers green propulsion systems for civil space and aviation auxiliary power, and meets the demand for non-toxic solutions. Therefore, the decomposition of HAN is worth further studying and exploring.

[0003] At present, the research on HAN decomposition mainly focuses on the final gas species and the decomposition temperature at the macro level. For example, Chambreau et al. studied the reaction activity of HAN water aerosol on Cu and Ir targets, and analyzed using a tunable vacuum ultraviolet photoionization time-of-flight aerosol mass spectrometer (J. Phys. Chem. Lett. 2017, 8, 10, 2126-2130). After the HAN solution was atomized to form a water aerosol, it was catalytically decomposed on a pure Cu and Ir target at 250-300℃, and then the reaction products were identified by mass-to-charge ratio and ionization energy, including NH3, H2O, NO, hydroxylamine (HA), HNO3 and a small amount of NO2. Hwang et al. pointed out that the thermal decomposition temperatures of HAN-based propellants were 150.0℃, 160.5℃ and 170.3℃ (corresponding to 83.9% HAN, (83% HAN)+MeOH and (55% HAN)+MeOH). However, under the action of a 30% Ir / Al2O3 catalyst, the catalytic decomposition temperature was lower, which was 78.7℃, 88.7℃ and 96.2℃, respectively, and the catalytic decomposition product species was not reported (Combust. Flame. 2014, 4, 161, 1109-1116). Amrousse et al. pointed out that a 20%Ir-10%CuO catalyst (Combust. Flame. 2015, 6, 162, 2686-2692) had a lower decomposition starting temperature for a 73.6% HAN-based monopropellant, which was reduced from 201℃ (thermal decomposition) to 65℃ (catalytic decomposition), and the main decomposition products were N2, NO, N2O, NO2, H2O and NH3.

[0004] Based on the above, the main problems faced by high-concentration HAN catalytic decomposition research are as follows: 1. The catalyst used has a high noble metal loading. 2. The gas-phase products after catalytic decomposition are diverse, and the selectivity of the gas-phase products is poor. At the same time, the high acidity of the HAN solution can corrode the carrier, leading to poor cyclic stability of the catalyst. 3. No liquid-phase products.

[0005] Based on this, researchers have conducted further research on the above problems. For example, Ruchika et al. (RSC Adv., 2018, 8, 22293) prepared a non-noble metal catalyst, 26% Co / CeO2 catalyst, by co-precipitation method. This catalyst showed excellent catalytic activity and stability in decomposing HAN, reducing the decomposition temperature of 75% HAN from 199℃ (thermal decomposition) to 139℃ (catalytic decomposition). Compared with the traditional 30% Ir / Al2O3 catalyst, this new catalyst not only performs well in physical integrity and resistance to poisoning, but also maintains good catalytic activity after 50 uses. At the same time, through infrared spectrum detection during the decomposition process, it was found that HNO3, N2O, NO2, and N2 were produced in the process. Deyan Yu et al. (New J. Chem., 2024, 48, 8660) prepared a 5% Ru / C catalyst for treating hydrazine nitrate (HN) and HAN in the Purex process by an equal-volume impregnation method. In a fixed-bed experiment simulating radioactive nitric acid waste liquid, it was found that the catalyst could completely decompose HN and HAN at 80℃ in 35min. The feed flow rate in the experimental conditions was 0.5mL / min, and the WHSV of HAN and HN was 0.42h -1 and 0.24 h -1 , respectively. The reaction was terminated with the complete decomposition of HN and HAN, and the gas-liquid phase products were not analyzed and detected. Dalsan Yoo et al. (Catalysts, 2024, 14, 2, 116) prepared a honeycomb catalyst with cordierite (5SiO2-2MgO-2Al2O3) as the carrier and Cu as the loading metal. The experimental results showed that the Cu-based catalyst had a significant advantage in reducing the initial decomposition temperature of 80% HAN solution. Specifically, compared with the thermal decomposition process (124℃), the 15% Cu-based catalyst reduced the initial decomposition temperature by 45.0℃. The study also found that there was no significant difference in specific surface area and pore size among different metal-loaded catalysts (Mn, Co, Cu, Ir), so the influence of pore structure on activity could be ruled out. In addition, the metal loading was also similar, which meant that the higher activity of the Cu-based catalyst was not due to the physical properties, but was likely due to the intrinsic activity of Cu metal being superior to other metals. At the same time, through infrared spectrum detection during the decomposition process, it was found that HNO2, N2O, and NO2 were produced in the process.

[0006] In summary, the current research on HAN catalytic decomposition is mostly focused on high concentration solution system, the final products of the reaction are quite different and lack of regularity, and there is little real-time monitoring of ion change process in liquid phase. Therefore, it is of great significance to study the evolution of ion concentration in the process of low concentration HAN catalytic decomposition and its influence on the reaction path, for the selective regulation of liquid and gas phase products.

[0007] To this end, a catalyst with low noble metal loading, high activity and good selectivity is developed, and the gas and liquid phase products in the process of HAN decomposition are systematically analyzed qualitatively and quantitatively to deeply analyze the selective regulation of products. In order to avoid the interference of side reactions between the carrier and HAN with the experimental results, activated carbon with excellent chemical inertness is selected as the carrier, and the prepared Pt / C, Ru / C, Rh / C and Pd / C catalysts exhibit good cycle stability and can still maintain stable catalytic performance after 5 cycles, while specific gas and liquid phase products can be obtained. This strategy not only effectively reduces the interference of the reaction system and product detection, but also ensures the efficiency and repeatability of the catalytic process, providing reliable technical support for realizing the controllable decomposition of HAN at low temperature. SUMMARY

[0008] The purpose of the present application is to provide a catalyst for efficient catalytic decomposition of hydroxylamine nitrate, which is applied to HAN catalytic decomposition reaction and regulates its gas and liquid phase products.

[0009] According to the first aspect of the present application, a supported carbon-based catalyst is provided, wherein the loading amount of metal elements in the supported carbon-based catalyst is 0.1-15wt%; The metal element is selected from one of Pt, Ru, Rh and Pd; The carrier of the supported carbon-based catalyst is coconut activated carbon; The supported carbon-based catalyst is selected from at least one of Pt / C, Ru / C, Rh / C and Pd / C.

[0010] According to the second aspect of the present application, a preparation method of a supported carbon-based catalyst is provided, wherein a metal salt solution is impregnated into coconut activated carbon in equal volume to obtain a carbon-based catalyst with different loading amounts, and then stirring, standing for 4-24h, drying at 80-120℃ for 6-24h, reduction and passivation are carried out to obtain a supported carbon-based catalyst. The concentration of the metal salt solution is 0.1-10wt. %; The metal salt is selected from one of rhodium acetate, rhodium nitrate, rhodium chloride, palladium acetate, palladium nitrate, palladium chloride, platinum acetate, platinum nitrate, platinum chloride, ruthenium acetate, ruthenium nitrate and ruthenium chloride.

[0011] Based on the above technical scheme, the reduction is specifically: placing the dried catalyst in a tube furnace to increase the temperature at a rate of 2-5°C / min to 200-400°C for 1-4h; the reducing atmosphere is H2 / Ar mixed gas, wherein the volume percentage of H2 is 10-15%.

[0012] Based on the above technical scheme, the passivation is specifically: placing the reduced catalyst in an air / Ar atmosphere, wherein the volume percentage of air is 2-3%, and passivating for 8-24h to obtain a supported carbon-based catalyst.

[0013] According to a third aspect of the present application, a supported carbon-based catalyst is provided for use in a hydroxylamine nitrate decomposition reaction, characterized in that the supported carbon-based catalyst is used to catalyze the decomposition of a hydroxylamine nitrate solution to obtain a liquid phase product and a gas phase product. The liquid phase product is selected from at least one of NH4 + , H + , NO3 - , and NO2 - . The gas phase product is selected from at least one of N2O, N2, NO, and NO2.

[0014] Based on the above technical scheme, the mass ratio of the supported carbon-based catalyst to the hydroxylamine nitrate solution is 1:100-100:1.

[0015] Based on the above technical scheme, the hydroxylamine nitrate decomposition is specifically: using a kettle reactor or a fixed bed reactor to decompose the hydroxylamine nitrate solution, reacting at 20-100°C for 1min-4h, and the mass space velocity WHSV is 0.1-100h -1 .

[0016] Based on the above technical scheme, the concentration of the hydroxylamine nitrate solution is 0.1-30 wt.%.

[0017] Based on the above technical scheme, the concentration of the hydroxylamine nitrate solution is 0.1-10 wt.%.

[0018] Based on the above technical scheme, when the supported carbon-based catalyst is Ru / C, the gas phase product is N2O and NO; When the supported carbon-based catalyst is Rh / C, the gas phase product is N2O and N2; When the supported carbon-based catalyst is Pt / C and / or Pd / C, the gas phase product is N2O, N2, NO, and NO2; When the supported carbon-based catalyst is Pt / C, Ru / C, Rh / C, and Pd / C, the liquid phase product is NH4 + , H + , NO3 - , and NO2- . BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 XRD patterns of catalysts of embodiments 2, 4, 6 of the present application.

[0020] Figure 2 SEM images of catalysts of embodiments 2, 4, 6 of the present application.

[0021] Figure 3 TEM images of catalysts of embodiments 2, 4, 6 of the present application.

[0022] Figure 4 Activity evaluation chart (left) and gas composition chart (right) of embodiments 6, 7, 8, 9 and comparative example 1 of the present application.

[0023] ADVANTAGEOUS EFFECTS The technical solution disclosed by the present application designs a catalyst for efficient catalytic decomposition of HAN and an application method thereof. The catalyst has the advantages of easy preparation, high catalytic efficiency and strong product selectivity, can generate specific gas-liquid phase products in a directional manner, and realizes qualitative and quantitative analysis of target products. DETAILED DESCRIPTION

[0024] The present application will be further described by examples below, but in no way limits the scope of the present application.

[0025] Unless otherwise specified, the reagents used in the present application are obtained by purchase, and the activated carbon carrier used is coconut shell activated carbon purchased from Hainan Xingguang Activated Carbon Co., Ltd., with a specific surface area of about 900 m 2 / g and an average pore size of about 3 nm; before formal use, the activated carbon is treated with 33% nitric acid at 80°C for 24 hours to remove surface impurities; then washed with deionized water to neutral and dried in an oven at 120°C; finally, sieved through a 100 mesh sieve and sealed for storage.

[0026] The gas phase products of the decomposition of hydroxylamine nitrate in the application example are qualitatively and quantitatively analyzed by mobile mass spectrometry, and the liquid phase products are qualitatively and quantitatively analyzed by stepwise detection and analysis by ultraviolet spectrophotometer, potentiometric titrator, ion chromatograph and electron paramagnetic resonance; wherein the model of the mobile mass spectrometer is GAM 200 (InProgress Instruments), the qualitative method is MID, and the quantitative method is MCD; The model of the ion chromatograph is ICS-5000+ (Thermo), NH4 +The detection scheme uses a CS12A chromatographic column with a column temperature of 30°C; the eluent is 8 mmol / L CH4SO3 aqueous solution, the flow rate is 1 mL / min; the suppression current is set to 30 mA, and a chemical detector is used for detection; NO2 - , NO3 - The qualitative and quantitative detection scheme uses an AS22 chromatographic column with a column temperature of 30°C; the eluent is 4.5 mmol / L Na2CO3 and 1.4 mmol / L NaHCO3 aqueous solution, the flow rate is 1 mL / min; the detection uses a chemical suppressor model AMMS 300 (4 mm) and a conductivity detector; The conversion rate of NO3 - , the yield of NO2 - , and the yield of NH4 + in the application example are calculated according to the following formulas: The conversion rate of NO3 - = (the molar amount of NO3 - in the feed - the molar amount of NO3 - in the product) / (the molar amount of NO3 - in the feed) x 100%; The yield of NO2 - = (the molar amount of NO2 - in the product) / (the molar amount of NO3 - in the feed) x 100%; The yield of NH4 + = (the molar amount of NH4 + in the product) / (the molar amount of NH3OH + in the feed) x 100%.

[0027] The model of the ultraviolet spectrophotometer is Lambda 950 (PerkinElmer); NH3OH + The detection scheme is based on the reducing property of NH3OH + to reduce Fe 3+ , and then using 1,10-phenanthroline and the reduced Fe 2+ to form a complex, and calculating the consumption according to the stoichiometric ratio; The calculation formula of the HAN conversion rate in the application example is as follows: HAN conversion rate = NH3OH + conversion rate = (the molar amount of NH3OH + in the feed - the molar amount of NH3OH + in the product) / (the molar amount of NH3OH + in the feed) x 100%.

[0028] The model of the potentiometric titrator is 801 pH Meter (Metrohm); H + The detection scheme is determined by using a pH electrode equipped with an automatic potentiometric titrator, and the pH slope is greater than or equal to 96% before determination; the data is determined in triplicate, and the average value is taken; The yield of H + in the application example is calculated according to the following formula: The yield of H + = (the molar amount of H + in the product - the molar amount of H + in the feed) / (the molar amount of NH3OH + in the feed) x 100%; The N balance = (the molar amount of NH4 + in the product + the molar amount of NH3OH + in the product + the molar amount of NO3 - in the product + the molar amount of NO2 - in the product + the molar amount of gas) / (2 x the molar amount of HAN in the feed) x 100%.

[0029] Example 1: Synthesis of 0.5 wt% Rh / C catalyst 0.029 g of rhodium nitrate (Rh (NO3) 3·3H2O) was dissolved in 5 ml of water to form a rhodium nitrate solution with a concentration of 0.58 wt. %; 3.03 ml of the rhodium nitrate solution was impregnated onto 0.995 g of activated carbon carrier by equal volume impregnation method. After sufficient stirring, it was left to stand for 4 h, and then dried in a drying oven at 100℃ overnight; then the dried catalyst was calcined in a tube furnace, and the program was to heat to 200℃ at a rate of 5℃ / min and keep for 2 h, and the process was reduced in a reducing atmosphere of 5% H2 / Ar. After cooling to room temperature, the final passivation was carried out in an atmosphere of 1% Air / Ar for 8 h, and 0.5 wt% Rh / C catalyst was obtained, and the loading of Rh in the catalyst was 0.49 wt%.

[0030] Example 2: Synthesis of 5 wt% Rh / C catalyst 0.29 g of rhodium nitrate (Rh (NO3) 3·3H2O) was dissolved in 5 ml of water to form a rhodium nitrate solution with a concentration of 5.5 wt. %, and 3.03 ml of the rhodium nitrate solution was impregnated onto 0.95 g of activated carbon by equal volume impregnation method. The remaining steps were consistent with Example 1, and the XRD characterization results of the obtained 5 wt% Rh / C supported catalyst are shown in Figure 1 , and it can be seen that there is no diffraction peak of Rh in the XRD pattern; the SEM and TEM images are shown in Figure 2 、 3As shown, the SEM image of 5 wt% Rh / C did not reveal any Rh distribution on the support, and no obvious agglomeration was observed on the TEM surface, indicating that Rh is highly dispersed on the activated carbon support. The Rh loading in the catalyst is 4.94 wt%.

[0031] Example 3: Synthesis of 0.5 wt% Rh / C catalyst 0.016 g of rhodium acetate (Rh(CH3COO)2·H2O) was dissolved in 5 ml of water to form a 0.32 wt.% rhodium acetate solution. 3.26 ml of the rhodium acetate solution was then impregnated onto a 0.995 g activated carbon support using an equal-volume impregnation method. The static drying process was the same as in Example 1. The dried catalyst was then calcined in a tube furnace, with the temperature increased to 300°C at a rate of 5°C / min and held for 2 hours. This reduction process was carried out in a 10% H2 / Ar reducing atmosphere. After cooling to room temperature, the catalyst was passivated for 8 hours in a 2% Air / Ar atmosphere to obtain a 0.5 wt% Rh / C catalyst, in which the Rh loading was 0.49 wt%.

[0032] Example 4: Synthesis of 5 wt% Rh / C catalyst The difference from Example 3 lies in the concentration of the rhodium acetate solution. Specifically, 0.16 g of rhodium acetate (Rh(CH3COO)2·H2O) was dissolved in 5 ml of water to form a 3.10 wt.% rhodium acetate solution. Then, 3.36 ml of the rhodium acetate solution was impregnated onto a 0.95 g activated carbon support using an equal-volume impregnation method. The remaining procedures were consistent with Example 3, yielding a 5 wt% Rh / C supported catalyst. The XRD characterization results of the catalyst are as follows: Figure 1 As shown, there are no Rh diffraction peaks in the XRD pattern; the SEM and TEM images are as follows. Figure 2 , 3 As shown, no Rh distribution was observed on the support in the SEM image of 5 wt% Rh / C, and no obvious agglomeration was observed on the TEM surface, indicating that Rh is highly dispersed on the activated carbon support. The Rh loading in the catalyst is 4.95 wt%.

[0033] Example 5: Synthesis of 0.5 wt% Rh / C catalyst A 0.02 g rhodium chloride (RhCl3-3H2O) was dissolved in 5 ml water to form a rhodium chloride solution with a concentration of 0.4 wt. %, and 3.21 ml of the rhodium chloride solution was impregnated onto 0.995 g of activated carbon support by equal volume impregnation method. After sufficient stirring, it was left to stand for 4 h, and then dried in a drying oven at 100 °C overnight. The dried catalyst was calcined in a tube furnace, with a temperature program of 5 °C / min to 400 °C and held for 2 h, and the process was reduced in a reducing atmosphere of 15% H2 / Ar. After cooling to room temperature, the final passivation was performed in an atmosphere of 3% Air / Ar for 8 h, to obtain a 0.5 wt% Rh / C catalyst, and the loading of Rh in the catalyst was 0.48 wt%.

[0034] Example 6: Synthesis of 5 wt% Rh / C catalyst The difference from Example 5 is that the concentration of the rhodium chloride solution is different, i.e. 0.20 g rhodium chloride (RhCl3-3H2O) was dissolved in 5 ml water to form a rhodium chloride solution with a concentration of 3.8 wt. %, and 3.37 ml of the rhodium chloride solution was impregnated onto 0.95 g of activated carbon support by equal volume impregnation method. The rest of the process was consistent with Example 5, and the XRD pattern of the 5 wt% Rh / C supported catalyst is shown in Figure 1 , and there is no diffraction peak of Rh in the XRD pattern; the SEM and TEM images are shown in Figure 2 , 3 , and no distribution of Rh on the support was observed in combination with the SEM image of the 5 wt% Rh / C, and there was no obvious agglomeration on the TEM surface, indicating that Rh was highly dispersed on the activated carbon support. The loading of Rh in the catalyst was 4.92 wt%.

[0035] Example 7: Synthesis of 5 wt% Pd / C catalyst A 0.17 g palladium chloride (PdCl2-2H2O) was dissolved in 5 ml water to form a palladium chloride solution with a concentration of 3.3 wt. %, and 3.03 ml of the palladium chloride solution was impregnated onto 0.95 g of activated carbon support by equal volume impregnation method. After sufficient stirring, it was left to stand for 4 h, and then dried in a drying oven at 100 °C overnight. The dried catalyst was calcined in a tube furnace, with a temperature program of 5 °C / min to 400 °C and held for 2 h, and the process was reduced in a reducing atmosphere of 15% H2 / Ar. After cooling to room temperature, the final passivation was performed in an atmosphere of 3% Air / Ar for 8 h, to obtain a 5 wt% Pd / C catalyst, and the loading of Pd in the catalyst was 4.94 wt%.

[0036] Example 8: Synthesis of 5 wt% Pt / C catalyst A 0.17 g of platinum chloride (PtCl4·5H2O) was dissolved in 5 ml of water to form a platinum chloride solution with a concentration of 3.3 wt. %, and 3.29 ml of the platinum chloride solution was impregnated onto 0.95 g of the activated carbon carrier by the equal volume impregnation method. The rest of the process was consistent with Example 7, and 5 wt% Pt / C catalyst was obtained, with a loading of Pt in the catalyst being 4.95 wt%.

[0037] Example 9: Synthesis of 5 wt% Ru / C catalyst A 0.21 g of ruthenium chloride (RuCl3·3H2O) was dissolved in 5 ml of water to form a ruthenium chloride solution with a concentration of 4.03 wt. %, and 3.18 ml of the ruthenium chloride solution was impregnated onto 0.95 g of the activated carbon carrier by the equal volume impregnation method. The rest of the process was consistent with Example 7, and 5 wt% Ru / C catalyst was obtained, with a loading of Ru in the catalyst being 4.94 wt%.

[0038] Application Example 1 The catalyst prepared in Example 6 was used for the HAN reaction. The HAN decomposition was carried out in a glass batch reactor, and 0.55 mg of the catalyst was used for each test; 11 g of 1 wt% HAN solution was reacted at different temperatures (20, 30, 50, 70, and 90 ℃) for 1 h, and the reaction was terminated by cooling the reactor with cold water. The specific catalytic reaction results and the gas composition are shown in Table 1.

[0039] Table 1 Catalytic reaction results and gas composition of 5% Rh / C catalyst

[0040] As can be seen from the table, the catalyst prepared in Example 6 has excellent selectivity for liquid phase products NH4 + and H + during the catalytic decomposition of HAN, and the selectivity is improved with the increase of catalytic activity. With the increase of the reaction temperature, the generation of NO2 - and NO3 - in the system presents a trend of first decreasing and then increasing. The continuous release of the gas phase products during the catalytic process, which only contains N2O and N2, indicates that the catalyst has good reaction path control ability.

[0041] Application Example 2 The catalyst prepared in Example 7 was used for the HAN reaction. The HAN decomposition was carried out in a glass batch reactor, and 0.55 mg of the catalyst was used for each test; 11 g of 1 wt% HAN solution was reacted at different temperatures (20, 30, 50, 70, and 90 ℃) for 1 h, and the reaction was terminated by cooling the reactor with cold water. The specific catalytic reaction results and the gas composition are shown in Table 2.

[0042] Table 2 Catalytic reaction results and gas composition of 5% Pd / C catalyst

[0043] According to the data in Table 2, compared with Example 6, the catalyst prepared in Example 7 has lower catalytic activity, but shows higher selectivity of liquid phase products NH4 + , H + and NO2 - . It is worth noting that this selectivity increases with the enhancement of catalytic activity. In terms of gas phase products, the main component is N2O, accounting for about 80% of the total gas, and the rest is NO, NO2 and N2, indicating that the reaction path is more inclined to generate nitrogen-containing oxide products under the action of this catalyst.

[0044] Application Example 3 The catalyst prepared in Example 8 was used for HAN reaction. HAN decomposition was carried out in a glass batch reactor, and 0.55 mg of catalyst was used for each test; after 11 g of 1 wt% HAN solution was reacted at different temperatures (20, 30, 50, 70, 90°C) for 1 h, the reaction was terminated by cooling the reactor with cold water, and the specific catalytic reaction results and gas composition are shown in Table 3.

[0045] Table 3 Catalytic reaction results and gas composition of 5% Pt / C catalyst

[0046] According to the data in Table 3, under the condition of normal pressure and low temperature, the catalysts prepared in Example 8 and Example 6 show similar HAN catalytic activity, and both of them show high selectivity of liquid phase products NH4 + and H + , and this selectivity increases with the enhancement of catalytic activity. With the increase of reaction temperature, the concentration of NO2 - product gradually increases, while the concentration of NO3 - first increases and then decreases. At the same time, with the improvement of catalytic activity, the gas production gradually increases. In the gas phase products, N2O and NO are the main components, accounting for about 95%, and the rest 5% is N2 and NO2, indicating that the reaction path is mainly inclined to generate nitrogen-containing oxides.

[0047] Application Example 4 The catalyst prepared in Example 9 was used for HAN reaction. The HAN decomposition was carried out in a glass batch reactor, and 0.55 mg of catalyst was used for each test; 11 g of 1 wt% HAN solution was reacted at different temperatures (20, 30, 50, 70, 90 °C) for 1 h, and the reaction was terminated by cooling the reactor with cold water. The specific catalytic reaction results and gas composition are shown in Table 4.

[0048] Table 4 Catalytic reaction results and gas composition of 5% Ru / C catalyst

[0049] According to the data in Table 4, under the condition of normal pressure and low temperature, the catalyst prepared in Example 9 has lower catalytic activity than the catalyst prepared in Example 6 in the HAN reaction, but both of them show high selectivity to NH4 + and H + O, and the selectivity increases with the increase of catalytic activity. With the increase of reaction temperature, the concentration of NO2 - product gradually increases, while the concentration of NO3 - product first increases and then decreases. At the same time, with the increase of catalytic activity, the gas production gradually increases. The gas phase product is only composed of N2O and NO, indicating that the reaction path mainly tends to generate nitrogen-containing oxides.

[0050] Application Example 5 The catalyst of Example 6 was used for HAN reaction. The HAN decomposition was carried out in a glass batch reactor, and 0.55 mg of catalyst was used for each test; different concentrations of HAN solution (the amount of substrate was constant, i.e. 0.1%, 1%, 10%, 20%, 30%) were reacted at 90 °C for 1 h, and the reaction was terminated by cooling the reactor with cold water. The catalytic performance of 5% Rh / C catalyst on different concentrations of hydroxylamine nitrate aqueous solution is shown in Table 5.

[0051] Table 5 Catalytic performance of 5% Rh / C catalyst on different concentrations of hydroxylamine nitrate aqueous solution

[0052] As can be seen from Table 5, with the increase of HAN concentration, the catalytic reaction activity is higher, and with the increase of concentration, the gas production also increases, and the high selectivity to N2O and N2 does not change the gas-liquid phase path with the increase of concentration.

[0053] Application Example 6: Example 7 Catalyst will be used for HAN reaction. HAN decomposition is carried out in a glass batch reactor, 0.55 mg of catalyst is used for each test; different concentrations of HAN solution (the amount of substrate is constant, i.e. 0.1%, 1%, 10%, 20%, 30%) are reacted at 90°C for 1h, after which the reaction is terminated by cooling the reactor with cold water, the catalytic performance of 5% Pd / C catalyst for different concentrations of aqueous hydroxylamine nitrate solution is shown in Table 6.

[0054] Table 6 Catalytic performance of 5% Pd / C catalyst for different concentrations of aqueous hydroxylamine nitrate solution

[0055] As can be seen from Table 6, as the concentration of HAN increases, the catalytic reaction activity is higher, and as the concentration increases, the gas production also increases, and the main component of the generated gas is N2O, accounting for about 80% of the total gas, the rest is NO, NO2 and N2, indicating that the reaction path is more inclined to generate nitrogen-containing oxidation products under the action of the catalyst, and will not change with the increase of concentration.

[0056] Application Example 7: Example 8 Catalyst will be used for HAN reaction. HAN decomposition is carried out in a glass batch reactor, 0.55 mg of catalyst is used for each test; different concentrations of HAN solution (the amount of substrate is constant, i.e. 0.1%, 1%, 10%, 20%, 30%) are reacted at 90°C for 1h, after which the reaction is terminated by cooling the reactor with cold water, the catalytic performance of 5% Pt / C catalyst for different concentrations of aqueous hydroxylamine nitrate solution is shown in Table 7.

[0057] Table 7 Catalytic performance of 5% Pt / C catalyst for different concentrations of aqueous hydroxylamine nitrate solution

[0058] As can be seen from Table 7, as the concentration of HAN increases, the catalytic reaction activity is higher, and as the concentration increases, the gas production also increases, and in the gas phase product, N2O and NO are the main components, accounting for about 95%, and the remaining 5% is N2 and NO2, indicating that the reaction path is mainly inclined to generate nitrogen-containing oxides.

[0059] Application Example 8: Example 9 Catalyst will be used for HAN reaction. HAN decomposition is carried out in a glass batch reactor, 0.55 mg of catalyst is used for each test; different concentrations of HAN solution (the amount of substrate is constant, i.e. 0.1%, 1%, 10%, 20%, 30%) are reacted at 90°C for 1h, after which the reaction is terminated by cooling the reactor with cold water, the catalytic performance of 5% Ru / C catalyst for different concentrations of aqueous hydroxylamine nitrate solution is shown in Table 8.

[0060] Table 8 Catalytic performance of 5% Ru / C catalyst for different concentrations of aqueous hydroxylamine nitrate

[0061] As can be seen from Table 8, as the concentration of HAN increases, the catalytic activity is higher, and as the concentration increases, the gas production also increases. The gas phase products are only composed of N2O and NO, indicating that the reaction path is mainly inclined to generate nitrogen-containing oxides.

[0062] Application Example 9: The catalyst of Example 6 will be used for HAN reaction. HAN decomposition is carried out in a glass batch reactor at different ratios of supported carbon-based catalyst and substrate hydroxylamine nitrate (i.e. the mass ratio of Rh / C catalyst to substrate hydroxylamine nitrate is 1:100, 1:10, 1:5, 1:1, 10:1, 100:1); 11 g of 1 wt% HAN solution is reacted at a temperature of 90°C for 1 h, and the reaction is terminated by cooling the reactor with cold water. The catalytic performance of 5% Rh / C catalyst for different concentrations of aqueous hydroxylamine nitrate is shown in Table 9.

[0063] Table 9 Catalytic performance of 5% Rh / C catalyst and substrate hydroxylamine nitrate at different mass ratios

[0064] As can be seen from Table 9, by adjusting the mass ratio of catalyst to substrate hydroxylamine nitrate, it can be seen that the greater the amount of catalyst, the better the catalytic activity, and the greater the gas production, which is only composed of N2O and N2.

[0065] Application Example 10: The catalyst of Example 7 will be used for HAN reaction. HAN decomposition is carried out in a glass batch reactor at different ratios of supported carbon-based catalyst and substrate hydroxylamine nitrate (i.e. the mass ratio of Pd / C catalyst to substrate hydroxylamine nitrate is 1:100, 1:10, 1:5, 1:1, 10:1, 100:1); 11 g of 1 wt% HAN solution is reacted at a temperature of 90°C for 1 h, and the reaction is terminated by cooling the reactor with cold water. The catalytic performance of 5% Pd / C catalyst and substrate hydroxylamine nitrate at different mass ratios is shown in Table 10.

[0066] Table 10 Catalytic performance of 5% Pd / C catalyst and substrate hydroxylamine nitrate at different mass ratios

[0067] As can be seen from Table 10, by adjusting the mass ratio of catalyst to substrate hydroxylamine nitrate, it can be seen that the greater the amount of catalyst, the better the catalytic activity, and the greater the gas production, which is composed of N2O, NO, NO2 and N2.

[0068] Example 11: Example 8 catalyst will be used for HAN reaction. HAN decomposition is carried out in a glass batch reactor at different ratios of supported carbon-based catalyst and substrate hydroxylamine nitrate (i.e. mass ratio of Pt / C catalyst to substrate hydroxylamine nitrate is 1:100, 1:10, 1:5, 1:1, 10:1, 100:1); 11 g of 1 wt% HAN solution is reacted for 1 h at a temperature of 90°C, after which the reaction is terminated by cooling the reactor with cold water, the catalytic performance of 5% Pt / C catalyst and substrate hydroxylamine nitrate at different mass ratios is shown in Table 11.

[0069] Table 11 Catalytic performance of 5% Pt / C catalyst and substrate hydroxylamine nitrate at different mass ratios

[0070] From Table 11, by adjusting the mass ratio of catalyst to substrate hydroxylamine nitrate, it can be seen that the greater the amount of catalyst, the better the catalytic activity, and the greater the gas production, which is composed of N2O, NO, NO2 and N2 four gases.

[0071] Example 12: Example 9 catalyst will be used for HAN reaction. HAN decomposition is carried out in a glass batch reactor at different ratios of supported carbon-based catalyst and substrate hydroxylamine nitrate (i.e. mass ratio of Ru / C catalyst to substrate hydroxylamine nitrate is 1:100, 1:10, 1:5, 1:1, 10:1, 100:1); 11 g of 1 wt% HAN solution is reacted for 1 h at a temperature of 90°C, after which the reaction is terminated by cooling the reactor with cold water, the catalytic performance of 5% Ru / C catalyst and substrate hydroxylamine nitrate at different mass ratios is shown in Table 12.

[0072] Table 12 Catalytic performance of 5% Ru / C catalyst and substrate hydroxylamine nitrate at different mass ratios

[0073] From Table 12, by adjusting the mass ratio of catalyst to substrate hydroxylamine nitrate, it can be seen that the greater the amount of catalyst, the better the catalytic activity, and the greater the gas production, which is composed of N2O and NO.

[0074] Example 13: The catalyst prepared in Example 6 was used for the decomposition of hydroxylamine nitrate. The reaction was carried out in a glass batch reactor at a temperature of 90 °C, using 11 g of a 1 wt% aqueous solution of HAN as substrate and 55 mg of catalyst. Samples were taken at different reaction times (i.e. 1 min, 10 min, 30 min, 1 h, 2 h, 4 h) and the reaction was then terminated by cooling the reactor with cold water. The catalytic performance of the 5% Rh / C catalyst at different reaction times is shown in Table 13.

[0075] Table 13 Catalytic performance of the 5% Rh / C catalyst at different reaction times

[0076] As can be seen from Table 13, the catalytic activity and the amount of gas produced increase with increasing reaction time. The gaseous products consist of N2O and N2.

[0077] Application Example 14: The catalyst prepared in Example 7 was used for the decomposition of hydroxylamine nitrate. The reaction was carried out in a glass batch reactor at a temperature of 90 °C, using 11 g of a 1 wt% aqueous solution of HAN as substrate and 55 mg of catalyst. Samples were taken at different reaction times (i.e. 1 min, 10 min, 30 min, 1 h, 2 h, 4 h) and the reaction was then terminated by cooling the reactor with cold water. The catalytic performance of the 5% Pd / C catalyst at different reaction times is shown in Table 14.

[0078] Table 14 Catalytic performance of the 5% Pd / C catalyst at different reaction times

[0079] As can be seen from Table 14, the catalytic activity and the amount of gas produced increase with increasing reaction time. The gaseous products consist of N2O, NO, NO2 and N2.

[0080] Application Example 15: The catalyst prepared in Example 8 was used for the decomposition of hydroxylamine nitrate. The reaction was carried out in a glass batch reactor at a temperature of 90 °C, using 11 g of a 1 wt% aqueous solution of HAN as substrate and 55 mg of catalyst. Samples were taken at different reaction times (i.e. 1 min, 10 min, 30 min, 1 h, 2 h, 4 h) and the reaction was then terminated by cooling the reactor with cold water. The catalytic performance of the 5% Pt / C catalyst at different reaction times is shown in Table 15.

[0081] Table 15 Catalytic performance of the 5% Pt / C catalyst at different reaction times

[0082] As shown in Table 15, the catalytic activity is better and the gas production is greater with the increase of reaction time, and the gas phase product is composed of N2O, NO, NO2 and N2.

[0083] Application Example 16 The catalyst prepared in Example 9 was used for the decomposition reaction of hydroxylamine nitrate. The reaction was carried out in a glass material batch reactor, the reaction temperature was 90°C, the substrate was 11 g of 1 wt% HAN aqueous solution, and the catalyst dosage was 55 mg. Sampling analysis was carried out at different reaction time points (i.e. 1 min, 10 min, 30 min, 1 h, 2 h, 4 h), and then the reactor was cooled with cold water to terminate the reaction. The catalytic performance of 5% Ru / C catalyst at different reaction times is shown in Table 16.

[0084] Table 16 Catalytic performance of 5% Ru / C catalyst at different reaction times

[0085] As shown in Table 16, the catalytic activity is better and the gas production is greater with the increase of reaction time, and the gas phase product is composed of N2O, NO, NO2 and N2.

[0086] Application Example 17 The catalyst prepared in Example 6 was used for the decomposition reaction of hydroxylamine nitrate. The reaction was carried out in a fixed bed, the reaction temperature was 90°C, the substrate was 1 wt% HAN aqueous solution, and the reaction was carried out at different mass space velocities WHSV (i.e. mass space velocity was 0.1 h -1 , 1 h -1 , 10 h -1 , 20 h -1 , 50 h -1 , 100 h -1 ). According to the mass ratio of the catalyst and the hydroxylamine nitrate substrate in the kettle reactor was 1:2, when WHSV = 0.1 h -1 , the sampling time was 1 h, the feed flow rate was 0.17 ml / min, and the catalyst dosage was 1 g; when WHSV = 1 h -1 , the sampling time was 1 h, the feed flow rate was 1.67 ml / min, and the catalyst dosage was 1 g; when WHSV = 10 h -1 , the sampling time was 1 h, the feed flow rate was 16.7 ml / min, and the catalyst dosage was 1 g; when WHSV = 20 h -1At that time, the sampling time was 1 hour, the feed flow rate was 16.7 ml / min, and the catalyst dosage was 0.5 g; when WHSV = 50 h -1 At that time, the sampling time was 1 hour, the feed flow rate was 16.7 ml / min, and the catalyst dosage was 0.2 g; when WHSV = 100 h -1 At the same time, the sampling time was 1 hour, the feed flow rate was 16.7 ml / min, and the catalyst dosage was 0.1 g. The catalytic performance of the 5% Rh / C catalyst at different mass hourly space velocities is shown in Table 17.

[0087] Table 17 Catalytic performance of 5% Rh / C catalyst at different mass space velocities

[0088] As shown in Table 17, with the increase of mass hourly space velocity, the catalytic activity and gas production first increase and then decrease. The gas composition is the same as that of the batch reactor, consisting only of N2O and N2.

[0089] Application Example 18: The catalyst prepared in Example 7 was used in the decomposition reaction of hydroxylamine nitrate. The reaction was carried out in a fixed bed at a temperature of 90°C, using a 1 wt% HAN aqueous solution as the substrate, and at different mass hourly space velocities (WHSVs) (i.e., WHSV of 0.1 h⁻¹). -1 1h -1 10h -1 20h -1 50h -1 100h -1 The ratio of catalyst to hydroxylamine nitrate substrate in the batch reactor is adjusted according to a mass ratio of 1:2. When WHSV = 0.1 h -1 At that time, the sampling time was 1 hour, the feed flow rate was 0.17 ml / min, and the catalyst dosage was 1 g; when WHSV = 1 h -1 At that time, the sampling time was 1 hour, the feed flow rate was 1.67 ml / min, and the catalyst dosage was 1 g; when WHSV = 10 h -1 At that time, the sampling time was 1 hour, the feed flow rate was 16.7 ml / min, and the catalyst dosage was 1 g; when WHSV = 20 h -1 At that time, the sampling time was 1 hour, the feed flow rate was 16.7 ml / min, and the catalyst dosage was 0.5 g; when WHSV = 50 h -1 At that time, the sampling time was 1 hour, the feed flow rate was 16.7 ml / min, and the catalyst dosage was 0.2 g; when WHSV = 100 h -1The catalytic performance of the 5% Pd / C catalyst at different mass space velocities is shown in Table 18.

[0090] Table 18 Catalytic performance of 5% Pd / C catalyst at different mass space velocities

[0091] As can be seen from Table 18, with the increase of the mass space velocity, the catalytic activity and the gas production first increase and then decrease, the gas components are consistent with those of the tank reactor, and are composed of N2O, NO, NO2and N2.

[0092] Application Example 19 The catalyst prepared in Example 8 was used for the decomposition reaction of hydroxylamine nitrate. The reaction was carried out in a fixed bed, the reaction temperature was 90°C, the substrate was 1 wt% HAN aqueous solution, and the reaction was carried out at different mass space velocities WHSV (i.e. the mass space velocities were 0.1 h -1 , 1 h -1 , 10 h -1 , 20 h -1 , 50 h -1 , 100 h -1 ), and the mass ratio of the tank reactor catalyst to the hydroxylamine nitrate substrate was adjusted to be 1:2, when WHSV = 0.1 h -1 , the sampling time was 1 h, the feed flow rate was 0.17 ml / min, and the catalyst amount was 1 g; when WHSV = 1 h -1 , the sampling time was 1 h, the feed flow rate was 1.67 ml / min, and the catalyst amount was 1 g; when WHSV = 10 h -1 , the sampling time was 1 h, the feed flow rate was 16.7 ml / min, and the catalyst amount was 1 g; when WHSV = 20 h -1 , the sampling time was 1 h, the feed flow rate was 16.7 ml / min, and the catalyst amount was 0.5 g; when WHSV = 50 h -1 , the sampling time was 1 h, the feed flow rate was 16.7 ml / min, and the catalyst amount was 0.2 g; and when WHSV = 100 h -1 , the sampling time was 1 h, the feed flow rate was 16.7 ml / min, and the catalyst amount was 0.1 g, the catalytic performance of the 5% Pt / C catalyst at different mass space velocities is shown in Table 19.

[0093] Table 19 Catalytic performance of 5% Pt / C catalyst at different mass space velocities

[0094] As can be seen from Table 19, with the increase of mass space velocity, the catalytic activity and gas production first increase and then decrease, and the gas components are consistent with those of the tank reactor, which are composed of N2O, NO, NO2and N2.

[0095] Application Example 20 The catalyst prepared in Example 9 was used for the decomposition reaction of hydroxylamine nitrate. The reaction was carried out in a fixed bed, the reaction temperature was 90°C, the substrate was 1 wt% HAN aqueous solution, and the reaction was carried out at different mass space velocities WHSV (i.e. mass space velocities were 0.1 h -1 , 1 h -1 , 10 h -1 , 20 h -1 , 50 h -1 , 100 h -1 ), and the amount of catalyst and hydroxylamine nitrate substrate was adjusted according to the mass ratio of 1:2. When WHSV = 0.1 h -1 , the sampling time was 1 h, the feeding amount flow rate was 0.17 ml / min, and the catalyst amount was 1 g; when WHSV = 1 h -1 , the sampling time was 1 h, the feeding amount flow rate was 1.67 ml / min, and the catalyst amount was 1 g; when WHSV = 10 h -1 , the sampling time was 1 h, the feeding amount flow rate was 16.7 ml / min, and the catalyst amount was 1 g; when WHSV = 20 h -1 , the sampling time was 1 h, the feeding amount flow rate was 16.7 ml / min, and the catalyst amount was 0.5 g; when WHSV = 50 h -1 , the sampling time was 1 h, the feeding amount flow rate was 16.7 ml / min, and the catalyst amount was 0.2 g; and when WHSV = 100 h -1 , the sampling time was 1 h, the feeding amount flow rate was 16.7 ml / min, and the catalyst amount was 0.1 g. The catalytic performance of the 5% Ru / C catalyst at different mass space velocities is shown in Table 20.

[0096] Table 20 Catalytic performance of 5% Ru / C catalyst at different mass space velocities

[0097] As can be seen from Table 20, with the increase of mass space velocity, the catalytic activity and gas production first increase and then decrease, and the gas components are consistent with those of the tank reactor, which are composed of N2O and NO.

[0098] Application Example 21 The cycle stability of the catalyst of Example 6 for the decomposition reaction of HAN was carried out in a glass batch reactor, and 0.55 mg of the catalyst was used in each test; 11 g of 1 wt% HAN solution was reacted at 90°C for 1 h, and the reaction was terminated by cooling the reactor with cold water. The cycle stability results of the 5% Rh / C catalyst are shown in Table 21.

[0099] Table 21 Cycle stability of 5% Rh / C catalyst

[0100] As can be seen from Table 21, after 5 cycles of catalysis, the catalytic activity, gas production and gas phase product composition of the catalyst prepared in Example 6 for the decomposition of HAN are basically the same as those in the initial state, indicating that the catalyst has good cycle stability. This characteristic provides strong support for its practical application in the later stage.

[0101] Application Example 22: The cycle stability of the catalyst of Example 7 for the decomposition reaction of HAN was carried out in a glass batch reactor, and 0.55 mg of the catalyst was used in each test; 11 g of 1 wt% HAN solution was reacted at 90°C for 1 h, and the reaction was terminated by cooling the reactor with cold water. The cycle stability results of the 5% Pd / C catalyst are shown in Table 22.

[0102] Table 22 Cycle stability of 5% Pd / C catalyst

[0103] As can be seen from Table 22, after 5 cycles of catalysis, the catalytic activity, gas production and gas phase product composition of the catalyst prepared in Example 7 for the decomposition of HAN are basically the same as those in the initial state, indicating that the catalyst has good cycle stability. This characteristic provides strong support for its practical application in the later stage.

[0104] Application Example 23: The cycle stability of the catalyst of Example 8 for the decomposition reaction of HAN was carried out in a glass batch reactor, and 0.55 mg of the catalyst was used in each test; 11 g of 1 wt% HAN solution was reacted at 90°C for 1 h, and the reaction was terminated by cooling the reactor with cold water. The cycle stability results of the 5% Pt / C catalyst are shown in Table 23.

[0105] Table 23 Cycle stability of 5% Pt / C catalyst

[0106] From Table 23, it can be seen that the catalyst prepared in Example 8 has good cycle stability, as its catalytic activity, gas production and gas composition are basically the same as those in the initial state after 5 cycles of catalytic reaction. This feature provides strong support for its practical application in the later stage.

[0107] Example 24: The cycle stability of the catalyst of Example 9 for the HAN decomposition reaction was tested in a glass batch reactor, and 0.55 mg of catalyst was used each time; 11 g of 1 wt% HAN solution was reacted at 90°C for 1 h, and the reaction was terminated by cooling the reactor with cold water. The cycle stability of the 5% Ru / C catalyst is shown in Table 24.

[0108] Table 24 Cycle stability of 5% Ru / C catalyst

[0109] From Table 24, it can be seen that the catalyst prepared in Example 9 has good cycle stability, as its catalytic activity, gas production and gas composition are basically the same as those in the initial state after 5 cycles of catalytic reaction. This feature provides strong support for its practical application in the later stage.

[0110] Comparative Example 1: The 30% Ir / Al2O3 catalyst was provided by the Catalysis and New Materials Research Room of the Dalian Institute of Chemical Physics, Chinese Academy of Sciences. The 30% Ir / Al2O3 catalyst was used for the HAN reaction. The reaction was carried out in a glass batch reactor, and 0.55 mg of catalyst was used each time; 11 g of 1 wt% HAN solution was reacted at 90°C for 1 h, and the reaction was terminated by cooling the reactor with cold water. The catalytic activity data and gas composition ratio are shown in Table 23. Figure 4

[0111] The catalytic decomposition products of Examples 6, 7, 8, 9 and Comparative Example 1 were qualitatively and quantitatively analyzed by the MID and MCD detection methods, and the results are shown in Table 49, Qualitative and quantitative analysis results of the catalytic decomposition products of Examples 6-9 and Comparative Example 1

[0112] It can be seen that the series of catalysts prepared exhibit high nitrogen oxide selectivity in the HAN catalytic decomposition reaction.

[0113] The NH3OH + of Examples 6, 7, 8, 9 and Comparative Example 1 were detected by the NH3OH + ​The consumption of NH4+ and H+ was calculated and used to evaluate the catalytic activity of each catalyst: Example 6 (Rh / C) had the highest catalytic activity of 69%; Example 7 (Pd / C) had the lowest catalytic activity of 24%; Example 8 (Pt / C) had a catalytic activity of 64%; Example 9 (Ru / C) had a catalytic activity of 34%; and, notably, Examples 6 and 8 both had higher catalytic activity than Comparative Example 1 (Ir / Al2O3), which had a catalytic activity of 51%.

[0114] The amount of NO2- and NO3- produced by Examples 6, 7, 8, 9 and Comparative Example 1 was calculated using the detection method of NO2- + and H + The detection method for NH4 + and H + After calculation, it was found that Example 6 (Rh / C) performed best in terms of the yield of H + , with a yield of H + of 56%; Example 7 (Pd / C) had the lowest yield of H + , with a yield of H + of 17%; Example 8 (Pt / C) performed best in terms of the yield of NH4 + , with a yield of NH4 + of 59%; and Example 9 (Ru / C) had the lowest yield of NH4 + , with a yield of 9.8%.

[0115] Overall, the selectivity trends for NH4 + and H + were consistent with the catalytic activity, in that the higher the catalytic efficiency of the catalyst, the stronger the selectivity of the catalyst for NH4 + and H + .

[0116] The amount of NO2- and NO3- produced by Examples 6, 7, 8, 9 and Comparative Example 1 was calculated using the detection method of NO2- - and NO3 - It was found that Example 6 (Rh / C) had the strongest catalytic activity, with the lowest amount of NO2 - in the system; Examples 7 (Pd / C) and 9 (Ru / C) had the weakest catalytic activity, with the highest amount of NO2 - ; and the consumption of NO3 - varied little between the different catalysts, with no obvious pattern.

[0117] In summary, the low-loading noble metal carbon-based catalysts (Pd / C, Ru / C, Pt / C, Rh / C) prepared in the present application exhibited high catalytic activity in the HAN decomposition reaction, and had good cycle stability, with no significant decrease in catalytic activity after 5 cycles. In addition, the liquid-phase products NH4+ and H + showed higher selectivity. The gas production gradually increased with the progress of the catalytic reaction, and the more complete the reaction, the higher the gas production. And the higher the HAN substrate concentration, the higher the catalytic activity. The composition of the gas phase products is simpler than that reported conventionally, mainly consisting of one or more of N2O, NO, NO2 and N2. Among them, the gas phase products of Rh / C catalyst are only N2O and N2, while Ru / C mainly generates N2O and NO, indicating that its reaction path is more specific. The above characteristics show that this type of catalyst has good application potential in the field of space propulsion catalysts.

[0118] The above is only a few embodiments of the present application, and does not limit the present application in any form. Although the preferred embodiments are disclosed above, they are not intended to limit the present application. Any skilled person in the art can make some changes or modifications to the above disclosed technical content without departing from the scope of the technical solution of the present application, which are equivalent to equivalent embodiments, and are within the scope of the technical solution.

Claims

1. A supported carbon-based catalyst, characterized in that, The loading of the metal element in the supported carbon-based catalyst is 0.1-15 wt%; The metal element is selected from one of Pt, Ru, Rh, Pd; The carrier of the supported carbon-based catalyst is coconut shell activated carbon; The supported carbon-based catalyst is selected from at least one of Pt / C, Ru / C, Rh / C, Pd / C.

2. The method for preparing a supported carbon-based catalyst according to claim 1, characterized in that, The metal salt solution is used to impregnate the coconut shell activated carbon in equal volume to obtain carbon-based catalysts with different loadings, which are stirred, left to stand for 4-24 h, dried at 80-120℃ for 6-24 h, reduced, and passivated to obtain the supported carbon-based catalysts; The concentration of the metal salt solution is 0.1-10 wt.%; The metal salt is selected from one of rhodium acetate, rhodium nitrate, rhodium chloride, palladium acetate, palladium nitrate, palladium chloride, platinum acetate, platinum nitrate, platinum chloride, ruthenium acetate, ruthenium nitrate, and ruthenium chloride.

3. The preparation method according to claim 2, characterized in that, The reduction specifically comprises: placing the dried catalyst in a tube furnace and heating at a rate of 2-5℃ / min to 200-400℃ for 1-4 h; the reducing atmosphere is H2 / Ar mixed gas, in which the volume ratio of H2 is 10-15%.

4. The preparation method according to claim 2, characterized in that, The passivation specifically comprises: placing the reduced catalyst in an air / Ar atmosphere, in which the volume ratio of air is 2-3%, and passivating for 8-24 h to obtain the supported carbon-based catalyst.

5. Use of the supported carbon-based catalyst according to claim 1 and / or obtained by the process according to any one of claims 2-4 in the decomposition reaction of hydroxylamine nitrate, characterized in that, The supported carbon-based catalyst is used to catalyze the decomposition of a hydroxylamine nitrate solution to obtain liquid and gaseous products; said liquid phase product is selected from at least one of NH4 + , H + , NO3 - , NO2 - ; The gaseous product is selected from at least one of N2O, N2, NO, and NO2.

6. Use according to claim 5, characterized in that, The mass ratio of the supported carbon-based catalyst to the hydroxylamine nitrate solution is 1:100-100:

1.

7. Use according to claim 5, characterized in that, The decomposition of the hydroxylamine nitrate is specifically: using a tank reactor or a fixed bed reactor to decompose the hydroxylamine nitrate solution, reacting at 20-100°C for 1 min-4h, mass space velocity WHSV is 0.1-100h -1 .

8. Use according to claim 5, characterized in that, The concentration of the hydroxylamine nitrate solution is 0.1-30 wt.%; Preferably, the concentration of the hydroxylamine nitrate solution is 0.1-10 wt.%.

9. Use according to claim 5, characterized in that, When the supported carbon-based catalyst is Ru / C, the gaseous product is N2O and NO; When the supported carbon-based catalyst is Rh / C, the gaseous product is N2O and N2; When the supported carbon-based catalyst is Pt / C and / or Pd / C, the gaseous product is N2O, N2, NO, and NO2. The liquid phase products are NH4 + , H + , NO3 - and NO2 - when the supported carbon-based catalyst is Pt / C, Ru / C, Rh / C, Pd / C.

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