A synthesis method of Ni-Mg@FER molecular sieve catalyst for catalytic conversion of CO2, CH4, and N2O multi-element greenhouse gases

Abstract

A method for synthesizing a Ni-Mg@FER molecular sieve catalyst for the catalytic conversion of multiple greenhouse gases (CO2, CH4, and N2O) belongs to the field of multiple greenhouse gas combustion catalysts. The catalyst of the present invention uses H-FER as a carrier, loaded with Ni and Mg as the active components of the catalyst. The present invention uses a solid-phase exchange method to load nickel and magnesium onto H-FER. Studies have shown that under reaction conditions of a space velocity of 12,000 h / min, the nickel and magnesium can be loaded onto H-FER. ‑1 , CO2:CH4:N2O:He = 10%:12%:3.6%:74.4%, and a total gas flow rate of 120ml / min. The catalyst of the present invention has good catalytic activity and thermal stability, a simple process, and low cost. At 750°C, the conversion rates of N2O, CH4, and CO2 reached 100%, 89.5%, and 92.1%, respectively.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalytic conversion and utilization of multiple greenhouse gases including CO2, methane and nitrous oxide, and in particular relates to a method for preparing a Ni-Mg@FER molecular sieve catalyst for the synergistic catalytic combustion of agricultural and animal husbandry waste gases including CO2, N2O and CH4. Background Art

[0002] With the rapid development of the global economy, greenhouse gas emissions are increasing. According to data released by the United Nations Environment Programme, greenhouse gas concentrations have increased by approximately 40% since the Industrial Revolution. Therefore, the development of greenhouse gas conversion and utilization technologies has important research significance and practical value in supporting my country's "dual carbon" national policy. Carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) are three major greenhouse gases, widely derived from industry, agriculture, animal husbandry, and lake / wetland aquatic ecosystems. Agriculture and animal husbandry have been confirmed by numerous scholars to be significant sources of CO2, CH4, and N2O in the atmosphere. With the increasing demand for livestock products and the continuous improvement of intensive large-scale farming, emissions are expected to increase further, with a significant greenhouse effect.

[0003] CO2 is the main component of greenhouse gases. The greenhouse effect caused by excessive emissions into the atmosphere will trigger a series of environmental problems, such as intensified heat waves, coral bleaching, increased floods, and frequent extreme weather. There are currently two main ways to deal with CO2: burying the captured CO2 or converting it into solid carbonates for storage, and using CO2 as a reactant to convert it into high-value-added chemical products through electrocatalytic reduction, photocatalytic reduction, and thermal catalytic reduction. The CH4-CO2 dry reforming reaction (DRM) has been favored by researchers since its discovery. On the one hand, this is because the reaction can simultaneously utilize CH4 and CO2, two greenhouse gases, and convert them into synthesis gas. On the other hand, the product H2 / CO ratio of the reaction is 1, which can be directly used as the feed gas for FT synthesis to produce liquid hydrocarbon compounds. However, the DRM reaction is a highly endothermic reaction thermodynamically (ΔH 298K =247kJ / mol), requiring relatively high temperatures. Researchers exploring reaction conditions and conducting thermodynamic simulations have found that the DRM reaction requires temperatures above 850°C to achieve high CH4 and CO2 conversion rates. High temperatures require catalysts with excellent thermal stability and place stringent demands on equipment. While significant progress has been made in research on methane-to-carbon dioxide reforming, the problems of sintering of active catalyst components and surface carbon accumulation remain unresolved.

[0004] Methane is the main component of natural gas and biogas. It is an energy gas, but it is also a greenhouse gas that seriously pollutes the environment. Its greenhouse effect is 23 times that of carbon dioxide and its ability to damage the ozone layer is 7 times that of carbon dioxide. The traditional method of burning methane directly in the air will cause the nitrogen in the air to react with oxygen to produce NO at a high temperature of more than 1000℃. x , polluting the environment. Currently, the main catalysts for methane catalytic combustion are: (1) transition metal oxide catalysts, such as NiO, Mn2O3, CuO and Fe2O3; (2) supported noble metal catalysts, including Rh, Pd and Pt; (3) rare earth perovskite-type composite metal oxide catalysts; (4) hexaaluminate-type catalysts. Among them, noble metal catalysts have the best low-temperature catalytic activity and anti-poisoning ability for methane combustion, but have the disadvantages of poor hydrothermal stability and high cost. In recent years, Ni-based catalysts have been widely studied due to their low cost and DRM activity comparable to that of noble metals.

[0005] Nitrous oxide (N2O), also known as "laughing gas", has a strong ability to absorb infrared radiation. Its warming effect is 310 times that of CO2 and 21 times that of CH4. N2O is difficult to self-degrade in nature and can exist in the atmosphere for 114 years. x It is a precursor of nitrous oxide and has a strong destructive effect on the ozone layer. At present, the decomposition methods of N2O mainly include high-temperature decomposition, selective catalytic decomposition, direct catalytic decomposition and other methods. However, N2O is a very promising oxidant, and compared with other oxidants reported in the literature for DMTM (O, H2O2, CO2), nitrous oxide as an oxidant can react with copper or iron zeolite molecular sieves to produce more active α-O. Moreover, compared with O2 and H2O, N2O oxidizes methane and releases a single oxygen atom, avoiding the over-oxidation of CH3OH and helping to improve the selectivity of CH3OH. Because of these advantages, some scholars have studied the oxidation of methane to methanol by nitrous oxide, but this reaction system has not yet been well established.

[0006] With the continuous increase in greenhouse gas emissions from industries (such as petrochemicals, electricity, steel, cement, etc.), agriculture (soil microbial metabolism, organic matter decomposition, nitrification, denitrification processes), animal husbandry (animal intestinal fermentation, manure treatment) and lake / wetland water ecology (microbial consumption, respiration), agriculture and animal husbandry have been confirmed to be important sources of CO2, CH4 and N2O in the atmosphere, and they together account for nearly 40% of the global greenhouse gas emissions.

[0007] In particular, livestock production contributes significantly to CH4 and N2O, two typical "non-carbon" greenhouse gases (with greenhouse gas potentials 21 times and 310 times greater than CO2, respectively), accounting for 37% and 65% of global CH4 and N2O emissions respectively. With the increasing demand for livestock products and the continued rise in intensive farming practices, emissions of these greenhouse gases are expected to increase further, with even more significant impacts on the global climate.

[0008] Therefore, in view of the intensive scale of livestock farming, we need to develop and promote effective greenhouse gas collection and treatment technologies to reduce the emission of these gases and thus alleviate the pressure of global warming.

[0009] Several patents have been reported for single and dual greenhouse gas treatment. For example, the patent "An Iridium-Supported Catalyst for Low-Concentration Methane Catalytic Combustion and Its Preparation Method" utilizes an Ir-TiO2 catalyst, improving its activity, stability, and durability. The patent "A Carbon Dioxide Methanation Catalyst and Its Preparation Method" utilizes a Ni-Mg-SiO2 catalyst to effectively catalyze the hydrogenation of carbon dioxide to methane under specific reaction conditions, achieving a maximum CO2 conversion rate exceeding 90% and a maximum CH4 selectivity of 99.9%. In previous research, we have also utilized catalysts such as Co3O4 and Fe-BEA for the low-temperature decomposition of nitrous oxide and the coordinated catalytic combustion of CH4 and N2O, respectively. The development of these technologies primarily focuses on single and dual greenhouse gas treatment and resource utilization, such as thermal / electrical / photoelectric CO2 hydrogenation reduction, CH4 catalytic combustion, direct N2O decomposition, CH4 dry reforming, and N2O selective reduction. These technologies are of great significance for improving greenhouse gas treatment efficiency and resource utilization. However, there has been no report on the relevant research on ternary greenhouse gases at home and abroad at this stage. Therefore, we propose a multi-element greenhouse gas conversion and utilization technology route of N2O selective catalytic reduction coupled with CH4 and CO2 dry reforming to achieve complementary advantages. Summary of the Invention

[0010] In light of the intensive scale of agriculture and animal husbandry, this invention provides a method for preparing and applying a Ni-Mg@FER molecular sieve catalyst for the coordinated collection and treatment of three greenhouse gases: CO2, CH4, and N2O. The material synthesized by this method not only offers the advantages of simple processing but also efficiently utilizes the multi-component (CO2 / CH4 / N2O) greenhouse gas for conversion and utilization, thus having strategic significance for greenhouse gas emission reduction and carbon recycling in my country.

[0011] The invention discloses a method for preparing a Ni-Mg@FER molecular sieve catalyst for the synergistic catalytic combustion of CO2, CH4 and N2O in agricultural and animal husbandry waste gases, characterized in that magnesium nitrate hexahydrate and nickel nitrate hexahydrate are selected as precursors, and Ni-Mg is loaded on the H-FER molecular sieve.

[0012] The mass of Ni accounts for 14% of the total mass of the final Ni-Mg@FER molecular sieve catalyst, and the mass of Mg accounts for 2-10% of the total mass of the final Ni-Mg@FER molecular sieve catalyst.

[0013] The prepared Ni-Mg@FER molecular sieve catalyst is used for the catalytic conversion of CO2, CH4 and N2O in agricultural and animal husbandry waste gas with a reaction space velocity of 12000h -1 The reaction temperature is 750°C, the volume proportion of carbon dioxide is 10%, the volume proportion of methane is 10% to 25%, the volume proportion of nitrous oxide is 0% to 30%, and the balance gas is helium.

[0014] The preparation method of the Ni-Mg@FER catalyst for the synergistic catalytic combustion of agricultural and animal husbandry waste gases CO2, CH4, and N2O is a solid phase exchange method, comprising the following steps:

[0015] (1) The H-FER molecular sieve was placed in a muffle furnace for calcination. The initial temperature of the muffle furnace was set to 30°C, and the temperature was increased by programming at 5°C / min to reach the final temperature of 550°C, and then maintained at 550°C for 6 hours;

[0016] (2) Mixed Calcination: H-FER molecular sieve was mixed with magnesium nitrate hexahydrate and nickel nitrate hexahydrate and calcined in a tube furnace under an ammonia atmosphere. The ammonia was introduced into the quartz tube by nitrogen bubbling. The initial temperature of the tube furnace was set to 25°C, and the heating rate was controlled by programming at 10°C / min to reach the set temperature of 550°C. The temperature was maintained at 550°C for 12 hours. The mass of Ni accounted for 14% of the total mass of the final Ni-Mg@FER molecular sieve catalyst, and the mass of Mg accounted for 2-10% of the total mass of the final Ni-Mg@FER molecular sieve catalyst.

[0017] (3) The solid product obtained in step (2) is tableted, crushed, and sieved to obtain a Ni-Mg@FER molecular sieve catalyst.

[0018] In the method of the present invention, the prepared Ni-Mg@FER molecular sieve catalyst is loaded into the constant temperature area of ​​the fixed bed micro quartz tube reactor. The reaction space velocity is 12000h -1 The feed ratio is 10% by volume of carbon dioxide, 10% to 25% by volume of methane, and 0% to 30% by volume of nitrous oxide, with helium as the balance gas. The gas after the reaction is fed into a gas chromatograph for product analysis.

[0019] The present invention provides the application of a catalyst for the coordinated catalytic combustion of CO2, N2O, and CH4:

[0020] The prepared Ni-Mg@FER catalyst was loaded into the constant temperature area of ​​a fixed-bed micro quartz tube reactor to carry out the reaction.

[0021] The present invention has the following advantages:

[0022] (1) This invention explores the multi-element greenhouse gas N2O-SCR-DRM coupled catalytic technology, which synergistically converts CO2, CH4, and N2O into synthesis gas (CO, H2) and N2, H2O, which is of great significance to the emission and utilization of greenhouse gases in my country.

[0023] (2) The preparation process of the present invention is simple, low-cost, and suitable for industrial production and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 When the feed ratio is CO2:CH4:N2O:He=10%:12%:3.6%:74.4%, the CO2 conversion rate is obtained when 14%Ni-2%Mg@FER, 14%Ni-5%Mg@FER, 14%Ni-7%Mg@FER and 14%Ni-10%Mg@FER catalysts are used for the synergistic catalytic conversion of CO2, CH4 and N2O.

[0025] Figure 2 When the feed ratio is CO2:CH4:N2O:He=10%:12%:3.6%:74.4%, the conversion rate of CH4 when 14%Ni-2%Mg@FER, 14%Ni-5%Mg@FER, 14%Ni-7%Mg@FER, and 14%Ni-10%Mg@FER catalysts are used for the synergistic catalytic conversion of CO2, CH4, and N2O.

[0026] Figure 3 The conversion rate of CO2 when the catalyst of Example 3 is used for catalytic conversion of CO2, CH4 and N2O in a variable volume ratio at 750°C.

[0027] Figure 4 The conversion rate of CH4 when the catalyst of Example 3 is used for catalytic conversion of CO2, CH4 and N2O in a variable volume ratio at 750°C.

[0028] Figure 5 Example 3 The catalyst was subjected to a stability test at 750°C with a feed ratio of CO2:CH4:N2O:He = 10%:12%:3.6%:74.4% for 30 hours to test the relationship between CO2 and time.

[0029] Figure 6 The catalyst of Example 3 was subjected to a stability test at 750° C. with a feed ratio of CO 2 : CH 4 : N 2 O: He = 10% : 12% : 3.6% : 74.4% for 30 hours to determine the relationship between CH 4 and time. DETAILED DESCRIPTION

[0030] The present invention will be further described below with reference to the embodiments, but the protection scope of the present invention is not limited to the scope shown in the embodiments.

[0031] Example 1: Preparation of 14% Ni-2% Mg@FER molecular sieve catalyst

[0032] H-FER was calcined in a muffle furnace with an initial temperature set at 30°C. The temperature was raised by programming at 5°C / min to a final temperature of 550°C after 104 minutes and maintained at 550°C for 6 hours. The calcined H-FER was ground and the amount of nickel nitrate hexahydrate and magnesium nitrate hexahydrate required for 14% Ni-2% Mg@FER was calculated. 0.69 g Ni(NO3)2·6H2O, 0.21 g Mg(NO3)2·6H2O and 1 g H-FER was stirred in a corundum boat for 20 minutes to thoroughly mix the Ni(NO3)2·6H2O, Mg(NO3)2·6H2O, and H-FER. The mixed sample was then placed in a quartz tube of a tube furnace. Ammonia was introduced into the tube by bubbling nitrogen for 4 hours at a nitrogen flow rate of 30 ml / min. After the purge, nitrogen and ammonia were continuously introduced. The initial temperature of the tube furnace was set at 25°C, and the temperature was ramped at a controlled rate of 10°C / min. After 52.5 minutes, the set temperature reached 550°C, where it was maintained for 12 hours. The prepared sample was pressed, crushed, and sieved to select a 40-60 mesh sample, resulting in a 14% Ni-2% Mg@FER sample for subsequent evaluation and testing. Ni ions accounted for 14% by mass of the modified molecular sieve, and Mg ions accounted for 2% by mass. The prepared molecular sieve catalyst was loaded into the constant temperature zone of a direct-flow tubular fixed-bed micro-quartz tube reactor. The fixed-bed reactor control panel was opened, the hydrogen-air generator was activated, and the gas chromatograph (GC) was started. The catalyst was pretreated with helium at 550°C and impurities were purged for 30 minutes, followed by cooling to 200°C. A mixture of N2O, CH4, CO2, and helium was introduced into the fixed-bed reactor at a rate of 120 ml / min. A catalytic reaction was carried out at a reaction temperature of 750°C and atmospheric pressure, wherein the CO2 content accounted for 10% of the total gas introduced, the CH4 content accounted for 12% of the total gas introduced, and the N2O content accounted for 3.6% of the total gas introduced, with the balance gas being helium. The resulting product was detected by gas chromatography for quantitative analysis.

[0033] Example 2: Preparation of 14% Ni-5% Mg@FER molecular sieve catalyst

[0034] H-FER was calcined in a muffle furnace with an initial temperature of 30°C. The temperature was raised by programming at 5°C / min to a final temperature of 550°C after 104 minutes and maintained at 550°C for 6 hours. The calcined H-FER was ground and the amount of nickel nitrate hexahydrate and magnesium nitrate hexahydrate required for 14% Ni-5% Mg@FER was calculated. 0.69 g Ni(NO3)2·6H2O, 0.52 g Mg(NO3)2·6H2O and 1 g H-FER was stirred in a corundum boat for 20 minutes to thoroughly mix Ni(NO3)2·6H2O, Mg(NO3)2·6H2O, and H-FER. The mixed sample was placed in a quartz tube of a tube furnace and ammonia was introduced into the tube by bubbling nitrogen for 4 hours at a nitrogen flow rate of 30 ml / min. After the purge was completed, nitrogen and ammonia were continuously introduced. The initial temperature of the tube furnace was set to 25°C, and the heating rate was controlled by a temperature program of 10°C / min. After 52.5 minutes, the set temperature reached 550°C and was maintained at 550°C for 12 hours. The prepared sample was pressed, crushed, and sieved to select a sample with a mesh size of 40-60. This yielded a 14% Ni-2% Mg@FER sample for subsequent evaluation and testing. The mass percentage of Ni ions in the modified molecular sieve was 14%, and the mass percentage of Mg ions in the modified molecular sieve was 5%. The activity evaluation method was the same as in Example 1.

[0035] Example 3: Preparation of 14% Ni-7% Mg@FER molecular sieve catalyst

[0036] H-FER was calcined in a muffle furnace with an initial temperature set at 30°C. The temperature was raised by programming at 5°C / min to a final temperature of 550°C after 104 minutes and maintained at 550°C for 6 hours. The calcined H-FER was ground and the amount of nickel nitrate hexahydrate and magnesium nitrate hexahydrate required for 14% Ni-7% Mg@FER was calculated. 0.69 g Ni(NO3)2·6H2O, 0.73 g Mg(NO3)2·6H2O and 1 g H-FER was stirred in a corundum boat for 20 minutes to thoroughly mix Ni(NO3)2·6H2O, Mg(NO3)2·6H2O, and H-FER. The mixed sample was placed in a quartz tube of a tube furnace and ammonia was introduced into the tube by bubbling nitrogen for 4 hours at a nitrogen flow rate of 30 ml / min. After the purge, nitrogen and ammonia were continuously introduced. The initial temperature of the tube furnace was set to 25°C, and the heating rate was controlled by a temperature program of 10°C / min. After 52.5 minutes, the set temperature reached 550°C and was maintained at 550°C for 12 hours. The prepared sample was pressed, crushed, and sieved to select a sample with a mesh size of 40-60. This yielded a 14% Ni-2% Mg@FER sample for subsequent evaluation and testing. The mass percentage of Ni ions in the modified molecular sieve was 14%, and the mass percentage of Mg ions in the modified molecular sieve was 7%. The activity evaluation method was the same as in Example 1.

[0037] Example 4: Preparation of 14% Ni-10% Mg@FER molecular sieve catalyst

[0038] H-FER was calcined in a muffle furnace with an initial temperature set at 30°C. The temperature was raised by programming at 5°C / min to a final temperature of 550°C after 104 minutes and maintained at 550°C for 6 hours. The calcined H-FER was ground and the amount of nickel nitrate hexahydrate and magnesium nitrate hexahydrate required for 14% Ni-10% Mg@FER was calculated. 0.69 g Ni(NO3)2·6H2O, 1.05 g Mg(NO3)2·6H2O and 1 g H-FER was stirred in a corundum boat for 20 minutes to thoroughly mix Ni(NO3)2·6H2O, Mg(NO3)2·6H2O, and H-FER. The mixed sample was placed in a quartz tube of a tube furnace and ammonia was introduced into the tube by bubbling nitrogen for 4 hours at a nitrogen flow rate of 30 ml / min. After the purge was completed, nitrogen and ammonia were continuously introduced. The initial temperature of the tube furnace was set to 25°C, and the heating rate was controlled by programming at 10°C / min. After 52.5 minutes, the set temperature reached 550°C and was maintained at 550°C for 12 hours. The prepared sample was pressed, crushed, and sieved to select samples with a mesh size of 40-60. This yielded a 14% Ni-2% Mg@FER sample for subsequent evaluation and testing. The mass percentage of Ni ions in the modified molecular sieve was 14%, and the mass percentage of Mg ions in the modified molecular sieve was 10%. The activity evaluation method was the same as in Example 1.

[0039] Depend on Figure 1 It can be seen that within 750°C, compared with several other samples, the 14%Ni-7%Mg@FER molecular sieve catalyst has the highest CO2 conversion rate, which can reach 92.3%.

[0040] Depend on Figure 2 It can be seen that within 750°C, compared with several other samples, the methane conversion rate of 14%Ni-7%Mg@FER molecular sieve catalyst is the highest, reaching 89.5%.

[0041] Depend on Figure 3 It can be seen that at 750°C, compared with several other gas volume ratios, the 14% Ni-7% Mg@FER molecular sieve catalyst has the highest CO2 conversion rate of 92.3% under the conditions of CO2:CH4:N2O:He=10%:12%:3.6%:74.4%.

[0042] Depend on Figure 4 It can be seen that at 750°C, compared with several other gas volume ratios, the 14% Ni-7% Mg@FER molecular sieve catalyst has the highest CH4 conversion rate of 89.5% under the conditions of CO2:CH4:N2O:He=10%:12%:3.6%:74.4%.

[0043] Depend on Figure 5 It can be seen that under 750℃, the 14%Ni-7%Mg@FER molecular sieve catalyst has good stability, the Ni-Mg particles are not easy to sinter, and the CO2 conversion rate only decreases by about 1.2% after 20 hours of testing.

[0044] Depend on Figure 6 It can be seen that under 750°C conditions, the 14% Ni-7% Mg@FER molecular sieve catalyst has good stability, the Ni-Mg particles are not easy to sinter, and the methane conversion rate only decreases by about 1.3% after 20 hours of testing.

Claims

1. A method for synthesizing a Ni-Mg@FER molecular sieve catalyst for catalytic conversion of multiple greenhouse gases including CO2, CH4, and N2O, characterized in that: Here are the steps: The H-FER molecular sieve was placed in a muffle furnace for calcination. The initial temperature of the muffle furnace was set at 30°C, and the temperature was increased by programming at 5°C / min to reach the final temperature of 550°C, and then maintained at 550°C for 6 hours. Mixed calcination: H-FER molecular sieve was mixed with nickel nitrate hexahydrate and magnesium nitrate hexahydrate and calcined in a tube furnace under an ammonia atmosphere. The ammonia was introduced into the quartz tube by nitrogen bubbling. The initial temperature of the tube furnace was set at 25°C, and the heating rate was controlled by programming at 10°C / min to reach the set temperature of 550°C. The temperature was maintained at 550°C for 12 hours. The weight of Ni accounted for 14% of the total weight of the final Ni-Mg@FER molecular sieve catalyst, and the weight of Mg accounted for 2-10% of the total weight of the final Ni-Mg@FER molecular sieve catalyst. The solid product obtained by mixing and calcining is pressed into tablets, crushed, and sieved to obtain a Ni-Mg@FER molecular sieve catalyst.

2. Application of the Ni-Mg@FER molecular sieve catalyst obtained by the method of claim 1 in a synergistic catalytic combustion system of agricultural and animal husbandry waste gases CO2, CH4 and N2O.

3. The use according to claim 2, characterized in that Livestock waste gas consists of CO2, CH4, and N2O. The volume ratios of CO2, CH4, and N2O in the waste gas are 10%: 10%-25%: 3.6%-30%, and the rest is He. A multi-component mixed gas containing CO2, CH4, and N2O is introduced into a quartz reaction bed equipped with a Ni-Mg@FER catalyst at a temperature of 750°C and a reaction space velocity of 1.2×10 5 h -1 The reaction was carried out under the condition of a total gas flow rate of 120 ml / min.

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