Catalytic pyrolysis of organic waste salt aerogel catalyst and its preparation method and application

Abstract

The present application relates to the technical field of industrial solid waste treatment, in particular to a catalytic pyrolysis organic waste salt aerogel catalyst and its preparation method and application. x The catalyst prepared by the present application takes SiO2 / Al2O3 aerogel as a carrier, and loads non-noble metal oxide Mo x (M is at least one of Co, Mn, Fe, Ni, Cu and Ce); the active component is anchored in the three-dimensional mesoporous framework in situ by using a sol-gel method. Compared with the traditional supported catalyst, the aerogel catalyst prepared by the present application has a large specific surface area, a high active site dispersion degree and a significantly improved mass transfer efficiency; the inorganic network structure is temperature-resistant and anti-shedding; the framework has a high mechanical strength, is elastically contacted with salt particles and is wear-resistant, and the catalyst has a high recovery rate. The organic matter can be deeply removed at a low temperature, the preparation is simple and the catalyst can be reused, the pyrolysis temperature and operation cost are significantly reduced, and the catalyst has a good industrial application prospect.

Description

Technical Field

[0001] This invention relates to the field of industrial solid waste treatment technology, specifically to a catalytic pyrolysis organic waste salt aerogel catalyst, its preparation method, and its application. Background Technology

[0002] Organic waste salt is a major solid byproduct generated through evaporation and crystallization in industries such as chemical, pharmaceutical, pesticide, petrochemical, and dyeing, under the premise of "zero discharge" of wastewater. It is primarily composed of inorganic salts such as sodium chloride and sodium sulfate, but also carries various organic pollutants and heavy metals, exhibiting characteristics of "mixed salts" and posing a high environmental risk. my country's annual production of organic waste salt exceeds 20 million tons, with diverse sources and complex compositions. Improper disposal can easily lead to environmental problems such as soil salinization and groundwater pollution, as well as wasting salt resources. Therefore, developing waste salt purification and resource utilization technologies is of great significance for environmental protection and the sustainable development of these industries.

[0003] Current methods for treating organic waste salts are mainly divided into two categories: non-thermal treatment and thermal treatment. Non-thermal treatment processes include salt washing, recrystallization, membrane separation, and advanced oxidation, which typically require dissolving the waste salt in an aqueous solution for treatment. This method is costly and makes it difficult to achieve deep purification of organic matter. Thermal treatment is the most commonly used method for removing organic pollutants from waste salts, mainly including pyrolysis carbonization and high-temperature melting. The former is usually carried out under oxygen-deficient conditions at 600-700℃, while the latter requires heating to 800-1200℃ to completely decompose the organic matter. However, high-temperature treatment has problems: the melting point of waste salts fluctuates greatly; alkali metal salts are easily melted at high temperatures, which can corrode pyrolysis kilns and cause slagging, agglomeration, and pipe blockage, affecting operational stability. At the same time, the extremely high pyrolysis temperature leads to huge energy consumption and high operating costs. In addition, thermal treatment processes generally suffer from problems such as unclear reaction mechanisms and insufficient treatment efficiency. Chinese patent application CN201610658535.7 discloses a refining method for organic salts, in which organic waste salt is passed into a rotary kiln for high-temperature pyrolysis, causing the organic matter in the salt to decompose and carbonize. However, this method still requires operation at high temperatures, resulting in high costs and potential equipment damage.

[0004] To lower the pyrolysis temperature and improve the efficiency of organic matter removal, researchers have attempted to introduce catalysts for catalytic pyrolysis, but some shortcomings exist. Chinese patent application CN202010481572.1 discloses a method for treating organic waste salts using low-temperature catalytic pyrolysis, in which organic waste salts are mixed with an ammonium salt catalyst and pyrolyzed at 300–700°C in an inert atmosphere. While this method lowers the pyrolysis temperature to some extent, the ammonium salt catalyst used is a disposable consumable and cannot be recycled; furthermore, the pyrolysis process requires an inert atmosphere such as nitrogen or argon, increasing operating costs and limiting its industrial application prospects. Chinese patent application CN202410989301.5 discloses a catalyst for the catalytic pyrolysis of organic waste salts, using ceramics, activated alumina, silica, or silica-alumina molecular sieves as supports, and loading transition metal oxides such as copper oxide and cobalt oxide as active components. This catalyst can achieve catalytic pyrolysis of waste salts at 350–550°C, and the catalyst can be reused, significantly reducing the treatment temperature and production costs. However, this catalyst faces several challenges in practical applications. First, the metal oxide active component is only loaded on the outer surface of the support and within shallow pores, resulting in low solid-solid contact efficiency between waste salt particles and the catalyst's active sites, limiting further improvements in catalytic efficiency. Second, during repeated pyrolysis-cooling cycles, thermal stress arises between the support and the active component due to differences in their coefficients of thermal expansion. Long-term operation can lead to sintering and agglomeration of the active component, deteriorating the catalyst's temperature resistance and reducing its catalytic activity. Finally, in industrial stirring or fluidized bed operations, continuous mechanical friction occurs between the waste salt particles and the catalyst, causing the active component coating on the support surface to gradually peel off. This not only results in catalyst loss and wear but also allows the active component to mix into the waste salt, affecting the purity of the regenerated salt.

[0005] In recent years, metal aerogels have attracted widespread attention as a novel porous catalytic material. Composed of metal nanostructures, metal aerogels combine the high conductivity and catalytic activity of metals with the large specific surface area and porous self-supporting properties of aerogels. Their three-dimensional network structure provides abundant active sites and excellent mass transfer channels, facilitating sufficient contact between reactants and catalytically active centers. Existing research has shown that non-noble metal aerogel materials exhibit excellent catalytic performance in catalytic oxidation and electrocatalysis reactions. Chinese patent application CN202411811947.0 discloses a metal aerogel catalyst, its preparation method, and its applications, composed of metals such as Ni, Co, Mn, Cu, or Fe and carbon materials. However, currently published patents on metal aerogel catalysts mainly focus on the field of electrocatalysis, and there are no reports of applying metal aerogel catalysts to the catalytic pyrolysis of industrial waste salts.

[0006] Therefore, addressing the problems of insufficient dispersion of active sites, low solid-solid mass transfer efficiency, easy detachment of active components due to temperature fluctuations, and severe mechanical wear in existing industrial waste salt catalytic pyrolysis technologies, this invention develops an integrated, non-precious metal aerogel catalyst. This catalyst possesses a well-developed mesoporous network structure, significantly improving mass transfer efficiency; its inorganic network framework exhibits strong resistance to temperature changes, effectively preventing the detachment of active components; simultaneously, its high mechanical strength provides excellent buffering and wear resistance when in contact with waste salt particles, which helps reduce catalyst loss and facilitates screening and recovery. Its application in the catalytic pyrolysis of organic waste salts has significant research and practical value. Summary of the Invention

[0007] The purpose of this invention is to provide a catalyst for catalytic pyrolysis of organic waste salt aerogel, its preparation method and application, in order to solve the problems mentioned in the background art.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0009] In a first aspect, the present invention provides an aerogel catalyst for the catalytic pyrolysis of organic waste salts, the catalyst comprising a SiO2 / Al2O3 composite oxide aerogel support and a non-precious metal oxide active component supported on the support; the general formula of the non-precious metal oxide active component is MO. x M is selected from any one or a combination of at least two of cobalt (Co), manganese (Mn), iron (Fe), nickel (Ni), copper (Cu), and cerium (Ce).

[0010] Furthermore, the non-precious metal oxide active component is selected from at least one of cobalt oxide (Co3O4) and manganese oxide (MnO2).

[0011] Furthermore, in the non-precious metal oxide active component, the molar ratio of Co to Mn is (0.1~10):1.

[0012] Furthermore, the preferred molar ratio of Co to Mn is (0.5~4):1.

[0013] Furthermore, the catalyst contains 1-15% by mass of non-precious metal elements.

[0014] Furthermore, the catalyst contains 3-10% by mass of non-precious metal elements.

[0015] Furthermore, in the SiO2 / Al2O3 composite oxide aerogel carrier, the molar ratio of SiO2 to Al2O3 is (1~10):1, and more preferably (2~5):1.

[0016] Furthermore, the specific surface area of ​​the catalyst is 200~800 m². 2 / g, pore volume 0.5~3.0cm 3 / g, with an average pore size of 2~50nm.

[0017] Furthermore, the particle size of the catalyst is 100-200 mesh, more preferably 120-140 mesh.

[0018] Secondly, the present invention provides a method for preparing the supported non-noble metal oxide aerogel catalyst, comprising the following steps:

[0019] Step 1: Dissolve the aluminum source in a mixed solvent of anhydrous ethanol and water, add the silicon source and an acid catalyst, and carry out a hydrolysis reaction to obtain a silicon-aluminum composite sol.

[0020] Step 2: Add a non-precious metal salt solution to the silica-alumina composite sol, mix well, add a gelation promoter, and let it stand to gel, thus obtaining a wet gel.

[0021] Step 3: Perform an aging treatment on the wet gel;

[0022] Step 4: Solvent replacement of the aged wet gel.

[0023] Step 5: Perform gradient drying on the solvent-displaced wet gel;

[0024] Step 6: Calcine and grind the dried gel to obtain the supported non-precious metal oxide aerogel catalyst.

[0025] Further, in step 1, the silicon source is any one of tetraethyl orthosilicate (TEOS), tetramethyl orthosilicate, and water glass, preferably tetraethyl orthosilicate.

[0026] Further, in step 1, the aluminum source is any one of aluminum chloride (AlCl3·6H2O), aluminum nitrate, and aluminum isopropoxide, preferably aluminum chloride.

[0027] Furthermore, in step 1, the acid catalyst is any one of hydrochloric acid, nitric acid, and acetic acid, preferably hydrochloric acid.

[0028] Furthermore, in step 1, the concentration of the acid catalyst is 0.05~0.5 mol / L.

[0029] Furthermore, in step 1, the hydrolysis reaction temperature is 40~70℃ and the time is 2~8h.

[0030] In this invention, a sol-gel method is used to prepare the catalyst. A SiO2 / Al2O3 composite oxide aerogel framework is constructed through a co-hydrolysis and condensation reaction of silicon and aluminum sources. Simultaneously, a non-noble metal salt precursor is introduced during the sol stage, ensuring uniform dispersion of metal ions within the sol system. After gelation, the metal ions are uniformly anchored within the aerogel framework and, upon calcination, are transformed into metal oxide nanoparticles, achieving a high degree of dispersion of the active component on the support. Compared to traditional impregnation and loading methods, this invention directly introduces the metal salt into the sol system, utilizing the formation of the gel framework during the sol-gel process to physically confine and chemically anchor the metal ions. This results in a more uniform distribution of the active component, stronger binding force with the support, and effectively prevents migration and aggregation of the active component during use.

[0031] Further, in step 2, the non-precious metal salt is a cobalt salt and / or a manganese salt; the cobalt salt is any one of cobalt nitrate (Co(NO3)2·6H2O), cobalt chloride (CoCl2·6H2O), and cobalt acetate (Co(CH3COO)2·4H2O), preferably cobalt nitrate; the manganese salt is any one of manganese nitrate (Mn(NO3)2·4H2O), manganese chloride (MnCl2·4H2O), and manganese acetate (Mn(CH3COO)2·4H2O), preferably manganese nitrate.

[0032] Further, in step 2, the gelation promoter is any one of 1,2-epoxypropane, 1,2-epoxybutane, and epichlorohydrin; preferably 1,2-epoxypropane.

[0033] Furthermore, in step 2, the amount of gelation promoter added is 0.5 to 5 times the total molar number of silicon and aluminum sources.

[0034] Furthermore, in step 2, the gelation temperature is 30~70℃ and the time is 2~24h.

[0035] Further, in step 3, the aging treatment involves immersing the wet gel in an aging solvent and aging it at 40~60℃ for 12~48h; the aging solution is any one of ethanol, isopropanol, and n-butanol, preferably ethanol.

[0036] Furthermore, in step 4, solvent replacement involves soaking and replacing the aged wet gel with a replacement solvent, with 1 to 3 replacements, each lasting 2 to 12 hours.

[0037] Furthermore, in step 4, the replacement solvent is any one of isopropanol, n-butanol, and acetone, preferably isopropanol.

[0038] In this invention, water and ethanol in the wet gel channels are replaced with isopropanol, which has a lower surface tension, by solvent replacement. This helps to reduce the damage to the gel skeleton by capillary forces during the subsequent drying process, thereby maintaining the aerogel structure under normal pressure conditions and avoiding the high investment in supercritical drying equipment.

[0039] Furthermore, in step 5, gradient drying is performed sequentially under multiple temperature gradients, with a drying temperature range of 50~150℃ and a total drying time of 4~12h.

[0040] Furthermore, in step 5, the gradient drying includes drying at 60℃, 80℃, 100℃, 120℃, and 150℃ for 1-3 hours each.

[0041] Furthermore, the gradient drying was carried out at 60℃, 80℃, 100℃, 120℃, and 150℃ for 2 hours each.

[0042] A gradient heating drying method is used to slowly and uniformly remove the solvent from the wet gel, avoiding shrinkage and cracking of the aerogel skeleton caused by rapid solvent vaporization, thus ensuring the integrity of the aerogel structure.

[0043] Furthermore, in step 6, the roasting temperature is 400~700℃; preferably 500~600℃.

[0044] Furthermore, in step 6, the roasting time is 3 to 8 hours; preferably 4 to 6 hours.

[0045] Furthermore, the heating rate during calcination is 1~10℃ / min; preferably 2~5℃ / min.

[0046] Thirdly, the present invention provides the application of the aerogel catalyst, comprising the following steps:

[0047] S1: In an oxygen-containing atmosphere, organic waste salt particles are mixed with the supported non-precious metal oxide aerogel catalyst as described in the first aspect and subjected to catalytic pyrolysis.

[0048] S2: The solid after catalytic pyrolysis is dissolved in water, filtered, and filtrate and residue are obtained. The filtrate is evaporated and crystallized to obtain crystalline salt, thus completing the catalytic pyrolysis of organic waste salt.

[0049] In this invention, the three-dimensional porous structure of the aerogel catalyst facilitates thorough mixing and contact with waste salt particles, while the large pores of the aerogel support enable the rapid escape of gaseous organic products, preventing secondary reactions and carbon buildup. Under an oxygen-containing atmosphere, the highly dispersed transition metal oxide nanoparticles within the aerogel framework provide abundant surface-active oxygen species and oxygen vacancies, efficiently promoting the low-temperature deep oxidative degradation of organic pollutants. Simultaneously, the high thermal stability and structural integrity of the aerogel support ensure the performance stability of the catalyst during recycling.

[0050] Furthermore, the oxygen-containing atmosphere includes air and / or oxygen.

[0051] Furthermore, in the oxygen-containing atmosphere, the amount of oxygen introduced is 5 to 25 times the chemical oxygen demand contained in the organic waste salt.

[0052] Furthermore, the particle size of the organic waste salt particles is 30-100 mesh, preferably 40-80 mesh.

[0053] Furthermore, the organic waste salt includes any one or a combination of at least two of the following: pesticide organic waste salt, pharmaceutical organic waste salt, dyeing and printing organic waste salt, and coal chemical organic waste salt.

[0054] Furthermore, the mass ratio of the organic waste salt to the catalyst is (5~100):1; preferably (10~50):1.

[0055] Furthermore, the temperature of the catalytic pyrolysis is 300~500℃, more preferably 350~450℃.

[0056] Furthermore, the catalytic pyrolysis time is 30~120 min, more preferably 45~90 min.

[0057] Furthermore, the catalytic pyrolysis method includes catalytic pyrolysis using a heating furnace, a rotary tube furnace, or a rotary kiln.

[0058] Furthermore, the heating rate of the furnace is 5~20℃ / min.

[0059] Furthermore, a pretreatment step is included before mixing the organic waste salt particles and the catalyst; the pretreatment method includes: crushing and drying the organic waste salt.

[0060] Furthermore, the pulverization method includes grinding and ball milling;

[0061] Furthermore, the drying temperature is 90~120℃, and the time is 12~24h.

[0062] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0063] (1) In this invention, for the first time, SiO2 / Al2O3 composite oxide aerogel prepared by the sol-gel method is used as a carrier to load non-precious metal oxide active components, and it is applied to the field of catalytic pyrolysis of organic waste salts. The aerogel carrier has a high specific surface area (200~800m²). 2 The structure of the three-dimensional interconnected channels enables the active components to be highly dispersed at the nanoscale, exposing more catalytic active sites and significantly improving catalytic efficiency. It can achieve efficient catalytic oxidation and degradation of organic pollutants in waste salt at a relatively low temperature of 350~450℃, greatly reducing the pyrolysis treatment temperature, avoiding the melting problem of waste salt at high temperature, and significantly saving energy consumption.

[0064] (2) In this invention, by introducing Al2O3 components into SiO2 aerogel, an integrated aerogel framework is constructed using Si-O-Al bonding. The active components are chemically anchored to the support through a sol-gel process, rather than being coated on the surface of traditional supported catalysts. This structure effectively solves the problem of active components easily detaching from traditional catalysts under temperature fluctuations. The three-dimensional network structure of the aerogel remains stable and undeformed during repeated pyrolysis-cooling cycles, significantly improving the catalyst's resistance to thermal aging and its stability in repeated use.

[0065] (3) In this invention, the catalyst is prepared by the sol-gel method. A non-precious metal salt precursor is introduced in the sol stage, so that the metal ions are uniformly anchored in the aerogel framework during the sol-gel transformation. After calcination, highly dispersed metal oxide nanoparticles are formed, and the uniformity of the distribution of active components is significantly better than that of the traditional impregnation method. At the same time, atmospheric pressure gradient drying technology is used instead of supercritical drying in the preparation process, which greatly reduces the preparation cost. The process is simple and controllable and suitable for industrial scale-up production.

[0066] (4) In this invention, the active components used are all non-precious metals (cobalt, manganese, etc.), and the raw materials are widely available and inexpensive. Compared with traditional supported catalysts, the active components in the integrated aerogel catalyst of this invention are embedded in the skeleton, which has high physical strength and plays a buffering and wear-resistant role when in elastic contact with waste salt particles. The catalyst recovery rate is over 95%, which is far superior to traditional supported catalysts (usually less than 85%). This is beneficial for the efficient screening and separation of the catalyst and regenerated salt, further reducing the overall operating cost of the waste salt treatment process, and has good economic benefits and industrial application prospects. Attached Figure Description

[0067] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0068] Figure 1The results are SEM characterization results of the aerogel catalyst prepared in Example 1 of this invention.

[0069] Figure 2 This is a physical image of the aerogel catalyst prepared in Example 1 of this invention. Detailed Implementation

[0070] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0071] In the following examples and comparative examples, the main inorganic salt component of the organic waste salt was NaCl. When NaCl was dissolved in pure water to prepare a 100 g / L brine solution, the TOC content was measured to be 2368.6 ± 5 mg / L. Although the same batch of industrial waste salt was used in the following examples and comparative examples, the TOC of the waste salt before catalytic pyrolysis was slightly different due to the limitations of experimental time arrangement and the influence of TOC test error. The differences were all within the allowable error range.

[0072] The preparation method of the organic waste salt particles used in the following examples and comparative examples is as follows: After grinding the above-mentioned organic waste salt, it is dried at 110°C for 24 hours to obtain organic waste salt particles with a particle size of 40~80 mesh.

[0073] Example 1: This example provides a catalyst for the catalytic pyrolysis of organic waste salt aerogel and its application. The preparation method includes:

[0074] Step 1: Weigh the raw materials according to the molar ratio of SiO2 to Al2O3 of 4:1. Dissolve 2.414g of AlCl3·6H2O in a mixed solvent of 20mL anhydrous ethanol and 10mL distilled water. Stir until completely dissolved, then add 20.83g of tetraethyl orthosilicate (TEOS). Stir evenly and then slowly add 0.1mol / L hydrochloric acid solution until pH=3. Hydrolyze at 55℃ for 4h to obtain a silica-alumina composite sol.

[0075] Step 2: Based on the mass percentage of Co in the catalyst being 5%, weigh 1.235g of Co(NO3)2·6H2O and dissolve it in 5mL of distilled water. Add this solution to the above-mentioned silica-alumina composite sol, stir and mix evenly, then add 4.0mL of 1,2-epoxypropane (approximately twice the total molar amount of TEOS and AlCl3), stir evenly, and let stand. Gelation is carried out at 50℃ for 6h to obtain a wet gel.

[0076] Step 3: Immerse the wet gel in anhydrous ethanol and age it at 50°C for 24 hours;

[0077] Step 4: Immerse the aged wet gel in isopropanol for solvent replacement, twice, the first replacement for 3 hours and the second replacement for 6 hours;

[0078] Step 5: Place the solvent-replaced wet gel in an oven and dry it for 2 hours at 60℃, 80℃, 100℃, 120℃ and 150℃ respectively.

[0079] Step 6: Place the dried gel in a muffle furnace and heat it to 550℃ at a heating rate of 5℃ / min. Calcinate for 5 hours. After cooling, grind the product to 120~140 mesh to obtain the Co3O4-SiO2 / Al2O3 aerogel catalyst.

[0080] The application of the aerogel catalyst includes the following steps:

[0081] S1: In an air atmosphere, mix 5g of organic waste salt particles and the obtained catalyst at a mass ratio of 10:1, place them in a tube furnace, raise the temperature to 400℃ at a heating rate of 10℃ / min, hold for 60min for pyrolysis, and remove after cooling.

[0082] S2: Dissolve the mixture of pyrolyzed catalyst and organic waste salt in deionized water to prepare a brine with a salt content of 100g / L. Stir magnetically to dissolve all inorganic salts, filter out the catalyst, obtain filtrate, evaporate the filtrate to crystallize, and obtain crystalline salt, thus completing the catalytic pyrolysis of organic waste salt.

[0083] Example 2: This example provides a catalyst for the catalytic pyrolysis of organic waste salt aerogel and its application. The only difference from Example 1 is that:

[0084] In step 1, Co(NO3)2·6H2O was replaced with Mn(NO3)2·4H2O (50wt% aqueous solution). Based on the mass percentage of Mn element in the catalyst being 5%, the corresponding mass of Mn(NO3)2·4H2O solution was weighed and added to the silica-alumina composite sol to obtain the MnO2-SiO2 / Al2O3 aerogel catalyst; other conditions were the same as in Example 1.

[0085] Example 3: This example provides a catalytic pyrolysis organic waste salt aerogel catalyst and its application. The only difference from Example 1 is that, based on a total mass percentage of 5% Co and Mn in the catalyst, the molar ratio of Co to Mn is 1:1. 0.617g of Co(NO3)2·6H2O and the corresponding mass of Mn(NO3)2·4H2O (50wt% aqueous solution) are weighed and dissolved together in 5mL of distilled water, and added to a silica-alumina composite sol to obtain a Co3O4-MnO2 / SiO2-Al2O3 aerogel catalyst; other conditions are the same as in Example 1.

[0086] Example 4: This example provides a catalyst for catalytic pyrolysis of organic waste salt aerogel and its application. The only difference from Example 3 is that the molar ratio of SiO2 to Al2O3 is 2:1, that is, the amount of AlCl3·6H2O is adjusted to 4.828g and the amount of TEOS is adjusted to 20.83g; other conditions are the same as in Example 3.

[0087] Example 5: This example provides a catalyst for catalytic pyrolysis of organic waste salt aerogel and its application. The only difference from Example 3 is that the molar ratio of SiO2 to Al2O3 is 8:1, that is, the amount of AlCl3·6H2O is adjusted to 1.207g and the amount of TEOS is adjusted to 20.83g; other conditions are the same as in Example 3.

[0088] Example 6: This example provides a catalyst for catalytic pyrolysis of organic waste salt aerogel and its application. The only difference from Example 3 is that the molar ratio of Co to Mn is 0.25:1, that is, the amount of Co(NO3)2·6H2O is 0.247g, and the amount of Mn(NO3)2·4H2O (50wt% aqueous solution) is calculated according to the molar number of Mn element; other conditions are the same as in Example 3.

[0089] Example 7: This example provides a catalyst for catalytic pyrolysis of organic waste salt aerogel and its application. The only difference from Example 3 is that the molar ratio of Co to Mn is 4:1, that is, the amount of Co(NO3)2·6H2O is 0.988g, and the amount of Mn(NO3)2·4H2O (50wt% aqueous solution) is calculated according to the molar number of Mn element; other conditions are the same as in Example 3.

[0090] Example 8: This example provides a catalyst for catalytic pyrolysis of organic waste salt aerogel and its application. The only difference from Example 3 is that the total mass percentage of Co and Mn elements in the catalyst is 3%, that is, the total amount of Co(NO3)2·6H2O and Mn(NO3)2·4H2O is calculated based on the total mass of metal elements accounting for 3% of the catalyst mass; other conditions are the same as in Example 3.

[0091] Example 9: This example provides a catalyst for catalytic pyrolysis of organic waste salt aerogel and its application. The only difference from Example 3 is that the total mass percentage of Co and Mn elements in the catalyst is 10%, that is, the total amount of Co(NO3)2·6H2O and Mn(NO3)2·4H2O is calculated based on the total mass of metal elements accounting for 10% of the catalyst mass; other conditions are the same as in Example 3.

[0092] Example 10: This example provides a catalyst for catalytic pyrolysis of organic waste salt aerogel and its application. The only difference from Example 3 is that in S1, the mass ratio of organic waste salt to catalyst is 5:1; other conditions are the same as in Example 3.

[0093] Example 11: This example provides a catalyst for catalytic pyrolysis of organic waste salt aerogel and its application. The only difference from Example 3 is that in S1, the mass ratio of organic waste salt to catalyst is 30:1; other conditions are the same as in Example 3.

[0094] Example 12: This example provides a catalyst for catalytic pyrolysis of organic waste salt aerogel and its application. The only difference from Example 3 is that in S1, the mass ratio of organic waste salt to catalyst is 50:1; other conditions are the same as in Example 3.

[0095] Example 13: This example provides a catalyst for catalytic pyrolysis of organic waste salt aerogel and its application. The only difference from Example 3 is that in S1, the temperature of catalytic pyrolysis is 350°C; other conditions are the same as in Example 3.

[0096] Example 14: This example provides a catalyst for catalytic pyrolysis of organic waste salt aerogel and its application. The only difference from Example 3 is that in S1, the temperature of catalytic pyrolysis is 450°C; other conditions are the same as in Example 3.

[0097] Example 15: This example provides a catalyst for catalytic pyrolysis of organic waste salt aerogel and its application. The only difference from Example 3 is that in S1, the catalytic pyrolysis time is 30 min; other conditions are the same as in Example 3.

[0098] Example 16: This example provides a catalyst for catalytic pyrolysis of organic waste salt aerogel and its application. The only difference from Example 3 is that in S1, the catalytic pyrolysis time is 90 min; other conditions are the same as in Example 3.

[0099] Comparative Example 1: This comparative example provides a method for the pyrolysis of organic waste salt, the method being as follows:

[0100] S1: In an air atmosphere, place 5g of organic waste salt particles in a tube furnace, raise the temperature to 400℃ at a heating rate of 10℃ / min, hold for 60min for pyrolysis, and remove after cooling.

[0101] S2: Dissolve the pyrolysis waste salt in deionized water to prepare a brine with a salt content of 100 g / L. Stir the brine magnetically to dissolve all the inorganic salts, filter the brine, and test the organic content of the brine using a TOC analyzer. Evaporate the brine to crystallize the salt and obtain crystalline salt.

[0102] The preparation method of the catalyst is the same as that in Example 1.

[0103] Comparative Example 2: This comparative example provides a method for catalytic pyrolysis of organic waste salts, the method being as follows:

[0104] Supported catalysts were prepared using a conventional impregnation method.

[0105] Weigh 5g of SiO2 / Al2O3 composite oxide powder (SiO2 to Al2O3 molar ratio is 4:1, specific surface area is approximately 250m²). 2 Co(NO3)2·6H2O was used as the support. Based on a Co content of 5% by mass in the catalyst, 1.235 g of Co(NO3)2·6H2O was dissolved in 20 mL of deionized water. The support was added to the cobalt nitrate solution, stirred and impregnated at room temperature for 12 h, then dried at 110 °C for 12 h. It was then placed in a muffle furnace and heated to 550 °C at a rate of 5 °C / min, calcined for 5 h, cooled, and ground to 120–140 mesh to obtain the Co3O4-SiO2 / Al2O3 supported catalyst.

[0106] The application of the aerogel catalyst includes the following steps:

[0107] S1: In an air atmosphere, mix 5g of organic waste salt particles and aerogel catalyst at a mass ratio of 10:1, place them in a tube furnace, raise the temperature to 400℃ at a heating rate of 10℃ / min, keep the temperature for pyrolysis for 60min, and take them out after cooling.

[0108] S2: Dissolve the mixture of pyrolyzed catalyst and organic waste salt in deionized water to prepare a brine with a salt content of 100 g / L. Stir magnetically to dissolve all inorganic salts, filter out the catalyst, obtain filtrate, evaporate the filtrate to crystallize, and obtain crystalline salt.

[0109] Comparative Example 3: This comparative example provides a method for catalytic pyrolysis of organic waste salts, the method being as follows:

[0110] Catalyst preparation: The method of Example 1 was followed, but supercritical drying was used instead of gradient drying. The aged and solvent-replaced wet gel was placed in a supercritical drying vessel and supercritically dried at a critical temperature of 31.1℃ and a critical pressure of 7.38MPa using CO2 as the medium to obtain the Co3O4-SiO2 / Al2O3 aerogel catalyst.

[0111] The application of the aerogel catalyst includes the following steps:

[0112] S1: In an air atmosphere, mix 5g of organic waste salt particles and aerogel catalyst at a mass ratio of 10:1, place them in a tube furnace, raise the temperature to 400℃ at a heating rate of 10℃ / min, keep the temperature for pyrolysis for 60min, and take them out after cooling.

[0113] S2: Dissolve the mixture of pyrolyzed catalyst and organic waste salt in deionized water to prepare a brine with a salt content of 100 g / L. Stir magnetically to dissolve all inorganic salts, filter out the catalyst, obtain filtrate, evaporate the filtrate to crystallize, and obtain crystalline salt.

[0114] Comparative Example 4: This comparative example provides a method for catalytic pyrolysis of organic waste salts, referring to the method in Example 2 of Chinese Patent Application CN202410989301.5:

[0115] Catalyst preparation: Weigh 0.571g Cu(NO3)2·3H2O, 0.493g Co(NO3)2·6H2O and 0.827g citric acid into 50mL of water, stir until dissolved, add 5g of silicon-aluminum molecular sieve ZSM-300, stir for 12h, dry at 110℃ for 15h, and finally calcine in a muffle furnace at a rate of 5℃ / min to 500℃ for 3h. After calcination, a Co and Cu dual-doped molecular sieve supported catalyst is obtained.

[0116] The application of the aerogel catalyst includes the following steps:

[0117] S1: In an air atmosphere, 5g of organic waste salt particles and the aerogel catalyst are mixed at a mass ratio of 10:1, placed in a tube furnace, heated to 400℃ at a heating rate of 10℃ / min, held at the temperature for 60min for pyrolysis, and then cooled and removed.

[0118] S2: Dissolve the mixture of pyrolyzed catalyst and organic waste salt in deionized water to prepare a brine with a salt content of 100 g / L. Stir magnetically to dissolve all inorganic salts, filter out the catalyst, obtain filtrate, evaporate the filtrate to crystallize, and obtain crystalline salt.

[0119] The aerogel catalyst material prepared in Example 1 was characterized by SEM, and the results are as follows: Figure 1 As shown. From Figure 1 As can be seen, this aerogel catalyst material has a porous, fluffy aggregated structure. Figure 2 This is a physical image of the aerogel catalyst prepared in Example 1 of the present invention.

[0120] The organic waste salts before and after catalytic pyrolysis in the above examples and comparative examples were prepared into brine with a salt content of 100 g / L. After filtering the solid catalyst, the TOC content was determined, and the results are shown in Table 1 below.

[0121] Table 1. Comparison of TOC content in waste salt before and after catalytic pyrolysis in the examples and comparative examples.

[0122] TOC content (mg / L) in waste salt before catalytic pyrolysis TOC content (mg / L) in waste salt after catalytic pyrolysis Example 1 2365.2 16.8 Example 2 2366.5 18.3 Example 3 2364.8 10.2 Example 4 2366.1 12.5 Example 5 2365.7 14.6 Example 6 2365.3 15.8 Example 7 2364.9 13.1 Example 8 2366.2 15.2 Example 9 2365.8 11.8 Example 10 2364.6 8.7 Example 11 2365.4 13.9 Example 12 2366.3 17.5 Example 13 2365.1 18.6 Example 14 2364.7 9.8 Example 15 2365.9 14.2 Example 16 2365.5 11.5 Comparative Example 1 2365.8 52.4 Comparative Example 2 2366.4 31.6 Comparative Example 3 2365.2 10.8 Comparative Example 4 2365.7 20.5

[0123] As shown in Table 1, the aerogel catalyst prepared by the sol-gel method in this invention can efficiently catalyze the pyrolysis of organic waste salt at a relatively low temperature (350~450℃), thus achieving deep removal of organic matter from the waste salt.

[0124] A comparison of the relevant data from Examples 1-3 and Comparative Example 1 shows that without the catalyst (Comparative Example 1), the TOC content of the waste salt after pyrolysis was as high as 52.4 mg / L; while after using the aerogel catalyst provided by the present invention, the TOC content of the waste salt after pyrolysis was significantly reduced to 10.2-18.3 mg / L, indicating that the catalyst of the present invention has a significant promoting effect on the catalytic pyrolysis of organic matter in waste salt.

[0125] As can be seen from the comparison between Example 3 and Examples 1-2, the catalytic effect of using Co-Mn bimetallic oxide as the active component (Example 3) is better than that of single Co oxide (Example 1) or single Mn oxide (Example 2). After pyrolysis, the TOC content further decreased from 16.8 mg / L and 18.3 mg / L to 10.2 mg / L, indicating that the synergistic effect between Co and Mn effectively improved the catalytic activity.

[0126] As can be seen from the comparison between Example 3 and Comparative Example 2, the catalyst prepared by directly introducing metal salt into the sol system using the sol-gel method (Example 3, TOC after pyrolysis is 10.2 mg / L) has a significantly better catalytic effect than the catalyst prepared by the traditional impregnation method (Comparative Example 2, TOC after pyrolysis is 31.6 mg / L). This indicates that the sol-gel method can achieve a more uniform dispersion of active components on the aerogel support.

[0127] As can be seen from the comparison between Example 3 and Comparative Example 3, the aerogel catalyst prepared by atmospheric pressure gradient drying (Example 3, TOC after pyrolysis is 10.2 mg / L) has comparable catalytic performance to the aerogel catalyst prepared by supercritical drying (Comparative Example 3, TOC after pyrolysis is 10.8 mg / L). However, atmospheric pressure gradient drying significantly reduces the preparation cost and is more suitable for industrial production.

[0128] As can be seen from the comparison between Example 3 and Comparative Example 4, the Co-Mn oxide / SiO2-Al2O3 aerogel catalyst of the present invention (TOC of 10.2 mg / L after pyrolysis) has a better organic matter removal effect under the same pyrolysis conditions than the Cu-Co / molecular sieve supported catalyst in the prior art (Comparative Example 4, TOC of 20.5 mg / L after pyrolysis). This indicates that the three-dimensional porous structure of the aerogel support is more conducive to the dispersion of active components and the mass transfer of reactants than the traditional molecular sieve support.

[0129] As can be seen from Examples 3-5, by controlling the molar ratio of SiO2 to Al2O3 to (2-8):1, the catalytic performance of the catalyst can be further optimized, so that the TOC content after pyrolysis is 10.2-14.6 mg / L, and the effect is optimal when the molar ratio is 4:1 (Example 3, TOC is 10.2 mg / L).

[0130] As can be seen from Examples 3 and 6-7, by controlling the molar ratio of Co to Mn to be (0.25-4):1 (Examples 3, 6-7), the present invention can achieve efficient removal of organic pollutants from industrial waste salt by catalyst, resulting in a TOC content of 10.2-15.8 mg / L after pyrolysis.

[0131] As can be seen from Examples 3 and 8-9, the present invention can achieve good catalytic effect by controlling the mass percentage of metal elements in the catalyst to 3-10% (Examples 3, 8-9), resulting in a TOC content of 10.2-15.2 mg / L after pyrolysis.

[0132] As can be seen from Examples 3 and 10-12, by controlling the mass ratio of organic waste salt to catalyst to be (5-50):1 (Examples 3, 10-12), the present invention can achieve deep removal of organic matter in waste salt, so that the TOC content after pyrolysis is 8.7-17.5 mg / L.

[0133] As can be seen from Examples 3 and 13-14, the catalyst of the present invention can effectively catalyze the pyrolysis of organic matter in waste salt within a temperature range of 350-450°C (TOC after pyrolysis is 9.8-18.6 mg / L), which is significantly lower than the pyrolysis temperature of above 500°C usually required by the prior art.

[0134] As can be seen from Examples 3 and 15-16, the catalyst of the present invention can achieve good organic matter removal effect within a pyrolysis time of 30-90 min (TOC after pyrolysis is 11.5-14.2 mg / L), indicating that the catalyst has high catalytic efficiency.

[0135] The catalyst samples prepared in Examples 1-5, Comparative Examples 2 and 4 were characterized, and the results are shown in Table 2. Wherein:

[0136] The specific surface area was determined using the gas adsorption BET method, referring to GB / T 19587-2017 "Determination of Specific Surface Area of ​​Solid Substances by Gas Adsorption BET Method". Before testing, the samples were vacuum degassed at 120-150℃ for 4-6 hours to remove adsorbed moisture and impurities from the sample surface. Then, using high-purity nitrogen as the adsorption medium at liquid nitrogen temperature (-196℃) and a relative pressure (P / P0) range of 0.05-0.30, the nitrogen adsorption-desorption isotherms of the samples were measured. The specific surface area of ​​the samples was calculated using the BET equation.

[0137] The average pore size test method is as follows: the Barrett-Joyner-Halenda (BJH) method is used. Based on the desorption branch data of the nitrogen adsorption-desorption isotherm, the pore size distribution is calculated by the BJH model. The pore size value corresponding to the cumulative pore volume reaching 50% in the pore size distribution curve is taken as the average pore size.

[0138] The pore volume test method is as follows: based on the nitrogen adsorption-desorption isotherm, at a relative pressure P / P0≈0.99, the total pore volume of the sample is calculated using the single-point method or the BJH method with the molar volume of liquid nitrogen as the reference.

[0139] The catalyst recovery rate is calculated as follows: After catalytic pyrolysis, the solid mixture after pyrolysis is dissolved in water, stirred to fully dissolve the inorganic salts, and then filtered to recover the catalyst. The recovered catalyst is dried at 110℃ to constant weight and then weighed. The catalyst recovery rate is calculated according to the following formula:

[0140] Catalyst recovery rate (%) = (mass of recovered and dried catalyst / mass of catalyst added before catalytic pyrolysis) × 100%;

[0141] Table 2 Comparison of structural parameters and recovery rates of catalysts in the embodiments of the present invention and comparative examples.

[0142] <![CDATA[Specific surface area (m 2 / g)]]> Average pore size (nm) <![CDATA[pore volume (cm 3 / g)]]> Catalyst recovery rate (%) Example 1 385 8.5 1.02 96.2 Example 2 392 7.8 0.98 95.8 Example 3 408 7.2 1.05 97.1 Example 4 356 9.1 0.95 95.3 Example 5 421 6.8 1.12 96.8 Comparative Example 2 168 4.2 0.31 78.4 Comparative Example 4 215 3.8 0.28 82.6

[0143] As shown in Table 2, the aerogel catalysts prepared by the sol-gel method in this invention (Examples 1-5) have a specific surface area of ​​356-421 m². 2 The concentration of catalysts prepared by the conventional impregnation method ( / g) was significantly higher than that of supported catalysts prepared by the conventional impregnation method (Comparative Example 2, 168m). 2 The aerogel catalyst, disclosed in Chinese patent application CN202410989301.5 (Comparative Example 4, 215 m² / g), has an average pore size (6.8–9.1 nm) and pore volume (0.95–1.12 cm³ / g). 3The / g) is also significantly superior to the comparative example. The well-developed three-dimensional mesoporous network provides more abundant mass transfer channels for the diffusion and reaction of organic pollutants, effectively solving the problem of limited mass transfer in solid-solid reactions.

[0144] Regarding catalyst recovery rate, the aerogel catalyst of this invention achieves a recovery rate of 95.3%~97.1% after one catalytic pyrolysis-separation cycle, significantly higher than Comparative Example 2 (78.4%) and Comparative Example 4 (82.6%). This is attributed to the high mechanical strength and structural integrity resulting from the integrated aerogel preparation. The active components are embedded within the framework rather than being surface-coated, making them less prone to peeling and wear during mechanical contact with waste salt particles, effectively solving the problem of high mechanical wear in solid-solid processes. Simultaneously, the three-dimensional network structure of the aerogel remains stable during calcination at 400~700℃ and repeated pyrolysis-cooling cycles, further ensuring the long service life of the catalyst.

[0145] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0146] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An aerogel catalyst for the catalytic pyrolysis of organic waste salts, the catalyst comprising a SiO2 / Al2O3 composite oxide aerogel support and a non-precious metal oxide active component supported on the support; characterized in that: The general formula of the non-noble metal oxide active component is MO. x M is any one or a combination of at least two of cobalt, manganese, iron, nickel, copper, and cerium.

2. The aerogel catalyst according to claim 1, characterized in that: The mass percentage of non-precious metal elements in aerogel catalysts is 1-15%.

3. The aerogel catalyst according to claim 1, characterized in that: In the SiO2 / Al2O3 composite oxide aerogel carrier, the molar ratio of SiO2 to Al2O3 is (1~10):

1.

4. The aerogel catalyst according to claim 1, characterized in that: The specific surface area of ​​the catalyst is 200~800m². 2 / g, pore volume 0.5~3.0cm 3 / g, with an average pore size of 2~50nm and an average particle size of 100~200 mesh.

5. The method for preparing the aerogel catalyst according to any one of claims 1 to 4, characterized in that: Includes the following steps: Step 1: Dissolve the aluminum source in a mixed solvent of anhydrous ethanol and water, add the silicon source and acid catalyst, and carry out a hydrolysis reaction at a temperature of 40~70℃ for 2~8h to obtain a silicon-aluminum composite sol. Step 2: Add a non-precious metal salt solution to the silica-alumina composite sol, mix well, add a gelation promoter, and let it stand to gel. The gelation temperature is 30~70℃ and the time is 2~24h to obtain a wet gel. The non-precious metal salt is any one or at least two of cobalt salt, manganese salt, iron salt, nickel salt, copper salt, and cerium salt. Step 3: The wet gel is subjected to aging treatment. The aging treatment method is as follows: the wet gel is immersed in an aging solvent and aged at 40~60℃ for 12~48h; the aging solution is any one of ethanol, isopropanol, and n-butanol. Step 4: Soak and replace the aged wet gel with a replacement solvent, 1 to 3 times, with each replacement lasting 2 to 12 hours; the replacement solvent can be any one of isopropanol, n-butanol, or acetone; Step 5: Perform gradient drying on the solvent-replaced wet gel; the gradient drying is performed at 60℃, 80℃, 100℃, 120℃, and 150℃ for 1~3 hours each; Step 6: Calcine and grind the dried gel to obtain the supported non-precious metal oxide aerogel catalyst; the calcination temperature is 400~700℃, the calcination time is 3~8h, and the calcination heating rate is 1~10℃ / min.

6. The method for preparing the aerogel catalyst according to claim 5, characterized in that: In step 1, the silicon source is any one of tetraethyl orthosilicate, tetramethyl orthosilicate, or water glass; The aluminum source can be any one of aluminum chloride, aluminum nitrate, or aluminum isopropoxide; The acid catalyst is any one of hydrochloric acid, nitric acid, or acetic acid, and the concentration of the acid catalyst is 0.05~0.5 mol / L.

7. The method for preparing the aerogel catalyst according to claim 5, characterized in that: In step 2, the non-precious metal salt is a cobalt salt and / or a manganese salt; the cobalt salt is any one of cobalt nitrate, cobalt chloride, and cobalt acetate; the manganese salt is any one of manganese nitrate, manganese chloride, and manganese acetate.

8. The method for preparing the aerogel catalyst according to claim 5, characterized in that: In step 2, the gelation accelerator is any one of 1,2-epoxypropane, 1,2-epoxybutane, and epichlorohydrin.

9. The method for preparing the aerogel catalyst according to claim 5, characterized in that: In step 2, the amount of gelation promoter added is 0.5 to 5 times the total molar amount of silicon source and aluminum source.

10. The application of an aerogel catalyst as described in any one of claims 1 to 4 in the catalytic pyrolysis of organic waste salts, characterized in that: Includes the following steps: S1: In an oxygen-containing atmosphere, organic waste salt particles are mixed with an aerogel catalyst and catalytically pyrolyzed at 300~500℃ for 30~120min; the particle size of the organic waste salt particles is 30~100 mesh; the mass ratio of organic waste salt to catalyst is (5~100):

1. S2: Dissolve the solid after catalytic pyrolysis in water, filter to obtain filtrate and filter residue; evaporate the filtrate to crystallize and obtain crystalline salt, thus completing the catalytic pyrolysis of organic waste salt.

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