A method for removing phosphine from a high-temperature environment using activated alumina adsorbent

Abstract

The present application relates to the technical field of gas purification, and discloses a method for removing phosphine by using active alumina adsorbent suitable for high-temperature environment, which comprises the following steps: mixing pseudo-boehmite, light magnesium oxide, zinc oxide and boric acid to obtain dry base powder; adding reduced graphene oxide and aluminum sol to knead low-acidity mud; adding surface passivation type active heat-conducting precursor for secondary kneading; obtaining adsorbent through forming, drying, and inert atmosphere step-sintering; and finally, passing phosphorus-containing waste gas at high temperature for adsorption. Through the construction of graphene and modified aluminum nitride composite heat-conducting network, the present application solves the problem of high-temperature heat accumulation; by using zinc-boron glass phase and magnesium-aluminum spinel reinforced skeleton, the present application inhibits high-temperature phase transition and pore collapse; by using step-by-step kneading and surface passivation technology, the present application effectively prevents the hydrolysis of heat-conducting fillers, and improves the high-temperature stability and phosphine removal efficiency of the adsorbent.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of gas purification, in particular to a method for removing phosphine by using active alumina adsorbent suitable for high-temperature environment. BACKGROUND

[0002] Phosphine in industrial waste gas is usually removed by oxidation adsorption. Since the oxidation of phosphine is a strong exothermic reaction, a large amount of heat will be released in the adsorbent bed when treating high-concentration waste gas or operating under high-temperature conditions. The thermal conductivity of the active alumina carrier itself is low, and the reaction heat is difficult to quickly transfer to the outside through the skeleton, resulting in the formation of local overheating areas in the bed. This heat accumulation phenomenon not only causes a large radial temperature difference in the bed, reducing the utilization rate of the adsorbent, but also may cause uncontrolled temperature rise and pose a safety hazard in severe cases.

[0003] Continuous high-temperature environment or local temperature rise caused by reaction heat can damage the skeleton stability of active alumina. Under high-temperature action, metastable gamma-alumina is prone to sintering and gradually changes to alpha-alumina, which is more thermodynamically stable. This phase change process is usually accompanied by grain growth, pore collapse, and a significant reduction in specific surface area, resulting in a decrease in the adsorbent's capacity to accommodate oxidation products, thereby significantly reducing the saturated adsorption capacity and service life of the adsorbent and increasing the operating cost of industrial applications.

[0004] To solve the heat dissipation problem, adding high-thermal-conductivity fillers such as aluminum nitride to the matrix is a common technical approach. However, the preparation of active alumina usually involves an acid peptization and wet molding process. Aluminum nitride powder is prone to hydrolysis in acidic aqueous solutions, generating aluminum hydroxide and releasing ammonia gas. This process not only causes the filler to lose its thermal conductivity, but also forms defects inside the molded body, resulting in low mechanical strength and easy disintegration of the prepared adsorbent, limiting the practical application of high-thermal-conductivity composite adsorbents. SUMMARY

[0005] The technical problem solved by the present application is that existing active alumina phosphorus removal adsorbents have low thermal conductivity under high-temperature conditions, and the heat released by the oxidation reaction of phosphine is difficult to effectively dissipate, resulting in local overheating in the adsorbent bed. At the same time, high-temperature environment can cause the alumina carrier to change from gamma phase to alpha phase, causing pore collapse and reduction of specific surface area. In addition, aluminum nitride as a high-thermal-conductivity filler is prone to hydrolysis and failure in conventional acid-based molding processes.

[0006] To solve the above problems, the present application provides the following technical solutions:

[0007] The present application provides a method for removing phosphine by using active alumina adsorbent suitable for high-temperature environment, which adopts the following technical solutions:

[0008] A method for removing phosphine using activated alumina adsorbent suitable for high-temperature environments includes the following steps:

[0009] S1. By weight, mix 90-110 parts of pseudoboehmite, 4.0-7.0 parts of light magnesium oxide, 3.0-6.0 parts of zinc oxide powder and 1.5-1.8 parts of boric acid to obtain a dry-based powder.

[0010] S2. Add 5-10 parts of reduced graphene oxide dispersion and 42-68 parts of aluminum sol to the dry base powder, and perform sol-kneading to obtain low acidity matrix mud.

[0011] S3. Add 22-35 parts of surface passivation type active thermally conductive precursor to the low acidity matrix mud, and knead it a second time to obtain composite adsorbent paste.

[0012] S4. The composite adsorbent paste is shaped and dried to obtain a dried green body;

[0013] S5. The dried green blank is sintered in sections under an inert atmosphere, and the activated alumina adsorbent is obtained after cooling.

[0014] S6. Fill the reactor with activated alumina adsorbent, heat it to the adsorption temperature under inert gas protection, and introduce industrial waste gas containing 1-500 ppm phosphine, controlling the gas volume hourly space velocity to be 2000-4000 h⁻¹. -1 .

[0015] By adopting the above technical solution, the present invention utilizes process control and component synergy in each step:

[0016] A continuous thermally conductive network is formed: The reduced graphene oxide introduced in step S2 disperses and connects in the matrix due to its two-dimensional sheet structure, while the surface-passivated active thermally conductive precursor introduced in step S3 fills the interparticle gaps in the alumina framework. Together, they construct a continuous heat conduction pathway from the inside out within the adsorbent. During the treatment in step S6, this structure can rapidly conduct the heat generated by the phosphating-hydrogenation reaction to the outer surface of the adsorbent and carry it away by the airflow, reducing the radial temperature difference of the bed and avoiding runaway temperature phenomena caused by heat accumulation.

[0017] Improving the stability of the high-temperature framework: In step S1, zinc oxide reacts with boric acid during the sintering process in step S5 to form a zinc-boron glass phase. This liquid phase wets the interface of alumina particles, promotes low-temperature liquid phase sintering, and enhances the bonding strength between particles. Light magnesium oxide reacts with alumina to form magnesium aluminum spinel microcrystals, which are distributed at the alumina grain boundaries. Due to the high stability of the spinel structure, it hinders the phase transformation from γ-Al2O3 to α-Al2O3 at high temperatures, reducing the collapse of channels caused by crystal transformation.

[0018] Process inhibits hydrolysis of heat conduction phase: using the step S2 and S3 of the split charging process, first using the peptizing reaction of aluminum sol and pseudoboehmite to consume the acid in the system, then adding the surface passivation type active heat conduction precursor. This post-charge mode significantly shortens the residence time of aluminum nitride in the acidic wet environment, combined with the barrier effect of the passivation layer on the surface of the precursor, avoiding the hydrolysis of aluminum nitride to form aluminum hydroxide and ammonia, ensuring the integrity of the adsorbent microstructure.

[0019] Preferably, in step S1, the amount of zinc oxide and boric acid satisfies the molar ratio of Zn to B is 1.5:1~2.5:1; in step S2, the solid content of the aluminum sol is 15%-20% and the pH value is 3.5-4.5; the concentration of the reduced graphene oxide dispersion is 0.5wt%-1.0wt%.

[0020] By adopting the above technical scheme, the molar ratio of Zn to B is controlled to adjust the viscosity of the glass phase in the sintering process, and the appropriate viscosity not only ensures the wetting and bonding effect of the liquid phase on the particles, but also prevents the liquid phase from excessive flowing and blocking the mesoporous channels of the adsorbent; the solid content and pH value of the aluminum sol are limited, so that the pseudoboehmite forms a network gel structure with good thixotropy, which enhances the suspension and carrying capacity of the slurry for high-density aluminum nitride particles, and prevents the components from settling and stratifying during the forming process.

[0021] Preferably, in step S3, the surface passivation type active heat conduction precursor is an aluminum nitride particle with a Fe-Ce-Cu composite metal oxide layer loaded on the surface.

[0022] By adopting the above technical scheme, the composite metal oxide layer plays two roles: first, as a physical barrier layer, it isolates water molecules from contacting the aluminum nitride lattice, improving the hydrolysis resistance of the precursor; second, as a catalytically active center, Fe and Cu species provide redox active sites, and Ce species act as oxygen storage components to adjust the local oxygen concentration, synergistically promoting the oxidation reaction of phosphine diffused to the deep layer of the adsorbent, thereby improving the breakthrough adsorption capacity of the adsorbent.

[0023] Preferably, the surface passivation type active heat conduction precursor is prepared by a method comprising the following steps:

[0024] Dissolve ferric nitrate nonahydrate, cerium nitrate hexahydrate and copper nitrate trihydrate in a solvent, wherein the metal molar ratio of Fe:Ce:Cu is (1.8-2.2):1:(0.8-1.2);

[0025] Add aluminum nitride powder with a particle size of 1-5μm to the above solution, control the solid-liquid ratio to be 1g:(15-25)mL, and ultrasonic dispersion under the condition of power 300-500W for 30-45 minutes;

[0026] The solvent is removed by rotary evaporation at a temperature of 60-70 DEG C and a vacuum degree of -0.08 MPa to -0.09 MPa to obtain a precursor dry powder;

[0027] The precursor dry powder is heated to 300-350 DEG C at a temperature increasing rate of 5-8 DEG C / min under an inert atmosphere and a gas flow of 300-500 mL / min and is kept for 1.0-2.0 hours.

[0028] By using the above technical scheme, the metal nitrate is converted into a dense oxide thin layer on the surface of the aluminum nitride in situ by using the solvent-assisted impregnation and low-temperature thermal decomposition process. The heat treatment temperature of 300-350 DEG C ensures complete decomposition of the nitrate and avoids excessive oxidation of the aluminum nitride matrix. The ultrasonic dispersion and rotary evaporation process ensures uniform coating of the active components on the surface of the micron-sized particles and avoids agglomeration.

[0029] Preferably, in step S6, the adsorption temperature is 180 DEG C-260 DEG C.

[0030] By using the above technical scheme, the temperature range can maintain the activation energy required for the phosphine oxidation reaction, ensure a high reaction rate, and cooperate with the thermal conductivity of the material to remove the reaction heat in time and maintain the stability of the reactor temperature field.

[0031] Preferably, in step S5, the process parameters of the staged sintering are as follows:

[0032] The nitrogen flow is 1-2 L / min;

[0033] First stage: heated to 500-550 DEG C at a temperature increasing rate of 4-5 DEG C / min and kept for 1.5-2.0 hours;

[0034] Second stage: continue to heat to 600-650 DEG C at a temperature increasing rate of 2-3 DEG C / min and keep for 2.0-3.0 hours.

[0035] By using the above technical scheme, the first stage of low-temperature sintering (500-550 DEG C) corresponds to the temperature range of the eutectic of zinc oxide and boric acid, and the slow temperature increasing rate makes the liquid phase flow and wet under the action of capillary force; the second stage of high-temperature solidification (600-650 DEG C) promotes the complete dehydration of pseudo-boehmite and the conversion into active alumina, and at the same time promotes the diffusion of magnesium species into the alumina lattice to form an anti-sintering structure.

[0036] Preferably, in step S2, the time of the peptization kneading is 20-30 minutes, and the pH value of the low-acidity matrix mud after kneading is 4.0-5.0; in step S4, the forming pressure is 2-4 MPa, and the diameter of the extrudate is 3-5 mm, and the water content is dried to less than 3%.

[0037] By adopting the technical scheme, the pH value is controlled in the interval of 4.0-5.0, the peptizing environment required for forming a gel network of the aluminum sol and the pseudo-boehmite is maintained, and the chemical corrosion of the heat-conducting component by the acidic medium is minimized; the water content after drying is controlled to be less than 3%, so as to prevent the internal water from rapidly vaporizing to generate internal stress in the subsequent sintering process, and to cause the adsorbent to crack or break.

[0038] The application provides a method for removing phosphine by using active alumina adsorbents in a high-temperature environment.

[0039] 1. The application introduces a reduced graphene oxide dispersion and a surface passivated active heat-conducting precursor to construct a composite heat-conduction system. The reduced graphene oxide extends in the internal structure of the matrix by using its two-dimensional sheet structure, and the surface passivated active heat-conducting precursor fills the gap between the alumina particles. The two work together to establish an effective heat conduction path. This structure can quickly conduct the large amount of heat generated by the oxidation reaction of phosphine to the surface of the adsorbent and be carried away by the airflow, effectively reducing the radial temperature difference of the reactor bed, avoiding the phenomenon of local heat accumulation, and ensuring the phosphorus removal efficiency and operation safety of the adsorbent in high-temperature working conditions.

[0040] 2. The application significantly improves the high-temperature skeleton stability of the adsorbent by adding zinc oxide, boric acid and light magnesium oxide. The zinc-boron glass phase formed by zinc oxide and boric acid during sintering promotes low-temperature liquid phase sintering between particles, improving the mechanical strength of the adsorbent; the spinel microcrystals of magnesium aluminate generated by the reaction of light magnesium oxide and alumina are distributed at the grain boundaries, effectively inhibiting the phase transition of gamma-alumina to alpha-alumina under high-temperature environment, preventing the collapse of the pore channel and the reduction of the specific surface area caused by the crystal type transformation, and thus maintaining the saturated sulfur capacity of the adsorbent during long-term high-temperature use.

[0041] 3. The application solves the hydrolysis problem of aluminum nitride in the water-based forming process by combining the step-by-step peptization kneading process with the surface modification of the precursor. By first performing the peptization reaction to reduce the acidity of the system and then adding the heat-conducting precursor, the residence time of aluminum nitride in the acidic environment is shortened; at the same time, the Fe-Ce-Cu composite metal oxide layer on the surface of the precursor physically blocks the contact between water molecules and the aluminum nitride lattice. This dual protection mechanism avoids the hydrolysis of aluminum nitride to generate aluminum hydroxide and ammonia gas, ensuring the integrity of the microstructure of the adsorbent after forming, and the metal oxide layer on the surface also provides additional catalytic oxidation active centers, improving the overall adsorption performance. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments and comparative examples of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the protection scope of the present application.

[0043] Preparation Example 1-3:

[0044] Preparation Example 1:

[0045] The present preparation example provides a surface passivated active thermal conductive precursor (component A-1), comprising the following steps:

[0046] Accurately weigh 29.1 g of iron nitrate nonahydrate, 17.4 g of cerium nitrate hexahydrate and 7.7 g of copper nitrate trihydrate (corresponding to the metal molar ratio Fe:Ce:Cu = 1.8:1:0.8), and add them to 250 mL of anhydrous ethanol. Stir magnetically at room temperature until the solids are completely dissolved to obtain a uniform transparent alkoxide solution;

[0047] Slowly add 10.0 g of aluminum nitride micropowder with an average particle size of 1 μm to the alkoxide solution (at this time, the solid-liquid ratio is about 1 g:25 mL), and perform ultrasonic dispersion treatment at 25°C for 30 minutes at a power of 300 W to make the solution fully infiltrate the powder pores to obtain a mixed suspension;

[0048] Place the mixed suspension in a rotary evaporator, and slowly evaporate the solvent under the conditions of a 60°C water bath and a vacuum degree of -0.08 MPa until no liquid flows out and the solid is in a dry and loose state to obtain a precursor dry powder;

[0049] Place the precursor dry powder in a tube furnace, and under the protection of a high-purity nitrogen gas stream with a flow rate of 300 mL / min, heat it to 300°C at a rate of 5°C / min and keep it at this temperature for 1.0 hour to make the nitrate decompose and form an oxide passivation layer in situ on the surface of the aluminum nitride. After cooling in the furnace, grind and sieve to obtain component A-1.

[0050] Preparation Example 2:

[0051] The present preparation example provides a surface passivated active thermal conductive precursor (component A-2), comprising the following steps:

[0052] Accurately weigh 29.1 g of iron nitrate nonahydrate, 17.4 g of cerium nitrate hexahydrate and 7.7 g of copper nitrate trihydrate (corresponding to the metal molar ratio Fe:Ce:Cu = 1.8:1:0.8), and add them to 250 mL of anhydrous ethanol. Stir magnetically at room temperature until the solids are completely dissolved to obtain a uniform transparent alkoxide solution;

[0053] The 10.0 g of aluminum nitride micropowder with an average particle size of 3 μm is slowly added into the alkoxide solution (at this time, the solid-liquid ratio is about 1 g:20 mL), and ultrasonic dispersion treatment is carried out at 25°C for 40 minutes at a power of 400 W, so that the solution fully infiltrates the powder pores, to obtain a mixed suspension;

[0054] The mixed suspension is placed in a rotary evaporator, and the solvent is slowly removed under the conditions of a water bath at 65°C and a vacuum degree of -0.085 MPa, until no liquid flows out and the solid is in a dry loose state, to obtain a dry powder of the precursor;

[0055] The dry powder of the precursor is placed in a tube furnace, and is heated to 325°C at a rate of 6°C / min under the protection of high-purity nitrogen gas flow at a flow rate of 400 mL / min and is kept for 1.5 hours, so that the nitrate is decomposed and an oxide passivation layer is formed in situ on the surface of the aluminum nitride, and after the furnace is cooled, the product is ground and sieved, to obtain component A-2.

[0056] Preparation Example 3:

[0057] The present preparation example provides a surface passivated active heat-conductive precursor (component A-3), comprising the following steps:

[0058] 45.3 g of iron nitrate nonahydrate, 22.2 g of cerium nitrate hexahydrate and 14.8 g of copper nitrate trihydrate (corresponding to a metal molar ratio of Fe:Ce:Cu=2.2:1:1.2) are accurately weighed and added into 150 mL of anhydrous ethanol, and are magnetically stirred at room temperature until the solids are completely dissolved, to obtain a uniform transparent alkoxide solution;

[0059] The 10.0 g of aluminum nitride micropowder with an average particle size of 5 μm is slowly added into the alkoxide solution (at this time, the solid-liquid ratio is about 1 g:15 mL), and ultrasonic dispersion treatment is carried out at 30°C for 45 minutes at a power of 500 W, so that the solution fully infiltrates the powder pores, to obtain a mixed suspension;

[0060] The mixed suspension is placed in a rotary evaporator, and the solvent is slowly removed under the conditions of a water bath at 70°C and a vacuum degree of -0.09 MPa, until no liquid flows out and the solid is in a dry loose state, to obtain a dry powder of the precursor;

[0061] The dry powder of the precursor is placed in a tube furnace, and is heated to 350°C at a rate of 8°C / min under the protection of high-purity nitrogen gas flow at a flow rate of 500 mL / min and is kept for 2.0 hours, so that the nitrate is decomposed and an oxide passivation layer is formed in situ on the surface of the aluminum nitride, and after the furnace is cooled, the product is ground and sieved, to obtain component A-3.

[0062] Examples 1-3:

[0063] Example 1:

[0064] The embodiment provides a method for removing phosphine by using active alumina adsorbent suitable for high-temperature environment, and comprises the following steps:

[0065] S1, 90 g of pseudo-boehmite, 4.0 g of light magnesium oxide, 3.0 g of zinc oxide powder and 1.5 g of boric acid (the molar ratio of Zn to B is about 1.5:1) are weighed and dry-mixed in a mechanical mixer for 15 minutes to obtain dry base powder with uniform mixing;

[0066] S2, 5 mL of reduced graphene oxide dispersion solution with a concentration of 0.5 wt% is sprayed into the dry base powder, and then 42 g of aluminum sol with a solid content of 15% (pH = 4.5) is slowly added, and glue dissolution kneading is carried out in a kneader for 20 minutes to make the boric acid and zinc oxide preliminarily react, and a low-acidity matrix paste with a pH value of 5.0 is obtained;

[0067] S3, 22 g of component A-1 (surface passivated active heat-conducting precursor) obtained in the preparation example 1 is added to the low-acidity matrix paste, and rapid secondary kneading is carried out for 10 minutes to uniformly disperse the passivated aluminum nitride particles in the matrix, and a composite adsorbent paste is obtained;

[0068] S4, the composite adsorbent paste is sent into a screw extruder, extruded into a strip with a diameter of 3 mm under a pressure of 2 MPa, and immediately sent into a blast drying oven after cutting, dried at 105 DEG C for 10 hours, and the water content is reduced to below 3% to obtain a dry green body;

[0069] S5, the dry green body is placed in an atmosphere sintering furnace, nitrogen gas with a flow rate of 1 L / min is introduced, first heated to 500 DEG C at a rate of 4 DEG C / min and kept for 1.5 hours to use the generated zinc-boron eutectic glass phase to wet the interface, then continuously heated to 600 DEG C at a rate of 2 DEG C / min and kept for 2.0 hours to complete the crystal transformation and structure solidification, and the active alumina adsorbent is obtained after the furnace is cooled;

[0070] S6, the active alumina adsorbent is packed in a fixed bed reactor, heated to an adsorption temperature of 180 DEG C under the protection of inert gas, and then industrial waste gas containing 100 ppm of phosphine (PH3) is introduced, and the volume space velocity of the gas is controlled to be 2000 h -1 , so that the phosphine is oxidized and converted into zinc phosphate and solidified in the pore channel of the adsorbent, thereby obtaining purified gas with a phosphorus content of less than 0.1 ppm.

[0071] Embodiment 2:

[0072] The embodiment provides a method for removing phosphine by using active alumina adsorbent suitable for high-temperature environment, and comprises the following steps:

[0073] S1, 100 g of pseudo-boehmite, 5.5 g of light magnesium oxide, 4.5 g of zinc oxide powder and 1.7 g of boric acid (the molar ratio of Zn to B is about 2.0:1) were weighed and dry-mixed in a mechanical mixer for 18 minutes to obtain a dry-mixed powder;

[0074] S2, 8 mL of a reduced graphene oxide dispersion solution with a concentration of 0.8 wt% was sprayed into the dry-mixed powder, and then 55 g of an aluminum sol with a solid content of 18% (pH = 4.0) was slowly added. The mixture was kneaded in a kneader for 25 minutes to preliminarily react the boric acid and zinc oxide, and a low-acidity matrix paste with a pH of 4.5 was obtained;

[0075] S3, 28 g of component A-2 (surface passivated active heat-conducting precursor) obtained in Preparation Example 2 was added to the low-acidity matrix paste, and rapid secondary kneading was performed for 12 minutes to uniformly disperse the passivated aluminum nitride particles in the matrix, and a composite adsorbent paste was obtained;

[0076] S4, the composite adsorbent paste was fed into a screw extruder and extruded into a 4 mm diameter strip under a pressure of 3 MPa. The strip was immediately cut and fed into a forced air drying oven, dried at 108°C for 11 hours, and the water content was reduced to below 2% to obtain a dry green body;

[0077] S5, the dry green body was placed in an atmosphere sintering furnace, and nitrogen gas with a flow rate of 1.5 L / min was introduced. First, the temperature was raised to 525°C at a rate of 4.5°C / min and held for 1.8 hours to wet the interface with the generated zinc-boron eutectic glass phase; then the temperature was raised to 625°C at a rate of 2.5°C / min and held for 2.5 hours to complete the crystal transformation and structure solidification. After cooling in the furnace, an active alumina adsorbent was obtained;

[0078] S6, the active alumina adsorbent was packed in a fixed bed reactor and heated to an adsorption temperature of 220°C under inert gas protection. Then, industrial waste gas containing 200 ppm of phosphine (PH3) was introduced, and the gas volume space velocity was controlled at 3000 h -1 The phosphine was oxidized and converted into zinc phosphate, which was solidified in the pores of the adsorbent, thereby obtaining purified gas with a phosphorus content of less than 0.1 ppm.

[0079] Example 3:

[0080] The present embodiment provides a method for removing phosphine from an active alumina adsorbent suitable for high temperature environments, comprising the following steps:

[0081] S1, 110 g of pseudo-boehmite, 7.0 g of light magnesium oxide, 6.0 g of zinc oxide powder and 1.8 g of boric acid (the molar ratio of Zn to B is about 2.5:1) were weighed and dry-mixed in a mechanical mixer for 20 minutes to obtain a dry base powder with uniform mixing;

[0082] S2, 10 mL of a reduced graphene oxide dispersion solution with a concentration of 1.0 wt% was sprayed into the dry base powder, followed by the slow addition of 68 g of an aluminum sol with a solid content of 20% (pH = 3.5). The mixture was subjected to a peptizing kneading process in a kneader for 30 minutes to allow the boric acid and zinc oxide to react preliminarily, thereby obtaining a low-acidity matrix paste with a pH value of 4.0;

[0083] S3, 35 g of component A-3 (surface passivated active heat-conductive precursor) obtained in Preparation Example 3 was added to the low-acidity matrix paste, and the mixture was subjected to a rapid secondary kneading process for 15 minutes to uniformly disperse the passivated aluminum nitride particles in the matrix, thereby obtaining a composite adsorbent paste;

[0084] S4, the composite adsorbent paste was fed into a screw extruder and extruded into a strip with a diameter of 5 mm under a pressure of 4 MPa. The strip was immediately cut and fed into a forced-air drying oven for drying at 110°C for 12 hours to reduce the water content to below 1.5%, thereby obtaining a dry green body;

[0085] S5, the dry green body was placed in an atmosphere sintering furnace and a nitrogen gas with a flow rate of 2 L / min was introduced. The temperature was first raised to 550°C at a rate of 5°C / min and maintained for 2.0 hours to utilize the generated zinc-boron eutectic glass phase to wet the interface. Then the temperature was continuously raised to 650°C at a rate of 3°C / min and maintained for 3.0 hours to complete the crystal transformation and structure solidification. After cooling in the furnace, an active alumina adsorbent was obtained;

[0086] S6, the active alumina adsorbent was packed in a fixed-bed reactor and heated to an adsorption temperature of 260°C under inert gas protection. Then an industrial waste gas containing 300 ppm of phosphine (PH3) was introduced, and the gas volume space velocity was controlled at 4000 h-1. The phosphine was oxidized and converted into zinc phosphate, which was solidified in the pores of the adsorbent, thereby obtaining a purified gas with a phosphorus content of less than 0.1 ppm. -1

[0087] Comparative Examples 1-5:

[0088] Comparative Example 1:

[0089] Comparative Example 2:

[0090] Comparative Example 2: ​

[0091] Compared with Example 2, the difference is that in step S1, zinc oxide powder and boric acid were not added, and in step S2, the amount of boehmite was increased accordingly to make up for the solid content. The remaining steps and parameters are the same.

[0092] Comparative Example 3:

[0093] Compared with Example 2, the difference is that in step S2, a 5wt% dilute nitric acid solution is used instead of aluminum sol as the adhesive solvent, while the other steps and parameters are the same.

[0094] Comparative Example 4:

[0095] Compared with Example 2, the difference is that component A-2 was not prepared in advance. Specifically, all the raw materials required to prepare component A-2 (ferric nitrate, cerium nitrate, copper nitrate, aluminum nitride micro powder) were directly mixed with the matrix raw materials such as boehmite and magnesium oxide in step S1 in one step, and the remaining steps and parameters were the same.

[0096] Comparative Example 5:

[0097] Compared with Example 2, the difference is that in step S1, only boric acid was added, and zinc oxide powder was not added, while the other steps and parameters were the same.

[0098] Test Example 1-3:

[0099] Test Example 1: Mechanical Strength Test (Lateral Compression Strength);

[0100] The radial lateral compressive strength of each group of samples was determined using a particle strength tester (model: DL-3). The test was conducted according to the chemical industry standard HG / T 2782-2011 "Determination of Crushing Resistance of Fertilizer Catalyst Particles". Twenty intact particles with a length of 5mm to 8mm were randomly selected from the test samples and placed in a 120℃ environment for 2 hours to eliminate the influence of humidity. Each sample was placed horizontally between the upper and lower pressure plates of the tester, keeping the particle axis parallel to the pressure plates. The instrument was started and a vertical load was applied at a rate of 5N / s until the particle fractured. The pressure value was recorded. The arithmetic mean and standard deviation of the 20 sets of data were calculated.

[0101] Table 1. Statistical analysis of radial lateral pressure strength test data for each group of samples.

[0102]

[0103] Results Analysis and Conclusions:

[0104] The data in Table 1 shows that the lateral strength of the example group is higher than that of each of the comparative examples, wherein the average strength of Example 2 reaches 121.8 N / pellet. Comparing Example 2 with Comparative Example 1, the anhydrous solvent system maintains the integrity of the skeleton. Comparative Example 1 uses water as the solvent, and aluminum nitride undergoes a hydrolysis reaction to generate aluminum hydroxide and ammonia gas. The gas escapes to form micropores inside the particles, and the aluminum hydroxide shrinks in volume when dehydrated during subsequent sintering, resulting in an average strength of 32.5 N / pellet. The examples retain the aluminum nitride phase and maintain structural strength through anhydrous ethanol loading and surface passivation.

[0105] Comparative Example 3 uses dilute nitric acid peptization, and the average strength is 54.7 N / pellet. The free strong acid environment corrodes aluminum nitride, and the gas generated by the reaction causes pores and cracks to appear inside the matrix during the dry sintering stage. The examples use aluminum sol neutral bonding to reduce the generation of internal gas and ensure matrix density.

[0106] The strength of the example group is higher than that of Comparative Examples 2 and 5, indicating that the liquid phase formed by the zinc-boron system promotes low-temperature sintering. In the 500-550°C range, the zinc-boron eutectic glass phase fills the gaps between the aluminum oxide particles, and after cooling, it forms a glass phase bond, improving the particle's compression resistance. Comparative Example 5 contains only boron oxide, lacks the mineralization effect of zinc ions, and the structural strength after solidification is lower than that of the zinc-boron system. Comparative Example 4 is prepared using a mixing method, and the metal components are randomly distributed, without forming a core-shell structure. The interface bonding force is weaker than the chemical bond interface formed by pre-loading in the examples, and the strength is lower than that of Example 2.

[0107] Test Example 2: High-temperature phosphine removal performance test (penetration phosphorus capacity);

[0108] The experiment uses a stainless steel fixed-bed micro-reactor. 5.0 g of adsorbent sample with a particle size of 3-5 mm is packed in the constant temperature section of a reaction tube with an inner diameter of 20 mm, and quartz sand is filled at both ends of the bed. Under a high-purity nitrogen flow of 50 mL / min, the reactor is heated to 200°C and maintained for 30 minutes. Switch the gas path to input simulated waste gas, with a gas composition of 200 ppm phosphine (PH3), 1.0 vol% oxygen (O2), and nitrogen as the balance gas. The gas hourly space velocity (GHSV) is controlled at 3000 h -1 -1. The outlet phosphine concentration is monitored using a gas chromatograph (FPD detector), and the experiment is stopped when the outlet concentration reaches 5% of the inlet concentration (10 ppm). The penetration phosphorus capacity of the unit mass of adsorbent is calculated based on the penetration time, flow rate, and inlet concentration. The unit of penetration phosphorus capacity is mg / g (i.e., milligrams of phosphorus per gram of adsorbent)

[0109] Table 2. Penetration phosphorus capacity test data of each group of samples at 200°C

[0110]

[0111] Results Analysis and Conclusions:

[0112] Table 2 shows that the phosphorus penetration capacity of Example 2 is 192.4 mg / g, which is higher than that of the comparative examples. High-temperature adsorption for phosphorus removal is limited by product layer diffusion and reaction heat accumulation. The influence of each component on adsorption performance is analyzed as follows:

[0113] Comparative Example 1 had a phosphorus content of 43.2 mg / g. The aqueous solvent caused aluminum nitride hydrolysis during the preparation process, which destroyed the skeletal structure. The hydrolysis products covered the active sites, reduced the effective specific surface area, and hindered gas diffusion into the particle interior.

[0114] Comparative Example 2 showed a phosphorus capacity of 92.1 mg / g, which was affected by the pore blockage effect. The phosphorus pentoxide and metaphosphoric acid generated by phosphating and oxidizing were in a high-viscosity gel state at 200℃, covering the surface of alumina and blocking the micropores, thus blocking the diffusion channels of the reactant gas into the interior, resulting in low internal utilization of the adsorbent.

[0115] The example group introduced a zinc-boron phase transfer agent to improve diffusion restriction. The P2O5 generated in the reaction reacted chemically with pre-dispersed zinc metaborate to transform into high-melting-point, crystalline zinc phosphate or zinc borophosphate. This process altered the product phase state, disrupted the dense P2O5 capping layer, and the product crystallization contraction exposed new active metal sites. Comparative Example 5 contained only boric acid, lacking zinc ions to form a stable crystalline product, resulting in weak product film reconstruction ability and a lower phosphorus capacity than the examples.

[0116] Comparative Example 4 was prepared using a mixing method, with a phosphorus capacity of 124.6 mg / g. Phosphate oxidation is an exothermic reaction; localized heat accumulation leads to sintering and deactivation of the active component. In this example, the active component was pre-loaded onto the aluminum nitride surface. The high thermal conductivity of aluminum nitride facilitates the transfer of reaction heat to the matrix framework, suppressing localized overheating, maintaining the dispersion of the active component, and prolonging the breakthrough time.

[0117] Test Example 3: Regeneration Stability Test (Lifetime Retention Rate);

[0118] Samples from test item two that had reached adsorption saturation were placed in a tubular regeneration furnace and heated to 250°C at a rate of 5°C / min under a nitrogen atmosphere, then held at that temperature for 4 hours. The high temperature induced a phase transition in the adsorbed products within the pores, removing physically adsorbed impurities. After cooling to room temperature in the furnace, the samples were reloaded into a fixed-bed reactor and tested at a temperature of 200°C and a space velocity of 3000 h⁻¹. -1 A second adsorption breakthrough experiment was conducted under the condition of an inlet air concentration of 200 ppm PH3, and the breakthrough phosphorus capacity was recorded. The above "adsorption regeneration" process was repeated 5 times, and the capacity retention rate after the 5th cycle was calculated based on the breakthrough phosphorus capacity of the 1st cycle.

[0119] Table 3. Capacity retention data of each group of samples after 5 adsorption-regeneration cycles.

[0120]

[0121] Results analysis and conclusion:

[0122] Table 3 shows that the capacity retention of Example 2 is 87.4% after 5 cycles of adsorption and regeneration, while the capacity retention of Comparative Example 2 and Comparative Example 4 is 32.1% and 61.5%, respectively. The stability in multi-cycle operation depends on the phase evolution of the adsorbed product and the thermal stability of the active components.

[0123] Comparative Example 2, which does not contain a sacrificial phase, shows a significant capacity decay. The phosphine oxidation product is mainly amorphous polyphosphate or phosphorus pentoxide glass. Under the high-temperature environment of regeneration and secondary adsorption, such substances soften and flow under heat, covering the unreacted active sites and pore throats, causing pore blockage. As the number of cycles increases, the accumulated glass phase material blocks the adsorbent pores, resulting in a decrease in adsorption capacity.

[0124] The high retention rate of the example group confirms the anti-clogging mechanism of the zinc-boron sacrificial phase. Under the dual action of adsorption heat release and regeneration heat treatment, the pre-dispersed zinc-boron species can induce mineralization of amorphous phosphorus oxides, gradually converting them into structurally dense zinc phosphate or zinc borophosphate solid solutions. This process causes the volume of the original fluffy product layer to shrink and solidify, creating microcracks and secondary pores inside the deposited layer, effectively reducing the mass transfer resistance and reopening the channels for gas molecules to diffuse to the deep active sites.

[0125] The capacity retention of Comparative Example 4 is 61.5%, which decays due to the thermal sintering of active components. In the repeated heat release adsorption and heating regeneration process, the alumina matrix lacks effective heat conduction channels, and local heat accumulation leads to the agglomeration of the loaded iron / cerium / copper oxides, reducing the active specific surface area. The example uses surface-passivated aluminum nitride as a heat-conducting skeleton to quickly dissipate reaction heat, inhibit the agglomeration of active metal particles, and maintain the dispersion and stability of active centers.

Claims

1. A method for removing phosphine using activated alumina adsorbent suitable for high-temperature environments, characterized in that, Includes the following steps: S1. By weight, mix 90-110 parts of pseudoboehmite, 4.0-7.0 parts of light magnesium oxide, 3.0-6.0 parts of zinc oxide powder and 1.5-1.8 parts of boric acid to obtain a dry-based powder. S2. Add 5-10 parts of reduced graphene oxide dispersion and 42-68 parts of aluminum sol to the dry base powder, and perform sol-kneading to obtain low acidity matrix mud. S3. Add 22-35 parts of surface passivation type active thermal conductive precursor to the low acidity matrix mud, and knead it a second time to obtain composite adsorbent paste; the surface passivation type active thermal conductive precursor is aluminum nitride particles with Fe-Ce-Cu composite metal oxide layer loaded on the surface. The surface-passivated active thermally conductive precursor is prepared by a method comprising the following steps: A solution was prepared by dissolving ferric nitrate nonahydrate, cerium nitrate hexahydrate, and copper nitrate trihydrate in anhydrous ethanol, wherein the molar ratio of Fe:Ce:Cu was (1.8-2.2):1:(0.8-1.2). Add aluminum nitride micro powder with a particle size of 1-5 μm to the above solution, control the solid-liquid ratio to 1 g:(15-25) mL, and ultrasonically disperse for 30-45 minutes under a power of 300-500 W. The anhydrous ethanol was removed by rotary evaporation at a temperature of 60-70℃ and a vacuum of -0.08MPa to -0.09MPa to obtain the precursor dry powder. The precursor powder was heated to 300-350°C at a heating rate of 5-8°C / min under an inert atmosphere and a gas flow rate of 300-500 mL / min, and held at that temperature for 1.0-2.0 hours. S4. The composite adsorbent paste is shaped and dried to obtain a dried green body; S5. The dried green blank is sintered in sections under an inert atmosphere, and the activated alumina adsorbent is obtained after cooling. S6. The activated alumina adsorbent is packed into the reactor and heated to the adsorption temperature under inert gas protection. Industrial waste gas containing 1-500 ppm phosphine is introduced, and the gas volume hourly space velocity is controlled at 2000-4000 h⁻¹. -1 .

2. The method for removing phosphine using activated alumina adsorbent suitable for high-temperature environments according to claim 1, characterized in that, In step S1, the amount of zinc oxide and boric acid fed in the feed satisfies the molar ratio of Zn to B being 1.5:1 to 2.5:1; in step S2, the solid content of the aluminum sol is 15%-20% and the pH value is 3.5-4.5; the concentration of the reduced graphene oxide dispersion is 0.5wt%-1.0wt%.

3. The method for removing phosphine using activated alumina adsorbent suitable for high-temperature environments according to claim 1, characterized in that, In step S6, the adsorption temperature is 180℃-260℃.

4. The method for removing phosphine using activated alumina adsorbent suitable for high-temperature environments according to claim 1, characterized in that, In step S5, the process parameters for segmented sintering are as follows: The nitrogen flow rate is 1-2 L / min; First stage: Increase the temperature to 500-550℃ at a heating rate of 4-5℃ / min, and hold for 1.5-2.0 hours; Second stage: Continue heating at a rate of 2-3℃ / min to 600-650℃, and hold for 2.0-3.0 hours.

5. The method for removing phosphine using activated alumina adsorbent suitable for high-temperature environments according to claim 1, characterized in that, In step S2, the gel kneading time is 20-30 minutes, and the pH value of the low acidity matrix mud after kneading is 4.0-5.

0.

6. The method for removing phosphine using activated alumina adsorbent suitable for high-temperature environments according to claim 4, characterized in that, In step S4, the molding pressure is 2-4 MPa, and the diameter of the extruded material is 3-5 mm.

7. The method for removing phosphine using activated alumina adsorbent suitable for high-temperature environments according to claim 4, characterized in that, In step S4, the drying temperature is 105-110℃, the drying time is 10-12 hours, and the drying is carried out until the moisture content is less than 3%.

8. The method for removing phosphine using activated alumina adsorbent suitable for high-temperature environments according to claim 1, characterized in that, In step S1, the mixing time is 15-20 minutes; in step S3, the second kneading time is 10-15 minutes.

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