A vanadium-inhibiting metal passivating agent for catalytic cracking units and its application

Abstract

This invention provides a vanadium-inhibiting metal passivating agent for catalytic cracking units and its application, relating to the field of industrial refining technology; it includes core-shell structured particles and bifunctional organic ligands; wherein, the core-shell structured particles include a barium titanate core and a lanthanum oxide-magnesium oxide composite oxide shell, and the bifunctional organic ligands include strong coordinating groups and hydrophilic segments; nanoparticles with barium titanate as the core and lanthanum magnesium oxide as the shell are constructed by the sol-gel method, and then supplemented with specially designed bifunctional organic ligands, achieving a breakthrough improvement in vanadium capture efficiency and dispersibility. Barium titanate selectively captures vanadium to form a stable Ba3V2O8 phase, lanthanum oxide constructs a high-melting-point LaVO4 barrier layer, and magnesium oxide creates an alkaline microenvironment to inhibit vanadate formation.

Description

Technical Field

[0001] This invention relates to the field of industrial refining technology, and in particular to a vanadium-inhibiting metal passivating agent for catalytic cracking units and its application. Background Technology

[0002] Catalytic cracking, as a core process in modern oil refining, faces severe challenges due to the increasing weight of feedstocks. Vanadium metal components enriched in residual oil feedstocks cause irreversible damage to molecular sieve catalysts during the reaction-regeneration process, leading to decreased catalyst activity, reduced light oil yield, and increased hydrogen and coke production.

[0003] While significant progress has been made in the research and application of vanadium-inhibiting passivators for catalytic cracking, many technical bottlenecks still need to be overcome. Mainstream passivators mainly rely on rare earth elements (such as lanthanum and cerium) or metallic antimony as active components. However, single rare earth systems have obvious limitations in high-temperature regeneration environments (>700℃)—the formation rate of LaVO4 is diffusion-controlled, making it difficult to completely fix high concentrations of vanadium in a short time. More importantly, when the vanadium deposited on the catalyst surface exceeds 5000 ppm, the efficiency of rare earth passivators drops sharply.

[0004] Current understanding of vanadium degradation mechanisms focuses on two aspects: first, the low melting point (690℃) of vanadium pentoxide (V2O5) causes it to melt in the high-temperature environment of the regenerator, clogging the catalyst channels; second, vanadic acid (H3VO4) causes acidic hydrolysis damage to the molecular sieve framework. However, current passivating agents are designed for only one of these mechanisms, and currently, highly efficient passivating agents often contain toxic metals such as antimony and lead, posing environmental risks. Summary of the Invention

[0005] The purpose of this invention is to provide a vanadium-inhibiting metal passivating agent for catalytic cracking equipment and its application, thereby achieving at least a partial solution to the above-mentioned problems.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a vanadium-inhibiting metal passivating agent for catalytic cracking units, comprising core-shell structured particles and bifunctional organic ligands;

[0007] The core-shell structured particles comprise a barium titanate core and a lanthanum oxide-magnesium oxide composite oxide shell, and the bifunctional organic ligand comprises a strong coordinating group and a hydrophilic segment.

[0008] Furthermore, the particle size of the core-shell structure particles is 80-100 nm, the particle size of the barium titanate core is 55-65 nm, and the thickness of the lanthanum oxide-magnesium oxide composite oxide shell is 15-35 nm.

[0009] The molar ratio of lanthanum to magnesium in the lanthanum oxide-magnesium oxide composite oxide shell is 2:3.

[0010] Furthermore, the strong coordinating group includes α-hydroxysuccinic acid, and the hydrophilic segment includes triethanolamine and acrylamide;

[0011] The mass ratio of the bifunctional ligand to the core-shell structured particles is (0.55-0.65):1.

[0012] Furthermore, the preparation of the vanadium metal passivating agent includes the following steps:

[0013] Tetrabutyl titanate and barium hydroxide were dissolved in deionized water, and citric acid was added as a complexing agent to carry out a hydrothermal reaction. The precipitate was then collected by centrifugation, and the collected precipitate was washed and dried to obtain the barium titanate core.

[0014] The barium titanate core was dispersed in an ethanol-water mixed solvent, and a coating solution containing lanthanum nitrate and magnesium nitrate was added dropwise while ammonia was added dropwise to maintain the pH value at 9.3-9.7. After aging, the solid product was separated by centrifugation and then calcined to obtain core-shell structured particles.

[0015] After reacting α-hydroxysuccinic acid with triethanolamine under nitrogen protection, acrylamide was added to continue the reaction to obtain a bifunctional ligand.

[0016] Core-shell nanoparticles were dispersed in deionized water, a bifunctional ligand was added, and after ultrasonic treatment, the particles were stirred, dialyzed and spray-dried in sequence to obtain modified powder.

[0017] The modified powder was mixed with deionized water, and rheology modifiers and antioxidants were added. The mixture was then subjected to high-pressure homogenization to obtain a vanadium-inhibiting metal passivating agent.

[0018] Furthermore, the hydrothermal reaction is carried out at a temperature of 195-205℃ for 11-13 hours, and the molar ratio of titanium to barium in the tetrabutyl titanate and barium hydroxide is 1:(1.05-1.15).

[0019] Furthermore, in the ethanol-water mixed solvent, the volume ratio of ethanol to water is 3:1, the calcination temperature is 590-610℃, and the calcination time is 3h.

[0020] The ultrasonic treatment has a power of 550-650W, a frequency of 38-42kHz, and a treatment time of 25-35min. During the addition of the coating liquid, the mixture is continuously stirred at a speed of not less than 800rpm.

[0021] Furthermore, α-hydroxysuccinic acid and triethanolamine were reacted under nitrogen protection at a temperature of 115-125℃ for 3.5-4.5 h, and then acrylamide was added to continue the reaction at a temperature of 115-125℃ for 1.5-2.5 h.

[0022] Furthermore, the stirring process is carried out at a constant temperature of 68-72℃ for 5.5-6.5 hours.

[0023] The mass ratio of the modified powder to deionized water is (12-13):(37-38), and the pressure of the high-pressure homogenization treatment is 140-160 MPa.

[0024] Furthermore, the rheology modifier includes hydroxyethyl cellulose, and the amount of the rheology modifier added is 0.4-0.6 wt%, and the antioxidant includes butylated hydroxytoluene, and the amount of the antioxidant added is 0.9-1.1 wt%.

[0025] On the other hand, the present invention also provides an application of a vanadium-inhibiting metal passivating agent for a catalytic cracking unit, characterized in that the above-mentioned vanadium-inhibiting metal passivating agent is used to inhibit vanadium contamination during the catalytic cracking process.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] This invention constructs nanoparticles with barium titanate as the core and lanthanum magnesium oxide as the shell using the sol-gel method, and then supplements them with specially designed bifunctional organic ligands, achieving a breakthrough improvement in vanadium capture efficiency and dispersibility. Barium titanate selectively captures vanadium to form a stable Ba3V2O8 phase, lanthanum oxide constructs a high-melting-point LaVO4 barrier layer, and magnesium oxide creates an alkaline microenvironment to inhibit the formation of vanadate. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0029] This invention provides a vanadium-inhibiting metal passivating agent for catalytic cracking units, comprising core-shell structured particles and bifunctional organic ligands;

[0030] The core-shell structured particles comprise a barium titanate core and a lanthanum oxide-magnesium oxide composite oxide shell, and the bifunctional organic ligand comprises a strong coordinating group and a hydrophilic segment.

[0031] In a further embodiment of this example, the particle size of the core-shell structure particles is 80-100 nm, the particle size of the barium titanate core is 55-65 nm, and the thickness of the lanthanum oxide-magnesium oxide composite oxide shell is 15-35 nm.

[0032] The molar ratio of lanthanum to magnesium in the lanthanum oxide-magnesium oxide composite oxide shell is 2:3.

[0033] In a further embodiment of this example, the strong coordinating group includes α-hydroxysuccinic acid, and the hydrophilic segment includes triethanolamine and acrylamide;

[0034] The mass ratio of the bifunctional ligand to the core-shell structured particles is (0.55-0.65):1, which ensures that the ligand forms a stable monolayer on the surface of the core-shell structured particles, effectively achieving stable dispersion and directional deposition of the core-shell structured particles. If the ratio is too low, the particles cannot be fully coated, and if it is too high, the ligand may accumulate excessively, affecting the performance of the passivating agent.

[0035] In a further embodiment of this example, the preparation of the vanadium-inhibiting metal passivating agent includes the following steps:

[0036] Tetrabutyl titanate and barium hydroxide were dissolved in deionized water, and citric acid was added as a complexing agent to carry out a hydrothermal reaction. The precipitate was then collected by centrifugation, and the collected precipitate was washed and dried to obtain the barium titanate core.

[0037] The barium titanate core was dispersed in an ethanol-water mixed solvent, and a coating solution containing lanthanum nitrate and magnesium nitrate was added dropwise while ammonia was added dropwise to maintain the pH value at 9.3-9.7. After aging, the solid product was separated by centrifugation and then calcined to obtain core-shell structured particles.

[0038] After reacting α-hydroxysuccinic acid with triethanolamine under nitrogen protection, acrylamide was added to continue the reaction to obtain a bifunctional ligand.

[0039] Core-shell nanoparticles were dispersed in deionized water, a bifunctional ligand was added, and after ultrasonic treatment, the particles were stirred, dialyzed and spray-dried in sequence to obtain modified powder.

[0040] The modified powder was mixed with deionized water, and rheology modifiers and antioxidants were added. The mixture was then subjected to high-pressure homogenization to obtain a vanadium-inhibiting metal passivating agent.

[0041] In a further embodiment of this example, the hydrothermal reaction is carried out at a temperature of 195-205℃ for 11-13 hours. The molar ratio of titanium to barium in the tetrabutyl titanate and barium hydroxide is 1:(1.05-1.15), which ensures the formation of regular cubic phase and barium titanate nanonuclei with the required particle size. Deviations in temperature and time will affect the crystal structure and particle size. This ensures the full synthesis of barium titanate. An improper ratio will lead to the formation of impurities.

[0042] In a further embodiment of this example, the volume ratio of ethanol to water in the ethanol-water mixed solvent is 3:1, the calcination temperature is 590-610℃, and the calcination time is 3h. This is beneficial for the dispersion of barium titanate nanonuclei and the subsequent shell coating reaction. An improper ratio will affect the dispersion effect and reaction uniformity.

[0043] The ultrasonic treatment has a power of 550-650W, a frequency of 38-42kHz, and a treatment time of 25-35min. During the addition of the coating liquid, it is under continuous stirring conditions with a stirring speed of not less than 800rpm, which can effectively disperse the core-shell nanoparticles and facilitate full contact between the ligands and the particles. Inappropriate parameters will affect the dispersion effect and subsequent modification reaction.

[0044] In a further embodiment of this example, α-hydroxysuccinic acid and triethanolamine are reacted under nitrogen protection at a temperature of 115-125°C for 3.5-4.5 hours, and then acrylamide is added and the reaction is continued at 115-125°C for 1.5-2.5 hours. This ensures the successful synthesis and performance of the ligand. Improper temperature and time will affect the structure and function of the ligand.

[0045] In a further embodiment of this example, the stirring process is carried out at a constant temperature of 68-72℃ for 5.5-6.5 hours to ensure that the bifunctional ligands are fully bonded to the surface of the nanoparticles. Inappropriate temperature and time will affect the anchoring effect of the ligands.

[0046] The mass ratio of the modified powder to deionized water is (12-13):(37-38), which ensures that the solid content of the passivating agent is within a suitable range and meets the usage requirements. The pressure of the high-pressure homogenization treatment is 140-160MPa, which makes the passivating agent form a uniform and stable liquid. Insufficient pressure will result in poor dispersion effect, while excessive pressure may increase energy consumption and equipment wear.

[0047] In a further embodiment of this example, the rheology modifier includes hydroxyethyl cellulose, and the amount of the rheology modifier added is 0.4-0.6 wt%, and the antioxidant includes butylated hydroxytoluene, and the amount of the antioxidant added is 0.9-1.1 wt%.

[0048] It should be noted that barium titanate, as the core functional unit, contains exchangeable barium ions in its crystal structure, which can react with vanadium oxide to form a thermodynamically stable Ba3V2O8 phase. Barium titanate has an affinity for vanadium that is more than three times that of traditional alumina, and it can still maintain its structural integrity under high vanadium pollution of 6000ppm. Furthermore, barium titanate has high stability in high-temperature hydrothermal environments.

[0049] Using lanthanum oxide-magnesium oxide composite oxide as the shell, lanthanum oxide, as the main passivating vanadium component, forms high-melting-point lanthanum vanadate with vanadium, effectively isolating vanadium from the molecular sieve. The introduction of magnesium oxide brings dual benefits: first, it provides an alkaline microenvironment to neutralize acidic species (such as H3VO4) generated by vanadium oxidation, inhibiting their hydrolytic damage to the molecular sieve framework; second, it acts as an "isolation layer" to prevent the core barium titanate from reacting adversely with the catalyst matrix at high temperatures.

[0050] Stable dispersion and directional deposition of nanoparticles are achieved by using bifunctional organic ligands with α-hydroxycarboxylic acid groups and alkanolamine segments. Through the synergistic coordination of hydroxyl and carboxyl groups, chelate bonds are formed with metal atoms on the surface of nanoparticles. The alkanolamine segments provide water solubility and enhance the affinity with the catalyst surface, so that the passivating agent forms a homogeneous aqueous solution at room temperature. In the high-temperature environment of the catalytic cracking reactor, the ligands gradually decompose and release active nanoparticles.

[0051] The core-shell structure described above prevents premature reaction between the core and poisons because the shell preferentially contacts vanadium. Furthermore, the shell can prevent the agglomeration of barium titanate during preparation and storage. Vanadium species diffuse from the shell to the core, while limiting the escape of molecular sieve fragments.

[0052] The core barium titanate captures vanadium through ion exchange to form the stable Ba3V2O8 phase, while the shell lanthanum oxide combines with vanadium to form the high-melting-point LaVO4 barrier. Magnesium oxide creates an alkaline microenvironment to inhibit the formation of vanadate.

[0053] The core-shell structure particles have a diameter of 80-100 nm because this size range ensures good dispersion, avoids agglomeration, and facilitates uniform distribution on the catalyst surface. If the particle size is too large, it will easily lead to uneven dispersion, while if it is too small, it may agglomerate due to excessive surface energy. Among them, the barium titanate core has a particle size of 55-65 nm. Within this particle size range, the core has enough space for vanadium capture reaction, and it matches the shell thickness to maintain the stability of the core-shell structure. The thickness of the lanthanum oxide-magnesium oxide composite oxide shell is 15-35 nm. Within this thickness range, it can effectively achieve preferential contact with vanadium, protect the core, and perform cascade passivation. If it is too thin, it will be difficult to form an effective barrier and provide a sufficient alkaline environment, while if it is too thick, it may hinder the diffusion of vanadium to the core.

[0054] In the lanthanum oxide-magnesium oxide composite oxide, the molar ratio of lanthanum to magnesium is 2:3. This ratio allows for an optimal balance between the two mechanisms: lanthanum oxide forming a high-melting-point LaVO4 barrier layer and magnesium oxide creating an alkaline microenvironment to inhibit vanadate formation. A ratio that is too high or too low will weaken the effect of one of these mechanisms.

[0055] On the other hand, the present invention also provides an application of a vanadium-inhibiting metal passivating agent for a catalytic cracking unit, characterized in that the above-mentioned vanadium-inhibiting metal passivating agent is used to inhibit vanadium contamination during the catalytic cracking process.

[0056] Example 1

[0057] Synthesis of monodisperse barium titanate particles: Tetrabutyl titanate and barium hydroxide were dissolved in deionized water, with a molar ratio of tetrabutyl titanate to barium hydroxide of 1.10:1, to form a precursor solution. 0.05 mol / L citric acid was added as a complexing agent to prevent premature precipitation of titanium species. The solution was transferred to a high-pressure reactor and hydrothermally reacted at 195 °C for 12 hours. The white precipitate was collected by centrifugation, washed three times with ethanol, and dried under vacuum at 80 °C. The resulting barium titanate nanoparticles were in a regular cubic phase with an average particle size of 55 nm.

[0058] Lanthanum oxide-magnesium oxide shell coating: Barium titanate particles were dispersed in an ethanol-water mixed solvent to prepare a coating solution containing lanthanum nitrate and magnesium nitrate. The coating solution was added dropwise to the barium titanate particle suspension under vigorous stirring at 800 rpm, while ammonia was added dropwise to maintain pH=9.5 to promote the co-precipitation of hydroxides. After aging for 12 hours, the solid product was separated by centrifugation and calcined in a muffle furnace at 590℃ for 3 hours to convert the hydroxides into an oxide composite shell. The amount of coating solution added was controlled to form a 25 nm shell.

[0059] Bifunctional ligand synthesis: α-hydroxysuccinic acid and triethanolamine were added to a reaction vessel, heated to 120°C, and reacted for 4 hours under nitrogen protection. Then acrylamide was added, and the reaction was continued for 2 hours. The temperature was then lowered to 60°C to obtain an amber viscous liquid.

[0060] Nanoparticle surface modification: Core-shell structured particles were dispersed in deionized water, and bifunctional ligands were added, wherein the mass ratio of bifunctional ligands to core-shell structured particles was 0.55:1. The particles were ultrasonically treated at 600W and 40kHz for 30 min, and then stirred at 70℃ for 6 h to complete ligand anchoring. Free ligands were removed by dialysis, and the modified nanoparticles were obtained by spray drying.

[0061] Passivating agent compounding and molding: Modified nanoparticles and deionized water are mixed at a mass ratio of 25:75, 0.5wt% hydroxyethyl cellulose is added as a rheology modifier, and 1wt% butyl hydroxytoluene is added as an antioxidant. After high pressure homogenization, the passivating agent product is obtained.

[0062] Example 2

[0063] Synthesis of monodisperse barium titanate particles: Tetrabutyl titanate and barium hydroxide were dissolved in deionized water, with a molar ratio of tetrabutyl titanate to barium hydroxide of 1.10:1, to form a precursor solution. 0.05 mol / L citric acid was added as a complexing agent to prevent premature precipitation of titanium species. The solution was transferred to a high-pressure reactor and hydrothermally reacted at 200℃ for 12 hours. The white precipitate was collected by centrifugation, washed three times with ethanol, and dried under vacuum at 80℃. The resulting barium titanate nanoparticles were in a regular cubic phase with an average particle size of 60 nm.

[0064] Lanthanum oxide-magnesium oxide shell coating: Barium titanate particles were dispersed in an ethanol-water mixed solvent to prepare a coating solution containing lanthanum nitrate and magnesium nitrate. The coating solution was added dropwise to the barium titanate particle suspension under vigorous stirring at 800 rpm, while ammonia was added dropwise to maintain pH=9.5 to promote the co-precipitation of hydroxides. After aging for 12 hours, the solid product was separated by centrifugation and calcined in a muffle furnace at 600℃ for 3 hours to convert the hydroxides into an oxide composite shell. The amount of coating solution added was controlled to form a 30 nm shell.

[0065] Bifunctional ligand synthesis: α-hydroxysuccinic acid and triethanolamine were added to a reaction vessel, heated to 120°C, and reacted for 4 hours under nitrogen protection. Then acrylamide was added, and the reaction was continued for 2 hours. The temperature was then lowered to 60°C to obtain an amber viscous liquid.

[0066] Nanoparticle surface modification: Core-shell structured particles were dispersed in deionized water, and bifunctional ligands were added, wherein the mass ratio of bifunctional ligands to core-shell structured particles was 0.6:1. The particles were ultrasonically treated at 600W and 40kHz for 30 min, and then stirred at 70℃ for 6 h to complete ligand anchoring. Free ligands were removed by dialysis, and the modified nanoparticles were obtained by spray drying.

[0067] Passivating agent compounding and molding: Modified nanoparticles and deionized water are mixed at a mass ratio of 25:75, 0.5wt% hydroxyethyl cellulose is added as a rheology modifier, and 1wt% butyl hydroxytoluene is added as an antioxidant. After high pressure homogenization, the passivating agent product is obtained.

[0068] Example 3

[0069] Synthesis of monodisperse barium titanate particles: Tetrabutyl titanate and barium hydroxide were dissolved in deionized water, with a molar ratio of tetrabutyl titanate to barium hydroxide of 1.10:1, to form a precursor solution. 0.05 mol / L citric acid was added as a complexing agent to prevent premature precipitation of titanium species. The solution was transferred to a high-pressure reactor and hydrothermally reacted at 205 °C for 12 hours. The white precipitate was collected by centrifugation, washed three times with ethanol, and dried under vacuum at 80 °C. The resulting barium titanate nanoparticles were in a regular cubic phase with an average particle size of 65 nm.

[0070] Lanthanum oxide-magnesium oxide shell coating: Barium titanate particles were dispersed in an ethanol-water mixed solvent to prepare a coating solution containing lanthanum nitrate and magnesium nitrate. The coating solution was added dropwise to the barium titanate particle suspension under vigorous stirring at 800 rpm, while ammonia was added dropwise to maintain pH=9.5 to promote the co-precipitation of hydroxides. After aging for 12 hours, the solid product was separated by centrifugation and calcined in a muffle furnace at 610℃ for 3 hours to convert the hydroxides into an oxide composite shell. The amount of coating solution added was controlled to form a 35 nm shell.

[0071] Bifunctional ligand synthesis: α-hydroxysuccinic acid and triethanolamine were added to a reaction vessel, heated to 120°C, and reacted for 4 hours under nitrogen protection. Then acrylamide was added, and the reaction was continued for 2 hours. The temperature was then lowered to 60°C to obtain an amber viscous liquid.

[0072] Nanoparticle surface modification: Core-shell structured particles were dispersed in deionized water, and bifunctional ligands were added, wherein the mass ratio of bifunctional ligands to core-shell structured particles was 0.65:1. The particles were ultrasonically treated at 600W and 40kHz for 30 min, and then stirred at 70℃ for 6 h to complete ligand anchoring. Free ligands were removed by dialysis, and the modified nanoparticles were obtained by spray drying.

[0073] Passivating agent compounding and molding: Modified nanoparticles and deionized water are mixed at a mass ratio of 25:75, 0.5wt% hydroxyethyl cellulose is added as a rheology modifier, and 1wt% butyl hydroxytoluene is added as an antioxidant. After high pressure homogenization, the passivating agent product is obtained.

[0074] Example 4

[0075] Synthesis of monodisperse barium titanate particles: Tetrabutyl titanate and barium hydroxide were dissolved in deionized water, with a molar ratio of tetrabutyl titanate to barium hydroxide of 1.10:1, to form a precursor solution. 0.05 mol / L citric acid was added as a complexing agent to prevent premature precipitation of titanium species. The solution was transferred to a high-pressure reactor and hydrothermally reacted at 200℃ for 12 hours. The white precipitate was collected by centrifugation, washed three times with ethanol, and dried under vacuum at 80℃. The resulting barium titanate nanoparticles were in a regular cubic phase with an average particle size of 60 nm.

[0076] Lanthanum oxide-magnesium oxide shell coating: Barium titanate particles were dispersed in an ethanol-water mixed solvent to prepare a coating solution containing lanthanum nitrate and magnesium nitrate. The coating solution was added dropwise to the barium titanate particle suspension under vigorous stirring at 800 rpm, while ammonia was added dropwise to maintain pH=9.5 to promote the co-precipitation of hydroxides. After aging for 12 hours, the solid product was separated by centrifugation and calcined in a muffle furnace at 590℃ for 3 hours to convert the hydroxides into an oxide composite shell. The amount of coating solution added was controlled to form a 25 nm shell.

[0077] Bifunctional ligand synthesis: α-hydroxysuccinic acid and triethanolamine were added to a reaction vessel, heated to 120°C, and reacted for 4 hours under nitrogen protection. Then acrylamide was added, and the reaction was continued for 2 hours. The temperature was then lowered to 60°C to obtain an amber viscous liquid.

[0078] Nanoparticle surface modification: Core-shell structured particles were dispersed in deionized water, and bifunctional ligands were added, wherein the mass ratio of bifunctional ligands to core-shell structured particles was 0.6:1. The particles were ultrasonically treated at 600W and 40kHz for 30 min, and then stirred at 70℃ for 6 h to complete ligand anchoring. Free ligands were removed by dialysis, and the modified nanoparticles were obtained by spray drying.

[0079] Passivating agent compounding and molding: Modified nanoparticles and deionized water are mixed at a mass ratio of 25:75, 0.5wt% hydroxyethyl cellulose is added as a rheology modifier, and 1wt% butyl hydroxytoluene is added as an antioxidant. After high pressure homogenization, the passivating agent product is obtained.

[0080] Example 5

[0081] Synthesis of monodisperse barium titanate particles: Tetrabutyl titanate and barium hydroxide were dissolved in deionized water, with a molar ratio of tetrabutyl titanate to barium hydroxide of 1.10:1, to form a precursor solution. 0.05 mol / L citric acid was added as a complexing agent to prevent premature precipitation of titanium species. The solution was transferred to a high-pressure reactor and hydrothermally reacted at 205 °C for 12 hours. The white precipitate was collected by centrifugation, washed three times with ethanol, and dried under vacuum at 80 °C. The resulting barium titanate nanoparticles were in a regular cubic phase with an average particle size of 65 nm.

[0082] Lanthanum oxide-magnesium oxide shell coating: Barium titanate particles were dispersed in an ethanol-water mixed solvent to prepare a coating solution containing lanthanum nitrate and magnesium nitrate. The coating solution was added dropwise to the barium titanate particle suspension under vigorous stirring at 800 rpm, while ammonia was added dropwise to maintain pH=9.5 to promote the co-precipitation of hydroxides. After aging for 12 hours, the solid product was separated by centrifugation and calcined in a muffle furnace at 605℃ for 3 hours to convert the hydroxides into an oxide composite shell. The amount of coating solution added was controlled to form a 30 nm shell.

[0083] Bifunctional ligand synthesis: α-hydroxysuccinic acid and triethanolamine were added to a reaction vessel, heated to 120°C, and reacted for 4 hours under nitrogen protection. Then acrylamide was added, and the reaction was continued for 2 hours. The temperature was then lowered to 60°C to obtain an amber viscous liquid.

[0084] Nanoparticle surface modification: Core-shell structured particles were dispersed in deionized water, and bifunctional ligands were added, wherein the mass ratio of bifunctional ligands to core-shell structured particles was 0.55:1. The particles were ultrasonically treated at 600W and 40kHz for 30 min, and then stirred at 70℃ for 6 h to complete ligand anchoring. Free ligands were removed by dialysis, and the modified nanoparticles were obtained by spray drying.

[0085] Passivating agent compounding and molding: Modified nanoparticles and deionized water are mixed at a mass ratio of 25:75, 0.5wt% hydroxyethyl cellulose is added as a rheology modifier, and 1wt% butyl hydroxytoluene is added as an antioxidant. After high pressure homogenization, the passivating agent product is obtained.

[0086] Comparative Example 1

[0087] Tetrabutyl titanate and barium hydroxide were dissolved in deionized water at a molar ratio of 1.10:1 to form a precursor solution. 0.05 mol / L citric acid was added as a complexing agent to prevent premature precipitation of titanium species. The solution was transferred to a high-pressure reactor and hydrothermally reacted at 200 °C for 12 hours. The white precipitate was collected by centrifugation, washed three times with ethanol, and dried under vacuum at 80 °C. The resulting barium titanate nanoparticles were in a regular cubic phase with an average particle size of 60 nm. Barium titanate was used only as a passivating agent.

[0088] Comparative Example 2

[0089] Synthesis of monodisperse barium titanate particles: Tetrabutyl titanate and barium hydroxide were dissolved in deionized water, with a molar ratio of tetrabutyl titanate to barium hydroxide of 1.10:1, to form a precursor solution. 0.05 mol / L citric acid was added as a complexing agent to prevent premature precipitation of titanium species. The solution was transferred to a high-pressure reactor and hydrothermally reacted at 180 °C for 12 hours. The white precipitate was collected by centrifugation, washed three times with ethanol, and dried under vacuum at 80 °C. The resulting barium titanate nanoparticles were in a regular cubic phase with an average particle size of 70 nm.

[0090] Lanthanum oxide-magnesium oxide shell coating: Barium titanate particles were dispersed in an ethanol-water mixed solvent to prepare a coating solution containing lanthanum nitrate and magnesium nitrate. The coating solution was added dropwise to the barium titanate particle suspension under vigorous stirring at 800 rpm, while ammonia was added dropwise to maintain pH=9.5 to promote the co-precipitation of hydroxides. After aging for 12 hours, the solid product was separated by centrifugation and calcined in a muffle furnace at 620℃ for 3 hours to convert the hydroxides into an oxide composite shell. The amount of coating solution added was controlled to form a 50 nm shell.

[0091] Bifunctional ligand synthesis: α-hydroxysuccinic acid and triethanolamine were added to a reaction vessel, heated to 120°C, and reacted for 4 hours under nitrogen protection. Then acrylamide was added, and the reaction was continued for 2 hours. The temperature was then lowered to 60°C to obtain an amber viscous liquid.

[0092] Nanoparticle surface modification: Core-shell structured particles were dispersed in deionized water, and bifunctional ligands were added, wherein the mass ratio of bifunctional ligands to core-shell structured particles was 0.55:1. The particles were ultrasonically treated at 600W and 40kHz for 30 min, and then stirred at 70℃ for 6 h to complete ligand anchoring. Free ligands were removed by dialysis, and the modified nanoparticles were obtained by spray drying.

[0093] Passivating agent compounding and molding: Modified nanoparticles and deionized water are mixed at a mass ratio of 25:75, 0.5wt% hydroxyethyl cellulose is added as a rheology modifier, and 1wt% butyl hydroxytoluene is added as an antioxidant. After high pressure homogenization, the passivating agent product is obtained.

[0094] Using a fixed fluidized bed device

[0095] Performance tests were conducted under conditions of 6000 ppm high vanadium pollution. The test indicators included: catalyst structural stability improvement rate, gasoline yield decline rate, micro-reaction activity loss rate, vanadium fixation efficiency, and hydrogen yield decline rate. The performance tests, such as the improvement rate, used a blank control without the addition of passivating agent. The results are shown in Table 1 below. The stability improvement rate was calculated based on the crystal retention rate.

[0096]

[0097] In summary, the core-shell composite passivator can achieve efficient vanadium suppression under high vanadium pollution conditions within the parameter range of 80-100nm particle size, 55-65nm core particle size, 15-35nm shell thickness, and 0.55-0.65:1 ligand ratio, providing reliable technical support for the processing of heavy feedstocks in catalytic cracking.

[0098] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A vanadium-inhibiting metal passivating agent for a catalytic cracking unit, characterized in that, Including core-shell structured particles and bifunctional organic ligands; The core-shell structured particles include a barium titanate core and a lanthanum oxide-magnesium oxide composite oxide shell, and the bifunctional organic ligand includes a strong coordinating group and a hydrophilic segment. The preparation of the vanadium-inhibiting metal passivating agent includes the following steps: Tetrabutyl titanate and barium hydroxide were dissolved in deionized water, and citric acid was added as a complexing agent to carry out a hydrothermal reaction. The precipitate was then collected by centrifugation, and the collected precipitate was washed and dried to obtain the barium titanate core. The barium titanate core was dispersed in an ethanol-water mixed solvent, and a coating solution containing lanthanum nitrate and magnesium nitrate was added dropwise while ammonia was added dropwise to maintain the pH value at 9.3-9.

7. After aging, the solid product was separated by centrifugation and then calcined to obtain core-shell structured particles. After reacting α-hydroxysuccinic acid with triethanolamine under nitrogen protection, acrylamide was added to continue the reaction to obtain a bifunctional ligand. Core-shell nanoparticles were dispersed in deionized water, a bifunctional ligand was added, and after ultrasonic treatment, the particles were stirred, dialyzed and spray-dried in sequence to obtain modified powder. The modified powder was mixed with deionized water, and a rheology modifier and an antioxidant were added. The mixture was then subjected to high-pressure homogenization to obtain a vanadium-inhibiting metal passivating agent.

2. The vanadium-inhibiting metal passivating agent for catalytic cracking units according to claim 1, characterized in that: The core-shell structure particles have a particle size of 80-100 nm, the barium titanate core has a particle size of 55-65 nm, and the lanthanum oxide-magnesium oxide composite oxide shell has a thickness of 15-35 nm. The molar ratio of lanthanum to magnesium in the lanthanum oxide-magnesium oxide composite oxide shell is 2:

3.

3. The vanadium-inhibiting metal passivating agent for catalytic cracking units according to claim 1, characterized in that: The strong coordinating group includes α-hydroxysuccinic acid, and the hydrophilic segment includes triethanolamine and acrylamide; The mass ratio of the bifunctional organic ligand to the core-shell structured particles is (0.55-0.65):

1.

4. The vanadium-inhibiting metal passivating agent for catalytic cracking units according to claim 1, characterized in that: The hydrothermal reaction is carried out at a temperature of 195-205℃ for 11-13 hours, and the molar ratio of titanium to barium in the tetrabutyl titanate and barium hydroxide is 1:(1.05-1.15).

5. The vanadium-inhibiting metal passivating agent for catalytic cracking units according to claim 1, characterized in that: In the ethanol-water mixed solvent, the volume ratio of ethanol to water is 3:1, and the calcination temperature of the centrifuged solid product after aging is 590-610℃, and the calcination time is 3h. The ultrasonic treatment has a power of 550-650W, a frequency of 38-42kHz, and a treatment time of 25-35min. During the addition of the coating liquid, the mixture is continuously stirred at a speed of not less than 800rpm.

6. The vanadium-inhibiting metal passivating agent for catalytic cracking units according to claim 1, characterized in that: α-Hydroxysuccinic acid and triethanolamine were reacted under nitrogen protection at 115-125℃ for 3.5-4.5 h, and then acrylamide was added and the reaction was continued at 115-125℃ for 1.5-2.5 h.

7. The vanadium-inhibiting metal passivating agent for catalytic cracking units according to claim 1, characterized in that: The ultrasonically treated stirring process is carried out under constant temperature stirring at 68-72℃ for 5.5-6.5 hours. The mass ratio of the modified powder to deionized water is (12-13):(37-38), and the pressure of the high-pressure homogenization treatment is 140-160 MPa.

8. The vanadium-inhibiting metal passivating agent for catalytic cracking units according to claim 1, characterized in that, The rheology modifier includes hydroxyethyl cellulose, and the amount of the rheology modifier added is 0.4-0.6 wt%. The antioxidant includes butylated hydroxytoluene, and the amount of the antioxidant added is 0.9-1.1 wt%.

9. The application of a vanadium-inhibiting metal passivating agent in a catalytic cracking unit, characterized in that, The application of the vanadium-inhibiting metal passivator according to any one of claims 1-8 in inhibiting vanadium contamination during catalytic cracking.

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