Anti-coking antimony trioxide production process

Abstract

The invention discloses an anti-coking antimony trioxide production process, and relates to the technical field of antimony trioxide production, and the anti-coking antimony trioxide production process comprises the following steps: uniformly mixing surface modified nano silicon dioxide, a rare earth oxide compound, a high-temperature lubricant and a metal catalyst according to a mass ratio of (50-60): (20-30): (15-20): (2-5) to prepare a composite auxiliary material; the refined metal antimony is placed in a generation furnace to be heated to 650-800 DEG C, and uniform antimony liquid is formed; under an inert atmosphere, adding a composite auxiliary material accounting for 0.01-0.05% of the mass of the antimony liquid into the antimony liquid, and uniformly stirring; the temperature is increased to 850-950 DEG C and kept, air is blown into the antimony liquid, and antimony trioxide steam is generated; and antimony trioxide steam is collected and condensed into antimony trioxide powder through a cooling system. By introducing the composite auxiliary material, the adhesion of the antimony liquid on the furnace wall is remarkably reduced, and coking is effectively prevented. The auxiliary material components have a synergistic effect, so that the problem of coking is solved from multiple dimensions.

Description

Technical Field

[0001] The present invention relates to the technical field of antimony trioxide production, and particularly to an antimony trioxide production process for preventing coking. Background Art

[0002] Antimony trioxide is an important chemical raw material, widely used in fields such as flame retardants and catalysts. Its main production method is the metal antimony fuming method, that is, by heating and melting refined metal antimony in a producer furnace, and blowing air at high temperature to oxidize and volatilize antimony into antimony trioxide vapor, and then cooling and collecting to obtain the product. In the traditional process, the temperature of the producer furnace is usually controlled at 650 - 850 °C to ensure the production of high-purity (≥99.9%) antimony trioxide. However, due to the high viscosity of the antimony liquid at high temperature and the uneven oxidation reaction, coking is likely to form on the furnace wall or in the pipeline, resulting in a decrease in production efficiency, an increase in equipment maintenance costs, and even affecting the product quality.

[0003] In the prior art, some processes alleviate the coking problem by adjusting the air blowing method or optimizing the furnace body structure, but the effect is limited, and often requires a large-scale transformation of the equipment, increasing the cost. Therefore, there is an urgent need for an efficient, low-cost and non-affecting product purity coking prevention process to improve the stability and economy of antimony trioxide production. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides an antimony trioxide production process for preventing coking, and the specific technical solution is as follows:

[0005] An antimony trioxide production process for preventing coking, comprising the following steps:

[0006] Step 1. Mix surface-modified nano-silica, rare earth oxide complex, high-temperature lubricant and metal catalyst evenly according to the mass ratio of (50 - 60):(20 - 30):(15 - 20):(2 - 5) to obtain a composite auxiliary material;

[0007] Step 2. Place refined metal antimony in a producer furnace and heat it to 650 °C - 800 °C to form a uniform antimony liquid;

[0008] Step 3. Under an inert atmosphere, add 0.01% - 0.05% of the composite auxiliary material by mass to the antimony liquid and stir evenly;

[0009] Step 4. Raise the temperature to 850 - 950 °C and maintain it, blow air into the antimony liquid to generate antimony trioxide vapor;

[0010] Step 5. Collect the antimony trioxide vapor and condense it into antimony trioxide powder through a cooling system.

[0011] Preferably:

[0012] The surface-modified nano-silica is obtained by compounding and modifying nano-silica with a silane coupling agent and hydroxylated polydimethylsiloxane;

[0013] The rare earth oxide complex is formed by compounding lanthanum oxide and cerium oxide;

[0014] The high-temperature lubricant is formed by compounding borate and phosphate;

[0015] The metal catalyst includes nano-molybdenum oxide.

[0016] Preferably:

[0017] The mass ratio of the silane coupling agent to hydroxylated polydimethylsiloxane is (1-3):1;

[0018] The mass ratio of lanthanum oxide to cerium oxide is 7:(3-4);

[0019] The mass ratio of borate to phosphate is (0.8-1.2):1.

[0020] Preferably, the borate is sodium borate and the phosphate is sodium tripolyphosphate.

[0021] Preferably, in step 1, the mixing method of the surface-modified nano-silica, rare earth oxide complex, high-temperature lubricant and metal catalyst is ball milling and mixing, and the milling time is 30-60 min.

[0022] Preferably, the way of blowing air in step 4 is pulsed air blowing, and the air blowing frequency is 40-60 times per minute.

[0023] Preferably, the preparation process of the surface-modified nano-silica includes the following steps:

[0024] Add nano-silica, silane coupling agent and hydroxylated polydimethylsiloxane into a stirrer, and stir and mix at 40-50 °C for 2-3 h;

[0025] Dry the mixture in an oven at 70-90 °C for 4-5 h to remove moisture and volatiles;

[0026] Use a grinder to grind the dried product into fine particles to obtain it.

[0027] Preferably, the preparation process of the rare earth oxide complex specifically includes the following steps:

[0028] Dissolve dioctyl phosphate in ethanol to make a modified solution with a concentration of 5%-10%;

[0029] Mix lanthanum oxide and cerium oxide evenly and add them into the modified solution, and perform ultrasonic dispersion treatment for 30-60 min;

[0030] Dry the dispersion in an oven at 60 - 80 °C for 6 - 8 h to remove ethanol;

[0031] Obtain the product by grinding the dried powder into fine particles.

[0032] Preferably, the preparation process of the high - temperature lubricant includes the following steps:

[0033] Dissolve polyethylene glycol in deionized water to make a PEG solution with a concentration of 10% - 20%;

[0034] Mix sodium borate and sodium tripolyphosphate evenly and slowly add them to the PEG solution, stirring continuously until homogeneous;

[0035] Obtain the product by drying the mixture into particles using a spray dryer.

[0036] Preferably, the metal catalyst is nanoscale molybdenum oxide surface - modified with a silane coupling agent, and its preparation process includes the following steps:

[0037] Add molybdenum oxide and silane coupling agent to isopropanol to make a suspension with a solid content of 10% - 20%;

[0038] Heat the suspension to 80 - 100 °C and reflux for 3 - 5 h;

[0039] Filter the suspension after the reaction and collect the solid;

[0040] Dry the solid in an oven at 60 - 80 °C for 4 - 8 h to remove isopropanol;

[0041] Obtain the product by grinding the dried powder into fine particles.

[0042] The anti - coking production process of antimony trioxide provided by the present invention has the following beneficial effects:

[0043] 1. By introducing composite auxiliary materials, the adhesion of antimony liquid on the furnace wall is significantly reduced, effectively preventing coking. The auxiliary material components act synergistically to solve the coking problem from multiple dimensions.

[0044] 2. The addition amount of the composite auxiliary material is only 0.01% - 0.05% of the mass of the antimony liquid, which has no significant impact on the purity of antimony trioxide, ensuring that the product meets high - quality requirements. The auxiliary material components are optimized in design, taking into account both high - efficiency anti - coking and low cost.

[0045] 3. The composite auxiliary material components have strong high - temperature stability, do not introduce harmful impurities, and the cooling and collection system efficiently recovers antimony trioxide powder, reducing material waste and environmental pollution. Detailed implementation mode

[0046] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be described in detail below. The description in this part is only exemplary and explanatory, and should not have any restrictive effect on the protection scope of the present invention.

[0047] An anti-coking production process of antimony trioxide includes the following steps:

[0048] Step 1. Mix surface-modified nano-silica, rare earth oxide complex, high-temperature lubricant and metal catalyst evenly according to the mass ratio of (50-60):(20-30):(15-20):(2-5) to obtain a composite auxiliary material.

[0049] Step 2. Place refined metallic antimony in a generator furnace and heat it to 650°C - 800°C to form a uniform antimony liquid.

[0050] Step 3. Under an inert atmosphere, add 0.01% - 0.05% of the composite auxiliary material based on the mass of the antimony liquid, and stir evenly.

[0051] Step 4. Raise the temperature to 850 - 950°C and maintain it, and blow air into the antimony liquid to generate antimony trioxide vapor.

[0052] Step 5. Collect the antimony trioxide vapor and condense it into antimony trioxide powder through a cooling system.

[0053] Among them, the purity of the antimony trioxide obtained from refined metallic antimony can reach more than 99.9%, and antimony trioxide with a purity of more than 99.8% can be used industrially. The addition amount of the composite auxiliary material in the antimony liquid is only 0.01% - 0.05%, so it will not have a great impact on the purity of the antimony trioxide finished product.

[0054] In the composite auxiliary materials: The modified nano-silica has a high specific surface area and excellent dispersibility, can be evenly distributed in the antimony liquid, reduce its surface tension and viscosity, and reduce the adhesion of the antimony liquid on the furnace wall. By reducing the viscosity of the antimony liquid and providing a lubricating layer, the deposition and solidification of the antimony liquid on the furnace wall are reduced, and the good compatibility of the modified layer with the antimony liquid can prevent agglomeration, ensure uniform dispersion, and reduce the coking tendency in local high-temperature areas; rare earth oxides have a unique electronic structure, can reduce the activation energy of the antimony oxidation reaction, promote the rapid reaction of antimony with oxygen to generate antimony trioxide vapor, and through catalytic action, reduce local overheating or uneven oxidation during the reaction process, prevent the decomposition or coking of the antimony liquid caused by high temperature, and can also inhibit side reactions caused by trace impurities that may exist in the antimony liquid, reducing the formation of coking precursor substances; the high-temperature lubricant can be partially melted at high temperature to form a smooth liquid or semi-solid coating, covering the furnace wall or the surface of the antimony liquid, and cooperating with the modified nano-silica to enhance the overall lubrication effect. The coating has chemical inertness, can prevent the antimony liquid or oxidation products from chemically bonding with the furnace wall, and the liquid characteristics of the lubricant promote the flow of the antimony liquid, reduce retention and local overheating, thereby preventing the antimony liquid from depositing and solidifying into coke on the furnace wall; the metal catalyst can further reduce the reaction temperature and energy barrier of antimony oxidation, improve the reaction efficiency, reduce the residence time of the antimony liquid in the high-temperature environment by accelerating the oxidation rate, reduce the coking risk caused by long-term high temperature, and can also promote the reaction uniformity, reduce local high-temperature areas, and avoid the formation of coke deposits.

[0055] Specifically, the modified nano-silica provides basic lubricity and viscosity adjustment, reducing the physical adhesion between the antimony liquid and the furnace wall; rare earth oxides and metal catalysts accelerate the oxidation reaction through catalytic action, shorten the high-temperature exposure time of the antimony liquid, and reduce the formation of coking precursors; the high-temperature lubricant forms a protective coating, further isolating the antimony liquid from the furnace wall and enhancing the anti-adhesion effect. The multi-component synergistic effect prevents coking.

[0056] The anti-coking antimony trioxide production process provided by this embodiment has the following beneficial effects:

[0057] 1. By introducing composite auxiliary materials, the adhesion of the antimony liquid on the furnace wall is significantly reduced, effectively preventing coking. The auxiliary material components act synergistically, thus solving the coking problem from multiple dimensions.

[0058] 2. The addition amount of the composite auxiliary materials is only 0.01% - 0.05% of the mass of the antimony liquid, which has no significant impact on the purity of antimony trioxide, ensuring that the product meets high-quality requirements. The auxiliary material components are optimized in design, taking into account both high-efficiency anti-coking and low cost.

[0059] 3. The composite auxiliary material components have strong high-temperature stability, do not introduce harmful impurities, and the cooling and collection system efficiently recovers the antimony trioxide powder, reducing material waste and environmental pollution.

[0060] Furthermore:

[0061] The surface-modified nano-silica is obtained by compounding and modifying nano-silica with a silane coupling agent and hydroxylated polydimethylsiloxane.

[0062] The rare earth oxide composite is formed by compounding lanthanum oxide and cerium oxide.

[0063] The high-temperature lubricant is formed by compounding borate and phosphate.

[0064] The metal catalyst includes nano-scale molybdenum oxide.

[0065] Furthermore:

[0066] The mass ratio of the silane coupling agent to hydroxylated polydimethylsiloxane is (1-3):1.

[0067] The mass ratio of lanthanum oxide to cerium oxide is 7:(3-4).

[0068] The mass ratio of borate to phosphate is (0.8-1.2):1.

[0069] Furthermore, the borate is sodium borate and the phosphate is sodium tripolyphosphate.

[0070] Furthermore, in step 1, the mixing method of the surface-modified nano-silica, rare earth oxide composite, high-temperature lubricant and metal catalyst is ball milling and mixing, and the milling time is 30-60 min.

[0071] Furthermore, the way of blowing air in step 4 is pulse air blowing, and the air blowing frequency is 40-60 times per minute.

[0072] Furthermore, the preparation process of the surface-modified nano-silica includes the following steps:

[0073] Add nano-silica, silane coupling agent and hydroxylated polydimethylsiloxane into a stirrer, and stir and mix at 40-50 °C for 2-3 h.

[0074] Dry the mixture in an oven at 70-90 °C for 4-5 h to remove moisture and volatiles.

[0075] Use a grinder to grind the dried product into fine particles to obtain it.

[0076] Furthermore, the preparation process of the rare earth oxide composite specifically includes the following steps:

[0077] Dissolve dioctyl phosphate in ethanol to make a modified solution with a concentration of 5%-10%.

[0078] Mix lanthanum oxide and cerium oxide evenly and add them into the modified solution, and perform ultrasonic dispersion treatment for 30-60 min.

[0079] Dry the dispersion in an oven at 60 - 80 °C for 6 - 8 h to remove ethanol.

[0080] It is obtained after grinding the dried powder into fine particles.

[0081] Furthermore, the preparation process of the high-temperature lubricant includes the following steps:

[0082] Dissolve polyethylene glycol in deionized water to make a PEG solution with a concentration of 10% - 20%.

[0083] Mix sodium borate and sodium tripolyphosphate evenly and slowly add them to the PEG solution, stirring continuously until homogeneous.

[0084] It is obtained after drying the mixture into particles using a spray dryer.

[0085] Furthermore, the metal catalyst is nanoscale molybdenum oxide modified by a silane coupling agent, and its preparation process includes the following steps:

[0086] Add molybdenum oxide and silane coupling agent to isopropanol to make a suspension with a solid content of 10% - 20%.

[0087] Heat the suspension to 80 - 100 °C and reflux for 3 - 5 h.

[0088] Filter the suspension after the reaction and collect the solid.

[0089] Dry the solid in an oven at 60 - 80 °C for 4 - 8 h to remove isopropanol.

[0090] It is obtained after grinding the dried powder into fine particles.

[0091] Specific examples are provided below. The provided examples can enable those skilled in the art to understand the present invention more comprehensively, but do not limit the present invention in any way.

[0092] Example 1

[0093] Weigh 200 g of nano-silica, 6 g of silane coupling agent (KH-550), and 3 g of hydroxylated polydimethylsiloxane (PDMS-OH), and place them in a stirrer. Set the stirrer temperature at 45 °C and the rotation speed at 500 rpm, and stir and mix for 2.5 h. Transfer the mixture to an oven, set the temperature at 80 °C, and dry for 4.5 h to remove moisture and volatiles. Grind the dried product using a planetary ball mill for 20 min at a rotation speed of 300 rpm to obtain approximately 205 g of surface-modified nano-silica for standby.

[0094] Put 55 g of surface-modified nano-silica, 25 g of rare-earth oxide composite (17.5 g of lanthanum oxide, 7.5 g of cerium oxide), 17 g of high-temperature lubricant (8.5 g of sodium borate, 8.5 g of sodium tripolyphosphate), and 3 g of molybdenum oxide into a planetary ball mill. Set the rotation speed at 400 rpm and grind for 45 min to ensure uniform mixing. Obtain 100 g of composite auxiliary material with uniform particle size for standby.

[0095] Load 50 kg of refined metallic antimony into a generator furnace. Introduce nitrogen (flow rate 2 L / min) as an inert atmosphere for protection. Heat to 750 °C (heating rate 10 °C / min) and hold for 30 min to form a uniform antimony liquid. The temperature of the antimony liquid is stable at 750 ± 5 °C with no obvious oxidation phenomenon.

[0096] Weigh 15 g of the composite auxiliary material. Disperse the auxiliary material in a 5 L nitrogen stream through an ultrasonic disperser and spray it into the antimony liquid. At the same time, use a mechanical stirrer (rotation speed 350 rpm) inside the generator furnace to stir for 10 min. The auxiliary material is evenly dispersed and there is no obvious agglomeration or precipitation in the antimony liquid.

[0097] Stop heating and heat up to 900 °C (heating rate 15 °C / min), and maintain the temperature at 900 ± 5 °C. Use a pulse gas flow controller to blow in air at a frequency of 50 times / min and a gas flow rate of 5 L / s. The reaction time is 2 h, and observe the generation of antimony trioxide vapor during this period. The generation of vapor is stable and there is no obvious coking on the furnace wall.

[0098] The antimony trioxide vapor passes through a multi-stage cooling system (500 °C → 200 °C → 50 °C, cooling time about 10 s). Use a cyclone separator and a bag filter to collect the antimony trioxide powder. The antimony trioxide powder is about 63.3 kg.

[0099] Take a sample of the antimony trioxide powder (5 g), press it into a tablet and conduct XRF analysis to determine the content of Sb2O3 and impurities. Take 0.5 g of the sample and disperse it in deionized water to measure the particle size distribution (D50). After the experiment, cool the generator furnace, check the furnace wall and the inner wall of the pipeline, and use a thermogravimetric analyzer to measure the mass of the residue (standard: the residue mass < 0.1 g is regarded as no obvious coking).

[0100] Example 2

[0101] Weigh 200 g of nano-silica, 6 g of silane coupling agent (KH-550), and 3 g of hydroxylated polydimethylsiloxane (PDMS-OH), and place them in a stirrer. Set the temperature of the stirrer at 45 °C and the rotation speed at 500 rpm, and stir and mix for 2.5 h. Transfer the mixture to an oven, set the temperature at 80 °C, and dry for 4.5 h to remove moisture and volatiles. Grind the dried material using a planetary ball mill for 20 min at a rotation speed of 300 rpm to obtain about 206 g of surface-modified nano-silica for standby.

[0102] Weigh 30 g of dioctyl phosphate and dissolve it in 600 mL of ethanol to prepare a modified solution. Weigh 17.5 g of lanthanum oxide and 7.5 g of cerium oxide, mix them evenly and add them to the modified solution. Use an ultrasonic disperser to treat for 45 min until evenly dispersed. Transfer the dispersion to an oven, set the temperature at 70 °C, and dry for 7 h to remove ethanol. Use a planetary ball mill to grind the dried powder for 15 min at a rotation speed of 300 rpm to obtain about 25 g of modified rare earth oxide composite for standby.

[0103] Place 55 g of surface-modified nano-silica, 25 g of modified rare earth oxide composite, 17 g of high-temperature lubricant (8.5 g of sodium borate and 8.5 g of sodium tripolyphosphate), and 3 g of molybdenum oxide in a planetary ball mill, set the rotation speed at 400 rpm, and grind for 45 min to ensure uniform mixing. Obtain 100 g of composite auxiliary material with uniform particle size for standby.

[0104] Load 50 kg of refined metallic antimony into a generator furnace. Introduce nitrogen (flow rate 2 L / min) as an inert atmosphere for protection. Heat to 750 °C (heating rate 10 °C / min) and maintain for 30 min to form a uniform antimony liquid. The temperature of the antimony liquid is stable at 750 ± 5 °C with no obvious oxidation phenomenon.

[0105] Weigh 15 g of the composite auxiliary material. Disperse the auxiliary material in a 5 L nitrogen stream through an ultrasonic disperser and spray it into the antimony liquid. At the same time, use a mechanical stirrer (rotation speed 350 rpm) inside the generator furnace to stir for 10 min. The auxiliary material is evenly dispersed and there is no obvious agglomeration or precipitation in the antimony liquid.

[0106] Stop heating, raise the temperature to 900 °C (heating rate 15 °C / min), and maintain the temperature at 900 ± 5 °C. Use a pulse gas flow controller to introduce air at a frequency of 50 times / min and a gas flow rate of 5 L / s. The reaction time is 2 h, and observe the generation of antimony trioxide vapor during this period. The generation of vapor is stable and there is no obvious coking on the furnace wall.

[0107] The antimony trioxide vapor passes through a multi-stage cooling system (500 °C → 200 °C → 50 °C, cooling time about 10 s). Use a cyclone separator and a bag filter to collect the antimony trioxide powder. The antimony trioxide powder is about 63.6 kg.

[0108] Take a sample (5 g) of the antimony trioxide powder, press it into a tablet and perform XRF analysis to determine the content of Sb2O3 and impurities. Take 0.5 g of the sample, disperse it in deionized water, and measure the particle size distribution (D50). After the experiment, cool the generator furnace, check the furnace wall and the inner wall of the pipeline, and use a thermogravimetric analyzer to measure the mass of the residue (standard: the residue mass < 0.1 g is regarded as no obvious coking).

[0109] Example 3

[0110] Weigh 200 g of nano-silica, 6 g of silane coupling agent (KH-550), and 3 g of hydroxylated polydimethylsiloxane (PDMS-OH), and place them in a stirrer. Set the temperature of the stirrer to 45 °C and the rotation speed to 500 rpm, and stir and mix for 2.5 h. Transfer the mixture to an oven, set the temperature to 80 °C, and dry for 4.5 h to remove moisture and volatiles. Grind the dried product using a planetary ball mill for 20 min at a rotation speed of 300 rpm to obtain approximately 205 g of surface-modified nano-silica for standby.

[0111] Weigh 17.5 g of lanthanum oxide and 7.5 g of cerium oxide, and mix them evenly. Obtain 25 g of rare earth oxide complex for standby.

[0112] Weigh 50 g of polyethylene glycol (PEG) and dissolve it in 400 mL of deionized water to prepare a PEG solution. Weigh 8.5 g of sodium borate and 8.5 g of sodium tripolyphosphate, mix them evenly, and slowly add them to the PEG solution while stirring with a stirrer for 30 min until homogeneous. Dry the mixture using a spray dryer, set the inlet air temperature to 200 °C and the spray pressure to 0.3 MPa, to obtain approximately 17 g of granular high-temperature lubricant for standby.

[0113] Place 55 g of surface-modified nano-silica, 25 g of rare earth oxide complex (17.5 g of lanthanum oxide, 7.5 g of cerium oxide), 17 g of high-temperature lubricant, and 3 g of molybdenum oxide in a planetary ball mill, set the rotation speed to 400 rpm, and grind for 45 min to ensure uniform mixing. Obtain 100 g of composite auxiliary material with uniform particle size for standby.

[0114] Load 50 kg of refined metallic antimony into a generating furnace. Pass nitrogen (flow rate 2 L / min) as an inert atmosphere for protection. Heat to 750 °C (heating rate 10 °C / min) and hold for 30 min to form a uniform antimony liquid. The temperature of the antimony liquid is stable at 750 ± 5 °C with no obvious oxidation phenomenon.

[0115] Weigh 15 g of the composite auxiliary material. Disperse the auxiliary material in a 5 L nitrogen stream using an ultrasonic disperser and spray it into the antimony liquid. At the same time, use a mechanical stirrer (rotation speed 350 rpm) inside the generating furnace to stir for 10 min. The auxiliary material is evenly dispersed and there is no obvious agglomeration or precipitation in the antimony liquid.

[0116] Stop heating, raise the temperature to 900 °C (heating rate 15 °C / min), and maintain the temperature at 900 ± 5 °C. Use a pulse gas flow controller to blow in air at a frequency of 50 times / min and a gas flow rate of 5 L / s. The reaction time is 2 h, and observe the generation of antimony trioxide vapor during this period. The vapor generation is stable and there is no obvious coking on the furnace wall.

[0117] Antimony trioxide vapor passes through a multi-stage cooling system (500°C → 200°C → 50°C, cooling time is about 10 s). A cyclone separator and a bag filter are used to collect antimony trioxide powder. The antimony trioxide powder is about 63.5 kg.

[0118] Take a sample of antimony trioxide powder (5 g), press it into tablets and conduct XRF analysis to determine the content of Sb2O3 and impurities. Take 0.5 g of the sample, disperse it in deionized water, and measure the particle size distribution (D50). After the experiment, cool the generator, check the inner walls of the furnace and the pipes, and use a thermogravimetric analyzer to measure the mass of the residue (standard: if the mass of the residue < 0.1 g, it is considered that there is no obvious coking).

[0119] Example 4

[0120] Weigh 200 g of nano-silica, 6 g of silane coupling agent (KH-550), and 3 g of hydroxylated polydimethylsiloxane (PDMS-OH), and place them in a stirrer. Set the temperature of the stirrer to 45°C and the rotation speed to 500 rpm, and stir and mix for 2.5 h. Transfer the mixture to an oven, set the temperature to 80°C, and dry for 4.5 h to remove moisture and volatiles. Use a planetary ball mill to grind the dried material for 20 min at a rotation speed of 300 rpm to obtain about 205 g of surface-modified nano-silica for standby.

[0121] Weigh 17.5 g of lanthanum oxide and 7.5 g of cerium oxide, mix them evenly to obtain 25 g of rare earth oxide complex for standby.

[0122] Weigh 8.5 g of sodium borate and 8.5 g of sodium tripolyphosphate, mix them evenly to obtain 17 g of high-temperature lubricant for standby.

[0123] Weigh 30 g of molybdenum oxide and 3 g of silane coupling agent (KH-550), add them to 270 mL of isopropanol to make a suspension with a solid content of about 10%. Transfer the suspension to a 500 mL three-necked flask, install a reflux condenser, heat to 90°C, and reflux for 4 h. After the reaction, filter the suspension using a vacuum filter to collect the solid. Transfer the solid to an oven, set the temperature to 70°C, and dry for 6 h to remove isopropanol. Use a planetary ball mill to grind the dried powder for 15 min at a rotation speed of 300 rpm to obtain about 30 g of modified molybdenum oxide for standby.

[0124] Place 55 g of surface-modified nano-silica, 25 g of rare earth oxide complex, 17 g of high-temperature lubricant, and 3 g of modified molybdenum oxide in a planetary ball mill, set the rotation speed to 400 rpm, and grind for 45 min to ensure uniform mixing. Obtain 100 g of composite auxiliary materials with uniform particle size for standby.

[0125] Load 50 kg of refined antimony metal into the generator. Introduce nitrogen gas (flow rate 2 L / min) as an inert atmosphere for protection. Heat to 750 °C (heating rate 10 °C / min), and maintain for 30 min to form a uniform antimony liquid. The temperature of the antimony liquid is stable at 750 ± 5 °C, with no obvious oxidation phenomenon.

[0126] Weigh 15 g of the composite auxiliary material. Disperse the auxiliary material in a 5 L nitrogen gas stream through an ultrasonic disperser and spray it into the antimony liquid. At the same time, use the built-in mechanical stirrer in the generator (rotation speed 350 rpm) to stir for 10 min. The auxiliary material is evenly dispersed, and there is no obvious agglomeration or precipitation in the antimony liquid.

[0127] Stop heating, heat up to 900 °C (heating rate 15 °C / min), and maintain the temperature at 900 ± 5 °C. Use a pulse gas flow controller to introduce air, with a frequency of 50 times / min and a gas flow rate of 5 L / s. The reaction time is 2 h, and during this period, observe the generation of antimony trioxide vapor. The generation of vapor is stable, and there is no obvious coking on the furnace wall.

[0128] The antimony trioxide vapor passes through a multi-stage cooling system (500 °C → 200 °C → 50 °C, cooling time about 10 s). Use a cyclone separator and a bag filter to collect the antimony trioxide powder. The antimony trioxide powder is about 64.0 kg.

[0129] Take a sample of the antimony trioxide powder (5 g), press it into a tablet and perform XRF analysis to determine the content of Sb2O3 and impurities. Take 0.5 g of the sample and disperse it in deionized water to measure the particle size distribution (D50). After the experiment, cool the generator, check the furnace wall and the inner wall of the pipeline, and use a thermogravimetric analyzer to measure the mass of the residue (standard: if the mass of the residue < 0.1 g, it is considered that there is no obvious coking).

[0130] Control experiment

[0131] Load 50 kg of refined antimony metal into the generator. Introduce nitrogen gas (flow rate 2 L / min) as an inert atmosphere for protection. Heat to 750 °C (heating rate 10 °C / min), and maintain for 30 min to form a uniform antimony liquid. The temperature of the antimony liquid is stable at 750 ± 5 °C, with no obvious oxidation phenomenon.

[0132] Stop heating, heat up to 900 °C (heating rate 15 °C / min), and maintain the temperature at 900 ± 5 °C. Use a pulse gas flow controller to introduce air, with a frequency of 50 times / min and a gas flow rate of 5 L / s. The reaction time is 2 h, and during this period, observe the generation of antimony trioxide vapor. The generation of vapor is stable, and there is no obvious coking on the furnace wall.

[0133] The antimony trioxide vapor passes through a multi-stage cooling system (500 °C → 200 °C → 50 °C, cooling time about 10 s). Use a cyclone separator and a bag filter to collect the antimony trioxide powder. The antimony trioxide powder is about 62.0 kg.

[0134] Take a sample of antimony trioxide powder (5 g), press it into tablets and perform XRF analysis to determine the content of Sb2O3 and impurities. Take 0.5 g of the sample, disperse it in deionized water, and measure the particle size distribution (D50). After the experiment, cool the generator, check the inner walls of the furnace and pipes, and use a thermogravimetric analyzer to measure the mass of the residue (standard: a residue mass < 0.1 g is considered to have no obvious coking).

[0135] The experimental data measured in Examples 1 to 4 and the comparative example are shown in the following table:

[0136] Experiment No. Purity of antimony trioxide (%) Powder particle size D50 (μm) Mass of coking residue (g) Yield (%) Example 1 99.89 2.3 0.05 95.5 Example 2 99.88 2.2 0.04 96.0 Example 3 99.87 2.4 0.03 95.8 Example 4 99.88 2.1 0.04 96.5 Comparative example 99.92 2.5 0.09 93.5

[0137] It can be seen that compared with the existing antimony trioxide production process (comparative example), Examples 1 to 4 significantly reduce the mass of coking residues. Among them, in Example 3, a high-temperature lubricant (containing polyethylene glycol) prepared by spray drying has uniform particles and excellent lubrication effect, and the anti-coking performance is the best.

[0138] The dioctyl phosphate-modified rare earth oxide and silane coupling agent-modified molybdenum oxide in Examples 2 and 4 improve the dispersibility of the auxiliary materials and the catalytic efficiency, and the anti-coking effect is better than that of Example 1.

[0139] Principle explanation:

[0140] The modified nano-silica has a high specific surface area and excellent dispersibility, can be evenly distributed in the antimony liquid, reduce its surface tension and viscosity, reduce the adhesion of the antimony liquid on the furnace wall, and reduce the deposition and solidification of the antimony liquid on the furnace wall by reducing the viscosity of the antimony liquid and providing a lubricating layer. Moreover, the good compatibility between the modified layer and the antimony liquid can prevent agglomeration, ensure uniform dispersion, and reduce the coking tendency in local high-temperature areas; rare earth oxides have a unique electronic structure, can reduce the activation energy of the antimony oxidation reaction, promote the rapid reaction of antimony with oxygen to generate antimony trioxide vapor, reduce local overheating or uneven oxidation during the reaction through catalytic action, prevent the decomposition or coking of the antimony liquid caused by high temperature, and can also inhibit side reactions caused by trace impurities that may exist in the antimony liquid, reducing the formation of coking precursor substances; the high-temperature lubricant can partially melt at high temperature to form a smooth liquid or semi-solid coating, covering the furnace wall or the surface of the antimony liquid, and cooperate with the modified nano-silica to enhance the overall lubrication effect. The coating has chemical inertness, can prevent the antimony liquid or oxidation products from bonding with the furnace wall chemically, and the liquid characteristics of the lubricant promote the flow of the antimony liquid, reduce retention and local overheating, thereby preventing the antimony liquid from depositing and solidifying into coke on the furnace wall; metal catalysts can further reduce the reaction temperature and energy barrier of antimony oxidation, improve the reaction efficiency, reduce the residence time of the antimony liquid in the high-temperature environment by accelerating the oxidation rate, reduce the coking risk caused by long-term high temperature, and can also promote the reaction uniformity, reduce local high-temperature areas, and avoid the generation of coking substances.

[0141] Specifically, the modified nano-silica provides basic lubricity and viscosity regulation, reducing the physical adhesion between the antimony liquid and the furnace wall; rare earth oxides and metal catalysts accelerate the oxidation reaction through catalysis, shortening the high-temperature exposure time of the antimony liquid and reducing the formation of coking precursors; the high-temperature lubricant forms a protective coating to further isolate the antimony liquid from the furnace wall and enhance the anti-adhesion effect. The multi-component synergistically prevents coking.

[0142] In this paper, specific examples are used to elaborate on the principle and implementation mode of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention. The above is only the preferred implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the technical field, within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be within the protection scope of the present invention.

Claims

1. A production process of antimony trioxide for preventing coking, characterized in that, It includes the following steps: S1. Mix surface-modified nano-silica, rare earth oxide complex, high-temperature lubricant, and metal catalyst evenly according to the mass ratio of (50 - 60):(20 - 30):(15 - 20):(2 - 5) to obtain a composite auxiliary material; S2. Place refined antimony metal in a generator furnace and heat it to 650°C - 800°C to form a uniform antimony liquid; S3. Under an inert atmosphere, add 0.01% - 0.05% of the composite auxiliary material based on the mass of the antimony liquid, and stir evenly; S4. Raise the temperature to 850 - 950°C and maintain it, and blow air into the antimony liquid to generate antimony trioxide vapor; S5. Collect the antimony trioxide vapor and condense it into antimony trioxide powder through a cooling system.

2. The production process of anti-coking antimony trioxide according to claim 1, wherein: The surface-modified nano-silica is obtained by compound modification of nano-silica with a silane coupling agent and hydroxylated polydimethylsiloxane; The rare earth oxide complex is formed by compounding lanthanum oxide and cerium oxide; The high-temperature lubricant is formed by compounding borate and phosphate; The metal catalyst includes nano-scale molybdenum oxide.

3. The production process of anti-coking antimony trioxide according to claim 2, wherein: The mass ratio of the silane coupling agent to hydroxylated polydimethylsiloxane is (1 - 3):1; The mass ratio of lanthanum oxide to cerium oxide is 7:(3 - 4); The mass ratio of borate to phosphate is (0.8 - 1.2):

1.

4. The anti-coking antimony trioxide production process according to claim 2, characterized in that, The borate is sodium borate, and the phosphate is sodium tripolyphosphate.

5. The anti-coking antimony trioxide production process according to claim 1, characterized in that, In step S1, the mixing method of the surface-modified nano-silica, rare earth oxide complex, high-temperature lubricant, and metal catalyst is ball milling, and the milling time is 30 - 60 min.

6. The anti-coking antimony trioxide production process according to claim 1, characterized in that, In step S4, the air-blowing method is pulsed air-blowing, and the air-blowing frequency is 40 - 60 times per minute.

7. The anti-coking antimony trioxide production process according to claim 3, characterized in that, The preparation process of the surface-modified nano-silica includes the following steps: Add nano-silica, silane coupling agent, and hydroxylated polydimethylsiloxane into a stirrer, and stir and mix at 40 - 50°C for 2 - 3 h; Dry the mixture in an oven at 70 - 90°C for 4 - 5 h to remove moisture and volatiles; Use a grinder to grind the dried product into fine particles to obtain it.

8. The anti-coking antimony trioxide production process according to claim 3, characterized in that, The preparation process of the rare earth oxide complex specifically includes the following steps: Dissolve dioctyl phosphate in ethanol to make a modified solution with a concentration of 5% - 10%; Mix lanthanum oxide and cerium oxide evenly and add them into the modified solution, and perform ultrasonic dispersion treatment for 30 - 60 min; Dry the dispersion liquid in an oven at 60 - 80°C for 6 - 8 h to remove ethanol; Grind the dried powder into fine particles to obtain it.

9. The anti-coking antimony trioxide production process according to claim 4, characterized in that, The preparation process of the high-temperature lubricant includes the following steps: Dissolve polyethylene glycol in deionized water to make a PEG solution with a concentration of 10% - 20%; Mix sodium borate and sodium tripolyphosphate evenly and slowly add them into the PEG solution, stirring while adding until it is uniform; Use a spray dryer to dry the mixed liquid into particles to obtain it.

10. The anti-coking antimony trioxide production process according to claim 2, characterized in that, The metal catalyst is nano-scale molybdenum oxide surface-modified by a silane coupling agent, and its preparation process includes the following steps: Molybdenum oxide and a silane coupling agent are added to isopropanol to prepare a suspension with a solid content of 10% - 20%; The suspension is heated to 80 - 100 °C and refluxed for 3 - 5 h; After the reaction, the suspension is filtered to collect the solid; The solid is dried in an oven at 60 - 80 °C for 4 - 8 h to remove isopropanol; It is obtained after grinding the dried powder into fine particles.