Composite silicon dioxide carrier with high specific surface area and preparation method thereof

Abstract

The preparation method comprises the following steps: S1, taking a water glass solution and a sulfuric acid solution as raw materials, S2, crushing silica gel, transferring the crushed silica gel into a reaction kettle A, heating the crushed silica gel, carrying out an aging reaction, S3, stopping heat preservation after aging, adjusting the pH value to 6.0-6.5, continuing stirring and aging, and carrying out filtration, washing and drying to obtain the composite silica carrier with the high specific surface area. S5, a mixture obtained after dispersion and pore filling is subjected to flash evaporation drying to obtain powder, silica sol with the specific particle size is added to fully permeate into inner pores of gel method silica, silica particles of the silica sol can be randomly reserved in the inner pores in the spray drying process, and the silica particles of the silica sol can be fully dispersed into the inner pores of the gel method silica; on one hand, the specific surface area of the product is increased, and the adsorption capacity of the product is improved; on the other hand, silica sol-silica particles in the inner holes form a supporting structure, the space structure of the carrier is further strengthened in the roasting process, and the mechanical strength and wear resistance are greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of chemical preparation technology, specifically relating to a high specific surface area composite silica carrier and its preparation method. Background Technology

[0002] As is well known, silica is often used as a catalyst support in the petrochemical, petroleum refining, and industrial catalysis fields. In addition to having a suitable pore structure and specific surface area, the catalyst support also needs to have high mechanical strength and wear resistance. Especially in most industrial processes, such as fluidized beds and fixed beds, frequent friction and collisions occur between catalyst particles, between catalyst particles and the reactor wall, and between catalyst particles and reactants or products. If the support is fragile or easily pulverized, the resulting powder particles will cause the fluidized bed or fixed bed to collapse. When the content of fine powder increases to a certain level, it will block the pore structure, further causing problems such as increased pressure drop and flow deviation in the bed reaction, ultimately leading to catalyst poisoning and shortening the catalyst's service life.

[0003] To improve catalyst performance, the industry has made many improvements to silica supports, among which improving mechanical strength and wear resistance is particularly crucial. However, preparing microspherical silica supports with suitable pore structure, high mechanical strength and excellent wear resistance remains a technical challenge in this field. This is because silica raw materials (such as precipitated silica and fumed silica) usually have poor sintering performance, and even after recrystallization treatment (such as hydrothermal treatment), the wear resistance of the support is still difficult to improve significantly. If alumina, calcium oxide, kaolin and other binders are used, although mechanical strength and wear resistance can be improved to a certain extent, the acid-sensitive components in the binder will be corroded under acidic conditions, resulting in a gradual decrease in the mechanical strength and wear resistance of the support.

[0004] Existing methods for pore expansion typically involve drying silica sol obtained from sodium silicate at a relatively low temperature (approximately 100°C) to obtain large-particle silica with a pore size of 12 nm. This is followed by pore expansion treatment in an autoclave using an ammonia solution, ultimately yielding a macroporous silica carrier with a particle size of 100–200 μm, a pore size of 42–200 nm, and a pore volume of 1.05 ml / g. The drawbacks of this method are that the high-temperature and high-pressure conditions are unsuitable for industrial production, resulting in low operational efficiency and a complex process. Furthermore, the use of ammonia solution as a pore-expanding agent causes significant environmental pollution and is difficult to implement. Large-scale industrial production is problematic because the working environment is filled with the smell of ammonia, which is detrimental to worker health. Another method involves preparing porous microspheres with an average particle size of 0.5–20 μm from inorganic colloidal particles of 0.005–1.0 μm. The core of this method is to first encapsulate small inorganic colloidal particles in an organic polymer, and then remove the organic polymer by calcination to form porous microspheres. The advantage of this method is that the pore size of the porous microspheres can be controlled by the size of the selected colloidal particles. However, the disadvantage is that the produced macroporous carrier has poor mechanical strength and is fragile. Furthermore, it is difficult to accurately control the specific surface area and average pore size during the sintering process. Summary of the Invention

[0005] The purpose of this invention is to provide a high specific surface area composite silica carrier and its preparation method, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a high specific surface area composite silica carrier, comprising the following steps:

[0007] S1. Silica gel was prepared by reacting water glass solution and sulfuric acid solution in a co-current mixing process.

[0008] S2. After crushing the silica gel, transfer it to reactor A, add water as a solvent, and add saturated sodium bicarbonate solution to reactor A to adjust the pH of the solution to 9.0±0.2. Then heat and age the solution.

[0009] S3. After aging is complete, stop the heat preservation and adjust the pH to 6.0-6.5. Then continue stirring and aging. Then, filter the stirred and aged material using an 800-mesh filter cloth and wash the material with pure water until it is neutral.

[0010] S4. Transfer the filter cake from the pressure filter to reactor B, and then add high-purity water and silica sol solution to reactor B for dispersion and pore filling.

[0011] S5. The mixture obtained after dispersion and pore filling is flash-dried to obtain powder, and the powder is then calcined to obtain composite silica carrier product.

[0012] Preferably, in step 1, the SiO2 concentration in the water glass solution is 25wt%, and the concentration of the dilute sulfuric acid solution is 45wt%. By limiting the raw material concentration parameters, the gelation reaction is ensured to proceed stably, thus guaranteeing the basic properties of the silica gel.

[0013] Preferably, in step 1, the flow rate of the water glass solution in the co-current mixing reaction is 1-3.0 m³ / h, the flow rate of the dilute sulfuric acid solution is 0.5-1.5 m³ / h, and the mixing ratio is 2:1 (V:V). By controlling the mixing flow rate and ratio of the raw materials, the uniform reaction of the two raw materials is ensured, and local reaction imbalance is avoided from affecting the gel quality.

[0014] Preferably, in step 2, the silicone gel is pulverized using a stainless steel multi-functional pulverizer with a 4mm stainless steel mesh screen. The particle size distribution of the pulverized powder is 20-200μm. The aging reaction temperature is ≥95℃, the reaction time is 8-16 hours, and the mass ratio of water to silicone gel powder is 1:1. By limiting the pulverization parameters, the gel particle size is made uniform. High-temperature aging and a reasonable liquid-solid ratio are used to construct a high-strength spatial structure and improve the mechanical properties of the carrier.

[0015] Preferably, in step 3, dilute sulfuric acid is used to adjust the pH to 6.0-6.5, and the stirring rate is maintained at 30-50 r / min during the adjustment process. The aging process is continuous stirring aging, the aging temperature is room temperature, and the aging time is 24-48 hours. The neutrality judgment standard is the pH of the washing effluent to 6.5-7.0. By adjusting the pH and stirring aging to optimize the gel structure, and combining it with precise washing standards to remove impurities, the subsequent processes can be carried out smoothly.

[0016] Preferably, in step 4, the silica sol is an alkaline silica sol with a particle size of 10nm to 15nm, a silica sol concentration of 20wt%, and an addition amount of 5% to 20% of the filter cake mass. The filter cake is the wet filter cake that has not been dried after washing in step 3. By limiting the type, particle size, concentration, and addition amount of silica sol, it is ensured that the silica sol can fully penetrate into the gel pores, preparing for increasing the specific surface area and strengthening the structure.

[0017] Preferably, in step 4, the amount of high-purity water added is 1 times the mass of the filter cake. The dispersion and filling of the pores is carried out by mechanical stirring. The stirrer is an anchor stirrer with a stirring linear speed of ≥60 m / min and a stirring time of ≥8 h. During the stirring process, the system temperature is maintained at 25-35℃. By optimizing the liquid-solid ratio, stirring parameters and temperature of the dispersion and filling of the pores, it is ensured that the silica sol fills the inner pores uniformly and avoids local accumulation that affects the uniformity of the carrier structure.

[0018] Preferably, in step 5, the flash drying is carried out using centrifugal spray drying, with an inlet air temperature of 200-250°C and an outlet air temperature of 80-100°C; the calcination is carried out in an air atmosphere, with a calcination temperature of 600-1000°C, a calcination time of 2-4 hours, and a calcination heating rate of 5-10°C / min. After calcination, the substrate is naturally cooled to room temperature to obtain a composite silica carrier. By limiting the drying and calcination parameters, moisture and impurities are removed, the spatial structure of the carrier is strengthened, and a composite silica carrier with stable performance is finally obtained.

[0019] A composite silica carrier with high specific surface area prepared by the above method is a porous network structure containing a supporting framework formed by silica sol filling. The average pore size of the carrier is 20-23 nm, and the specific surface area is not less than 260 m² / g.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] (1) The present invention uses water glass and dilute sulfuric acid to prepare silica gel by co-current mixing reaction. The source is gel silica, which has better structural stability than precipitated silica or gas phase silica, laying the foundation for the subsequent preparation of high mechanical strength carrier.

[0022] (2) A high-temperature aging process of ≥95℃ is used in the aging step of the hole expansion process. The high-temperature environment is conducive to building a high-strength spatial structure, which significantly enhances the mechanical strength of the carrier and improves its impact resistance.

[0023] (3) By adding silica sol with a specific particle size (10nm~15nm) to fully penetrate into the inner pores of gel-processed silica, the silica particles of silica sol will be randomly retained in the inner pores during the spray drying process. On the one hand, this increases the specific surface area of ​​the product and improves the adsorption capacity of the product, which is beneficial for the subsequent adsorption of active components such as metal ions or small organic molecules to prepare catalysts. On the other hand, the silica particles of silica sol in the inner pores form a supporting structure, which further strengthens the spatial structure of the carrier during the calcination process and greatly improves the mechanical strength and wear resistance.

[0024] (4) The high-temperature calcination process can not only burn off the moisture and impurities remaining in the inner pores and increase the pore volume, but also strengthen the spatial structure of the carrier and further enhance its mechanical strength, ensuring that the carrier has excellent stability in complex industrial environments. Attached Figure Description

[0025] Figure 1 This is a flowchart of the preparation method of the present invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "sleeved with," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0028] The following combination Figure 1 The present invention will be further described as follows:

[0029] The following methods and standards were used to test the physicochemical properties of the finished products in all embodiments and comparative examples. All test samples underwent pretreatment by vacuum drying at 500°C for 2 hours to remove adsorbed moisture and ensure the accuracy of the test data.

[0030] 1. Specific surface area and pore structure testing: A fully automated specific surface area and porosity analyzer (model: Microt TriStar II plus 3.03) was used. Before testing, the samples were degassed at 500℃ for 3 hours with a degassed vacuum degree ≤10Pa. The specific surface area was calculated using the BET method, and the pore volume and pore size distribution of the mesoporous region (2-50nm) were analyzed using the BJH method. The pore size was expressed as the most probable pore size calculated by the BJH desorption branch. The particle size was measured using a laser particle size analyzer (model: Malvern 3000). Deionized water was used as the dispersion medium, and 0.05wt% sodium hexametaphosphate was added as a dispersant. The samples were ultrasonically dispersed for 10 minutes before testing. The particle size distribution was characterized by D10, D50, and D100.

[0031] 2. Average particle size test: A laser particle size analyzer (model: Malvern 3000) was used.

[0032] 3. Bulk density test: Referring to GB / T 16913.3-1997 standard, a 100mL standard volumetric cylinder is used. The sample is slowly poured into the cylinder through a funnel, avoiding vibration. After filling to the mark, the excess sample is scraped off and the sample mass is weighed. Bulk density = powder mass / volume V of the container occupied by the powder. The test is performed in parallel for 3 times and the average value is taken. The test accuracy is 0.0001g / cm³.

[0033] 4. Strength and Abrasion Resistance Test: According to NB / SH / T 0964-2017 "Determination of Wear Index of Catalytic Cracking Catalyst - Straight Tube Method", an XCM-1 straight tube wear index tester was used for evaluation. Specific test conditions were: a loading amount of 30.00±0.01g (baked at 500℃ for 1h, cooled to room temperature in a desiccator, and then weighed), using humidified air as the gas source (relative humidity 60±5%), and an air flow rate of 100±5mL / min. The wear rate and breakage rate were measured sequentially at 10h, 50h, and 250h. During the test, the fluidization height was controlled to approximately 5 times the static height (achieved by adjusting the airflow speed). Ensure consistent fluidization state of all carriers; Wear rate = mass of collected dust (particle diameter less than 15μm) / loading amount 30g. Before weighing, place the collected dust and filter paper in a crucible and bake at 500℃ for 1h to burn off the filter paper and moisture. After cooling, weigh using an electronic analytical balance (accuracy 0.1mg); Fragmentation rate is calculated by examining the number of fragments in 1000 randomly selected microspheres after wear using an optical microscope (magnification 100x). The criterion for fragmentation is the appearance of obvious cracks or breakage into two or more independent particles in the microspheres; The test methods for wear rate and fragmentation rate of the catalyst are similar to those for the carrier.

[0034] Comparative Example 1

[0035] At room temperature, the water glass pump flow rate was adjusted to 1.0 m³ / h, and the sulfuric acid pump flow rate was adjusted to 0.5 m³ / h. 0.5 m³ of 25 wt% water glass and 0.25 m³ of 45 wt% sulfuric acid solution were simultaneously added to a 1000 L tank over a period of 30 minutes, forming a silica gel liquid. After standing for 36 hours, the silica gel liquid gelled, forming a silica gel and producing acidic water. After draining the acidic water, the silica gel was manually scraped and broken into 15 mm pieces using a shovel. These 15 mm pieces were then further pulverized using a stainless steel multi-functional pulverizer with a 4 mm stainless steel mesh sieve to obtain silica gel powder of 20–200 μm. The silica gel powder was then set aside for use.

[0036] Weigh 80 kg of silica gel powder into a 200 L enamel-lined reactor A, add 80 kg of tap water, and adjust the pH of the system to 9.0 ± 0.2 using saturated sodium bicarbonate. Turn on the cooling reflux device and begin heating the reactor to 95 °C for aging. Stop heating after 8 hours. Add dilute sulfuric acid to the reactor to adjust the pH to 6.0–6.5, and continue aging for 24 hours. Open the bottom valve and transfer the aged liquid to a plate and frame filter press with an 800-mesh filter cloth for filtration. Wash with high-purity water until the pH of the discharged water is measured to be 6.5–7.0. Washing is now complete. Transfer the filter cake to reactor B and add 80 kg of high-purity water. Start the agitator and adjust the linear speed to 60 m / min, stirring for 8 hours. After stirring, spray dry the resulting slurry, then calcine it in a 600 °C furnace for 2 hours to obtain the silica carrier product.

[0037] The following are the test results of the physicochemical properties of samples taken from three different locations of the finished product in Comparative Example 1, as shown in Table 1:

[0038] Table 1

[0039]

[0040] Comparative Example 2

[0041] At room temperature, the water glass pump flow rate was adjusted to 1.4 m³ / h, and the sulfuric acid pump flow rate was adjusted to 0.7 m³ / h. 0.7 m³ of 25 wt% water glass and 0.35 m³ of 45 wt% sulfuric acid solution were simultaneously injected into a 1000 L tank over a period of 30 minutes, forming a silica gel liquid. After standing for 48 hours, the silica gel liquid gelled, forming a silica gel and acidic water. After draining the acidic water, the silica gel was manually scraped and broken into 15 mm pieces using a shovel. These 15 mm pieces were then further pulverized using a stainless steel multi-functional pulverizer with a 4 mm stainless steel mesh sieve to obtain silica gel powder of 20–200 μm. The silica gel powder was set aside for later use.

[0042] Weigh 80 kg of silica gel powder into a 200 L enamel-lined reactor A, add 80 kg of tap water, and adjust the pH of the system to 9.0 ± 0.2 using saturated sodium bicarbonate. Turn on the cooling reflux device and begin heating the reactor to 100 °C for aging. Stop heating after 8 hours. Add dilute sulfuric acid to the reactor to adjust the pH to 6.0–6.5, and continue aging for 24 hours. Open the bottom valve and transfer the aged liquid to a plate and frame filter press with an 800-mesh filter cloth for filtration. Wash with high-purity water until the pH of the discharged water is measured to be 6.5–7.0, indicating washing is complete. Transfer the filter cake to reactor B and add 80 kg of high-purity water. Start stirring and adjust the linear speed to 60 m / min. Stir for 12 hours. After stirring, spray dry the resulting slurry and then calcine it in a 1000 °C furnace for 4 hours to obtain the silica carrier product.

[0043] The following are the test results of the physicochemical properties of samples taken from three different locations of the finished product in Comparative Example 2, as shown in Table 2:

[0044] Table 2

[0045]

[0046] Example 1

[0047] Under room temperature (25±2℃) conditions, industrial-grade water glass (SiO2 content 25wt%, Na2O content 7.5wt%, impurity content ≤0.1wt%) with a modulus of 3.2 and industrial-grade dilute sulfuric acid (concentration 45wt%, Fe content ≤0.005wt%) were selected as raw materials. The flow rate of the water glass pump (model: G-type screw pump, flow accuracy ±0.01m³ / h) was adjusted to 1.0m³ / h, and the flow rate of the sulfuric acid pump (model: corrosion-resistant diaphragm pump, flow accuracy ±0.01m³ / h) was adjusted to 0.5m³ / h. 0.5m³ of water glass and 0.25m³ of sulfuric acid solution were simultaneously injected into a 1000L stainless steel reaction tank through dual feed pipes. During the feeding process, the anchor-type agitator (model: JBJ-1000, agitator diameter 800mm) at the bottom of the reaction tank was turned on, maintaining a stirring rate of 80r / min. Ensure the two raw materials are mixed evenly, with the addition time strictly controlled at 30 minutes to form a uniform silica gel liquid. Turn off the stirring and allow the silica gel liquid to stand at room temperature for 36 hours to allow it to fully gel. After gelation, a silica gel and acidic water (supernatant) will be formed. Slowly drain the acidic water (pH≈2.0) through the drain valve at the bottom of the reaction tank, avoiding disturbance to the silica gel layer during the draining process. After draining the acidic water, manually scrape the silica gel with a stainless steel spatula to break it into pieces of about 15mm. Then, use a stainless steel multi-functional pulverizer (model: WF-400, speed 3000r / min) with a 4mm stainless steel mesh screen to further pulverize it. After pulverization, sieve it through a vibrating screen (model: ZS-515) to remove excessively large particles, obtaining silica gel powder with a particle size distribution of 20-200μm. Place the powder in a desiccator for later use to prevent moisture absorption.

[0048] 80.0 kg of the above-mentioned silica gel powder was weighed using an electronic platform scale (100 kg capacity, 0.1 kg accuracy) and slowly added to a 200 L enamel-lined reactor A (model: FCH-200, with jacketed heating and cooling reflux device, anchor-type stirrer); then 80.0 kg of tap water (conductivity ≤50 μS / cm) was added, and stirring was started and the stirring speed was adjusted to 50 r / min to uniformly disperse the powder in the water; saturated sodium bicarbonate solution (concentration ≥99.5%, analytical grade) was slowly added dropwise using a pipette. During the dropwise addition, a pH meter (model: PHS-3C, accuracy ±0.01) was used to monitor the pH value of the system in real time, and the pH was adjusted to 9.0±0.2. After the dropwise addition was completed, stirring was continued for 10 minutes to ensure that the pH was uniform and stable. The jacket heating device was turned on, and heat transfer oil was used for heating. The heating rate was set to 2℃ / min. After heating to 95℃, the cooling reflux device was turned on (condensate temperature ≤10℃) to keep the temperature inside the reactor stable at 95±1℃. The aging reaction was carried out for 8 hours. During the aging process, a record was taken every 1 hour. The temperature and pH were adjusted to ensure stable reaction conditions. After aging, the heating device was turned off, and the mixture was allowed to cool naturally to below 60°C. Dilute sulfuric acid (45wt%) was then slowly added dropwise to the reactor through a constant-pressure dropping funnel to adjust the pH to 6.0–6.5. During the addition, the stirring rate was maintained at 30 r / min. After the addition was completed, stirring and aging continued for 24 hours, with the aging temperature controlled at room temperature (25±2°C). After aging, the bottom valve of the reactor was opened, and the aging liquid was piped to a plate and frame filter press with 800-mesh filter cloth. (Model: XMYZ-80 / 1000-UB, pressure 0.6MPa) is used for pressure filtration. During the filtration process, the pressure is kept stable. After the filtrate no longer flows out significantly, the feed valve is closed and the washing water valve is opened. High-purity water (conductivity ≤10μS / cm) is used for washing. During the washing process, the pH value of the washing discharge water is sampled and tested every 30 minutes until the pH value of the discharge water is 6.5~7.0. Then, the washing is stopped, the washing water valve is closed, and pressure filtration continues for 30 minutes to remove free water from the filter cake and complete the washing process.

[0049] The filter cake (approximately 60 wt% moisture content) after pressure filtration was transferred to a 200L enamel-lined reactor B (model: FCH-200, equipped with a variable frequency stirrer) using a stainless steel shovel. 80.0 kg of high-purity water and 4.0 kg of alkaline silica sol (particle size 10 nm–15 nm, concentration 20 wt%, pH 9.0–10.0, analytical grade) were added. The variable frequency stirrer was turned on, and the stirring linear speed was adjusted to 60 m / min (corresponding to a stirring rate of 120 r / min). The stirring time was 8 hours, maintaining the system temperature at 25–30℃ during stirring. The slurry state was observed every 2 hours to ensure no sediment accumulation. After stirring, the resulting slurry was pumped through a screw pump (model: G3). 0-1) The powder is fed into a centrifugal spray dryer (model: LPG-5, inlet air temperature 220℃, outlet air temperature 90℃, atomizer speed 20000r / min) for flash drying. After drying, a white powder (moisture content ≤5wt%) is obtained. The dried powder is then placed in an alumina crucible and placed in a box-type resistance furnace (model: SX2-12-10, temperature control accuracy ±5℃). The powder is calcined in an air atmosphere with a heating rate of 5℃ / min. After heating to 600℃, the powder is calcined at a constant temperature for 2 hours. After calcination, the heating device is turned off, and the powder is allowed to cool naturally to room temperature (25±2℃) to obtain a composite silica carrier product. The product is then sealed and stored in a desiccator to prevent moisture absorption.

[0050] The finished product of Example 1 was sampled using the quartering method. Five sampling points were selected at different locations (top, middle, bottom, left, and right) of the product pile, with 10g sample taken from each sampling point. After mixing, the samples were divided into three parallel groups (5g each) for physicochemical property testing. The testing process strictly followed the above testing method. The results are shown in Table 3.

[0051] Table 3

[0052]

[0053] Example 2

[0054] At room temperature (25±2℃), water glass (modulus 3.2, SiO2 content 25wt%) and dilute sulfuric acid (concentration 45wt%) of the same specifications as in Example 1 were selected as raw materials. The flow rate of the water glass pump was adjusted to 1.0 m³ / h and the flow rate of the sulfuric acid pump was adjusted to 0.5 m³ / h. 0.5 m³ of water glass and 0.25 m³ of sulfuric acid solution were simultaneously injected into a 1000L stainless steel reaction tank through a double feed pipe. During the feeding process, the stirring rate was maintained at 80 r / min and the mixture was added at a uniform rate within 30 min to form a uniform silica gel liquid. The stirring was turned off and the mixture was allowed to stand at room temperature for 48 hours to allow the silica gel liquid to fully gel. After the upper layer of acid water was drained, the silica gel was manually broken into 15 mm blocks and then crushed and sieved using a stainless steel multi-functional pulverizer (model: WF-400) with a 4 mm stainless steel mesh screen to obtain 20-200 μm silica gel powder, which was then stored in a dryer for later use.

[0055] Weigh 80.0 kg of the above silica gel powder into a 200L enamel-lined reactor A, add 80.0 kg of tap water, and start stirring (50 r / min) to disperse the powder evenly; add saturated sodium bicarbonate solution dropwise to adjust the pH to 9.0±0.2, and stir for 10 min to stabilize the pH; turn on the jacket heating at a heating rate of 2℃ / min, and heat to 100℃, then turn on the cooling reflux device to maintain the temperature at 100±1℃, and age for 12 hours, monitoring the temperature and pH every 1 hour during the aging process; after aging, cool down to below 60℃, add dilute sulfuric acid dropwise to adjust the pH to 6.0~6.5, maintain the stirring rate at 30 r / min, and age at room temperature for 24 hours; filter the aged liquid through an 800-mesh filter cloth plate and frame filter press, wash with high-purity water until the pH of the effluent is 6.5~7.0, and filter for 30 min to remove free water.

[0056] The filter cake was transferred to a 200L enamel-lined reactor B, and 80.0 kg of high-purity water and 4.0 kg of alkaline silica sol (particle size 10nm~15nm, concentration 20wt%) were added. The variable frequency stirring was turned on, and the linear speed was adjusted to 70 m / min (corresponding to a stirring rate of 140 r / min). The mixture was stirred at room temperature (25±2℃) for 10 hours. After stirring, the slurry was dried by a centrifugal spray dryer (inlet air 230℃, outlet air 95℃, atomizer speed 22000 r / min) to obtain a white powder with a water content ≤5wt%. The powder was placed in a box-type resistance furnace and heated to 800℃ at 5℃ / min in an air atmosphere. It was calcined at a constant temperature for 2 hours, and then naturally cooled to room temperature before being sealed and stored to obtain the composite silica carrier product.

[0057] In Example 2, three parallel samples were selected using the same sampling method as in Example 1 for physicochemical property testing. The testing conditions were the same as in Example 1, and the results are shown in Table 4.

[0058] Table 4

[0059]

[0060] Example 3

[0061] Under room temperature (25±2℃) conditions, water glass (modulus 3.2, SiO2 content 25wt%) and dilute sulfuric acid (concentration 45wt%) of the same specifications as in Example 2 were selected as raw materials. The water glass pump flow rate was adjusted to 1.4 m³ / h, and the sulfuric acid pump flow rate was adjusted to 0.7 m³ / h. 0.7 m³ of water glass with a silica concentration of 25wt% and 0.35 m³ of sulfuric acid solution with a concentration of 45wt% were simultaneously injected into a 1000L stainless steel reaction tank over a period of 30 minutes, forming a silica liquid. After standing for 48 hours, the silica liquid gelled, forming a silica gel and acidic water. After the acidic water was discharged, the silica gel was manually scraped and broken into 15mm pieces using a shovel. The 15mm pieces were then further pulverized using a stainless steel multi-functional pulverizer with a 4mm stainless steel mesh sieve to obtain silica gel powder of 20–200μm. The silica gel powder was set aside for later use.

[0062] Weigh 100 kg of silica gel powder into a 200 L enamel-lined reactor A, add 100 kg of tap water, and adjust the pH of the system to 9.0 ± 0.2 using saturated sodium bicarbonate. Turn on the cooling reflux device and begin heating the reactor to 98 °C for aging. Stop heating after 14 hours. Add dilute sulfuric acid to the reactor to adjust the pH to 6.0–6.5, and continue aging for 24 hours. Open the bottom valve and transfer the aged liquid to a plate and frame filter press with an 800-mesh filter cloth for filtration. Wash with high-purity water until the pH of the discharged water is measured to be 6.5–7.0. Washing is now complete. Transfer the filter cake to reactor B, add 100 kg of high-purity water and 10 kg of silica sol with a particle size of 10 nm–15 nm and a concentration of 20%. Start the agitator and adjust the linear speed to 60 meters per minute. Stir for 10 hours. After stirring, spray dry the resulting slurry and then calcine it in an 800-degree high-temperature furnace for 3 hours to obtain the silica carrier product.

[0063] The following are the results of physicochemical property testing of three parallel samples selected using the same sampling method as in Example 3, with the same testing conditions as in Example 2. The results are shown in Table 5:

[0064] Table 5

[0065]

[0066] Example 4

[0067] Under room temperature (25±2℃) conditions, water glass (modulus 3.2, SiO2 content 25wt%) and dilute sulfuric acid (concentration 45wt%) of the same specifications as in Example 3 were selected as raw materials. The water glass pump flow rate was adjusted to 1.4 m³ / h, and the sulfuric acid pump flow rate was adjusted to 0.7 m³ / h. 0.7 m³ of water glass with a silica concentration of 25wt% and 0.35 m³ of sulfuric acid solution with a concentration of 45wt% were simultaneously injected into a 1000L stainless steel reaction tank over a period of 30 minutes, forming a silica liquid. After standing for 48 hours, the silica liquid gelled, forming a silica gel and acidic water. After the acidic water was discharged, the silica gel was manually scraped and broken into 15mm pieces using a shovel. The 15mm pieces were then further pulverized using a stainless steel multi-functional pulverizer with a 4mm stainless steel mesh sieve to obtain silica gel powder of 20–200 μm. The silica gel powder was set aside for later use.

[0068] Weigh 100 kg of silica gel powder into a 200 L enamel-lined reactor A, add 100 kg of tap water, and adjust the pH of the system to 9.0 ± 0.2 using saturated sodium bicarbonate. Turn on the cooling reflux device and begin heating the reactor to 100 °C for aging. Stop heating after 14 hours. Add dilute sulfuric acid to the reactor to adjust the pH to 6.0–6.5, and continue aging for 36 hours. Open the bottom valve and transfer the aged liquid to a plate and frame filter press with an 800-mesh filter cloth for filtration. Wash with high-purity water until the pH of the discharged water is measured to be 6.5–7.0. Washing is now complete. Transfer the filter cake to reactor B, add 100 kg of high-purity water and 12 kg of silica sol with a particle size of 10 nm–15 nm and a concentration of 20%. Start the agitator and adjust the linear speed to 70 meters per minute. Stir for 12 hours. After stirring, spray dry the resulting slurry and then calcine it in a 900-degree high-temperature furnace for 2.5 hours to obtain the silica carrier product.

[0069] The following are the results of physicochemical property testing of three parallel samples selected using the same sampling method as in Example 3, with the same testing conditions as in Example 3. The results are shown in Table 6:

[0070] Table 6

[0071]

[0072] Example 5

[0073] Under room temperature (25±2℃) conditions, water glass (modulus 3.2, SiO2 content 25wt%) and dilute sulfuric acid (concentration 45wt%) of the same specifications as in Example 4 were selected as raw materials. The water glass pump flow rate was adjusted to 1.2 m³ / h, and the sulfuric acid pump flow rate was adjusted to 0.6 m³ / h. 0.6 m³ of water glass with a silica concentration of 25wt% and 0.3 m³ of sulfuric acid solution with a concentration of 45wt% were simultaneously injected into a 1000L stainless steel reaction tank over a period of 30 minutes, forming a silica liquid. After standing for 48 hours, the silica liquid gelled, forming a silica gel and acidic water. After the acidic water was discharged, the silica gel was manually scraped and broken into 15mm pieces using a shovel. The 15mm pieces were then further pulverized using a stainless steel multi-functional pulverizer with a 4mm stainless steel mesh sieve to obtain silica gel powder of 20–200μm. The silica gel powder was set aside for later use.

[0074] Weigh 90 kg of silica gel powder into a 200 L enamel-lined reactor A, add 90 kg of tap water, and adjust the pH of the system to 9.0 ± 0.2 using saturated sodium bicarbonate. Turn on the cooling reflux device and begin heating the reactor to 96 °C for aging. Stop heating after 16 hours. Add dilute sulfuric acid to the reactor to adjust the pH to 6.0–6.5, and continue aging for 32 hours. Open the bottom valve and transfer the aged liquid to a plate and frame filter press with an 800-mesh filter cloth for filtration. Wash with high-purity water until the pH of the discharged water is measured to be 6.5–7.0. Washing is now complete. Transfer the filter cake to reactor B, add 90 kg of high-purity water and 13.5 kg of silica sol with a particle size of 10 nm–15 nm and a concentration of 20%. Start the agitator and adjust the linear speed to 70 meters per minute. Stir for 12 hours. After stirring, spray dry the resulting slurry and then calcine it in a 900-degree high-temperature furnace for 3 hours to obtain the silica carrier product.

[0075] The following are the results of physicochemical property testing of three parallel samples selected in Example 5 using the same sampling method as in Example 4, with the same test conditions as in Example 4. The results are shown in Table 7:

[0076] Table 7

[0077]

[0078] Example 6

[0079] Under room temperature (25±2℃) conditions, water glass (modulus 3.2, SiO2 content 25wt%) and dilute sulfuric acid (concentration 45wt%) of the same specifications as in Example 4 were selected as raw materials. The water glass pump flow rate was adjusted to 1.2 m³ / h, and the sulfuric acid pump flow rate was adjusted to 0.6 m³ / h. 0.6 m³ of water glass with a silica concentration of 25wt% and 0.3 m³ of sulfuric acid solution with a concentration of 45wt% were simultaneously injected into a 1000L stainless steel reaction tank over a period of 30 minutes to form a silica liquid. After standing for 48 hours, the silica liquid gelled to form a silica gel and acid water. After draining the acid water, the silica gel was manually scraped and broken into 15mm pieces using a shovel. The 15mm pieces were then further pulverized using a stainless steel multi-functional pulverizer with a 4mm stainless steel mesh sieve to obtain 20-200μm silica gel powder, which was set aside for later use.

[0080] Weigh 100 kg of silica gel powder into a 200 L enamel-lined reactor A, add 100 kg of tap water, and adjust the pH of the system to 9.0 ± 0.2 using saturated sodium bicarbonate. Turn on the cooling reflux device and begin heating the reactor to 100 °C for aging. Stop heating after 16 hours. Add dilute sulfuric acid to the reactor to adjust the pH to 6.0–6.5, and continue aging for 28 hours. Open the bottom valve and transfer the aging liquid to a plate and frame filter press with an 800-mesh filter cloth for filtration. Wash with high-purity water until the pH of the discharged water is measured to be 6.5–7.0. Washing is now complete. The filter cake was transferred to reactor B, and 100 kg of high-purity water and 15 kg of silica sol with a particle size of 10 nm to 15 nm and a concentration of 20% were added. The stirring was started and the linear speed was adjusted to 80 m / min. The stirring time was 18 hours. After stirring, the resulting slurry was spray-dried and then calcined in a 900-degree high-temperature furnace for 4 hours to obtain the silica carrier product.

[0081] The following are the results of physicochemical property testing of three parallel samples selected in Example 6 using the same sampling method as in Example 5, with the same testing conditions as in Example 5. The results are shown in Table 8:

[0082] Table 8

[0083]

[0084] Example 7

[0085] Under room temperature (25±2℃) conditions, water glass (modulus 3.2, SiO2 content 25wt%) and dilute sulfuric acid (concentration 45wt%) of the same specifications as in Example 4 were selected as raw materials. The water glass pump flow rate was adjusted to 1.2 m³ / h, and the sulfuric acid pump flow rate was adjusted to 0.6 m³ / h. 0.6 m³ of water glass with a silica concentration of 25wt% and 0.3 m³ of sulfuric acid solution with a concentration of 45wt% were simultaneously injected into a 1000L stainless steel reaction tank over a period of 30 minutes, forming a silica gel liquid. After standing for 48 hours, the silica gel liquid gelled, forming a silica gel and acidic water. After the acidic water was discharged, the silica gel was manually scraped and broken into 15mm pieces using a shovel. The 15mm pieces were then further pulverized using a stainless steel multi-functional pulverizer with a 4mm stainless steel mesh sieve to obtain silica gel powder of 20–200μm. The silica gel powder was set aside for later use.

[0086] Weigh 100 kg of silica gel powder into a 200 L enamel-lined reactor A, add 100 kg of tap water, and adjust the pH of the system to 9.0 ± 0.2 using saturated sodium bicarbonate. Turn on the cooling reflux device and begin heating the reactor to 100 °C for aging. After 16 hours of reaction, stop heating, add dilute sulfuric acid to the reactor to adjust the pH to 6.0–6.5, and continue aging for 48 hours. Open the bottom valve and transfer the aged liquid to a plate and frame filter press with an 800-mesh filter cloth for filtration. Wash with high-purity water until the pH of the discharged water is measured to be 6.5–7.0. Washing is now complete. Transfer the filter cake to reactor B, add 100 kg of high-purity water and 20 kg of silica sol with a particle size of 10 nm–15 nm and a concentration of 20%. Start stirring and adjust the linear speed to 80 m / min, stirring for 24 hours. The resulting slurry, after stirring, is spray-dried and then calcined in a 1000-degree high-temperature furnace for 4 hours to obtain the silica carrier product.

[0087] The following are the results of physicochemical property testing of three parallel samples selected in Example 7 using the same sampling method as in Example 6, with the same testing conditions as in Example 6. The results are shown in Table 9:

[0088] Table 9

[0089]

[0090] Physical performance testing

[0091] The physical properties of the composite silica carriers prepared in Comparative Examples 1 and 2 and Examples 1, 2, 6, and 7 were compared with those of similar products from domestic and international sources. The physicochemical properties of the composite silica carriers are shown in Table 10, where each data point represents the average of the measured data from three parallel products.

[0092] Table 10

[0093]

[0094] Results of physical performance tests (based on Table 10, data are the average values ​​of 3 parallel samples).

[0095] Specific surface area: The products of the embodiments of the present invention have significant advantages. The highest specific surface area in Example 7 is 345.54 m² / g, which far exceeds that of a domestic manufacturer (256.65 m² / g) and a foreign manufacturer (266.82 m² / g). The specific surface area of ​​Comparative Examples 1 and 2 (267.7 and 275.02 m² / g) is close to that of domestic and foreign products.

[0096] Pore ​​volume: Example 7 (1.7862 cm³ / g) is optimal, while Examples 1 and 2 (1.5662, 1.5588 cm³ / g) are comparable to domestic and foreign products (1.557, 1.5449 cm³ / g), and the comparative examples are lower than the examples.

[0097] Pore ​​size: The products in the examples have a pore size distribution of 18.31~23.67nm, which is compatible with domestic and foreign products (23.34, 24.08nm) to meet the industrial catalysis requirements.

[0098] Particle size and bulk density: The particle size (D50) of the product in the example gradually increases with process optimization (28.134~42.025μm), and the bulk density increases simultaneously (0.2141~0.3015g / cm³), adapting to different industrial filling requirements.

[0099] The composite silica support obtained by the continuous steps of material preparation, dispersion filling, flash drying, and calcination of this invention has reasonable preparation cost, simple processing method, uniform particle size distribution, and high mechanical strength. It can meet the requirements of transportation, filling and use in actual production in the fields of chemical industry catalysis and petrochemical catalysis. It is suitable for preparing silica supports for fluidized beds.

[0100] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a high specific surface area composite silica carrier, characterized in that, Includes the following steps: S1. Silica gel was prepared by reacting water glass solution and sulfuric acid solution in a co-current mixing process. S2. After crushing the silica gel, transfer it to reactor A, add water as a solvent, and add saturated sodium bicarbonate solution to reactor A to adjust the pH of the solution to 9.0±0.

2. Then heat and age the solution. S3. After aging is complete, stop the heat preservation and adjust the pH to 6.0-6.

5. Then continue stirring and aging. Then, filter the stirred and aged material using an 800-mesh filter cloth and wash the material with pure water until it is neutral. S4. Transfer the filter cake from the pressure filter to reactor B, and then add high-purity water and silica sol solution to reactor B for dispersion and pore filling. S5. The mixture obtained after dispersion and pore filling is flash-dried to obtain powder, and the powder is then calcined to obtain composite silica carrier product.

2. The method for preparing a high specific surface area composite silica carrier according to claim 1, characterized in that: In step 1, the SiO2 concentration in the water glass solution is 25 wt%, and the concentration of the dilute sulfuric acid solution is 45 wt%.

3. The method for preparing a high specific surface area composite silica carrier according to claim 1, characterized in that: In step 1, the flow rate of the water glass solution in the co-current mixing reaction is 1–3.0 m³ / h, the flow rate of the dilute sulfuric acid solution is 0.5–1.5 m³ / h, and the mixing ratio is 2:

1.

4. The method for preparing a high specific surface area composite silica carrier according to claim 1, characterized in that: In step 2, the silicone gel is pulverized using a stainless steel multi-functional pulverizer with a 4mm stainless steel mesh screen. The particle size distribution of the pulverized powder is 20-200μm. The aging reaction temperature is ≥95℃, the reaction time is 8-16 hours, and the mass ratio of water added to silicone gel powder is 1:

1.

5. The method for preparing a high specific surface area composite silica carrier according to claim 1, characterized in that: In step 3, dilute sulfuric acid is used to adjust the pH to 6.0-6.

5. During the adjustment process, the stirring rate is maintained at 30-50 r / min. The aging process is continuous stirring aging, the aging temperature is room temperature, and the aging time is 24-48 hours. The neutrality criterion is that the pH of the washing effluent is 6.5-7.

0.

6. The method for preparing a high specific surface area composite silica carrier according to claim 1, characterized in that: In step 4, the silica sol is an alkaline silica sol with a particle size of 10nm to 15nm, a silica sol concentration of 20wt%, and the amount of silica sol added is 5% to 20% of the filter cake mass. The filter cake is the wet filter cake that has not been dried after washing in step 3.

7. The method for preparing a high specific surface area composite silica carrier according to claim 1, characterized in that: In step 4, the amount of high-purity water added is 1 times the mass of the filter cake. The dispersion and filling of the pores is carried out by mechanical stirring. The stirrer is an anchor stirrer with a stirring linear speed of ≥60 m / min and a stirring time of ≥8 h. During the stirring process, the system temperature is maintained at 25~35℃.

8. The method for preparing a high specific surface area composite silica carrier according to claim 1, characterized in that: In step 5, the flash drying is carried out using centrifugal spray drying, with an inlet air temperature of 200-250℃ and an outlet air temperature of 80-100℃; the calcination is carried out in an air atmosphere, with a calcination temperature of 600-1000℃, a calcination time of 2-4 hours, and a calcination heating rate of 5-10℃ / min. After calcination, the material is naturally cooled to room temperature to obtain a composite silica carrier.

9. A high specific surface area composite silica carrier prepared by the method according to any one of claims 1-8, characterized in that, The carrier has a porous mesh structure with a supporting framework formed by silica sol filling inside. The average pore size of the carrier is 20-23 nm and the specific surface area is 300-260 m² / g.

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