Structural stability roasting method of silochrom

Abstract

The invention belongs to the technical field of spherical silicon oxide, and particularly relates to a structural stability roasting method of silochrom. The method comprises the following steps: 1) putting silochrom prepared by a sol-gel method into a roasting furnace, and introducing an ammonia gas atmosphere to replace air in the furnace; (2) carrying out roasting treatment in an ammonia gas atmosphere; (3) after the temperature is reduced, inert atmosphere is introduced for purging, and the silochrom with the stable structure is finally obtained.According to the silochrom obtained through roasting with the method, the structural stability is remarkably improved, the silochrom can have the excellent mechanical strength while the macroporous structure is kept, specifically, the strength of the obtained silochrom is not lower than 100 N / particle, and the pore volume is not lower than 0.90 cm / g.

Description

Technical Field

[0001] This invention belongs to the field of spherical silicon oxide technology, specifically relating to a method for calcining coarse-porous silica gel to stabilize its structure. Background Technology

[0002] The sol-gel method is a commonly used process for preparing spherical silicone rubber. However, after the drying process of the gel spheres, a certain number of hydroxyl groups often remain on the surface of the product, and its internal cross-linked structure is not yet fully stable, resulting in some internal stress. These factors typically lead to low mechanical strength in the finished silicone rubber product. Therefore, a high-temperature calcination process is usually used to further remove the residual hydroxyl groups and stabilize and homogenize the internal structure, thereby significantly improving the mechanical strength of the silicone rubber product.

[0003] Currently, conventional calcination is usually carried out in an air atmosphere. However, this process has certain limitations: when the calcination temperature is low, hydroxyl groups are not completely removed and the structural stabilization is insufficient, resulting in limited improvement in the mechanical strength of silica gel; while when the temperature is too high, local sintering is easily caused, resulting in the destruction of the microporous structure of silica gel, specifically manifested as a significant decrease in specific surface area and pore volume, which in turn affects its application performance in adsorption, catalysis, chromatographic separation and other fields.

[0004] With the increasingly widespread application of silica gel as a catalyst carrier, adsorbent, and chromatographic packing material in industries such as petrochemicals, biopharmaceuticals, and environmental remediation, higher requirements are being placed on its mechanical strength, pore structure stability, and specific surface area. Therefore, existing high-temperature calcination processes in air atmosphere are insufficient to simultaneously improve mechanical strength and effectively maintain the pore structure. The market urgently needs a novel processing technology that can effectively suppress sintering during calcination and maintain high specific surface area and suitable pore structure while improving the mechanical strength of silica gel. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a calcination method for improving the structural stability of coarse-porous silica gel, which addresses the shortcomings of the existing technology. The coarse-porous silica gel obtained by the calcination method has a strength of not less than 100 N / particle and a pore volume of not less than 0.90 cm³ / g.

[0006] To address the technical problem proposed in this invention, this invention provides a method for calcining coarse-porous silica gel to stabilize its structure, comprising calcining coarse-porous silica gel prepared by the sol-gel method in an ammonia atmosphere.

[0007] Furthermore, including: (1) Place the coarse-porous silica gel prepared by the sol-gel method in a calcination furnace and introduce an ammonia atmosphere to replace the air in the furnace; (2) Calcination treatment is carried out under an ammonia atmosphere; (3) After cooling, an inert atmosphere is introduced for purging.

[0008] Furthermore, in the ammonia atmosphere, the volume fraction of ammonia is 50% to 100%, and the remainder is inert gas.

[0009] Furthermore, in the inert atmosphere, the inert gas is nitrogen or argon, and the volume fraction of the inert gas is ≥99%.

[0010] Furthermore, in step (1), the mass hourly space velocity (MSV) of the ammonia atmosphere is 0.05~1 h⁻¹. -1 The replacement time is 0.5 to 4 hours.

[0011] Furthermore, in step (2), the mass hourly space velocity (MSV) of the ammonia atmosphere is 0.1–5 h⁻¹. -1 .

[0012] Further, in step (2), the conditions for the calcination treatment include: a heating rate of 1~20 ℃ / min, a calcination temperature of 500~800℃, and a calcination time of 1~24 h.

[0013] Furthermore, in step (3), the cooling conditions include: cooling rate ≤ 200℃ / h, and temperature reduced to 100~300℃.

[0014] Furthermore, in step (3), the mass space velocity of the inert atmosphere is 0.05~1 h⁻¹. -1 The temperature after purging is 10~50℃.

[0015] The present invention also provides a silica gel prepared by the above method, wherein the silica gel has a strength of not less than 100 N / particle and a pore volume of not less than 0.90 cm³ / g.

[0016] Compared with the prior art, the beneficial technical effects of the present invention include: This invention, by introducing an ammonia atmosphere during heat treatment, effectively achieves the calcination objectives (such as further removing residual hydroxyl groups and enhancing crosslinking stability) while significantly inhibiting or delaying the sintering and densification process of silica gel at high temperatures, thus significantly improving its structural stability. This process effectively balances the contradiction between structural strengthening and porosity retention, enabling the obtained coarse-porous silica gel to maintain excellent pore structure characteristics while achieving a high mechanical strength of no less than 100 N / particle, with a pore volume of no less than 0.90 cm³ / g, thereby achieving an overall balance between high strength and high porosity. Detailed Implementation

[0017] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] In the following examples, the coarse-porous silica gel used was prepared by the sol-gel method using air granulation. The specific steps are as follows: 1) Water glass with a modulus of 3.2 and a sodium oxide content of 15 wt% and sulfuric acid with a concentration of 15 wt% are pumped into the reactor. The water glass flow rate is 10 m³ / s. 3 / h, sulfuric acid flow rate 3 m 3 / h, the molar ratio of sulfuric acid to sodium oxide is 1.05:1. After being mixed evenly, the mixture is sprayed into the water tank through a nozzle to obtain spherical gel balls; 2) Place the spherical gel balls in a water tank for 4 hours to allow the silica gel network to further condense and initially form pores; 3) Subsequently, it was placed in an oven at 100℃ and dried for 12 h to obtain a strength of 62.50 N / particle and a specific surface area of ​​481 m². 2 / g, pore volume 0.96 cm³ 3 / g of coarse-pore silica gel. Example 1

[0019] A method for calcining coarse-porous silica gel to stabilize its structure, comprising the following steps: 1) Place 5 g of coarse-porous silica gel prepared by the sol-gel method in a tube furnace. First, introduce ammonia gas to replace the air in the furnace tube. The ammonia gas integral is 99.5%, the gas flow rate is 20 sccm, and the replacement time is 1 h. 2) After the replacement is completed, a preset heating program is executed under an ammonia atmosphere for calcination treatment, wherein the ammonia gas integral is 99.5%, the gas flow rate is 50 sccm, the heating rate of the calcination treatment is 5 ℃ / min, the calcination temperature is 800℃, and the calcination time is 12 h. 3) After calcination, allow the furnace to cool naturally at a rate of approximately 100 °C / h. When the temperature drops to 200 °C, switch the atmosphere to nitrogen with a volume fraction of 99.5% and continue purging at a gas flow rate of 20 sccm until the temperature is cooled to 25 °C, thus obtaining structurally stable coarse-porous silica gel. Example 2

[0020] A method for calcining coarse-porous silica gel to stabilize its structure, comprising the following steps: 1) Place 5 g of coarse-porous silica gel prepared by the sol-gel method in a tube furnace. First, introduce ammonia gas to replace the air in the furnace tube. The ammonia gas integral is 99.5%, the gas flow rate is 20 sccm, and the replacement time is 1 h. 2) After the replacement is completed, a preset heating program is executed under an ammonia atmosphere for calcination treatment, wherein the ammonia gas integral is 99.5%, the gas flow rate is 50 sccm, the heating rate of the calcination treatment is 5 ℃ / min, the calcination temperature is 500℃, and the calcination time is 12 h. 3) After calcination, allow the furnace to cool naturally at a rate of approximately 100 °C / h. When the temperature drops to 200 °C, switch the atmosphere to nitrogen with a volume fraction of 99.5% and continue purging at a gas flow rate of 20 sccm until the temperature is cooled to 25 °C, thus obtaining structurally stable coarse-porous silica gel. Example 3

[0021] A method for calcining coarse-porous silica gel to stabilize its structure, comprising the following steps: 1) Place 5 g of coarse-porous silica gel prepared by the sol-gel method in a tube furnace. First, introduce ammonia gas to replace the air in the furnace tube. The ammonia gas integral is 99.5%, the gas flow rate is 20 sccm, and the replacement time is 1 h. 2) After the replacement is completed, a preset heating program is executed under an ammonia atmosphere for calcination treatment, wherein the ammonia gas integral is 99.5%, the gas flow rate is 50 sccm, the heating rate of the calcination treatment is 5 ℃ / min, the calcination temperature is 600℃, and the calcination time is 24 h. 3) After calcination, allow the furnace to cool naturally at a rate of approximately 100 °C / h. When the temperature drops to 200 °C, switch the atmosphere to nitrogen with a volume fraction of 99.5% and continue purging at a gas flow rate of 20 sccm until the temperature is cooled to 25 °C, thus obtaining structurally stable coarse-porous silica gel. Comparative Example 1

[0022] A method for calcining coarse-porous silica gel to stabilize its structure, comprising the following steps: 1) Place 5 g of coarse-porous silica gel prepared by the sol-gel method in a tube furnace. First, introduce ammonia gas to replace the air in the furnace tube. The ammonia gas integral is 99.5%, the gas flow rate is 20 sccm, and the replacement time is 1 h. 2) After the replacement is completed, a preset heating program is executed under an ammonia atmosphere for calcination treatment, wherein the ammonia gas integral is 99.5%, the gas flow rate is 50 sccm, the heating rate of the calcination treatment is 5 ℃ / min, the calcination temperature is 400℃, and the calcination time is 12 h. 3) After calcination, allow the furnace to cool naturally at a rate of approximately 100 °C / h. When the temperature drops to 200 °C, switch the atmosphere to nitrogen with a volume fraction of 99.5% and continue purging at a gas flow rate of 20 sccm until the temperature is cooled to 25 °C, thus obtaining structurally stable coarse-porous silica gel. Comparative Example 2

[0023] A method for calcining coarse-porous silica gel to stabilize its structure, comprising the following steps: 1) Place 5 g of coarse-porous silica gel prepared by the sol-gel method in a tube furnace. First, introduce nitrogen gas to replace the air in the furnace tube. The nitrogen gas integral is 99.5%, the gas flow rate is 20 sccm, and the replacement time is 1 h. 2) After the replacement is completed, a preset heating program is executed under a nitrogen atmosphere for calcination treatment, wherein the nitrogen gas fraction is 99.5% and the gas flow rate is 50 sccm; the heating rate of the calcination treatment is 5 ℃ / min; when the temperature reaches 150℃, the atmosphere is switched to water vapor with a volume fraction of 100% and a gas flow rate of 50 sccm, and calcination continues at a temperature of 800℃ for 12 h. 3) After calcination, allow the furnace to cool naturally at a rate of approximately 100 °C / h. When the temperature drops to 200 °C, switch the atmosphere to nitrogen with a volume fraction of 99.5% and continuously purge at a flow rate of 20 sccm until the temperature is cooled to 25 °C, ultimately obtaining silica gel with its microporous structure destroyed. Comparative Example 3

[0024] A method for calcining coarse-porous silica gel to stabilize its structure, comprising the following steps: 1) Place 5 g of coarse-porous silica gel prepared by the sol-gel method in a tube furnace without replacing the air inside the tube; 2) The pre-set heating program was executed in an air atmosphere for calcination treatment. The heating rate of the calcination treatment was 5℃ / min, the calcination temperature was 800℃, and the calcination time was 12 h. 3) After calcination, allow the furnace to cool naturally at a rate of approximately 100 ℃ / h until it cools to 25 ℃, ultimately obtaining silica gel with its microporous structure destroyed.

[0025] The performance of the silicone products obtained in the examples and comparative examples was tested, and the results are shown in Table 1.

[0026] Table 1. Performance Test Results of Silicone Products

[0027] The specific surface area, pore volume, and strength of the samples prepared in the examples were determined. Specific surface area and pore volume were measured using a McMurray Tic-ASAP2460 specific surface area and porosity analyzer via the BET method. The crushing strength of the small spheres was tested using a DL4 particle strength tester, with an average sphere diameter of 3 mm.

[0028] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for improving the structural stability of a coarse-pored silica gel by calcination, characterized by The crude porous silica gel prepared by the sol-gel method is placed in an ammonia atmosphere for calcination treatment.

2. The method of claim 1, wherein, The method comprises the following steps: (1) placing the crude porous silica gel prepared by the sol-gel method in a calcination furnace, and introducing ammonia gas to replace the air in the furnace; (2) performing calcination treatment under the ammonia atmosphere; (3) after cooling, introducing an inert atmosphere for purging.

3. The method according to claim 1 or 2, characterized in that, In the ammonia atmosphere, the volume fraction of ammonia gas is 50% to 100%, and the rest is inert gas.

4. The method according to any one of claims 1 to 3, characterized in that, In the inert atmosphere, the inert gas is nitrogen or argon, and the volume fraction of the inert gas is greater than or equal to 99%.

5. The method according to any one of claims 1 to 4, characterized in that, In step (1), the mass space velocity of the ammonia atmosphere is 0.05 to 1 h -1 , and the replacement time is 0.5 to 4 h.

6. The method according to any one of claims 1 to 5, characterized in that, In step (2), the mass space velocity of the ammonia atmosphere is 0.1 to 5 h -1 .

7. The method according to any one of claims 1 to 6, characterized in that, In step (2), the calcination treatment conditions include: a heating rate of 1 to 20 ℃ / min, a calcination temperature of 500 to 800 ℃, and a calcination time of 1 to 24 h.

8. The method of any one of claims 1-7, wherein, In step (3), the cooling conditions include: a cooling rate of less than or equal to 200 ℃ / h, and a temperature drop to 100 to 300 ℃.

9. The method according to any one of claims 1 to 8, characterized in that, In step (3), the mass space velocity of the inert atmosphere is 0.05 to 1 h -1 , and the temperature after purging is 10 to 50°C.

10. The silica gel prepared by the method of any one of claims 1 to 9, characterized in that, The strength of the silica gel is not less than 100 N / particle, and the pore volume is not less than 0.90 cm³ / g.

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