A method for solid phase synthesis of molecular sieve by using rice husk as silicon source and template

Abstract

The application discloses a method for synthesizing molecular sieve by using rice hull as a silicon source and a template, and comprises the following steps: (1) soaking rice hull powder in a hydrochloric acid solution, then heating the rice hull powder in an oil bath to remove impurities, then washing the obtained suspension with deionized water until neutral, and then drying the suspension in an oven; (2) grinding and mixing the material obtained in the step (1), a structure directing agent, NaAlO2 and NaOH uniformly, and then crystallizing, wherein the structure directing agent is tetrapropylammonium hydroxide and / or n-butylamine; (3) high-temperature calcining the material obtained in the step (2) to remove organic cellulose and template components, and thus the molecular sieve is obtained. The application effectively solves the problems of large wastewater discharge and high cost in the preparation process of traditional molecular sieve.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of waste biomass resource utilization, and specifically relates to a method for solid-phase synthesis of molecular sieves using rice hulls as a silicon source and template. BACKGROUND

[0002] According to the grain yield data released by the National Bureau of Statistics, the total yield of rice in China in 2023 reached 206.6 million tons. As one of the main agricultural by-products of processing rice, rice hulls account for about 20% of the total mass of rice, approximately 41.32 million tons. Traditionally, rice hulls, as agricultural waste, are often directly burned or discarded, which has a serious impact on the environment. However, with increasing emphasis on sustainable development and resource recycling, the rational resource utilization of rice hulls has been given new value. Studies have shown that the silicon content in rice hulls products after high-temperature roasting can reach more than 90%, which makes silicon-rich rice hulls have potential application value in the preparation of molecular sieve materials.

[0003] Molecular sieves have been widely used in catalytic pyrolysis reaction research due to their excellent thermal stability, suitable acid properties, and unique pore structure. However, the traditional hydrothermal method for preparing molecular sieves produces a large amount of wastewater, which not only pollutes the environment but also increases production costs. Therefore, it is of great significance to develop a simple and environmentally friendly molecular sieve preparation technology.

[0004] CN 105731485A discloses a method for preparing a hierarchical pore zeolite molecular sieve by using rice husk. The synthesis process needs to consume a large amount of water, and the specific synthesis steps are as follows: 30-35 parts of rice husk, 5-8 parts of NaAlO2, 45-55 parts of deionized water, 3-5 parts of NaOH and 0.5-0.8 parts of TPAOH are selected by weight fraction, uniformly mixed and stirred, then added into a stainless steel reaction kettle, heated to 150-160℃, taken out after 20-30h of reaction, centrifuged to obtain a precipitate, washed with deionized water for 2-4 times, and then dried in an oven at 80-100℃. After drying, the precipitate is placed in a muffle furnace and calcined at 500-600℃ for 4-6h, and then the obtained crystal is taken out after cooling. Then, 5-7g of NaAlO2 and 20-25g of NaOH are dissolved in 600-650mL of distilled water, stirred until the solid is completely dissolved, then 50-60g of white carbon black is added, and stirred and mixed for 2-3h to form a gel. 3-5% of the above crystal is added to the gel as a seed crystal, and after stirring and dispersing uniformly, the mixed gel is added to a stainless steel reaction kettle, and crystallized at 130-140℃ for 50-80h. After the crystallization is completed, the product is repeatedly washed with deionized water until the filtrate is neutral, and then the washed product is placed in an oven at 100-120℃ for 6-8h to dry, and a hierarchical pore zeolite molecular sieve is obtained. Although the above prior art successfully prepares a molecular sieve by using rice husk, the preparation process is complex and a large amount of wastewater is generated. SUMMARY

[0005] The present application aims to overcome the defects of the prior art and provide a method for solid-phase synthesis of a molecular sieve by using rice husk as a silicon source and a template.

[0006] The technical solution of the present application is as follows:

[0007] A method for solid-phase synthesis of a molecular sieve by using rice husk as a silicon source and a template, comprising the following steps:

[0008] (1) At room temperature, the rice husk powder is soaked in a hydrochloric acid solution for 6-24h, and then heated in an oil bath at 80-130℃ for 10min-1h to remove impurities, and then the obtained suspension is washed with deionized water until neutral, and then dried in an oven;

[0009] (2) The material obtained in step (1), a structure directing agent, NaAlO2 and NaOH are mixed in a ratio of 1.8-2.2g:3.5-4.5mL:0.008-0.012g:0-0.12g, and then fully ground and mixed uniformly, and then crystallized at 100-200℃ for 10-48h, and the structure directing agent is tetrapropylammonium hydroxide and / or n-butylamine;

[0010] (3) The material obtained in step (2) is calcined at 500-600℃ for 1-3 hours to remove organic cellulose and template components, thereby obtaining the molecular sieve.

[0011] In a preferred embodiment of the present invention, in step (1), the concentration of the hydrochloric acid solution is 2-15 wt%.

[0012] More preferably, in step (1), the ratio of rice husk powder to hydrochloric acid solution is 50-80g:1-2L.

[0013] In a preferred embodiment of the present invention, in step (2), the crystallization temperature is 110-170°C and the time is 12-48h.

[0014] In a preferred embodiment of the present invention, in step (3), the high-temperature calcination temperature is 540-560°C and the time is 1.5-2.5h.

[0015] More preferably, in step (3), the heating rate of the high-temperature roasting is 2-5℃ / min.

[0016] In a preferred embodiment of the present invention, in step (1), the concentration of the hydrochloric acid solution is 2-15 wt%; in step (2), the crystallization temperature is 110-170°C and the time is 12-48 h; in step (3), the high-temperature calcination temperature is 540-560°C and the time is 1.5-2.5 h.

[0017] More preferably, in step (1), the ratio of rice husk powder to hydrochloric acid solution is 50-80g:1-2L.

[0018] More preferably, in step (3), the heating rate of the high-temperature roasting is 2-5℃ / min.

[0019] More preferably, in step (1), the ratio of rice husk powder to hydrochloric acid solution is 50-80g:1-2L; in step (3), the heating rate of the high-temperature roasting is 2-5℃ / min.

[0020] The beneficial effects of this invention are:

[0021] 1. This invention uses rice husks as a silicon source and template agent to prepare molecular sieves through a simple solid-phase synthesis method. During the synthesis process, by precisely controlling key parameters such as crystallization temperature, crystallization time, and the type and amount of template agent, highly crystalline molecular sieves can be prepared. This method effectively solves the problems of large wastewater discharge and high costs in traditional molecular sieve preparation processes.

[0022] 2、The method is simple, energy-saving and environment-friendly, and can promote the high value-added utilization of agricultural waste, realizing the dual benefits of resourceization and environmental friendliness of waste. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The X-ray diffractometer spectrum of the molecular sieve obtained under different synthesis conditions for Examples 1 to 8 of the present application was characterized by an X-ray powder diffractometer produced by Rigaku Company, model SmartLab, equipped with a Cu Kα radiation source of 40 kV and 30 mA The detection range is 5-50°.

[0024] Figure 2 The scanning electron microscope photos of the molecular sieve prepared in Examples 1 to 8 of the present application were characterized by a field emission scanning electron microscope produced by Hitachi Company, equipment model SU5500. DETAILED DESCRIPTION

[0025] The technical solutions of the present application are further described and explained below by specific embodiments in conjunction with the drawings.

[0026] Example 1

[0027] (1) 70 g of rice hull powder (mesh size 120) was soaked in 1 L of 5 wt% hydrochloric acid solution at room temperature for 24 h, then heated in an oil bath at 100 ℃ for 30 min to remove impurities, then washed with deionized water to neutral, and then dried in an oven at 80 ℃ for 12 h;

[0028] (2) 2 g of the material obtained in step (1), 4 mL of structure-directing agent TPAOH, and 0.01 g of NaAlO2 were thoroughly ground and mixed, and then crystallized in a high-pressure reaction kettle at 110 ℃ for 30 h;

[0029] (3) The material obtained in step (2) was placed in a muffle furnace and heated at a rate of 2 ℃ / min to 550 ℃, and then calcined at 550 ℃ for 2 h to remove organic cellulose and template components, thereby obtaining the molecular sieve as shown in Figure 1 .

[0030] Figure 1 The XRD spectrum results of the molecular sieve prepared in this example showed that the molecular sieve prepared in this example had good crystallinity, and the sample diffraction peak was consistent with the standard card (JCPDS No. 44-0003) diffraction peak. The crystallinity of the sample was calculated in the diffraction angle range of 15-30°, and the crystallinity of Example 1 was 90.2%. As shown in Figure 2 (a), the molecular sieve prepared in this example showed a blocky microstructure under scanning electron microscope magnification.

[0031] Example 2

[0032] (1) 70 g of rice husk powder (120 mesh) was soaked in 1 L of 5 wt% hydrochloric acid solution at room temperature for 24 h, and then heated in an oil bath at 100 °C for 30 min to remove impurities. The obtained suspension was then washed with deionized water until neutral, and then dried in an oven at 80 °C for 12 h;

[0033] (2) 2 g of the material obtained in step (1), 4 mL of structure directing agent TPAOH, and 0.01 g of NaAlO2 were thoroughly ground and mixed, and then crystallized in a high-pressure reaction kettle at 140 °C for 12 h;

[0034] (3) The material obtained in step (2) was placed in a muffle furnace and heated at a rate of 2 °C / min to 550 °C, and then calcined at 550 °C for 2 h to remove organic cellulose and template components, thereby obtaining the molecular sieve as shown in Figure 1 .

[0035] Figure 1 The XRD spectrum of the molecular sieve prepared in this example showed that the molecular sieve had good crystallinity, and the sample diffraction peak was consistent with the standard card (JCPDS No. 44-0003). The crystallinity of the sample was calculated in the diffraction angle range of 15-30°, and the crystallinity of Example 2 was 91.8%. As shown in Figure 2 (b), the molecular sieve prepared in this example showed a blocky microstructure under scanning electron microscope.

[0036] Example 3

[0037] (1) 70 g of rice husk powder (120 mesh) was soaked in 1 L of 5 wt% hydrochloric acid solution at room temperature for 24 h, and then heated in an oil bath at 100 °C for 30 min to remove impurities. The obtained suspension was then washed with deionized water until neutral, and then dried in an oven at 80 °C for 12 h;

[0038] (2) 2 g of the material obtained in step (1), 4 mL of structure directing agent TPAOH, and 0.01 g of NaAlO2 were thoroughly ground and mixed, and then crystallized in a high-pressure reaction kettle at 140 °C for 48 h;

[0039] (3) The material obtained in step (2) was placed in a muffle furnace and heated at a rate of 2 °C / min to 550 °C, and then calcined at 550 °C for 2 h to remove organic cellulose and template components, thereby obtaining the molecular sieve as shown in Figure 1 and Figure 2 .

[0040] Figure 1The XRD spectrum results of the molecular sieve prepared in this example show that the molecular sieve has good crystallinity, the sample diffraction peaks are consistent with the standard card (JCPDS No. 44-0003) diffraction peaks, and the crystallinity of the sample is calculated in the diffraction angle of 15-30° interval, and the crystallinity of Example 3 is 92.5%. As shown in Figure 2 (c), the molecular sieve prepared in this example shows a blocky microstructure under scanning electron microscope.

[0041] Example 4

[0042] (1) 70 g of rice husk powder (120 mesh) was soaked in 1 L of 5 wt% hydrochloric acid solution at room temperature for 24 h, then heated in an oil bath at 100°C for 30 min to remove impurities, then the obtained suspension was washed with deionized water until neutral, and then dried in an oven at 80°C for 12 h;

[0043] (2) 2 g of the material obtained in step (1), 4 mL of structure directing agent TPAOH, and 0.01 g of NaAlO2 were thoroughly ground and mixed, and then crystallized in a high-pressure reaction kettle at 170°C for 30 h;

[0044] (3) The material obtained in step (2) was placed in a muffle furnace and heated at a rate of 2°C / min to 550°C, and then calcined at 550°C for 2 h to remove organic cellulose and template components, thereby obtaining the molecular sieve as shown in Figure 1 and Figure 2 .

[0045] Figure 1 The XRD spectrum results of the molecular sieve prepared in this example show that the molecular sieve has good crystallinity, the sample diffraction peaks are consistent with the standard card (JCPDS No. 44-0003) diffraction peaks, and the crystallinity of the sample is calculated in the diffraction angle of 15-30° interval, and the crystallinity of Example 4 is 93.3%. As shown in Figure 2 (d), the molecular sieve prepared in this example mainly shows a blocky microstructure under scanning electron microscope.

[0046] Example 5

[0047] (1) 50 g of rice husk powder (120 mesh) was soaked in 2 L of 2 wt% hydrochloric acid solution at room temperature for 24 h, then heated in an oil bath at 130°C for 30 min to remove impurities, then the obtained suspension was washed with deionized water until neutral, and then dried in an oven at 80°C for 12 h;

[0048] (2) 2 g of the material obtained in step (1), 2 mL of structure-directing agent TPAOH, 2 mL of structure-directing agent n-butylamine, and 0.01 g of NaAlO2 were thoroughly ground and uniformly mixed, and then crystallization was performed at 170°C for 30 h in an autoclave;

[0049] (3) The material obtained in step (2) was placed in a muffle furnace, heated to 550°C at a rate of 5°C / min, and then calcined at 550°C for 2 h to remove the organic cellulose and template components, thereby obtaining the molecular sieve.

[0050] Figure 1 The XRD spectrum of the molecular sieve prepared in this example showed that the molecular sieve prepared in this example had good crystallinity, and the diffraction peaks of the sample were consistent with the diffraction peaks of the standard card (JCPDS No. 44-0003). The crystallinity of the sample was calculated in the range of diffraction angles of 15-30°, and the crystallinity of the sample was 93.5%. As shown in Figure 2 (e), the molecular sieve prepared in this example had a blocky microstructure after being magnified by a scanning electron microscope.

[0051] Example 6

[0052] (1) 80 g of rice hull powder (120 mesh) was soaked in 1 L of 10 wt% hydrochloric acid solution at room temperature for 12 h, and then heated in an oil bath at 80°C for 60 min to remove impurities. Then the obtained suspension was washed with deionized water until neutral, and then dried in an oven at 80°C for 12 h;

[0053] (2) 2 g of the material obtained in step (1), 1 mL of structure-directing agent TPAOH, 3 mL of structure-directing agent n-butylamine, and 0.01 g of NaAlO2 were thoroughly ground and uniformly mixed, and then crystallization was performed at 170°C for 30 h in an autoclave;

[0054] (3) The material obtained in step (2) was placed in a muffle furnace, heated to 550°C at a rate of 2°C / min, and then calcined at 550°C for 2 h to remove the organic cellulose and template components, thereby obtaining the molecular sieve.

[0055] Figure 1 The XRD spectrum of the molecular sieve prepared in this example showed that the molecular sieve prepared in this example had good crystallinity, and the diffraction peaks of the sample were consistent with the diffraction peaks of the standard card (JCPDS No. 44-0003). The crystallinity of the sample was calculated in the range of diffraction angles of 15-30°, and the crystallinity of the sample was 94.3%. As shown in Figure 2 (f), the molecular sieve prepared in this example had a blocky microstructure after being magnified by a scanning electron microscope.

[0056] Example 7

[0057] (1) 80 g of rice husk powder (120 mesh) was soaked in 1 L of 15 wt% hydrochloric acid solution at room temperature for 12 h, and then heated in an oil bath at 80 °C for 10 min to remove impurities. The obtained suspension was washed with deionized water until neutral, and then dried in an oven at 80 °C for 12 h;

[0058] (2) 2 g of the material obtained in step (1), 3 mL of structure-directing agent TPAOH, 1 mL of structure-directing agent n-butylamine, and 0.01 g of NaAlO2 were thoroughly ground and mixed, and then crystallized in a high-pressure reaction kettle at 170 °C for 30 h;

[0059] (3) The material obtained in step (2) was placed in a muffle furnace and heated at a rate of 2 °C / min to 550 °C, and then calcined at 550 °C for 2 h to remove organic cellulose and template components, thereby obtaining the molecular sieve.

[0060] Figure 1 The XRD spectrum of the molecular sieve prepared in this example showed that the molecular sieve had good crystallinity, and the sample diffraction peak was consistent with the standard card (JCPDS No. 44-0003). The crystallinity of the sample was calculated in the diffraction angle range of 15-30°, and the crystallinity of the sample of Example 7 was 95.2%. As shown in FIG. 8, the molecular sieve prepared in this example had a blocky microstructure after scanning electron microscope magnification. Figure 2

[0061] Example 8

[0062] (1) 50 g of rice husk powder (120 mesh) was soaked in 1 L of 2 wt% hydrochloric acid solution at room temperature for 24 h, and then heated in an oil bath at 130 °C for 30 min to remove impurities. The obtained suspension was washed with deionized water until neutral, and then dried in an oven at 80 °C for 12 h;

[0063] (2) 2 g of the material obtained in step (1), 4 mL of structure-directing agent TPAOH, 0.01 g of NaAlO2, and 0.12 g of NaOH (to control the morphology and particle size of the molecular sieve) were thoroughly ground and mixed, and then crystallized in a high-pressure reaction kettle at 170 °C for 30 h;

[0064] (3) The material obtained in step (2) was placed in a muffle furnace and heated at a rate of 5 °C / min to 550 °C, and then calcined at 550 °C for 2 h to remove organic cellulose and template components, thereby obtaining the molecular sieve.

[0065] Figure 1 ​The XRD spectrum results of the molecular sieve prepared in the example show that the molecular sieve has good crystallinity, the sample diffraction peak is consistent with the standard card (JCPDS No. 44-0003) diffraction peak, the crystallinity of the sample in the diffraction angle of 15-30° interval is calculated, and the crystallinity of the example 8 is 94.7%. As shown in Fig. 8, the molecular sieve prepared in the example is in a block microstructure after scanning electron microscope amplification. Figure 2 (h) As shown in the scanning electron microscope amplification, the molecular sieve prepared in the example is in a block microstructure.

[0066] The above is only a preferred embodiment of the present application, and therefore cannot limit the scope of the present application. Any equivalent changes and modifications made in accordance with the scope of the present application and the content of the specification should still be within the scope of the present application.

Claims

1. A method for solid-phase synthesis of molecular sieves using rice husks as a silicon source and template, characterized in that: Includes the following steps: (1) At room temperature, rice husk powder is soaked in hydrochloric acid solution for 6-24 h, and then heated in an oil bath at 80-130 ℃ for 10 min-1 h to remove impurities. The resulting suspension is then washed with deionized water until neutral and then dried in an oven. (2) The material obtained in step (1), the structure directing agent, NaAlO2 and NaOH are thoroughly ground and mixed in a ratio of 1.8-2.2 g: 3.5-4.5 mL: 0.008-0.012 g: 0-0.12 g, and then crystallized at 100-200 °C for 10-48 h. The structure directing agent is tetrapropylammonium hydroxide and / or n-butylamine. (3) The material obtained in step (2) is calcined at 500-600 ℃ for 1-3 h to remove organic cellulose and template components, thereby obtaining the molecular sieve.

2. The method as described in claim 1, characterized in that: In step (1), the concentration of the hydrochloric acid solution is 2-15 wt%.

3. The method as described in claim 2, characterized in that: In step (1), the ratio of rice husk powder to hydrochloric acid solution is 50-80 g: 1-2 L.

4. The method as described in claim 1, characterized in that: In step (2), the crystallization temperature is 110-170℃ and the time is 12-48 h.

5. The method as described in claim 1, characterized in that: In step (3), the high-temperature calcination temperature is 540-560 ℃ and the time is 1.5-2.5 h.

6. The method as described in claim 5, characterized in that: In step (3), the heating rate of the high-temperature calcination is 2-5 ℃ / min.

7. The method as described in claim 1, characterized in that: In step (1), the concentration of the hydrochloric acid solution is 2-15 wt%; in step (2), the crystallization temperature is 110-170 ℃ and the time is 12-48 h; in step (3), the high-temperature calcination temperature is 540-560 ℃ and the time is 1.5-2.5 h.

8. The method as described in claim 7, characterized in that: In step (1), the ratio of rice husk powder to hydrochloric acid solution is 50-80 g: 1-2 L.

9. The method as described in claim 7, characterized in that: In step (3), the heating rate of the high-temperature roasting is 2-5 ℃ / min.

10. The method as described in claim 7, characterized in that: In step (1), the ratio of rice husk powder to hydrochloric acid solution is 50-80 g: 1-2 L; in step (3), the heating rate of high-temperature roasting is 2-5 ℃ / min.

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