A zeolite molecular sieve based on fly ash and waste silicon powder and its preparation method

Abstract

The invention provides a zeolite molecular sieve based on fly ash and waste silicon powder and a preparation method thereof, comprising the following steps: S1: roasting a mixture of silicon powder and fly ash in a mass ratio of (0.5-5):5 at a high temperature to activate the fly ash, wherein the roasting temperature is 850-1300°C and the roasting time is 1-4 hours, and the roasted product is taken out after natural cooling; S2: removing impurities from the silicon roasted activated fly ash with hydrochloric acid, filtering, washing the filter residue with deionized water until the pH value of the filtrate is neutral, and drying the filter residue for standby use; S3: adding a 3 mol / L-10 mol / L NaOH solution to the filter residue, with a solid-liquid ratio of the filter residue to the NaOH solution of 1:8, and stirring to convert the silicon powder, silicon dioxide and aluminum oxide in the filter residue into SiO3 2‑ and AlO2 ‑ The reaction solution is filtered out and the filtrate is set aside; S4: the filtrate is subjected to a hydrothermal reaction to crystallize to obtain a zeolite molecular sieve. The preparation method of the present invention solves the high cost problem of conventional preparation methods and has high commercial value.

Description

Technical Field

[0001] The present invention relates to the technical field of molecular sieve preparation, in particular to a zeolite molecular sieve using fly ash and waste silicon powder as raw materials and a preparation method thereof. Background Art

[0002] Coal combustion produces a large amount of solid fly ash waste. The large amount of fly ash accumulation not only wastes precious land resources, but also brings a huge environmental burden. How to achieve high-value utilization and scientific disposal of fly ash has become a top priority. The main chemical components of fly ash are silicon dioxide and aluminum oxide, accounting for more than 70%, and it is also the synthetic zeolite molecular sieve (the basic molecular formula of zeolite molecular sieve is M n / 2 O·Al2O3·XSiO2·YH2O, where M represents a cation, n represents the valence of the cation, and Y represents the degree of hydration).

[0003] Zeolites are a series of natural and synthetic aluminosilicate materials with catalytic, adsorption, and ion exchange properties. Currently, the main steps for preparing zeolites from fly ash, both domestically and internationally, include alkali roasting to activate the fly ash, acid leaching to remove metal impurities, alkali leaching to extract silicon and aluminum, adding a silicon or aluminum source to the filtrate to adjust the silicon-to-aluminum ratio, and hydrothermal synthesis of the zeolite. Because the glass spheres in fly ash have a layer of mullite (3Al2O3·2SiO2) on their surface, which is neither reactive with acid nor alkaline solutions, alkali roasting is used to activate fly ash. This is done by alkali fusion at high temperatures to partially melt the relatively smooth glass spheres, causing them to collapse locally and expand. This eliminates the mullite (3Al2O3·2SiO2) attached to the glass spheres, facilitating more efficient extraction of active ingredients such as silica and alumina in subsequent steps. However, alkali roasting at high temperatures can also corrode high-temperature sintering equipment, reducing its service life. In addition, before preparing zeolite molecular sieves by the hydrothermal method, it is usually necessary to add a large amount of reagent-grade silicon source (such as silicon dioxide, sodium silicate, silica sol, etc.) to the resulting filtrate to adjust the silicon-aluminum ratio in the target zeolite molecular sieve to an appropriate ratio, which also greatly increases the production cost of the zeolite molecular sieve. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a preparation method of zeolite molecular sieve using fly ash and waste silicon powder as raw materials. In the process of high-temperature roasting and activating fly ash, silicon melting is used instead of the alkali melting method in the conventional preparation method, and at the same time, the problem that a large amount of reagent-grade silicon source needs to be additionally supplemented in the conventional preparation method and the preparation cost is high can be solved.

[0005] To solve the above problems, the present invention provides a method for preparing zeolite molecular sieve using fly ash and waste silicon powder as raw materials, comprising the following steps:

[0006] S1: Calcination of fly ash with silicon: Calcination of a mixture of silicon powder and fly ash in a mass ratio of (0.5-5):5 at a high temperature of 850°C-1300°C for 1-4 hours. The calcined product is then removed after natural cooling.

[0007] S2: Acid leaching to remove metal impurities: The silicon roasted activated fly ash prepared in step S1 is treated with hydrochloric acid to remove impurities, filtered, and the filter residue is washed with deionized water until the pH value of the filtrate is neutral. The filter residue is dried and set aside for use;

[0008] S3: Alkaline solution leaching of silicon and aluminum components: Add 3 mol / L-10 mol / L NaOH solution to the filter residue prepared in step S2 and stir to convert all silicon and aluminum components such as silicon powder, silicon dioxide and aluminum oxide in the filter residue into SiO3 2- and AlO2 - The reaction solution was filtered out and the filtrate was set aside for use;

[0009] S4: Synthesis of zeolite molecular sieve by hydrothermal method: subjecting the filtrate obtained in step S3 to a hydrothermal reaction for crystallization to obtain zeolite molecular sieve.

[0010] The present invention proposes to use waste silicon chips generated during the production of semiconductor silicon wafers or solar silicon wafers as an activator for the high-temperature roasting of fly ash. Compared to conventional alkaline reagents, silicon chips are mostly factory waste, are widely available, and are inexpensive, with a primary particle size of less than 1 micron. According to the formulas Si + SiO2 = 2SiO; 2SiO + O2 = 2SiO2; and 3Si + 2Al2O3 = 4Al + 3SiO2, silicon powder reacts with the mullite (3Al2O3·2SiO2) on the surface of the glass spheres in the fly ash at high temperatures, thereby causing the mullite to melt and facilitating the extraction of active ingredients such as silica and alumina from the glass spheres in subsequent steps. Furthermore, excess silicon powder can serve as an additional silicon source to supplement the zeolite molecular sieve structure, eliminating the need for the addition of other reagent-grade silicon sources, which will reduce the manufacturing cost of the zeolite molecular sieve.

[0011] As a preferred solution, in step S1, the solid-liquid ratio of the silicon powder to the fly ash is 1:5.

[0012] As a preferred solution, in step S1, the calcination temperature is 1050° C. and the calcination time is 2 hours.

[0013] As a preferred solution, in step S2, the concentration of the hydrochloric acid is 20%.

[0014] As a preferred solution, the solid-to-liquid ratio of the silicon roasted activated fly ash to the hydrochloric acid is 1:3.

[0015] As a preferred solution, in step S2, the impurity removal condition is: acid washing with stirring at a constant temperature of 90° C. for 1 hour.

[0016] As a preferred solution, the concentration of the NaOH solution is 5 mol / L.

[0017] As a preferred solution, the solid-liquid ratio of the filter residue to the NaOH is 1:8, and the stirring condition is stirring at a constant temperature for 2 hours.

[0018] As a preferred solution, in step S4, the temperature of the hydrothermal reaction is 100-140° C., and the time is 4-16 hours.

[0019] Another technical problem to be solved by the present invention is to provide a zeolite molecular sieve using fly ash and waste silicon powder as raw materials to solve the problem of high production cost of conventional zeolite molecular sieves.

[0020] In order to solve the above problems, the present invention provides a zeolite molecular sieve based on fly ash and waste silicon powder, and the zeolite molecular sieve is prepared by the above preparation method.

[0021] The beneficial effects of the preparation method of zeolite molecular sieve based on fly ash and waste silicon powder of the present invention are mainly as follows: 1) compared with conventional alkali roasting to activate fly ash, silicon roasting to activate fly ash has mild conditions, is environmentally friendly and pollution-free, avoids corrosion to high-temperature roasting equipment, and is conducive to industrial promotion; 2) after using waste silicon to roast and activate fly ash, there is no need to additionally supplement reagent silicon sources in subsequent steps, and waste silicon powder can be utilized as a resource, which is conducive to reducing the manufacturing cost of zeolite molecular sieve. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the structure of zeolite molecular sieve. DETAILED DESCRIPTION

[0023] The technical solution of the present invention will be described clearly and completely below. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0024] The present invention provides a method for preparing a zeolite molecular sieve based on fly ash and waste silicon powder, comprising the following steps:

[0025] S1: Calcination of fly ash with silicon: Calcination of a mixture of silicon powder and fly ash in a mass ratio of (0.5-5):5 at a high temperature of 850°C-1300°C for 1-4 hours. The calcined product is then removed after natural cooling.

[0026] S2: Acid leaching to remove metal impurities: The silicon roasted activated fly ash prepared in step S1 is treated with hydrochloric acid to remove impurities, filtered, and the filter residue is washed with deionized water until the pH value of the filtrate is neutral. The filter residue is dried and set aside for use;

[0027] S3: Alkaline solution leaching of silicon and aluminum components: Add 3mol / L-10mol / L NaOH solution to the filter residue prepared in step S2 and stir to convert all the silicon powder, silicon dioxide and aluminum oxide in the filter residue into SiO3 2- and AlO2 - The reaction solution was filtered out and the filtrate was set aside for use;

[0028] S4: Synthesis of zeolite molecular sieve by hydrothermal method: subjecting the filtrate obtained in step S3 to a hydrothermal reaction for crystallization to obtain zeolite molecular sieve.

[0029] Preferably, in step S1, the mass ratio of the silicon powder to fly ash is 1:5.

[0030] Preferably, in step S1, the calcination temperature is 1050° C. and the calcination time is 2 hours.

[0031] Preferably, in step S2, the concentration of the hydrochloric acid is 20%.

[0032] Preferably, the solid-liquid ratio of the silicon roasted activated fly ash to the hydrochloric acid is 1:3.

[0033] Preferably, in step S2, the impurity removal condition is: acid washing with stirring at a constant temperature of 90° C. for 1 hour.

[0034] Preferably, the concentration of the NaOH solution is 5 mol / L.

[0035] Preferably, the solid-liquid ratio of the filter residue to the NaOH solution is 1:8, and the stirring condition is constant temperature stirring for 2 hours.

[0036] Preferably, in step S4, the temperature of the hydrothermal reaction is 100-140° C., and the time is 4-16 hours.

[0037] The present invention also provides a zeolite molecular sieve based on fly ash and waste silicon powder, and the zeolite molecular sieve is prepared by the above preparation method.

[0038] The following provides an embodiment to describe the above technical solution of the present invention:

[0039] Example 1:

[0040] S1: Silicon roasted activated fly ash

[0041] Silica powder and fly ash are mixed in a mass ratio of 1:5, and the mixture is calcined at a high temperature, preferably at a calcination temperature of 1050° C. and a calcination time of 2 h. The calcined product is taken out after natural cooling.

[0042] S2: Acid leaching to remove metal impurities

[0043] Silicon roasted activated fly ash and 20% hydrochloric acid were acid-washed at a solid-liquid ratio of 1:3 at 90°C for 1 hour to remove impurities such as iron, and then filtered. The filter residue was washed with deionized water until the pH value of the filtrate was neutral. The filter residue was dried and set aside for use.

[0044] S3: Alkali solution leaching of silicon and aluminum components

[0045] Add 5 mol / L NaOH solution to the above acid leaching residue, stir and dissolve it at 80℃ for 2 hours at a solid-liquid ratio of 1:8 to convert all the silicon powder, silicon dioxide and aluminum oxide in the residue into SiO3 2- and AlO2 - The reaction solution was filtered out and the filtrate was set aside.

[0046] S4: Hydrothermal synthesis of zeolite molecular sieves

[0047] The filtrate in the previous step is subjected to a hydrothermal reaction at a crystallization temperature of 100-140° C. and a crystallization time of 4-16 hours to obtain zeolite molecular sieve crystals.

[0048] Example 2:

[0049] S1: Silicon roasted activated fly ash

[0050] Silica powder and fly ash are mixed, preferably in a mass ratio of 0.5:5, and the mixture is calcined at a high temperature, preferably at a temperature of 850° C. and a calcination time of 4 hours. The calcined product is taken out after natural cooling.

[0051] S2: Acid leaching to remove metal impurities

[0052] Silicon roasted activated fly ash and 20% hydrochloric acid are stirred and pickled at a constant temperature of 90°C at a solid-liquid ratio of 1:3 for 1 hour to remove impurities such as iron, then filtered and the filter residue is washed with deionized water until the pH value of the filtrate is neutral. The filter residue is dried and set aside for use.

[0053] S3: Alkali solution leaching of silicon and aluminum components

[0054] Add 5 mol / L NaOH solution to the above acid leaching residue, stir and dissolve it at 80℃ for 2 hours at a solid-liquid ratio of 1:3 to convert all the silicon powder, silicon dioxide and aluminum oxide in the residue into SiO3 2- and AlO2 - The reaction solution was filtered out and the filtrate was set aside.

[0055] S4: Hydrothermal synthesis of zeolite molecular sieves

[0056] The filtrate in the previous step was subjected to a hydrothermal reaction at a crystallization temperature of 100° C. and a crystallization time of 16 h to obtain zeolite molecular sieve crystals.

[0057] Example 3:

[0058] S1: Silicon roasted activated fly ash

[0059] Silica powder and fly ash are mixed in a mass ratio of 5:5, and the mixture is calcined at a high temperature, preferably at a calcination temperature of 1300° C. and a calcination time of 1 hour. The calcined product is taken out after natural cooling.

[0060] S2: Acid leaching to remove metal impurities

[0061] Silicon roasted activated fly ash and 20% hydrochloric acid were mixed at a solid-liquid ratio of 1:3 and stirred at a constant temperature of 90°C for 1 hour to remove impurities such as iron, and then filtered and the filter residue was washed with deionized water until the pH value of the filtrate was neutral. The filter residue was dried and set aside for use.

[0062] S3: Alkali solution leaching of silicon and aluminum components

[0063] Add 5 mol / L NaOH solution to the acid leaching residue and stir at a solid-liquid ratio of 1:8 at 80 ° C for 2 hours to convert all the silicon powder, silicon dioxide and aluminum oxide in the residue into SiO3 2- and AlO2 - The reaction solution was filtered out and the filtrate was set aside.

[0064] S4: Hydrothermal synthesis of zeolite molecular sieves

[0065] The filtrate in the previous step was subjected to a hydrothermal reaction at a crystallization temperature of 140° C. and a crystallization time of 4 h to obtain zeolite molecular sieve crystals.

[0066] like Figure 1 As shown, Figure 1 This is a schematic diagram of the appearance structure of a zeolite molecular sieve based on fly ash and waste silicon powder prepared in an embodiment of the present invention. The zeolite molecular sieve based on fly ash and waste silicon powder prepared by the preparation method of the present invention has excellent shape, stable performance, low preparation cost, and high commercial value and promotion value.

[0067] Although the present disclosure is disclosed as above, the protection scope of the present disclosure is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A method for preparing zeolite molecular sieve based on fly ash and waste silicon powder, characterized in that: The following steps are involved: S1: Calcination of fly ash with silicon: Calcination of a mixture of silicon powder and fly ash at a mass ratio of (0.5-5):5 at a high temperature of 850-1300°C for 1-4 hours. The calcined product is then removed after natural cooling. S2: Acid leaching to remove metal impurities: The silicon roasted activated fly ash prepared in step S1 is treated with hydrochloric acid to remove impurities, filtered, and the filter residue is washed with deionized water until the pH value of the filtrate is neutral. The filter residue is dried and set aside for use; S3: Alkaline solution leaching of silicon and aluminum components: Add 3mol / L-10mol / L NaOH solution to the filter residue prepared in step S2 and stir to convert all the silicon powder, silicon dioxide and aluminum oxide in the filter residue into SiO3 2- and AlO2 - The reaction solution was filtered out and the filtrate was set aside for use; S4: Synthesizing zeolite molecular sieve by hydrothermal method: subjecting the filtrate obtained in step S3 to hydrothermal reaction for crystallization to obtain zeolite molecular sieve; In step S4, the temperature of the hydrothermal reaction is 100-140° C., and the time is 4-16 hours.

2. The method for preparing zeolite molecular sieve based on fly ash and waste silicon powder according to claim 1, characterized in that: In step S1, the mass ratio of the silicon powder to the fly ash is 1:

5.

3. The method for preparing zeolite molecular sieve based on fly ash and waste silicon powder according to claim 1, characterized in that: In the step S1, the calcination temperature is 1050° C. and the calcination time is 2 hours.

4. The method for preparing zeolite molecular sieve based on fly ash and waste silicon powder according to claim 1, characterized in that: In step S2, the concentration of the hydrochloric acid is 20%.

5. The method for preparing zeolite molecular sieve based on fly ash and waste silicon powder according to claim 4, characterized in that: The solid-liquid ratio of the silicon roasted activated fly ash to the hydrochloric acid is 1:

3.

6. The method for preparing zeolite molecular sieve based on fly ash and waste silicon powder according to claim 1, characterized in that: In step S2, the impurity removal condition is: acid washing with stirring at a constant temperature of 90° C. for 1 hour.

7. The method for preparing zeolite molecular sieve based on fly ash and waste silicon powder according to claim 1, characterized in that: The concentration of the NaOH solution is 5 mol / L.

8. The method for preparing zeolite molecular sieve based on fly ash and waste silicon powder according to claim 1, characterized in that: The solid-liquid ratio of the filter residue to the NaOH solution is 1:8, and the stirring condition is stirring at a constant temperature for 2 hours.

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