Preparation example of zeolite molecular sieve from fly ash

② Preparation example

Preparation of aA molecular sieve

Hydrothermal synthesis method, sodium silicate and sodium aluminate , sodium hydroxide in a certain mole ratio, under the reaction was stirred at about 80 ℃ 30min, the resulting gel was heated to 90 deg.
] C thermostat IH, continue to heat up to (102 ±2)℃, crystallize for 4～6h
.

Filter and wash with a pH value of 9, and dry at 100-200°C to obtain a crystal powder, namely 4A molecular sieve powder, which is then kneaded with the powder mixture, dried, and fired to activate the 4A molecular sieve molded product

If the above powder is cation exchanged with 0.
2mol/L KCl solution at 60-70°C (exchange degree 70%), then filtered, washed, dried, molded, and fired to activate 3A molecular sieve
.

If the above powder is cation exchanged with 0.
5-1mol/L CaCl ₂ solution at 50-80°C (exchange degree 70%), then filtered, washed, dried, molded, and fired to activate a 5A molecular sieve
.

b.
Bentonite deep processing to make P-type zeolite

I.
Preparation of P-type zeolite by sodium hydroxide solution activated bentonite method

Take 40 g of bentonite, which has been purified by the wet method and crushed into fine powder, mixed with 48 g of sodium hydroxide, and then added to the autoclave, while adding 700 mL of water
.

The XRD spectrum analysis of the solid phase composition of the bentonite activation reaction at 150℃ for 3h shows that the activation reaction product is mainly hydrated aluminosilicate (Na ₆ Al ₆ Si ₁₀ O ₃₂ ·12H ₂ O), in addition to a small amount of Na (AISi ₂ O ₆ )H ₂ O and Na ₂ SiO ₃

Take out the reaction liquid from the autoclave and put it into an Erlenmeyer flask, and then use aluminum hydroxide, sodium hydroxide and water to adjust the molar ratio of Al ₂ O ₃ : SiO ₂ : Na ₂ O: H ₂ O in the system.
1:2.
3:3:190
.

The mixed system was aged for 8 hours at 90°C, and then a small amount of 4A zeolite seed crystals (0.

II.
Preparation of P-type zeolite by sodium hydroxide alkali fusion activated bentonite method

After the wet-purified ore powder is pulverized into a fine powder by a universal pulverizer, 18 g is taken out and uniformly mixed with 21.
6 g of sodium hydroxide, and the mixture is placed in a muffle furnace for alkali fusion activation reaction
.

Although the melting point of sodium hydroxide is 318°C, due to the addition of bentonite, the reaction system only becomes liquid at nearly 400°C during the experiment.

The alkali fusion activated raw materials are crushed and put into an Erlenmeyer flask, and the molar ratio of Al ₂ O ₃ :SiO ₂ :Na ₂ O:H ₂ O in the system is adjusted with aluminum hydroxide, sodium hydroxide and water respectively to 1: 2.
1:3.
0:190
.

The adjusted system is first stirred and aged at 80℃ for 6h, and then a small amount of 4A zeolite seed crystal (0.

c.
Microwave preparation and modification of β zeolite

I.
Synthesis of Beta Zeolite Powder

Gel Preparation: coarse pore silica as silica source, the aluminum source is sodium aluminate, tetraethyl ammonium hydroxide as templating agent, molar composition of Al 1.
0 ₂ O _.
3 · nSiO ₂ · 2.
14Na ₂ O · 100H ₂ O ·NTEAOH (Tetraethylammonium Hydroxide), respectively use the amount of template agent n(TEAOH)/n(SiO ₂ )=0.
05～0.
12 and pH=7～11 to mix the crystallization mother liquor, then add silica gel and stir well for 2～4h
.

Synthesis by microwave radiation method: transfer the colloid into a microwave reactor, place the reactor in a microwave oven to receive microwave radiation, microwave power 200W, crystallization temperature 80～180℃, crystallization time 1～5h, until crystallization is completed, cooling and washing When the pH value is 7, the raw Naβ zeolite powder is obtained by suction filtration and drying at 110°C
.

II.
Preparation of Hβ Zeolite

Microwave radiation demoulding method: microwave power 700W, heating rate 10℃/min, final temperature 180℃, constant temperature 0.
5h, radiation demoulding
.

Transformation of β zeolite: After demolding, β zeolite is used 0.
2mol/L NH ₄ Cl aqueous solution (liquid-solid ratio 30mL/g), refluxed at a constant temperature of 80°C for 3h, washed with deionized water until the pH of the solution is 7,110 Drying at ℃, roasting at 550℃ for 4h, Hβ zeolite is obtained, and then the Hβ zeolite catalyst is obtained by tableting and sieving (particle size 0.
28～0.
45mm)
.

I.
Ag modification

Dissolve AgNO ₃ in water, and then gradually drop its co-solution into the weighed Hβ zeolite, dry at room temperature for 6 hours, gradually increase from room temperature to 550 ℃ during roasting, and then reduce the temperature after 2 hours of constant temperature, then press tablets and sieving ( Particle size 0.
28～0.
45mm), that is, Ag/β zeolite (Ag mass fraction is 1.
8%)
.

d.
Preparation of pure zeolite molecular sieve by stepwise dissolution of silica and aluminum from fly ash

I.
Fly ash roasting pretreatment process

The fly ash and 200 mesh sodium carbonate are thoroughly mixed at a mass ratio of 1:1.
5, placed in a corundum crucible, and heated to 830°C in a muffle furnace for 1 hour
.

The calcined product is light yellow powder

II.
Synthesis of Zeolite Molecular Sieve

The pre-calcined fly ash roasted product is leached with deionized water at a liquid-solid ratio of 5:1, heated and stirred to fully dissolve the soluble silicate, and filtered
.

The filter residue is leached with different concentrations of NaOH solution, heated to boiling under stirring, the aluminosilicate in the roasted product is decomposed into silicate and aluminate under the action of OH- , and filtered

e.
Preparation of 4A zeolite molecular sieve from attapulgite clay

I.
Raw material handling

The original attapulgite soil was calcined at 650°C for 30 minutes to destroy its crystal structure and free the silicon dioxide in it to become amorphous SiO2
.

Add 3% ammonium chloride as a roasting aid during roasting to remove iron interference

II.
Preparation method

Add a certain amount of calcined earth and measured 30% sodium hydroxide solution to a three-necked flask for alkali dissolution, and react in a constant temperature water bath under magnetic stirring.
The alkali dissolving temperature is above 90℃ and the alkali dissolving time is 4 hours to obtain a gel mixture.

.
Then in the gel mixture, adjust the addition of sodium metaaluminate and water according to a certain ratio, and continuously stir to carry out the crystallization reaction
.
The crystallization reaction temperature is 90°C, and the crystallization time is 2-6h
.
After the reaction, filter and wash until the pH of the filtrate is less than or equal to 11.
The filter cake is placed in an oven at 120° C.
and dried for 12 hours to obtain a 4A zeolite molecular sieve product
.

[Technical index] Domestic reference standard for natural zeolite