CN103588212A - Method for synthesizing delta-layered sodium disilicate by silicon tetrachloride - Google Patents

Abstract

A method for synthesizing delta-layered sodium disilicate by silicon tetrachloride comprises the following steps: hydrolyzing silicon tetrachloride, carrying out pumping filtration and separation to respectively obtain a hydrochloric acid filtrate and an orthosilicic acid filter residue; mixing orthosilicic acid and sodium hydroxide and calcining to obtain solid sodium silicate; dissolving solid sodium silicate in hot water and filtering to obtain a liquid sodium silicate filtrate; carrying out spray drying on liquid sodium silicate at 150-250 DEG C to obtain amorphous powdery sodium disilicate; and uniformly mixing powdery sodium disilicate and 5-20% of delta-layered sodium disilicate seed crystal with the particle size being 0.04-0.1mm, and carrying out high-temperature roasting and crystallization in a muffle furnace of 650-750 DEG C for 10-60min so as to finally prepare delta-layered sodium disilicate. According to the method, the industrial waste silicon tetrachloride is used as a raw material such that safe treatment of a photovoltaic by-product is guaranteed and valuable delta-layered sodium disilicate and hydrochloric acid are also synthesized. The method is a green chemical reaction pathway. The method requires a simple production technology. Purity of the synthesized product delta-phase crystal can reach 95%, degree of crystallization can reach 90%, and the product has good calcium and magnesium ion exchange capacity and buffer capacity.

Description

The method of the synthetic high-purity δ-layered sodium disilicate of a kind of silicon tetrachloride

Technical field

The invention belongs to photovoltaic industry silicon tetrachloride as by-product recycling treatment disposal technology field, be specifically related to the method for the synthetic high-purity δ-layered sodium disilicate of a kind of silicon tetrachloride.

Background technology

Polysilicon is as the direct material of producing photovoltaic cell, and along with the fast development of photovoltaic exhibition industry over nearly 10 years, output continues surging, and within 2011, domestic polysilicon output has reached 7.5 ten thousand tons.Yet 1 ton of polysilicon of every production is by the silicon tetrachloride by product that produces 18 tons, and silicon tetrachloride boiling point only has 70 ℃, in air, very easily hydrolysis generates hydrochloric acid mist, there is extremely strong corrodibility and toxicity, be incorporated into < < hazardous chemical register (2012) > > the 8th class the 1st group.According to the regulation in Hazardous Waste List (2008) the > > of < < country, hazardous chemical class under silicon tetrachloride belongs to Hazardous wastes, need to dispose according to the management rules safe handling of Hazardous wastes.The resource technology of silicon tetrachloride mainly comprises at present: (1) silicon tetrachloride hydrogenating reduction is produced trichlorosilane, comes back in polycrystalline silicon production line, at technique internal recycle, uses; (2) take silicon tetrachloride prepares other Chemicals as raw material, as white carbon black, organosilicon product and optical fiber level silicon tetrachloride etc.

The molecular formula of layered sodium disilicate is Na ₂onSiO ₂(n=2.0), wherein silicate forms three-dimensional netted skeleton structure, Na by sharing Sauerstoffatom ⁺in the middle of silicate layer, be combined with summit oxygen, form stable chemical structure.Layered sodium disilicate comprises α, β and tri-kinds of crystalline phases of δ, wherein δ-layered sodium disilicate have stronger calcium and magnesium ion exchange capacity and pH surge capability, therefore can substitute tripoly phosphate sodium STPP and 4A zeolite, be a kind of non-phosphorus washing assistant of high-efficiency environment friendly; But the expensive problem of δ-layered sodium disilicate has restricted its large-scale application.

The synthetic method of layered sodium disilicate all be take water glass as raw material at present, is divided into two kinds of dry method and wet methods.Wet method is to take sodium silicate aqueous solution as presoma, synthetic 600～800 ℃ of calcinings, according to the difference of temperature and time, can synthesize α, β and tri-kinds of different crystalline phases of δ; Dry method is to take solid water glass particle as presoma, synthetic 650～750 ℃ of calcinings, mainly take the mixture of α and δ crystalline phase as main.Research shows, in order to improve the ratio of wet method δ crystalline phase product, can presoma spraying is dry after calcined crystalline or add a certain proportion of crystal seed in crystallisation process again.

Although silicon tetrachloride refuse has larger harm, purity reaches more than 99%, take that it prepares the interference that δ-layered sodium disilicate can be good at avoiding impurity as raw material; Meanwhile, in the process of preparation, can also reclaim hydrochloric acid, without other by products, generate, be a kind of green chemical reaction process.The method at home and abroad have not been reported at present.

Summary of the invention

In order to overcome the defect of prior art, the object of the present invention is to provide the method for the synthetic high-purity δ-layered sodium disilicate of a kind of silicon tetrachloride, take silicon tetrachloride as raw material, synthetic δ-layered sodium disilicate also reclaims the method for hydrochloric acid, object is to dispose for the safe handling of silicon tetrachloride Hazardous wastes the resource utilization approach that provides, and the non-phosphorus washing assistant of preparation has higher added value simultaneously.

For achieving the above object, technical scheme of the present invention is:

A method for the synthetic high-purity δ-layered sodium disilicate of silicon tetrachloride, comprises the following steps:

(A) hydrolyzing silicon tetrachloride: silicon tetrachloride is at the uniform velocity dropped to and is equipped with in pure water Erlenmeyer flask with automatic sampler, and control rate of addition is 1～2ml/min, prevents hydrochloric acid volatilization; The mol ratio of silicon tetrachloride and water is 1:8～1:40, and the reaction times is 5～10min; Silicon tetrachloride and water react and generate orthosilicic acid precipitation and hydrochloric acid, reaction equation (1):

SiCl ₄+4H ₂O→Si(OH) ₄+4HCl （1）

(B) product separation, reclaims hydrochloric acid: the product in step (A) is separated with suction filtration device, and filter residue is required product orthosilicic acid, and filtrate is hydrochloric acid, after concentrating, as salt acid product, reclaims;

(C) prepare sodium silicate solid: the orthosilicic acid in step (B) is transferred in 50ml nickel crucible, adds sodium hydrate solid, make modulus n=1.9～2.1; Mix and nickel crucible is put into after reactant to the retort furnace of 800～900 ℃ and calcined 1～2h; After taking-up nickel crucible is cooling, obtain sodium silicate solid; Orthosilicic acid and sodium hydroxide react and generate water glass, reaction equation (2) under molten state:

2Si(OH) ₄+2NaOH→Na ₂Si ₂O ₅+5H ₂O （2）

(D) dissolution filter: the sodium silicate solid in step (C) is dissolved in 50～80 ℃ of hot water, and product is separated with suction filtration device; Filter residue is unreacted silicon-dioxide and turns back in step (C) and sodium hydroxide secondary response again, and filtrate is liquid sodium silicate and transfers in beaker; The solid content of controlling liquid sodium silicate in this step is 40～50%;

(E) spraying is dry: the liquid sodium silicate in step (D) is dried 150～250 ℃ of sprayings, obtains the powdery sodium disilicate of amorphous state;

(F) prepare δ-layered sodium disilicate: the product in step (E) is transferred in 50ml nickel crucible, and adding particle diameter is δ-layered sodium disilicate crystal seed of 0.04～0.1mm, the add-on of crystal seed is 5%～20% of product quality in step (E); After mixing reactant, nickel crucible is placed in to 650～750 ℃ of retort furnace high-temperature roasting crystallization 10～60min, powdery sodium disilicate finally makes δ-layered sodium disilicate through recrystallization.

The invention has the advantages that:

1. take industrial waste silicon tetrachloride as raw material, both guaranteed that the safe handling of photovoltaic by product was disposed, synthesized again δ-layered sodium disilicate and the hydrochloric acid with higher utility value, reaction whole process no coupling product produces, and is a kind of green chemical reaction approach.

2. the method production technique is simple, at high temperature synthesizes δ-layered sodium disilicate, the purity to 95% of δ phase crystal, and degree of crystallinity can reach 90%.

3. this product has good calcium and magnesium ion exchange capacity and surge capability, to the exchange capacity of calcium ion, can reach 300mg CaCO ₃more than/g, to the exchange capacity of magnesium ion, can reach 400mgMgCO ₃more than/g.

Accompanying drawing explanation

Fig. 1 is process flow sheet of the present invention.

Fig. 2 is comparative example 1 and embodiment 1 sample XRD figure spectrum; (a) for not adding crystal seed collection of illustrative plates; (b) add 20% crystal seed collection of illustrative plates.

Fig. 3 is the impact of Tc on δ-layered sodium disilicate degree of crystallinity and δ phase crystal purity, sample in corresponding embodiment 1 and embodiment 3～6.

Fig. 4 is the impact of Tc on δ-layered sodium disilicate calcium and magnesium ion exchange capacity, sample in corresponding embodiment 1 and embodiment 3～6.

Embodiment

Technical process of the present invention as shown in Figure 1, is carried out more detailed description below in conjunction with concrete case study on implementation to the present invention, but is not limited to the examples.

Embodiment mono-

(A) get 31.4ml pure water and be placed in 150ml Erlenmeyer flask, with automatic sampler, 10ml silicon tetrachloride is evenly added drop-wise in pure water, rate of addition is 1.5ml/min, and the mol ratio of silicon tetrachloride and water is excessive 4 times of 1:20(water);

(B) with suction filtration device by step (A) product separation, after filtrate is concentrated, as HCl recovery, filter residue (orthosilicic acid) is transferred in 50ml nickel crucible;

(C) take 3.48gNaOH solid, join in 50ml nickel crucible, make SiO ₂/ Na ₂o modulus is 1.9～2.1; Mix and nickel crucible is put into after reactant to the retort furnace of 850 ℃ and calcined 1h, take out nickel crucible and obtain sodium silicate solid after cooling;

(D) get 15ml pure water and join in 50ml beaker, be heated to 80 ℃, step (C) sodium silicate solid is transferred in beaker and dissolved; With suction filtration device, by product separation, filter residue (unreacted silicon-dioxide) turns back in step (C) and sodium hydroxide secondary response again, and filtrate (being liquid sodium silicate) is transferred in beaker; The solid content of controlling liquid sodium silicate in this step is 40%;

(E) liquid silicic acid sodium solution is squeezed in spray-drying tower, under 200 ℃ of hot blast direct heating, obtained the powdery sodium disilicate of amorphous state;

(F) powdery sodium disilicate is transferred in 50ml nickel crucible, adding particle diameter is δ-layered sodium disilicate crystal seed of 0.04～0.1mm, add-on is 20% of the middle product quality of step (E), after mixing reactant, nickel crucible is put into 700 ℃ of retort furnaces, high-temperature roasting crystallization 30min, obtains δ-layered sodium disilicate product after taking-up nickel crucible is cooling.

Embodiment 2

(A) get 12.56ml pure water and be placed in 150ml Erlenmeyer flask, with automatic sampler, 10ml silicon tetrachloride is evenly added drop-wise in pure water, rate of addition is 1ml/min, and the mol ratio of silicon tetrachloride and water is excessive 1 times of 1:8(water);

(B) with suction filtration device by step (A) product separation, after filtrate is concentrated, as HCl recovery, filter residue (orthosilicic acid) is transferred in 50ml nickel crucible;

(C) take about 3.48gNaOH solid, join in 50ml nickel crucible, make SiO ₂/ Na ₂o modulus is 1.9～2.1; Mix and nickel crucible is put into after reactant to the retort furnace of 800 ℃ and calcined 2h, take out nickel crucible and obtain sodium silicate solid after cooling;

(D) get 15ml pure water and join in 50ml beaker, be heated to 70 ℃, step (C) sodium silicate solid is transferred in beaker and dissolved; With suction filtration device, by product separation, filter residue (unreacted silicon-dioxide) turns back in step (C) and sodium hydroxide secondary response again, and filtrate (being liquid sodium silicate) is transferred in beaker; The solid content of controlling liquid sodium silicate in this step is 50%;

(E) liquid silicic acid sodium solution is squeezed in spray-drying tower, under 250 ℃ of hot blast direct heating, obtained the powdery sodium disilicate of amorphous state;

(F) powdery sodium disilicate is transferred in 50ml nickel crucible, adding particle diameter is δ-layered sodium disilicate crystal seed of 0.04～0.1mm, add-on is 10% of the middle product quality of step (E), after mixing reactant, nickel crucible is put into 750 ℃ of retort furnaces, high-temperature roasting crystallization 20min, obtains δ-layered sodium disilicate product after taking-up nickel crucible is cooling.

Embodiment 3

Described step is identical with embodiment 1, and difference is that in step (F), high-temperature roasting temperature is 650 ℃.

Embodiment 4

Described step is identical with embodiment 1, and difference is that in step (F), high-temperature roasting temperature is 685 ℃.

Embodiment 5

Described step is identical with embodiment 1, and difference is that in step (F), high-temperature roasting temperature is 725 ℃.

Embodiment 6

Described step is identical with embodiment 1, and difference is that in step (F), high-temperature roasting temperature is 750 ℃.

Comparative example 1:

Described step is identical with embodiment 1, difference is, in step (F), powdery sodium disilicate to be transferred in 50ml nickel crucible, does not add crystal seed, nickel crucible is directly put into 700 ℃ of retort furnace high-temperature roasting crystallization 30min, after taking-up nickel crucible is cooling, obtain δ-layered sodium disilicate product.

Embodiment mono-product is analyzed and is contrasted:

Adopt X ray high resolving power diffractometer (Siemens, D8Advance type) to measure the crystal structure characteristic of δ-layered sodium disilicate product particle.Instrument source of radiation is selected Cu-K α (λ=0.15406nm), 2 10 ° of θ angular regions～50 °, and step-length is 0.02 °.

(1) by not adding in comparative example 1, in the synthetic product of crystal seed and embodiment 1, do not add synthetic sample under 20% crystal seed, 700 ℃ of conditions and get respectively 1g, with agate mortar, grain diameter is ground to below 5 μ m, with its crystalline structure of X-ray diffractometer tester, the XRD figure obtaining is composed as shown in Figure 2.From figure, can find α-Na while not adding crystal seed ₂si ₂o ₃(27 °), β-Na ₂si ₂o ₃(30 ° and 37 °) and δ-Na ₂si ₂o ₃(22.4 ° and 37 °) have all shown stronger absorption peak; And add after 20% δ phase crystal seed α-Na ₂si ₂o ₃and β-Na ₂si ₂o ₃absorption peak obviously a little less than; Show after δ phase crystal seed adds to make the crystallization of layered sodium disilicate become selective the purity of the δ phase crystal greatly having improved.

(2) by adding 20% crystal seed, Tc to be respectively synthetic sample under 700 ℃, 650,685 ℃, 725 ℃ and 750 ℃ of conditions in embodiment 1, embodiment 3～6, get respectively 1g, with agate mortar, grain diameter is ground to below 5 μ m, with its crystalline structure of X-ray diffractometer tester, purity and the degree of crystallinity of δ phase crystal in analytic sample, experimental result as shown in Figure 3.Degree of crystallinity refers to α-Na ₂si ₂o ₃(27 °) and δ-Na ₂si ₂o ₃the ratio of (22.4 °) response intensity sum and standard model response intensity.

Embodiment bis-products are analyzed and are contrasted:

(1) EDTA volumetric determination calcium exchange capacity method:

With pipette, extract 50ml calcium chloride solution (0.05mol/L) in 500ml volumetric flask, be diluted with water to scale, mix, all be transferred in dry 1000ml beaker, add several sodium hydroxide solutions (0.5mol/L) regulator solution pH to 10.5(records with pH meter under whipped state), be heated to (35 ± 1) ℃;

Add 0.5g δ-layered sodium disilicate sample (105 ℃ dry 2h), immediately beaker is placed in to the water bath with thermostatic control of (35 ± 1) ℃, under 500r/min rotating speed, stir 20min;

With dry qualitative filter paper at a slow speed, filter, initial 5ml filtrate is discarded, filtrate reaches after certain volume, with transfer pipet, pipette 50.0ml in 250ml Erlenmeyer flask immediately, add 2ml sodium hydroxide solution (2.5mol/L) and 0.06g calconcarboxylic acid, with EDTA standard titration solution (0.01mol/L) titration, from burgundy, becoming blueness is terminal.

Calcium ion exchange capacity is with X _caCO3power represents, unit is mgCaCO ₃/ g, calculates by formula (3):

$X_{{\mathrm{CaCO}}_3}=\frac{1000.8\&times;(5\&times;C_{{\mathrm{CaCl}}_2}-V_{\mathrm{EDTA}}\&times;C_{\mathrm{EDTA}})}{m}---\left(3\right)$

In formula: C _caCl2the concentration that represents calcium chloride, mol/L; V _eDTAthe volume that represents the EDTA standardized solution that titration consumes, ml; C _eDTAthe concentration that represents EDTA standardized solution, mol/L; M represents the quality of sample, g.

(2) EDTA volumetric determination magnesium exchange capacity method:

With pipette, extract 50ml magnesium chloride solution (0.05mol/L) in 500ml volumetric flask, be diluted with water to scale, mix, all be transferred in dry 1000ml beaker, add several sodium hydroxide solutions (0.5mol/L) regulator solution pH to 10.5(records with pH meter under whipped state), be heated to (35 ± 1) ℃;

Add 0.5g δ-layered sodium disilicate sample (105 ℃ dry 2h), immediately beaker is placed in to the water bath with thermostatic control of (35 ± 1) ℃, under 500r/min rotating speed, stir 20min;

With dry qualitative filter paper at a slow speed, filter, initial 5ml filtrate is discarded, filtrate reaches after certain volume, with transfer pipet, pipette 50.0ml in 250ml Erlenmeyer flask immediately, add 15ml ammonia-chloride buffer solution (pH=10) and 0.03g acid chromium blue k indicator, with EDTA standard titration solution (0.01mol/L) titration, from red-purple, becoming blueness is terminal.

Magnesium ion exchange capacity is with X _mgCO3power represents, unit is mgMgCO ₃/ g, calculates by formula (4):

$X_{{\mathrm{MgCO}}_3}=\frac{843.2\&times;(5\&times;C_{{\mathrm{MgCl}}_2}-V_{\mathrm{EDTA}}\&times;C_{\mathrm{EDTA}})}{m}---\left(4\right)$

In formula: C _mgCl2the concentration that represents magnesium chloride, mol/L; V _eDTAthe volume that represents the EDTA standardized solution that titration consumes, ml; C _eDTAthe concentration that represents EDTA standardized solution, mol/L; M represents the quality of sample, g.

(3) embodiment sample determination:

As above described in method, Tc in embodiment 1, embodiment 3～6 is respectively to synthetic sample under 700 ℃, 650,685 ℃, 725 ℃ and 750 ℃ of conditions and measures, the calcium ions and magnesium ions exchange capacity obtaining as shown in Figure 4.

Claims (1)

1. a method for the synthetic high-purity δ-layered sodium disilicate of silicon tetrachloride, is characterized in that, comprises the following steps:

(A) hydrolyzing silicon tetrachloride: silicon tetrachloride is at the uniform velocity dropped to and is equipped with in pure water Erlenmeyer flask with automatic sampler, and control rate of addition is 1～2ml/min, prevents hydrochloric acid volatilization; The mol ratio of silicon tetrachloride and water is 1:8～1:40, and the reaction times is 5～10min; Silicon tetrachloride and water react and generate orthosilicic acid precipitation and hydrochloric acid, reaction equation (1):

SiCl ₄+4H ₂O→Si(OH) ₄+4HCl （1）

(B) product separation, reclaims hydrochloric acid: the product in step (A) is separated with suction filtration device, and filter residue is required product orthosilicic acid, and filtrate is hydrochloric acid, after concentrating, as salt acid product, reclaims;

(C) prepare sodium silicate solid: the orthosilicic acid in step (B) is transferred in 50ml nickel crucible, adds sodium hydrate solid, make modulus n=1.9～2.1; Mix and nickel crucible is put into after reactant to the retort furnace of 800～900 ℃ and calcined 1～2h; After taking-up nickel crucible is cooling, obtain sodium silicate solid; Orthosilicic acid and sodium hydroxide react and generate water glass, reaction equation (2) under molten state:

2Si(OH) ₄+2NaOH→Na ₂Si ₂O ₅+5H ₂O （2）

(D) dissolution filter: the sodium silicate solid in step (C) is dissolved in 50～80 ℃ of hot water, and product is separated with suction filtration device; Filter residue is unreacted silicon-dioxide and turns back in step (C) and sodium hydroxide secondary response again, and filtrate is liquid sodium silicate and transfers in beaker; The solid content of controlling liquid sodium silicate in this step is 40～50%;

(E) spraying is dry: the liquid sodium silicate in step (D) is dried 150～250 ℃ of sprayings, obtains the powdery sodium disilicate of amorphous state;

(F) prepare δ-layered sodium disilicate: the product in step (E) is transferred in 50ml nickel crucible, and adding particle diameter is δ-layered sodium disilicate crystal seed of 0.04～0.1mm, the add-on of crystal seed is 5%～20% of product quality in step (E); After mixing reactant, nickel crucible is placed in to 650～750 ℃ of retort furnace high-temperature roasting crystallization 10～60min, powdery sodium disilicate finally makes δ-layered sodium disilicate through recrystallization.

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