CN103466637A - Method for producing precipitate silicon dioxide by using sodium bicarbonate to control supersaturation degree - Google Patents

Abstract

A method for producing precipitated silica by using sodium bicarbonate to control supersaturation, using quartz sand and soda ash as raw materials, firstly preparing sodium silicate solution by calcining and dissolving sodium carbonate solution, and then mixing sodium silicate solution with sodium bicarbonate Solution reaction, by controlling the supersaturation of reaction crystallization, hydrated silica precipitate is precipitated, and the precipitate obtained by filtration is washed, dried and other steps to finally obtain the precipitated silica product, namely white carbon black. The filtered filtrate is sodium carbonate solution, which is divided into three parts for recycling: one part absorbs carbon dioxide from the calcination section to prepare concentrated sodium bicarbonate solution required for crystallization reaction; one part is used to dissolve solid sodium silicate; the last part is evaporated and concentrated Then return to the quartz sand calcination section. The precipitated silica product obtained by the invention has high purity and uniform particle size distribution, and the materials in the whole production process are recycled, which overcomes the problem of sodium sulfate sewage discharge in conventional production.

Description

A kind of method utilizing sodium bicarbonate to control supersaturation to produce precipitated silica

technical field

The invention belongs to the field of precipitated silica production, and in particular relates to a method for preparing precipitated silica by crystallization through the reaction of sodium silicate solution and sodium bicarbonate solution to control supersaturation through the sodium bicarbonate solution.

Background technique

Precipitated silica is commonly known as white carbon black, also known as hydrated silica, and its molecular formula is SiO ₂ ·nH ₂ O. It is a white, non-toxic, amorphous ultrafine powder with porosity, high Lightweight, good chemical stability, high temperature resistance, non-combustible and good electrical insulation and other excellent properties. Silica is an important inorganic chemical raw material, which is widely used in the fields of rubber, plastics, coatings, papermaking, medicine, pesticides and daily chemicals. At present, 70% of the world's silica is used in the rubber industry, and it is a rubber reinforcing agent with excellent performance.

There are two methods of producing white carbon black: dry method and wet method. The dry method includes the gas phase method and the arc method, and the wet method includes the precipitation method and the gel method, among which the gas phase method and the precipitation method occupy a dominant position in the production of white carbon black at home and abroad. The gas phase method mostly uses SiCl ₄ as raw material, and the obtained product has high purity, good dispersion, fine and spherical particles, and has excellent reinforcing properties. However, due to expensive raw materials, high energy consumption and complex technology in the production process, the application of gas phase method in industry is limited. The traditional precipitation method uses water glass as raw material to prepare white carbon black through acidification with inorganic acid, and acidification with sulfuric acid is often used in industry. Compared with the gas-phase method, the raw materials of the precipitation method are easy to obtain, the energy consumption of the production process is low, and the process is simple, but the quality of the obtained product is low, and a large amount of sodium sulfate sewage is generated during the production process.

At present, some researchers have improved the traditional precipitation technology. For example, the literature Quang, D.V.; Kim, J.-K.; Park, J.-K.; Park, S.-H.; Elineema, G.; Sarawade, P.B.; Kim, H.T., Effect of the gelation on the properties of precipitated silica powder produced by acidizing sodium silicate solution at the pilot scale. Chemical Engineering Journal 2012, 209, 531-536. Reported a production method of white carbon black. The method uses water glass and sulfuric acid as raw materials, and on the basis of traditional techniques, controls the gelation process by adding acid in two steps, and then uses spray drying technology to dry silicon dioxide hydrate to obtain a white carbon black product. The white carbon black obtained by this method has uniform particle size distribution, high specific surface area and pore volume, but it does not solve the problem of sodium sulfate sewage, which not only causes waste of water resources and available sodium sulfate resources, but also produces serious environmental pollution. pollute.

Patent CN201110026112.0 discloses a process for preparing precipitation white carbon black by carbon dioxide decomposition. In this method, carbon dioxide is used as a precipitating agent, which is passed into an industrial sodium silicate solution to obtain precipitated white carbon black, and the solution after precipitation can be made into a high-value-added sodium carbonate product, thereby eliminating sewage discharge. Patent CN200710062197.1 discloses a method for preparing white carbon black by secondary carbon fraction. _CO2 gas is introduced into the sodium silicate solution twice successively to adjust the pH value of the solution to realize two solid-liquid separations, and the remaining sodium carbonate The solution is made into sodium hydroxide solution after being concentrated by causticizing. Patent CN201110267981.2 uses micro-silicon powder as raw material to synthesize white carbon black through carbonization, realizing the resource utilization of industrial waste. Patent CN201110267968.7 proposes to use micro-silica powder as raw material to make water glass by sodium hydroxide hot alkali method, and then carry out carbonization reaction with carbon dioxide, and add calcium hydroxide to the sodium carbonate raffinate after carbonization and filtration to carry out causticization reaction. That is to say, the technology of preparing white carbon black and co-producing calcium carbonate has been formed. These carbonization technologies all avoid the problem that a large amount of sewage is difficult to treat, but due to the long gas-liquid reaction time, low conversion rate, and the complex mass transfer process of _CO2 gas in sodium silicate solution, it is difficult to effectively control, resulting in the obtained The particle size distribution of the precipitate is uneven and the purity is not high, which affects the industrial application of the product.

Patent CN00132275.3 and patent CN02132723.8 propose a carbonization reaction method in a supergravity reactor. The supergravity environment strengthens the gas-liquid mass transfer process, thereby improving production efficiency and shortening the production cycle. However, the above-mentioned carbon dioxide precipitation methods all use industrial grade sodium silicate as raw material, requiring the use of sodium silicate solution with higher purity, and when the impurity content of the raw material is high, qualified white carbon black products cannot be produced.

Patent CN200810048295.4 and patent CN201110078760.0 use the ammonification precipitation method to prepare white carbon black by reacting water glass with ammonium bicarbonate solution, and the gas and filtrate generated during the production process are recovered and recycled to realize efficient utilization of raw materials . However, ammonium bicarbonate solution is unstable and easily decomposes above 36°C to release CO ₂ and NH ₃ , and the precipitation process is difficult to control, resulting in low precipitation reaction efficiency and uneven product particle size distribution. On the other hand, both ammonium bicarbonate and ammonia water have pungent smell and corrosiveness, endanger human health and corrode equipment.

Contents of the invention

The purpose of the present invention is to address the deficiencies in the prior art, to provide a method for controlling supersaturation by using sodium bicarbonate solution and crystallizing to prepare precipitated silica. The obtained precipitated silica product has high purity and uniform particle size distribution, and Materials are recycled throughout the production process, and no waste liquid is generated.

The present invention uses quartz sand and soda ash as raw materials. Firstly, sodium silicate solution is prepared by calcining and dissolving, and then sodium silicate is reacted with sodium bicarbonate, and hydrated silica precipitates are precipitated by controlling the supersaturation degree of reaction crystallization, and filtered. The obtained precipitate is washed and dried to obtain a precipitated silica product. The filtered filtrate is sodium carbonate solution, which is recycled through three parts: one part absorbs carbon dioxide from the calcination section to prepare the concentrated sodium bicarbonate solution required for the crystallization reaction; one part is used to dissolve solid sodium silicate; the last part is evaporated and concentrated Return to the quartz sand calcination section.

The reaction that the present invention relates to has:

(1) SiO ₂ (s)+Na ₂ CO ₃ (s)=Na ₂ SiO ₃ (s)+CO ₂ (g)

(2) Na ₂ SiO ₃ (aq)+2NaHCO ₃ (aq)=SiO ₂ (s)+2Na ₂ CO ₃ (aq)+H ₂ O(aq)

(3) Na ₂ CO ₃ (aq)+CO ₂ (g)+H ₂ O(aq)=2NaHCO ₃ (aq)

The specific process steps are as follows:

1) Preparation of solid sodium silicate by calcining quartz sand and soda ash

Choose quartz sand with a specification of 40-70 mesh and a _SiO2 content of 98.8%, and mix the quartz sand and soda ash according to requirements, and the molar ratio is 1:(1.2-1.8). After mixing evenly, calcinate at 1300-1400°C for 30-60 minutes to obtain solid sodium silicate, and recover CO ₂ at the same time.

2) Solid sodium silicate dissolved

Solid sodium silicate was dissolved in sodium carbonate solution to obtain a sodium silicate solution with a concentration of 1.2mol/L.

3) Reaction crystallization of sodium silicate and sodium bicarbonate

Place the sodium silicate solution obtained in step 2) in a crystallization reactor, control the temperature at 40-50°C, turn on the stirrer, add a sodium bicarbonate solution with a concentration of 2.7mol/L dropwise with a peristaltic pump, and adjust the solution The rate of addition and the amount of addition are used to control the degree of supersaturation and precipitate hydrated silica. The above reaction temperature and the concentration of reactants are beneficial to the formation and precipitation of crystals, so that the produced crystals have high purity, good crystal form, high specific surface area and pore volume, and uniform particle size distribution.

4) Preparation of high-purity white carbon black

The suspension obtained in step 3) is filtered to obtain a hydrated silica precipitate and a sodium carbonate filtrate. The filtered precipitate is washed, dried and pulverized to obtain a precipitated silica product.

5) recycling of sodium carbonate solution

Step 4) the sodium carbonate filtrate that obtains is recycled in three parts: a part of sodium carbonate solution absorbs the _CO gas that step 1) obtains, controls gas flow, obtains sodium bicarbonate solution, returns to step 3) recycles; a part of sodium carbonate solution Return to step 2) for dissolving solid sodium silicate; the last part of the sodium carbonate solution is concentrated by evaporation and returns to step 1) for calcination.

Advantage and positive effect of the present invention are:

(1) The present invention uses sodium bicarbonate solution to control the supersaturation, which is convenient and controllable, and the supersaturation, as the driving force of crystallization, can directly affect the formation of crystal nuclei and the growth of crystals, and then affect the crystallization products The particle size and particle size distribution of the crystals.

(2) Material recycling in the production process greatly saves the amount of raw materials such as soda ash and water, and there is no waste water and waste gas discharge, which is friendly to the environment.

(3) The prepared precipitated silica has high purity and uniform particle size distribution, and can be sold as a high-quality product.

Description of drawings

Fig. 1 is a schematic diagram of the process flow of the present invention.

The materials in the figure represent respectively:

L1: the mixture of quartz sand and soda ash;

S2-1: the sodium silicate solid obtained by calcining;

G2-2: _CO gas released by calcination;

L3: sodium silicate solution;

L4: the suspension after the crystallization reaction;

S5: hydrated silica solid;

L6-1: _Na2CO3 solution entering _{the CO2} absorption section;

L6-2: _Na2CO3 solution entering the dissolution section _;

L6-3: _Na2CO3 solution entering the evaporation concentration section _;

L7:NaHCO ₃ solution;

L8: concentrated Na ₂ CO ₃ solution.

Fig. 2 is the SEM picture of the precipitated silica product prepared in Example 1 of the present invention;

Fig. 3 is an EDS energy spectrum diagram of the precipitated silica product prepared in Example 1 of the present invention.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. But the following embodiments are only limited to explain the present invention, and the protection scope of the present invention should include the entire content of the claims, not only limited to the present embodiment.

As shown in Figure 1, the present invention first uses quartz sand and soda ash as raw materials, mixes them uniformly and then calcines to prepare sodium silicate, then reacts sodium silicate with sodium bicarbonate solution, and controls the supersaturation of the solution to crystallize and hydrate Silica is precipitated, and the filtered precipitate is washed and dried to obtain precipitated silica products, while the filtrate sodium carbonate is recycled.

Example 1

Mix 600g of quartz sand with 1270g of soda ash, and calcinate at 1300°C for 60 minutes to obtain 1205g of solid sodium silicate, while recovering CO ₂ . Solid sodium silicate was dissolved in sodium carbonate solution to obtain 1.2mol/L sodium silicate solution.

Put 500mL of sodium silicate solution in a 10L crystallization reactor, control the temperature at 40°C, turn on the stirrer, and use a peristaltic pump to add dropwise a sodium bicarbonate solution with a concentration of 2.7mol/L. By adjusting the drop rate of the solution and To control the degree of supersaturation, a total of 700 mL of sodium bicarbonate solution was added dropwise to precipitate hydrated silica.

The suspension in the crystallization reactor was filtered. Filter to obtain 1160mL sodium carbonate solution, wherein 500mL sodium carbonate solution absorbs _CO gas to obtain 2.7mol/L sodium bicarbonate solution, which is returned to the peristaltic pump for recycling; 300mL sodium carbonate solution is used to dissolve solid sodium silicate; the remaining sodium carbonate The solution is concentrated by evaporation and returned to the calcination process. The filtered precipitate was washed, dried and pulverized to obtain 582g of precipitated silica product with a silica content of 99.90wt%.

Example 2

Mix 1000g of quartz sand with 2650g of soda ash and calcinate at 1350°C for 60 minutes to obtain 1880g of solid sodium silicate, while recovering CO ₂ . Solid sodium silicate was dissolved in sodium carbonate solution to obtain 1.2mol/L sodium silicate solution.

Put 800mL of sodium silicate solution in a 10L crystallization reactor, control the temperature at 45°C, turn on the stirrer, and use a peristaltic pump to add dropwise a sodium bicarbonate solution with a concentration of 2.7mol/L. By adjusting the drop rate of the solution and To control the degree of supersaturation, a total of 1120 mL of sodium bicarbonate solution was added dropwise to precipitate hydrated silica.

The suspension in the crystallization reactor was filtered. Filter to obtain 1870mL sodium carbonate solution, wherein 800mL sodium carbonate solution absorbs _CO gas to obtain 2.7mol/L sodium bicarbonate solution, which is returned to the peristaltic pump for recycling; 500mL sodium carbonate solution is used to dissolve solid sodium silicate; the remaining sodium carbonate The solution is concentrated by evaporation and returned to the calcination process. The filtered precipitate was washed, dried and pulverized to obtain 915g of precipitated silica product with a silica content of 99.92wt%.

Example 3

Mix 1,000g of quartz sand with 3,000g of soda ash, and calcinate at 1,400°C for 60 minutes to obtain 1,975g of solid sodium silicate, while recovering CO ₂ . Solid sodium silicate was dissolved in sodium carbonate solution to obtain 1.2mol/L sodium silicate solution.

Put 1000mL of sodium silicate solution in a 10L crystallization reactor, control the temperature at 50°C, turn on the stirrer, and use a peristaltic pump to add dropwise a sodium bicarbonate solution with a concentration of 2.7mol/L. By adjusting the drop rate of the solution and To control the degree of supersaturation, a total of 1400 mL of sodium bicarbonate solution was added dropwise to precipitate hydrated silica.

The suspension in the crystallization reactor was filtered. Filter to obtain 2275mL sodium carbonate solution, wherein 1000mL sodium carbonate solution absorbs _CO gas to obtain 2.7mol/L sodium bicarbonate solution, which is returned to the peristaltic pump for recycling; 600mL sodium carbonate solution is used to dissolve solid sodium silicate; the remaining sodium carbonate The solution is concentrated by evaporation and returned to the calcination process. The filtered precipitate was washed, dried and pulverized to obtain 952g of high-purity precipitated silica product with a silica content of 99.95wt%.

In a word, the precipitated silica product obtained by the present invention has a purity of more than 99.9%, uniform particle size distribution, and the recycling of materials in the entire production process, which overcomes the problem of sodium sulfate sewage discharge in conventional production.

It should be noted that, according to the above-mentioned embodiments of the present invention, those skilled in the art can fully realize the full scope of the independent claims and dependent rights of the present invention, and the implementation process and method are the same as the above-mentioned embodiments; and the present invention is not elaborated Some of them belong to well-known technologies in the art.

The above are only some specific implementations of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be covered within the protection scope of the present invention.

Claims (6)

1. one kind is utilized sodium bicarbonate to control the method that degree of supersaturation is produced precipitated silica, it is characterized in that performing step is as follows:

(1) quartz sand and soda ash are prepared burden on request, calcine 30～60min and obtain solid-state water glass under 1300～1400 ℃, reclaim CO simultaneously ₂; Mole proportioning of described quartz sand and soda ash is 1:(1.2～1.8);

(2) solid-state water glass dissolves in sodium carbonate solution, obtains sodium silicate solution;

(3) the resulting sodium silicate solution of step (2) is placed in to crystallization reactor, controls temperature, turn on agitator, drip sodium hydrogen carbonate solution with peristaltic pump, control degree of supersaturation by drop rate and the dripping quantity of adjusting solution, separate out the hydrated SiO 2 precipitation, obtain suspension;

(4) the resulting suspension of step (3) is filtered, obtain hydrated SiO 2 precipitation and sodium carbonate filtrate, the precipitation after filtration makes the precipitated silica product through washing, drying, pulverizing;

(5) the filtrate sodium bicarbonate that step (4) obtains divides three partially recycled utilizations: the CO that a part of sodium carbonate solution absorption step (1) obtains ₂gas, control gas flow, obtains sodium hydrogen carbonate solution, turns back to step (3) and recycle; Part sodium carbonate solution turns back to step (2), for dissolving solid-state water glass; The last part sodium carbonate solution, through evaporation concentration, turns back to step (1) and is calcined.

2. method according to claim 1, it is characterized in that: the specification of the described quartz sand of step (1) is 40～70 orders, SiO ₂content is 98.8%.

3. method according to claim 1, it is characterized in that: the concentration of the resulting sodium silicate solution of step (2) is 1.2mol/L.

4. method according to claim 1 is characterized in that: in step (3), the crystallization reaction actuator temperature is controlled at 40～50 ℃.

5. method according to claim 1, it is characterized in that: the concentration of the sodium hydrogen carbonate solution dripped in step (3) is 2.7mol/L.

6. method according to claim 1, it is characterized in that: described step (5) precipitated silica product purity is up to more than 99.9%.

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