CN101045538A - Method for preparing modified silicon oxide using coal series kaolin rock or flyash - Google Patents

Abstract

The invention discloses a method for preparing modified silicon oxide from coal series kaolinite or fly ash. It is obtained by drying, grinding, magnetically separating and calcining coal-measure kaolinite or fly ash, and leaching with inorganic acid to form a silicon-rich precipitate phase and an aluminum-rich solution phase, and the aluminum-rich liquid phase is refined, concentrated, and crystallized. Aluminum salt; the silicon-rich solid phase is dissolved in alkali and acid-precipitated to obtain crude silicon oxide; the crude silicon oxide is activated with acid to fully hydroxylate the surface of silicon oxide, and impurities such as aluminum, iron, calcium, and magnesium are removed by filtration and washing. Purified silicon oxide is obtained, and its surface is modified with a coupling agent to obtain a modified silicon oxide product. The method for preparing silicon oxide products from coal series kaolinite or fly ash of the present invention has simple preparation technology and mild operating conditions, and the prepared silicon oxide products have good dispersibility and compatibility in the organic phase, and are suitable for coal It provides a new method for the high value-added and high-efficiency utilization of kaolinite or fly ash.

Description

A method for preparing modified silicon oxide from coal-measure kaolinite or fly ash

technical field

The invention relates to the field of resource deep processing and utilization of coal series kaolinite or fly ash, in particular to a method for preparing modified silicon oxide from coal series kaolinite or fly ash.

Background technique

Coal-measure kaolinite and fly ash are mainly composed of Al ₂ O ₃ and SiO ₂ . Traditionally, coal-measure kaolinite and fly ash are regarded as industrial waste. In the pitheads and coal washing plants of large coal mines in China, As well as large coal-fired thermal power plants, there are mountains of coal-measure kaolinite and fly ash, and they are still increasing at a rate of hundreds of millions of tons per year. They not only occupy a large amount of land, but also seriously pollute the ecological environment. public nuisance.

The expansion of the production capacity of my country's aluminum smelting industry has resulted in a shortage of alumina in the domestic and foreign markets, and has also caused a serious shortage of domestic bauxite resources. The technical demand for extracting alumina from coal gangue and fly ash and comprehensively utilizing silica is very urgent.

The direction of resource utilization of coal-measure kaolinite or fly ash is mainly to extract aluminum salt and produce alumina, but the remaining silica slag is only used as industrial waste or used to produce cement. For example, Poland used this technology in 1953 A production line with an annual output of 10,000 tons of alumina and 100,000 tons of cement has been built. This technology has problems such as irrational product structure, high material consumption, and high energy consumption, making it difficult to further develop. High-purity silica is an important material in many high-tech industries, and is widely used in polymer composite materials, special inks, paints, coatings, ceramics, electronic components and precision optical glass. With the rapid development of high-tech industries, high-tech The market demand for high-grade, multi-variety, high-purity, functionalized modified silica products continues to increase, and there is a strong market demand. Therefore, it is of great significance to prepare high-purity silica and its modified products by using coal-measure kaolinite or fly ash.

my country's coal-measure kaolinite or fly ash silica slag are also traditionally used as raw materials for the preparation of white carbon black. Since the product positioning is mainly primary products, the added value is low, and the economic benefits are not obvious. my country's high-purity white carbon black production And modification technology is relatively backward, only small-scale trial production, and the quality is poor. At present, the Chinese modified silica market is basically occupied by products from foreign companies such as the United States, Germany, and Japan.

Contents of the invention

The purpose of the present invention is to provide a method for preparing modified silicon oxide from coal series kaolinite or fly ash.

The method for preparing modified silicon oxide from coal-measure kaolinite or fly ash is to use coal-measure kaolinite or fly ash as raw materials, and through acid leaching to form a silicon-rich solid phase and an aluminum-rich solution phase. Alkali dissolution, acid precipitation, acid activation purification, surface modification to prepare modified silica, the specific steps are as follows:

1) Coal series kaolinite or fly ash is dried, crushed, dry magnetically separated, then calcined at 550-850°C for 1-4 hours, mixed with acid with a mass percentage concentration of 20-35%, and heated at 100 Leach at ~250°C for 1-4 hours; filter or centrifuge, dissolve the silicon-rich solid phase with alkali to form water glass, precipitate, filter, wash, and dry to obtain crude silicon oxide;

2) Activate the crude silicon oxide obtained in step 1) with an acid with a concentration of 1-3M at a temperature of 60-90°C for 2-3 hours, control the pH of the system not higher than 4, filter, wash, and dry to obtain the activated oxidation product. silicon;

3) Disperse the activated silicon oxide obtained in step 2) in an organic solvent at a solid-to-liquid ratio of 1:5-10, add a coupling agent equivalent to 0.5-10% of the weight of activated silicon oxide, and heat up to reflux reaction at 0.5 ~2 hours, filter, and dry the filter cake to obtain modified silica.

Described acid is hydrochloric acid, sulfuric acid or nitric acid. The organic solvent is methanol, ethanol, propanol or isopropanol. The coupling agent is a silane coupling agent, a titanate coupling agent or a stearic acid coupling agent. The silane coupling agent is trimethylethoxysilane, methyltrimethoxysilane, vinyltriethoxysilane, tetrabutoxysilane or hexamethyldisilazane. The titanate coupling agent is (tetra) isopropyl titanate or (tetra) n-butyl titanate. The stearic acid coupling agent is stearic acid, iron stearate, calcium stearate or magnesium stearate.

The invention has mild operating conditions, simple process, low equipment investment and energy consumption; wide source of raw materials and low price; compared with the existing coal series kaolinite or fly ash deep processing technology, the prepared product has a higher market positioning , can be widely used in high-tech industries such as polymer composite materials, special inks, paints, coatings, ceramics, electronic components and precision optical glass, and has good economic and social benefits.

Detailed ways

In the present invention, coal series kaolinite or fly ash is dried, ground, magnetically separated, and calcined into metakaolin, and a silicon-rich precipitate phase and an aluminum-rich solution phase are formed by leaching with an inorganic acid, and the aluminum-rich liquid phase is refined. , concentration, and crystallization to obtain aluminum salt; the silicon-rich solid phase is dissolved in alkali to obtain water glass, filtered, and inorganic acid is added to precipitate to obtain crude silicon oxide. The methods of impurity removal, activation, and acid-base extraction are well known.

The surface modification of silicon oxide includes two steps of pre-activation treatment and surface modification. The content of hydroxyl groups (-OH) on the surface of silicon oxide is the key factor affecting the modification effect. The method for preparing modified silicon oxide products from coal series kaolinite or fly ash provided by the present invention is characterized in that the catalysis in inorganic acid is used to break the silicon-oxygen bond (Si-O-Si) to obtain a surface Fully hydroxylated (-OH) silica particles improve the effect of the subsequent surface modification of the coupling agent and can improve its dispersion and compatibility in the organic phase.

In addition, after acid leaching of coal-measure kaolinite or fly ash, the content of impurities such as iron, titanium, calcium, and magnesium in silicon slag is relatively low, but it contains a certain amount of alumina that has not been leached by acid. During the silicon oxide reaction, alumina is also involved to generate sodium metaaluminate and enter the solution, which is mixed in the white carbon black in the form of amorphous aluminosilicate in the subsequent process, which affects product quality; the present invention provides A method for preparing modified silica products from coal series kaolinite or fly ash. In the process of activating silica, impurities such as aluminum, iron, calcium, and magnesium can be further removed by filtering and washing. The two steps of refining and activating Two into one, the process is simple.

The present invention is further illustrated in conjunction with the following examples, but the content of the present invention is not limited to the content involved in the examples.

Example 1

1) Dry coal series kaolinite or fly ash, pulverize, dry magnetic separation, then calcinate at 550°C for 1 hour, mix with hydrochloric acid with a concentration of 20% by mass, and extract at 100°C for 1 hour ; Filtration or centrifugation, dissolving the silicon-rich solid phase with alkali to form water glass, precipitation, filtration, washing, and drying to obtain crude silicon oxide;

2) Activate the crude silica obtained in step 1) with 1M hydrochloric acid at a temperature of 60° C. for 2 hours, control the pH of the system to 2, filter, wash, and dry to obtain activated silica;

3) Disperse the activated silicon oxide obtained in step 2) in methanol organic solvent at a solid-to-liquid ratio of 1:5, add trimethylethoxysilane equivalent to 0.5% by weight of activated silicon oxide, and heat up to reflux reaction After 0.5 hour, filter and dry the filter cake to obtain modified silica.

Example 2

1) Dry coal series kaolinite or fly ash, pulverize, dry magnetic separation, then calcinate at 850°C for 4 hours, mix with sulfuric acid with a concentration of 35% by mass, and extract at 250°C for 4 hours ; Filtration or centrifugation, dissolving the silicon-rich solid phase with alkali to form water glass, precipitation, filtration, washing, and drying to obtain crude silicon oxide;

2) Activate the crude silica obtained in step 1) with 3M sulfuric acid at a temperature of 90° C. for 3 hours, control the pH of the system to 3, filter, wash, and dry to obtain activated silica;

3) Disperse the activated silicon oxide obtained in step 2) in an organic solvent at a solid-to-liquid ratio of 1:10, add (tetra)isopropyl titanate equivalent to 10% by weight of the activated silicon oxide, and heat up to reflux reaction After 2 hours, filter and dry the filter cake to obtain modified silica.

Example 3

1) Coal series kaolinite is dried, pulverized, dry magnetically separated, then calcined at 550°C for 4 hours, mixed with hydrochloric acid with a mass percentage concentration of 20%, and leached at 100°C for 1 hour; filtered, and The silicon-rich solid phase is dissolved with sodium hydroxide to form water glass, which is precipitated, filtered, washed, and dried to obtain crude silicon oxide;

2) Activate the crude silicon oxide obtained in step 1) with 1M hydrochloric acid at a temperature of 60° C. for two hours, control the pH of the system to 3.8, filter, wash, and dry to obtain activated silicon oxide.

3) Disperse the activated silica obtained in step 2) in methanol at a solid-to-liquid ratio of 1:5, add trimethylethoxysilane equivalent to 0.5% by weight of activated silica, and heat up to reflux for 0.5 hours , filter, and dry the filter cake to obtain modified silica.

Example 4

1) Coal series kaolinite is dried, pulverized, dry-magnetically separated, then calcined at 850°C for 1 hour, mixed with sulfuric acid with a mass percentage concentration of 35%, and extracted at 250°C for 4 hours; centrifuged, Dissolve the silicon-rich solid phase with sodium carbonate to form water glass, precipitate, filter, wash, and dry to obtain crude silicon oxide;

2) Activate the crude silicon oxide obtained in step 1) with 1M sulfuric acid at a temperature of 90° C. for two hours, control the pH of the system to 3, filter, wash, and dry to obtain activated silicon oxide.

3) Disperse the activated silicon oxide obtained in step 2) in ethanol at a solid-to-liquid ratio of 1:5, add hexamethyldisilazane equivalent to 10% by weight of the activated silicon oxide, and heat up to reflux for 2 hours , filter, and dry the filter cake to obtain modified silica.

Example 5

1) Dry the fly ash, pulverize it, dry magnetic separation, then calcinate at 650°C for 2 hours, mix it with nitric acid with a mass percentage concentration of 25%, and extract it at 125°C for 2 hours; The solid phase is dissolved with sodium carbonate to form water glass, which is precipitated, filtered, washed, and dried to obtain crude silicon oxide;

2) Activate the crude silicon oxide obtained in step 1) with 1M nitric acid at a temperature of 70° C. for two hours, control the pH of the system to 2, filter, wash, and dry to obtain activated silicon oxide.

3) Disperse the activated silicon oxide obtained in step 2) in propanol at a solid-to-liquid ratio of 1:5, add (tetra)isopropyl titanate equivalent to 2% by weight of activated silicon oxide, and heat up to reflux reaction After 1 hour, filter and dry the filter cake to obtain modified silica.

Example 6

1) Coal series kaolinite is dried, pulverized, dry magnetically separated, then calcined at 700°C for 2 hours, mixed with sulfuric acid with a mass percentage concentration of 25%, and extracted at 200°C for 2 hours; filtered, and The silicon-rich solid phase is dissolved with sodium hydroxide to form water glass, which is precipitated, filtered, washed, and dried to obtain crude silicon oxide;

2) Activate the crude silicon oxide obtained in step 1) with 1M sulfuric acid at a temperature of 90° C. for two hours, control the pH of the system to 1, filter, wash, and dry to obtain activated silicon oxide.

3) Disperse the activated silica obtained in step 2) in isopropanol at a solid-to-liquid ratio of 1:5, add (tetra)n-butyl titanate equivalent to 5% by weight of the activated silica, and heat up to reflux React for 1.5 hours, filter, and dry the filter cake to obtain modified silica.

Example 7

1) Dry coal-based fly ash, pulverize, dry magnetic separation, then calcinate at 750°C for 1.5 hours, mix with nitric acid with a mass percentage concentration of 30%, and extract at 150°C for 3 hours; filter or centrifuge Separation, dissolving the silicon-rich solid phase with sodium carbonate to generate water glass, precipitation, filtration, washing, and drying to obtain crude silicon oxide;

2) Activate the crude silica obtained in step 1) with 1M nitric acid at a temperature of 80° C. for two hours, control the pH of the system to 2.5, filter, wash, and dry to obtain activated silica.

3) Disperse the activated silicon oxide obtained in step 2) in ethanol at a solid-to-liquid ratio of 1:5, add stearic acid equivalent to 2% by weight of activated silicon oxide, heat up to reflux for 1.5 hours, filter, filter The cake is dried to obtain modified silica.

Example 8

1) Dried coal-based fly ash, pulverized, dry-magnetic separation, then calcined at 600°C for 4 hours, mixed with hydrochloric acid with a mass percentage concentration of 35%, and extracted at 150°C for 3.5 hours; filtered or centrifuged Separation, dissolving the silicon-rich solid phase with sodium hydroxide to generate water glass, precipitation, filtration, washing, and drying to obtain crude silicon oxide;

2) Activate the crude silica obtained in step 1) with 1M hydrochloric acid at 60°C for two hours, control the pH of the system to 2.5, filter, wash, and dry to obtain activated silica.

3) Disperse the activated silicon oxide obtained in step 2) in isopropanol at a solid-to-liquid ratio of 1:5, add calcium stearate equivalent to 4% by weight of activated silicon oxide, heat up to reflux for 2 hours, Filter and dry the filter cake to obtain modified silica.

Example 9

1) Coal series kaolinite is dried, pulverized, dry magnetically separated, then calcined at 650°C for 4 hours, mixed with sulfuric acid with a mass percentage concentration of 35%, and extracted at 180°C for 2 hours; centrifuged, Dissolve the silicon-rich solid phase with sodium carbonate to form water glass, precipitate, filter, wash, and dry to obtain crude silicon oxide;

2) Activate the crude silica obtained in step 1) with 1M sulfuric acid at a temperature of 70° C. for two hours, control the pH of the system to 1, filter, wash, and dry to obtain activated silica.

3) Disperse the activated silicon oxide obtained in step 2) in ethanol at a solid-to-liquid ratio of 1:5, add magnesium stearate equivalent to 6% by weight of activated silicon oxide, heat up to reflux for 1.5 hours, filter, The filter cake is dried to obtain modified silica.

Claims (7)

1. A method for preparing modified silicon oxide with coal-measure kaolinite or fly ash is characterized in that it is made of coal-measure kaolinite or fly ash as raw material, and is processed into silicon-rich solid phase and rich-silica by acid leaching. The aluminum solution phase and the silicon-rich solid phase are subjected to alkali dissolution, acid precipitation, acid activation purification, and surface modification to obtain modified silica. The specific steps are as follows: 1) Coal series kaolinite or fly ash is dried, crushed, dry magnetically separated, then calcined at 550-850°C for 1-4 hours, mixed with acid with a mass percentage concentration of 20-35%, and heated at 100 Leach at ~250°C for 1-4 hours; filter or centrifuge, dissolve the silicon-rich solid phase with alkali to form water glass, precipitate, filter, wash, and dry to obtain crude silicon oxide; 2) Activate the crude silicon oxide obtained in step 1) with an acid with a concentration of 1-3M at a temperature of 60-90°C for 2-3 hours, control the pH of the system not higher than 4, filter, wash, and dry to obtain the activated oxidation product. silicon; 3) Disperse the activated silicon oxide obtained in step 2) in an organic solvent at a solid-to-liquid ratio of 1:5-10, add a coupling agent equivalent to 0.5-10% of the weight of activated silicon oxide, and heat up to reflux reaction at 0.5 ~2 hours, filter, and dry the filter cake to obtain modified silica. 2. a kind of method as claimed in claim 1 is that raw material prepares modified silica with coal series kaolinite or fly ash, it is characterized in that described acid is hydrochloric acid, sulfuric acid or nitric acid. 3. a kind of method as claimed in claim 1 is that raw material prepares modified silica with coal series kaolinite or fly ash, it is characterized in that described organic solvent is methyl alcohol, ethanol, propanol or isopropanol . 4. a kind of method as claimed in claim 1 is that raw material prepares modified silicon oxide with coal series kaolinite or fly ash, it is characterized in that described coupling agent is silane coupling agent, titanate Coupling agent or stearic acid coupling agent. 5. a kind of as claimed in claim 4 is the method for raw material preparation modified silica with coal series kaolinite or fly ash, it is characterized in that described silane coupling agent is trimethylethoxysilane , methyltrimethoxysilane, vinyltriethoxysilane, tetrabutoxysilane or hexamethyldisilazane. 6. a kind of method as claimed in claim 4 is that raw material prepares modified silica with coal series kaolinite or fly ash, it is characterized in that described titanate coupling agent is titanic acid (tetra)iso Propyl ester or (tetra) n-butyl titanate. 7. a kind of as claimed in claim 4 is the method for raw material preparation modified silicon oxide with coal series kaolinite or fly ash, it is characterized in that described stearic acid coupling agent is stearic acid, stearic acid Iron stearate, calcium stearate or magnesium stearate.