CN105566170B - A kind of dilute sulfuric acid recoverying and utilizing method - Google Patents

Abstract

The invention discloses a method for recycling dilute sulfuric acid, which is characterized in that it comprises the following steps: rectifying the dilute sulfuric acid together with dicyclic aromatic hydrocarbons or/and polycyclic aromatic hydrocarbons in a rectifying reactor, During the process, water is a light component, which is extracted from the top of the rectification tower, the concentration of sulfuric acid in the kettle rises, and the temperature of the kettle rises; when the mass concentration of sulfuric acid in the kettle is >63%, the temperature in the kettle is 150-175°C, Sulfuric acid undergoes sulfonation reaction with bicyclic aromatic hydrocarbons or/and polycyclic aromatic hydrocarbons to generate water at the same time. The concentration of sulfuric acid decreases and rectification produces water. This cycle is repeated until the reaction of sulfuric acid in the tank is completely consumed. The invention combines rectification, concentration and utilization of dilute sulfuric acid with sulfonation of bicyclic/polycyclic aromatic hydrocarbons, and can realize the concentration and utilization of dilute sulfuric acid without high temperature.

Description

A kind of dilute sulfuric acid recycling method

Technical field:

The invention belongs to the field of chemical industry, and in particular relates to a recycling method for preparing related sulfonic acid products by combining concentration and sulfonation of dilute sulfuric acid.

Background technique:

Sulfuric acid is widely used in chemical, steel and other industries. However, during the application process of sulfuric acid in catalysis and dehydration, it becomes dilute sulfuric acid due to water absorption or reaction to generate water. The whereabouts of dilute sulfuric acid after losing dehydration and catalytic ability is a very thorny issue at present. If the dilute sulfuric acid is discharged into the environment without treatment, it will cause water or soil acidification, endanger the ecological environment, and waste a lot of resources. Patents such as CN102951627A use methods such as production of gypsum or phosphate fertilizer to process dilute sulfuric acid, but with the development of the chemical industry and the needs of environmental protection, this treatment method can no longer meet the demand. Therefore, it is necessary to recycle dilute sulfuric acid after being concentrated.

At present, there are two main types of dilute sulfuric acid concentration methods. Atmospheric pressure method: such as CN101214931A, dilute sulfuric acid is placed in the evaporator, and the evaporator is directly heated with fuel or heated by a heat exchanger under normal pressure to achieve the purpose of dilute sulfuric acid concentration. Since the boiling point of sulfuric acid is as high as 338°C, high temperature is required for direct concentration of sulfuric acid under normal pressure, and at high temperature, sulfuric acid is very corrosive. concentrated dilute sulfuric acid. That is, under reduced pressure, the method and equipment for heating dilute sulfuric acid with a heat exchanger and evaporating at the same time. However, a small amount of sulfuric acid volatilizes unavoidably during the distillation process, which is difficult to solve for the corrosion of equipment such as vacuum pumps. The vacuum system can only use water ring pumps, etc., and the decompression capacity is limited, so the concentration temperature of dilute sulfuric acid still needs to be very high. In short, at present, the concentration of dilute sulfuric acid can only reach 70% or less of sulfuric acid, and 70% of sulfuric acid still has no functions such as dehydration and catalysis, and cannot achieve the purpose of concentration and utilization. And to further achieve more than 90% sulfuric acid, it needs to be carried out at high temperature. High temperature sulfuric acid, especially high temperature concentrated sulfuric acid, is strongly corrosive, which puts forward extremely high requirements on the material of the heat exchanger, and requires expensive rare metals. For example, tantalum, zirconium and special alloys are used to make heat exchangers. In addition, the use of evaporation and concentration requires a lot of energy, which increases the concentration cost of dilute sulfuric acid, thus limiting the recycling of waste dilute sulfuric acid. In addition, dilute sulfuric acid often contains other organic impurities, which are prone to condensation, carbonization and other reactions at high temperatures, which will affect the reuse after concentration.

CN 102688706 A proposes to use membrane treatment to concentrate dilute sulfuric acid, but as the concentration increases, the osmotic pressure will increase significantly, so membrane treatment can only obtain sulfuric acid with a concentration of 70% or less, which is far from reaching the purpose of utilization.

On the other hand, sulfonic acid and its salt obtained by sulfonation of many aromatic hydrocarbons are widely used surfactants, such as CN103626637B, CN103864332A, CN102503223A, CN102746196A, etc. by sulfonating naphthalene, methylnaphthalene, washing oil, etc. in concentrated sulfuric acid to obtain The corresponding sulfonic acid products; some are further decondensed, neutralized and other steps to prepare naphthalene-based high-efficiency cement superplasticizers, MF dispersants, etc. In these processes, concentrated sulfuric acid with a mass fraction >90% is required, and the reaction is carried out at a high temperature of 160°C; in addition, molecular water is generated during the sulfonation process, which reduces the concentration of sulfuric acid and loses the sulfonation ability. Therefore, in the actual reaction , the amount of sulfuric acid needs to be over 20% to ensure the complete sulfonation of organic matter, resulting in a large amount of dilute waste acid, which has an adverse effect on product quality. For example, the current preparation methods of naphthalene-based water reducers mainly include sulfonation, After hydrolysis, condensation, neutralization and other reactions, the product is obtained by drying. The naphthalene-based water-reducing agent obtained by this method has a low concentration and contains about 20-25% of sodium sulfate (accounting for powder), which increases the loss of concrete slump and is not suitable for self-flowing grouting and preparation of pumped concrete, which affects construction progress and quality. The Na ₂ SO ₄ in low-concentration naphthalene-based superplasticizer products will crystallize below 15°C, which seriously affects the accuracy of concrete metering pumps and water-reducing effect. The method of _CN103755203A when separating _Na2SO4 is to dilute the product with water, add lime to make excess sulfuric acid produce calcium sulfate, and separate by filtration, separation and removal are difficult, and the separated waste acid or salt will cause serious environmental pollution.

Invention content:

In view of the above problems, the present invention provides a method for recycling dilute sulfuric acid, which can realize the concentration and utilization of dilute sulfuric acid without high temperature.

The technical scheme that the present invention takes is as follows:

A method for recycling dilute sulfuric acid is characterized in that it comprises the following steps: in a reactor with rectification, dilute sulfuric acid is rectified together with bicyclic aromatic hydrocarbons or/and polycyclic aromatic hydrocarbons, and during the rectification process, water It is a light component, which is extracted from the top of the rectification tower. The concentration of sulfuric acid in the kettle increases, and the temperature in the kettle rises; Aromatic hydrocarbons or/and polycyclic aromatic hydrocarbons undergo sulfonation reactions, and water is formed at the same time, and the concentration of sulfuric acid decreases. During the whole process, due to the production of rectification water and the water produced by sulfonation, the balance is reached, and the temperature in the kettle is stable at 150-175°C until the The internal sulfuric acid reaction is completely consumed.

Further settings are as follows:

The dilute sulfuric acid is sulfuric acid with a concentration of 2-40%. Preferably, the dilute sulfuric acid is first concentrated to a concentration >40%, and then the concentrated sulfuric acid is used for sulfonation of bicyclic aromatic hydrocarbons or/and polycyclic aromatic hydrocarbons. The concentration method adopts any one of multiple effect distillation, membrane concentration and MVR technology.

Due to the rectification and dehydration, the concentration of dilute sulfuric acid is gradually increased to ensure the sulfonation ability. Therefore, the quantitative reaction between bicyclic aromatic hydrocarbons or/and polycyclic aromatic hydrocarbons and sulfuric acid is adopted, and there is no need to add excessive sulfuric acid.

The sulfuric acid and bicyclic aromatic hydrocarbons or/and polycyclic aromatic hydrocarbons undergo a sulfonation reaction under rectification to prepare aromatic hydrocarbon sulfonic acids, and the aromatic hydrocarbon sulfonic acids are further prepared into cement water reducers or MF dispersants.

The bicyclic aromatic hydrocarbon used for sulfonation is selected from any one of naphthalene, methylnaphthalene, dialkyl-substituted naphthalene, polyalkyl-substituted naphthalene, naphthol, naphthylamine, anthracene, phenanthrene and their substitutes.

The polycyclic aromatic hydrocarbons used for sulfonation are condensed ring aromatic hydrocarbons.

The mixture of dicyclic aromatic hydrocarbons and polycyclic aromatic hydrocarbons used for sulfonation is selected from washing oil and coal tar.

Preferably, the temperature in the reactor is controlled at 160-165°C, and the concentration of sulfuric acid is 65-68%.

Working principle of the present invention and beneficial effect are as follows:

1. The present invention combines dilute sulfuric acid rectification and concentration utilization with the sulfonation of bicyclic/polycyclic aromatic hydrocarbons to prepare bicyclic/polycyclic aromatic hydrocarbon sulfonic acids (taking naphthalenesulfonic acid as an example):

Dilute sulfuric acid and naphthalene are rectified together. During the rectification process, water is the light component, which is extracted from the top of the rectification tower. The concentration of sulfuric acid in the tank increases, and the temperature of the rectification tank rises. When the mass concentration of sulfuric acid in the kettle is >63%, the temperature in the kettle is about 150-175°C. At this temperature, sulfuric acid and naphthalene undergo a sulfonation reaction, and water is generated at the same time, reducing the concentration of sulfuric acid. The whole process is rectification to produce water, sulfonation to produce water to reach equilibrium, so that the temperature in the kettle is stabilized between 150 and 175°C without further rise. As the sulfuric acid reaction in the kettle is consumed, the sulfonation reaction will no longer produce water, and the system temperature will rise further, thereby avoiding the high temperature phenomenon (>180°C) required for the concentration of sulfuric acid. In addition, the concentration of dilute sulfuric acid will gradually increase due to the rectification and dehydration. As a result, the sulfonation ability can be guaranteed by rising, so the quantitative reaction between naphthalene and sulfuric acid can be achieved, and there is no need to add excessive sulfuric acid to achieve energy saving and consumption reduction.

Note: At 1 atm, the boiling point of sulfuric acid with a mass concentration of 60% is 142°C, and the boiling point of sulfuric acid with a mass concentration of 70% is 170°C. When the temperature in the kettle is 160-165°C, the concentration of sulfuric acid is 65-68%. Sulfuric acid can be used as a sulfonating agent to sulfonate naphthalene (and other bicyclic and polycyclic aromatic hydrocarbons) into corresponding sulfonic acids.

The situation of other bicyclic and polycyclic aromatic hydrocarbons is the same as that of naphthalene, or it is easier to sulfonate than naphthalene, so that the reaction-distillation equilibrium temperature is lower, and it is easier to realize the combination of dilute sulfuric acid concentration and sulfonation reaction.

The present invention will be further described below in combination with specific embodiments.

detailed description:

The present invention can be better understood from the following examples. However, those skilled in the art will readily understand that the specific material ratios, process conditions and results described in the examples are only used to illustrate the present invention, and should not and will not limit the present invention described in detail in the claims . The raw materials used in the embodiments are all obtained through commercial purchase.

Embodiment 1: Preparation of β-naphthalenesulfonic acid.

Add 134g of industrial naphthalene (purity ≥ 95%, 1.0mol), 121g of sulfuric acid (mass concentration: 85%, 1.05mol) into the reaction flask, with a 20cm rectification column on the reaction flask, and raise the temperature to 160-170°C to react the refined After distillation for 1.5h, 16g of water was produced during the period. After the reaction, the sample was analyzed by liquid chromatography to obtain 8.51% of α-naphthalenesulfonic acid and 88.3% of β-naphthalenesulfonic acid.

Example 2: Preparation of naphthalene-based cement water reducer.

Add 134g industrial naphthalene (purity ≥ 95%, 1.0mol) and 178.0g sulfuric acid (mass concentration: 55%, 1.0mol) to the reaction flask, heat up to 135°C and start back distillation, produce water, continue to rectify and heat up to 165～ React at 175°C for 9 hours. After the reaction, the measured acidity is 26%; cool down to 95°C, add 30.7g of paraformaldehyde (purity ≥ 99%, 1mol is calculated as formaldehyde) and 54.0g of water, and gradually heat up to 100-110°C , keep warm for 8h, add water to control the polymerization under proper viscosity during the keep warm process. After the reaction is finished, add liquid caustic soda to adjust the pH=6-8, and dry to obtain the naphthalene-based cement water-reducer. The sodium sulfate content is 8.7%.

Comparative example: Naphthalene-based cement superplasticizer was prepared by using concentrated sulfuric acid.

1. According to the number of parts by weight, add 160 parts of liquid industrial naphthalene to the reaction kettle, stir and heat up to 135 °C, start to drop 120 parts of sulfuric acid with a concentration of 98%, and control the adding speed so that the temperature does not exceed 165 °C. Insulation binary azeotropic reflux for 4h, control acidity is 25%; simultaneously "azeotrope" obtains 18 parts of waste water (dilute sulfuric acid solution) and needs additional treatment.

2. Cool the material obtained in step 1 to 115°C, then add 23 parts of water to the reaction kettle, slowly raise the temperature to 130°C, use the binary azeotropic method to recover naphthalene, control the acidity to 26%, and stop hydrolysis;

3. Cool the material obtained in step 2 to 110°C, start to add 100 parts of formaldehyde dropwise, control the drop rate, and complete the dropwise addition within 3 hours, then keep warm and condense for 5 hours, and recover formaldehyde at the same time during this step;

4. Add 170 parts of alkali to the condensate obtained in step 3 for neutralization, and then dry to obtain the naphthalene-based cement water reducer, which contains 21.6% sodium sulfate by mass.

Example 3: Preparation of MF dispersant.

Add 150g industrial methylnaphthalene (purity ≥95%, 1.0mol), 196.0g sulfuric acid (mass concentration: 55%, 1.1mol) to the reaction flask, heat up to 135°C and start back distillation, produce water, continue to rectify and heat up to React at 160-170°C for 9 hours. After the reaction, the measured acidity is 28%. Cool down to 95°C, add 30.7g of paraformaldehyde (purity ≥ 99%, 1mol is calculated as formaldehyde) and 54.0g of water, gradually raise the temperature to 100-110°C, keep warm for 8 hours, add water during the heat preservation process to control polymerization at an appropriate viscosity. After the reaction is finished, add liquid caustic soda to adjust pH=6-8, and dry to obtain MF dispersant.

Example 4: Preparation of MF dispersant.

Add 200g of washing oil and 217.0g of sulfuric acid (mass concentration: 45%, 1.1mol) into the reaction bottle, start back distillation when the temperature is raised to 130°C, extract water, continue rectification, raise the temperature to 155-165°C for 9 hours, after the reaction, The measured acidity is 26%; cool down to 95°C, add 30.7g of paraformaldehyde (purity ≥ 99%, 1mol is calculated as formaldehyde) and 54.0g of water, gradually raise the temperature to 100-110°C, keep warm for 8 hours, add water during the keep warm Polymerize under suitable viscosity. After the reaction, add liquid caustic soda to adjust pH=6-8, dry to obtain MF dispersant.

Claims (8)

1. a method for reclaiming dilute sulfuric acid, is characterized in that, comprises the following steps: in the reactor with rectification, dilute sulfuric acid is rectified together with bicyclic aromatic hydrocarbon or/and polycyclic aromatic hydrocarbon, in rectifying process , water is the light component, extracted from the top of the rectification tower, the concentration of sulfuric acid in the kettle rises, and the temperature in the kettle rises; when the mass concentration of sulfuric acid in the kettle is >63%, the temperature in the kettle is 150-175°C, sulfuric acid and Bicyclic aromatic hydrocarbons or/and polycyclic aromatic hydrocarbons undergo sulfonation reactions, and water is formed at the same time, and the concentration of sulfuric acid decreases. During the whole process, due to the production of rectification water and the water produced by sulfonation, the balance is reached, and the temperature in the kettle is stabilized and controlled at 150-170°C. The concentration is 55-70%, until the sulfuric acid reaction in the kettle is completely consumed; The dilute sulfuric acid is sulfuric acid with a concentration of 2-40%. 2. a kind of dilute sulfuric acid recycling method according to claim 1 is characterized in that: dilute sulfuric acid is first concentrated to concentration > 40%, then the sulfuric acid after the above-mentioned concentration is used for dicyclic aromatic hydrocarbons or/and polycyclic aromatic hydrocarbons sulfonation reaction. 3. a kind of dilute sulfuric acid recycling method according to claim 2 is characterized in that: the concentration method adopts any one of multiple-effect distillation, membrane concentration, MVR technology. 4. the method for a kind of dilute sulfuric acid recycling according to claim 1 is characterized in that: due to rectification dehydration action dilute sulfuric acid concentration rises gradually and guarantees sulfonation ability, therefore, bicyclic aromatic hydrocarbon or/and polycyclic aromatic hydrocarbon and polycyclic aromatic hydrocarbon Quantitative reaction is adopted between sulfuric acid, and there is no need to add excessive sulfuric acid. 5. the method for a kind of dilute sulfuric acid recycling according to claim 1 is characterized in that: described sulfuric acid and bicyclic aromatic hydrocarbon or/and polycyclic aromatic hydrocarbon take place sulfonation reaction under rectification, prepare aromatic hydrocarbon sulfonic acid, the The aromatic hydrocarbon sulfonic acid is further prepared into cement water reducer or MF dispersant. 6. the method for a kind of dilute sulfuric acid recycling according to claim 1 is characterized in that: the bicyclic aromatic hydrocarbon used for sulfonation is selected from naphthalene, methylnaphthalene, dialkyl substituted naphthalene, polyalkyl substituted naphthalene, Naphthol, naphthylamine, and any one of anthracene and phenanthrene. 7. The method for recycling dilute sulfuric acid according to claim 1, characterized in that: the polycyclic aromatic hydrocarbons used for sulfonation are fused-ring aromatic hydrocarbons. 8. A method for recycling dilute sulfuric acid according to claim 1, characterized in that: the mixture of dicyclic aromatic hydrocarbons and polycyclic aromatic hydrocarbons used for sulfonation is selected from washing oil and coal tar.