CN1164555C - A kind of method that prepares calcium magnesium acetate salt with underpressure distillation - Google Patents

Abstract

The invention discloses a method for preparing calcium magnesium acetate salt by vacuum distillation, which relates to fine chemical preparation technology. The present invention is to use glacial acetic acid or acetic acid solution and calcium magnesium oxide or calcium magnesium carbonate as raw materials, at first adding the calcium and magnesium compounds whose molar ratio is Ca:Mg=3～4:6～7 in the acetic acid solution and mixing, Prepare a solution with a concentration of (3-5) mol/L, and control the reaction temperature at 40-90°C. After 1-3 hours of reaction, the calcium-magnesium acetate salt solution is filtered, concentrated by vacuum distillation, and dried to obtain granular acetic acid. For calcium and magnesium salts, the distillation pressure is controlled at -0.08 to -0.1 MPa, the temperature is controlled at 45 to 90°C, and the distillation time is controlled at 1 to 5 hours. Compared with methods such as acid-base reaction synthesis method and atmospheric distillation, the preparation method has simple process route, low reaction temperature, small loss rate of acetate ions, and obviously improved product purity.

Description

A kind of method that prepares calcium magnesium acetate salt with underpressure distillation

technical field

The invention relates to a method for preparing calcium magnesium acetate salt by vacuum distillation, which belongs to the technical field of fine chemical preparation.

Background technique

Calcium Magnesium Acetate (CMA) is a calcium-magnesium acetate compound salt, a new environmentally friendly chemical developed in the United States in the early 1980s to replace highway deicing agents (sodium chloride). CMA has good water solubility, low melting point, and biodegradability. Compared with sodium chloride, it can reduce the corrosion of concrete and metal by chloride ions in vehicles and road infrastructure and the pollution of surface water. Studies in recent years have also found that CMA has the function of removing NO _x , SO ₂ produced by coal combustion and HCl produced by PVC combustion, so as to control air pollution. U.S. Patents US4699725 and US4913831 respectively reported the use of X-ray diffraction and "TGA-GC-MSD" (differential thermal-thermogravimetric analysis) to measure the microscopic composition of CMA, which played a certain guiding role in the understanding and analysis of CMA. At present, it is mainly U.S. Patent No. 4,913,831 to introduce the method of synthesizing calcium-magnesium acetate salt with acid-base reaction. Liquid, and then add acetic acid to react; product dehydration, dispersion, drying and granulation processes are simultaneously carried out in a complex design equipment. Patent US4588512 mainly introduces the granulation and drying of calcium magnesium acetate slurry by means of gravel or coagulant. The main defect of the above process has two points, the one, because the granulation drying equipment is complicated, the temperature requirement in the whole reaction process is very high (not lower than 90 ℃), causes the volatilization loss of acetic acid to be bigger, causes product purity to decline; The amount of water required in the reaction process must be continuously adjusted as the fluid enters the drying equipment for granulation and drying flow rate and drying effect, resulting in high energy consumption in the dehydration process.

Contents of the invention

The purpose of this invention is to provide a kind of method that preparation technique and equipment are simple, temperature of reaction is low, product purity is high with vacuum distillation method synthetic calcium magnesium salt.

The present invention proposes a method for preparing calcium-magnesium acetate salt by vacuum distillation, using glacial acetic acid or acetic acid solution and calcium-magnesium oxide or calcium-magnesium carbonate as raw materials, characterized in that calcium and magnesium compounds are added to the acetic acid solution mixed in, the calcium-magnesium acetate solution obtained by the reaction is concentrated through distillation under reduced pressure, and then dried to obtain granular calcium-magnesium acetate salt, and its specific preparation process is carried out as follows:

(1) Acid-base reaction: first add deionized water to the reaction tank at room temperature, slowly add glacial acetic acid to make a solution with a concentration of (3-5) mol/L, and then mix the pre-pulverized calcium and magnesium mixture with chemical The metering ratio is put into the reaction tank, supplemented by stirring, the molar ratio of calcium and magnesium mixture is Ca:Mg=3~4:6~7, the reaction temperature is controlled at (40~90)°C, and the reaction time is (1~3) hours , and finally adjust the pH value in the solution between 7 and 10 by adding a small amount of calcium and magnesium mixture to stop the reaction;

(2) Filtration: the solution prepared in step (1) is filtered, the liquid phase is subjected to vacuum distillation, and the solid phase calcium and magnesium oxide is recovered and reused;

(3) Distillation under reduced pressure: the liquid prepared in step (2) is steamed out of the moisture in the solution under reduced pressure, the distillation pressure is (-0.08～-0.1) MPa, and the distillation temperature is (45～90)°C, The distillation time is (1-5) hours, and the concentrated calcium-magnesium acetate solution can reach white viscous crystals.

In this preparation method, the step (1) in the acid-base reaction can also be taken to add deionized water first in the reaction tank at room temperature, and then add CaO, MgO to form a mixed emulsion of calcium oxide and magnesium oxide, a mixture of calcium and magnesium The mol ratio of Ca: Mg=3～4: 6～7, then slowly add glacial acetic acid, its solution concentration is (3～5) mol/L, and stirring makes it react by the condition of step (1).

Because the present invention adopts conventional underpressure distillation equipment dehydration drying, process route is simple, and reaction temperature is low, and product purity obviously improves, and acetate ion loss rate is about 0.01% (acetate ion loss rate is about 2% during atmospheric distillation, measured The required temperature for atmospheric distillation is 125°C to 130°C). Moreover, the concentration of the mother liquid product obtained by the process reaction is high, the dehydration is simple, and the energy consumption can be saved to the greatest extent.

Description of drawings

Fig. 1 is an X-ray diffraction diagram of an embodiment of the present invention.

Detailed ways

Below is the embodiment that adopts method of the present invention to prepare calcium magnesium salt.

Example 1:

Take 500ml of deionized water at room temperature, slowly add 2.878mol of glacial acetic acid, then add 0.483mol of CaO and 1.100mol of MgO at one time, and stir to make it react for 1.5hr, the solution is slightly yellow, and the reaction temperature is 45±5℃. Adjust the pH value with a calcium-magnesium mixture with a molar ratio of Ca:Mg=3:7 until the solution shows weak alkaline pH=7.4, centrifuge and filter to separate excess calcium and magnesium oxide after resting. The pH of the mother liquor was measured to be 9.11.

Put the mother liquor into a rotary evaporator and carry out vacuum distillation at a pressure of -0.096 to -0.098MPa and a temperature of 50±5°C. After vacuum distillation for 1.5 hours, a large amount of white crystals precipitated, and the volume of the distillate was measured. The distillate was measured by high-pressure liquid chromatography, and the acetate ion concentration was 2.475×10 ^-3 mol/L, pH=4.60, and the loss rate of acetic acid was 0.01%.

Example 2:

Take 500ml of deionized water at room temperature, slowly add 4.029mol of glacial acetic acid, then add 0.672mol of CaO and 1.34mol of MgO at one time, and stir to make it react for 2 hours. The solution is slightly yellow, and the reaction temperature is 70±5℃. The calcium and magnesium mixture with a molar ratio of Ca:Mg=3:6 is used to adjust the pH value until the solution shows a weakly alkaline pH=8.5. After resting, centrifuge and filter to separate excess calcium and magnesium oxide. The pH of the mother liquor was measured to be 9.56.

Put the mother liquor into a rotary evaporator and carry out vacuum distillation at a pressure of -0.095 to -0.098MPa and a temperature of 75±5°C. After vacuum distillation for 3.5 hours, a large amount of white crystals precipitated, and the volume of the distillate was measured. The distillate was measured by high-pressure liquid chromatography, and the concentration of acetate ion was 3.755×10 ^-3 mol/L, pH=4.16, and the loss rate of acetic acid was 0.012%.

Example 3:

Take 500ml of deionized water at room temperature, add 0.483mol of CaO and 1.100mol of MgO to form a mixed emulsion of calcium oxide and magnesium oxide, slowly add 2.878mol of glacial acetic acid, and stir to make it happen. Control the temperature at 85±5 Between ℃, the required time of complete reaction is about 3 hours, and the obtained mother liquor is similar to Example 1.

The mother liquor was put into a rotary evaporator for vacuum distillation, the pressure was controlled at -0.083 ~ -0.086Mpa, and the rest of the conditions were the same. It was measured that the required temperature for vacuum distillation was 85±5°C, and the required time was 5 hr. The acetate ion concentration in the distillate was 6.635×10 ^-3 mol/L, pH=3.62, and the loss rate of acetic acid was 0.015%.

Claims (2)

1, a kind of method with process for preparing calcium magnesium acetate by vacuum distillation, with Glacial acetic acid or acetum and calcium magnesium oxide or calcium carbonate and magnesium carbonate is raw material, it is characterized in that: calcium, magnesium compound are added in the acetum and mix, the calcium magnesium acetate salts solution of reaction gained concentrates through underpressure distillation, drying gets granular calcium acetate magnesium salt again, and its concrete preparation technology carries out as follows:

(1) acid-base reaction: in reaction tank, add deionized water under the room temperature earlier, slowly add Glacial acetic acid, be made into the solution that concentration is 3mol/L～5mol/L, the calcium magnesium compound that will crush in advance then drops in the reaction tank with stoichiometric ratio, be aided with stirring, the mol ratio of calcium magnesium compound is Ca: Mg=3～4: 6～7, temperature of reaction is controlled at 40 ℃～90 ℃, reaction times is 1 hour～3 hours, adjust pH value in the solution between 7～10, stopped reaction by adding the small amount of calcium magnesium compound at last;

(2) filter: the solution of step (1) preparation is filtered, and liquid phase is carried out underpressure distillation, the recycling of solid phase calcium magnesium oxide;

(3) underpressure distillation: the liquid of step (2) preparation is steamed moisture in the solution under the condition of decompression, the distillation pressure be-0.08MPa～-0.1MPa, distillation temperature is 45 ℃～90 ℃, and distillation time is 1 hour～5 hours, and concentrated calcium acetate magnesium solution reaches white thick crystal and gets final product.

2, according to the described a kind of method of claim 1 with process for preparing calcium magnesium acetate by vacuum distillation, it is characterized in that: step (1) also can take to add earlier under the room temperature deionized water in reaction tank, add CaO then, MgO, be made into calcium oxide, magnesium oxide mixed emulsion, the mol ratio of calcium magnesium compound is Ca: Mg=3～4: 6～7, slowly adds Glacial acetic acid again, its strength of solution is 3mol/L～5mol/L, and stirs the condition that makes it set by step (1) and react.

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