CN111454307A - Preparation method of high-purity tannic acid with different crystal water - Google Patents

Abstract

The invention discloses a method for preparing high-purity tannic acid with different crystal waters. times; drying to obtain a tannic acid solid with a crystal water content in the range of 4 to 9%, the drying temperature is set to -20 to 200°C, and the vacuum degree is set to -0.05 to -0.1 Mpa. By strictly controlling the drying temperature and vacuum degree of the tannic acid, the present invention can obtain high-quality tannic acid solids and tannic acid solids containing different contents of crystal water, which satisfies the requirements of food grade and pharmaceutical grade tannic acid for its purity. high demands.

Description

A kind of preparation method of high-purity different crystal water tannic acid

technical field

The invention belongs to the field of food and medicine, and relates to the research on drying process of tannic acid, in particular to a preparation method of high-purity tannic acid with different crystal waters. The tannic acid solid prepared by the method of the invention can make the residue and quality of the organic solvent meet the national standards of food grade and pharmaceutical grade.

Tannic acid, also known as tannic acid or tannic acid, English name Tannic acid, tannic acid in the form of non-crystalline powder or flakes is light yellow to brown at room temperature, the crystal form and color of tannic acid and purification Craftsmanship is closely related. The main source of tannins is extracted from the bark and fruits of plants, such as Chinese gall, Turkish gall, tara pod, pomegranate, sumac leaves, sumac, witch hazel, etc., which are also generated by these trees being attacked by insects. The main component of the gall (galls), the content of 50 ~ 70%. In addition, more than 70% of Chinese herbal medicines such as Burnet, rhubarb, myrobalan, cinnamon, mango and Agrimony contain a lot of tannins.

Tannins are widely used in medicine, brewing, beverages, tanning, metallurgy, daily chemical industry and other fields, especially high-purity tannins have a large market demand. At present, the domestic tannic acid production technology research focuses on the purification of tannic acid, such as activated carbon adsorption, macroporous resin adsorption, membrane separation technology, ion exchange technology, molecular distillation technology, freezing clarification, solvent extraction and other single purification methods and multiple combination purification. method, but there are few reports on the drying method of tannic acid. The document "Application of Air Flow Spray Drying Device in Tannic Acid Production" discloses a method for spray drying, which can quickly obtain powdered tannic acid, but the disadvantages of this method are high temperature conditions for spray drying, heat-sensitive tannins. The polyhydroxy chemical groups of acids are susceptible to oxidation. Therefore, it is difficult to prepare high-purity tannic acid under conventional conditions, and it is difficult to meet the market demand for high-purity tannic acid products.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is the removal of the residual organic solvent of the tannic acid product, and the preparation of high-purity tannic acid with different crystal waters. In order to solve this technical problem, the present invention provides a preparation method of high-purity tannic acid with different crystal waters. The tannic acid prepared by the method of the invention has stable quality, can effectively remove the residual organic solvent in the purification process of the tannic acid, and reaches the national food grade and pharmaceutical grade standards.

Specifically, a kind of preparation method of high-purity different crystal water tannic acid according to the present invention, it comprises,

Dissolve the tannic acid sample with water as a solvent to form an aqueous tannic acid solution. The amount of water used is 0.5 to 10 times that of the tannic acid sample in terms of mass;

Drying to obtain a tannic acid solid with a crystal water content in the range of 4-9%, the drying temperature is set to -20-200°C, and the vacuum degree is set to -0.05--0.1 Mpa.

As a preferred method for the preparation of the high-purity tannic acid with different crystal waters, when the mass of the dried tannic acid is below 100 g and vacuum drying is adopted, and the drying temperature is between -20 and 60 °C under stirring, the vacuum The degree of drying is -0.08～0.095Mpa, and the drying time is 15-20 hours. When the mass of dried tannic acid is more than 100 g and vacuum drying is adopted, the drying time is appropriately extended, usually more than 20 hours.

As a preferred method for the preparation of the high-purity tannic acid with different crystal waters, after the water in the tannic acid aqueous solution is removed and the tannic acid is in a solid state, the drying temperature is set to 100-200 °C, and the vacuum degree is set to It is -0.05～-0.1Mpa.

As the preferred preparation method of the high-purity tannic acid with different crystal waters, the tannic acid aqueous solution is dried by a gradient heating method, and the gradient heating method is to increase the temperature by 10 °C per hour to obtain tannic acid solids of different crystal forms. and tannin solids with different contents of crystal water.

As a preferred method for the preparation of the high-purity tannic acid with different crystal waters, when the vacuum degree is controlled to be -0.05 to -0.1 Mpa, the drying temperature is set to 65 °C, and stirred for 1 hour; the temperature is lowered to make the tannic acid aqueous solution solidify; Freeze-drying in a freeze-drying machine, the freezing parameter is set to -40～-80 ℃, and the vacuum degree is not higher than -0.09 Mpa; after freeze-drying, the solid is placed in a vacuum drying box, and the vacuum degree is set to -0.085～-0.1 Mpa, the temperature is set to 70-200 °C, and the drying time is controlled to obtain tannic acid solids containing 4-9% crystal water.

Compared with the prior art, the present invention has the advantages or beneficial effects of the method for preparing high-purity tannic acid with different crystal waters.

Most of the tannic acid products prepared by the existing tannic acid production process have residual organic solvents with a boiling point lower than 100 °C, such as ethyl acetate, methyl acetate, acetone, ethanol, petroleum ether, dichloromethane, chloroform, tetrahydrofuran Wait. In order to optimize the drying conditions of the tannic acid product, keep the quality of the tannic acid unchanged before and after drying, and obtain high-purity tannic acid with different contents of crystal water, the present invention provides a preparation of high-purity tannic acid with different crystal waters method. The quality of the tannic acid prepared by the method of the invention is stable, and at the same time, the residual organic solvent in the purification process of the tannic acid can be effectively removed, and the tannic acid can reach the national food-grade and pharmaceutical-grade standards. The method for preparing tannic acid of the present invention has the advantages of simple process, convenient operation and low cost.

The present invention studies the quality (quality) difference of dried tannins under different vacuum degrees and different temperature conditions. First, dissolve an appropriate amount of tannic acid in a certain amount of water (preferably deionized water) (the ratio of the amount of water to the mass of tannic acid is in the range of 0.5:1 to 10:1), and pump it with a water pump or oil pump or other The vacuum instrument is decompressed (the vacuum degree is controlled in the range of -0.05 Mpa ~ -0.1 Mpa), and the tannic acid aqueous solution is heated and stirred until solid tannic acid is obtained. Based on the technical idea of the present invention, the preparation requirements of different percentages of crystal water tannic acid can be achieved by adjusting the heating temperature, drying time and vacuum degree as required.

By adopting the method of the invention, different crystal water tannic acids with water content between 4 and 10% can be prepared, and the organic solvent residues thereof are lower than the national standard (less than 25 mg/Kg).

Detailed ways

Example 1

Take 100 g of tannic acid sample and dissolve it in 1 L of water (preferably deionized water) to form an aqueous tannic acid solution, then heat it to 80 °C, reduce the pressure to -0.09 Mpa with an oil pump, and stir, about 0.5 L to 0.7 When L water is removed, stop stirring until the tannic acid aqueous solution becomes solid, then continue to dry under vacuum (-0.09 Mpa vacuum degree) at 80 °C for 4 hours to obtain a tannic acid solid with a water content of 6%. After cooling to room temperature , take out the tannic acid solid, crush the tannic acid solid with a pulverizer, and screen with different mesh sieves to obtain tannic acid with different mesh numbers.

Example 2

Dissolve 100 g of tannic acid in 0.5 L of water to form a tannic acid aqueous solution, then heat it to 40 °C, and use an oil pump to reduce the pressure to -0.09 Mpa to -0.095 Mpa. When about 0.4 L of water is removed, stop stirring. After the tannic acid aqueous solution becomes solid, increase the vacuum temperature to 80 °C and vacuum (-0.09 Mpa vacuum degree) for 4 hours, then increase the vacuum temperature to 110 °C for 2 hours to obtain tannins with a water content of 5% Acid solid, after cooling to room temperature, take out the solid, pulverize the solid tannic acid with a pulverizer, and screen with different mesh sieves to obtain tannic acid with different mesh numbers.

Example 3

Dissolve 100 g of tannic acid in 0.3 L of water to form a tannic acid aqueous solution, then heat it to between 60 and 65 °C, use an oil pump to reduce the pressure to -0.08 Mpa to -0.095 Mpa, and stir until the tannic acid aqueous solution becomes After forming a solid, increase the vacuum temperature to 80 °C and vacuum (-0.095 Mpa vacuum degree) for 4 hours, then increase the vacuum temperature to 110 °C and keep it for 2 hours to obtain a tannic acid solid with a water content of 5%, which is cooled to room temperature Then, the solid is taken out, and the solid tannic acid is pulverized with a pulverizer, and sieved with sieves of different mesh numbers to obtain tannins of different mesh numbers.

Example 4

Dissolve 100 g of tannic acid in 0.3 L of water to form a tannic acid aqueous solution, then heat it to between 60 and 65 °C, use an oil pump to reduce the pressure to -0.08 Mpa to -0.095 Mpa, and stir until the tannic acid aqueous solution becomes After becoming solid, vacuum (-0.09Mpa vacuum degree) drying for 4 hours to obtain the tannic acid solid with water content of 9%, after cooling to room temperature, take out the solid, pulverize the solid tannic acid with a pulverizer, screen with different mesh sieves, Tannins of different mesh numbers were obtained.

Example 5

Dissolve 100 g of tannic acid in 0.3 L of water to form an aqueous solution of tannic acid, then heat it to between 60 and 65 °C (gradient heating is used, and the gradient heating method is 10 °C per hour), and the pressure is reduced to - Between 0.08 Mpa and -0.095 Mpa, after stirring the tannic acid aqueous solution for 0.5 hours, the temperature is lowered to freeze the tannic acid aqueous solution into a solid, and then transferred to a freeze dryer for freeze drying, the temperature is -80 ℃, and the vacuum degree is -0.092 Mpa , until the water is completely drained, take out the solid to obtain a tannic acid solid with a water content of 9%, pulverize the solid tannic acid with a pulverizer, and screen with different mesh sieves to obtain different mesh tannic acid.

Example 6

Dissolve 100 g of tannic acid in 0.3 L of water to form an aqueous tannic acid solution, then heat it to 60-65 °C, use an oil pump to reduce pressure to the range of -0.08 Mpa to -0.095 Mpa, and stir the aqueous tannic acid solution for 0.5 After an hour, the temperature was lowered to freeze the tannic acid aqueous solution into a solid block, and then transferred to a freeze dryer for freeze drying, the temperature was -80 °C, and the vacuum degree was -0.092 Mpa, until the water was completely drained, and the solid was taken out to obtain a The tannic acid solid with a water content of 9%; then put into a vacuum drying box, the vacuum degree is kept in the range of -0.085 Mpa～-0.095 Mpa, then heated to 110 ° C, kept for 4 hours, and the solid was taken out to obtain a water content of 6% The solid tannins are crushed with a pulverizer and screened with different mesh sieves to obtain tannins with different mesh numbers.

Example 7

Dissolve 100 g of tannic acid in 0.3 L of water to form a tannic acid aqueous solution, then heat it to 60-65 °C, stir the tannic acid aqueous solution for 0.1 hour, cool down to freeze the tannic acid aqueous solution into a block, and then transfer Freeze-dry in a freeze dryer, the temperature is -80 °C, and the vacuum degree is -0.092 Mpa, until the water is completely drained, and the solid is taken out to obtain a tannic acid solid with a water content of 9%; then put into a vacuum drying box, The vacuum degree is kept in the range of -0.085 Mpa～-0.095 Mpa, then heated to 110 ℃ and kept for 4 hours, and the solid is taken out to obtain a tannic acid solid with a water content of 6%. The ethyl ester residue of 1000mg/Kg is far greater than the national standard.

Example 8

In this method, the residual determination of ethyl acetate is taken as an example to verify the purity of the tannic acid prepared by the present invention. The standard solutions used are ethyl acetate standard solution (1#) and n-butanol standard solution (2#).

The chromatographic data of the standard solution are as follows.

The calibration factor f _i is calculated according to the formula:

where:

A _s - the peak area value of n-butanol (internal standard) in the chromatogram of the standard solution;

c _s — the concentration of n-butanol (internal standard) in the standard solution, in milligrams per milliliter (mg/mL);

A _r —the peak area value of the ethyl acetate standard in the standard solution chromatogram;

cr _- the concentration of the ethyl acetate standard in the standard solution, in milligrams per milliliter (mg/mL).

The sample weight of the n-butanol standard product is 0.1014 g, the sample weight of the ethyl acetate standard product is 0.1033 g, and the sample weight of the tannic acid sample prepared by the method described in Example 1 is 1.0024 g; Example 7, 3#) A tannic acid sample was prepared and the sample amount was 1.0015 g.

The concentration of n-butanol is 0.1014/100*5/100*1000=0.0507 mg/mL,

Ethyl acetate concentration is 0.1033/100*0.1/25*1000=0.004132 mg/mL,

Calibration factor f _i = (112.36454/0.0507)/(66.46095/0.004132)=0.1378.

The chromatographic data of the sample solution are as follows.

The content w ₃ of the residual solvent (ethyl acetate) of the tannic acid sample prepared by the method described in Example 1, in milligrams per kilogram (mg/kg), is calculated as follows:

where:

A —the peak area value of ethyl acetate in the sample solution chromatogram;

m _i - the mass of n-butanol (internal standard) in the sample solution, in milligrams (mg);

f _i —calibration factor;

A _i - the peak area value of n-butanol (internal standard) in the chromatogram of the sample solution;

m - the mass of the sample, in grams (g).

Calculation of ethyl acetate content: w ₃ =23.35189*(5*0.0507)*0.1378/(79.96697*1.0024)=10.1765 mg/kg≤25 mg/kg. It can be seen that the ethyl acetate residue of the tannic acid sample prepared by the method described in Example 1 is 10.1765 mg/kg, which is lower than the national standard of 25 mg/kg. From the peak area ratio (Example 7) in the above table, it can be seen that the method without reduced pressure, the residual amount of ethyl acetate in the tannic acid is 100 times that under reduced pressure, far exceeding the national standard.

Claims (5)

1. A method for preparing tannic acid with different crystal water in high purity is characterized by comprising the following steps,

dissolving a tannic acid sample by using water as a solvent to form a tannic acid aqueous solution, wherein the amount of the water is 0.5-10 times of that of the tannic acid sample by mass;

drying to obtain the tannic acid solid with the crystal water content of 4-9%, wherein the drying temperature is set to-20-200 ℃, and the vacuum degree is set to-0.05-0.1 Mpa.

2. The method of preparing tannic acid of different crystal waters in high purity according to claim 1, wherein the drying time is 15 to 20 hours, and the drying temperature is-20 to 60 ℃ under agitation, the degree of vacuum is-0.08 to 0.095Mpa, and the mass of the dried aqueous tannic acid solution is 100 g or less.

3. The method of preparing tannic acid of different crystal waters of high purity according to claim 1, wherein the drying temperature is set to 100 to 200 ℃ and the degree of vacuum is set to-0.05 to-0.1 Mpa after water in the aqueous solution of tannic acid is removed and tannic acid is in a solid form.

4. The method of claim 1, wherein the aqueous solution of tannic acid is dried by gradient heating at 10 ℃ per hour to obtain tannic acid solids of different crystal forms and tannic acid solids of different crystal water contents.

5. The method of preparing tannic acid of different crystal waters of high purity as claimed in claim 1, wherein the drying temperature is set to 65 ℃ and stirring is carried out for 1 hour while controlling the degree of vacuum to-0.05 to-0.1 Mpa; cooling to solidify the tannic acid aqueous solution; freeze drying in a freeze drier with freezing parameter set at-40-80 deg.c and vacuum degree not higher than-0.09 MPa; after freeze drying, putting the mixture into a vacuum drying oven, setting the vacuum degree to be-0.085 to-0.1 Mpa and the temperature to be 70 to 200 ℃, and obtaining the tannic acid solid containing 4 to 9 percent of crystal water.