CN-116554020-B - Purification method of analytically pure salicylic acid

Abstract

The invention discloses a purification method of analytically pure salicylic acid, which comprises the following steps of adding salicylic acid, deionized water and active carbon into an autoclave, then introducing inert gas, stirring and dissolving under the conditions of pressurization and heating, filtering to remove the active carbon, introducing the obtained filtrate into a crystallizer for crystallization, and finally centrifugally dehydrating, and transferring the obtained salicylic acid wet crystal into a dryer for drying to obtain the analytically pure salicylic acid. According to the invention, the salicylic acid is dissolved under the condition of pressurization, so that the dissolution speed and the dissolution sufficiency of the salicylic acid in water are effectively improved, an excellent purification effect can be achieved through one-time recrystallization, and the salicylic acid purified by the method disclosed by the invention is high in purity, good in quality and high in yield, and is high-quality analytically pure salicylic acid.

Inventors

• DAI HUIMING
• ZHANG LUJIA

Assignees

• 永华化学股份有限公司

Dates

Publication Date

20260508

Application Date

20230426

Claims (7)

1. 1. A method for purifying analytically pure salicylic acid, comprising the steps of: Adding salicylic acid, deionized water and active carbon into an autoclave, then introducing inert gas, stirring and dissolving under the conditions of pressurization and heating, wherein the pressurization pressure is 3-6 MPa, the heating temperature is 85-100 ℃, filtering to remove the active carbon, introducing the obtained filtrate into a crystallizer for crystallization, and finally centrifugally dehydrating, and transferring the obtained salicylic acid wet crystals into a dryer for drying to obtain the analytically pure salicylic acid.
2. 2. The method for purifying analytically pure salicylic acid according to claim 1, wherein the crystallization process conditions are that the temperature is 5-25 ℃, the stirring speed is 15-30 r/min, and the time is 120-180 min.
3. 3. The method for purifying analytically pure salicylic acid according to claim 1, wherein the drying process conditions are vacuum low-temperature drying, drying for 1-2 hours at 30-50 ℃ and then heating to 50-80 ℃ and drying for 2-5 hours.
4. 4. A method for purifying analytically pure salicylic acid according to claim 1 wherein the filtration is carried out by opening the outlet at the bottom of the autoclave and discharging the dissolved solution together with the activated carbon by the pressure in the autoclave.
5. 5. The method for purifying analytically pure salicylic acid according to claim 4, wherein the outlet of the autoclave is connected to the inlet of the crystallizer via a pipe, and a filter is installed on the pipe between the autoclave and the crystallizer.
6. 6. The method of purifying analytically pure salicylic acid according to claim 1, wherein the salicylic acid is technical grade salicylic acid.
7. 7. The method for purifying analytically pure salicylic acid according to claim 6, wherein the ratio of the mass of salicylic acid to the volume of deionized water is 1 g:5-10 ml.

Description

Purification method of analytically pure salicylic acid Technical Field The invention relates to the technical field of chemical purification, in particular to a purification method of analytically pure salicylic acid. Background Salicylic acid (SALICYLIC ACID) is also called 2-hydroxybenzoic acid, the molecular formula is C 7H6O3, and belongs to a fat-soluble organic acid. Salicylic acid is a toxic white needle-like crystal or monoclinic crystal, has special phenolic acid taste, is easily dissolved in diethyl ether, ethanol and propanol, and is slightly dissolved in cold water. Salicylic acid is an important chemical raw material and is widely applied to the fields of medicines, cosmetics, pesticides and the like. The purity requirement of the analytically pure salicylic acid is more than or equal to 99.5 percent. The existing salicylic acid purification method mostly adopts a recrystallization method, and the total yield is not high because the solubility of salicylic acid in water is not high. If high quality salicylic acid is to be obtained, multiple recrystallisation may be required, which may result in lower yields. Currently, the industry lacks efficient purification methods for salicylic acid. Disclosure of Invention The present invention solves the above-mentioned problems associated with prior art salicylic acid purification by providing a method for purifying analytically pure salicylic acid. In order to solve the technical problems, the invention provides a purification method of analytically pure salicylic acid, which comprises the following steps: adding industrial grade salicylic acid, deionized water and active carbon into an autoclave, then introducing inert gas, stirring and dissolving under the conditions of pressurization and heating, filtering to remove the active carbon, introducing the obtained filtrate into a crystallizer for crystallization, and finally centrifugally dehydrating, and transferring the obtained salicylic acid wet crystals into a dryer for drying to obtain the analytically pure salicylic acid. In a preferred embodiment of the present invention, the pressurizing pressure is 1 to 10mpa, preferably 3 to 6mpa. In a preferred embodiment of the present invention, the heating temperature is 85-100 ℃. In a preferred embodiment of the invention, the crystallization process conditions are that the temperature is 5-25 ℃, the stirring speed is 15-30 r/min, and the time is 120-180 min. In a preferred embodiment of the invention, the drying process conditions are that vacuum low-temperature drying is carried out, the drying is carried out for 1-2 hours at 30-50 ℃, and then the drying is carried out for 2-5 hours at 50-80 ℃. In a preferred embodiment of the invention, the filtration is carried out by opening a discharge port in the bottom of the autoclave and discharging the dissolved solution together with the activated carbon by means of the pressure in the autoclave. In a preferred embodiment of the invention, the discharge port of the autoclave is connected with the feed port of the crystallizer by a pipe, and a filter is arranged on the pipe between the autoclave and the crystallizer. In a preferred embodiment of the present invention, the volume ratio of the mass of the salicylic acid to the deionized water is 1 g:5-10 ml. The method for purifying the analytically pure salicylic acid has the beneficial effects that the salicylic acid is dissolved under the condition of pressurization, so that the dissolution speed and the dissolution sufficiency of the salicylic acid in water are effectively improved, an excellent purification effect can be achieved through one-time recrystallization, and the salicylic acid purified by the method is high in purity, good in quality and high in yield, and is high-quality analytically pure salicylic acid. Drawings FIG. 1 is a schematic diagram of equipment used in a method of purifying analytically pure salicylic acid according to the invention; the components in the drawings are marked as follows, 1. Autoclave, 2. Piping, 3. Crystallizer, 4, filter. Detailed Description The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making clear and defining the scope of the present invention. Referring to fig. 1, an embodiment of the present invention includes: The invention relates to a method for preparing analytically pure salicylic acid by high-pressure purification, which improves the solubility of salicylic acid in deionized water serving as a solvent under high-pressure conditions, so that the salicylic acid is promoted to be rapidly and fully dissolved in the deionized water, and then the salicylic acid is purified by recrystallization, thereby being beneficial to improving the recrystallization effect of the salicylic acid, and further improving t