CN109821269B - Method for separating high-freezing-point substances from mixture containing different freezing-point substances in high purity - Google Patents

Abstract

A method for separating high freezing point substances from a mixture containing different freezing point substances in high purity comprises the following steps: providing a mixture to be separated, wherein the mixture to be separated is a homogeneous mixture, and the mixture to be separated contains at least two substances; providing a dispersing agent which enables the condensation point of the low condensation point substance in the mixture to be separated to be reduced but does not affect the condensation point of the high condensation point substance, or the reduction degree of the condensation point of the high condensation point substance relative to the low condensation point substance is smaller than that of the low condensation point substance; uniformly distributing a dispersing agent into a mixture to be separated, then carrying out first cooling to crystallize a first high-condensation-point substance with the highest condensation point of the separated mixture, and then finishing extraction of the first high-condensation-point substance through solid-liquid separation. The application makes it possible to lower the freezing point of substances with a low freezing point in the mixture to be separated by dispersing the dispersant into the mixture to be separated, so that the difference in freezing point between the freezing point and the first substance with a high freezing point becomes large.

Description

Method for separating high-freezing-point substances from mixture containing different freezing-point substances in high purity

Technical Field

The present application relates to a process for the high purity separation of high freezing point substances from a mixture containing substances of different freezing points.

Background

The purification and separation of substances are the basis of substance application, so that a great number of means exist for the purification and separation process. The separation and purification method is always perfected along two different directions. One is to investigate the direction of how to obtain high purity materials. For example, how to obtain high purity silicon with purity as high as 99.9999% or more. And the other is how to apply the economic separation and purification method to large-scale industrial production. For example, titanium dioxide (titanium dioxide) is a very common white pigment used in the industrial production of enamels and cosmetics. Because of the symbiosis of iron ore and titanium ore, the prepared titanium dioxide is often mixed with iron and is yellowed when used as a pigment or a cosmetic filler. The iron removing method is not difficult in a laboratory, but has complex process and more technical problems in industrial production, so that the price of the primary product titanium dioxide which does not contain iron basically is far from that of the secondary product titanium dioxide which contains a small amount of iron. Therefore, how to remove iron in titanium dioxide by using a simple method is always a critical item for technical personnel in pigment factories. Some places have the phenomenon of secondary titanium dioxide expansion (excessive stock and difficult sale), while primary products only depend on import. If the second-grade product can be improved into the first-grade product, the market demand can be met, the import can be reduced, and even the export of export sales is organized. Common separation methods are: crystallization and recrystallization; distillation cooling method; a filtration method; a sublimation method; an extraction method; dissolution method, and the like.

In order to separate substances with different melting points or boiling points, methods such as rectification, crystallization and the like can be adopted, but no matter which method is adopted, it is always difficult to separate substances with approximate properties, even phenomena such as azeotropy, eutectic and the like.

CN105112090A discloses an oil wax dispersant, a preparation method thereof and an oil wax separation method, wherein the oil wax dispersant comprises the following components by taking the total mass of the oil wax dispersant as 100 percent: 1 to 2 percent of ethylene-vinyl acetate copolymer, 2 to 5 percent of dichloroethane, 0.5 to 1 percent of polyacrylate and the balance of light oil. The preparation method of the oil wax dispersant comprises the following steps: mixing and stirring the ethylene-vinyl acetate copolymer, dichloroethane, polyacrylate and light oil for 30-60 min at 50 ℃ and normal pressure to obtain the oil wax dispersant. The oil wax separation method provided by the invention comprises the step of sending the oil wax dispersing agent and the oil wax to be separated into a two-phase horizontal screw centrifuge for separation. The oil wax dispersing agent and the oil wax separation method provided by the invention can effectively separate the oil wax. In this application, there are mainly two problems: 1. the addition amount of the separating agent is too large; 2. the added materials may accumulate in the oil or wax liquid, thereby introducing the oil wax dispersant itself into the overall system as an impurity, thereby making such oil wax dispersants unsuitable for the separation of high purity demanding materials.

Content of application

In order to solve the problems, the application provides a method for separating high-freezing-point substances from a mixture containing different freezing-point substances in high purity, which comprises the following steps:

providing a mixture to be separated, wherein the mixture to be separated is a homogeneous mixture, and the mixture to be separated contains at least two substances;

providing a dispersing agent which enables the condensation point of the low condensation point substance in the mixture to be separated to be reduced but does not affect the condensation point of the high condensation point substance, or the reduction degree of the condensation point of the high condensation point substance relative to the low condensation point substance is smaller than that of the low condensation point substance;

uniformly distributing a dispersing agent into a mixture to be separated, then carrying out first cooling to crystallize a first high-condensation-point substance with the highest condensation point of the separated mixture, and then finishing extraction of the first high-condensation-point substance through solid-liquid separation. The dispersant enables the high condensation point substance and the low condensation point substance to be better separated through different actions with the low condensation point substance and the high condensation point substance. Specifically, the dispersant allows the freezing point of the low freezing point substance in the mixture to be separated to be lowered by dispersing the dispersant in the mixture to be separated, so that the difference in freezing point between the freezing point and the first high freezing point substance becomes large, and therefore, when the first condensation is performed at a later stage so that the temperature is lower than the freezing point of the first high freezing point substance, the first high freezing point substance is separated in advance by crystallization in a supercooled state, and since the first high freezing point substance has a high difference in freezing point with other substances, impurities are not introduced, but the first high freezing point substance is capable of self-crystallizing.

Preferably, the first high freezing point substance contains a trace amount of dispersant. In the present application, the trace amount criterion is less than 0.01%, and the object is easily achieved when the amount of the dispersant is very small, but when the amount of the dispersant is very small, the separation between the freezing points is not very obvious, so that in some mixtures to be separated with close freezing points, a larger amount of the dispersant must be added, for example, when 5000ppm, that is, 0.5 wt%, is reached, because the amount of the dispersant added is larger, the difference of the freezing points between the first high-freezing-point substance and other substances can be more greatly opened, thereby facilitating the first high-freezing-point substance to obtain pure crystals without the dispersant under a proper condition.

Preferably, the mass percentage of the impurities in the first high freezing point substance is not higher than 10%. Impurities here refer to substances other than the first high freezing point substance in the mixture to be separated.

Preferably, the solid-liquid separation mode is centrifugal separation or filter-pressing separation.

Preferably, the method comprises the process of separating the mixture to be separated from which the first high-condensation-point substance is separated, and then sequentially carrying out the steps of uniformly distributing the dispersing agent, carrying out second cooling to obtain a second high-condensation-point substance and carrying out solid-liquid steps to obtain the second high-condensation-point substance. Essentially, the process of repeated addition of dispersant for repeated separation. If a mixture of stearic acid, oleic acid and linoleic acid is separated, the stearic acid can be separated by condensation, and then the oleic acid can be separated by condensation.

Preferably, the dispersant is one or a mixture of more than two of alkyl naphthalene, polyether, poly alpha olefin, polyethylene-vinyl acetate acid, polymethacrylate and polyethylene-fumaric acid copolymer in any proportion.

Preferably, the mass concentration of the dispersant in the mixture to be separated is 1 to 5000 ppm.

Preferably, the dispersing agent is uniformly distributed in the mixture to be separated by heating the mixture to be separated to a temperature higher than the solidifying point by 10-50 ℃, and then adding the dispersing agent and stirring. The substrate is in a liquid state, so that the dispersing agent is mixed in the liquid state, and the dispersing agent can be basically mixed into the mixture to be separated in a molecular state.

Preferably, the mixture to be separated is diesel containing wax, which is the first high freezing point material.

Preferably, the mixture to be separated is fatty acid, and the stearic acid is a first high freezing point substance.

This application can bring following beneficial effect:

1. the dispersant can reduce the freezing point of the substances with low freezing points in the mixture to be separated by dispersing into the mixture to be separated, so that the difference between the freezing point of the substances with low freezing points and the freezing point of the substances with high freezing points is increased, and therefore, the first substance with high freezing points is separated in advance due to crystallization when the temperature is lower than the freezing point of the first substance with high freezing points in a supercooled state, and impurities cannot be introduced due to the higher difference between the freezing point of the first substance with high freezing points and other substances, but the first substance with high freezing points can be crystallized by itself;

2. Because trace amount of the dispersant in the high freezing point substance can be conveniently left in the high freezing point substance by pulling the freezing point between the high freezing point substance and other substances, the aim is easy to realize when the addition amount of the dispersant is very small, but the separation between the freezing points is not very obvious when the addition amount of the dispersant is very small, so that in some mixtures to be separated with close freezing points, a larger amount of the dispersant must be added, for example, when the addition amount reaches 5000ppm, namely 0.5 wt%, the difference between the freezing points of the first high freezing point substance and other substances can be pulled open to a larger extent due to the larger addition amount of the dispersant, and therefore, the first high freezing point substance can conveniently obtain pure crystals without the dispersant under a proper condition;

3. the separation of the high freezing point materials can be achieved gradually by continuing the addition of the dispersant, but if the overall addition is too large or if the materials to be separated have substantially the same freezing point or even if a co-coagulating mixture is produced, the separation cannot be continued.

Detailed Description

In order to clearly explain the technical features of the present solution, the present application will be explained in detail through the specific embodiments below.

The embodiment is as follows:

in this embodiment, the method comprises the following steps:

s1, taking a mixture to be separated, wherein the mixture to be separated consists of a first high-condensation-point substance and other substances, the mass fraction of the first high-condensation-point substance in the mixture to be separated is recorded as a first mass fraction, and a first temperature is obtained by heating at first and is higher than the solidification temperature of the mixture to be separated;

s2, adding a dispersing agent, wherein the adding amount is calculated according to the mass of the mixture to be separated, and the adding amount is recorded as the mass concentration of the dispersing agent;

s3, cooling the product obtained in the step S2 to a second temperature;

s4, performing centrifugal separation on the product obtained in the step S3;

and S5, detecting the content of the dispersant and the content of impurities in the solid obtained in the S4.

TABLE 1 test conditions

TABLE 1 continuation of the table

It can be seen from the above table that by adding smaller amounts of dispersants of the above type to different substances, a substantially higher degree of purification of the high freezing point substance can be achieved, the dispersant content as well as the impurity content of the purified high freezing point substance being at a lower level.

The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for the system embodiment, since it is substantially similar to the method embodiment, the description is simple, and for the relevant points, reference may be made to the partial description of the method embodiment.

The above description is only an example of the present application and is not intended to limit the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims (4)

1. A method for separating high freezing point substances from a mixture containing different freezing point substances in high purity, which is characterized by comprising the following steps: the method comprises the following steps:

providing a mixture to be separated, wherein the mixture to be separated is a homogeneous mixture, the mixture to be separated comprises at least two substances, the two substances are a first high condensation point substance and other substances, the first high condensation point substance is oleic acid, and the other substances are linoleic acid;

providing a dispersing agent, wherein the dispersing agent is polymethacrylate;

uniformly distributing a dispersing agent into a mixture to be separated, carrying out first cooling to crystallize a first high-condensation-point substance with the highest condensation point of the separated mixture, and then completing extraction of the first high-condensation-point substance through solid-liquid separation;

the first high condensation point substance contains a trace amount of dispersant;

The mass percentage of impurities in the first high freezing point substance is not higher than 10%.

2. The method of claim 1 for separating high freezing point substances from a mixture containing different freezing point substances, wherein the method comprises the following steps: the solid-liquid separation mode is centrifugal separation or filter pressing separation.

3. The method of claim 1 for separating high freezing point substances from a mixture containing different freezing point substances, wherein the method comprises the following steps: the mass concentration of the dispersing agent in the mixture to be separated is 1-5000 ppm.

4. The method of claim 1 for separating high freezing point substances from a mixture containing different freezing point substances, wherein the method comprises the following steps: the uniform distribution of the dispersing agent in the mixture to be separated is carried out by heating the mixture to be separated to a temperature higher than the solidifying point by 10-50 ℃, then adding the dispersing agent and stirring.