Process for the isolation of 2-alkylanthraquinones, and 2-alkylanthraquinone products produced by the isolation process and their use

Abstract

The present application relates to the technical field of separation, in particular to a separation method of 2-alkylanthraquinone, a 2-alkylanthraquinone product prepared by the separation method and application thereof. The separation method comprises the following steps: (1) distilling 2-alkylanthra oxidation reaction liquid to obtain water and a solid-liquid mixture with a water content of 1-5 wt%; performing first filtration on the solid-liquid mixture to obtain a solid mixture rich in hydrophilic impurities and a liquid mixture containing 2-alkylanthracene, 2-alkylanthraquinone and oleophilic impurities; (2) performing crystallization on the liquid mixture as a crystallization liquid to obtain 2-alkylanthraquinone crystals; (3) performing purification on the 2-alkylanthraquinone crystals to obtain a 2-alkylanthraquinone product. The separation method can obtain a 2-alkylanthraquinone product with high purity, the method significantly reduces the energy consumption and operation difficulty of the separation process, and is convenient for industrial production.

Description

Technical Field

[0001] This invention relates to the field of separation technology, specifically to a method for separating 2-alkylanthraquinone, a 2-alkylanthraquinone product obtained by the separation method, and its applications. Background Technology

[0002] Hydrogen peroxide is an important green basic chemical with a wide range of industrial applications. my country has been the world's largest producer of hydrogen peroxide for over a decade, with a domestic production capacity of approximately 15 million tons per year in 2020 (based on 27.5 wt%). Currently, commercial hydrogen peroxide production both domestically and internationally mainly relies on the anthraquinone process, which accounts for 95% of global production and 98% of domestic production. The phthalic anhydride process is the primary method for producing 2-alkylanthraquinone, the main component of the anthraquinone working solution, but this process suffers from serious pollution problems. Producing 1 ton of 2-ethylanthraquinone requires 1.76 tons of anhydrous AlCl3 and 4.2 tons of fuming sulfuric acid, both of which are difficult to recover. Therefore, from the perspective of environmental protection and clean production, developing a green production process for 2-alkylanthraquinone is crucial.

[0003] The process of preparing 2-alkylanthraquinone by alkylating anthracene to 2-alkylanthraquinone is considered a green production technology with broad application prospects due to its advantages such as simple process flow, wide availability of raw materials, and low environmental pollution. 2-alkylanthraquinone, as a "carrier" for recycling in the hydrogen peroxide production process, requires high purity, especially the removal of trace impurities that affect hydrogenation and oxidation efficiency and long-term cycle stability. For the oxidation reaction system, firstly, due to the limitations of the catalytic activity, selectivity, and separation difficulties of the preceding alkylation reaction, the purity of the 2-alkylanthraquinone feedstock is often low, introducing some difficult-to-remove, widely distributed heteroatoms, pigments, organic acids, soluble salts, and other impurities into the reaction system; secondly, the addition of reaction solvents and oxidation catalysts, as well as their poor stability, also increase the separation difficulty; simultaneously, the oxidation reaction still presents problems with catalytic activity and side reactions. Therefore, the separation and purification of 2-alkylanthraquinone products in such a complex system requires the development of specialized and efficient separation technologies.

[0004] CN111825544A, CN111825540A and US3953482 all disclose oxidation methods for preparing the corresponding anthraquinones from anthracene or 2-alkylanthracene, but none of them provide a method for purifying 2-alkylanthraquinones from the oxidation reaction products.

[0005] CN107162889A discloses a method for preparing and purifying 2-tert-pentylanthraquinone based on 2-(4'-tert-pentylbenzoyl)benzoic acid (ABB acid), but the separation method is limited to this reaction system; CN106365970A discloses a method for separating and purifying 2-tert-pentylanthraquinone from a mixture of ABB acid and 2-tert-pentylanthraquinone, with a purity >95wt%; CN110511130A discloses a method for purifying 2-tert-pentylanthraquinone from a mixture of 2-secondary-pentylanthraquinone and 2-tert-pentylanthraquinone, obtaining 2-tert-pentylanthraquinone with a purity ≥99wt%. In other words, the prior art only discloses methods for separating 2-tert-pentylanthraquinone from binary components containing 2-tert-pentylanthraquinone, and does not involve methods for directly post-processing 2-alkylanthraquinone products from oxidation reaction solutions. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of existing methods for separating 2-alkylanthraquinone, such as the inability to directly separate 2-alkylanthraquinone from the 2-alkylanthraquinone oxidation reaction solution, low separation efficiency and low purity, and complex process flow. This invention provides a new method for separating 2-alkylanthraquinone, a 2-alkylanthraquinone product obtained by this method, and its applications. This method efficiently removes impurities from the 2-alkylanthraquinone oxidation reaction solution, yielding a high-purity 2-alkylanthraquinone product.

[0007] To achieve the above objective, the first aspect of the present invention provides a method for separating 2-alkylanthraquinone, the separation method comprising the following steps:

[0008] (1) The 2-alkylanthracene oxidation reaction solution is distilled to obtain water and a solid-liquid mixture with a water content of 1-5 wt%; the solid-liquid mixture is first filtered to obtain a solid mixture rich in hydrophilic impurities and a liquid mixture containing 2-alkylanthracene, 2-alkylanthraquinone and lipophilic impurities;

[0009] (2) The liquid mixture was used as a crystallizing liquid to crystallize and obtain 2-alkylanthraquinone crystals;

[0010] (3) The 2-alkylanthraquinone crystals are purified to obtain the 2-alkylanthraquinone product.

[0011] Preferably, the 2-alkylanthraquinone oxidation reaction solution comprises: 2-alkylanthracene, 2-alkylanthraquinone, water, hydrophilic impurities, and lipophilic impurities.

[0012] The second aspect of the present invention provides a 2-alkylanthraquinone product obtained by the separation method provided in the first aspect.

[0013] The third aspect of this invention provides the application of the 2-alkylanthraquinone product provided in the second aspect in the preparation of hydrogen peroxide.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] (1) The method provided by the present invention uses a complex 2-alkylanthraquinone oxidation reaction solution as raw material and employs distillation, crystallization and purification techniques to effectively remove water, hydrophilic impurities and lipophilic impurities from the 2-alkylanthraquinone oxidation reaction solution to obtain a high-purity 2-alkylanthraquinone product, namely, the 2-alkylanthraquinone content in the 2-alkylanthraquinone product is ≥98.5wt%, the heteroatom content is ≤20ppm, and the total metal content is ≤20ppm; at the same time, the method significantly reduces the energy consumption and operational difficulty of the separation process, and is convenient for industrial production;

[0016] (2) The 2-alkylanthraquinone product prepared by the method provided by the present invention has good single impurity indicators and can be used as a standard of 2-alkylanthraquinone. At the same time, it is used in the study of hydrogen peroxide preparation experiments, which solves the problem of impurities affecting hydrogenation and oxidation efficiency and long-term cycle stability. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the process for separating 2-alkylanthraquinone provided by the present invention. Detailed Implementation

[0018] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0019] In this invention, unless otherwise specified, "first," "second," and "third" do not indicate a sequence or limit the specific materials or steps; they are merely used to distinguish or indicate that these are not the same material or step. For example, in "first filtration," "second filtration," and "third filtration," "first," "second," and "third" are used only to indicate that these are not the same filtration process.

[0020] The first aspect of this invention provides a method for separating 2-alkylanthraquinone, the method comprising the following steps:

[0021] (1) The 2-alkylanthracene oxidation reaction solution is distilled to obtain water and a solid-liquid mixture with a water content of 1-5 wt%; the solid-liquid mixture is first filtered to obtain a solid mixture rich in hydrophilic impurities and a liquid mixture containing 2-alkylanthracene, 2-alkylanthraquinone and lipophilic impurities;

[0022] (2) The liquid mixture was used as a crystallizing liquid to crystallize and obtain 2-alkylanthraquinone crystals;

[0023] (3) The 2-alkylanthraquinone crystals are purified to obtain the 2-alkylanthraquinone product.

[0024] According to the present invention, unless otherwise specified, the impurities in the 2-alkylanthracene oxidation reaction solution include impurities introduced from the reaction raw materials and impurities from side reactions. Specifically, impurities introduced from the raw materials include heteroatoms such as P, Si, N, S, and Cl introduced from the crude 2-alkylanthracene and the solvent; organic acids such as methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, butanesulfonic acid, perfluoromethanesulfonic acid, perfluoroethanesulfonic acid, perfluoropropanesulfonic acid, and perfluorobutanesulfonic acid, and their oxidation or decomposition products; and Cu. 2+ Fe 3+ It includes non-ferrous metal ion impurities, other anthracene substances, etc.; it also includes soluble compounds and decomposition products of one or more metals from Group IB, Group IVB, Group VB, Group VIIB and Group VIII introduced by oxidation catalysts; side reaction impurities include alkane oxides, aromatic oxides, phthalic anhydrides, other anthraquinone substances, etc.

[0025] In this invention, unless otherwise specified, the hydrophilic impurities in the 2-alkylanthracene oxidation reaction solution include some heteroatoms such as P, Si, N, S, and Cl, sulfonic acid organic acids and their oxidation or decomposition products, and Cu. 2+ Fe 3+ The main impurities are non-ferrous metal ions, soluble compounds of various metals introduced by the catalyst and their decomposition products; the rest are mainly lipophilic impurities.

[0026] In some embodiments of the present invention, preferably, the 2-alkylanthraquinone oxidation reaction solution comprises: 2-alkylanthracene, 2-alkylanthraquinone, water, hydrophilic impurities, and lipophilic impurities.

[0027] In some embodiments of the present invention, preferably, based on the total weight of the 2-alkylanthraquinone oxidation reaction solution, the content of the 2-alkylanthracene is 0.1-6 wt%, the content of the 2-alkylanthraquinone is 3-25 wt%, the content of water is 5-40 wt%, the content of the hydrophilic impurity is 0.1-35 wt%, and the content of the lipophilic impurity is 0.1-10 wt%; more preferably, the content of the 2-alkylanthracene is 0.1-3 wt%, the content of the 2-alkylanthraquinone is 5-15 wt%, the content of water is 20-30 wt%, the content of the hydrophilic impurity is 0.5-10 wt%, and the content of the lipophilic impurity is 0.5-5 wt%.

[0028] In some embodiments of the present invention, preferably, the 2-alkylanthracene is selected from at least one of 2-butylanthracene, 2-pentylanthracene and 2-hexylanthracene; and the 2-alkylanthraquinone is selected from at least one of 2-butylanthraquinone, 2-pentylanthraquinone and 2-hexylanthraquinone.

[0029] In this invention, the source of the 2-alkylanthracene oxidation reaction solution has a wide range of selection, as long as the 2-alkylanthracene oxidation reaction solution meets the above-mentioned limitations. Preferably, the 2-alkylanthracene oxidation reaction solution is prepared by oxidizing 2-alkylanthracene in the presence of an oxidizing solvent and an oxidizing catalyst.

[0030] In one specific embodiment of the present invention, the 2-alkylanthracene oxidation reaction solution is prepared by the following method: in the presence of an alkylation catalyst and an alkylation solvent, anthracene and an alkylation reagent are subjected to an alkylation reaction, and the resulting product containing 2-alkylanthracene is separated to obtain crude 2-alkylanthracene; in the presence of an oxidizing solvent and an oxidizing catalyst, the crude 2-alkylanthracene is subjected to an oxidizing reaction to obtain the 2-alkylanthracene oxidation reaction solution.

[0031] In this invention, the alkylation catalyst is selected from one or more liquid acids, preferably methanesulfonic acid and / or p-toluenesulfonic acid; based on the total weight of the feed liquid containing anthracene, the alkylation catalyst and the alkylation reaction solvent, the catalyst content is 0.01-50 wt%, preferably 0.5-30 wt%.

[0032] In this invention, the alkylation reaction solvent is C6 or higher, preferably C6-C. 12 The solvent is selected from one or more of alkanes, cycloalkanes, and aromatic hydrocarbons; wherein the aromatic hydrocarbon is substituted or unsubstituted, preferably one or more of mono- or poly-substituted benzene derivatives; more preferably one or more of poly-substituted benzene derivatives, wherein the substituent is one or more of C1-C4 alkyl and halogen elements; further preferably, the alkylation reaction solvent is one or more of polyalkyl-substituted benzene derivatives; most preferably, the alkylation reaction solvent is selected from one or more of 1,3,5-trimethylbenzene, 1,2,3,5-tetramethylbenzene, 1,3,4,5-tetramethylbenzene, 1,3,5,6-tetramethylbenzene, and 2,3,5,6-tetramethylbenzene. Based on the total weight of anthracene and the alkylation reaction solvent, the anthracene content is 5-60 wt%, preferably 8-50 wt%.

[0033] In this invention, the alkylating agent is one or more of olefins, alcohols, halogenated hydrocarbons, and ethers containing 2-8 carbon atoms, preferably one or more of olefins, alcohols, halogenated hydrocarbons, and ethers containing 4-6 carbon atoms, and more preferably a monoolefin containing 4-6 carbon atoms. The molar ratio of anthracene to the alkylating agent is 0.2-20:1, preferably 0.5-5:1.

[0034] In this invention, the conditions for the alkylation reaction include: a reaction temperature of 100-250°C, preferably 120-200°C; a reaction pressure of 0-1 MPa, preferably 0.05-0.5 MPa; and a reaction time of 0.01-48 h, preferably 0.5-24 h.

[0035] In this invention, the oxidizing solvent is selected from at least one of methanol, tert-butanol, acetone, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpropionamide, N-methylpyrrolidone, and N-ethylpyrrolidone.

[0036] In this invention, the oxidation catalyst is selected from metal catalysts and / or supported catalysts. The metal catalyst is selected from soluble compounds containing at least one metal element from Group IB, Group IVB, Group VB, Group VIIB, and Group VIII, such as chlorates, nitrates, and sulfates. The active component in the supported catalyst is selected from at least one metal from Group IB, Group IVB, Group VB, Group VIIB, and Group VIII, and the support is selected from inorganic heat-resistant oxides, including but not limited to alumina, silicon oxide, etc.

[0037] In this invention, the conditions for the oxidation reaction include: a reaction temperature of 25-100℃, preferably 50-75℃; a reaction pressure of 0.1-0.15MPa, preferably 0.08-0.12MPa; and a reaction time of 1-10h, preferably 3-6h.

[0038] In this invention, the distillation aims to remove water from the 2-alkylanthracene oxidation reaction solution to obtain a solid-liquid mixture with water ≤0.5 wt%, wherein the solid-liquid mixture contains 2-alkylanthracene, 2-alkylanthraquinone, hydrophilic impurities, and lipophilic impurities. Preferably, the distillation conditions include: a temperature of 25-100°C, preferably 45-80°C; a pressure of 6-101 kPa, preferably 15-55 kPa; a reflux ratio of 0.5-8, preferably 1-3; and a theoretical plate number of 10-90, preferably 30-75.

[0039] In this invention, the distillation is carried out in situ in a reaction vessel or in a distillation column. Water is obtained at the top of the column, and a solid-liquid mixture containing 2-alkylanthracene, 2-alkylanthraquinone, hydrophilic impurities, and lipophilic impurities is obtained at the bottom. During the distillation process, by controlling the water content in the solid-liquid mixture and combining it with a first filtration, the solid mixture rich in hydrophilic impurities is effectively removed, resulting in a liquid mixture containing 2-alkylanthracene, 2-alkylanthraquinone, and lipophilic impurities.

[0040] In some embodiments of the present invention, preferably, the temperature of the first filter is 25-100°C, more preferably 45-80°C.

[0041] In this invention, the first filter is selected from membrane filtration or centrifugal filtration, preferably membrane filtration, wherein the pore size of the filter membrane or filter cloth is 0.2-4 μm, preferably 0.4-1.2 μm.

[0042] In this invention, the crystallization is intended to remove 2-alkyl anthracene and most of the lipophilic impurities from a liquid mixture containing 2-alkyl anthracene, 2-alkyl anthraquinone and lipophilic impurities, to obtain 2-alkyl anthraquinone crystals. In addition to 2-alkyl anthraquinone, the 2-alkyl anthraquinone crystals inevitably contain residual hydrophilic impurities, such as heteroatoms, metal elements, etc.

[0043] In some embodiments of the present invention, preferably, in step (2), the crystallization conditions include: an initial temperature of 35-80°C, preferably 45-65°C; and an end temperature of -20 to 5°C, preferably -10 to 0°C.

[0044] In some embodiments of the present invention, preferably, the crystallization is selected from cooling-dissolution coupled crystallization, dissolution crystallization, and cooling crystallization; more preferably, it is selected from cooling-dissolution coupled crystallization and dissolution crystallization; and even more preferably, it is selected from cooling-dissolution coupled crystallization. In the present invention, the use of cooling-dissolution coupled crystallization technology can precisely balance crystal nucleation and growth rates, regulate crystal growth, and effectively control impurity inclusions in the crystal, laying a crucial foundation for obtaining high-purity 2-alkylanthraquinone.

[0045] In some embodiments of the present invention, preferably, in step (2), the cooling-dissolution coupled crystallization is selected from the following methods: crystallization followed by cooling, crystallization followed by cooling, and crystallization while simultaneously cooling. The preferred method is crystallization while simultaneously cooling. All three crystallization methods aim to balance and control the crystal nucleation rate and growth rate, and to regulate the orderly growth of crystals in a crystallization solution containing a relatively large number of impurities, thereby better ensuring crystal quality and improving purity.

[0046] In this invention, unless otherwise specified, when the cooling-dissolution coupled crystallization is selected from the method of first dissolution crystallization and then cooling crystallization, the solvent is first added to the crystallization liquid and then the temperature is lowered; when the cooling-dissolution coupled crystallization is selected from the method of first cooling crystallization and then dissolution crystallization, the crystallization liquid is first cooled and then the solvent is added; when the cooling-dissolution coupled crystallization is selected from the method of simultaneous dissolution crystallization and cooling crystallization, the addition of the solvent and the cooling are carried out simultaneously.

[0047] In some embodiments of the present invention, preferably, the solvent in the dissolution crystallization is selected from water; more preferably, the water obtained from the distillation is returned and mixed into the solvent. This arrangement further saves material consumption.

[0048] In some embodiments of the present invention, preferably, the weight ratio of the solvent to the crystallizing liquid is 1:1-15, for example, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:10, 1:15, and any value within any range of two such values, preferably 1:2-7. Using these preferred conditions is more conducive to improving the purity of 2-alkylanthraquinone crystals.

[0049] In some embodiments of the present invention, preferably, when the cooling-dissolution coupled crystallization is selected from the case of dissolution crystallization followed by cooling crystallization, the dissolution crystallization process is divided into four stages. In the first stage, a portion of the dissolution agent is added at a rate of 0.02-0.2 g / (g). 结晶液 ×h); Stage I-2, stabilization period, time is 0.1-1.3h; Stage I-3, the remaining solvent is added at a rate of 0.1-1g / (g) 结晶液 ×h); Phase I-4, the stable period, lasts 0.1-1.3h.

[0050] In some embodiments of the present invention, preferably, the cooling-dissolution coupled crystallization is selected from the case of first dissolution crystallization and then cooling crystallization, and the weight ratio of the portion of the dissolution agent to the remaining portion of the dissolution agent is 5-25:75-95.

[0051] In some embodiments of the present invention, preferably, in the first-second stage, 2-alkylanthraquinone seed crystals are added, wherein the weight ratio of the 2-alkylanthraquinone seed crystals to the crystallization liquid based on 2-alkylanthraquinone is 0.01-20:100, for example, 0.01:100, 0.1:100, 0.5:100, 1:100, 2:100, 5:100, 6:100, 8:100, 10:100, 15:100, 20:100, and any value within the range of any two values, preferably 0.5-10:100. This configuration, by adding 2-alkylanthraquinone seed crystals in the first-second stage, inhibits explosive nucleation, promotes crystal growth, reduces crystal inclusions, and improves crystal purity.

[0052] In some embodiments of the present invention, preferably, when the cooling-dissolution coupled crystallization is selected from dissolution crystallization followed by cooling crystallization, the cooling crystallization process includes: a cooling rate from the initial temperature to the final temperature of 0.1-2℃ / min, preferably 0.5-1℃ / min; and a final crystal growth time of 0.2-6h, preferably 0.5-2h. More preferably, the cooling crystallization process further includes: maintaining a constant temperature for 0.1-1.5h after cooling to any temperature between 10-60℃. Using these preferred conditions more effectively suppresses crystal growth and consumes supersaturation.

[0053] In some embodiments of the present invention, preferably, when the cooling-dissolution coupled crystallization is selected from cooling crystallization followed by dissolution crystallization, the cooling crystallization process is divided into four stages: Stage II-1, cooling from the initial temperature to 30-60℃ at a cooling rate of 0.01-0.1℃ / min; Stage II-2, isothermal stage, for 0.2-1h; Stage II-3, continuing to cool to the final temperature at a cooling rate of 0.1-2℃ / min; Stage II-4, isothermal crystal growth stage, for 0.2-2h.

[0054] In some embodiments of the present invention, more preferably, in stage II-1, the initial temperature is reduced to 30-55℃ at a cooling rate of 0.02-0.05℃ / min; in stage II-2, a constant temperature stage is maintained for 0.4-0.8h; in stage II-3, the temperature is further reduced to the final temperature at a cooling rate of 0.2-1℃ / min; and in stage II-4, a constant temperature crystal growth stage is maintained for 0.5-1h.

[0055] In some embodiments of the present invention, preferably, in the II-2 stage, 2-alkylanthraquinone seed crystals are added, wherein the weight ratio of the 2-alkylanthraquinone seed crystals to the crystallization liquid based on 2-alkylanthraquinone is 0.01-20:100, for example, 0.01:100, 0.1:100, 0.5:100, 1:100, 2:100, 5:100, 6:100, 8:100, 10:100, 15:100, 20:100, and any value within any range of any two values, preferably 0.5-10:100. This configuration, by adding 2-alkylanthraquinone seed crystals in the II-2 stage, inhibits explosive nucleation, promotes crystal growth, reduces crystal inclusions, and improves crystal purity.

[0056] In some embodiments of the present invention, preferably, when the cooling-dissolution coupled crystallization is selected from cooling crystallization followed by dissolution crystallization, the dissolution crystallization process involves a dissolution agent at a concentration of 0.1-1 g / (g). 结晶液 The solvent is added at a rate of 0.2-0.8 g / (g·h), and then crystallized at a constant temperature for 0.1-1.3 h; more preferably, the solvent is added at a rate of 0.2-0.8 g / (g·h).结晶液 The solvent is added at a rate of (×h), and then the crystals are grown at a constant temperature for 0.5-1h. More preferably, when the amount of solvent added is 1 / 3-2 / 3 of the total amount of solvent used, the process is paused for 0.5-1h, and the remaining solvent is added. Using these preferred conditions, crystal growth is more effectively controlled, and supersaturation is consumed.

[0057] In some embodiments of the present invention, preferably, when the cooling-dissolution coupled crystallization is selected as simultaneous dissolution crystallization and cooling crystallization, the simultaneous dissolution crystallization and cooling crystallization process is divided into six stages. In stage III-1, a first portion of the solvent is added and the temperature is lowered, with an addition rate of 0.01-0.1 g / (g) 结晶液 ×h), cooling rate is 0.1-0.5℃ / min, cooling to 35-60℃; Stage III-2, stabilization period, isothermal time is 0.1-1.3h; Stage III-3, addition of the second part of the solvent and cooling, addition rate is 0.1-0.5g / (g 结晶液 ×h), cooling rate is 0.2-1℃ / min; cooling to 10-35℃; stage III-4, stabilization period, isothermal time is 0.2-2h; stage III-5, addition of the third part of the solvent and cooling, addition rate is 0.1-1g / (g 结晶液 The cooling rate is 0.5-2℃ / min, reaching the final temperature; in stages III-6, crystal growth is carried out at a constant temperature for 0.2-6 hours. In this invention, stages III-4 effectively control crystal growth and consume supersaturation; stages III-6 improve crystal yield.

[0058] In some embodiments of the present invention, preferably, the weight ratio of the first portion of the solvent, the second portion of the solvent, and the third portion of the solvent in the solvent is 5-15:10-45:40-80. This controls crystal nucleation and growth while ensuring crystal purity and yield.

[0059] In some embodiments of the present invention, preferably, in the III-2 stage, 2-alkylanthraquinone seed crystals are added, wherein the weight ratio of the 2-alkylanthraquinone seed crystals to the crystallization liquid based on 2-alkylanthraquinone is 0.01-20:100, for example, 0.01:100, 0.1:100, 0.5:100, 1:100, 2:100, 5:100, 6:100, 8:100, 10:100, 15:100, 20:100, and any value within the range of any two values, preferably 0.5-10:100.

[0060] In this invention, the purification aims to further remove residual hydrophilic impurities (e.g., heteroatoms, metal ions, etc.) from the 2-alkylanthraquinone crystals. Preferably, in step (3), the purification process includes: performing melt extraction on the 2-alkylanthraquinone crystals and an extractant, and then cooling and second filtering the resulting melt-extracted product to obtain the 2-alkylanthraquinone product.

[0061] In some embodiments of the present invention, preferably, the conditions for melt extraction include: temperature ≥ 60°C, preferably 60-100°C; time 0.1-5h, preferably 0.5-3h.

[0062] In some embodiments of the present invention, preferably, the extractant is selected from water, and the weight ratio of the 2-alkylanthraquinone crystals to the extractant is 0.1-10:1, for example, 0.1:1, 0.5:1, 1:1, 1.5:1, 2:1, 5:1, 8:1, 10:1, and any value within the range of any two values, preferably 0.5-2:1.

[0063] In this invention, the cooling is intended to utilize the phase transition characteristic of 2-alkylanthraquinone at low temperatures to solidify the 2-alkylanthraquinone, followed by a second filtration to obtain the 2-alkylanthraquinone product. Preferably, the cooling and second filtration conditions each independently include: a temperature ≤ 45°C, more preferably 20-45°C.

[0064] In some embodiments of the present invention, preferably, the separation method further includes: subjecting the crystallized product to a third filtration; more preferably, the temperature of the third filtration is -20 to 5°C, for example, -20°C, -10°C, -5°C, 0°C, 5°C, and any value within the range of any two values, preferably -10 to 0°C.

[0065] In some embodiments of the present invention, preferably, the separation method further includes: repeating the purification process 1-5 times to obtain the 2-alkylanthraquinone product.

[0066] The separation method provided by this invention, targeting the complex composition of 2-alkylanthraquinone oxidation reaction solution, significantly reduces energy consumption and operational difficulty in the separation process by coupling distillation-cooling-dissolution crystallization and purification, and substantially reduces the content of trace impurities in the product, thus facilitating the acquisition of high-purity 2-alkylanthraquinone products. Furthermore, this separation method introduces only water (as a solvent and extractant), without introducing other impurities, and the water can be recycled. It boasts advantages such as simple process, high efficiency, low pollution, and environmental friendliness.

[0067] The second aspect of the present invention provides a 2-alkylanthraquinone product obtained by the separation method provided in the first aspect.

[0068] According to the present invention, preferably, the 2-alkylanthraquinone content in the 2-alkylanthraquinone product is ≥98.5 wt%, more preferably ≥99.5 wt%; the heteroatom content is ≤20 ppm, more preferably ≤15 ppm; and the total metal content is ≤20 ppm, more preferably ≤5 ppm. Wherein, heteroatom content refers to the content of single heteroatoms, and heteroatoms include, but are not limited to, P, N, Cl, S, and Si.

[0069] In this invention, unless otherwise specified, the 2-alkylanthraquinone content parameter is determined according to GB / T23672-2009; the heteroatom content parameter is determined according to GB / T 17476-1998; and the metal content parameter is determined according to SH / T 0715-2002.

[0070] The third aspect of this invention provides the application of the 2-alkylanthraquinone product provided in the second aspect in the preparation of hydrogen peroxide.

[0071] According to a particularly preferred embodiment of the present invention, a method for separating 2-alkylanthraquinone includes the following steps:

[0072] (1) The 2-alkylanthracene oxidation reaction solution is distilled to obtain water and a solid-liquid mixture with a water content of 1-5 wt%; the solid-liquid mixture is first filtered to obtain a solid mixture rich in hydrophilic impurities and a liquid mixture containing 2-alkylanthracene, 2-alkylanthraquinone and lipophilic impurities;

[0073] (2) The liquid mixture was used as a crystallizing liquid and subjected to cooling-dissolution coupled crystallization to obtain 2-alkylanthraquinone crystals;

[0074] (3) The 2-alkylanthraquinone crystals are purified to obtain the 2-alkylanthraquinone product;

[0075] Based on the total weight of the 2-alkylanthraquinone oxidation reaction solution, the content of 2-alkylanthraquinone is 0.1-3 wt%; the content of 2-alkylanthraquinone is 5-15 wt%; the content of water is 20-30 wt%; the content of hydrophilic impurities is 0.5-10 wt%; and the content of lipophilic impurities is 0.5-5 wt%.

[0076] Wherein, the 2-alkylanthracene is selected from at least one of 2-butylanthracene, 2-pentylanthracene, and 2-hexylanthracene; the 2-alkylanthraquinone is selected from at least one of 2-butylanthraquinone, 2-pentylanthraquinone, and 2-hexylanthraquinone;

[0077] The cooling-dissolution coupled crystallization is selected from the following: first dissolution crystallization followed by cooling crystallization, first cooling crystallization followed by dissolution crystallization, and simultaneous dissolution crystallization and cooling crystallization; during the dissolution crystallization process, the solvent is selected from water; the weight ratio of the solvent to the crystallization liquid is 1:2-7; the water obtained in step (1) is returned and mixed into the solvent.

[0078] The present invention will be described in detail below through embodiments.

[0079] The 2-alkylanthraquinone content in the 2-alkylanthraquinone oxidation reaction solution A1 is 7.3 wt%, the 2-alkylanthraquinone content is 0.5 wt%, the water content is 27.7 wt%, the hydrophilic impurity content is 1 wt%, and the lipophilic impurity content is 0.7 wt%.

[0080] The 2-alkylanthraquinone content in the 2-alkylanthraquinone oxidation reaction solution A2 is 11.2 wt%, the 2-alkylanthraquinone content is 0.7 wt%, the water content is 21.5 wt%, the hydrophilic impurity content is 1.9 wt%, and the lipophilic impurity content is 1.5 wt%.

[0081] The 2-alkylanthraquinone content in the 2-alkylanthraquinone oxidation reaction solution A3 is 6.3 wt%, the 2-alkylanthraquinone content is 0.7 wt%, the water content is 27.4 wt%, the hydrophilic impurity content is 0.9 wt%, and the lipophilic impurity content is 1.5 wt%.

[0082] Example 1

[0083] (1) 1080g of 2-alkylanthracene (a mixture of 2-butylanthracene, 2-pentylanthracene and 2-hexylanthracene) oxidation reaction solution A1 was distilled (temperature 25℃, pressure 6kPa, theoretical plate number 25, reflux ratio 4) to obtain 275g of water and a solid-liquid mixture with a water content of 3wt%; the above solid-liquid mixture was filtered at 80℃ (filter membrane pore size 0.8μm) to obtain 8.7g of solid mixture (rich in hydrophilic impurities) and 796.3g of liquid mixture (containing 2-alkylanthracene, 2-alkylanthraquinone and lipophilic impurities);

[0084] (2) The above liquid mixture was used as a crystallization liquid for simultaneous dissolution and cooling crystallization. The total amount of solvent (water) was 397.2g (including 275g of water obtained by distillation).

[0085] In stage III-1, a solvent is added and the temperature is lowered, with an addition rate of 0.05 g / (g). 结晶液×h); the initial temperature is 65℃, and the cooling rate is 0.1℃ / min; when the temperature drops to 55℃, the addition of solvent and cooling are stopped simultaneously; in stage III-2, the stabilization period, 8.4g of 2-alkylanthraquinone seed crystals are added for 0.5h; in stage III-3, solvent is added and cooling is continued, with the solvent addition rate being 0.1g / (g) 结晶液 ×h), cooling rate is 0.5℃ / min, cooling to 15℃; Stage III-4, stabilization period, isothermal time is 0.5h; Stage III-5, addition of solvent and cooling, addition rate is 0.5g / (g 结晶液 ×h), cooling rate is 0.5℃ / min until the solvent is completely added and the temperature is reduced to the final temperature of -10℃; in stages III-6, crystallization is carried out at constant temperature for 0.5h, followed by constant temperature filtration to obtain 77g of 2-alkylanthraquinone crystals and crystallization mother liquor (containing lipophilic impurities, 2-alkylanthracene and water).

[0086] In stages III-1, III-3, and III-5, the weight ratio of the solvent is 8.3:13.3:78.4.

[0087] (3) The above 2-alkylanthraquinone crystals and water were melt-extracted at a weight ratio of 1:1 (temperature 80℃, time 1h). The resulting mixture was cooled to 30℃ and filtered at a constant temperature to obtain 72.8g of solid 2-alkylanthraquinone product S1.

[0088] The purity of 2-alkylanthraquinone product S1 was 99.7 wt%, and the yield was 92.3%.

[0089] Based on the total weight of 2-alkylanthraquinone product S1, the content of 2-butylanthraquinone is 16.2 wt%, the content of 2-pentylanthraquinone is 82.3 wt%, the content of 2-hexylanthraquinone is 1.2 wt%, the content of N is 2.6 ppm, the content of Cl is 0.7 ppm, the content of S is 12 ppm, and the total metal content is 3.55 ppm.

[0090] Example 2

[0091] (1) 5129g of 2-alkylanthracene (2-hexylanthracene) oxidation reaction solution A2 was distilled (temperature 100℃, pressure 101kPa, theoretical plate number 30, reflux ratio 3.5) to obtain 1024g of water and a solid-liquid mixture with a water content of 2wt%; the above solid-liquid mixture was filtered at 65℃ (filter membrane pore size 1.2μm) to obtain 69.3g of solid mixture (rich in hydrophilic impurities) and 4035.7g of liquid mixture (containing 2-alkylanthracene, 2-alkylanthraquinone and lipophilic impurities);

[0092] (2) The above liquid mixture was used as a crystallization liquid for first dissolution and then cooling crystallization. The total amount of solvent (water) was 4035.7g (including 1024g of water obtained by distillation).

[0093] The crystallization process is divided into four stages. In stage I-1, a portion of the solvent is added at a rate of 0.075 g / (g). 结晶液 ×h); In stage I-2, during the stabilization period, 3g of 2-hexylanthracene seed crystals were added, and the mixture was stirred at a constant temperature for 1h; In stage I-3, the remaining solvent was added at a rate of 0.15g / (g) 结晶液 ×h); Stage I-4, stabilization period, constant temperature stirring for 0.3h; wherein, the weight ratio of part of the solvent to the remaining solvent is 15:85;

[0094] The cooling crystallization process includes: cooling from the initial temperature of 65℃ to the final temperature of -15℃ at a cooling rate of 0.5℃ / min, maintaining the temperature for 2 hours; filtering at the constant temperature to obtain 527.5g of 2-alkylanthraquinone crystals and crystallization mother liquor (containing lipophilic impurities, 2-alkylanthracene and water);

[0095] (3) The above 2-alkylanthraquinone crystals and water were melt-extracted at a weight ratio of 10:1 (temperature 70℃, time 2.5h). The resulting mixture was cooled to 20℃ and filtered at a constant temperature. Step (3) was repeated 3 times to obtain solid 2-alkylanthraquinone product S2.

[0096] The purity of 2-alkylanthraquinone product S2 was 99.8 wt%, and the yield was 91.8%.

[0097] Based on the total weight of the 2-alkylanthraquinone product S2, the 2-hexylanthraquinone content is 99.8 wt%; the N content is 12 ppm, the Cl content is 1.5 ppm, the S content is 13 ppm, and the total metal content is 4.3 ppm.

[0098] Example 3

[0099] (1) 3036g of 2-alkylanthracene (a mixture of 2-butylanthracene and 2-pentylanthracene) oxidation reaction solution A3 was distilled (temperature 77℃, pressure 50kPa, theoretical plate number 30, reflux ratio 2) to obtain 718g of water and a solid-liquid mixture with a water content of 5wt%; the above solid-liquid mixture was filtered at 70℃ (filter membrane pore size 0.45μm) to obtain 20.5g of solid mixture (rich in hydrophilic impurities) and 2297.5g of liquid mixture (containing 2-alkylanthracene, 2-alkylanthraquinone and lipophilic impurities);

[0100] (2) The above liquid mixture is used as a crystallization liquid for first cooling and then dissolving and crystallizing, wherein the total amount of solvent (water) is 818g (including 718g of water obtained by distillation);

[0101] The cooling crystallization process is divided into four stages: Stage II-1, the initial temperature is reduced from 70℃ to 60℃ at a cooling rate of 0.05℃ / min; Stage II-2, the isothermal stage, 12g of 2-alkylanthraquinone seed crystals are added and the temperature is maintained for 0.3h; Stage II-3, the temperature is reduced to the final temperature of -20℃ at a cooling rate of 0.4℃ / min; Stage II-4, the crystals are grown at a constant temperature for 0.3h.

[0102] During the crystallization process, the above-mentioned solvent is used at a concentration of 0.5 g / (g). 结晶液 The mixture was added at a rate of ×h, and then kept at a constant temperature for 0.5h to grow crystals; after constant temperature filtration, 174.3g of 2-alkylanthraquinone crystals and crystallization mother liquor (containing lipophilic impurities, 2-alkylanthracene and water) were obtained.

[0103] (3) The above 2-alkylanthraquinone crystals and water were melt-extracted at a weight ratio of 2:1 (temperature 80℃, time 1h). The resulting mixture was cooled to 40℃ and filtered at a constant temperature. Step (3) was repeated twice to obtain 173.7g of solid 2-alkylanthraquinone product S3.

[0104] The purity of 2-alkylanthraquinone product S3 was 99.6 wt%, and the yield was 90.8%.

[0105] Based on the total weight of 2-alkylanthraquinone product S3, the content of 2-butylanthraquinone is 23.9 wt%, the content of 2-pentylanthraquinone is 75.7 wt%, the content of N is 7 ppm, the content of Cl is 2.4 ppm, the content of S is 11 ppm, and the total metal content is 3.9 ppm.

[0106] Example 4

[0107] The method of Example 1 is followed, except that in step (2), the weight ratio of the solvent in stages III-1, III-3 and IIII-5 is replaced with 40:30:30, and the other conditions are the same, and the purity of the 2-alkylanthraquinone product S4 is 98.6 wt% and the yield is 90%.

[0108] Based on the total weight of 2-alkylanthraquinone product S4, the content of 2-butylanthraquinone is 15.3 wt%, the content of 2-pentylanthraquinone is 82.2 wt%, and the content of 2-hexylanthraquinone is 1.1 wt%; the content of N is 14 ppm, the content of Cl is 20 ppm, the content of S is 10 ppm, and the total metal content is 18 ppm.

[0109] Example 5

[0110] The method of Example 1 is different except that in step (2), the above liquid mixture at 65°C is cooled and crystallized at a cooling rate of 0.1°C / min, cooled to -10°C, and filtered at a constant temperature to obtain 2-alkylanthraquinone crystals and crystallization mother liquor.

[0111] Under the same conditions, the purity of the 2-alkylanthraquinone product S6 was 99.2 wt%, and the yield was 85%.

[0112] Based on the total weight of 2-alkylanthraquinone product S6, the content of 2-butylanthraquinone is 15.1 wt%, the content of 2-pentylanthraquinone is 83.6 wt%, and the content of 2-hexylanthraquinone is 0.5 wt%; the content of N is 19 ppm, the content of Cl is 15 ppm, the content of S is 16 ppm, and the total metal content is 19 ppm.

[0113] Example 6

[0114] The method of Example 1 is different except that step (2) is different, that is, the crystallizing solution at 65°C is dissolved and crystallized.

[0115] The dissolution and crystallization process is divided into four stages. In stage I-1, the addition rate is 0.05 g / (g) 结晶液 ×h), add 1 / 10 and stop; in stage I-2, add 0.5g of 2-alkylanthraquinone seed crystals and stir at a constant temperature for 1h; in stage I-3, continue to add the remaining solvent at a rate of 0.3g / (g) 结晶液 After the addition of the ingredients (×h), the mixture was stirred at a constant temperature for 0.3h, and then filtered at a constant temperature to obtain 2-alkylanthraquinone crystals and a mother liquor for crystallization.

[0116] Under the same conditions, the purity of the 2-alkylanthraquinone product S6 was 99.7 wt%, and the yield was 43%.

[0117] Based on the total weight of 2-alkylanthraquinone product S6, the content of 2-butylanthraquinone is 8.4 wt%, the content of 2-pentylanthraquinone is 91.2 wt%, the content of 2-hexylanthraquinone is 0.1 wt%, the content of N is 2.2 ppm, the content of Cl is 1.4 ppm, the content of S is 8 ppm, and the total metal content is 5 ppm.

[0118] Comparative Example 1

[0119] 1080g of 2-alkylanthracene (a mixture of 2-butylanthracene, 2-pentylanthracene, and 2-hexylanthracene) oxidation reaction solution A1 was fed into a vacuum distillation system for direct multi-stage vacuum distillation.

[0120] The process involves the following steps: First, the extract is subjected to vacuum distillation (temperature 81.5℃; pressure 10 kPa; theoretical plates 30; reflux ratio 2), yielding solvent at the top and a mixture containing 2-alkylanthracene and 2-alkylanthraquinone at the bottom. Second, this mixture is subjected to vacuum distillation (temperature 180-230℃; pressure 0.5 kPa; theoretical plates 45; reflux ratio 4), yielding a 2-alkylanthracene fraction at the top and a 2-alkylanthraquinone mixture at the bottom. Third, this mixture is subjected to vacuum distillation (temperature 230-260℃; pressure 0.5 kPa; theoretical plates 45; reflux ratio 5), yielding a 2-alkylanthraquinone fraction at the bottom, which is then used as 2-alkylanthraquinone. The bottom of the distillation also yields a mixture rich in heavy component impurities.

[0121] The above-mentioned 2-alkylanthraquinone was cooled and crystallized. The 2-alkylanthraquinone was dissolved in a crystallization solvent (methanol and hexanol) at 55°C, wherein the weight ratio of methanol, hexanol and 2-alkylanthraquinone was 0.4:0.4:1. After being kept at this temperature for 0.3 h, the temperature was lowered to 40°C for 2 h, and 8.5 g of seed crystals were added. After being kept at this temperature for 0.5 h, the temperature was lowered to -10°C for 3 h and kept at this temperature for 0.3 h. The mixture was then filtered while cold, and the obtained 2-alkylanthraquinone crystals were vacuum dried to obtain 170 g of the 2-alkylanthraquinone product DS1.

[0122] Among them, the purity of 2-alkylanthraquinone product DS1 was 98.5 wt%, and the yield was 84%.

[0123] Based on the total weight of DS1, a 2-alkylanthraquinone product, the content of 2-butylanthraquinone is 14 wt%, the content of 2-pentylanthraquinone is 82.8 wt%, and the content of 2-hexylanthraquinone is 1.7 wt%; the content of N is 38 ppm, the content of Cl is 25 ppm, the content of S is 140 ppm, the content of Si is 43 ppm, and the total metal content is 18 ppm.

[0124] Comparative Example 2

[0125] The method of Example 1 is different except that in step (1), the water content in the solid-liquid mixture is adjusted to 8 wt% by adjusting the distillation conditions, and the other conditions are the same, so that the purity of the 2-alkylanthraquinone product DS2 is 98.1 wt% and the yield is 93%.

[0126] Based on the total weight of the 2-alkylanthraquinone product DS2, the content of 2-butylanthraquinone is 13.4 wt%, the content of 2-pentylanthraquinone is 83.1 wt%, and the content of 2-hexylanthraquinone is 1.6 wt%; the content of N is 14 ppm, the content of Cl is 33 ppm, the content of S is 28 ppm, and the total metal content is 24 ppm.

[0127] Compared with Comparative Examples 1-2, the 2-alkylanthraquinone product prepared by the method provided by this invention not only has high purity, but also effectively reduces the total impurity content and metal content in the 2-alkylanthraquinone product. That is, the 2-alkylanthraquinone product meets the following requirements: 2-alkylanthraquinone content ≥ 98.5 wt%, heteroatom content ≤ 20 ppm, and total metal content ≤ 20 ppm. At the same time, the 2-alkylanthraquinone product prepared by the method provided by this invention has good individual impurity indicators and can be used as a standard for 2-alkylanthraquinone.

[0128] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for separating 2-alkylanthraquinone, characterized in that, The separation method includes the following steps: (1) The 2-alkylanthracene oxidation reaction solution is distilled to obtain water and a solid-liquid mixture with a water content of 1-5 wt%; the solid-liquid mixture is filtered for the first time to obtain a solid mixture rich in hydrophilic impurities and a liquid mixture containing 2-alkylanthracene, 2-alkylanthraquinone and lipophilic impurities; (2) The liquid mixture is used as a crystallization liquid to crystallize and obtain 2-alkylanthraquinone crystals; (3) The 2-alkylanthraquinone crystals are purified to obtain the 2-alkylanthraquinone product; The 2-alkylanthracene oxidation reaction solution is composed of 2-alkylanthracene, 2-alkylanthraquinone, water, hydrophilic impurities, and lipophilic impurities. Based on the total weight of the 2-alkylanthracene oxidation reaction solution, the content of the 2-alkylanthracene is 0.1-6 wt%; the content of the 2-alkylanthraquinone is 3-25 wt%; the content of water is 5-40 wt%; the content of the hydrophilic impurities is 0.1-35 wt%; and the content of the lipophilic impurities is 0.1-10 wt%. The crystallization is a cooling-dissolution coupled crystallization; In step (3), the purification process includes: melting and extracting the 2-alkylanthraquinone crystal and the extractant, and then cooling and filtering the resulting melt-extracted product to obtain the 2-alkylanthraquinone product. The extractant is water.

2. The separation method according to claim 1, wherein, Based on the total weight of the 2-alkylanthracene oxidation reaction solution, the content of 2-alkylanthracene is 0.1-3 wt%; the content of 2-alkylanthraquinone is 5-15 wt%; the content of water is 20-30 wt%; the content of hydrophilic impurities is 0.5-10 wt%; and the content of lipophilic impurities is 0.5-5 wt%. And / or, the 2-alkylanthraquinone is selected from at least one of 2-butylanthraquinone, 2-pentylanthraquinone, and 2-hexylanthraquinone; the 2-alkylanthraquinone is selected from at least one of 2-butylanthraquinone, 2-pentylanthraquinone, and 2-hexylanthraquinone.

3. The separation method according to claim 1 or 2, wherein, In step (1), the distillation conditions include: temperature of 25-100℃; pressure of 6-101kPa; reflux ratio of 0.5-8; and theoretical plate number of 10-90. And / or, the temperature of the first filter is 25-100°C.

4. The separation method according to claim 3, wherein, In step (1), the distillation conditions include: temperature of 45-80℃; pressure of 15-55kPa; reflux ratio of 1-3; and theoretical plate number of 30-75.

5. The separation method according to claim 3, wherein, In step (1), the temperature of the first filter is 45-80℃.

6. The separation method according to claim 1 or 2, wherein, In step (2), the crystallization conditions include: an initial temperature of 35-80℃; and an ending temperature of -20 to 5℃. And / or, in step (2), the cooling-dissolution coupled crystallization is selected from the following: first dissolution crystallization followed by cooling crystallization, first cooling crystallization followed by dissolution crystallization, and simultaneous dissolution crystallization and cooling crystallization; And / or, in step (2), during the crystallization process, the solvent is selected from water.

7. The separation method according to claim 6, wherein, In step (2), the crystallization conditions include: an initial temperature of 45-65℃ and an end temperature of -10 to 0℃.

8. The separation method according to claim 6, wherein, In step (2), the cooling-dissolution coupled crystallization is a process of simultaneous dissolution crystallization and cooling crystallization.

9. The separation method according to claim 6, wherein, In step (2), the weight ratio of the solvent to the crystallizing liquid is 1:1-15.

10. The separation method according to claim 9, wherein, In step (2), the weight ratio of the solvent to the crystallizing liquid is 1:2-7.

11. The separation method according to claim 6, wherein, In step (2), the water obtained in step (1) is returned and mixed into the solvent.

12. The separation method according to claim 6, wherein, When the cooling-dissolution coupled crystallization is selected from the case of dissolution crystallization followed by cooling crystallization, the dissolution crystallization process is divided into four stages. In the first stage, a portion of the dissolution agent is added at a rate of 0.02-0.2 g / (g). 结晶液 ×h); Stage I-2, stabilization period, time is 0.1-1.3h; Stage I-3, the remaining solvent is added at a rate of 0.1-1g / (g) 结晶液 ×h); Phase I-4, the stable period, lasts 0.1-1.3h.

13. The separation method according to claim 12, wherein, When the cooling-dissolution coupled crystallization is selected from the case of dissolution crystallization followed by cooling crystallization, the weight ratio of the portion of the dissolution agent to the remaining portion of the dissolution agent is 5-25:75-95.

14. The separation method according to claim 12, wherein, In stage I-2, 2-alkylanthraquinone seed crystals are added, wherein the weight ratio of the 2-alkylanthraquinone seed crystals to the 2-alkylanthraquinone in the crystallization solution (calculated as 2-alkylanthraquinone) is 0.01-20:

100.

15. The separation method according to claim 14, wherein, In stage I-2, 2-alkylanthraquinone seed crystals are added, wherein the weight ratio of the 2-alkylanthraquinone seed crystals to the 2-alkylanthraquinone in the crystallization solution (calculated as 2-alkylanthraquinone) is 0.5-10:

100.

16. The separation method according to claim 6, wherein, When the cooling-dissolution coupled crystallization is selected from the first dissolution crystallization followed by cooling crystallization, the cooling crystallization process includes: a cooling rate of 0.1-2℃ / min from the initial temperature to the final temperature; and a final crystal growth time of 0.2-6h.

17. The separation method according to claim 16, wherein, When the cooling-dissolution coupled crystallization is selected from the first dissolution crystallization followed by cooling crystallization, the cooling crystallization process includes: a cooling rate of 0.5-1℃ / min from the initial temperature to the final temperature; and a final crystallization time of 0.5-2h.

18. The separation method according to claim 16, wherein, When the cooling-dissolution coupled crystallization is selected from the first dissolution crystallization followed by cooling crystallization, the cooling crystallization process further includes: cooling the temperature to any temperature between 10-60℃ and holding it at that temperature for 0.1-1.5 hours.

19. The separation method according to claim 6, wherein, When the cooling-dissolution coupled crystallization is selected from the first cooling crystallization followed by dissolution crystallization, the cooling crystallization process is divided into four stages: Stage II-1, cooling from the initial temperature to 30-60℃ at a cooling rate of 0.01-0.1℃ / min; Stage II-2, isothermal stage, for 0.2-1h; Stage II-3, continuing to cool to the final temperature at a cooling rate of 0.1-2℃ / min; Stage II-4, isothermal crystal growth stage, for 0.2-2h.

20. The separation method according to claim 19, wherein, When the cooling-dissolution coupled crystallization is selected from the first cooling crystallization followed by dissolution crystallization, the cooling crystallization process is divided into four stages: Stage II-1, cooling from the initial temperature to 30-55℃ at a cooling rate of 0.02-0.05℃ / min; Stage II-2, isothermal stage, isothermal time of 0.4-0.8h; Stage II-3, continuing to cool to the final temperature at a cooling rate of 0.2-1℃ / min; Stage II-4, isothermal crystal growth stage, time of 0.5-1h.

21. The separation method according to claim 19, wherein, In stage II-2, 2-alkylanthraquinone seed crystals are added, wherein the weight ratio of the 2-alkylanthraquinone seed crystals to the 2-alkylanthraquinone in the crystallization solution (calculated as 2-alkylanthraquinone) is 0.01-20:

100.

22. The separation method according to claim 21, wherein, In stage II-2, 2-alkylanthraquinone seed crystals are added, wherein the weight ratio of the 2-alkylanthraquinone seed crystals to the 2-alkylanthraquinone in the crystallization solution (calculated as 2-alkylanthraquinone) is 0.5-10:

100.

23. The separation method according to claim 6, wherein, When the cooling-dissolution coupled crystallization is selected from the case of cooling crystallization followed by dissolution crystallization, during the dissolution crystallization process, the dissolving agent is used at a concentration of 0.1-1 g / (g). 结晶液 The crystals are added at a rate of ×h, and then kept at a constant temperature for 0.1-1.3h.

24. The separation method according to claim 23, wherein, When the cooling-dissolution coupled crystallization is selected from the case of cooling crystallization followed by dissolution crystallization, during the dissolution crystallization process, the dissolving agent is used at a concentration of 0.2-0.8 g / (g). 结晶液 The mixture was added at a rate of ×h, and then kept at a constant temperature for 0.5-1h to grow crystals.

25. The separation method according to claim 23, wherein, When the amount of solvent added is 1 / 3 to 2 / 3 of the total amount of solvent used, pause for 0.5 to 1 hour, and then add the remaining solvent.

26. The separation method according to claim 6, wherein, When the cooling-dissolution coupled crystallization is selected from simultaneous dissolution crystallization and cooling crystallization, the simultaneous dissolution crystallization and cooling crystallization process is divided into six stages. In stage III-1, the first part of the solvent is added and the temperature is lowered, with an addition rate of 0.01-0.1 g / (g) 结晶液 ×h), cooling rate is 0.1-0.5℃ / min, cooling to 35-60℃; Stage III-2, stabilization period, isothermal time is 0.1-1.3h; Stage III-3, addition of the second part of the solvent and cooling, addition rate is 0.1-0.5g / (g 结晶液 ×h), cooling rate is 0.2-1℃ / min; cooling to 10-35℃; stage III-4, stabilization period, isothermal time is 0.2-2h; stage III-5, addition of the third part of the solvent and cooling, addition rate is 0.1-1g / (g 结晶液 ×h), the cooling rate is 0.5-2℃ / min, and the temperature is reduced to the final temperature; in stages III-6, the crystals are grown at a constant temperature for 0.2-6h.

27. The separation method according to claim 26, wherein, The weight ratio of the first part of the solvent, the second part of the solvent, and the third part of the solvent in the solvent is 5-15:10-45:40-80.

28. The separation method according to claim 26, wherein, In stage III-2, 2-alkylanthraquinone seed crystals are added, wherein the weight ratio of the 2-alkylanthraquinone seed crystals to the crystallization liquid based on 2-alkylanthraquinone is 0.01-20:

100.

29. The separation method according to claim 28, wherein, In stage III-2, 2-alkylanthraquinone seed crystals are added, wherein the weight ratio of the 2-alkylanthraquinone seed crystals to the crystallization liquid based on 2-alkylanthraquinone is 0.5-10:

100.

30. The separation method according to claim 1 or 2, wherein, In step (3), the conditions for melt extraction include: temperature ≥ 60℃; time 0.1-5h.

31. The separation method according to claim 30, wherein, The conditions for the melt extraction include: a temperature of 60-100℃ and a time of 0.5-3h.

32. The separation method according to claim 1 or 2, wherein, In step (3), the weight ratio of the 2-alkylanthraquinone crystals to the extractant is 0.1-10:

1.

33. The separation method according to claim 32, wherein, In step (3), the weight ratio of the 2-alkylanthraquinone crystals to the extractant is 0.5-2:

1.

34. The separation method according to claim 1 or 2, wherein, In step (3), the temperatures of the cooling and the second filtration are each ≤45°C independently.

35. The separation method according to claim 34, wherein, In step (3), the temperatures of the cooling and the second filtration are each independently 20-45°C.

36. The separation method according to claim 1 or 2, wherein, The separation method further includes subjecting the crystallized product to a third filtration.

37. The separation method according to claim 36, wherein, The temperature of the third filter is -20 to 5°C.

38. The separation method according to claim 37, wherein, The temperature of the third filter is -10 to 0°C.

39. The separation method according to claim 1 or 2, wherein, The separation method further includes repeating the purification process 1-5 times to obtain the 2-alkylanthraquinone product.

40. The separation method according to claim 1 or 2, wherein, The 2-alkylanthraquinone product obtained by the separation method has a 2-alkylanthraquinone content ≥98.5wt%; heteroatom content ≤20ppm; and total metal content ≤20ppm.

41. The separation method according to claim 40, wherein, The 2-alkylanthraquinone product contains ≥99.5 wt% 2-alkylanthraquinone; ≤15 ppm heteroatom content; and ≤5 ppm total metal content.

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