A process for the recovery of anthraquinone from spent activated alumina using a soxhlet extractor

Abstract

This invention relates to a method for recovering anthraquinones from spent activated alumina using a Soxhlet extractor. The method first involves adding a solvent or mixed solvent to a reactor, then adding dried spent activated alumina to the Soxhlet extractor, which is then installed on the reactor. Heating causes the solvent to vaporize, rise, condense, and flow back into the reactor, repeating this cycle. After the experiment, the extract is rotary evaporated under reduced pressure until no more solvent is distilled off; the remaining solid is the product. This invention maximizes the recovery of anthraquinones and hydroanthraquinones. Furthermore, ethanol and cyclohexane have lower boiling points than the working solvents, resulting in lower energy consumption and a more environmentally friendly approach.

Description

Technical Field

[0001] This invention relates to anthraquinone recovery processes, and more particularly to a method for recovering anthraquinone from spent activated alumina in hydrogen peroxide production processes. Background Technology

[0002] Currently, large-scale hydrogen peroxide manufacturers both domestically and internationally employ the anthraquinone process. This method uses trioctyl phosphate and heavy aromatics as a mixed solvent, and 2-ethylanthraquinone as the solute, to form the working solution. The process involves catalytic hydrogenation, air oxidation, sieve plate extraction purification, and post-treatment within a closed system to produce hydrogen peroxide. The post-treatment section uses activated alumina to regenerate anthraquinone degradation products and adsorb alkali and water entrained in the working solution. Activated alumina consists of white, spherical particles with a porous internal structure and a short lifespan, typically around 80 days. A hydrogen peroxide company with an annual production capacity of 200,000 tons consumes approximately 1,500-2,000 tons of activated alumina balls annually, placing a significant financial burden on the production enterprise. After deactivation, the alumina is typically removed by steam purging to remove the working solution components adsorbed on the surface of the alumina particles. However, the removal effect is not ideal for the working solution components adsorbed in the mesopores within the alumina, especially the anthraquinone component (approximately 3%). This portion of anthraquinone is generally not recovered, resulting in significant production waste and severe environmental pollution. Therefore, recycling this anthraquinone has significant economic and environmental benefits. Consequently, how to recover this portion of anthraquinone has become a key concern for hydrogen peroxide producers and researchers.

[0003] There are few reports on the recovery of anthraquinone from spent activated alumina in existing technologies, such as Chinese patents CN115745770A and CN112645372B. Existing technologies all suffer from the following problems: high equipment investment, complex processes with low extraction efficiency, high energy consumption, and environmental unfriendliness. Summary of the Invention

[0004] To address the problems existing in the prior art, the purpose of this invention is to provide a method for recovering anthraquinone from waste activated alumina in the hydrogen peroxide production process. This method is simple and has high extraction efficiency.

[0005] The technical solution adopted by this invention to solve the above-mentioned technical problems is as follows: a method for recovering anthraquinones from waste activated alumina in hydrogen peroxide production process using a Soxhlet extractor, comprising the following steps:

[0006] Step 1: Dry the waste activated alumina discharged from the white clay bed device in the hydrogen peroxide workshop at 100-150℃ for 3 hours in a drying equipment;

[0007] Step 2: The dried waste activated alumina from Step 1 is loaded into a bag filter membrane and sealed, then transferred to the sleeve of a Soxhlet extractor.

[0008] Step 3: Add the mixed solvent of ethanol and cyclohexane to the reactor, and install the Soxhlet extractor from Step 2 onto the reactor.

[0009] Step 4: Heat the reactor from step 3, maintain the mixed solvent under reflux for 1-4 hours, then stop heating and allow it to cool.

[0010] Step 5: Distill the extract from the reactor in Step 4 under reduced pressure until no solvent is distilled off; the remaining solid is the product.

[0011] Furthermore, in step 1, the preferred temperature in the drying equipment is 120°C.

[0012] Furthermore, in step 3, the ratio of ethanol to cyclohexane in the mixed solvent is 1:1 to 1:4.

[0013] Furthermore, in step 3, the ratio of ethanol to cyclohexane in the mixed solvent of ethanol and cyclohexane is 1:3.

[0014] The working principle of this invention is:

[0015] Anthraquinone and hydroanthraquinone adsorbed by activated alumina have different polarities, making it impractical to recover the polar hydroanthraquinone using only non-polar solvents like heavy aromatics. Based on the principle of "like dissolves like," using a mixed solvent—a polar solvent similar to the working liquid phase, ethanol, and a non-polar solvent, cyclohexane, in specific proportions, can maximize the recovery of both anthraquinone and hydroanthraquinone.

[0016] Beneficial effects of the present invention

[0017] This invention uses ethanol and cyclohexane as a mixed solvent to recover anthraquinone from spent activated alumina in hydrogen peroxide production processes using a Soxhlet extractor. The optimal extraction rate of anthraquinone from spent activated alumina is 96.7% when the mass ratio of ethanol to cyclohexane is 1:3. The recovered anthraquinone has high value, with a market price of 40,000-60,000 RMB / ton, and can be reused as a solute in the working solution for hydrogen peroxide production, resulting in good economic benefits. Furthermore, from an energy-saving and environmental protection perspective, ethanol and cyclohexane have lower boiling points than the working solution solvents, resulting in lower energy consumption and a more environmentally friendly approach. Removing the working solution provides a new pathway for the subsequent treatment and comprehensive utilization of spent activated alumina, changing the environmental pollution caused by long-term stockpiling, landfilling, or incineration, and offering significant environmental benefits. Attached Figure Description

[0018] Figure 1 The liquid chromatograms are of standard solutions of anthraquinone (EAQ) and hydroanthraquinone (H4EAQ);

[0019] Figure 2 This is a liquid chromatogram of the extracts of anthraquinone (EAQ) and hydroanthraquinone (H4EAQ). Detailed Implementation

[0020] The features of the present invention are described below through examples. The present invention is not limited to the following embodiments, experimental examples, and comparative examples.

[0021] Example 1

[0022] 500g of spent activated alumina, dried at 120℃ for 3 hours in a drying device, was placed into a bag filter membrane and sealed. This bag was then transferred to the sleeve of a Soxhlet extractor. A mixed solvent of 500g of ethanol and cyclohexane (mass ratio 1:4) was added to the reactor. The Soxhlet extractor was then installed on the reactor, and heating was initiated. Timing began when the mixed solvent was refluxed. After reflux for 2 hours, heating was stopped, and the mixture was allowed to cool. 5mL of the extract was analyzed by liquid chromatography to determine the anthraquinone content. The remaining sample was distilled under reduced pressure to recover the solvent. The solid sample remaining in the reactor was the anthraquinone product.

[0023] Example 2

[0024] 500g of spent activated alumina, dried at 120℃ for 3 hours in a drying device, was placed into a bag filter membrane and sealed. This bag was then transferred to the sleeve of a Soxhlet extractor. A mixed solvent of 500g of ethanol and cyclohexane (mass ratio 1:3) was added to the reactor. The Soxhlet extractor was then installed on the reactor, and heating was initiated. Timing began when the mixed solvent was refluxed. After reflux for 2 hours, heating was stopped, and the mixture was allowed to cool. 5mL of the extract was analyzed by liquid chromatography to determine the anthraquinone content. The remaining sample was distilled under reduced pressure to recover the solvent. The solid sample remaining in the reactor was the anthraquinone product.

[0025] Example 3

[0026] 500g of spent activated alumina, dried at 120℃ for 3 hours in a drying device, was placed into a bag filter membrane and sealed. This bag was then transferred to the sleeve of a Soxhlet extractor. A mixed solvent of 500g of ethanol and cyclohexane (mass ratio 1:2) was added to the reactor. The Soxhlet extractor was then installed on the reactor, and heating was initiated. Timing began when the mixed solvent was refluxed. After reflux for 2 hours, heating was stopped. After cooling, 5mL of the extract was analyzed by liquid chromatography to determine the anthraquinone content. The remaining sample was distilled under reduced pressure to recover the solvent. The solid sample remaining in the reactor was the anthraquinone product.

[0027] Example 4

[0028] 500g of spent activated alumina, dried at 120℃ for 3 hours in a drying device, was placed into a bag filter membrane and sealed. This bag was then transferred to the sleeve of a Soxhlet extractor. A mixed solvent of 500g of ethanol and cyclohexane (mass ratio 1:1) was added to the reactor. The Soxhlet extractor was then installed on the reactor, and heating was initiated. Timing began when the mixed solvent was refluxed. After reflux for 2 hours, heating was stopped, and the mixture was allowed to cool. 5mL of the extract was analyzed by liquid chromatography to determine the anthraquinone content. The remaining sample was distilled under reduced pressure to recover the solvent. The solid sample remaining in the reactor was the anthraquinone product.

[0029] Experimental Example 1

[0030] 500g of spent activated alumina, dried at 120℃ for 3 hours in a drying device, was placed into a bag filter membrane and sealed. This bag was then transferred to the sleeve of a Soxhlet extractor. A mixed solvent of 500g of ethanol and cyclohexane (mass ratio 2:1) was added to the reactor. The Soxhlet extractor was then installed on the reactor, and heating was initiated. Timing began when the mixed solvent was refluxed. After reflux for 2 hours, heating was stopped, and the mixture was allowed to cool. 5mL of the extract was analyzed by liquid chromatography to determine the anthraquinone content. The remaining sample was distilled under reduced pressure to recover the solvent. The solid sample remaining in the reactor was the anthraquinone product.

[0031] Experiment Example 2

[0032] 500g of spent activated alumina, dried at 130℃ for 3 hours in a drying device, was placed into a bag filter membrane and sealed. This bag was then transferred to the sleeve of a Soxhlet extractor. A mixed solvent of 500g of ethanol and cyclohexane (mass ratio 3:1) was added to the reactor. The Soxhlet extractor was then installed on the reactor, and heating was initiated. Timing began when the mixed solvent was refluxed. After reflux for 2 hours, heating was stopped, and the mixture was allowed to cool. 5mL of the extract was analyzed by liquid chromatography to determine the anthraquinone content. The remaining sample was distilled under reduced pressure to recover the solvent. The solid sample remaining in the reactor was the anthraquinone product.

[0033] Experimental Example 3

[0034] 500g of spent activated alumina, dried at 140℃ for 3 hours in a drying device, was placed into a bag filter membrane and sealed. This bag was then transferred to the sleeve of a Soxhlet extractor. A mixed solvent of 500g of methanol and cyclohexane (mass ratio 2:1) was added to the reactor. The Soxhlet extractor was then installed on the reactor, and heating was initiated. Timing began when the mixed solvent was refluxed. After reflux for 2 hours, heating was stopped. After cooling, 5mL of the extract was analyzed by liquid chromatography to determine the anthraquinone content. The remaining sample was distilled under reduced pressure to recover the solvent. The solid sample remaining in the reactor was the anthraquinone product.

[0035] Experiment Example 4

[0036] 500g of spent activated alumina, dried at 140℃ for 3 hours in a drying device, was placed into a bag filter membrane and sealed. This bag was then transferred to the sleeve of a Soxhlet extractor. A mixed solvent of 500g of methanol and cyclohexane (mass ratio 1:4) was added to the reactor. The Soxhlet extractor was then installed on the reactor, and heating was initiated. Timing began when the mixed solvent was refluxed. After reflux for 2 hours, heating was stopped, and the mixture was allowed to cool. 5mL of the extract was analyzed by liquid chromatography to determine the anthraquinone content. The remaining sample was distilled under reduced pressure to recover the solvent. The solid sample remaining in the reactor was the anthraquinone product.

[0037] Experimental Example 5

[0038] 500g of spent activated alumina, dried at 140℃ for 3 hours in a drying device, was placed into a bag filter membrane and sealed. This bag was then transferred to the sleeve of a Soxhlet extractor. A mixed solvent of 500g of methanol and cyclohexane (mass ratio 1:5) was added to the reactor. The Soxhlet extractor was then installed on the reactor, and heating was initiated. Timing began when the mixed solvent was refluxed. After reflux for 2 hours, heating was stopped, and the mixture was allowed to cool. 5mL of the extract was analyzed by liquid chromatography to determine the anthraquinone content. The remaining sample was distilled under reduced pressure to recover the solvent. The solid sample remaining in the reactor was the anthraquinone product.

[0039] Comparative Example 1

[0040] This example is basically the same as Example 1, except that the solvent used is a mixture of ethanol and cyclohexane in a mass ratio of 1:3, and an anthraquinone is extracted using a conventional reflux apparatus.

[0041] Comparative Example 2

[0042] This example is basically the same as Example 1, except that the drying temperature of the waste activated alumina is 100°C, the solvent used is ethanol, and the reflux time is 4 hours.

[0043] Comparative Example 3

[0044] This example is basically the same as Example 1, except that the drying temperature of the waste activated alumina is 100°C, the solvent used is methanol, and the reflux time is 3 hours.

[0045] Comparative Example 4

[0046] This example is basically the same as Example 1, except that the drying temperature of the waste activated alumina is 110°C and the solvent used is 1,2-dichloroethane.

[0047] Comparative Example 5

[0048] This example is basically the same as Example 1, except that the drying temperature of the waste activated alumina is 110°C and the solvent used is cyclohexane.

[0049] Comparative Example 6

[0050] This example is basically the same as Example 1, except that the drying temperature of the waste activated alumina is 120°C, the solvent used is heavy aromatic hydrocarbon, and the reflux time is 1 hour.

[0051] Comparative Example 7

[0052] This example is basically the same as Example 1, except that the drying temperature of the waste activated alumina is 150°C, and the solvent used is a mixture of methanol and 1,2-dichloroethane in a mass ratio of 1:3.

[0053] Comparative Example 8

[0054] This example is basically the same as Example 1, except that the solvent used is a mixture of ethanol and heavy aromatic hydrocarbons in a mass ratio of 1:3.

[0055] The mass of anthraquinones extracted in Examples 1-4, Experimental Examples 1-5, and Comparative Examples 1-8 is shown in the table below. The liquid chromatograms of the extracted anthraquinones are as follows: Figure 2 As shown, the comparison is as follows Figure 1 The standard solution chromatogram shown indicates that the main component of the anthraquinone extract is anthraquinone, followed by hydroanthraquinone.

[0056] Table 1. Mass of anthraquinones extracted using a Soxhlet extractor with different solvents (Examples 1-3)

[0057]

[0058] Table 2. Mass of anthraquinone extracted using a Soxhlet extractor with different solvents (Experiments 1-5)

[0059]

[0060] Table 3. Mass of anthraquinone extracted using a Soxhlet extractor with different solvents (Comparative Examples 1–8)

[0061]

[0062] As can be seen from the examples in Table 1, when other reaction conditions are the same, the best extraction effect of anthraquinone from waste activated alumina is achieved when the mass ratio of the mixed solvent ethanol to cyclohexane is 1:3, with an anthraquinone recovery rate of 96.7%. This may be because waste activated alumina mainly contains anthraquinone, and a higher proportion of the non-polar solvent cyclohexane can better dissolve and extract anthraquinone. However, if the proportion of cyclohexane is too high, it will affect the dissolution and extraction of polar anthraquinone. Therefore, the optimal ratio of ethanol to cyclohexane is 1:3.

[0063] As can be seen from Experimental Examples 1 and 2 in Table 2 and Comparative Example 2 in Table 3, the extraction of anthraquinones from waste activated alumina is poor when the ethanol content in the mixed solvent is too high or when ethanol is used alone as the solvent, with a recovery rate of 49.3% to 61.3%. This may also be because the polar solvent ethanol cannot dissolve the non-polar anthraquinones well.

[0064] As can be seen from Experimental Examples 3, 4, and 5 in Table 2 and Comparative Example 3 in Table 3, when ethanol in the mixed solvent is replaced with methanol or methanol is used alone as the solvent, the extraction of anthraquinones from waste activated alumina is poor, with recovery rates ranging from 48.0% to 65.3%. This may be because methanol has a relatively high hydroxyl activity, which promotes the degradation of anthraquinones under reflux conditions, leading to a reduction in the content of extracted anthraquinones.

[0065] As can be seen from Comparative Example 8 in Table 3, when cyclohexane in the mixed solvent was replaced with heavy aromatics, the extraction of anthraquinone from waste activated alumina was better, with a recovery rate of 80.6%. The extraction effect was second only to that of the mixed solvents ethanol and cyclohexane, but heavy aromatics have a higher boiling point, resulting in higher energy consumption and environmental unfriendliness.

[0066] In summary, the best extraction effect of anthraquinone from waste activated alumina was achieved by a mixed solvent of ethanol and cyclohexane at a mass ratio of 1:3, followed by a mixed solvent of ethanol and heavy aromatics.

Claims

1. A method for recovering anthraquinones from spent activated alumina using a Soxhlet extractor, characterized in that: Includes the following steps: Step 1: Dry the waste activated alumina discharged from the white clay bed device in the hydrogen peroxide workshop at 100-150℃ for 3 hours in a drying equipment; Step 2: The dried waste activated alumina from Step 1 is loaded into a bag filter membrane and sealed, then transferred to the sleeve of a Soxhlet extractor. Step 3: Add the mixed solvent of ethanol and cyclohexane to the reactor, and install the Soxhlet extractor from Step 2 onto the reactor; Step 4: Heat the reactor from step 3, maintain the mixed solvent under reflux for 1-4 hours, then stop heating and allow it to cool. Step 5: Distill the extract from the reactor in Step 4 under reduced pressure until no solvent is distilled off; the remaining solid is the product.

2. The method for recovering anthraquinone from spent activated alumina using a Soxhlet extractor according to claim 1, characterized in that: In step 1, the preferred temperature in the drying equipment is 120°C.

3. The method for recovering anthraquinone from spent activated alumina using a Soxhlet extractor according to claim 1, characterized in that: In step 3, the ratio of ethanol to cyclohexane in the mixed solvent is 1:1 to 1:

4.

4. The method for recovering anthraquinone from spent activated alumina using a Soxhlet extractor according to claim 1, characterized in that: In step 3, the preferred ratio of ethanol to cyclohexane in the mixed solvent is 1:3.

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