A method for treating xylene oxide residue

Abstract

This invention relates to the field of xylene oxidation residue treatment technology, specifically a method for treating xylene and m-xylene oxidation residues, comprising the following steps: S1. Pretreatment; S2. Separation; S3. Evaporation and concentration; S4. Incineration; S5. Ash dissolution; S6. Filtration; S7. Recovery of sodium carbonate and sodium bromide; S8. Bromine recovery and utilization; S9. Recovery of cobalt-manganese catalyst; S10. Precipitate treatment; S11. Recycling of cobalt-manganese catalyst; S12. Recovery and utilization of sodium carbonate. This invention uses an aqueous solution of oxalic acid and sodium carbonate to treat the xylene oxidation residue. The addition of oxalic acid effectively prevents the valence change of cobalt-manganese ions during precipitation under alkaline conditions, thereby reducing the Co content. 3+ Mn 4+ The production of [something], and the addition of oxalic acid will also react with Co. 2+ Mn 2+ The formation of cobalt manganese oxalate precipitate facilitates the recovery of cobalt and manganese catalysts. This invention enables the recovery and recycling of sodium carbonate and cobalt manganese bromine catalysts from residues, with no waste emissions.

Description

Technical Field

[0001] This invention relates to the field of xylene oxidation residue treatment technology, specifically a method for treating and recycling cobalt-manganese-bromine catalysts found in p-xylene and m-xylene oxidation residues. Background Technology

[0002] Terephthalic acid (p-xylene oxide) and isophthalic acid (m-xylene oxide) are important organic synthesis monomers in the chemical industry. Terephthalic acid (PTA) is mainly used to produce polyethylene terephthalate (PET) and bottle-grade polyester, while isophthalic acid (MTA) is mainly used to mix with terephthalic acid to produce modified polyesters such as bottle-grade polyester. Currently, China's domestic production capacity for terephthalic acid has exceeded 50 million tons, and for isophthalic acid it has exceeded 1 million tons, and this capacity is still expanding. To ensure the quality of terephthalic acid and isophthalic acid products, a portion of the mother liquor needs to be extracted during the xylene oxidation process and then sent to a thin-film evaporator to recover acetic acid. The distillation residue is discharged as waste, accounting for approximately 0.35-0.6% of the total xylene oxidation production. The main components of this residue are oxidation byproducts, organic acids, and small amounts of cobalt, manganese, heavy metals, bromides, etc. In addition, in the xylene oxidation unit, alkaline solutions are often used for cleaning to remove blockages in various equipment and pipelines. Other waste materials carried out from the site and system due to leaks, spills, drips, and other sources are also discharged into the waste collection pool. These waste residues are also discharged into the xylene oxidation waste residue system. Because the composition of these waste residues is complex, and their composition and content vary with the high-temperature oxidation process, this poses a challenge to the comprehensive recycling and utilization of the waste residues.

[0003] CN202110072703.5 discloses a comprehensive utilization process for terephthalic acid oxidation residue. This patent involves esterifying and distilling the terephthalic acid oxidation residue with octanol and other substances to obtain esters. The residue from the distillation vessel is then incinerated to obtain cobalt, manganese, and bromide salts. These are then extracted and purified to obtain cobalt sulfate and manganese sulfate. Further precipitation with sodium bicarbonate, washing, concentration, and crystallization yield cobalt acetate and manganese acetate. Sodium bromide is then dissolved, decolorized, concentrated, crystallized, and centrifuged to obtain the final sodium bromide product. This process is complex and unstable, generates large amounts of wastewater, and causes severe environmental pollution.

[0004] CN201810143964.X provides a system and method for the comprehensive utilization of terephthalic acid oxidation residue and sludge. This method recovers cobalt-manganese catalyst by incinerating terephthalic acid oxidation sludge and distillation residue. The cobalt and manganese metals contained therein are converted into cobalt-manganese oxide ash after high-temperature incineration, which is discharged from a slag cooler. The slag cooler is cooled to below 150°C using water cooling. The cooled ash, i.e., cobalt-manganese oxide, is sent to an ash storage tank for storage and packaging for sale after natural cooling. However, this method only converts the cobalt and manganese in the residue into cobalt-manganese oxide ash; it cannot be used as a catalyst and cannot recover and reuse bromine.

[0005] CN201910096370.2 provides a method for the resource-based recycling of xylene (p-xylene and m-xylene) oxidation residues. This method prepares environmentally friendly plasticizer diethylene glycol dibenzoate (DEDB) products through three steps: oxidation, extraction and esterification of the residues. The preparation process of this method is complex, generates waste emissions, does not recover bromine, and does not provide detailed information on the recovery and application of cobalt and manganese in the residues.

[0006] Therefore, there is a need to invent a green treatment method for xylene oxidation residue, optimize the recycling process, reduce or avoid wastewater discharge, and at the same time realize the recycling and reuse of cobalt, manganese and bromine catalysts. Summary of the Invention

[0007] To address the above problems, this invention provides a method for treating xylene oxidation residue.

[0008] The technical solution adopted by this invention to solve its technical problem includes the following steps:

[0009] S1. Pretreatment: Add xylene oxide residue to a mixing device, then add oxalic acid or oxalate aqueous solution and sodium carbonate aqueous solution for stirring and reaction, and adjust the pH of the solution to 7-8, controlling the solid content in the solution to 3-5%;

[0010] S2. Separation: The mixture after pretreatment in step S1 is filtered to obtain solid A and the first filtrate;

[0011] S3. Evaporation and concentration: The first filtrate obtained in step S2 is sent to a multi-effect evaporator for concentration, and the concentration of the filtrate is concentrated to a solid content of 50-70% to obtain a concentrated solution;

[0012] S4. Incineration: The concentrated liquid obtained in step S3 is sent to an incinerator for incineration to obtain ash residue. The energy generated during the incineration process is recovered.

[0013] S5. Ash and slag dissolution: Add the ash and slag obtained in step S4 to the dissolution tank, then add pure water to adjust the ash and slag concentration in the solution to 15~25% to obtain the ash and slag dissolution solution;

[0014] S6. Filtration: The ash residue solution obtained in step S5 is filtered through a filter to obtain solid B. The filtrate is then pumped to the evaporation and crystallization unit.

[0015] S7. Sodium carbonate and sodium bromide recovery: The filtrate sent to the evaporation and crystallization unit in step S6 is evaporated and crystallized. The evaporated water is recycled. Solid sodium carbonate product is separated by centrifugation. The mother liquor is recycled. When the sodium bromide content in the mother liquor reaches 30~43%, it is sent to the hydrobromic acid recovery unit to recover hydrobromic acid.

[0016] S8. Bromine recovery and utilization: The bromine-containing mother liquor from the S7 process is sent to the reaction evaporator. Phosphoric acid or sulfuric acid aqueous solution is added to the reaction evaporator, heated to boiling, and the fraction is collected to obtain crude hydrobromic acid, which is sent to the cobalt-manganese catalyst recovery unit as raw material. When no hydrobromic acid is distilled out in the reaction evaporator, the remaining liquid is cooled or evaporated to crystallize and obtain sodium hydrogen phosphate or sodium sulfate products.

[0017] S9. Recovery of cobalt-manganese catalyst: Add solid A obtained in step S2 to a mixer, add recovered dilute acetic acid or fresh acetic acid and water from the xylene oxidation unit to the mixer, heat to 80℃~boiling, maintain for 30~180min, filter while hot to obtain catalyst filtrate and solid precipitate C, and control the total cobalt and manganese content in the catalyst filtrate to be 1~6% after the reaction is completed;

[0018] S10. Solid precipitate treatment: The solid B obtained in step S6 and / or the solid precipitate C obtained in step S9 are fed into the reactor, and the hydrobromic acid recovered in step S8 or fresh hydrobromic acid and water are added to react. The molar ratio of cobalt and manganese to hydrobromic acid is 1:2.2~3.0. When the concentration of cobalt and manganese ions in the solution no longer changes or the dissolution is complete, the solution is filtered to obtain the post-treatment solution. The percentage of the sum of cobalt and manganese content in the post-treatment solution to the mass of the treatment solution is controlled at 1.5~12%.

[0019] The post-treatment liquid is transferred to a reactor containing cobalt and / or manganese, and heated for 60-240 min. After the reaction is completed, the solution is filtered to obtain the catalyst filtrate. The total mass of cobalt and / or manganese added to the reactor accounts for 5-20% of the total mass of cobalt and manganese in the post-treatment liquid.

[0020] S11. Recycling of cobalt-manganese catalyst: The catalyst filtrate obtained in steps S9 and S10 is returned to the catalyst preparation system and mixed with fresh catalyst for use.

[0021] S12. Sodium carbonate recycling: The solid sodium carbonate product separated in step S7 is added to pure water to make an aqueous solution, which is then returned to step S1 for use.

[0022] Further, in step S1, the oxalate is sodium oxalate or potassium oxalate, the mass fraction of the aqueous solution of oxalic acid or oxalate is 2.5-30%, the concentration of the aqueous solution of sodium carbonate is 20-25%, and the molar ratio of oxalic acid or oxalate to sodium carbonate is 0.001-0.0015:1.0.

[0023] Furthermore, in step S2, the solid content in the first filtrate is 3-5%. The precipitate formed at this time is beneficial for filtration and separation and reduces entrainment. At the same time, the sodium carbonate solution in this concentration range can remain stable for a long time and is convenient to use. The present invention controls the pH value to be 7-8 after the alkaline dissolution is completed. When the pH value is lower than 7, there will be insufficient dissolution or instability, and the cobalt and manganese carbonate precipitation will not be sufficient, and the cobalt and manganese metal ions will not be fully recovered. When the pH value is higher than 8, further increasing the amount of alkali has no significant effect on dissolution and cobalt and manganese precipitation, and increases the post-processing load and wastes resources.

[0024] Furthermore, pure water is added during the ash dissolution process in step S5. This pure water is the distilled water recovered from the evaporation and concentration processes in steps S3 and S7, or / and pure water from a pure water device.

[0025] Furthermore, in step S8, an aqueous solution of phosphoric acid or sulfuric acid is added, wherein the concentration of phosphoric acid is 40-98% and the concentration of sulfuric acid is 40-95%.

[0026] Furthermore, the dilute acetic acid in step S9 is derived from the recovered dilute acetic acid in the xylene oxidation unit or is prepared by mixing fresh acetic acid with the recovered dilute acetic acid. The acetic acid content in the dilute acetic acid is 25-40%, and the molar ratio of cobalt and manganese to acetic acid is 1:2.05-6.0.

[0027] Furthermore, in step S10, the solid B obtained in step S6 and the precipitate C obtained in step S9 are fed into the reactor, wherein the solid B and the precipitate C can be mixed in any proportion when used together.

[0028] Furthermore, in the post-treatment liquid obtained in step S10, the combined content of cobalt and manganese accounts for 1-6% of the mass of the treatment liquid.

[0029] Furthermore, in step S10, the total mass of cobalt and / or manganese added to the reactor accounts for 5-20% of the total mass of cobalt and manganese in the post-treatment solution. The addition of cobalt and / or manganese can react with excess hydrobromic acid in the treatment solution to increase the pH value of the solution and reduce or avoid the oxidation of bromide ions, thereby stabilizing the valence state of cobalt and manganese bromide ions in the obtained catalyst aqueous solution and giving it more stable catalytic performance.

[0030] Furthermore, the recycling of the cobalt-manganese catalyst in step S11 involves mixing the catalyst filtrate obtained in steps S9 and S10 with fresh catalyst in any proportion to obtain a cobalt-manganese-bromine mixed catalyst, which is then returned to the system for recycling.

[0031] Furthermore, in step S12, sodium carbonate recycling involves directly preparing an aqueous solution from the solid sodium carbonate separated in step S7 without drying it, and then returning it to step S1 for use.

[0032] Furthermore, in step S12, during the dissolution of solid sodium carbonate, pure water is added. This pure water is the distilled water recovered from the evaporation and concentration processes in steps S3 and S7, or / and pure water from a pure water device.

[0033] The beneficial effects of this solution are as follows: First, this invention uses an aqueous solution of oxalic acid or oxalate and an aqueous solution of sodium carbonate to treat the xylene oxidation residue. The addition of oxalic acid can effectively prevent the oxidation and valence change of cobalt and manganese ions when they precipitate in an alkaline state, thereby reducing the Co content. 3+ Mn 4+ The production of [something], and the addition of oxalic acid will also react with Co. 2+ Mn 2+ The process generates cobalt manganese oxalate precipitate, facilitating the recovery of cobalt and manganese catalysts; secondly, it converts organic matter in xylene oxidation residue into carbonates for recycling; thirdly, it achieves the recovery of cobalt, manganese, and bromine catalysts from xylene oxidation residue; fourthly, the water generated during the treatment process is recycled, with no wastewater discharge; and fifthly, the residue treatment process is green and energy-saving, with no waste discharge. Detailed Implementation

[0034] Example 1:

[0035] A method for treating p-xylene oxide residue includes the following steps:

[0036] S1. Pretreatment: Add the phthalic acid oxidation residue to the mixing device, then add oxalic acid and sodium carbonate aqueous solution and stir to react, and adjust the pH of the solution to 7, controlling the solid content in the solution to 3%; the concentration of the oxalic acid aqueous solution is 30%, the concentration of the sodium carbonate aqueous solution is 20%, and the molar ratio of oxalic acid to sodium carbonate is 1:0.001;

[0037] S2. Separation: The mixture after pretreatment in step S1 is filtered to obtain solid A and a first filtrate; the solid content in the first filtrate is 3%;

[0038] S3. Evaporation and concentration: The first filtrate obtained in step S2 is sent to a multi-effect evaporator for concentration, and the concentration of the filtrate is concentrated to a solid content of 50% to obtain a concentrated solution;

[0039] S4. Incineration: The concentrated liquid obtained in step S3 is sent to an incinerator for incineration to obtain ash residue;

[0040] S5. Ash and slag dissolution: Add the ash and slag obtained in step S4 to the dissolution tank, then add pure water to adjust the ash and slag concentration in the solution to 15% to obtain the ash and slag solution; the pure water is the pure water recovered from the distillation water device in the evaporation and concentration process of step S3;

[0041] S6. Filtration: The ash residue solution obtained in step S5 is filtered through a filter to collect solid B, and the filtrate is pumped to the evaporation and crystallization unit.

[0042] S7. Sodium carbonate and sodium bromide recovery: The filtrate sent to the evaporation and crystallization unit in step S6 is evaporated and crystallized. The water vapor generated by evaporation is condensed and recovered. Solid sodium carbonate product is continuously separated by centrifugation. The mother liquor is recycled. When the sodium bromide content in the mother liquor reaches 30%, it is sent to the hydrobromic acid recovery unit to recover hydrobromic acid.

[0043] S8. Bromine recovery and utilization: The bromine-containing mother liquor from the S7 process is fed into the reaction evaporator. 98% phosphoric acid and water are added to the reaction evaporator and heated to boiling. The distillate is collected to obtain crude hydrobromic acid, which is sent to the cobalt-manganese catalyst recovery unit as raw material. When no hydrobromic acid is distilled out in the reaction evaporator, the remaining liquid is cooled and separated to obtain sodium hydrogen phosphate product.

[0044] S9. Recovery of cobalt-manganese catalyst: The solid A obtained in step S2 is added to a mixer, dilute acetic acid and water are added to the inside of the mixer, the mixture is heated to boiling and kept for 180 min, and then filtered while hot to obtain catalyst filtrate and solid precipitate C; wherein the cobalt and manganese contents in the catalyst filtrate are 3.15% and 2.81%, respectively.

[0045] The dilute acetic acid is recovered from the xylene oxidation unit. The dilute acetic acid in step S9 has an acetic acid content of 25%, and the molar ratio of cobalt and manganese to acetic acid is 1:2.05.

[0046] S10. Solid precipitate treatment: Solid B obtained in step S6 and solid precipitate C obtained in step S9 are mixed in any proportion and fed into a reactor. Hydrobromic acid and water recovered in step S7 are added to react, wherein the molar ratio of cobalt and manganese to hydrobromic acid is 1:2.2. When the concentration of cobalt and manganese ions in the solution no longer changes, a post-treatment solution is obtained, wherein the cobalt and manganese content is 6.71% and 5.33%, respectively.

[0047] The post-treatment liquid was transferred into a reactor containing cobalt metal, wherein the amount of cobalt metal was 5% of the total mass of cobalt and manganese in the added post-treatment liquid. The reaction was heated for 2 hours, and after the reaction was completed, it was filtered to obtain the catalyst filtrate.

[0048] S11. Recycling of cobalt-manganese catalyst: The catalyst filtrate obtained in steps S9 and S10 is returned to the catalyst preparation system and mixed with fresh catalyst for use, wherein the catalyst filtrate and fresh catalyst are mixed in any proportion.

[0049] S12. Sodium carbonate recycling: The solid sodium carbonate product separated in step S7 is directly converted into an aqueous solution and returned to step S1 for use without drying. The water added is the condensate from the evaporation in steps S3 and S7.

[0050] Example 2:

[0051] A method for treating m-xylene oxidation residue includes the following steps:

[0052] S1. Pretreatment: Add the m-xylene oxide residue to the mixing device, then add sodium oxalate aqueous solution and sodium carbonate aqueous solution for stirring and reaction, and adjust the pH of the solution to 8, controlling the solid content in the solution to 5%; the mass fraction of the sodium oxalate aqueous solution is 2.5%, the concentration of the sodium carbonate aqueous solution is 25%, and the molar ratio of sodium oxalate to sodium carbonate is 0.0015:1;

[0053] S2. Separation: The mixture after pretreatment in step S1 is filtered to obtain solid A and a first filtrate; the solid content in the first filtrate is 5%;

[0054] S3. Evaporation and concentration: The first filtrate obtained in step S2 is sent to a multi-effect evaporator for concentration, and the concentration of the filtrate is concentrated to a solid content of 70% to obtain a concentrated solution;

[0055] S4. Incineration: The concentrated liquid obtained in step S3 is sent to an incinerator for incineration to obtain ash residue;

[0056] S5. Ash and slag dissolution: Add the ash and slag obtained in step S4 to the dissolution tank, then add pure water to adjust the ash and slag concentration in the solution to 25% to obtain the ash and slag dissolution solution; the pure water is pure water from the pure water device;

[0057] S6. Filtration: The ash residue solution obtained in step S5 is filtered through a filter to collect solid B, and the filtrate is pumped to the evaporation and crystallization unit.

[0058] S7. Sodium carbonate and sodium bromide recovery: The filtrate sent to the evaporation and crystallization unit in step S6 is evaporated and crystallized, and solid sodium carbonate product is separated by centrifugation. The mother liquor is recycled. When the sodium bromide content in the mother liquor reaches 43%, it is sent to the hydrobromic acid recovery unit to recover hydrobromic acid.

[0059] S8. Bromine recovery and utilization: The bromine-containing mother liquor from the S7 process is fed into the reaction evaporator. 95% sulfuric acid and water are added to the reaction evaporator and heated to boiling. The distillate is collected to obtain crude hydrobromic acid, which is sent to the cobalt-manganese catalyst recovery unit as raw material. When no hydrobromic acid is distilled out in the reaction evaporator, the remaining liquid is cooled and separated to obtain sodium sulfate product.

[0060] S9. Recovery of cobalt-manganese catalyst: The solid A obtained in step S2 is added to a mixer, dilute acetic acid and water are added to the inside of the mixer, the mixture is heated to 80°C and kept for 30 minutes, and then filtered while hot to obtain catalyst filtrate and solid precipitate C; wherein the cobalt and manganese contents in the catalyst filtrate are 0.53% and 0.52%, respectively.

[0061] The dilute acetic acid is recovered from the xylene oxidation unit. The dilute acetic acid in step S9 has an acetic acid content of 40%, and the molar ratio of cobalt and manganese to acetic acid is 1:6.0.

[0062] S10. Solid precipitate treatment: Solid B obtained in step S6 and solid precipitate C obtained in step S9 are mixed in any proportion and fed into a reactor. Fresh hydrobromic acid and water are added to carry out the reaction. The molar ratio of cobalt and manganese to hydrobromic acid is 1:3.0. When the concentration of cobalt and manganese ions in the solution no longer changes, a post-treatment solution is obtained, in which cobalt and manganese are 4.42% and 4.35%, respectively.

[0063] The post-treatment liquid was transferred into a reactor containing metallic manganese, wherein the amount of metallic manganese was 15% of the total mass of cobalt and manganese in the added post-treatment liquid. The reaction was heated for 4 hours, and after the reaction was completed, it was filtered to obtain the catalyst filtrate.

[0064] S11. Recycling of cobalt-manganese catalyst: The catalyst filtrate obtained in steps S9 and S10 is returned to the catalyst preparation system and mixed with fresh catalyst for use; wherein the catalyst filtrate and fresh catalyst are mixed in any proportion.

[0065] S12. Sodium carbonate recycling: The solid sodium carbonate product separated in step S7 is directly converted into an aqueous solution and returned to step S1 for use without drying. The water added is the condensate from the evaporation in steps S3 and S7.

[0066] Example 3:

[0067] A method for treating xylene oxidation residue includes the following steps:

[0068] S1. Pretreatment: The p-xylene oxide residue is added to a mixing device, then oxalic acid aqueous solution and sodium carbonate aqueous solution are added and stirred to react. The pH value of the solution is adjusted to 7.5, and the solid content in the solution is controlled to be 4%. The mass fraction of the oxalic acid aqueous solution is 10%, the concentration of the sodium carbonate aqueous solution is 22%, and the molar ratio of oxalic acid to sodium carbonate is 0.0012:1.

[0069] S2. Separation: The mixture after pretreatment in step S1 is filtered to obtain solid A and a first filtrate; the solid content of the first filtrate is 4%.

[0070] S3. Evaporation and concentration: The first filtrate obtained in step S2 is sent to a multi-effect evaporator for concentration, and the concentration of the filtrate is concentrated to a solid content of 60% to obtain a concentrated solution;

[0071] S4. Incineration: The concentrated liquid obtained in step S3 is sent to an incinerator for incineration to obtain ash residue;

[0072] S5. Ash and slag dissolution: Add the ash and slag obtained in step S4 to the dissolution tank, then add pure water to adjust the ash and slag concentration in the solution to 20% to obtain the ash and slag dissolution solution; the pure water is a mixture of distilled water recovered from the evaporation process in steps S3 and S7 and pure water from the pure water device;

[0073] S6. Filtration: The ash residue solution obtained in step S5 is filtered through a filter to collect solid B, and the filtrate is pumped to the evaporation and crystallization unit.

[0074] S7. Sodium carbonate and sodium bromide recovery: The filtrate sent to the evaporation and crystallization unit in step S6 is evaporated and crystallized, and solid sodium carbonate product is continuously separated by centrifugation. The mother liquor is recycled. When the sodium bromide content in the mother liquor reaches 35%, it is sent to the hydrobromic acid recovery unit to recover hydrobromic acid.

[0075] S8. Bromine recovery and utilization: The bromine-containing mother liquor from the S7 process is fed into the reaction evaporator. 40% sulfuric acid and water are added to the reaction evaporator and heated to boiling. The distillate is collected to obtain crude hydrobromic acid, which is sent to the cobalt-manganese catalyst recovery unit as raw material. When no hydrobromic acid is distilled out in the reaction evaporator, the remaining liquid is cooled and separated to obtain sodium sulfate product.

[0076] S9. Recovery of cobalt-manganese catalyst: The solid A obtained in step S2 is added to a mixer, dilute acetic acid and water are added to the inside of the mixer, the mixture is heated to 90°C and kept for 90 min, and then filtered while hot to obtain catalyst filtrate and solid precipitate C; wherein the cobalt and manganese contents in the catalyst filtrate are 2.94% and 2.62%, respectively.

[0077] The dilute acetic acid is recovered from the xylene oxidation unit. The dilute acetic acid in step S9 has an acetic acid content of 35%, and the molar ratio of cobalt and manganese to acetic acid is 1:4.0.

[0078] S10. Solid precipitate treatment: Solid B obtained in step S6 and solid precipitate C obtained in step S9 are mixed in any proportion and fed into a reactor. Hydrobromic acid and water recovered in step S7 are added to react, wherein the molar ratio of cobalt and manganese to hydrobromic acid is 1:2.5. When the concentration of cobalt and manganese ions in the solution no longer changes, a post-treatment solution is obtained, wherein the cobalt and manganese are 0.82% and 0.66%, respectively.

[0079] The post-treatment liquid was transferred into a reactor containing cobalt and manganese, wherein the amount of cobalt was 10% of the total mass of cobalt and manganese in the post-treatment liquid, and the amount of manganese was 10% of the total mass of cobalt and manganese in the post-treatment liquid. The reaction was heated for 60 minutes, and after the reaction was completed, the mixture was filtered to obtain the catalyst filtrate.

[0080] S11. Recycling of cobalt-manganese catalyst: The catalyst filtrate obtained in steps S9 and S10 is returned to the catalyst preparation system and mixed with fresh catalyst for use; wherein the catalyst filtrate and fresh catalyst are mixed in any proportion.

[0081] S12. Sodium carbonate recycling: The solid sodium carbonate product separated in step S7 is directly converted into an aqueous solution and returned to step S1 for use without drying. The water added is the condensate from the evaporation in steps S3 and S7.

[0082] Example 4:

[0083] A method for treating xylene oxidation residue includes the following steps:

[0084] S1. Pretreatment: The p-xylene oxide residue is added to a mixing device, then potassium oxalate aqueous solution and sodium carbonate aqueous solution are added and stirred to react. The pH of the solution is adjusted to 7, and the solid content in the solution is controlled to be 4%. The mass fraction of the potassium oxalate aqueous solution is 15%, the concentration of the sodium carbonate aqueous solution is 20%, and the molar ratio of potassium oxalate to sodium carbonate is 0.0012:1.

[0085] S2. Separation: The mixture after pretreatment in step S1 is filtered to obtain solid A and a first filtrate; the solid content of the first filtrate is 5%.

[0086] S3. Evaporation and concentration: The first filtrate obtained in step S2 is sent to a multi-effect evaporator for concentration, and the concentration of the filtrate is concentrated to a solid content of 68% to obtain a concentrated solution;

[0087] S4. Incineration: The concentrated liquid obtained in step S3 is sent to an incinerator for incineration to obtain ash residue;

[0088] S5. Ash and slag dissolution: Add the ash and slag obtained in step S4 to the dissolution tank, then add pure water to adjust the ash and slag concentration in the solution to 20% to obtain the ash and slag dissolution solution; the pure water is a mixture of distilled water recovered from the evaporation process in steps S3 and S7 and pure water from the pure water device;

[0089] S6. Filtration: The ash residue solution obtained in step S5 is filtered through a filter to collect solid B, and the filtrate is pumped to the evaporation and crystallization unit.

[0090] S7. Sodium carbonate and sodium bromide recovery: The filtrate sent to the evaporation and crystallization unit in step S6 is evaporated and crystallized, and solid sodium carbonate product is continuously separated by centrifugation. The mother liquor is recycled. When the sodium bromide content in the mother liquor reaches 35%, it is sent to the hydrobromic acid recovery unit to recover hydrobromic acid.

[0091] S8. Bromine recovery and utilization: The bromine-containing mother liquor from the S7 process is sent to the reaction evaporator. 40% phosphoric acid and water are added to the reaction evaporator and heated to boiling. The distillate is collected to obtain crude hydrobromic acid, which is sent to the cobalt-manganese catalyst recovery unit as raw material. When no hydrobromic acid is distilled out in the reaction evaporator, the remaining liquid is cooled and separated to obtain sodium hydrogen phosphate product.

[0092] S9. Recovery of cobalt-manganese catalyst: The solid A obtained in step S2 is added to a mixer, dilute acetic acid and water are added to the inside of the mixer, the mixture is heated to 90°C and kept for 60 min, and then filtered while hot to obtain catalyst filtrate and solid precipitate C; wherein the cobalt and manganese contents in the catalyst filtrate are 2.71% and 2.41%, respectively.

[0093] The dilute acetic acid is recovered from the xylene oxidation unit. The dilute acetic acid in step S9 has an acetic acid content of 25%, and the molar ratio of cobalt and manganese to acetic acid is 1:3.0.

[0094] S10. Solid precipitate treatment: Solid B obtained in step S6 and solid precipitate C obtained in step S9 are mixed in any proportion and fed into a reactor. Hydrobromic acid and water recovered in step S7 are added to react, wherein the molar ratio of cobalt and manganese to hydrobromic acid is 1:2.25. When the concentration of cobalt and manganese ions in the solution no longer changes, a post-treatment solution is obtained, wherein the cobalt and manganese are 0.82% and 0.66%, respectively.

[0095] The post-treatment liquid was transferred into a reactor containing metallic manganese, wherein the amount of metallic manganese was 5% of the total mass of cobalt and manganese in the added post-treatment liquid. The reaction was heated for 90 minutes. After the reaction was completed, the solution was filtered to obtain the catalyst filtrate.

[0096] S11. Recycling of cobalt-manganese catalyst: The catalyst filtrate obtained in steps S9 and S10 is returned to the catalyst preparation system and mixed with fresh catalyst for use; wherein the catalyst filtrate and fresh catalyst are mixed in any proportion.

[0097] S12. Sodium carbonate recycling: The solid sodium carbonate product separated in step S7 is directly converted into an aqueous solution and returned to step S1 for use without drying. The water added is the condensate from the evaporation in steps S3 and S7.

[0098] The above-described specific embodiments are merely specific examples of the present invention. The patent protection scope of the present invention includes, but is not limited to, the product form and style of the above-described specific embodiments. Any xylene oxide residue treatment method that conforms to the claims of the present invention and any appropriate changes or modifications made thereto by those skilled in the art should fall within the patent protection scope of the present invention.

Claims

1. A method for treating xylene oxidation residue, characterized in that: Includes the following steps: S1. Pretreatment: Add xylene oxide residue to a mixing device, then add oxalic acid or oxalate aqueous solution and sodium carbonate aqueous solution for stirring and reaction, and adjust the pH of the solution to 7-8, controlling the solid content in the solution to 3-5%; S2. Separation: The mixture after pretreatment in step S1 is filtered to obtain solid A and the first filtrate; S3. Evaporation and concentration: The first filtrate obtained in step S2 is sent to a multi-effect evaporator for concentration, and the concentration of the filtrate is concentrated to a solid content of 50-70% to obtain a concentrated solution; S4. Incineration: The concentrated liquid obtained in step S3 is sent to an incinerator for incineration to obtain ash residue; S5. Ash and slag dissolution: Add the ash and slag obtained in step S4 to the dissolution tank, then add pure water to adjust the ash and slag concentration in the solution to 15~25% to obtain the ash and slag dissolution solution; S6. Filtration: The ash residue solution obtained in step S5 is filtered through a filter to obtain solid B. The filtrate is pumped to the evaporation and crystallization unit. S7. Sodium carbonate and sodium bromide recovery: The filtrate sent to the evaporation and crystallization unit in step S6 is evaporated and crystallized, and solid sodium carbonate product is separated by centrifugation. The mother liquor is recycled. When the sodium bromide content in the mother liquor reaches 30~43%, the mother liquor is sent to the hydrobromic acid recovery unit to recover hydrobromic acid. S8. Bromine Recovery and Utilization: The bromine-containing mother liquor from process S7 is fed into a reaction evaporator. Phosphoric acid or sulfuric acid aqueous solution is added to the reaction evaporator and heated to boiling. The fraction collected yields crude hydrobromic acid, which is sent to the cobalt-manganese catalyst recovery unit used for step S9 cobalt-manganese catalyst recovery and step S10 solid precipitate treatment as raw material. This raw material is used for the subsequent dissolution of solid precipitates. When no hydrobromic acid is distilled off in the reaction evaporator, the remaining liquid is cooled, evaporated, and crystallized to obtain sodium hydrogen phosphate or sodium sulfate products. S9. Recovery of cobalt-manganese catalyst: Add solid A obtained in step S2 to a mixer, add recovered dilute acetic acid or fresh acetic acid and water from the xylene oxidation unit to the inside of the mixer, heat to 80℃ to boiling, maintain for 30 to 180 min, filter while hot to obtain catalyst filtrate and solid precipitate C, and control the total cobalt and manganese content in the catalyst filtrate to be 1 to 6% after the reaction is completed; S10. Solid Precipitate Treatment: This step is the core operation of the cobalt-manganese catalyst recovery unit. The solid B obtained in step S6 and / or the solid precipitate C obtained in step S9 are fed into the reactor, and the hydrobromic acid recovered in step S8 or fresh hydrobromic acid and water are added to react. The molar ratio of cobalt-manganese to hydrobromic acid is 1:2.2~3.

0. When the concentration of cobalt-manganese ions in the solution no longer changes or the dissolution is complete, a post-treatment solution is obtained. The total cobalt-manganese content in the post-treatment solution is controlled to be 1.5~12%. The post-treatment liquid was transferred into a reactor containing cobalt and / or manganese, and heated for 60-240 min. After the reaction was completed, the solution was filtered to obtain the catalyst filtrate. S11. Recycling of cobalt-manganese catalyst: The catalyst filtrate obtained in steps S9 and S10 is returned to the catalyst preparation system and mixed with fresh catalyst for reuse. S12. Sodium carbonate recycling: The solid sodium carbonate product separated in step S7 is made into an aqueous solution and returned to step S1 for use.

2. The method for treating xylene oxidation residue according to claim 1, characterized in that: In step S1, the oxalate is sodium oxalate or potassium oxalate, the mass fraction of the aqueous solution of oxalic acid or oxalate is 2.5-30%, the concentration of the aqueous solution of sodium carbonate is 20-25%, and the molar ratio of oxalic acid or oxalate to sodium carbonate is 0.001-0.0015:1.

0.

3. The method for treating xylene oxidation residue according to claim 1, characterized in that: In step S2, the solid content in the first filtrate is 3-5%.

4. The method for treating xylene oxidation residue according to claim 1, characterized in that: In step S5, pure water is added during the ash dissolution process. This pure water is the distilled water recovered from the evaporation and concentration process in step S3 or / and pure water from a pure water device.

5. The method for treating xylene oxidation residue according to claim 1, characterized in that: In step S9, the dilute acetic acid contains 25-40% acetic acid, and the molar ratio of cobalt and manganese to acetic acid is 1:2.05-6.

0.

6. The method for treating xylene oxidation residue according to claim 1, characterized in that: In step S8, an aqueous solution of phosphoric acid or sulfuric acid is added, wherein the concentration of phosphoric acid is 40-98% and the concentration of sulfuric acid is 40-95%.

7. The method for treating xylene oxidation residue according to claim 1, characterized in that: In step S10, the total mass of cobalt and / or manganese metal added to the reactor accounts for 5-20% of the total mass of cobalt and manganese in the post-treatment solution.

8. The method for treating xylene oxidation residue according to claim 1, characterized in that: The recycling of the cobalt-manganese catalyst in step S11 involves mixing the catalyst filtrate obtained in steps S9 and S10 with fresh catalyst to obtain a cobalt-manganese-bromine mixed catalyst, which is then returned to the system for recycling.

9. The method for treating xylene oxidation residue according to claim 1, characterized in that: The sodium carbonate recycling step S12 involves directly preparing an aqueous solution from the solid sodium carbonate separated in step S7 without drying it and returning it to step S1 for use.

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