An additive and a method for inhibiting decomposition of methionine in methionine production using the same

Abstract

The application belongs to the technical field of fine chemical industry and relates to an additive and a method for inhibiting methionine decomposition in methionine production by using the additive. The additive contains 1-5 parts of a hindered phenol antioxidant and 1 part of a metal chelating agent in terms of weight ratio. After the additive is added into methionine crystallization mother liquor and / or hydrolysis liquor, the additive can inhibit methionine oxidative cleavage, greatly reduce dimethyl disulfide output, and is compatible with the existing mother liquor impurity catalytic hydrolysis process, and product quality and total yield are improved.

Description

Technical Field

[0001] This invention belongs to the field of fine chemical technology and relates to an additive and a method for inhibiting the decomposition of methionine during methionine production. Background Technology

[0002] DL-methionine is an essential sulfur-containing amino acid for animals and humans. It is the first limiting amino acid in animal feed, and its addition to livestock, poultry, and aquatic diets can balance nutrition and improve protein conversion rates. DL-methionine is also widely used in food fortification, pharmaceutical preparations, and fine chemical synthesis.

[0003] Currently, the industrial production of DL-methionine mainly adopts the hydantoin process, which commonly uses sodium / potassium salt processes: In the sodium salt process, hydantoin is generated from cyanohydrin, ammonia, and carbon dioxide. Hydantoin undergoes ring-opening decomposition under the action of sodium hydroxide to produce a saponified solution of sodium methionine and sodium carbonate. The saponified solution is neutralized with sulfuric acid to crystallize and produce methionine. The sodium sulfate mother liquor containing methionine is concentrated at high temperature to precipitate a large amount of sodium sulfate (the solubility of methionine increases with increasing temperature, while the solubility of sodium sulfate decreases with increasing temperature). After filtration, the mother liquor is returned to the sulfuric acid acidification section. In the potassium salt process, hydantoin is generated from cyanohydrin, ammonia, and carbon dioxide. Hydantoin undergoes ring-opening decomposition under the action of potassium hydroxide or potassium carbonate to produce potassium methionine. The potassium methionine is neutralized with carbon dioxide to produce methionine and potassium bicarbonate. The separated potassium bicarbonate mother liquor is concentrated at high temperature to produce potassium carbonate, which is returned to the hydantoin hydrolysis section to continue hydrolysis.

[0004] However, in the industrial production of DL-methionine using the hydantoin process, regardless of whether the sodium or potassium salt process is employed, 2-5% of unprecipitated methionine, methionine dipeptides and tripeptides, diketopiperazine, as well as sulfates / carbonates and organic formates remain in the crystallization mother liquor. To improve the overall yield and reduce material loss, the crystallization mother liquor is typically subjected to long-term closed-loop circulation and multiple high-temperature concentrations in industry. This is an indispensable and crucial step in the hydantoin-process methionine production.

[0005] CN106349131A first studied the thermal decomposition mechanism of methionine. Using gas chromatography-mass spectrometry (GC-MS), it was confirmed that the products of methionine thermal decomposition are dimethyl disulfide, acrylamide, 3-methylthiopropylamine, and carbon dioxide. The mechanism is as follows: upon heating, methionine first undergoes decarboxylation to decompose into 3-methylthiopropylamine and carbon dioxide. Further heating of 3-methylthiopropylamine decomposes it into dimethyl disulfide and acrylamide (see [link to CN106349131A]). Figure 1 In response to the thermal decomposition mechanism of methionine, CN106349131A introduced a two-stage electrodialysis coupled desalination process using a homogeneous membrane and a heterogeneous membrane. This process addresses three major industry pain points: high-temperature decomposition of methionine mother liquor from the hydantoin process, malodorous pollution, and impurity accumulation. It replaces the traditional thermal concentration process with electrodialysis technology, taking into account product yield, purity, and environmental protection requirements.

[0006] CN104693082A addresses the challenges of mother liquor separation and thermal deterioration in methionine production via the hydantoin process (NaOH hydrolysis route). It proposes a combined process of low-temperature concentration and ion exchange chromatography, which relies on physical separation to replace the traditional high-temperature salt extraction process. This effectively suppresses the generation of malodorous substances such as dimethyl disulfide, while achieving high yield and high purity of methionine and resource utilization of by-product salts.

[0007] CN102827045A utilizes a specific adsorbent to remove organic impurities from the secondary methionine mother liquor, reducing the accumulation of impurities in the mother liquor and decreasing the amount of mother liquor discharged as waste, thereby increasing the methionine yield.

[0008] Therefore, on the one hand, the existing method of using reduced pressure low-temperature concentration to replace the traditional atmospheric pressure high-temperature cooking can reduce the thermal decomposition rate of methionine to a certain extent. However, the low-temperature concentration equipment requires large investment and the vacuum system has high energy consumption. Moreover, transition metal ions such as iron, copper, and nickel introduced by equipment corrosion and raw materials in the mother liquor will still catalyze the oxidation reaction, and dimethyl disulfide will continue to be generated. This can only alleviate the problem but cannot eliminate it. On the other hand, chromatography and electrodialysis devices avoid the thermal decomposition problem of methionine caused by repeated high-temperature purification. However, their core is the separation of inorganic salts, and the initial equipment investment is high, and the membrane / resin maintenance cost is high, making them unsuitable for prevention and control in all stages of the process. Thirdly, the high-temperature incineration + alkaline washing desulfurization treatment for the generated odorous sulfide waste liquid is an end-of-pipe remedial measure. Not only is the incineration process energy-intensive and further causes methionine material loss, but it also generates secondary pollutants. This is a temporary solution and cannot solve the core problem of methionine decomposition in the mother liquor and the deterioration of product quality.

[0009] In summary, existing technologies for addressing methionine decomposition in methionine crystallization mother liquor and / or hydrolysate suffer from drawbacks such as limited functionality, poor adaptability to operating conditions, low control efficiency, and high operating costs. Actual industrial production urgently needs a novel method to inhibit methionine decomposition in methionine crystallization mother liquor and / or hydrolysate that is adaptable to high-temperature circulating conditions of methionine mother liquor or methionine hydrolysis conditions, combines the dual effects of passivating metal ions and capturing free radicals, thereby inhibiting the generation of malodorous substances from methionine decomposition, and possesses strong process compatibility and low cost. Summary of the Invention

[0010] The primary objective of this invention is to provide an additive that, when added to methionine crystallization mother liquor and / or hydrolysate, inhibits the oxidative cracking of methionine, significantly reduces the production of dimethyl disulfide, and is compatible with existing mother liquor impurity catalytic hydrolysis processes, thereby improving product quality and overall yield.

[0011] To achieve this objective, in a basic implementation, the present invention provides an additive containing, by weight, 1-5 parts of a hindered phenolic antioxidant and 1 part of a metal chelating agent.

[0012] In a preferred embodiment, the present invention provides an additive wherein the hindered phenolic antioxidant is selected from one or more of Irganox 1010, Irganox 1076, Irganox 1135, Irganox 1330, Irganox PS 800, Irganox 1098, Irganox 245, Irganox 245-DW, 2,6-di-tert-butyl-p-cresol (BHT), butylated hydroxyanisole (BHA), and tert-butylhydroquinone (TBHQ).

[0013] In a preferred embodiment, the present invention provides an additive wherein the metal chelating agent is selected from EDTA and / or phytic acid.

[0014] In a preferred embodiment, the present invention provides an additive wherein the EDTA is selected from one or more of EDTA acid, disodium EDTA, trisodium EDTA, and tetrasodium EDTA.

[0015] In a preferred embodiment, the present invention provides an additive, wherein the metal chelating agent is obtained by compounding EDTA and phytic acid in a mass ratio of 1:0.2-2, so as to balance the depth of heavy metal chelation and high-temperature hydrolysis resistance.

[0016] The second objective of this invention is to provide a method for inhibiting the decomposition of methionine during methionine production, which can suppress the oxidative cracking of methionine, significantly reduce the production of dimethyl disulfide, and is compatible with existing mother liquor impurity catalytic hydrolysis processes, thereby improving product quality and overall yield.

[0017] To achieve this objective, in a basic implementation, the present invention provides a method for inhibiting the decomposition of methionine during methionine production, wherein the method involves adding the additives described above to the hydrolysis section and / or the crystallization mother liquor recycling section of methionine production.

[0018] In a preferred embodiment, the present invention provides a method for inhibiting the decomposition of methionine during methionine production, wherein the total concentration of the hindered phenolic antioxidant after addition is 0.01-0.3 wt%, and the total concentration of the metal chelating agent after addition is 0.01-0.15 wt%.

[0019] In a preferred embodiment, the present invention provides a method for inhibiting the decomposition of methionine during methionine production, wherein the additive is added to the feed of the hydantoin hydrolysis tower for methionine production, and the reaction temperature of the hydrolysis tower is controlled at 140-200°C and the reaction pressure is 0.5-1.3 MPa.

[0020] In a preferred embodiment, the present invention provides a method for inhibiting the decomposition of methionine during methionine production, wherein the additive is added to the decarbonization feed of the crystallization mother liquor during methionine production, and the reaction temperature of the decarbonization of the crystallization mother liquor is controlled at 120-180°C and the reaction pressure is 0.1-0.8 MPa.

[0021] In a preferred embodiment, the present invention provides a method for inhibiting the decomposition of methionine during methionine production, wherein the additive is added to the pipeline of the methionine production crystallization mother liquor after decarbonization and return to the hydantoin hydrolysis tower.

[0022] The beneficial effects of the present invention are that, after the additive of the present invention is added to the methionine crystallization mother liquor and / or hydrolysate, it can inhibit the oxidative cracking of methionine, significantly reduce the production of dimethyl disulfide, and at the same time be compatible with the existing mother liquor impurity catalytic hydrolysis process, thereby improving product quality and total yield.

[0023] This invention relates to the stabilization and recycling of mother liquor and the reduction of odorous sulfides in the industrial production of methionine. In particular, it relates to the addition of an additive composed of multiple hindered phenols and a composite chelating agent to the hydantoin hydrolysis section or the mother liquor recycling section of crystallization, which plays a synergistic stabilizing role. This additive inhibits the decomposition of methionine through a dual pathway of "blocking metal catalysis and capturing sulfur free radicals", effectively reducing the heat loss of methionine, significantly alleviating the off-odor in production, improving environmental protection, and demonstrating outstanding value for industrial application.

[0024] Therefore, the additive of the present invention, when added to the methionine crystallization mother liquor and / or hydrolysate, effectively reduces the content of dimethyl disulfide (DMDS), thereby reducing heat loss from methionine and improving the color of the mother liquor. This effectively reduces the impact of off-odors on methionine production and is suitable for continuous methionine production. Consequently, the method of the present invention is simple, low-cost, and possesses extremely high industrial value.

[0025] The beneficial effects of this invention are specifically reflected in: (1) Dual inhibition mechanism with outstanding odor suppression efficiency: The hindered phenol multi-component synergistic capture of sulfur free radicals, EDTA + phytic acid compound chelating agent passivates metal ions, and the dual blocking of the methionine oxidation to dimethyl disulfide pathway, the sulfide reduction rate can reach 82-92%, which is better than the single additive system.

[0026] (2) Wide range of working conditions: covering high temperature hydrolysis (150-200℃), low temperature refining (120-150℃), high metal impurities, and multiple circulation mother liquor scenarios; the ratio of hindered phenol antioxidant to metal chelating agent can be flexibly adjusted.

[0027] (3) Perfectly compatible with existing mother liquor impurity removal process: The stable system pH is adapted to 4.5-6.5, which can simultaneously complete impurity conversion and oxidation suppression and deodorization without the need for additional independent reaction equipment.

[0028] (4) Green recycling and low loss: The amount of additives added is low, and no inorganic salt impurities that are difficult to remove are introduced. The mother liquor can be completely recycled in a closed loop, with no increase in solid waste or waste liquid. The stable system does not destroy the structure of methionine, and the thermal oxidation loss of methionine is less than 0.8%. Attached Figure Description

[0029] Figure 1 This is a diagram illustrating the thermal decomposition mechanism of methionine. Detailed Implementation

[0030] To better understand the technical solutions and advantages of the present invention, the present invention will be further illustrated below through embodiments.

[0031] The small-scale experiments in Examples 1-9 and Comparative Examples 1-6 below first simulated actual industrial production to obtain the optimal additive ratio, with temperature and reaction time consistent with the industrial continuous process. The standard raw material was industrial methionine circulating crystallization mother liquor (initial basic indicators: methionine monomer content 3.2 wt%; DMDS content 1120 mg / L after blank high-temperature treatment, as detected by HPLC). A uniform 1000 g of methionine circulating crystallization mother liquor was added. After the additive was added to the methionine circulating crystallization mother liquor, the mixture was stirred for 15 min. After thorough stirring, the mixture was kept at 140 ℃ for 3 h. After cooling, samples were taken to detect the DMDS concentration and methionine content, thereby calculating the DMDS reduction rate and methionine monomer loss (methionine monomer loss is the proportion of methionine monomer decomposition loss at 140 ℃ high-temperature cycling; methionine monomer loss = (methionine monomer content in the mother liquor before 140 ℃ high-temperature treatment - methionine monomer content in the mother liquor after 140 ℃ high-temperature treatment) / methionine monomer content in the mother liquor before 140 ℃ high-temperature treatment × 100%).

[0032] Example 1: Hindered phenolic antioxidant: Irganox 1010 0.6 g (total 0.06wt%) was added to the mother liquor; metal chelating agents: EDTA acid 0.1 g and phytic acid 0.1 g (total 0.02wt%, EDTA acid to phytic acid 1:1); the total mass of hindered phenolic antioxidant to the total mass of metal chelating agent was 3:1.

[0033] Test results: DMDS reduction rate 75.1%; methionine monomer loss 0.86%.

[0034] Example 2: Hindered phenolic antioxidant: Irganox 1010 0.9 g (total 0.09wt%) was added to the mother liquor; metal chelating agents: EDTA acid 0.17 g and phytic acid 0.17 g (total 0.034wt%, EDTA acid to phytic acid 1:1) were added; the total mass of hindered phenolic antioxidant: total mass of metal chelating agent = 2.65:1.

[0035] Test results: DMDS reduction rate 80.6%; methionine monomer loss 0.81%.

[0036] Example 3: Hindered phenolic antioxidant: Irganox 1010 1.2 g (total 0.12wt%) was added to the mother liquor; metal chelating agents: EDTA acid 0.25 g and phytic acid 0.25 g (total 0.05wt%, EDTA acid to phytic acid 1:1); the total mass of hindered phenolic antioxidant to the total mass of metal chelating agent = 2.4:1.

[0037] Test results: DMDS reduction rate 86.8%; methionine monomer loss 0.61%.

[0038] Example 4: The hindered phenolic antioxidant Irganox 1010 1.5 g (total 0.15wt%) was added to the mother liquor; metal chelating agents EDTA acid 0.33 g and phytic acid 0.33 g (total 0.066wt%, EDTA acid to phytic acid 1:1) were added; the total mass of hindered phenolic antioxidant to the total mass of metal chelating agent = 2.27:1.

[0039] Test results: DMDS reduction rate 87.5%; methionine monomer loss 0.58%.

[0040] Example 5: Hindered phenolic antioxidant: Irganox 1098 1.2 g (total 0.12wt%) was added to the mother liquor; metal chelating agents: EDTA acid 0.25 g and phytic acid 0.25 g (total 0.05wt%, EDTA acid to phytic acid 1:1) were added; the total mass of hindered phenolic antioxidant: total mass of metal chelating agent = 2.4:1.

[0041] Test results: DMDS reduction rate averaged 87%; methionine monomer loss was 0.63%.

[0042] Example 6: The hindered phenolic antioxidant Irganox1076 1.2 g (0.12wt%) was added to the mother liquor; metal chelating agents EDTA acid 0.25 g and phytic acid 0.25 g (total 0.05wt%, EDTA acid to phytic acid 1:1) were added; the total mass of hindered phenolic antioxidant to the total mass of metal chelating agent = 2.4:1.

[0043] Test results: DMDS reduction rate 86.7%; methionine monomer loss 0.64%.

[0044] Example 7: Hindered phenolic antioxidant TBHQ 1.2 g (0.12wt%) was added to the mother liquor; metal chelating agents EDTA acid 0.25 g and phytic acid 0.25 g (total 0.05wt%, EDTA acid to phytic acid 1:1) were added; the total mass of hindered phenolic antioxidant to the total mass of metal chelating agent was 2.4:1.

[0045] Test results: DMDS reduction rate 86.6%; methionine monomer loss 0.61%.

[0046] Example 8: The mother liquor was supplemented with hindered phenolic antioxidant Irganox 1010 1.2 g (0.12wt%); and metal chelating agents EDTA acid 0.2 g and phytic acid 0.3 g (total 0.05wt%, EDTA acid to phytic acid 0.67:1); the ratio of total hindered phenolic antioxidant to total metal chelating agent was 2.4:1.

[0047] Test results: DMDS reduction rate 86.3%; methionine monomer loss 0.63%.

[0048] Example 9: The mother liquor was supplemented with hindered phenolic antioxidant Irganox1076 1.2 g (0.12wt%); and metal chelating agents EDTA acid 0.3 g and phytic acid 0.2 g (total 0.05wt%, EDTA acid to phytic acid 1.5:1); the total mass of hindered phenolic antioxidant to the total mass of metal chelating agent was 2.4:1.

[0049] Test results: DMDS reduction rate 86.7%; methionine monomer loss 0.65%.

[0050] Comparative Example 1: No hindered phenolic antioxidants or metal chelating agents were added to 1000g of mother liquor. The mixture was stirred for 15 min and then kept at 140℃ for 3 h. Test results: DMDS reduction rate 0%; methionine monomer loss 2.73%.

[0051] Comparative Example 2: Add 1.2 g (0.12wt%) of Irganox1010 to 1000 g of mother liquor, without adding any metal chelating agent, then stir for 15 min, and after stirring evenly, keep warm at 140 ℃ for 3 h.

[0052] Test results: DMDS reduction rate 37.7%; methionine monomer loss 1.82%.

[0053] Comparative Example 3: Add the following metal chelating agents to 1000g of mother liquor: 0.2g of EDTA acid and 0.3g of phytic acid (total 0.05wt%, EDTA acid to phytic acid 0.67:1), without adding any hindered phenolic antioxidants; then stir for 15 min, and after stirring evenly, keep warm at 140 ℃ for 3 h.

[0054] Test results: DMDS reduction rate 45.1%; methionine monomer loss 1.51%.

[0055] Comparative Example 4: Add 0.5 g (0.05 wt%) of phytic acid to 1000 g of mother liquor, without adding any hindered phenolic antioxidants; then stir for 15 min, and after stirring evenly, keep warm at 140 ℃ for 3 h.

[0056] Test results: DMDS reduction rate 42.2%; methionine monomer loss 1.58%.

[0057] Comparative Example 5: Add 1.2 g of Irganox 1010 and 0.5 g (0.05 wt%) of EDTA acid to 1000 g of mother liquor, then stir for 15 min. After stirring evenly, keep warm at 140 ℃ for 3 h.

[0058] Test results: DMDS reduction rate 75.1%; methionine monomer loss 0.92%.

[0059] Comparative Example 6: Add 1.2 g of Irganox1010 and 0.5 g (0.05wt%) of phytic acid to 1000 g of mother liquor, then stir for 15 min. After stirring evenly, keep warm at 140 ℃ for 3 h.

[0060] Test results: DMDS reduction rate 76.5%; methionine monomer loss 0.98%.

[0061] It can be seen that as the amount of hindered phenolic antioxidant and metal chelating agent added increases simultaneously, the DMDS reduction rate continues to increase and the loss of methionine monomers continues to decrease; the treatment effect is best when the total mass of hindered phenolic antioxidant to the total mass of metal chelating agent is controlled at 2.27-3:1; under the same total metal chelating agent addition conditions, the antioxidant effect of the EDTA acid and phytic acid composite chelating agent is significantly better than that of the single metal chelating agent.

[0062] Based on the optimal addition ratio obtained in the above small-scale experiments, the following Examples 10-11 added the additive to the hydrolysis section or crystallization mother liquor circulation section of actual methionine production, and sampled and tested the DMDS concentration and methionine content to calculate the DMDS reduction rate and methionine monomer loss.

[0063] Example 10: The hindered phenolic antioxidant Irganox 1010 72 g / h (total 0.12wt%) is added to the feed of the hydantoin hydrolysis tower via a metering pump; metal chelating agents EDTA acid 15 g / h and phytic acid 15 g / h (total 0.05wt%, EDTA acid to phytic acid 1:1) are also added; the hindered phenolic antioxidant:metal chelating agent ratio is 2.4:1. The molar ratio of the feed to the hydrolysis tower is hydantoin:potassium salt = 1:2.6; the hydrolysis temperature is 140 ℃; the hydrolysis pressure is 0.5 MPa; 1.0 MPa steam is directly supplied to the bottom of the tower; and the liquid phase residence time is 3 h.

[0064] Test results: DMDS reduction rate 86.7%; methionine monomer loss 0.61%.

[0065] Example 11: In the decarbonization and recycling feed of the crystallization mother liquor, hindered phenolic antioxidant Irganox 1010 120 g / h (total 0.12 wt%) was added via metering pump; metal chelating agents EDTA acid 25 g / h and phytic acid 25 g / h (total 0.05 wt%, EDTA acid to phytic acid 1:1) were added; the hindered phenolic antioxidant:metal chelating agent ratio was 2.4:1. The hydrolysis temperature was 140 ℃; the hydrolysis pressure was 0.5 MPa; 1.0 MPa steam was directly supplied to the bottom of the column; and the liquid phase residence time was 3 h.

[0066] Test results: DMDS reduction rate 86.5%; methionine monomer loss 0.64%.

[0067] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims and their equivalents, this invention is also intended to include these modifications and variations. The above embodiments or implementations are merely illustrative examples of this invention, and it can also be implemented in other specific ways or forms without departing from its gist or essential characteristics. Therefore, the described embodiments should be considered illustrative rather than limiting in any respect. The scope of this invention should be defined by the appended claims, and any changes equivalent to the intent and scope of the claims should also be included within the scope of this invention.

Claims

1. An additive, characterized in that: The additive contains 1-5 parts by weight of hindered phenolic antioxidant and 1 part by weight of metal chelating agent.

2. The additive according to claim 1, characterized in that: The hindered phenolic antioxidant is selected from one or more of Irganox 1010, Irganox 1076, Irganox 1135, Irganox 1330, Irganox PS 800, Irganox 1098, Irganox 245, Irganox 245-DW, 2,6-di-tert-butyl-p-cresol, butylated hydroxyanisole, and tert-butylhydroquinone.

3. The additive according to claim 1, characterized in that: The metal chelating agent is selected from EDTA and / or phytic acid.

4. The additive according to claim 3, characterized in that: The EDTA is selected from one or more of EDTA acid, disodium EDTA, trisodium EDTA, and tetrasodium EDTA.

5. The additive according to claim 1, characterized in that: The metal chelating agent is obtained by compounding EDTA and phytic acid in a mass ratio of 1:0.2-2.

6. A method for inhibiting the decomposition of methionine during methionine production, characterized in that: The method involves adding the additive according to any one of claims 1-5 to the hydrolysis section and / or the crystallization mother liquor recycling section of methionine production.

7. The method according to claim 6, characterized in that: The total concentration of the hindered phenolic antioxidant after addition is 0.01-0.3 wt%, and the total concentration of the metal chelating agent after addition is 0.01-0.15 wt%.

8. The method according to claim 6 or 7, characterized in that: The additive is added to the feed of the hydrolysis tower for methionine production, and the reaction temperature of the hydrolysis tower is controlled at 140-200℃ and the reaction pressure is 0.5-1.3MPa.

9. The method according to claim 6 or 7, characterized in that: The additive is added to the decarbonization feed of the crystallization mother liquor in methionine production, and the reaction temperature of the decarbonization mother liquor is controlled at 120-180℃ and the reaction pressure is 0.1-0.8MPa.

10. The method according to claim 6 or 7, characterized in that: The additive is added to the pipeline of the methionine production crystallization mother liquor after decarbonization and returned to the hydantoin hydrolysis tower.

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