Green preparation method of terephthalic acid dihydrazide
By using the same alcohol solvent as the by-product in the preparation process of terephthalic acid dihydrazide for stirring and distillation reaction, the problems of high energy consumption and low efficiency in the prior art are solved, and a high yield, low energy consumption and environmentally friendly preparation method is achieved, and it is suitable for tire rubber processing.
Patent Information
- Application Number
- CN202510553073.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-29
- Publication Date
- 2025-08-05
AI Technical Summary
The prior art has problems such as high energy consumption, difficulty in treating waste liquids and low utilization rate of hydrazine when preparing dihydrazine in terephthalic acid. In particular, the acid chloride method produces chlorine-containing organic matter and is highly dangerous, while the hydrazine solution of the esters is slow and has low efficiency.
The alcohol solvents of the same as the by-products are used for stirring and distillation reactions. By adding hydrazine hydrate under a stirring state and heating and distillation, the purification and recovery of solvents and by-products are achieved simultaneously, and the ratio of hydrazine hydrate is adjusted to meet the needs of products of different specifications, and the mother liquor and hydrazine hydrate are recycled.
It realizes an efficient reaction process, shortens the synthesis cycle, improves product yield and hydrazine utilization, reduces wastewater and energy consumption, adapts to different application needs, and reduces the Payne effect and rolling resistance of tire rubber.
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Figure CN120423976A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of terephthalic acid dihydrazide, and more particularly to a green manufacturing method of terephthalic acid dihydrazide. Background Art
[0002] Dihydrazide additives are widely used in tires. As functional additives in rubber formulations, they can not only improve the dispersion of fillers in rubber through hydrogen bonding with the surface molecules of fillers (carbon black and / or white carbon black), but also react with the carbonyl oxygen generated by rubber molecules during mixing to form hydrazone bonds, thereby strengthening the rubber network structure, reducing the Payne effect, improving the dynamic mechanical properties of the rubber compound, reducing heat generation, increasing strength and elasticity, improving the durability and wear resistance of the tire, and reducing rolling resistance.
[0003] There are two common methods for preparing terephthalic acid dihydrazide. The first, the acyl chloride method, involves reacting terephthalic acid with thionyl chloride (SOCl2) to produce terephthaloyl chloride. The terephthaloyl chloride is then condensed with hydrazine hydrate (N2H4·H2O) in a solvent such as dichloromethane. Pyridine is added as an acid absorbent, and the product is purified after the reaction through filtration, washing, and recrystallization. While this method offers the advantage of high yield, the production process results in a large amount of chlorinated organic matter in the wastewater, requiring specialized treatment (such as incineration or chemical oxidation), increasing environmental costs and presenting a high risk.
[0004] The second method is the hydrazine hydrolysis of esters: the target product is directly generated by reacting terephthalic acid esters with hydrazine hydrate at high temperature. However, the high temperature reaction will trigger the decomposition of hydrazine (N2H4) (3N2H4→4NH3+N2), generating by-products such as nitrogen and ammonia, which reduces the effective utilization rate of hydrazine. At the same time, the exchange reaction rate of esters and hydrazine is slow, usually taking 12-24 hours to complete, and the production efficiency is much lower than the acyl chloride method.
[0005] Therefore, it is necessary to propose a green manufacturing method of terephthalic acid dihydrazide to solve the above problems. Summary of the Invention
[0006] The purpose of the present invention is to solve the problems raised in the above background technology and to provide a green production method for terephthalic acid dihydrazide.
[0007] In order to achieve the above-mentioned purpose, the present invention specifically adopts the following technical solutions:
[0008] A green manufacturing method for terephthalic acid dihydrazide comprises the following steps:
[0009] S1, stirring: placing the raw materials and the alcohol solvent in a reaction kettle and uniformly stirring to obtain a mixed solution or suspension, wherein the raw material is a C1-C4 alcohol ester of terephthalic acid, and the alcohol solvent is a C1-C4 alcohol that is the same as the terephthalic acid diol ester;
[0010] S2, reaction: adding 80% by mass fraction of hydrazine hydrate to the mixed solution or suspension under stirring, heating the kettle to raise the temperature to 60-105°C, keeping the temperature and distilling for 1-4 hours to distill out a distillate containing part of the alcohol solvent, by-product alcohols and water;
[0011] S3, treatment: cooling the material in the kettle after the distillation to below 30°C, filtering, washing with the same alcohol solvent and drying to obtain the finished product;
[0012] S4, recovery: the distillate is subjected to rectification to obtain a recovered alcohol solvent, which is used in the above steps S1-S3; the mixed mother liquor of the filtered and washed materials is subjected to rectification to obtain a recovered alcohol solvent and a concentrated alcohol solution of hydrazine hydrate, the former of which is also used in the above steps S1-S, and the latter is used to replace part of the hydrazine hydrate in step S1 after the hydrazine hydrate content is determined;
[0013]
[0014]
[0015] Preferably, the raw material in step S1 is dimethyl terephthalate or diethyl terephthalate, and dimethyl terephthalate is most preferred. The alcohol solvent in step S1 is preferably methanol or ethanol corresponding to the raw material, and methanol is most preferred.
[0016] Preferably, the stirring speed in step S1 is 50-300 r / min, preferably 150-250 r / min, and the stirring speed in step S2 is 100-300 r / min, preferably 150-250 r / min.
[0017] Preferably, the molar ratio of the raw material to hydrazine hydrate is 1:2.0-8.0, preferably 1:2.5-4.5.
[0018] Preferably, the mass ratio of the raw material to the alcohol solvent in the stirring in step S1 is 1.0:1.0-4.5, preferably 1.0:1.0-2.0.
[0019] Preferably, the insulation and distillation temperature in the step S2 reaction is preferably 65-85°C.
[0020] Preferably, the insulation and distillation time in the step S2 reaction is preferably 1.5-3 hours.
[0021] Compared with the prior art, the present invention has the following beneficial effects:
[0022] 1. During the reaction, the use of the same alcohol solvent as the by-product alcohol not only promotes efficient reaction performance but also enables the combined distillation and purification of the solvent and by-product, thereby supporting resource recycling and energy conservation and emission reduction. This process effectively shortens the synthesis cycle and simplifies subsequent processing steps by simultaneously distilling the solvent and by-product under heat preservation conditions. Furthermore, concentration increases the concentration of the reaction system, facilitating the advancement of the main reaction. With an excess of hydrazine hydrate, the reaction rate is accelerated, promoting the formation of dihydrazide while suppressing the formation of other by-products.
[0023] 2. By adjusting the ratio of hydrazine hydrate, products with different dihydrazide contents can be produced to meet different application requirements. After solid-liquid separation, the mother liquor is concentrated and reused, which not only avoids the generation of high-ammonia nitrogen wastewater, but also allows the remaining hydrazine hydrate to continue to participate in the reaction, further increasing the dihydrazide content. This process has multiple green and environmental advantages, such as short cycle, high yield, low energy consumption, low wastewater, and by-product recycling for the synthesis of the original process. At the same time, it can avoid the generation of by-products such as nitrogen and ammonia due to high temperature, thereby improving the effective utilization rate of hydrazine. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 This is a typical liquid chromatogram of terephthalic acid dihydrazide in the present invention;
[0025] Figure 2 It is a typical infrared spectrum of terephthalic acid dihydrazide in the present invention. DETAILED DESCRIPTION
[0026] The present invention will be further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the scope of protection of the present invention is not limited thereby.
[0027] The materials and instruments used in the following examples are all commercially available, and the reaction flask used is equipped with a thermometer, a mechanical stirring device, a distillation condenser, and a receiver.
[0028] In the presence of an alcohol solvent (methanol), dimethyl terephthalate reacts with hydrazine hydrate at a certain ratio and reaction temperature to obtain the low rolling resistance modifier terephthaloyl hydrazide. The chemical formula is:
[0029]
[0030] In the presence of an alcohol solvent (ethanol), diethyl terephthalate reacts with hydrazine hydrate at a certain ratio and reaction temperature to obtain the low rolling resistance modifier terephthaloyl hydrazide. The chemical formula is:
[0031]
[0032] Figure 1 For test analysis: a typical chromatogram of terephthalic acid dihydrazide, in which the peak with a retention time of 3.531 min is terephthalic acid dihydrazide, and the peak with a retention time of 10.429 min is terephthalic acid monohydrazide.
[0033] Figure 2 It is a typical infrared spectrum of terephthalic acid dihydrazide in the present invention.
[0034] Example 1:
[0035] S1, stirring: add 80g of dimethyl terephthalate and 130g of methanol into the reaction flask, start mechanical stirring at a speed of 180r / min, and stir to obtain a mixed solution;
[0036] S2, reaction: add 101.97 g of 80% hydrazine hydrate to the mixed solution, increase the speed to 250 r / min, raise the temperature to 70°C, keep warm and distill for 3 hours to obtain a distillate;
[0037] S3. Treatment: The temperature of the contents of the bottle was lowered to 20°C, filtered, washed with distilled methanol, and dried to obtain 77.87 g of product.
[0038] Example 2:
[0039] S1, stirring: add 80g of dimethyl terephthalate and 130g of methanol into the reaction flask, start mechanical stirring at a speed of 140r / min, and stir to obtain a mixed solution;
[0040] S2, reaction: add 101.97 g of 80% hydrazine hydrate to the mixed solution, increase the speed to 250 r / min, raise the temperature to 75°C, keep warm and distill for 2.5 hours to obtain a distillate;
[0041] S3. Treatment: The temperature of the contents of the bottle was lowered to 25°C, filtered, washed with distilled methanol, and dried to obtain 77.62 g of product.
[0042] The difference between Example 2 and Example 1 is that the rotation speed during the stirring step is reduced, the distillation time during the reaction step is shortened, and the temperature during the treatment step is lowered. The remaining steps remain the same as in Example 1.
[0043] Example 3:
[0044] S1, stirring: add 40g of dimethyl terephthalate and 80g of methanol into the reaction flask, start mechanical stirring at a speed of 120r / min, and stir to obtain a mixed solution;
[0045] S2, reaction: the temperature of the mixed solution was raised to 64 ° C, 31.9 g of 80% hydrazine hydrate was added, the rotation speed was maintained at 120 r / min, the temperature was raised to 70 ° C, and the mixture was kept warm and distilled for 2 h to obtain a distillate;
[0046] S3. Treatment: The temperature of the contents of the bottle was lowered to 20°C, filtered, washed with distilled methanol, and dried to obtain 38.04 g of product.
[0047] The changes in Example 3 from Example 1 are that the molar ratio of hydrazine hydrate to dimethyl terephthalate is reduced, the stirring speed is maintained at 120 r / min, and the temperature of the mixed solution is preheated to 64° C. before the dropwise addition of hydrazine hydrate to reduce the distillation time. The remaining steps remain the same as in Example 1.
[0048] Example 4:
[0049] S1, stirring: add 80g of dimethyl terephthalate and 130g of methanol into the reaction flask, start mechanical stirring at a speed of 180r / min, and stir to obtain a mixed solution;
[0050] S2, reaction: the mixed solution was heated to 68 ° C, 63.73 g of 80% hydrazine hydrate was added, the rotation speed was increased to 250 r / min, the temperature was increased to 70 ° C, and the mixture was kept warm and distilled for 3 h to obtain a distillate;
[0051] S3. Processing: Cool the contents of the bottle to 0°C, filter, wash with distilled methanol, and dry. Retain the mother liquor after filtration. 77.65 g of product was obtained.
[0052] Example 4 differs from Example 1 in that the mixed solution is preheated to 68° C. in the reaction step, the molar ratio of hydrazine hydrate is reduced, and the temperature of the material in the bottle is subsequently reduced in the treatment step. The remaining steps remain the same as in Example 1.
[0053] Example 5:
[0054] S1, stirring: add 80g of dimethyl terephthalate and 130g of methanol into the reaction flask, start mechanical stirring at a speed of 180r / min, and stir to obtain a mixed solution;
[0055] S2, reaction: the mixed solution was heated to 64 ° C, 63.73 g of 80% hydrazine hydrate was added, the speed was increased to 250 r / min, the temperature was raised to 70 ° C, and after keeping warm for 1.5 h, 18 g of the mother liquor after filtering in Example 4 was added, and the temperature was kept warm for another 0.5 h, and methanol was distilled to obtain a material from which methanol was distilled;
[0056] S3. Treatment: The temperature of the above materials was lowered to 20°C, filtered, washed with clean water to pH-8, and dried to obtain 77.68 g of product.
[0057] The differences between Example 5 and Example 4 are that in the reaction step, the temperature of the mixed solution is lowered before the addition of hydrazine hydrate, and the mother liquor from Example 4 is added. In the treatment step, the temperature of the material is lowered to 20° C. and washed with clean water. The remaining steps remain the same as in Example 4.
[0058] Example 5 The mother liquor in Example 4 was applied mechanically. While ensuring the yield, the dihydrazide content was found to be increased by 1.9%.
[0059] Example 6:
[0060] S1, stirring: add 111g of diethyl terephthalate and 50g of ethanol into the reaction flask, start mechanical stirring at a speed of 180r / min, and stir to obtain a mixed solution;
[0061] S2, reaction: the temperature of the mixed solution was raised to 75 ° C, 31.5 g of 80% hydrazine hydrate was added, the speed was increased to 250 r / min, the temperature was raised to 80 ° C, and after keeping warm for 1 hour, 31.5 g of hydrazine hydrate was added twice, and the temperature was kept warm for another 1 hour to obtain a distillate;
[0062] S3. Treatment: The distillate was cooled to 20°C, filtered, washed with water until the pH value was -8, and dried to obtain 94.5 g of product.
[0063] The changes in Example 6 are that the raw material in the stirring step is changed to diethyl terephthalate, and the solvent is changed to ethanol, which is equivalent to the corresponding by-product alcohol, the hydrazine hydrate in the reaction step is added twice, and finally, the filtered material is washed with clean water.
[0064] The products obtained in Examples 1 to 6 are compared and analyzed below, with the analysis indicators being yield, monohydrazide content, dihydrazide content, and total hydrazide content.
[0065] Table 1 Performance comparison
[0066]
[0067]
[0068] As shown in Table 1, the yield and dihydrazide content of Example 1 are better than those of other embodiments, and the total hydrazide content is second only to that of Example 2; the total hydrazide content of Example 2 is better than that of other embodiments, and the dihydrazide content is second only to that of Example 1; the monohydrazide content obtained in Example 4 is better than that of other embodiments. This shows that the dihydrazide content obtained using the components and method of Example 1 is the best, and the monohydrazide content obtained using the components and method of Example 4 is the best. By adjusting the different ester and hydrazine hydrate molar ratios, products of different specifications can be obtained to meet different usage requirements.
[0069] In the presence of a solvent, dimethyl terephthalate (or its diethyl ester) exhibits good dispersibility, enabling the reaction to proceed rapidly. After the addition of the feed, the temperature is raised to a specified temperature during the synthesis process, and distillation is performed simultaneously to separate the solvent and the byproduct, methanol. This process is carried out simultaneously with the insulation reaction. The separated solvent and byproducts are recycled and purified for reuse.
[0070] After the reaction and distillation separation stages are completed, the temperature will be lowered to the range of 0-30°C, followed by solid-liquid washing and separation. In this step, methanol or water can be used as the eluent. Choosing methanol as the eluent not only helps to reduce the generation of wastewater, but also allows it to be integrated into the solvent recovery process for distillation, purification and reuse. If water is used as the eluent, it can be included in the distillation process for condensation purification and reuse. Finally, the solid material is dried to obtain the target product - terephthalic acid hydrazide. In addition, the mother liquor generated during the separation process can be reused multiple times through reasonable application strategies, further improving the overall efficiency and environmental friendliness of the process.
[0071] In summary, this method achieves a product yield greater than 96% and a total hydrazide content greater than 95%. It avoids the problem of high temperatures triggering hydrazine decomposition, which generates byproducts such as nitrogen and ammonia and reduces the effective utilization rate of hydrazine. It offers a short reaction cycle and high yield. It also offers multiple environmental advantages, including low energy consumption, minimal wastewater production, and the recycling of byproducts for the synthesis process. Subsequent application of this method in tire rubber processing has been shown to significantly reduce the Payne effect of vulcanized rubber by more than 30%, corresponding to a 10-20% reduction in tire rolling resistance. This method has promising prospects for industrial application.
Claims
1. A green manufacturing method for terephthalic acid dihydrazide, characterized in that: The following steps are involved: S1, stirring: placing the raw materials and the alcohol solvent in a reaction kettle and uniformly stirring to obtain a mixed solution or suspension, wherein the raw material is a C1-C4 alcohol ester of terephthalic acid, and the alcohol solvent is a C1-C4 alcohol that is the same as the terephthalic acid diol ester; S2, reaction: adding 80% by mass fraction of hydrazine hydrate to the mixed solution or suspension under stirring, heating the kettle to raise the temperature to 60-105°C, keeping the temperature and distilling for 1-4 hours to distill out a distillate containing part of the alcohol solvent, by-product alcohols and water; S3, treatment: cooling the material in the kettle after the distillation to below 30°C, filtering, washing with the same alcohol solvent and drying to obtain the finished product; S4, recovery: the distillate is subjected to rectification to obtain a recovered alcohol solvent, which is used in the above steps S1-S3; the mixed mother liquor of the filtered and washed materials is subjected to rectification to obtain a recovered alcohol solvent and a concentrated alcohol solution of hydrazine hydrate, the former of which is also used in the above steps S1-S, and the latter is used to replace part of the hydrazine hydrate in step S1 after the hydrazine hydrate content is determined; 2. The green manufacturing method of terephthalic acid dihydrazide according to claim 1, characterized in that: The raw material in step S1 is preferably dimethyl terephthalate or diethyl terephthalate, and dimethyl terephthalate is most preferred. The alcohol solvent in step S1 is preferably methanol or ethanol corresponding to the raw material, and methanol is most preferred.
3. The green manufacturing method of terephthalic acid dihydrazide according to claim 1, characterized in that: The stirring speed in step S1 is 50-300 r / min, preferably 150-250 r / min, and the stirring speed in step S2 is 100-300 r / min, preferably 150-250 r / min.
4. The green manufacturing method of terephthalic acid dihydrazide according to claim 1, characterized in that: The molar ratio of the raw material to hydrazine hydrate is 1:2.0-8.0, preferably 1:2.5-4.
5.
5. The green manufacturing method of terephthalic acid dihydrazide according to claim 1, characterized in that: In the step S1, the mass ratio of the raw material to the alcohol solvent during stirring is 1.0:1.0-4.5, preferably 1.0:1.0-2.
0.
6. The green manufacturing method of terephthalic acid dihydrazide according to claim 1, characterized in that: The insulation and distillation temperature in the step S2 reaction is preferably 65-85°C.
7. The green manufacturing method of terephthalic acid dihydrazide according to claim 1, characterized in that: The heat preservation and distillation time in the step S2 reaction is preferably 1.5-3 hours.