Tert-butylhydroquinone and preparation method thereof

Abstract

The invention provides a preparation method of tert-butylhydroquinone, which comprises the following steps: carrying out catalytic hydrogenation reduction reaction on hydroquinone and an isobutene alkylated oil phase to reduce TBQ and DTBQ into TBHQ and DTBHQ, adding water and a reducing agent into a crude product, carrying out azeotropic distillation under the protection of nitrogen to remove a residual solvent, and filtering to remove DTBHQ, thereby obtaining the tert-butylhydroquinone. Oxidation by-product impurities TBQ and DTBQ generated in the whole production process are basically distributed in the separated acid catalyst, the crude product mother liquor and the finished product mother liquor, the problem of enrichment of the oxidation by-product impurities is avoided, the quality and yield of the product are improved, and the method is suitable for industrial production. The three strands of materials can be used in a reaction unit or a crude product crystallization unit for next-batch preparation, harmful impurities TBQ and DTBQ are converted into a main product TBHQ and a by-product DTBHQ respectively, waste is turned into wealth, the problem of treatment of a large amount of VOC generated in the product drying process is avoided, and the method is environmentally friendly.

Description

Technical Field

[0001] The present invention relates to the technical field of antioxidant tert-butylhydroquinone, and in particular to a tert-butylhydroquinone and a preparation method thereof. Background Art

[0002] Tert-butylhydroquinone, abbreviated as antioxidant TBHQ, is a hindered phenol antioxidant with a wide range of applications and high cost performance, and has been attracting much attention in the chemical industry. TBHQ is more effective than other commonly used antioxidants such as BHA, BHT, and PG for unsaturated oils, and has many advantages such as no peculiar smell or odor when added to any oil, good safety, high antioxidant performance, and excellent oil solubility.

[0003] TBHQ has a good antioxidant effect. It is precisely because it is more easily oxidized by itself, which causes problems of easy oxidation during the production and storage of TBHQ. TBHQ is prone to produce oxidation by-product impurities 2-tert-butyl-p-benzoquinone (TBQ) and 2,5-di-tert-butyl-p-benzoquinone (DTBQ) during the production process. Although the prior art has been continuously improving the process in order to reduce the occurrence of side reactions, the results are still far from satisfactory. Moreover, with the continuous recycling of the catalyst and solvent, TBQ and DTBQ will continuously accumulate in the reaction system, which will ultimately seriously affect the appearance and purity of the product TBHQ. At the same time, most of the process will also produce a large amount of pollutants, making it difficult to meet the requirements of the green environment.

[0004] Prior art documents:

[0005] Chinese Patent: CN105294403

[0006] Chinese Patent: CN110903170 Summary of the Invention

[0007] The object of the present invention is to provide a tert-butylhydroquinone and a preparation method thereof in view of the deficiencies of the prior art. Through the design of the process, the problem of enrichment of oxidation by-product impurities during the production of antioxidant TBHQ is solved, and TBQ and DTBQ are respectively converted into TBHQ and DTBHQ, turning waste into treasure. Moreover, without the solvent recrystallization process, qualified finished products can be directly obtained, avoiding the problem of treating a large amount of VOCs generated during the product drying process after solvent recrystallization.

[0008] According to the first aspect of the object of the present invention, a preparation method of tert-butylhydroquinone is provided, including the following steps:

[0009] S1. Add hydroquinone to a solvent, add an acidic catalyst, heat to the reaction temperature under nitrogen protection, and then introduce isobutene for alkylation reaction until the reaction end point. After the reaction is completed, separate the acidic catalyst to obtain an oil phase;

[0010] S2, subjecting the oil phase to a catalytic hydrogenation reduction reaction, so that TBQ and DTBQ in the oil phase are reduced to TBHQ and DTBHQ, and then separating the catalyst of the catalytic hydrogenation reduction reaction, and cooling the product to obtain a crude product by crystallization and filtration;

[0011] S3. Add water and a reducing agent to the crude product, and perform azeotropic distillation under nitrogen protection until the solvent is removed, then control the temperature to filter and remove the insoluble DTBHQ, and cool the filtrate to crystallize and filter to obtain the finished product tert-butylhydroquinone TBHQ.

[0012] As an optional embodiment, in step S1, the solvent is xylene, the catalyst is aqueous phosphoric acid solution, and the reaction temperature is 80-100°C.

[0013] As an optional embodiment, in step S2, the catalyst used in the catalytic hydrogenation reduction reaction is R-Ni or a noble metal series.

[0014] As an optional embodiment, in step S2, the reaction conditions of the catalytic hydrogenation reduction reaction are: temperature 60-150° C., reaction pressure 0.3-1.5 MPa.

[0015] As an optional embodiment, in step S3, the weight of water is set according to dissolving all TBHQ in the crude product, and the amount of reducing agent used is 0.1-0.5% of the weight of water.

[0016] As an optional embodiment, in step S3, the temperature during filtration is controlled at 90-95°C.

[0017] As an optional embodiment, in step S3, the reducing agent includes unsaturated sulfide.

[0018] As an optional embodiment, the preparation method further comprises: distilling the finished product mother liquor obtained in step S3, recovering HQ, TBQ, DTBQ and TBHQ therein, and using the recovered product in step S2.

[0019] As an optional embodiment, the distillation conditions of the finished product mother liquor are: an operating temperature of 60 to 90° C. and an operating pressure of -0.05 to 0.08 MPa.

[0020] According to a second aspect of the present invention, there is provided tert-butylhydroquinone prepared by the aforementioned method.

[0021] As can be seen from the above technical solution of the present invention, in the preparation method of tert-butylhydroquinone proposed by the present invention, hydroquinone is heated to the reaction temperature under the protection of nitrogen in the presence of an acidic catalyst and a solvent, and then isobutene is introduced for alkylation reaction. The oil phase after separating the acidic catalyst is subjected to catalytic hydrogenation reduction reaction to reduce TBQ and DTBQ therein to TBHQ and DTBHQ. The oil phase after separating the hydrogenation reduction catalyst is cooled and crystallized, filtered to obtain a crude product. The crude product is added with water and a reducing agent, and azeotropic distillation is carried out under the protection of nitrogen to remove the residual solvent, and DTBHQ is removed by hot filtration. The filtrate is cooled and crystallized, filtered, and vacuum dried to obtain a white finished product of TBHQ. The oxidation by-product impurities TBQ and DTBQ generated in the whole production process are basically distributed in the separated acidic catalyst, the mother liquor of the crude product, and the mother liquor of the finished product, avoiding the problem of enrichment of oxidation by-product impurities, improving the quality and yield of the product, and these three streams of materials can be recycled to the reaction unit or the crude product crystallization unit for the preparation of the next batch, converting the harmful impurities TBQ and DTBQ into the main product TBHQ and the by-product DTBHQ respectively, turning waste into treasure.

[0022] The preparation method of tert-butylhydroquinone of the present invention does not require a solvent recrystallization process, and a qualified finished product can be directly obtained through simple steps, avoiding the problem of treating a large amount of VOC generated during the product drying process, which is green and environmentally friendly. Brief Description of the Drawings

[0023] Figure 1 It is the GC chromatogram of sample 3-2 in the embodiment of the present invention.

[0024] Figure 2 It is the GC chromatogram of sample 5-2 in the embodiment of the present invention.

[0025] Figure 3 It is the GC chromatogram of sample 6-2 in the embodiment of the present invention. Detailed Description of the Invention

[0026] In order to better understand the technical content of the present invention, specific embodiments are hereby given and described in conjunction with the accompanying drawings as follows.

[0027] In the present disclosure, aspects of the present invention are described with reference to the accompanying drawings, in which many illustrative embodiments are shown. The embodiments of the present disclosure are not necessarily intended to cover all aspects of the present invention. It should be understood that the various concepts and embodiments introduced above, as well as those concepts and embodiments described in more detail below, can be implemented in any of many ways.

[0028] The present invention aims to design a preparation method of tert-butylhydroquinone that avoids the enrichment of oxidation by-product impurities TBQ and DTBQ. Hydroquinone is heated to the reaction temperature under nitrogen protection in the presence of an acidic catalyst and a solvent, and then isobutene is introduced for alkylation reaction; after the reaction is completed, the acidic catalyst is separated while it is hot, and is reused as the reaction catalyst for the next batch of reaction (A). The oil phase is subjected to catalytic hydrogenation reduction reaction to reduce TBQ and DTBQ therein to TBHQ and DTBHQ. The oil phase after separating the hydrogenation reduction catalyst is cooled and crystallized, and filtered to obtain the crude product. The mother liquor of the crude product is reused as the reaction solvent for the next batch of reaction (B). The crude product is added with water and a certain amount of reducing agent, and azeotropic distillation is carried out under nitrogen protection to remove the residual solvent, and DTBHQ is removed by hot filtration. The filtrate is cooled and crystallized, filtered, and vacuum dried to obtain the white finished product TBHQ. The mother liquor of the finished product is distilled to recover HQ, TBQ, DTBQ, TBHQ, etc. therein, and is reused in the reaction unit (C). The oxidation impurities TBQ and DTBQ generated in the whole production process are basically distributed in three streams of materials A, B, and C. They are reused in the reaction unit or the crude product crystallization unit for the next batch of preparation, and the harmful impurities TBQ and DTBQ are respectively converted into the main product TBHQ and the by-product DTBHQ.

[0029] In an exemplary embodiment of the present invention, a preparation method of tert-butylhydroquinone is provided, including the following steps:

[0030] S1. Hydroquinone is added to a solvent, and an acidic catalyst is added. It is heated to the reaction temperature under nitrogen protection, and then alkylation reaction is carried out with isobutene until the reaction end point. After the reaction is completed, the acidic catalyst is separated to obtain an oil phase;

[0031] Among them, the separated acidic catalyst is reused as the reaction catalyst for the next batch of alkylation reaction. There is a slight loss in the separation and recovery of the acidic catalyst, and it can be supplemented with fresh acidic catalyst and then reused.

[0032] S2. The oil phase is subjected to catalytic hydrogenation reduction reaction, transferred to a catalytic hydrogenation reduction kettle, a catalyst is added, after nitrogen replacement, hydrogen is introduced, and the temperature is raised in a closed state. Under a certain temperature and pressure, catalytic hydrogenation reduction is carried out to reduce TBQ and DTBQ to TBHQ and DTBHQ. After the reaction is completed, the catalyst for the catalytic hydrogenation reduction reaction is separated, and the product is cooled and crystallized, and filtered to obtain the crude product;

[0033] Among them, the mother liquor of the crude product is reused as the reaction solvent for the next batch of alkylation reaction. There is a slight loss in the recovery process of the mother liquor of the crude product, and it can be supplemented with fresh solvent and then reused.

[0034] S3. Add water and a reducing agent to the crude product, and perform azeotropic distillation under nitrogen protection until the solvent is removed. Then, control the temperature to filter out the insoluble DTBHQ. The filtrate is cooled and crystallized, and then filtered to obtain the finished product tert-butylhydroquinone (TBHQ).

[0035] Among them, the mother liquor of the finished product is distilled to recover the HQ, TBQ, DTBQ, and TBHQ therein, and the recovered substances are recycled to the catalytic hydrogenation reduction reaction. The collected water can be recycled to the next batch, and there is no wastewater discharge in the entire process flow.

[0036] As an optional implementation manner, in step S1, the solvent is xylene, the catalyst is an aqueous phosphoric acid solution, and the reaction temperature is 80-100°C.

[0037] As an optional implementation manner, in step S2, the catalyst used in the catalytic hydrogenation reduction reaction is R-Ni or a noble metal series, such as Pt / C, Pd / C, etc.

[0038] As an optional implementation manner, in step S2, the reaction conditions for the catalytic hydrogenation reduction reaction are: temperature 60-150°C, particularly preferably 90-120°C; reaction pressure 0.3-1.5 MPa, particularly preferably 0.5-1.0 MPa.

[0039] As an optional implementation manner, in step S3, the weight of water is set according to completely dissolving the TBHQ in the crude product, and the usage amount of the reducing agent is 0.1-0.5% of the weight of water.

[0040] As an optional implementation manner, in step S3, the temperature during filtration is controlled at 90-95°C.

[0041] As an optional implementation manner, in step S3, the reducing agent includes unsaturated sulfides.

[0042] In a preferred embodiment, the reducing agent includes sodium sulfite, sodium bisulfite, sodium metabisulfite, sodium dithionite (sodium hydrosulfite), sulfur dioxide, etc., and particularly preferably sodium hydrosulfite.

[0043] As an optional implementation manner, the distillation conditions for the mother liquor of the finished product are: operating temperature 60-90°C, operating pressure -0.05-0.08 MP.

[0044] In another exemplary embodiment of the present invention, there is also provided a tert-butylhydroquinone prepared by the foregoing method. The TBHQ has a purity as high as 99%, high product quality, a long shelf life, and the entire process is green and environmentally friendly, without the problem of tail gas VOC treatment.

[0045] For better understanding, the present invention will be further described below in conjunction with several specific examples. However, the preparation process is not limited thereto, and the content of the present invention is not limited thereto.

[0046] Unless otherwise specified, the materials in the examples are prepared according to existing methods or directly purchased from the market.

[0047] Example 1

[0048] In a 5L glass reactor, add 200g of HQ, 400g of 70% phosphoric acid, and 1600mL of xylene. Heat up to 90°C under nitrogen protection, introduce isobutene and react for 6 hours. Let it stand for liquid separation. Recover 376g of the phosphoric acid phase (PA1) from the bottom. Analyze the composition of the oil phase (denoted as sample 1) and divide it into two equal parts, denoted as oil phase 1 and oil phase 2.

[0049] Example 2

[0050] Cool and crystallize oil phase 1, then filter it. Collect the mother liquor of the crude product (S1-1) for reuse. Add 4.5L of water and 6g of sodium dithionite to the crude product. Under nitrogen protection, perform azeotropic distillation at 95 - 100°C to completely remove the xylene solvent brought in by the crude product. Then perform hot filtration at 90°C. The filter cake is the by-product DTBHQ. Cool and crystallize the filtrate, then filter it. Dry at -0.095MPa and 100°C for 1.5 hours to obtain 91g of the finished product (denoted as sample 2).

[0051] Example 3

[0052] After adjusting the pH of oil phase 2 to 7.0 with 15% sodium carbonate solution, add it to a stainless steel autoclave. Add 6g of R-Ni catalyst, displace with nitrogen, heat up to 100°C, set the hydrogen pressure to 1.0MPa, and react for 2 hours. Separate the catalyst by sedimentation. After analyzing the composition of the reduced reaction solution (denoted as sample 3-1), cool and crystallize it, then filter to obtain the crude product. Collect the mother liquor of the crude product (S1-2) for reuse.

[0053] Add 4.5L of water and 6g of sodium dithionite to the crude product. Under nitrogen protection, perform azeotropic distillation at 95 - 100°C to completely remove the xylene solvent brought in by the crude product. Then perform hot filtration at 90°C. The filter cake is the by-product DTBHQ. Cool and crystallize the filtrate, then filter it. Dry at -0.095MPa and 100°C for 1.5 hours to obtain 99g of the white finished product (denoted as sample 3-2).

[0054] Example 4

[0055] In a 5L glass reactor, 180 g of HQ, 376 g of phosphoric acid (PA1) recovered in Example 1, 24 g of 70% phosphoric acid, a total of 1480 mL of the crude product mother liquor (S1-1 + S1-2) recovered in Examples 1 and 2, 120 mL of xylene were added. Under nitrogen protection, the temperature was raised to 90 °C, and isobutene was introduced for reaction for 5.5 hours. After standing and separating layers, 381 g of phosphoric acid phase (PA2) was recovered from the bottom. The composition of the oil phase (denoted as sample 4) was analyzed and divided into two equal parts, denoted as oil phase 3 and oil phase 4.

[0056] Example 5

[0057] 4 g of 3% Pt / C catalyst was added to oil phase 3 in a stainless steel autoclave. After purging with nitrogen, the temperature was raised to 80 °C, and the hydrogen pressure was set at 0.6 MPa. The reaction was carried out for 1.5 hours. After settling and separating the catalyst, the reduced reaction solution (denoted as sample 5-1) was analyzed for its composition, then cooled for crystallization, filtered to obtain the crude product, and the crude product mother liquor (S3) was collected for reuse.

[0058] 4.5 L of water and 6 g of sodium dithionite were added to the crude product. Under nitrogen protection, azeotropic distillation was carried out at 95 - 100 °C to completely remove the xylene solvent brought in by the crude product. Then, it was filtered while hot. The filter cake was the by-product DTBHQ. The filtrate was cooled for crystallization, filtered, and dried at -0.095 MPa and 100 °C for 1.5 hours to obtain 115 g of white finished product (denoted as sample 5-2).

[0059] Example 6

[0060] 4 g of 3% Pd / C catalyst was added to oil phase 4 in a stainless steel autoclave. After purging with nitrogen, the temperature was raised to 90 °C, and the hydrogen pressure was set at 0.6 MPa. The reaction was carried out for 1.5 hours. After settling and separating the catalyst, the reduced reaction solution (denoted as sample 6-1) was analyzed for its composition, then cooled for crystallization, filtered to obtain the crude product, and the crude product mother liquor (S4) was collected for reuse.

[0061] 4.5 L of water and 6 g of sodium dithionite were added to the crude product. Under nitrogen protection, azeotropic distillation was carried out at 95 - 100 °C to completely remove the xylene solvent brought in by the crude product. Then, it was filtered while hot. The filter cake was the by-product DTBHQ. The filtrate was cooled for crystallization, filtered, and dried at -0.095 MPa and 100 °C for 1.5 hours to obtain 118 g of white finished product (denoted as sample 6-2).

[0062] Component analysis

[0063] The above samples 1 - 8 were analyzed for their components, and the results are shown in Table 1.

[0064] Table 1

[0065]

[0066] As can be seen from the above data, for Sample 2 without catalytic hydrogenation reduction treatment, the purity of the obtained product fails to meet the quality index requirements and needs to go through the organic solvent recrystallization step to reach the requirement of purity greater than 99%. However, the treatment technology for VOC in the drying tail gas of the recrystallized product is difficult and the operation cost is high.

[0067] For Samples 3-2, 5-2, and 6-2 prepared by the method of the present invention, combined with Table 1, Figure 1 , Figure 2 and Figure 3 as shown, it can be known that the quality index requirement of purity greater than 99% can be achieved without organic solvent recrystallization, and there is no problem of treating VOC in the tail gas during the drying process of the crude product (without organic solvent).

[0068] As can be seen from the above, the TBHQ prepared by the method of the present invention can preferably solve the problem of enrichment of oxidation by-product impurities during the production process of the antioxidant TBHQ, convert the harmful impurities TBQ and DTBQ into the main product TBHQ and the by-product DTBHQ respectively, turn waste into treasure, and avoid the problem of treating a large amount of VOC generated during the product drying process.

[0069] Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Those with ordinary knowledge in the technical field to which the present invention pertains can make various modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to what is defined by the claims.

Claims

1. A preparation method of tert-butylhydroquinone, characterized in that, It includes the following steps: S1. Add hydroquinone into a solvent, add an acidic catalyst, heat to the reaction temperature under nitrogen protection, then introduce isobutene to carry out an alkylation reaction until the reaction end point. After the reaction is completed, separate the acidic catalyst to obtain an oil phase; S2. Carry out a catalytic hydrogenation reduction reaction on the oil phase to reduce TBQ and DTBQ in the oil phase to TBHQ and DTBHQ, then separate the catalyst for the catalytic hydrogenation reduction reaction, and the product is cooled, crystallized, and filtered to obtain a crude product; S3. Add water and a reducing agent to the crude product, and carry out azeotropic distillation under nitrogen protection until the solvent is removed, then control the temperature to filter out insoluble DTBHQ, and the filtrate is cooled, crystallized, and filtered to obtain the finished product tert-butylhydroquinone TBHQ.

2. The preparation method of tert-butylhydroquinone according to claim 1, characterized in that, In the step S1, the solvent is xylene, the catalyst is an aqueous phosphoric acid solution, and the reaction temperature is 80 - 100 °C.

3. The preparation method of tert-butylhydroquinone according to claim 1, characterized in that, In the step S2, the catalyst used for the catalytic hydrogenation reduction reaction is R-Ni or a noble metal series.

4. The preparation method of tert-butylhydroquinone according to claim 1, characterized in that, In the step S2, the reaction conditions for the catalytic hydrogenation reduction reaction are: temperature 60 - 150 °C, reaction pressure 0.3 - 1.5 MPa.

5. The preparation method of tert-butylhydroquinone according to claim 1, characterized in that, In the step S3, the weight of water is set according to completely dissolving TBHQ in the crude product, and the usage amount of the reducing agent is 0.1 - 0.5% of the weight of water.

6. The preparation method of tert-butylhydroquinone according to claim 1, characterized in that, In the step S3, the temperature during filtration is controlled at 90 - 95 °C.

7. The preparation method of tert-butylhydroquinone according to claim 1, characterized in that, In the step S3, the reducing agent includes unsaturated sulfides.

8. The preparation method of tert-butylhydroquinone according to claim 1, characterized in that, The preparation method further includes: distilling the mother liquor of the finished product obtained in the step S3, recovering HQ, TBQ, DTBQ, and TBHQ therein, and recycling the recovered substances to the step S2.

9. The preparation method of tert-butylhydroquinone according to claim 8, characterized in that, The distillation conditions for the mother liquor of the finished product are: operating temperature 60 - 90 °C, operating pressure -0.05 - 0.08 MP.

10. A tert-butylhydroquinone prepared by the method according to any one of claims 1 - 9.

Images