A method for synthesizing p-xylylene oxide

Abstract

The application discloses a synthesis method of p-dimethoxybenzene and belongs to the technical field of chemical industry. In the application, the surface acid and alkali of magnesium-aluminum hydrotalcite is adjusted by using tungsten oxide or bismuth oxide to obtain a modified magnesium-aluminum hydrotalcite catalyst. By using a fixed bed reactor, p-dimethoxybenzene is synthesized by using hydroquinone and dimethyl carbonate as raw materials, high-efficiency catalytic conversion is completed under normal pressure, and the green synthesis of p-dimethoxybenzene is realized. The catalyst preparation process is simple, the catalyst cost is low, the solid catalyst is easy to separate from the product, the catalytic reaction activity is high, the yield of p-dimethoxybenzene is high. Under the optimal synthesis condition, the yield and selectivity of p-dimethoxybenzene are as high as 99.8%.

Description

Technical Field

[0001] This invention belongs to the field of chemical technology, specifically relating to a method for synthesizing p-phenylenedimethyl ether. Background Technology

[0002] Terephthalic acid dimethyl ether (TBDE) is an important organic chemical raw material with significant applications in pharmaceuticals, fragrances, and antioxidants. It can be used to produce drugs such as methoxyamine hydrochloride and dyes such as black benzoyl peroxide (ANS), and is also used in the synthesis of food flavorings and tobacco flavorings. Currently, industrially, TBDE is mainly produced by reacting hydroquinone with dimethyl sulfate using a strong alkali. Dimethyl sulfate is highly toxic, and the addition of a large amount of strong alkali generates substantial amounts of highly toxic wastewater and solid waste, causing severe environmental pollution. Dimethyl carbonate (DCS), on the other hand, is a low-pollution, environmentally friendly, and emerging green chemical raw material that is harmless, non-toxic, and pollution-free, attracting widespread attention. With the increasing emphasis on ecological environment in China, developing green TBDE synthesis processes using new alkylating reagents has become a crucial issue that researchers in this field urgently need to address. Summary of the Invention

[0003] To address the problems existing in the background art, the present invention aims to provide a method for synthesizing diphenyl ether. The present invention improves the acidity of the catalyst by adding tungsten oxide or bismuth oxide to the surface of magnesium aluminum layered double hydroxide (MLD), thereby increasing the selectivity of diphenyl ether and lowering the reaction temperature. This yields a highly active and stable modified magnesium aluminum MLD catalyst. Using hydroquinone as a raw material and dimethyl carbonate as an alkylating agent, diphenyl ether is synthesized under normal pressure using the modified magnesium aluminum MLD catalyst. The catalytic reaction temperature is lower, the catalytic activity is higher, and the product selectivity is higher, offering significant advantages compared to existing processes.

[0004] The objective of this invention is achieved through the following means:

[0005] The present invention also provides a method for synthesizing diphenyl ether, comprising the following steps: vaporizing a mixed solution of hydroquinone and dimethyl carbonate and mixing it with a carrier gas, passing it into a reactor containing a modified magnesium aluminum hydrotalcite catalyst with tungsten oxide and / or bismuth oxide supported on the surface, and carrying out a gas-solid phase reaction at 190-350°C to obtain diphenyl ether.

[0006] Furthermore, the reaction temperature is 200–300℃, and the reaction pressure is 0.1–5 MPa.

[0007] Furthermore, the molar ratio of hydroquinone to dimethyl carbonate is 1:1 to 1:10, preferably 1:3.

[0008] Furthermore, the carrier gas is one or a mixture of two or more of nitrogen, argon, helium, carbon dioxide, and neon.

[0009] Furthermore, the catalyst contains 0.01–5 wt% tungsten oxide and 0.01–5 wt% bismuth oxide.

[0010] Furthermore, the preparation method of the modified magnesium aluminum layered double hydroxide catalyst with surface-supported tungsten oxide and / or bismuth oxide includes the following steps:

[0011] (1) The mixed solution containing magnesium salt and aluminum salt was co-precipitated with an alkaline solution, filtered, dried and calcined to obtain magnesium aluminum hydrotalcite.

[0012] (2) Grind the magnesium aluminum hydrotalcite obtained in step (1) into powder, add it to an aqueous solution containing tungsten salt and / or bismuth salt and soak for 1 to 48 hours, filter, dry, and treat at 400 to 600°C for 1 to 24 hours to obtain the product.

[0013] Furthermore, in step (1), the pH of the co-precipitation process is maintained at 9–11, and the temperature is maintained at 20–40°C.

[0014] Furthermore, in step (1), the roasting temperature is 500-700℃ and the roasting time is 2-10h.

[0015] Furthermore, in step (1), the magnesium-aluminum molar ratio is 1:5 to 5:1, preferably 3:2 to 2:1.

[0016] Further, the magnesium salt in step (1) is one or more of magnesium nitrates, chlorides or sulfates, and the aluminum salt is one or more of aluminum nitrates, chlorides or sulfates.

[0017] Furthermore, the alkaline solution mentioned in step (1) is a solution containing one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate.

[0018] Furthermore, the particle size of the powder mentioned in step (2) is 20 to 80 mesh.

[0019] Furthermore, the tungsten salt mentioned in step (2) is one or two of ammonium tungstate and ammonium metatungstate, and the bismuth salt is one or a combination of two or more of bismuth nitrate, chloride or sulfate.

[0020] The advantages of this invention over the prior art are as follows:

[0021] This invention utilizes tungsten oxide or bismuth oxide-modified magnesium aluminum layered double hydroxide (TLD) as a catalyst in a fixed-bed reactor to synthesize diphenyl ether (TPE) from hydroquinone and dimethyl carbonate. The highly efficient catalytic conversion was achieved under atmospheric pressure, realizing the green synthesis of TPE. The catalyst preparation process is simple, the catalyst cost is low, the solid catalyst is easily separated from the product, and the catalytic activity is high, resulting in a high yield of TPE. Under optimal synthesis conditions, the yield and selectivity of TPE reach as high as 99.8%. Detailed Implementation

[0022] The present invention will be described in detail below with reference to the embodiments. However, the implementation of the present invention is not limited thereto. Obviously, the embodiments described below are only some embodiments of the present invention. For those skilled in the art, other similar embodiments can be obtained without creative effort and all fall within the protection scope of the present invention.

[0023] Comparative Example 1

[0024] Synthesis of conventional magnesium-aluminum hydrotalcite: 256g of Mg(NO3)2·6H2O and 125g of Al(NO3)3·9H2O were accurately weighed to prepare 1L of solution A. 108g of NaOH and 94.5g of Na2CO3 were weighed to prepare 1L of solution B. 100mL of deionized water was added to beaker C. Under stirring, solutions A and B were added to beaker C separately using a peristaltic pump for co-precipitation at 25℃, maintaining the pH of the system at 10-11. After the addition was complete, stirring was continued for 10h. The mixture was filtered and dried in an oven at 110℃ for 12h. The dried sample was then calcined in a muffle furnace at a rate of 10℃ / min to 650℃ for 5h to obtain the hydrotalcite carrier, labeled Sample 1.

[0025] Examples 1-9 illustrate the synthesis methods of modified magnesium-aluminum hydrotalcite series catalysts:

[0026] Example 1

[0027] Weigh 0.1g of ammonium tungstate and dissolve it in 100ml of water. Add 100g of ground sample 1 and impregnate it. Let it stand for 24h, filter it, and dry it in an oven at 110℃ for 12h. Then, calcine the dried sample in a muffle furnace at a rate of 10℃ / min to 500℃ for 6h to obtain the catalyst, which is labeled as Sample 2.

[0028] Example 2

[0029] Weigh 5g of ammonium tungstate and dissolve it in 100ml of water. Add 100g of ground sample 1 and impregnate it. Let it stand for 24h, filter it, and dry it in an oven at 110℃ for 12h. Then, calcine the dried sample in a muffle furnace at a rate of 10℃ / min to 500℃ for 6h to obtain the catalyst, which is labeled as Sample 3.

[0030] Example 3

[0031] Weigh 30g of ammonium tungstate and dissolve it in 100ml of water. Add 100g of ground sample 1 and impregnate it. Let it stand for 24h, filter it, and dry it in an oven at 110℃ for 12h. Then, calcine the dried sample in a muffle furnace at a rate of 10℃ / min to 500℃ for 6h to obtain the catalyst, which is labeled as Sample 4.

[0032] Example 4

[0033] Weigh 0.1g of bismuth nitrate and dissolve it in 100ml of water. Add 100g of ground sample 1 and impregnate it. Let it stand for 24h, filter it, and dry it in an oven at 110℃ for 12h. Then, calcine the dried sample in a muffle furnace at a rate of 10℃ / min to 500℃ for 6h to obtain the catalyst, which is labeled as Sample 5.

[0034] Example 5

[0035] Weigh 1g of bismuth nitrate and dissolve it in 100ml of water. Add 100g of ground sample 1 and impregnate it. Let it stand for 24h, filter it, and dry it in an oven at 110℃ for 12h. Then, calcine the dried sample in a muffle furnace at a rate of 10℃ / min to 500℃ for 6h to obtain the catalyst, which is labeled as Sample 6.

[0036] Example 6

[0037] Weigh 20g of bismuth nitrate and dissolve it in 100ml of water. Add 100g of ground sample 1 and impregnate it. Let it stand for 24h, filter it, and dry it in an oven at 110℃ for 12h. Then, calcine the dried sample in a muffle furnace at a rate of 10℃ / min to 500℃ for 6h to obtain the catalyst, which is labeled as Sample 7.

[0038] Example 7

[0039] Weigh out 2.5g of ammonium tungstate and 0.5g of bismuth nitrate and dissolve them in 50ml of water. Add 100g of ground sample1 and impregnate the sample. Let it stand for 24h, filter it, and dry it in an oven at 110℃ for 12h. Then, calcine the dried sample in a muffle furnace at a rate of 10℃ / min to 500℃ for 6h to obtain the catalyst, which is labeled as Sample 8.

[0040] Example 8

[0041] Weigh out 5g of ammonium tungstate and 2.5g of bismuth nitrate and dissolve them in 50ml of water. Add 100g of ground sample1 and impregnate the sample. Let it stand for 24h, filter it, and dry it in an oven at 110℃ for 12h. Then, calcine the dried sample in a muffle furnace at a rate of 10℃ / min to 500℃ for 6h to obtain the catalyst, which is labeled as Sample 9.

[0042] Example 9

[0043] The modified catalyst was prepared using the same method as in Comparative Example 1, but with the magnesium-aluminum ratio adjusted to 1:5, and then processed in the same manner as in Example 2 to obtain the modified catalyst, labeled as Sample 10.

[0044] Example 10

[0045] The same preparation method as Comparative Example 1 was used, but the ratio of magnesium to aluminum was adjusted to 5:1, and then the catalyst was treated in the same manner as in Example 2 to obtain the modified catalyst, labeled as Sample 11.

[0046] Example 11

[0047] Catalyst Sample 3 was compressed into 20-40 mesh particles, and 8g was weighed and loaded into a 304 stainless steel fixed-bed reactor. The raw materials were hydroquinone and dimethyl carbonate. The reaction solution was metered in using a horizontal flow pump. The reaction was carried out at atmospheric pressure and a reaction temperature of 225℃, with a mass hourly space velocity of 0.5h⁻¹. -1 The carrier gas was N2, and the flow rate was 10 mL / min. The molar ratio of the reactants was varied, and the resulting samples were subjected to chromatographic analysis. The reaction results are shown in Table 1.

[0048] Table 1. Hydroquinone conversion rate and dimethyl ether selectivity in Example 11

[0049]

[0050] Example 12

[0051] The specific process is the same as in Example 11, except that the hydroquinone / dimethyl carbonate (molar ratio) is 1:3, and the space velocity of the reaction is changed. The specific experimental results are shown in Table 2.

[0052] Table 2 shows the hydroquinone conversion rate and dimethyl ether selectivity in Example 12.

[0053]

[0054]

[0055] Example 13

[0056] The specific process is the same as in Example 11, except that the molar ratio of hydroquinone / dimethyl carbonate is 1:3 and the reaction temperature is changed. The specific experimental results are shown in Table 3.

[0057] Table 3. Hydroquinone conversion rate and dimethyl ether selectivity in Example 13

[0058] Temperature ℃ Hydroquinone conversion rate % p-phenylenedimethyl ether selectivity % 180 22.3 61.8 200 86.2 76.2 225 98.1 97.5 250 98.3 96.8 300 100 73.6

[0059] Example 14

[0060] The specific process is the same as in Example 11, except that the molar ratio of hydroquinone / dimethyl carbonate is 1:3, and the flow rate of nitrogen gas in the reaction is changed. The specific experimental results are shown in Table 4.

[0061] Table 4. Hydroquinone conversion rate and dimethyl ether selectivity in Example 14

[0062] Gas flow rate (ml / min) Hydroquinone conversion rate % p-phenylenedimethyl ether selectivity % 1 99.8 99.8 10 98.1 97.5 100 63.9 86.7

[0063] Example 15

[0064] The specific process is the same as in Example 11, except that the molar ratio of hydroquinone / dimethyl carbonate is 1:3, and the type of inert gas in the reaction is changed. The specific experimental results are shown in Table 5.

[0065] Table 5. Hydroquinone conversion rate and dimethyl ether selectivity in Example 15

[0066] Gas types Hydroquinone conversion rate % p-phenylenedimethyl ether selectivity % Nitrogen 98.1 97.5 Argon 99.4 99.7 helium 99.9 99.8 carbon dioxide 95.2 79.6

[0067] Example 16

[0068] Comparison of the activities of different catalysts under the same reaction conditions: 8g of catalyst particles (20-40 mesh) were weighed and loaded into a 304 stainless steel fixed-bed reactor; hydroquinone / dimethyl carbonate (molar ratio) was 1:3; nitrogen was used as the carrier gas; and the space velocity was 0.5 h⁻¹. -1 The experimental results after 10 hours of reaction at atmospheric pressure and reaction temperature of 225℃ and a flow rate of 10 mL / min are shown in Table 6.

[0069] Table 6. Hydroquinone conversion rate and dimethyl ether selectivity in Example 16

[0070] Catalyst types Hydroquinone conversion rate % p-phenylenedimethyl ether selectivity % Sample 1 66.3 83.6 Sample 3 98.1 97.5 Sample 6 96.8 95.9 Sample 7 99.6 99.2

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for synthesizing p-phenylenedimethyl ether, characterized in that, Includes the following steps: A mixed solution of hydroquinone and dimethyl carbonate is vaporized and mixed with a carrier gas, then introduced into a reactor containing a modified magnesium aluminum hydrotalcite catalyst with surface-supported tungsten oxide and / or bismuth oxide, and subjected to a gas-solid phase reaction at 200~300℃ to obtain dimethyl terephthalate. The reaction pressure is 0.1~5 MPa; the molar ratio of hydroquinone to dimethyl carbonate is 1:3~1:10; The catalyst contains 0.01-5 wt% tungsten oxide and 0.01-5 wt% bismuth oxide. The preparation method of the modified magnesium aluminum layered double hydroxide catalyst with surface-supported tungsten oxide and / or bismuth oxide includes the following steps: (1) The mixed solution containing magnesium salt and aluminum salt is co-precipitated with an alkaline solution, filtered, dried and calcined to obtain magnesium aluminum hydrotalcite; (2) Grind the magnesium aluminum hydrotalcite obtained in step (1) into powder, add it to an aqueous solution containing tungsten salt and / or bismuth salt and soak for 1 to 48 hours, filter, dry, and treat at 400 to 600 °C for 1 to 24 hours to obtain the product; In step (1), the magnesium-aluminum molar ratio is 3:2 to 2:1; the magnesium salt is one or more of magnesium nitrates, chlorides or sulfates, and the aluminum salt is one or more of aluminum nitrates, chlorides or sulfates. In step (1), the pH of the co-precipitation process is maintained at 9-11, and the temperature is maintained at 20-40℃. In step (1), the roasting temperature is 500~700℃ and the roasting time is 2~10h; The tungsten salt mentioned in step (2) is one or two of ammonium tungstate and ammonium metatungstate, and the bismuth salt is one or a combination of two or more of bismuth nitrate, chloride or sulfate.

2. The synthesis method according to claim 1, characterized in that, The molar ratio of hydroquinone to dimethyl carbonate is 1:

3.

3. The synthesis method according to claim 1, characterized in that, The carrier gas is one or a mixture of two or more of nitrogen, argon, helium, carbon dioxide and neon.

4. The synthesis method according to claim 1, characterized in that, The alkaline solution mentioned in step (1) is a solution containing one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate.

5. The synthesis method according to claim 1, characterized in that, The particle size of the powder mentioned in step (2) is 20~80 mesh.

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