A method for synthesizing p-hydroxyanisole in gas phase

Abstract

The present invention provides a method for gas-phase synthesis of p-hydroxyanisole. The method uses a graphite-supported P-Ru-Gd catalyst to catalyze the synthesis of p-hydroxyanisole by hydroquinone and methanol under gas-phase conditions. The process uses a fixed-bed continuous reactor, wherein the reactor includes a gasification section, a reaction section and a heat preservation section. The raw materials are first fully gasified in the gasification section and then enter the reaction section containing the catalyst to react. Thereafter, the raw materials enter the storage tank through the heat preservation section and are condensed to obtain a reaction solution. The preparation method in the present invention ensures that the activity and stability of the catalyst in the reaction section are not affected, and the catalyst has the advantages of strong activity and long life.

Description

Technical Field

[0001] The invention belongs to the field of chemical synthesis technology, and particularly relates to a method for synthesizing p-hydroxyanisole in a gas phase. Background Art

[0002] p-Hydroxyanisole (p-hydroxyanisole), also known as 4-methoxyphenol, hydroquinone methyl ether, and MEHQ, is a white flaky crystal. It is an important chemical product used in a wide range of applications, including as a polymerization inhibitor (e.g., for vinyl polymers, acrylic resins, and methacrylic resins), a dye intermediate (e.g., hydroquinone dyes), a pharmaceutical intermediate (e.g., antibiotics), and an antioxidant.

[0003] The synthesis of p-hydroxyanisole primarily involves the hydroxylation of p-aminoanisole and the methylation of hydroquinone. The hydroxylation of p-aminoanisole primarily involves diazotization and hydrolysis reactions to produce p-hydroxyanisole. This process offers low reaction yields, high raw material costs, and difficult waste treatment. The hydroquinone methylation process can be further categorized as the dimethyl sulfate method, the chloromethane method, and the methanol method, depending on the methylating agent. The raw material dimethyl sulfate in the dimethyl sulfate method is a highly toxic chemical, resulting in significant waste pollution. The chloromethane method is an older process, exhibits a relatively low overall yield, and requires high-pressure equipment. In contrast, the methanol method, which uses methanol as the methylating agent, offers significant advantages, including a wide range of raw material sources, low cost, and environmentally friendly and efficient processing. The methanol method is highly competitive in the market for the synthesis of p-hydroxyanisole.

[0004] Patent CN102408319A uses hydroquinone, methanol, and sulfuric acid to produce p-hydroxyanisole, which mainly consists of four steps: etherification, distillation, extraction, and vacuum distillation. Although this process uses the methanol method, the post-processing steps are complex and the process is a batch reactor process, which is relatively cumbersome. Patent CN109111350A synthesizes p-hydroxyanisole in a hydroquinone and methanol solution using acid as a catalyst and quinhydrone as an auxiliary agent or raw material liquid phase conditions. This process is still a batch reactor production process, and the raw material quinhydrone is relatively expensive.

[0005] Therefore, it is of great research value to develop a green and efficient preparation method for p-hydroxyanisole with simple post-processing, high product selectivity, strong catalyst activity and stable long-term operation. Summary of the Invention

[0006] One of the objects of the present invention is to provide a method for vapor phase synthesis of p-hydroxyanisole, which can obtain p-hydroxyanisole with high selectivity, and has significant advantages such as high product selectivity, strong catalyst activity and stable long-term operation.

[0007] To achieve the above object, the present invention provides a novel graphite-supported P-Ru-Gd catalyst, which can obtain p-hydroxyanisole with high conversion rate and high selectivity under gas phase conditions. In addition, the present invention adopts a fixed bed process for reaction, wherein a gasification section first gasifies the raw material into a gaseous state, thereby preventing liquid from entering the reaction section, thereby ensuring that the activity and stability of the catalyst in the reaction section are not affected, and the catalyst has the advantages of high activity, long service life, and the like.

[0008] The technical solution is as follows:

[0009] The invention discloses a method for synthesizing p-hydroxyanisole in gas phase. The method adopts a graphite-supported P-Ru-Gd catalyst to catalyze the synthesis of p-hydroxyanisole from hydroquinone and methanol under gas phase conditions.

[0010] In one embodiment of the present invention, the method adopts a fixed bed continuous reactor, wherein the reactor comprises a gasification section, a reaction section and a heat preservation section.

[0011] In one embodiment of the present invention, in the method, the raw materials are first gasified in a gasification section, then enter a reaction section containing a catalyst to react, and then enter a storage tank through an insulation section for condensation to obtain a reaction liquid; preferably, the temperature of the gasification section is 260-350°C, the temperature of the reaction section is 200-260°C, and the temperature of the insulation section is 170-200°C.

[0012] In one embodiment of the present invention, the molar ratio of hydroquinone to methanol in the method is 1:(5-12).

[0013] In one embodiment of the present invention, the mass space velocity of the raw material liquid in terms of hydroquinone is 0.06-1.5h -1 .

[0014] Another object of the present invention is to provide a method for preparing a graphite-supported P-Ru-Gd catalyst.

[0015] A method for preparing a graphite-supported P-Ru-Gd catalyst, wherein the P-Ru-Gd catalyst is the catalyst used in the above method, and the preparation method comprises the following steps:

[0016] S1: dissolving a phosphorus source, a ruthenium source, and a gadolinium source in water to obtain a mixed solution A;

[0017] S2: adding graphite to the mixed solution A and dispersing it evenly to obtain a mixed solution B;

[0018] S3: Drying the mixed solution B and calcining to obtain the target P-Ru-Gd catalyst.

[0019] In one embodiment of the present invention, the phosphorus source in S1 is a phosphoric acid source, preferably one or more of phosphoric acid, trimethyl phosphate, dimethyl phosphate, sodium dihydrogen phosphate, and potassium dihydrogen phosphate.

[0020] In one embodiment of the present invention, the ruthenium source in S1 is one or more of ruthenium oxide, ruthenium trichloride, ruthenium triiodide, ruthenium oxide, and ruthenium acetate.

[0021] In one embodiment of the present invention, the gadolinium source in S1 is a gadolinium salt, preferably one or more of gadolinium nitrate, gadolinium nitrate hexahydrate, gadolinium chloride, and gadolinium sulfate; preferably, the molar ratio of the metal elements in the phosphorus source, ruthenium source, and gadolinium source is phosphorus:ruthenium:gadolinium = (1-1.5): (0.5-0.8): (0.1-0.2).

[0022] In one embodiment of the present invention, the amount of graphite added to S2 is 5-20 times the total mass of the phosphorus source, ruthenium source and gadolinium source; preferably, the graphite is added in batches, preferably 3-5 times, and the addition interval is 20-40 minutes.

[0023] In one embodiment of the present invention, the dispersing process in S2 is ultrasonic dispersion, and the ultrasonic frequency is 20-40 kHz; preferably, the ultrasonic dispersion temperature is 20-40° C., and the dispersion time is 2-5 h.

[0024] In one embodiment of the present invention, the drying in S3 is carried out under a nitrogen atmosphere at a drying temperature of 40-60° C. and a drying time of 24-72 h.

[0025] In one embodiment of the present invention, the calcination in S3 is carried out under a nitrogen atmosphere at a temperature of 350-550° C. and a calcination time of 4-10 h.

[0026] Another object of the present invention is to provide a graphite-supported P-Ru-Gd catalyst

[0027] A graphite-supported P-Ru-Gd catalyst, wherein the P-Ru-Gd catalyst is the catalyst used in the above method, or is the catalyst prepared by the above preparation method, and the molar ratio of the metal elements in the catalyst is phosphorus:ruthenium:gadolinium=(1-1.5):(0.5-0.8):(0.1-0.2).

[0028] Another object of the present invention is to provide a kind of p-Hydroxyanisole.

[0029] The invention discloses p-hydroxyanisole, which is prepared by the method or catalytically prepared by the catalyst.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The catalyst can obtain p-hydroxyanisole under conditions of high conversion rate and selectivity, wherein the conversion rate of hydroquinone can reach up to 80% and the selectivity of p-hydroxyanisole is 95%.

[0032] (2) The fixed bed process is used for the reaction. The gasification section first gasifies the raw materials into a gaseous state to prevent the liquid from entering the reaction section, thus ensuring that the activity and stability of the catalyst are not affected. The catalyst can operate stably for more than 2000 hours and has prospects for industrial application. DETAILED DESCRIPTION

[0033] In order to better understand the present invention, the content of the present invention is further described below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.

[0034] In the following examples, the conversion rate of hydroquinone and the selectivity of p-hydroxyanisole can be calculated based on the composition of the reaction solution. The analysis method adopts gas chromatography, and the instrument is Shimadzu GC-2030 gas chromatograph.

[0035] Sources of some raw materials used:

[0036] Hydroquinone, phosphoric acid, trimethyl phosphate, sodium dihydrogen phosphate, ruthenium trichloride, ruthenium oxide, ruthenium acetate, gadolinium nitrate, gadolinium chloride: Aladdin Technology Co., Ltd.;

[0037] Methanol and acetonitrile: Beijing Inokai Technology Co., Ltd.

[0038] Example 1

[0039] Preparation of catalyst:

[0040] (1) Dissolve 9.80 g of phosphoric acid, 10.35 g of ruthenium trichloride, and 3.43 g of gadolinium nitrate in 500 g of water, stirring and mixing until uniform; ensure that the molar ratio of the metal elements in the compound is phosphorus: ruthenium: gadolinium = 1:0.5:0.1.

[0041] (2) placing the above-mentioned mixed solution in an ultrasonic environment, and slowly adding 235.8 g of graphite (10 times the total mass of the above-mentioned phosphorus source, ruthenium source, and gadolinium source) into the mixed solution in three portions, each with an interval of 20 minutes, and ultrasonically dispersing the mixture at 25°C for 3 hours to ensure that the graphite is evenly dispersed, wherein the ultrasonic frequency is 30 kHz;

[0042] (3) Drying the above liquid in a nitrogen atmosphere at a drying temperature of 45°C for 36 hours;

[0043] (4) The solid obtained after drying was calcined in a nitrogen atmosphere to obtain a P-Ru-Gd catalyst at a calcination temperature of 400°C and a calcination time of 5 h.

[0044] Fixed bed continuous reaction conditions of hydroquinone and methanol:

[0045] The molar ratio of hydroquinone to methanol is 1:8, and the mass space velocity of hydroquinone in the raw material liquid is 0.1h -1 The temperature of the gasification section of the fixed-bed continuous reactor is 280°C, the temperature of the reaction section is 220°C, and the temperature of the insulation section is 180°C.

[0046] After the reaction stabilized under the above conditions, a sample of 2 ml was taken. The sample was diluted 10 times with acetonitrile and then the composition of the reaction solution was analyzed by gas chromatography. The conversion rate of hydroquinone was calculated to be 69%, and the selectivity of p-hydroxyanisole was 92%.

[0047] Example 2

[0048] Preparation of catalyst:

[0049] (1) Dissolve 16.80 g of trimethyl phosphate, 9.31 g of ruthenium oxide, and 5.15 g of gadolinium nitrate in 500 g of water, stirring and mixing until uniform; ensure that the molar ratio of the metal elements in the compound is phosphorus: ruthenium: gadolinium = 1.2:0.7:0.15.

[0050] (2) placing the above-mentioned mixed solution in an ultrasonic environment, and slowly adding 468.9 g of graphite (15 times the total mass of the above-mentioned phosphorus source, ruthenium source, and gadolinium source) into the mixed solution in four portions, each with an interval of 30 minutes, and ultrasonically dispersing at 35°C for 4 hours to ensure that the graphite is evenly dispersed, wherein the ultrasonic frequency is 20 kHz;

[0051] (3) Drying the above-mentioned liquid under nitrogen atmosphere at a drying temperature of 55°C for 48 hours;

[0052] (4) The solid obtained after drying was calcined in a nitrogen atmosphere to obtain a P-Ru-Gd catalyst at a calcination temperature of 500°C and a calcination time of 8 h.

[0053] Fixed bed continuous reaction conditions of hydroquinone and methanol:

[0054] The molar ratio of hydroquinone to methanol is 1:10, and the mass space velocity of hydroquinone in the raw material liquid is 0.3h -1 The temperature of the gasification section of the fixed-bed continuous reactor is 310°C, the temperature of the reaction section is 240°C, and the temperature of the insulation section is 190°C.

[0055] After the reaction stabilized under the above conditions, a sample of 2 ml was taken. The sample was diluted 10 times with acetonitrile and then the composition of the reaction solution was analyzed by gas chromatography. The conversion rate of hydroquinone was calculated to be 80%, and the selectivity of p-hydroxyanisole was 95%.

[0056] Example 3

[0057] Preparation of catalyst:

[0058] (1) Dissolve 18.00 g of sodium dihydrogen phosphate, 13.90 g of ruthenium acetate, and 3.42 g of gadolinium chloride in 500 g of water, stirring and mixing until uniform; ensure that the molar ratio of the metal elements in the compound is phosphorus: ruthenium: gadolinium = 1.5:0.5:0.13.

[0059] (2) placing the above-mentioned mixed solution in an ultrasonic environment, and slowly adding 706.4 g of graphite (20 times the total mass of the above-mentioned phosphorus source, ruthenium source, and gadolinium source) into the mixed solution in 5 times, each time with an interval of 20 minutes, and ultrasonically dispersing at 40°C for 5 hours to ensure that the graphite is evenly dispersed, wherein the ultrasonic frequency is 35 kHz;

[0060] (3) Drying the above liquid in a nitrogen atmosphere at a drying temperature of 60°C for 60 h;

[0061] (4) The solid obtained after drying was calcined in a nitrogen atmosphere to obtain a P-Ru-Gd catalyst at a calcination temperature of 550°C and a calcination time of 10 h.

[0062] Fixed bed continuous reaction conditions of hydroquinone and methanol:

[0063] The molar ratio of hydroquinone to methanol is 1:12, and the mass space velocity of hydroquinone in the raw material liquid is 0.8h -1 The temperature of the gasification section of the fixed-bed continuous reactor is 330°C, the temperature of the reaction section is 260°C, and the temperature of the insulation section is 200°C.

[0064] After the reaction stabilized under the above conditions, a sample of 2 ml was taken. The sample was diluted 10 times with acetonitrile and then the composition of the reaction solution was analyzed by gas chromatography. The conversion rate of hydroquinone was calculated to be 75%, and the selectivity of p-hydroxyanisole was 88%.

[0065] Comparative Example 1

[0066] The catalyst was prepared in the same manner as in Example 2, with the main differences being that no gadolinium source was added, the molar ratio of the metal elements in the phosphorus source and ruthenium source was phosphorus:ruthenium = 1.2:0.7, and the amount of graphite added was 15 times the total mass of the phosphorus source and ruthenium source. Other preparation and reaction conditions were the same as in Example 2.

[0067] After the reaction stabilized under the above conditions, a sample of 2 ml was taken. The sample was diluted 10 times with acetonitrile and then the composition of the reaction solution was analyzed by gas chromatography. The conversion rate of hydroquinone was calculated to be 35%, and the selectivity of p-hydroxyanisole was 68%.

[0068] Although the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description is not intended to limit the present invention. Those skilled in the art will appreciate that, based on the teachings of this specification, modifications or adjustments may be made to the present invention. Such modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A method for gas phase synthesis of p-hydroxyanisole, characterized in that, The method adopts a graphite-supported P-Ru-Gd catalyst to catalyze the synthesis of p-hydroxyanisole from hydroquinone and methanol under gas phase conditions.

2. The method according to claim 1, characterized in that The method adopts a fixed bed continuous reactor, wherein the reactor comprises a gasification section, a reaction section and a heat preservation section; And / or, in the method, the raw materials are first gasified in the gasification section, then enter the reaction section containing the catalyst to react, and then enter the storage tank through the insulation section to condense to obtain the reaction liquid; and / or, the molar ratio of hydroquinone to methanol in the method is 1:(5-12); And / or, in the method, the mass space velocity of the raw material liquid based on hydroquinone is 0.06-1.5h -1 .

3. The method according to claim 2, characterized in that The temperature of the gasification section is 260-350°C, the temperature of the reaction section is 200-260°C, and the temperature of the insulation section is 170-200°C.

4. A method for preparing a graphite-supported P-Ru-Gd catalyst, wherein the P-Ru-Gd catalyst is the catalyst used in the method according to any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: S1: dissolving a phosphorus source, a ruthenium source, and a gadolinium source in water to obtain a mixed solution A; S2: adding graphite to the mixed solution A and dispersing it evenly to obtain a mixed solution B; S3: Drying the mixed solution B and calcining to obtain the target P-Ru-Gd catalyst.

5. The preparation method according to claim 4, characterized in that The phosphorus source in S1 is a phosphoric acid-based phosphorus source; and / or, the ruthenium source in S1 is one or more of ruthenium oxide, ruthenium trichloride, ruthenium triiodide, ruthenium oxide, and ruthenium acetate; And / or, the gadolinium source in S1 is a gadolinium salt.

6. The preparation method according to claim 5, characterized in that The phosphorus source in S1 is one or more of phosphoric acid, trimethyl phosphate, dimethyl phosphate, sodium dihydrogen phosphate, and potassium dihydrogen phosphate; and / or, the gadolinium source in S1 is one or more of gadolinium nitrate, gadolinium nitrate hexahydrate, gadolinium chloride, and gadolinium sulfate; The molar ratio of the metal elements in the phosphorus source, ruthenium source and gadolinium source in S1 is phosphorus:ruthenium:gadolinium = (1-1.5):(0.5-0.8):(0.1-0.2).

7. The preparation method according to claim 4, characterized in that The amount of graphite added in S2 is 5-20 times the total mass of the phosphorus source, ruthenium source and gadolinium source; And / or, the dispersing process in S2 is ultrasonic dispersion, and the ultrasonic frequency is 20-40 kHz.

8. The preparation method according to claim 7, characterized in that Graphite in S2 is added in batches; The temperature of ultrasonic dispersion in S2 is 20-40°C, and the dispersion time is 2-5h.

9. The preparation method according to claim 8, characterized in that In S2, graphite is added in batches of 3-5 times, with an addition interval of 20-40 minutes.

10. The preparation method according to claim 4, characterized in that The drying in S3 is carried out under a nitrogen atmosphere at a temperature of 40-60° C. and a drying time of 24-72 h; And / or, the calcination in S3 is carried out under a nitrogen atmosphere at a temperature of 350-550° C. and a calcination time of 4-10 h.

11. A graphite-supported P-Ru-Gd catalyst, wherein the P-Ru-Gd catalyst is the catalyst used in the method according to any one of claims 1 to 3, or the catalyst prepared by the preparation method according to any one of claims 4 to 10, characterized in that: The molar ratio of the metal elements in the catalyst is phosphorus:ruthenium:gadolinium=(1-1.5):(0.5-0.8):(0.1-0.2).