A method for separating and regenerating a phenol hydroxylation catalyst

Abstract

The invention discloses a method for separating and regenerating a phenol hydroxylation catalyst. The method performs two-stage solid-liquid separation on a phenol hydroxylation reaction liquid containing phenol, a solvent, water, catechol, hydroquinone, tar and a catalyst, wherein the solid content in the liquid is less than 100 ppm. The separated catalyst is directly subjected to a multi-stage regeneration treatment using a solvent to remove heavy component impurities such as tar. The entire process is continuously operated, has simple and efficient operation, can avoid catalyst separation loss, and the regenerated catalyst can reach a fresh catalyst level. The method is particularly suitable for large-scale industrial production.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis and relates to a method for separating and regenerating a phenol hydroxylation catalyst. Background Art

[0002] The technology of producing o- and hydroquinone by hydroxylation of phenol with hydrogen peroxide as oxidant has become a hot topic of research and development due to its simple process flow, mild reaction conditions, mature catalytic technology and low environmental pollution. For the reaction liquid of phenol hydroxylation, the separation tasks mainly include separating the catalyst, recovering the solvent, dehydrating, recovering phenol, refining the o- and hydroquinone products, etc., among which the separation of the catalyst has a great influence on the subsequent separation and purification. If the catalyst separation is not thorough and is brought into the distillation device, it may cause equipment damage, abnormal material transportation, tar more likely to agglomerate, affecting product quality and other problems. Therefore, the solid-liquid separation of the catalyst and the reaction liquid is very critical. Patent CN109956852A discloses a method for preparing o- and hydroquinone by hydroxylation of phenol. After the solid catalyst is intercepted by an inorganic membrane or a vibrating membrane, the reaction liquid enters a molecular sieve membrane for dehydration. The biggest feature of this process is the use of a molecular sieve membrane for water separation in the separation stage, which can significantly reduce separation energy consumption. However, direct membrane dehydration of the reaction liquid containing a large amount of tar will cause clogging of the separation membrane. The liquid phase feed does not provide vaporization conditions and does not meet the requirements for the use of the molecular sieve membrane, making it unfeasible for engineering implementation. Patent CN114920626A discloses a high-efficiency separation method for phenol hydroxylation reaction liquid. The method uses a membrane separation device to pre-separate the reaction liquid by pressurized distillation, dehydrate it through a separation membrane, and then remove the tar and catalyst from the kettle liquid by vacuum distillation. This method can avoid clogging of the dehydration separation membrane by tar and catalyst, but the energy consumption of separating the catalyst by a distillation tower is high, and after separation together with the tar, the catalyst and tar are tightly coated, making it difficult to reuse.

[0003] During the phenol hydroxylation reaction, more tar will be generated, and tar will be adsorbed on the catalyst surface, blocking the internal and external pores of the catalyst, thereby deactivating the catalyst and requiring regeneration. Regarding the regeneration of titanium silicon molecular sieve, patent CN102309981B stirs the deactivated titanium silicon molecular sieve with an organic base, titanium silicon solution or water vapor in a closed kettle for 2h to obtain a molecular sieve after regeneration, which is substantially restored to the level of fresh catalyst. Patent CN105665002A provides a method for catalyst regeneration, in which the deactivated titanium silicon molecular sieve is reacted successively with an acidic solution and an alkaline solution containing a cation trapping agent, and the purpose of regeneration is reached after washing, drying and roasting. As can be seen from the above patents, although the regeneration methods mentioned can all make the catalyst activity recover to or near the level before deactivation, there are complex operations, complex processes, more reagents used, high regeneration costs, and shortcomings such as easy loss of catalyst disassembly and assembly process. In addition, the phenol hydroxylation reaction has the characteristics of large tar production, fast catalyst deactivation, and frequent regeneration, and complicated processes cannot meet industrial requirements.

[0004] Patent CN113304773 provides a method for in-vehicle regeneration of deactivated titanium silicalite molecular sieves. This method addresses the phenol hydroxylation reaction, where the catalyst is prone to tar adsorption and deactivation. The method utilizes a solvent to wash the organic matter, followed by a peroxide catalyst to decompose the tar and dissolve small molecules. The entire regeneration process takes place within the reactor, resulting in a continuous reaction that avoids complex catalyst disassembly and assembly. After regeneration, the catalyst's performance reaches the level of a fresh catalyst. However, the peroxide used in the regeneration process may remain in the reactor. Due to its strong oxidizing properties, it reacts with the raw materials before any oxidant is added, producing a large amount of byproducts.

[0005] Compared with the above-mentioned patented technical solutions, the method for separating and regenerating the phenol hydroxylation catalyst of the present invention has a continuous and efficient solid-liquid separation process without the need for complex distillation operations. The catalyst regeneration process does not require the addition of other reagents and a calcination process. Instead, the effective regeneration of the catalyst can be achieved by relying on the solvent of the process itself and an enhanced mass transfer method. The process is economical and has strong applicability, and can provide an important approach for the industrialized continuous production of phenol hydroxylation. Summary of the Invention

[0006] The present invention addresses the problems of the prior art by providing a method for separating and regenerating a phenol hydroxylation catalyst. This method utilizes a two-stage separation process, combining improved spiral filter press technology with a membrane separation device to achieve continuous and efficient solid-liquid separation, eliminating the need for complex distillation operations and improving industrial production efficiency.

[0007] A further purpose of this method is that, through the method of the present invention, the catalyst adopts a multi-stage regeneration process, and the regeneration process does not require the addition of other reagents or the use of a high-temperature calcination process. By relying on the solvent of the process itself and the method of enhancing mass transfer, the effective regeneration of the catalyst can be achieved, and the reaction performance can reach the level of fresh agent, effectively improving the safety and economy of existing industrial production.

[0008] To achieve the above object, the technical solution adopted by the present invention is:

[0009] A method for separating and regenerating a phenol hydroxylation catalyst is carried out according to the following steps:

[0010] (1) subjecting a phenol hydroxylation reaction liquid containing phenol, solvent, water, catechol, hydroquinone, tar and catalyst to two-stage solid-liquid separation, wherein the first stage is a spiral rotary filter press to perform preliminary separation on the initial reaction liquid;

[0011] (2) After the first stage separation, the second stage separation is carried out, and the separation method is membrane tube separation. After separation, the catalyst and the reaction liquid can be completely separated, and the solid content in the liquid is <100ppm;

[0012] (3) The separated catalyst is directly regenerated in a multi-stage process using the clean solvent used in the reaction process. The first stage is ultrasonic immersion regeneration to remove most of the attached organic matter and tar. The second stage is leaching regeneration. The catalyst is continuously rinsed with solvent sprayed around it during the transfer process to further remove impurities on the catalyst.

[0013] (4) Finally, the catalyst enters the third stage of microwave drying and regeneration to deeply dry the light components, solvent and water remaining in the catalyst. The regenerated catalyst can be reloaded into the reactor for reaction.

[0014] The catalyst content in the phenol hydroxylation reaction solution accounts for 5-30% of the reaction solution.

[0015] The catalyst includes titanium silicon molecular sieve TS-1, tin silicon molecular sieve, molybdate, tungstate, perchlorate, and titanium silicon molecular sieve catalyst HTS-1.

[0016] The first-stage separation device is a spiral filter press, comprising a feed inlet, a solids discharge port, a liquid discharge port, a chamber, a screw, a filter membrane, and a rotating motor. The filter membrane used in the spiral filter press has a pore size of 2-20 μm. After the first-stage solid-liquid separation, the solids content in the liquid is 200-1000 ppm.

[0017] The first stage solid-liquid separation method can also be plate filter press or pressure filter press to perform preliminary separation on the initial reaction liquid; spiral filter press is preferred.

[0018] The second-stage solid-liquid separation device is a membrane tube separation device, comprising a circulation tank, a membrane filter, a backwash tank, a circulation pump, and a backwash pump. The membrane tubes used in the second-stage solid-liquid separation device have a pore size of 50-200 nm. After the second-stage solid-liquid separation, the solid content in the liquid is 0-100 ppm.

[0019] The solvent is one or more of acetone, butanone, methanol, ethanol, propanol, n-butanol, isobutanol, acetonitrile, butyronitrile, 1,4-dioxane, and water. The mass ratio of fresh solvent to catalyst used for the first stage regeneration is 10-100:1, and the solvent mass space velocity is 1-10h -1 The mass ratio of fresh solvent to catalyst used for the second stage regeneration is 20-200:1, and the mass space velocity of the solvent is 5-15h -1 The catalyst is deeply dried by microwave heating for the third stage regeneration, the microwave heating temperature is controlled at 80-200°C, and the power of the microwave device reactor is adjusted to control the heating rate at 0.5-20°C / min.

[0020] The process flow includes different functional areas such as the feeding system, the secondary separation system, the tertiary regeneration system, and the product collection system.

[0021] Compared with the prior art, the present invention has the following main advantages:

[0022] 1. The present invention adopts a method for separating and regenerating a phenol hydroxylation catalyst. This process incorporates a two-stage solid-liquid separation method, improves the spiral filter press technology, and combines it with a membrane separation device to make the solid-liquid separation process continuous and efficient. The solid content of the liquid after separation is <100ppm. The separation process does not require complex distillation operations, further improving industrial production efficiency.

[0023] 2. The catalyst utilizes a multi-stage regeneration process. This process does not require the addition of other reagents or high-temperature calcination. Instead, the process utilizes the solvent itself, along with enhanced mass transfer, to achieve effective catalyst regeneration. The regenerated catalyst's performance reaches the same level as fresh catalyst, effectively improving the safety and economic efficiency of existing industrial production.

[0024] 3. The entire process is simple, highly operable, safe, reliable, clean and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the process flow for continuous separation and regeneration of phenol hydroxylation catalyst.

[0026] Figure 2 Schematic diagram of the spiral filter press device.

[0027] Figure 3 Schematic diagram of membrane tube separation device. DETAILED DESCRIPTION

[0028] The present invention is described in detail below with reference to examples and comparative examples. The following examples are preferred implementations of the present invention, and the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed in the present invention, who makes equivalent substitutions or changes to the technical solutions and concepts according to the present invention, should all be covered by the protection scope of the present invention.

[0029] In the following examples and comparative examples, the composition and content of the products were analyzed by gas chromatography, and the conversion rate of phenol and the effective utilization rate of hydrogen peroxide were calculated using the following formulae, respectively.

[0030] X 苯酚 =[(m 0 苯酚 -m 苯酚 ) / m 0 苯酚 ]×100% (Ⅰ)

[0031] In Formula Ⅰ, X 苯酚 represents the conversion rate of phenol;

[0032] m 0 苯酚 represents the number of moles of phenol added;

[0033] m 苯酚 represents the number of moles of unreacted phenol.

[0034] X 双氧水 =[(m 0 过氧化氢 -m 过氧化氢 ) / m 0 过氧化氢 ]×100% (Ⅱ)

[0035] In formula II, X 双氧水 represents the conversion rate of hydrogen peroxide;

[0036] m 0 过氧化氢 Indicates the mass of hydrogen peroxide added;

[0037] m 过氧化氢 Indicates the mass of unreacted hydrogen peroxide.

[0038] Example 1

[0039] Reference Figure 1The product composition after the phenol hydroxylation reaction is 56% solvent acetone, 8% water, 18% phenol, 1% catechol, 12% hydroquinone, 5% tar, and 5% catalyst. The material enters the first-stage separation spiral filter press device with a 10μm pore size filter membrane. After separation, the solid content in the liquid is 200ppm. It enters the second-stage ceramic membrane separation device with a 50nm pore size. After separation, the solid content in the liquid is 20ppm. The catalyst undergoes the first-stage regeneration device and is regenerated with acetone. At this time, the mass ratio of acetone to catalyst is 10:1, and the solvent mass space velocity is 2h. -1 The catalyst is then transferred to the second stage regeneration unit, where the mass ratio of acetone to catalyst is 20:1 and the mass space velocity of the solvent is 5h -1 Finally, the catalyst was deeply dried by microwave heating, the microwave heating temperature was controlled at 120°C, and the power of the microwave device reactor was controlled to control the heating rate at 10°C / min.

[0040] The separated and regenerated catalyst was returned to the reaction unit to obtain a phenol hydroxylation product. The product composition was analyzed by gas chromatography, and the phenol conversion rate and the effective utilization rate of the oxidant were calculated. The data are listed in Table 2.

[0041] Example 2

[0042] The product composition after the phenol hydroxylation reaction is 56% solvent acetone, 8% water, 18% phenol, 1% catechol, 12% hydroquinone, 5% tar, and 10% catalyst. The material enters the first-stage separation spiral filter press, using a 5μm pore size filter membrane. After separation, the solid content in the liquid is 500ppm. It enters the second-stage ceramic membrane separation device, using a 200nm pore size filter membrane. After separation, the solid content in the liquid is 50ppm. The catalyst undergoes a first-stage regeneration device, where it is regenerated with acetone. At this point, the mass ratio of acetone to catalyst is 20:1, and the solvent mass space velocity is 4h / min. -1 The catalyst is then transferred to the second stage regeneration unit, where the mass ratio of acetone to catalyst is 40:1 and the mass space velocity of the solvent is 10h -1 Finally, the catalyst was deeply dried by microwave heating, the microwave heating temperature was controlled at 150°C, and the power of the microwave device reactor was controlled to control the heating rate at 15°C / min.

[0043] The separated and regenerated catalyst was returned to the reaction unit to obtain a phenol hydroxylation product. The product composition was analyzed by gas chromatography, and the phenol conversion rate and the effective utilization rate of the oxidant were calculated. The data are listed in Table 2.

[0044] Comparative Example 1

[0045] TS-1 catalyst, phenol and methanol were added to the reactor, circulated with cooling and reflux, heated to boiling, and 50% hydrogen peroxide solution was slowly added dropwise. The reaction was stopped after keeping warm for 10 hours. The material was discharged and sent to the pressurized filter press equipment for solid-liquid separation at a pressure of 0.6 MPa. After separation, the catalyst was returned to the reactor, and the feed liquid was sent to the refining system for separation and purification. The solid content of the feed liquid after filter press was tested and the results are listed in Table 1.

[0046] Comparative Example 2

[0047] The product of the phenol hydroxylation reaction was used, and the reactor was loaded with 100g of catalyst TS-1. At room temperature and pressure, 10kg of acetone was injected into the reactor at a rate of 400g / h to wash the deactivated catalyst. 10g of catalyst TS-1 was mixed with 2kg of a 27% hydrogen peroxide solution and injected into the reactor at a rate of 300g / h at 70°C to decompose the tar on the deactivated catalyst. At room temperature and pressure, 10kg of cumene was injected into the reactor at a rate of 300g / h to clean the small molecule products produced by the tar decomposition. Through the above steps, the deactivated TS-1 catalyst was regenerated. The regenerated catalyst was then fed with the phenol hydroxylation reaction feedstock. The results are listed in Table 2.

[0048] Comparative Example 3

[0049] Amorphous silica gel and tetrapropylammonium hydroxide (TPAH) were mixed in measured amounts, and distilled water was added. After mixing, the mixture was stirred at room temperature for 1.5 hours. Nibutyl titanate was then added and stirred for 0.5 hours. The mixture was then stirred at 75°C for 3 hours to produce a regeneration solution. 12 grams of deactivated TS-1 molecular sieve catalyst was mixed with 60 grams of the regeneration solution and reacted in a sealed autoclave at 175°C for 52 hours. The resulting product was filtered, washed, dried at 180°C for 120 minutes, and then calcined at 650°C for 2 hours to obtain a hydrothermally regenerated molecular sieve catalyst. The regenerated catalyst was then fed with the raw materials for the hydroxylation of phenol. The reaction results are listed in Table 2.

[0050] Table 1

[0051] Example No. Solid content after filtration ppm Example 1 200 Example 2 500 Comparative Example 1 2000

[0052] Table 2

[0053] Example No. Phenol conversion rate% Hydrogen peroxide conversion rate% Freshener 45.02 98.26 Example 1 44.32 97.92 Example 2 44.09 97.96 Comparative Example 2 25.26 90.05 Comparative Example 3 24.75 92.51

Claims

1. A method for separating and regenerating a phenol hydroxylation catalyst, comprising the steps of: (1) subjecting the phenol hydroxylation reaction liquid containing phenol, solvent, water, catechol, hydroquinone, tar and catalyst to two-stage solid-liquid separation, wherein the first stage of solid-liquid separation is a spiral rotary filter press to perform preliminary separation on the initial reaction liquid; (2) After the first stage of solid-liquid separation, the product enters the second stage of solid-liquid separation. The separation method is membrane tube separation. After separation, the catalyst and the reaction liquid can be completely separated, and the solid content in the liquid is <100ppm; (3) The separated catalyst is directly subjected to multi-stage regeneration treatment using solvents. The first stage of regeneration is ultrasonic immersion regeneration to remove most of the attached organic matter and tar. The second stage of regeneration is leaching regeneration. During the transfer process, the catalyst is continuously rinsed with solvents sprayed around it to further remove impurities on the catalyst. (4) Finally, the catalyst enters the third stage of regeneration, which is microwave drying regeneration. The light components, solvents and water remaining in the catalyst are deeply dried. The regenerated catalyst can be reloaded into the reactor for reaction.

2. The method for separating and regenerating the phenol hydroxylation catalyst according to claim 1, wherein The weight content of the catalyst in the phenol hydroxylation reaction solution accounts for 5-30% of the reaction solution.

3. The method for separation and regeneration of phenol hydroxylation catalyst according to claim 1, wherein The catalyst is one or more combinations of titanium silicon molecular sieve TS-1, tin silicon molecular sieve, molybdate, tungstate, perchlorate, and titanium silicon molecular sieve catalyst HTS-1.

4. The method for separation and regeneration of phenol hydroxylation catalyst according to claim 1, wherein The first-stage solid-liquid separation spiral filter press device includes a feed port, a solid discharge port, a liquid discharge port, a cavity, a screw, a filter membrane, and a rotating motor; the pore size of the filter membrane used in the spiral filter press device is 2-20 μm.

5. The method for separation and regeneration of phenol hydroxylation catalyst according to claim 4, wherein After the first stage solid-liquid separation, the solid content in the liquid is 100-1000 ppm.

6. The method for separation and regeneration of phenol hydroxylation catalyst according to claim 1, wherein The membrane tube separation device for the second stage solid-liquid separation mainly includes a circulation tank, a membrane filter, a backwash tank, a circulation pump, and a backwash pump; the pore size of the membrane tube used in the second stage solid-liquid separation membrane tube separation device is 50-200nm.

7. The method for separation and regeneration of phenol hydroxylation catalyst according to claim 6, wherein After the second stage solid-liquid separation, the solid content in the liquid is 10-100 ppm.

8. The method for separation and regeneration of phenol hydroxylation catalyst according to claim 1, wherein The solvent used for catalyst regeneration is one or more of acetone, butanone, methanol, ethanol, propanol, n-butanol, isobutanol, acetonitrile, butyronitrile, 1,4-dioxane, and water.

9. The method for separation and regeneration of phenol hydroxylation catalyst according to claim 1, wherein In the first stage regeneration, the mass ratio of fresh solvent to catalyst is 10-100:1, and the mass space velocity of the solvent is 1-10h -1 In the second stage regeneration, the mass ratio of fresh solvent to catalyst is 20-200:1, and the mass space velocity of the solvent is 5-15h -1 In the third stage regeneration, the microwave heating temperature is controlled to be 80-200°C, and the power of the microwave device reactor is adjusted to control the heating rate to be 0.5-20°C / min.

10. The method for separating and regenerating a phenol hydroxylation catalyst according to claim 1, wherein The process flow of the method includes different functional areas such as a feeding system, a secondary separation system, a tertiary regeneration system, and a product collection system.

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