In-situ regeneration method of a catalyst for preparing benzene by dehydrogenation of cyclohexane

Abstract

This invention discloses an in-situ regeneration method for a cyclohexane dehydrogenation catalyst to benzene, relating to the field of industrial catalysis. The method includes the following steps: cleaning the deactivated catalyst with a surface-active amine polymer solution; cleaning the deactivated catalyst again with an alkali metal chloride aqueous solution; drying the cleaned catalyst under an inert atmosphere; performing preliminary carbonization of the catalyst by heating under an oxygen-containing atmosphere; continuing to heat and increase the oxygen content for secondary carbonization; and reducing the decarbonized catalyst under a hydrogen atmosphere. This invention utilizes the synergistic effect of the amine polymer and the secondary cleaning with alkali metal chloride to soften the graphite-like carbon deposits on the surface of the spent catalyst while simultaneously completing the chlorination step. This eliminates the need for a separate chlorination activation step required in traditional regeneration methods, simplifying the process and reducing energy consumption. After five regeneration cycles, the regenerated catalyst maintains a stable conversion rate of over 95% for cyclohexane dehydrogenation and a selectivity of over 99.7%.

Description

Technical Field

[0001] This invention relates to the field of industrial catalysis technology, specifically to an in-situ regeneration method for a catalyst used in the dehydrogenation of cyclohexane to benzene. Background Technology

[0002] Cyclohexane is a crucial industrial raw material, serving as a primary intermediate in the production of caprolactam and adipic acid, and is used to manufacture nylon 6, nylon 66, and other fine chemicals. According to publicly available information, the global cyclohexanone market reached 59.15 billion yuan in 2022, with an annual growth rate of 3.59%, and is projected to reach 71.12 billion yuan by 2028. Therefore, the continuously growing demand necessitates the development of green chemistry processes for cyclohexanone.

[0003] In recent years, with the increasing demand for caprolactam, a downstream product of cyclohexanone, a mature industrial chain has been formed, consisting of benzene-cyclohexene-cyclohexanol-cyclohexanone-caprolactam. In the process of producing cyclohexene by hydrogenating benzene, a large amount of cyclohexane is produced as a byproduct. Due to the limited downstream market for cyclohexane, its added value is low. Therefore, regenerating benzene from cyclohexane through dehydrogenation can effectively improve raw material utilization and achieve a greener cyclohexanone process. Furthermore, due to the price inversion between cyclohexane and benzene, and the current supply shortage of benzene caused by the rapid expansion of downstream production capacity, a seller's market has emerged. Developing a cyclohexane dehydrogenation process to produce benzene will have extremely high economic value.

[0004] The process and catalysts for cyclohexane dehydrogenation to benzene have been extensively studied. Since Guizhou Research Institute of Industrial Catalysts (Yunnan) Co., Ltd. first industrialized a cyclohexane dehydrogenation catalyst in 2023, several caprolactam manufacturers in China have adopted the cyclohexane dehydrogenation to benzene process, achieving breakthrough progress in this field. Cyclohexane dehydrogenation catalysts are mainly platinum-based, with initial conversion rates >95% and selectivity >99%. However, after 18 months of operation, the activity of these catalysts typically decreases significantly due to the continuous accumulation of carbon deposits. Therefore, regeneration methods for these catalysts have become one of the key means to solve the problem of catalyst deactivation in industrial applications.

[0005] Currently, common industrial methods for regenerating alkane dehydrogenation catalysts include high-temperature carbonization-chlorination regeneration processes. For example, CN1589970A discloses a regeneration method for a catalyst used in the dehydrogenation of alkane aromatics to produce alkenyl aromatics. This method requires a high regeneration temperature (>500°C). If the regeneration temperature is below 500°C, carbon deposits are difficult to completely remove, thus affecting regeneration performance. CN1541140A discloses a regeneration method for a dehydrogenation catalyst, which achieves regeneration by changing the oxygen concentration, regeneration pressure, and space velocity. This regeneration method is prone to the accumulation of active metals. CN101940959A discloses a regeneration method for a low-carbon alkane dehydrogenation catalyst. This method first regenerates the catalyst in an air atmosphere at a lower temperature to burn off carbon deposits on the catalyst surface and most of the carbon deposits inside the pores. Then, the catalyst is further regenerated in a mixed atmosphere of water vapor and air. CN104084218A discloses a method for regenerating platinum-based alkane dehydrogenation catalysts through a process involving staged carbonization, followed by soaking in a chloride aqueous solution, calcination in air, and finally reduction with hydrogen. All of these regeneration methods require high-temperature carbonization processes, which pose a risk of metal accumulation.

[0006] Cyclohexane dehydrogenation to benzene production is mainly divided into two processes: high-temperature dehydrogenation and low-temperature dehydrogenation. Compared with high-temperature dehydrogenation, low-temperature dehydrogenation has lower energy consumption and investment, making it more favored by industry and more widely used. However, for the low-temperature cyclohexane dehydrogenation process, the heat transfer oil is limited by its operating temperature (≤350℃), while the regeneration of alkane dehydrogenation catalysts typically requires high-temperature (≥450℃) carbonization. Therefore, in-situ regeneration of cyclohexane dehydrogenation catalysts at low temperatures presents significant challenges, and there are currently no reports on the in-situ regeneration of cyclohexane dehydrogenation catalysts at low temperatures. Summary of the Invention

[0007] The purpose of this invention is to overcome the above-mentioned shortcomings and provide an in-situ regeneration method for cyclohexane dehydrogenation to benzene catalyst. This method uses a lower carbonization temperature, which significantly reduces energy consumption and effectively overcomes the technical bottleneck of in-situ high-temperature regeneration that cannot be performed due to the temperature limitation of heat transfer oil in industrial plants. At the same time, the low-temperature conditions avoid the aggregation of precious metal active components and eliminate the chlorination activation step required in traditional regeneration methods.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0009] A method for in-situ regeneration of a catalyst for the dehydrogenation of cyclohexane to benzene includes the following steps:

[0010] S100. Clean the deactivated catalyst on the device using a surface-active amine polymer solution;

[0011] S200. The deactivated catalyst on the device is cleaned again using an alkali metal chloride aqueous solution.

[0012] The cleaned catalyst was dried under an inert atmosphere at S300.

[0013] Under an oxygen-containing atmosphere (S400), the catalyst is initially carbonized by heating; the temperature is then increased and the oxygen content is further increased to perform a secondary carbonization.

[0014] Under S500 and hydrogen atmosphere, the decarbonized catalyst is reduced;

[0015] The amine polymer molecular chain contains both a hydrophobic organic segment and at least one hydrophilic amino group.

[0016] Traditional methods for regenerating alkane dehydrogenation catalysts generally employ high-temperature carbonization processes above 450°C. This temperature condition fundamentally conflicts with the upper limit of the operating temperature of the heat transfer oil system in a cyclohexane low-temperature dehydrogenation unit (350°C), making in-situ regeneration impossible.

[0017] This invention provides a regeneration path of "softening first, then low-temperature combustion". First, a surface-active amine polymer solution is used as a cleaning agent. This polymer molecular chain contains both hydrophobic organic segments and at least one hydrophilic amino group. The hydrophobic segments can effectively penetrate and anchor into the stubborn carbon deposits with a graphite-like structure on the catalyst surface, while the hydrophilic amino group provides good dispersibility in an acetone-water mixed solvent. The synergistic effect of both allows the cleaning solution to significantly reduce surface tension, disrupt the strong adhesion between the carbon deposits and the catalyst active sites, and achieve softening, swelling, and initial peeling of the stubborn surface carbon deposits, creating conditions for subsequent low-temperature carbonization.

[0018] A secondary cleaning process using an aqueous solution of alkali metal chloride is then employed. On one hand, free chloride ions in the solution displace and remove residual amine polymers on the catalyst through common ion effects or ion exchange mechanisms (first-step cleaning). Simultaneously, chloride ions coordinate with platinum particles, preventing their agglomeration during charring. On the other hand, beneficial alkali metal ions (K⁺ or Na⁺) are simultaneously replenished to the catalyst surface, restoring their neutralizing effect on the acidity of the support and their electronic stabilizing effect on the platinum particles. This allows the present invention to eliminate the necessary chlorination activation step in traditional alkane dehydrogenation catalyst regeneration methods, simplifying the process and reducing safety risks.

[0019] Furthermore, a two-stage controlled oxygen charring process was completed at a temperature not exceeding 320℃. The first stage involved preliminary charring under low temperature and low oxygen concentration conditions, gently removing easily combustible carbon deposits softened by the polymer. The second stage involved increasing the temperature and oxygen concentration for deep charring to thoroughly remove residual carbon deposits. The maximum temperature throughout the entire charring process was controlled below 320℃, making it fully compatible with the existing low-temperature dehydrogenation unit's heat transfer oil system. This achieved true in-situ regeneration while avoiding the problem of precious metal active components agglomerating and sintering due to high-temperature treatment.

[0020] Finally, the hydrogen reduction step reduces the platinum species in the oxidized state after carbonization to the catalytically active metallic state Pt. 0 It should be noted that this reduction process can be efficiently completed under the low-temperature conditions of this invention, thanks to the preceding polymer cleaning and low-temperature carbonization steps which preserve the highly dispersed state of the platinum particles and the chemical forms of the tin and alkali metal additives. During the reduction process, the generated Pt... 0 The in-situ formation of a Pt-Sn alloy structure with adjacent tin species is crucial for the high selectivity of the cyclohexane dehydrogenation catalyst. The unique low-temperature regeneration process of this invention ensures the effective reconstruction of this alloy structure, avoiding alloy phase destruction caused by metal sintering in traditional high-temperature regeneration. Simultaneously, the hydrogen overflow effect under a reducing atmosphere helps remove trace amounts of residual oxygen from the surface of platinum particles, fully exposing the active sites. Alkali metal additives ( The catalyst remains stable under the low-temperature conditions of this invention, continuing to neutralize the acidity of the support and regulate the electronic state of platinum. It is precisely because the preceding steps create favorable conditions for reduction, coupled with the proper control of the reduction step itself, that the regenerated catalyst can restore its dehydrogenation activity (conversion rate >95%) and selectivity (>99.7%) close to that of the fresh catalyst, and its performance remains stable after multiple cycles.

[0021] The above steps work together: polymer softening lowers the temperature threshold required for carbonization; chloride cleaning and adhesion to the catalyst surface prevents platinum particle agglomeration during carbonization; two-stage oxygen control balances carbonization efficiency and operational safety; and the hydrogen reduction step reduces the oxidized platinum species (PtO / PtO2) after carbonization to catalytically active metallic Pt, promoting the reconstruction of the Pt-Sn alloy structure, thereby restoring the catalyst's dehydrogenation activity and selectivity. After five regeneration cycles, the catalyst using this method maintains a stable cyclohexane dehydrogenation conversion rate of over 95% and a selectivity of over 99.7%, essentially matching the performance of a fresh catalyst. In contrast, regeneration performance significantly decreases with increasing cycle number when using only single cleaning or traditional high-temperature carbonization.

[0022] Further, in step S100, the amine polymer is selected from polyetheramine or polyisobutyleneamine; the concentration of the amine polymer solution is 0.2wt%~1wt%.

[0023] This invention uses a polyetheramine solution / polyisobutyleneamine to clean the deactivated catalyst. The surface-active components contained in the polyetheramine / polyisobutyleneamine effectively adhere to and penetrate into the interior of the stubborn carbon deposits on the catalyst surface, destroying the adhesion between the carbon deposits and the active sites, thereby softening and initially peeling off the carbon deposits, and significantly reducing the temperature threshold required for subsequent carbon burning.

[0024] Further, in step S100, the solvent of the amine polymer solution is an acetone-water solution, and the volume ratio of acetone to water is 1:0.9~1.1.

[0025] While polyetheramine is readily soluble in organic solvents, its water solubility is poor. Using pure organic solvents (such as pure acetone) can ensure effective dissolution, but it poses significant safety hazards due to its flammability and explosiveness. Using only water, polyetheramine is difficult to dissolve fully and cannot achieve its softening effect. This invention innovatively uses a mixed solvent of acetone and water, ensuring both effective dissolution of polyetheramine and its ability to wet carbon deposits, while controlling the organic solvent concentration within a safe range, significantly reducing operational risks. This technical solution not only ensures the feasibility of low-temperature carbonization but also meets the safety requirements for industrial scale-up.

[0026] Further, in step S200, the alkali metal chloride is selected from potassium chloride or sodium chloride; the concentration of the aqueous solution of the alkali metal chloride is 0.1wt%~1wt%.

[0027] In this invention, the selection of alkali metal chlorides must simultaneously meet the following process requirements: effective removal of harmful chloride ions, supplementation of alkali metal additives, stability in the low-temperature carbonization range (≤320℃), and consideration of industrial economics.

[0028] The ionic radius of alkali metal cations directly affects their interaction with the alumina support. If the ionic radius is too small, it easily leads to lattice mismatch, generating impurity phases and significantly reducing activity; if the ionic radius is too large, it will disrupt the Pt-Sn-Al₂O₃ active interface and inhibit dehydrogenation reactions. Medium-radius K... + and Na + It has the best lattice matching with the carrier, which can effectively neutralize acidity and stabilize platinum particles.

[0029] Alkali metal chlorides must be able to displace amine polymers through common ion effects in the presence of residual amine polymers without inducing additional interfacial galvanic corrosion. Li + When the electrode potential is too low, uncontrollable electron transfer side reactions are prone to occur; Cs + The electrode potential is high, but the polarizability is too large, which easily changes the surface charge distribution. K + with Na + Being in the middle range ensures both chloride ion exchange efficiency and avoids interfering with the chemical state of the catalyst surface.

[0030] The carbonization temperature of this invention is controlled below 320℃, which requires that the selected alkali metal chlorides do not decompose or volatilize within this temperature range. KCl has a melting point of 770℃ and NaCl has a melting point of 801℃, both of which are much higher than the process temperature and fully meet the stability requirements; while LiCl, although having a higher melting point (605℃), is unsuitable for this process due to its strong hygroscopicity and potential side reaction risks.

[0031] In addition, potassium chloride and sodium chloride are readily available, inexpensive, non-toxic, and safe raw materials.

[0032] Furthermore, in steps S100 and S200, the cleaning temperature is 20~30℃ and the cleaning time is 2~4h.

[0033] Further, in step S300, drying is carried out for 2-4 hours under a nitrogen atmosphere at a temperature of 80-120°C.

[0034] Further, in step S400, the temperature is raised to 210~230℃, and an oxygen-containing atmosphere with an oxygen content of 8v%~10v% is introduced for preliminary charring for 2~4 hours; the temperature is raised to 310~320℃ for secondary charring, and the oxygen content is increased to 18v%~21v% for 18~24 hours.

[0035] This invention employs a two-stage oxygen-controlled charring strategy. In the first stage, preliminary charring is carried out at 220°C and low oxygen concentration (8v%~10v%) to gently remove the easily combustible carbon deposits after polymer softening. In the second stage, the temperature is raised to 310~320°C and the oxygen concentration is increased to 18v%~21v% for deep charring to thoroughly remove residual carbon deposits.

[0036] Furthermore, in step S400, the oxygen-containing atmosphere is a mixture of oxygen and nitrogen.

[0037] Furthermore, in step S500, the reduction temperature is 300~360℃ and the reduction time is 2~4h.

[0038] This temperature range aligns with the low-temperature carbonization process (≤320℃) of this invention, avoiding the re-agglomeration of platinum particles caused by traditional high-temperature reduction (>400℃), and effectively maintaining the highly dispersed state of the active metal. Simultaneously, the sufficient reduction time (2~4h) ensures that the oxidized platinum species on the catalyst surface are fully reduced to the catalytically active metallic state Pt. 0Under these conditions, the regenerated catalyst can restore dehydrogenation activity (conversion rate >95%) and selectivity (>99.7%) close to that of the fresh catalyst, and its performance remains stable after multiple regeneration cycles. Furthermore, these reduction conditions are compatible with the heat transfer oil heating system of industrial plants, requiring no additional equipment modifications and achieving true low-temperature in-situ regeneration.

[0039] Further, in step S500, the hydrogen atmosphere is a mixture of hydrogen and nitrogen, with a hydrogen concentration of 5wt% to 50wt%.

[0040] The preparation method of the cyclohexane dehydrogenation to benzene catalyst of the present invention includes the following steps:

[0041] Step 1: Preparation of alumina carrier: Boehmite, guar gum powder, nitric acid and water are mixed evenly, shaped, dried and calcined to obtain alumina carrier.

[0042] Step 2: Loading the active component: Prepare a Pt-containing solution and test the water absorption rate of the support. Take the alumina support obtained in Step 1, and according to the water absorption rate of the support, transfer the Pt-containing solution and deionized water to prepare an impregnation solution. Adjust the pH value of the impregnation solution with hydrochloric acid or sodium carbonate, and then add the impregnation solution to the support in multiple portions, shaking continuously until all the impregnation solution is adsorbed. After aging at room temperature, dry and calcinate to obtain the catalyst precursor.

[0043] Step 3, reduce the catalyst precursor: take the catalyst precursor obtained in step 2, heat and pressurize it, reduce it, then cool it down, purge it with nitrogen and unload it for later use.

[0044] Step 4: Loading the additive: Based on the additive content in the catalyst and the water absorption rate of the catalyst precursor, a quantitative amount of soluble salt containing the additive is weighed and dissolved in a quantitative amount of deionized water to prepare an impregnation solution containing the additive. The pH value of the impregnation solution is adjusted with hydrochloric acid or sodium carbonate. Then, the impregnation solution is added to the reduced catalyst precursor in multiple portions, shaking continuously until the impregnation solution is completely adsorbed. After aging at room temperature, drying, and calcination, the catalyst is obtained. The active components of the catalyst are distributed in a shell-like pattern on the support. The catalyst composition is Pt-Sn-K-Ce.

[0045] Compared with the prior art, the beneficial effects of the present invention are:

[0046] 1. This invention maintains a processing temperature below 320℃ throughout the entire process, making it perfectly compatible with the heat transfer oil system of a cyclohexane low-temperature dehydrogenation industrial unit. In-situ regeneration can be achieved without disassembling the catalyst, effectively solving the problem of traditional high-temperature regeneration being unable to operate online. Furthermore, the use of low-temperature carbonization instead of the traditional high-temperature treatment above 450℃, combined with the removal of harmful chloride ions using alkali metal chlorides, significantly inhibits the migration and sintering of platinum particles, ensuring that the active metal remains highly dispersed even after multiple regenerations.

[0047] 2. This invention utilizes the synergistic effect of polyetheramine or polyisobutyleneamine softening of carbon deposits and secondary cleaning with alkali metal chlorides to complete dechlorination, replenishment, and carbon removal in a single step. This eliminates the need for a separate chlorination activation step required in traditional regeneration methods, simplifying the process and reducing operational safety risks. After five regeneration cycles, the regenerated catalyst maintains a stable conversion rate of over 95% for cyclohexane dehydrogenation, close to the 96.0% of the fresh catalyst, with selectivity remaining above 99.7%, far superior to comparative methods using only single cleaning or traditional high-temperature carbonization.

[0048] 3. This invention uses an acetone-water mixed solvent, which avoids the flammability and explosion risks of pure organic solvents; it selects readily available, inexpensive, and non-toxic raw materials such as potassium chloride and sodium chloride, which are far cheaper than lithium salts or cesium salts, combining safety, environmental protection, and industrial economy, making it suitable for large-scale promotion and application. Attached Figure Description

[0049] Figure 1 The in-situ regeneration catalyst prepared in Example 2 of this invention;

[0050] Figure 2 It is a catalyst used in the dehydrogenation of cyclohexane to benzene process. Detailed Implementation

[0051] The present invention will now be further described.

[0052] Example 1

[0053] A method for preparing a catalyst for the dehydrogenation of cyclohexane to benzene includes the following steps:

[0054] Step 1: Preparation of alumina carrier: Take 300g of boehmite, 15g of guar gum powder, 10g of nitric acid and 280g of water, mix them evenly and shape them, dry them at 120℃ for 8 hours, and calcine them at 750℃ for 6 hours to obtain the alumina carrier.

[0055] Step 2, Loading the active component: Prepare a Pt-containing solution with a Pt content of 2%, and test the water absorption rate of the support (90%). Take 50g of the alumina support obtained in Step 1, and according to the water absorption rate of the support, transfer the Pt-containing solution and deionized water to prepare an impregnation solution. Adjust the pH of the impregnation solution to 1.52 with hydrochloric acid or sodium carbonate, and then add the impregnation solution to the support in 10 portions, shaking while adding, until the impregnation solution is completely adsorbed. After aging at room temperature for 3 hours, dry at 150℃ for 10 hours, and calcine at 400℃ for 4 hours to obtain the catalyst precursor.

[0056] Step 3, reduce the catalyst precursor: Take 40g of the catalyst precursor obtained in step 2, reduce it for 4 hours at 350℃, 200KPa hydrogen pressure, and a hydrogen to catalyst precursor volume ratio of 300, then reduce it to 30℃, purge with nitrogen for 4 hours and unload it for later use.

[0057] Step 4: Loading the additive: Based on the additive content in the catalyst and the water absorption rate of the catalyst precursor, a quantitative amount of soluble salt containing the additive is weighed and dissolved in a quantitative amount of deionized water to prepare an impregnation solution containing the additive. The pH of the impregnation solution is adjusted to 1.85 with hydrochloric acid or sodium carbonate. Then, the impregnation solution is added to the reduced catalyst precursor in 10 portions, shaking continuously until the impregnation solution is completely adsorbed. After aging at room temperature for 3 hours, it is dried at 150℃ for 10 hours and calcined at 400℃ for 4 hours to obtain the catalyst. The active components of the catalyst are distributed in a shell-like pattern on the support. The catalyst composition is 0.45%Pt-0.20%Sn-0.15%K-0.15%Ce.

[0058] Example 2

[0059] Take 10g of the fresh catalyst from Example 1 and age it under the following conditions: reaction pressure 10 kPa, reaction temperature 400°C, and cyclohexane liquid hourly space velocity 2.0 h⁻¹. -1 After the reaction has proceeded for a period of time, when the conversion rate drops from 99.9% to 95%, nitrogen gas is used to purge and lower the temperature to 320°C. o C, airspeed adjusted to 0.5h -1 At this point, the conversion rate drops to 80%, the selectivity is 99.9%, and the catalyst aging step is complete.

[0060] An in-situ regeneration method for catalysts used in the dehydrogenation of cyclohexane to benzene includes the following steps:

[0061] S100. After the aging test, nitrogen gas was used to purge and cool the room to room temperature. Then, a 1.0 wt% polyetheramine solution was injected, with acetone-water solution as the solvent. The volume ratio of acetone to water was 1:1, and the space velocity was 1 h⁻¹. -1 Clean for 4 hours.

[0062] S200, inject a 1.0 wt% sodium chloride aqueous solution, with a space velocity of 1 h⁻¹. -1 Clean for 4 hours.

[0063] Under S300 and nitrogen atmosphere, the temperature is raised to 120°C. o C, keep at a constant temperature for 2 hours to dry.

[0064] S400, continue heating to 220℃, introduce an oxygen-containing atmosphere with an oxygen content of 8v% for preliminary charring for 2 hours, then raise the temperature to 310℃ for secondary charring, increasing the oxygen content to 18v% for 18 hours.

[0065] S500, at a hydrogen flow rate of 50 ml / min, 300 o Reduction for 4 hours under reaction conditions C yields the first-generation product of the in-situ regenerated catalyst, as shown in the product description. Figure 1As shown. After aging the first-cycled product again using the method described above, the in-situ regeneration method is repeated twice to obtain the second-cycled product. The same method is used to obtain the third-cycled product, the fourth-cycled product, and the fifth-cycled product.

[0066] Example 3

[0067] Take 10g of the fresh catalyst from Example 1 and age it according to the method of Example 2.

[0068] An in-situ regeneration method for catalysts used in the dehydrogenation of cyclohexane to benzene includes the following steps:

[0069] After the S100 aging test, the mixture was purged with nitrogen and cooled to room temperature. A 0.2 wt% polyetheramine solution was then injected, with an acetone-water aqueous solution as the solvent (acetone to water volume ratio 1:1) and a space velocity of 1 h⁻¹. -1 Clean for 4 hours.

[0070] S200, inject a 0.2wt% potassium chloride aqueous solution, with a space velocity of 1 h⁻¹. -1 Clean for 4 hours.

[0071] Under S300 and nitrogen atmosphere, the temperature is raised to 120°C. o C, keep at a constant temperature for 2 hours.

[0072] S400, continue heating to 220℃, introduce an oxygen-containing atmosphere with an oxygen content of 10v% for preliminary charring for 4 hours, then raise the temperature to 320℃ for further charring, increase the oxygen content to 21v%, and continue for 24 hours.

[0073] S500, at a hydrogen flow rate of 50 ml / min, 300 o Reduction was performed for 4 hours under reaction conditions C. The first-regenerated catalyst product was obtained. The first-regenerated product was then aged again according to the method in Example 2, and the in-situ regeneration method was repeated twice to obtain the second-regenerated product. The same method was used to obtain the third-regenerated product, the fourth-regenerated product, and the fifth-regenerated product.

[0074] Example 4

[0075] Take 10g of the fresh catalyst from Example 1 and age it according to the method of Example 2.

[0076] An in-situ regeneration method for catalysts used in the dehydrogenation of cyclohexane to benzene includes the following steps:

[0077] After the S100 aging test, the mixture was purged with nitrogen and cooled to room temperature. A 0.6 wt% polyetheramine solution was then injected, with an acetone-water aqueous solution as the solvent. The volume ratio of acetone to water was 1:1.1, and the space velocity was 1 h⁻¹. -1 Cleaning time: 3.5 hours.

[0078] S200, inject a 0.6wt% potassium chloride aqueous solution, with a space velocity of 1 h⁻¹. -1 Clean for 3 hours.

[0079] Under S300 nitrogen atmosphere, the temperature is raised to 100°C. o C, keep at a constant temperature for 3 hours to dry.

[0080] S400, continue heating to 220℃, introduce an oxygen-containing atmosphere with an oxygen content of 9v% for preliminary charring for 3.2 hours, then raise the temperature to 315℃ for further charring, increase the oxygen content to 21v%, and continue for 21 hours.

[0081] S500, at a hydrogen flow rate of 50 ml / min, 300 o Reduction was performed for 3 hours under reaction conditions C. The first-regenerated catalyst product was obtained. The first-regenerated product was then aged again according to the method in Example 2, and the in-situ regeneration method was repeated twice to obtain the second-regenerated product. The same method was used to obtain the third-regenerated product, the fourth-regenerated product, and the fifth-regenerated product.

[0082] Example 5

[0083] Take 10g of the fresh catalyst from Example 1 and age it according to the method of Example 2.

[0084] An in-situ regeneration method for catalysts used in the dehydrogenation of cyclohexane to benzene includes the following steps:

[0085] After the S100 aging test, the mixture was purged with nitrogen and cooled to room temperature. A 0.5 wt% polyisobutylene amine solution was then injected, with acetone-water solution as the solvent. The volume ratio of acetone to water was 1:0.9, and the space velocity was 1 h⁻¹. -1 Cleaning time: 3.5 hours.

[0086] S200, inject a 0.1 wt% sodium chloride aqueous solution, with a space velocity of 1 h⁻¹. -1 Clean for 3 hours.

[0087] Under S300 and nitrogen atmosphere, the temperature is raised to 80°C. o C, keep at a constant temperature for 4 hours to dry.

[0088] S400, continue heating to 230℃, introduce an oxygen-containing atmosphere with an oxygen content of 10v% for preliminary charring for 3.2 hours, then raise the temperature to 315℃ for further charring, increase the oxygen content to 20v%, and continue for 22 hours.

[0089] S500, at a hydrogen flow rate of 50 ml / min, 300 oReduction was performed for 2 hours under reaction conditions C. The first-regenerated catalyst product was obtained. The first-regenerated product was then aged again according to the method in Example 2, and the in-situ regeneration method was repeated twice to obtain the second-regenerated product. The same method was used to obtain the third-regenerated product, the fourth-regenerated product, and the fifth-regenerated product sequentially.

[0090] Comparative Example 1

[0091] Take 10g of the fresh catalyst from Example 1 and age it according to the method of Example 2.

[0092] An in-situ regeneration method for catalysts used in the dehydrogenation of cyclohexane to benzene includes the following steps:

[0093] The catalyst aging process is complete; maintain a constant temperature of 320°C. o C. Air is introduced at a flow rate of 30 mL / min for charring treatment. After charring for 18 hours, hydrogen is introduced at a flow rate of 50 mL / min and 300 mL / min. o Reduction was performed for 4 hours under reaction conditions C. The first-regenerated catalyst product was obtained. The first-regenerated product was then aged again according to the method in Example 2, and the in-situ regeneration method was repeated twice to obtain the second-regenerated product. The same method was used to obtain the third-regenerated product.

[0094] Comparative Example 2

[0095] Take 10g of the fresh catalyst from Example 1 and age it according to the method of Example 2.

[0096] An in-situ regeneration method for catalysts used in the dehydrogenation of cyclohexane to benzene includes the following steps:

[0097] After the aging test, the room temperature was lowered to room temperature by nitrogen purging, and then a 0.1 wt% potassium chloride aqueous solution was injected at a space velocity of 1 h⁻¹. -1 Cleaning for 4 hours. Under a nitrogen atmosphere, heat to 120°C. o C, maintain constant temperature for 4 hours. Switch from air to nitrogen and raise the temperature to 320°C. o C. Perform charcoal burning treatment. After charcoal burning for 18 hours, use hydrogen at a flow rate of 50 ml / min and a temperature of 300... o Reduction was performed for 4 hours under reaction conditions C. The first-regenerated catalyst product was obtained. The first-regenerated product was then aged again according to the method in Example 2, and the in-situ regeneration method was repeated twice to obtain the second-regenerated product. The same method was used to obtain the third-regenerated product.

[0098] Comparative Example 3

[0099] Take 10g of the fresh catalyst from Example 1 and age it according to the method of Example 2.

[0100] An in-situ regeneration method for catalysts used in the dehydrogenation of cyclohexane to benzene includes the following steps:

[0101] After the aging test, the mixture was purged with nitrogen and cooled to room temperature. Then, a 0.2 wt% polyetheramine solution (acetone aqueous solution) was injected at a space velocity of 1 h⁻¹. -1 Clean for 2 hours. Heat to 120°C under a nitrogen atmosphere. o C, maintain constant temperature for 2 hours. Switch from air to nitrogen and raise the temperature to 320°C. o C. Perform charcoal burning treatment. After charcoal burning for 18 hours, use hydrogen at a flow rate of 50 ml / min and a temperature of 300... o Reduction was performed for 4 hours under reaction conditions C. The first-regenerated catalyst product was obtained. The first-regenerated product was then aged again according to the method in Example 2, and the in-situ regeneration method was repeated twice to obtain the second-regenerated product. The same method was used to obtain the third-regenerated product.

[0102] The catalyst products regenerated in situ using the methods of Examples 1-5 and Comparative Examples 1-3 were used for performance evaluation. The catalyst regeneration and performance evaluation were repeated 5 times, and the average value was taken. The performance evaluation conditions of the regenerated catalyst were the same as those of the fresh catalyst. The results are shown in Table 1.

[0103] Catalyst performance evaluation: 10 grams of catalyst were weighed and placed in a stainless steel reaction tube with an inner diameter of 12 mm and a length of 550 mm. In the simulated isothermal tubular reactor, the reaction temperature was controlled by the heat transfer oil in the jacket. In the model adiabatic reactor, the reaction temperature was controlled by an electric heating furnace. Before performance testing, the catalyst was reduced for 4 hours at 300°C with a hydrogen flow rate of 50 ml / min. After adjusting to the reaction temperature, cyclohexane was pumped in to initiate the reaction.

[0104] Reaction conditions: reaction pressure 10 kPa, reaction temperature 300 °C, cyclohexane liquid hourly space velocity 0.5 h⁻¹ -1 The dilution gas was controlled by a mass flow meter. After the reaction stabilized, liquid products were taken from the bottom of the separator every 8 hours for analysis. The composition of the liquid products was analyzed by an Agilent 7890 gas chromatograph (HP-Al2O3 / KCl capillary column, FID detector).

[0105] Performance evaluation results of catalysts regenerated in situ using the methods in Examples 1-5 and Comparative Examples 1-3

[0106]

[0107] As shown in Table 1, the original catalytic capacity of the catalyst prepared in Example 1 was 96.0% conversion and 99.8% selectivity. In Examples 2-5, after five regenerations, the conversion and selectivity of the aged catalysts participating in the catalytic reaction fluctuated due to normal systematic errors, but the conversion remained above 95% and the selectivity was above 99.7%.

[0108] In Comparative Example 1, using the traditional regeneration method, the conversion rate of the catalyst reaction was only 92% after one regeneration. After two and three regenerations, the conversion rate dropped sharply. After three regenerations, the conversion rate was only 82%, which was much lower than that of Example 2.

[0109] In Comparative Example 2, the aged catalyst was first cleaned with a potassium chloride aqueous solution, and then a conventional regeneration method was used. The conversion rate of the catalyst reaction was increased to 95%. After two and three regenerations, the conversion rate decreased slightly. This indicates that the potassium chloride cleaning method of the present invention can effectively improve the conversion rate of the regenerated catalyst and maintain the stability of the conversion performance after catalyst regeneration.

[0110] In Comparative Example 3, the aged catalyst was first cleaned with a polyetheramine solution, and then a conventional regeneration method was used. The conversion rate of the catalyst reaction was increased to 95.3%. After two and three regenerations, the conversion rate decreased slightly. This indicates that the polyetheramine solution cleaning method of the present invention can effectively improve the conversion rate of the regenerated catalyst and maintain the stability of the conversion performance after catalyst regeneration. Furthermore, the conversion rate of Comparative Example 3 is slightly higher than that of Comparative Example 2.

[0111] The high selectivity values ​​of Comparative Examples 1-3 actually indicate poor activity: as the conversion rate decreases, side reactions are suppressed, naturally increasing the selectivity. In contrast, Examples 2-5 maintain a selectivity of over 99.7% while maintaining a high conversion rate, demonstrating that the regenerated catalyst of this invention has a conversion rate and selectivity comparable to that of the fresh catalyst.

Claims

1. A method for in-situ regeneration of a catalyst for the dehydrogenation of cyclohexane to benzene, characterized in that, Includes the following steps: S100. Clean the deactivated catalyst on the device using a surface-active amine polymer solution; S200. The deactivated catalyst on the device is cleaned again using an alkali metal chloride aqueous solution. The cleaned catalyst was dried under an inert atmosphere at S300. Under an oxygen-containing atmosphere (S400), the catalyst is initially carbonized by heating. Continue to increase the temperature and oxygen content to carry out a second charcoal burning process; Under S500 and hydrogen atmosphere, the decarbonized catalyst is reduced; The amine polymer molecular chain contains both a hydrophobic organic segment and at least one hydrophilic amino group.

2. The in-situ regeneration method for the catalyst in the dehydrogenation of cyclohexane to benzene according to claim 1, characterized in that, In step S100, the amine polymer is selected from polyetheramine or polyisobutyleneamine; the concentration of the amine polymer solution is 0.2~1wt%.

3. The in-situ regeneration method for the catalyst in the dehydrogenation of cyclohexane to benzene according to claim 1, characterized in that, In step S100, the solvent of the amine polymer solution is an acetone-water solution, and the volume ratio of acetone to water is 1:0.9~1.

1.

4. The in-situ regeneration method for the catalyst in the dehydrogenation of cyclohexane to benzene according to claim 1, characterized in that, In step S200, the alkali metal chloride is selected from potassium chloride or sodium chloride; the concentration of the aqueous solution of the alkali metal chloride is 0.1~1wt%.

5. The in-situ regeneration method for the catalyst in the dehydrogenation of cyclohexane to benzene according to claim 1, characterized in that, In steps S100 and S200, the cleaning temperature is 20~30℃ and the cleaning time is 2~4h.

6. The in-situ regeneration method for the catalyst in the dehydrogenation of cyclohexane to benzene according to claim 1, characterized in that, In step S300, drying is carried out for 2-4 hours under a nitrogen atmosphere at a temperature of 80-120°C.

7. The in-situ regeneration method for the catalyst in the dehydrogenation of cyclohexane to benzene according to claim 1, characterized in that, In step S400, the temperature is raised to 210~230℃, and an oxygen-containing atmosphere with an oxygen content of 8v%~10v% is introduced for preliminary charring for 2~4 hours; the temperature is then raised to 310~320℃ for secondary charring, and the oxygen content is increased to 18~21v% for 18~24 hours.

8. The in-situ regeneration method for the catalyst in the dehydrogenation of cyclohexane to benzene according to claim 1, characterized in that, In step S400, the oxygen-containing atmosphere is a mixture of oxygen and nitrogen.

9. The in-situ regeneration method for the catalyst in the dehydrogenation of cyclohexane to benzene according to claim 1, characterized in that, In step S500, the reduction temperature is 300~360℃ and the reduction time is 2~4h.

10. The in-situ regeneration method for the catalyst in the dehydrogenation of cyclohexane to benzene according to claim 1, characterized in that, In step S500, the hydrogen atmosphere is a mixture of hydrogen and nitrogen, with a hydrogen concentration of 5-50 wt%.

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