Method for improving in-situ regeneration efficiency of titanium-silicon molecular sieve

Abstract

The present application relates to a kind of methods for improving the efficiency of titanium-silicon molecular sieve in-situ regeneration, belong to the field of catalyst regeneration technology.The method includes the following steps: first, the reactor containing deactivated titanium-silicon molecular sieve is heated to a certain temperature, while in normal pressure state, the reactor is purged with nitrogen, then water is blown into the reactor in the form of microdroplets with ozone-containing gas for a certain time, under the combined action of microdroplet electric field and ozone, the accumulated carbon on the surface and internal pores of the molecular sieve can be efficiently oxidized, after cooling, finally, the microdroplets containing ozone are blown clean with nitrogen, and the in-situ regeneration is completed.The method utilizes the combined action of microdroplet electric field generated by water microdroplets and ozone, in low temperature and normal pressure state, accumulated carbon in deactivated titanium-silicon molecular sieve can be eliminated in a short time, after regeneration, the activity of titanium-silicon molecular sieve is the same as that of fresh titanium-silicon molecular sieve, and the service life can reach more than 95% of that of fresh catalyst.

Description

Technical Field

[0001] This invention relates to the field of catalyst regeneration technology, and more particularly to the field of regeneration technology for deactivated titanium-silicon molecular sieve catalysts after propylene epoxidation, chloropropylene epoxidation, phenol hydroxylation reaction, or toluene hydroxylation reaction. Specifically, it relates to a method for improving the in-situ regeneration efficiency of deactivated titanium-silicon molecular sieves. Background Technology

[0002] The main reason for the deactivation of titanium-silicon molecular sieves is the small pore size of the catalyst, which restricts the diffusion of reactants and products. Products, unable to diffuse sufficiently, produce large-molecule byproducts, which accumulate to a certain level, eventually leading to catalyst deactivation. Since the pores are now completely blocked, ordinary solvents are insufficient to clean the carbon deposits, making in-situ solvent regeneration extremely difficult. Removing the catalyst, calcining it, and then reloading it is not only time-consuming and labor-intensive but also significantly increases costs and greatly limits production efficiency.

[0003] CN102941117A uses oxygen-containing gas for in-situ regeneration at temperatures as high as 200-800℃, which is difficult to achieve in a fixed-bed reactor. This is essentially equivalent to in-situ roasting, which is highly dangerous, as there is a significant risk of combustion of organic matter.

[0004] CN112675907A involves sequentially treating the catalyst with solvent, urea peroxide solution, and an aqueous ionic liquid solution, followed by a final solvent treatment to achieve in-situ regeneration of the deactivated catalyst. At a pressure of 0.5-2.0 MPa and a temperature of 60-100℃, the catalyst requires initial solvent washing to remove easily washable substances, followed by oxidation of most residual organic matter with urea peroxide solution, then further treatment with an aqueous ionic liquid solution, and finally, solvent washing. This method has extremely stringent requirements for each cleaning step, necessitating large amounts of solvent for rinsing, resulting in waste.

[0005] CN114308118A: The washing solution is fed into a reaction apparatus containing deactivated titanium-silicon molecular sieves for a first-stage reaction. An acidic solution is then fed into the same apparatus for a second-stage reaction. Finally, an alkaline titanium-containing solution is fed into the apparatus for a third-stage reaction, yielding regenerated titanium-silicon molecular sieves. This process also requires extensive solvent rinsing.

[0006] The above-mentioned in-situ regeneration methods either require high-temperature processing, which demands sophisticated equipment and poses safety hazards, or they involve in-situ regeneration using an oxidation solution, both of which require switching between different solutions for rinsing, necessitating large amounts of solvent to ensure thorough rinsing and wasting raw materials. Summary of the Invention

[0007] To address the above technical problems, this invention provides an in-situ regeneration method for deactivated titanium-silicon molecular sieves. The method involves first heating a reactor containing the deactivated titanium-silicon molecular sieve to a certain temperature, while simultaneously purging the reactor with nitrogen gas at atmospheric pressure. Then, water containing ozone gas is blown into the reactor in the form of microdroplets for a certain reaction time. Under the combined action of the microdroplet electric field and ozone, carbon deposits on the surface and within the internal pores of the molecular sieve are efficiently oxidized. After cooling, the ozone-containing microdroplets are finally purged with nitrogen gas to remove them, thus completing the in-situ regeneration. This method only requires switching nitrogen gas for purging, is simple, low-cost, highly efficient, and maintains unchanged catalyst activity, with a lifespan exceeding 95% of that of a fresh catalyst.

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

[0009] A method for improving the in-situ regeneration efficiency of titanium-silicon molecular sieves utilizes the combined effect of microdroplet electric field and ozone to enhance the in-situ regeneration efficiency of deactivated titanium-silicon molecular sieves. The method specifically includes the following steps:

[0010] Step (1) First, heat the reactor containing the deactivated titanium silicon molecular sieve. At the same time, nitrogen gas is introduced into the reactor under normal pressure to dry the reaction liquid on the surface and inside of the deactivated titanium silicon molecular sieve.

[0011] After nitrogen purging in step (2), the reactor temperature is changed, and ozone-containing gas is used to blow water into the reactor in the form of micro-droplets for a certain period of time. The combined effect of the micro-droplet electric field generated by the water micro-droplets and ozone is used to oxidize and eliminate carbon deposits on the surface and inside the pores of the molecular sieve.

[0012] Step (3) Lower the reactor temperature and purge the ozone-containing microdroplets in the reactor with nitrogen to obtain in-situ regenerated titanium-silicon molecular sieve.

[0013] Furthermore, the deactivated titanium-silicon molecular sieve is suitable for titanium-silicon molecular sieves that have been deactivated after chloropropylene epoxidation, propylene epoxidation, phenol hydroxylation, or toluene hydroxylation.

[0014] Furthermore, the deactivated titanium-silicon molecular sieve is a deactivated TS-1 type titanium-silicon molecular sieve, a Ti-MWW type titanium-silicon molecular sieve, or a deactivated Ti-MOR type titanium-silicon molecular sieve.

[0015] Furthermore, before proceeding to step (1), the reaction liquid inside the reactor is emptied in advance.

[0016] Furthermore, in step (1), the reactor temperature is 30-120℃, the heating rate is 0.2-5℃ / min, and the nitrogen space velocity is 0.1-5min. -1 The purging time is 1-24 hours.

[0017] Furthermore, in step (1), the reactor temperature is 60-90℃, the heating rate is 1-3℃ / min, and the nitrogen space velocity is 1-3min. -1 The purging time is 2-9 hours.

[0018] Furthermore, in step (2), the carrier containing ozone gas is nitrogen, oxygen, argon, helium, or any combination of these gases.

[0019] Furthermore, in step (2), the reactor temperature is 30-120℃, the ozone concentration is 20-120 mg / L, and the ozone gas space velocity is 0.1-5 min. -1 The ozone-containing gas is introduced over a period of 3-18 hours.

[0020] Furthermore, in step (2), the reactor temperature is 30-60℃, the ozone concentration is 40-80 mg / L, and the ozone gas space velocity is 1-3 min. -1 The ozone-containing gas is introduced over a period of 6-12 hours.

[0021] Furthermore, in step (2), the microdroplet size is 1-20 μm, and the microdroplet space velocity is 0.5-5 h⁻¹. -1 .

[0022] Furthermore, in step (2), the microdroplet size is 2-10 μm, and the microdroplet space velocity is 1-3 h⁻¹. -1 .

[0023] Furthermore, in step (3), the nitrogen space velocity is 0.5-5 min. -1 Purging time is 3-24 hours.

[0024] Furthermore, in step (3), the nitrogen space velocity is 1-3 min. -1 The purging time is 12-18 hours.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] This invention utilizes ozone-containing gas to blow water into a fixed-bed reactor in the form of microdroplets for a certain reaction time. Under the combined action of the microdroplet electric field and ozone, carbon deposits on the surface and within the internal pores of the molecular sieve can be efficiently oxidized. It can regenerate various deactivated titanium-silicon molecular sieves, significantly improving the in-situ regeneration efficiency. The method, performed at ambient pressure and low temperature, is safe and efficient, restoring deactivated titanium-silicon molecular sieves to over 95% of their previous lifespan without damaging the catalyst structure, allowing for cyclic regeneration and greatly extending the catalyst's lifespan. Detailed Implementation

[0027] The regeneration method of the present invention will be further described in detail below through comparative examples and embodiments.

[0028] An example was conducted using a continuous epoxidation reaction of allyl chloride, with TS-1 titanium silicate molecular sieve as the catalyst. The evaluation method is as follows:

[0029] TS-1 titanium-silicon molecular sieves were packed into a reactor, and then 50% hydrogen peroxide, allyl chloride, and methanol were added at a hydrogen peroxide:allyl chloride:methanol molar ratio of 1:1.5:7, with a total liquid hourly space velocity of 1 h⁻¹. -1 The catalyst was introduced into the TS-1 titanium-silicon molecular sieve catalyst bed from the bottom of the reactor. The catalyst bed temperature was controlled at 35℃ using a water bath, and the reaction pressure was 0.1 MPa. Samples were taken online every 12 hours. The hydrogen peroxide conversion was determined by titration using the cerium sulfate method, and the epichlorohydrin yield and selectivity were analyzed by gas chromatography. The catalyst was considered deactivated when the hydrogen peroxide conversion was below 95% for three consecutive cycles. The catalyst's lifespan was calculated based on the first instance of a hydrogen peroxide conversion below 95%. Finally, the average hydrogen peroxide conversion and average epichlorohydrin selectivity were calculated.

[0030] The main performance evaluation indicators for the continuous epoxidation reaction of chloropropene are the conversion rate of H2O2 (X), the selectivity of epichlorohydrin (S), and the service life of the catalyst.

[0031] X(H2O2)=n0(H2O2)-n(H2O2) / n0(H2O2)*100%

[0032] S(ECH)=n(ECH) / n0(H2O2)*100%

[0033] In the formula, n0(H2O2) represents the number of moles of hydrogen peroxide entering the reactor during the sampling time, n(H2O2) represents the number of moles of hydrogen peroxide remaining in the sample, and N(ECH) represents the number of moles of epichlorohydrin in the sample.

[0034] Comparative Example 1

[0035] 100g of fresh TS-1 titanium-silicon molecular sieve was packed into the reactor, and the reaction solution was introduced. The experiment was conducted according to the above method to evaluate the lifespan of the fresh catalyst.

[0036] Comparative Example 2

[0037] 100g of the same batch of deactivated TS-1 titanium-silicon molecular sieve as in Comparative Example 1 was packed into the reactor. The deactivated catalyst was first purged with nitrogen at 80°C for 6 hours at a nitrogen space velocity of 1.5 min⁻¹. -1 Then, the reactor was kept at 80°C, and ozone-containing nitrogen gas was introduced for 24 hours, with an ozone concentration of 80 mg / L and an ozone-containing nitrogen gas space velocity of 1 min. -1 After treatment, the reactor was stopped from being kept at 80°C, and simultaneously switched to nitrogen gas for purging containing ozone, with a nitrogen space velocity of 1 min.-1 The purging time was 6 hours. After purging, the lifetime of the regenerated catalyst was evaluated according to the above experimental method.

[0038] Comparative Example 3

[0039] 100g of the same batch of deactivated TS-1 titanium-silicon molecular sieve as in Comparative Example 1 was packed into the reactor. The deactivated catalyst was first purged with nitrogen at 80°C for 6 hours at a nitrogen space velocity of 1.5 min⁻¹. -1 Then, keeping the reactor at 80°C, nitrogen gas was used to blow water into the reactor in the form of microdroplets at a nitrogen space velocity of 1 min. -1 The average droplet size is 5-10 μm, and the droplet space velocity is 2 h⁻¹. -1 The treatment time was 24 hours. After treatment, the reactor was stopped at 80°C and simultaneously switched to nitrogen gas to purge residual microdroplets, with a nitrogen space velocity of 1 min. -1 The purging time was 6 hours. After purging, the lifetime of the regenerated catalyst was evaluated according to the above experimental method.

[0040] Example 1

[0041] 100g of the same batch of deactivated TS-1 titanium-silicon molecular sieve as in Comparative Example 1 was packed into the reactor. The deactivated catalyst was first purged with nitrogen at 80°C for 6 hours at a nitrogen space velocity of 1.5 min⁻¹. -1 Then, keeping the reactor at 80°C, the filtered water was blown into the reactor in the form of microdroplets using ozone-containing nitrogen gas. The ozone concentration was 60 mg / L, and the ozone-containing nitrogen gas space velocity was 1 min. -1 The microdroplet size is 5-10 μm, and the microdroplet space velocity is 2 h⁻¹. -1 The treatment time was 12 hours. After treatment, the reactor was stopped and kept at 80°C. At the same time, nitrogen gas was switched on to purge residual microdroplets, with a nitrogen space velocity of 1 min. -1 The purging time was 6 hours. After purging, the lifetime of the regenerated catalyst was evaluated according to the above experimental method.

[0042] Example 2

[0043] The ozone-containing nitrogen gas was replaced with ozone-containing oxygen gas, and the other conditions were the same as in Example 1.

[0044] Example 3

[0045] 100g of the same batch of deactivated TS-1 titanium-silicon molecular sieve as in Comparative Example 1 was packed into the reactor. The catalyst was first deactivated by nitrogen purging at 30°C for 6 hours at a nitrogen space velocity of 1.5 min⁻¹. -1Then, keeping the reactor at a constant temperature of 30°C, water was blown into the reactor in the form of microdroplets using ozone-containing nitrogen gas. The ozone concentration was 120 mg / L, and the ozone-containing nitrogen gas space velocity was 0.5 min. -1 The microdroplet size is 1-5 μm, and the microdroplet space velocity is 2 h⁻¹. -1 The treatment time was 12 hours. After treatment, the reactor was stopped at 30°C and simultaneously switched to nitrogen gas to purge residual microdroplets, with a nitrogen space velocity of 1 min. -1 The purging time was 12 hours. After purging, the lifetime of the regenerated catalyst was evaluated according to the above experimental method.

[0046] Example 4

[0047] 100g of the same batch of deactivated TS-1 titanium-silicon molecular sieve as in Comparative Example 1 was packed into the reactor. The catalyst was first deactivated by nitrogen purging at 120℃ for 6 hours at a nitrogen space velocity of 1.5 min⁻¹. -1 Then, keeping the reactor at 120°C, water was blown into the reactor in the form of microdroplets using ozone-containing nitrogen gas. The ozone concentration was 20 mg / L, and the ozone-containing nitrogen gas space velocity was 3 min. -1 The microdroplet size is 4-6 μm, and the microdroplet space velocity is 1.5 h⁻¹. -1 The treatment time was 15 hours. After treatment, the fixed bed was stopped at 120°C, and nitrogen gas was switched on to purge residual microdroplets at a nitrogen space velocity of 1 minute. -1 The purging time was 15 hours. After purging, the lifetime of the regenerated catalyst was evaluated according to the above experimental method.

[0048] Example 5

[0049] The TS-1 titanium-silicon molecular sieve, which had been deactivated in the reaction evaluation of Example 1, was regenerated in situ. First, after the reaction was stopped, the reaction liquid in the reactor was emptied. Then, the reactor was heated to 90°C, and nitrogen gas was simultaneously introduced to purge the deactivated catalyst for 9 hours at a nitrogen space velocity of 1 min. -1 Then, keeping the reactor at 90°C, water was blown into the reactor in the form of microdroplets using ozone-containing nitrogen gas. The ozone concentration was 80 mg / L, and the ozone-containing nitrogen gas space velocity was 1 min. -1 The microdroplet size is 4-6 μm, and the microdroplet space velocity is 2 h⁻¹. -1 The treatment time was 12 hours. After treatment, the reactor was stopped from being kept at 90°C, and nitrogen gas was switched on to purge residual microdroplets at a nitrogen space velocity of 1 min. -1 The purging time was 6 hours. After purging, the lifetime of the regenerated catalyst was evaluated according to the above experimental method.

[0050] Table 1 Evaluation Results of Comparative and Example Tables for the Continuous Reaction of Allyl Chloride Epoxidation

[0051]

[0052] An example was conducted using a continuous propylene epoxidation reaction, with Ti-MWW type titanium-silicon molecular sieve as the catalyst. The evaluation method is as follows:

[0053] Ti-MWW titanium-silicon molecular sieves were packed into the reactor. Then, 50% hydrogen peroxide, propylene, and methanol were added at a hydrogen peroxide:propylene:methanol molar ratio of 1:2.2:5, with a total liquid hourly space velocity (LHSV) of 1 h⁻¹. -1 The catalyst bed of Ti-MWW titanium-silicon molecular sieve was introduced from the bottom of the reactor. The temperature of the catalyst bed was controlled at 40℃ using a water bath, and the reaction pressure was 2.2 MPa. Samples were taken online every 12 hours. The hydrogen peroxide conversion was determined by cerium sulfate titration, and the yield and selectivity of propylene oxide were analyzed by gas chromatography. The catalyst was considered deactivated when the hydrogen peroxide conversion was below 95% for three consecutive cycles. The catalyst's lifespan was calculated based on the first instance of a hydrogen peroxide conversion below 95%. Samples were taken at regular intervals, and the hydrogen peroxide conversion was determined by cerium sulfate titration, and the reaction products were analyzed by gas chromatography. Y PO S PO , The values ​​are: hydrogen peroxide conversion rate, propylene oxide yield, propylene oxide selectivity, and effective utilization rate of hydrogen peroxide. and n represents the amount of hydrogen peroxide entering the reactor and the amount of hydrogen peroxide exiting the reactor during the sampling period, respectively. PO n PGE n PG The molar amounts of propylene oxide, propylene glycol monomethyl ether, and propylene glycol in the product are calculated using the following equation.

[0054]

[0055]

[0056]

[0057]

[0058] Comparative Example 4

[0059] 100g of fresh titanium Ti-MWW silica molecular sieve was packed into a reactor, and the reaction solution was introduced. The reaction solution was then used to evaluate the catalyst's lifespan according to the experimental method described above.

[0060] Comparative Example 5

[0061] 100g of the same batch of deactivated Ti-MWW titanium-silicon molecular sieve as in Comparative Example 4 was packed into the reactor. The catalyst was first deactivated by nitrogen purging at 80°C for 6 hours at a nitrogen space velocity of 1.5 min⁻¹. -1 Then, the reactor was kept at 80°C, and ozone-containing nitrogen gas was introduced for 24 hours, with an ozone concentration of 80 mg / L and an ozone-containing nitrogen gas space velocity of 1 min. -1 After treatment, the reactor was stopped from being kept at 80°C, and simultaneously switched to nitrogen gas for purging containing ozone, with a nitrogen space velocity of 1 min. -1 The purging time was 6 hours. After purging, the lifetime of the regenerated catalyst was evaluated according to the above experimental method.

[0062] Comparative Example 6

[0063] 100g of the same batch of deactivated Ti-MWW titanium-silicon molecular sieve as in Comparative Example 4 was packed into the reactor. The catalyst was first deactivated by nitrogen purging at 80°C for 6 hours at a nitrogen space velocity of 1.5 min⁻¹. -1 Then, keeping the reactor at 80°C, water was blown into the reactor in the form of microdroplets using nitrogen gas at a nitrogen space velocity of 1 min. -1 The average droplet size is 5-10 μm, and the droplet space velocity is 2 h⁻¹. -1 The treatment time was 24 hours. After treatment, the reactor was stopped at 80°C and simultaneously switched to nitrogen gas to purge residual microdroplets, with a nitrogen space velocity of 1 min. -1 The purging time was 6 hours. After purging, the lifetime of the regenerated catalyst was evaluated according to the above experimental method.

[0064] Example 6

[0065] 100g of the same batch of deactivated Ti-MWW titanium-silicon molecular sieve as in Comparative Example 4 was packed into the reactor. The catalyst was first deactivated by nitrogen purging at 80°C for 6 hours at a nitrogen space velocity of 1.5 min⁻¹. -1 Then, keeping the reactor at 80°C, water was blown into the reactor in the form of microdroplets using ozone-containing nitrogen gas. The ozone concentration was 60 mg / L, and the ozone-containing nitrogen gas space velocity was 1 min. -1 The microdroplet size is 5-10 μm, and the microdroplet space velocity is 2 h⁻¹. -1 The treatment time was 12 hours. After treatment, the reactor was stopped and kept at 80°C. At the same time, nitrogen gas was switched on to purge residual microdroplets, with a nitrogen space velocity of 1 min. -1 The purging time was 6 hours. After purging, the lifetime of the regenerated catalyst was evaluated according to the above experimental method.

[0066] Example 7

[0067] The ozone-containing nitrogen gas was replaced with ozone-containing oxygen gas, and the other conditions were the same as in Example 6.

[0068] Example 8

[0069] After the reaction inactivation in Example 6, in-situ regeneration was performed again according to the method in Example 6.

[0070] Table 2 Evaluation Results of Comparative and Example Tables for Continuous Propylene Epoxidation Reactions

[0071]

[0072] The experimental data above show that using ozone-containing gas or water-carrier gas to create microdroplets for regeneration is not very effective, and the catalyst life can only be restored to 30-40% of its original life. However, using ozone-containing gas to create microdroplets can efficiently and quickly restore the catalyst activity, and the catalyst life can reach more than 95% of the original life, and it can be recycled.

[0073] Toluene hydroxylation was used as an example, with a Ti-MOR type titanium silicate molecular sieve as the catalyst. The evaluation method is as follows:

[0074] Ti-MOR titanium silicate molecular sieves were packed into a reactor equipped with a mechanical stirrer and a constant-temperature reflux device. Then, hydrogen peroxide (30% by mass), cresol, and water were added at a molar ratio of 1:2.2:2.5 (hydrogen peroxide:toluene:water), with a catalyst concentration of 10%. The reaction was mechanically stirred, and the reaction temperature was controlled at 65°C in a water bath for 6 hours. Gas phase analysis was used to determine the toluene conversion (X), the yield of o-cresol and p-cresol (Y), and the selectivity (S) of o-cresol and p-cresol. A toluene conversion rate below 25% was considered catalyst deactivation.

[0075] X(toluene) = n0(toluene) - n(toluene) / n0(toluene) * 100%

[0076] Y(o-cresol + p-cresol) = n(o-cresol + p-cresol) / n0(toluene) * 100%

[0077] S(o-cresol + p-cresol) = Y(o-cresol + p-cresol) / X(toluene) * 100%

[0078] In the formula, n0(toluene) represents the number of moles of toluene added, n(toluene) represents the number of moles of toluene remaining after the reaction, and n(o-cresol + p-cresol) represents the total number of moles of o-cresol and p-cresol produced after the reaction.

[0079] Comparative Example 7

[0080] 5g of fresh Ti-MOR titanium silicate molecular sieve was packed into a 100ml reactor, and the reaction solution was introduced. The reaction solution was evaluated according to the above experimental method to obtain the toluene conversion rate of the fresh catalyst, and the yield and selectivity of o-cresol and p-cresol.

[0081] Comparative Example 8

[0082] The Ti-MOR catalyst used in Comparative Example 7 was filtered and washed three times with 30g of methanol solvent each time, and then dried at 80℃. It was then added back to a 100ml reactor, and the reaction solution was purged. The reaction was evaluated according to the experimental method described above to obtain the toluene conversion rate, and the yields and selectivity of o-cresol and p-cresol when the fresh catalyst was reused.

[0083] Comparative Example 9

[0084] 5g of the same batch of deactivated Ti-MOR titanium-silicon molecular sieve from Comparative Example 7 was packed into a 100ml reactor. The deactivated catalyst was first purged with nitrogen at 60℃ for 9h at a nitrogen space velocity of 1min. -1 Then, keeping the reactor at 60°C, ozone-containing nitrogen gas was introduced into the reactor for treatment for 12 hours, with an ozone concentration of 60 mg / L and an ozone-containing nitrogen gas hourly space velocity of 1 min. -1 After treatment, the reactor was stopped at 60°C and simultaneously switched to nitrogen purging with ozone-containing nitrogen gas at a gas hourly space velocity (GHSV) of 1 min. -1 The purging time was 6 hours. After purging, the regenerated catalyst was evaluated according to the above experimental method to obtain the toluene conversion, yield, and selectivity of o-cresol and p-cresol.

[0085] Comparative Example 10

[0086] 5g of the same batch of deactivated Ti-MOR titanium-silicon molecular sieve from Comparative Example 7 was packed into a 100ml reactor. The deactivated catalyst was first purged with nitrogen at 60℃ for 9h at a nitrogen space velocity of 1min. -1 Then, keeping the reactor at 60°C, the water was treated with nitrogen gas through microdroplets for 12 hours, with a nitrogen space velocity of 1 min. -1 The microdroplet size is 10-20 μm, and the microdroplet space velocity is 2 h⁻¹. -1 After treatment, the reactor was stopped at 60°C and simultaneously switched to nitrogen gas to purge the micro-droplets, with a nitrogen space velocity of 1 min. -1 The purging time was 6 hours. After purging, the regenerated catalyst was evaluated according to the above experimental method to obtain the toluene conversion, yield, and selectivity of o-cresol and p-cresol.

[0087] Example 9

[0088] 5g of the same batch of deactivated Ti-MOR titanium-silicon molecular sieve from Comparative Example 7 was packed into a 100ml reactor. The deactivated catalyst was first purged with nitrogen at 60℃ for 9h at a nitrogen space velocity of 1min. -1 Then, keeping the reactor at 60°C, water was purged with ozone-containing nitrogen gas to form microdroplets for 12 hours, with an ozone concentration of 60 mg / L and a nitrogen space velocity of 1 min.-1 The microdroplet size is 5-10 μm, and the microdroplet space velocity is 2 h⁻¹. -1 After treatment, the reactor was stopped at 60°C and simultaneously switched to nitrogen gas to purge the slightly ozone-containing liquid droplets, with a nitrogen space velocity of 1 min. -1 The purging time was 6 hours. After purging, the regenerated catalyst was evaluated according to the above experimental method to obtain the toluene conversion, yield, and selectivity of o-cresol and p-cresol.

[0089] Example 10

[0090] 5g of the same batch of deactivated Ti-MOR titanium-silicon molecular sieve from Comparative Example 7 was packed into a 100ml reactor. The deactivated catalyst was first purged with nitrogen at 40℃ for 12h at a nitrogen space velocity of 2.5min / min. -1 Then, keeping the reactor at 40°C, water was purged with ozone-containing nitrogen gas to form microdroplets for 18 hours, with an ozone concentration of 100 mg / L and a nitrogen space velocity of 2.5 min⁻¹. -1 The microdroplet size is 1-5 μm, and the microdroplet space velocity is 3 h⁻¹. -1 After treatment, the reactor was stopped at 40°C and simultaneously switched to nitrogen gas to purge the slightly ozone-containing liquid droplets, with a nitrogen space velocity of 2 min⁻¹. -1 The purging time was 12 hours. After purging, the regenerated catalyst was evaluated according to the above experimental method to obtain the toluene conversion, yield, and selectivity of o-cresol and p-cresol.

[0091] Example 11

[0092] 5g of the same batch of deactivated Ti-MOR titanium-silicon molecular sieve from Comparative Example 7 was packed into a 100ml reactor. The deactivated catalyst was first purged with nitrogen at 100℃ for 8 hours at a nitrogen space velocity of 1.5 min⁻¹. -1 Then, keeping the reactor at 100°C, water was purged with ozone-containing nitrogen gas to form microdroplets for 18 hours, with an ozone concentration of 40 mg / L and a nitrogen space velocity of 2.5 min⁻¹. -1 The microdroplet size is 10-20 μm, and the microdroplet space velocity is 3 h⁻¹. -1 After treatment, the reactor was stopped from being kept at 100°C, and nitrogen gas was switched to purge the slightly ozone-containing liquid droplets, with a nitrogen space velocity of 1 min. -1 The purging time was 6 hours. After purging, the regenerated catalyst was evaluated according to the above experimental method to obtain the toluene conversion, yield, and selectivity of o-cresol and p-cresol.

[0093] Example 12

[0094] After filtering, the sample from Example 9 was placed in a 100 ml reactor. The catalyst was first deactivated by nitrogen purging at 80°C for 16 h at a nitrogen space velocity of 2 min⁻¹.-1 Then, the reactor was kept at 80°C, and water containing ozone and nitrogen was passed through to form microdroplets for 16 hours, with an ozone concentration of 90 mg / L and a nitrogen space velocity of 2 min⁻¹. -1 The microdroplet size is 3-6 μm, and the microdroplet space velocity is 2 h⁻¹. -1 After treatment, the reactor was stopped from being kept at 80°C, and simultaneously switched to nitrogen gas to purge the slightly ozone-containing liquid droplets, with a nitrogen space velocity of 2.5 min⁻¹. -1 The purging time was 4 hours. After purging, the regenerated catalyst was evaluated according to the above experimental method to obtain the toluene conversion, yield, and selectivity of o-cresol and p-cresol.

[0095] Example 13

[0096] After the reaction in Example 10 was completed, the sample was filtered and placed into a 100 ml reactor. In-situ regeneration was performed according to the method in Example 9, except that the ozone-containing nitrogen gas was replaced with ozone-containing oxygen gas.

[0097] Table 3 Evaluation Results of Toluene Hydroxylation Reactions: Comparative Examples and Case Studies

[0098]

[0099] A phenol hydroxylation example was used, with a Ti-MOR type titanium silicate molecular sieve as the catalyst. The evaluation method is as follows:

[0100] Ti-MOR titanium silicate molecular sieves were packed into a reactor equipped with a mechanical stirrer and a constant-temperature reflux device. Then, 30% hydrogen peroxide, phenol, and methanol were added at a hydrogen peroxide:toluene:methanol molar ratio of 1:2.5:3.5, with a catalyst concentration of 5%. The reaction was mechanically stirred, and the reaction temperature was controlled at 60°C in a water bath for 3 hours. Gas phase analysis was used to measure the phenol conversion (X), the yield (Y) of catechol and hydroquinone, and the selectivity (S) of catechol and hydroquinone. A phenol conversion rate below 15% was considered catalyst deactivation.

[0101] X(phenol) = n0(phenol) - n(phenol) / n0(phenol) * 100%

[0102] Y(catechol and hydroquinone) = n(catechol and hydroquinone) / n0(phenol) * 100%

[0103] S(catechol and hydroquinone) = Y(catechol and hydroquinone) / X(phenol) * 100%

[0104] In the formula, n0 (phenol) represents the number of moles of toluene added, n (phenol) represents the number of moles of toluene remaining after the reaction, and n (catechol and hydroquinone) represents the total number of moles of catechol and hydroquinone produced after the reaction.

[0105] Comparative Example 11

[0106] 2.5g of fresh Ti-MOR titanium silicate molecular sieve was packed into a 100ml reactor, and the reaction solution was introduced. The reaction solution was evaluated according to the above experimental method to obtain the toluene conversion rate of the fresh catalyst, and the yield and selectivity of catechol and hydroquinone.

[0107] Comparative Example 12

[0108] The Ti-MOR sample from Comparative Example 11 was filtered and then washed three times with 20g of methanol solvent each time. After washing, it was dried at 80°C. The sample was then added back into a 100ml reactor, and the reaction solution was purged. The reaction was evaluated according to the experimental method described above to obtain the phenol conversion rate, catechol and hydroquinone yields and selectivity of the first reaction with fresh catalyst.

[0109] Comparative Example 13

[0110] 2.5 g of the same batch of deactivated Ti-MOR titanium-silicon molecular sieve as in Comparative Example 11 was packed into a 100 ml reactor. The deactivated catalyst was first purged with nitrogen at 60 °C for 9 h at a nitrogen space velocity of 1 min. -1 Then, keeping the reactor at 60°C, ozone-containing nitrogen gas was introduced into the reactor for treatment for 12 hours, with an ozone concentration of 60 mg / L and an ozone-containing nitrogen gas hourly space velocity of 1 min. -1 After treatment, the reactor was stopped at 60°C and simultaneously switched to nitrogen purging with ozone-containing nitrogen gas at a gas hourly space velocity (GHSV) of 1 min. -1 The purging time was 6 hours. After purging, the regenerated catalyst was evaluated according to the above experimental method to obtain the phenol conversion rate, catechol and hydroquinone yields and selectivity.

[0111] Comparative Example 14

[0112] 2.5 g of the same batch of deactivated Ti-MOR titanium-silicon molecular sieve as in Comparative Example 11 was packed into a 100 ml reactor. The deactivated catalyst was first purged with nitrogen at 60 °C for 9 h at a nitrogen space velocity of 1 min. -1 Then, keeping the reactor at 60°C, the water was treated with nitrogen gas through microdroplets for 12 hours, with a nitrogen space velocity of 1 min. -1 The microdroplet size is 10-20 μm, and the microdroplet space velocity is 2 h⁻¹. -1 After treatment, the reactor was stopped at 60°C and simultaneously switched to nitrogen gas to purge the micro-droplets, with a nitrogen space velocity of 1 min. -1 The purging time was 6 hours. After purging, the regenerated catalyst was evaluated according to the above experimental method to obtain the phenol conversion rate, catechol and hydroquinone yields and selectivity.

[0113] Example 14

[0114] 2.5 g of the same batch of deactivated Ti-MOR titanium-silicon molecular sieve as in Comparative Example 11 was packed into a 100 ml reactor. The deactivated catalyst was first purged with nitrogen at 60 °C for 9 h at a nitrogen space velocity of 1 min. -1 Then, keeping the reactor at 60°C, water was purged with ozone-containing nitrogen gas to form microdroplets for 12 hours, with an ozone concentration of 60 mg / L and a nitrogen space velocity of 1 min. -1 The microdroplet size is 5-10 μm, and the microdroplet space velocity is 2 h⁻¹. -1 After treatment, the reactor was stopped at 60°C and simultaneously switched to nitrogen gas to purge the slightly ozone-containing liquid droplets, with a nitrogen space velocity of 1 min. -1 The purging time was 6 hours. After purging, the regenerated catalyst was evaluated according to the above experimental method to obtain the phenol conversion rate, catechol and hydroquinone yields and selectivity.

[0115] Example 15

[0116] The inactivated sample from Example 14 was regenerated according to the method in Example 14, and then evaluated.

[0117] Table 4 Evaluation Results of Phenol Hydroxylation Reactions: Comparative Examples and Case Studies

[0118]

[0119] The hydroxylation reactions of toluene and phenol easily produce tar, and a single reaction can cause catalyst deactivation. Comparative Examples 8 and 11 show that the catalyst activity is only 30-40% of that of fresh catalyst. Comparative Examples 9, 10, 13, and 14, treated with a single ozone-containing gas or a single nitrogen-containing micro-droplet water treatment, restored the catalyst activity to 45-60% of that of fresh catalyst. Using ozone-containing gas to form micro-droplets and introducing them into the reactor can achieve efficient in-situ regeneration, restoring the catalyst activity to more than 95% of the activity of the deactivated catalyst.

[0120] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for improving the in-situ regeneration efficiency of titanium-silicon molecular sieves, characterized in that, This method utilizes the combined effect of microdroplet electric field and ozone to improve the in-situ regeneration efficiency of deactivated titanium-silicon molecular sieves, and specifically includes the following steps: Step (1) First, heat the reactor containing the deactivated titanium-silicon molecular sieve. While heating, nitrogen gas is introduced into the reactor at atmospheric pressure to dry the reaction liquid on the surface and inside of the deactivated titanium-silicon molecular sieve. The reactor temperature is 30-120℃, the heating rate is 0.2-5℃ / min, and the nitrogen space velocity is 0.1-5min. -1 The purging time is 1-24 hours; After nitrogen purging is completed in step (2), the reactor temperature is changed, and ozone-containing gas is used to blow water into the reactor in the form of micro-droplets for a certain period of time. The combined effect of the micro-droplet electric field generated by the water micro-droplets and ozone is used to oxidize and eliminate the carbon deposits on the surface and inside the pores of the molecular sieve. The reactor temperature is 30-120℃, the ozone concentration is 20-120 mg / L, and the ozone gas space velocity is 0.1-5 min. -1 The ozone-containing gas is introduced over a period of 3-18 hours. The microdroplets have a particle size of 1-20 μm and a space velocity of 0.5-5 h⁻¹. -1 ; Step (3) involves lowering the reactor temperature while simultaneously purging the reactor with nitrogen containing ozone microdroplets to obtain in-situ regenerated titanium-silicon molecular sieves; nitrogen space velocity is 0.5-5 min. -1 Purging time is 3-24 hours.

2. The method for improving the in-situ regeneration efficiency of titanium-silicon molecular sieves according to claim 1, characterized in that, The deactivated titanium-silicon molecular sieve is suitable for titanium-silicon molecular sieves that have been deactivated after chloropropylene epoxidation, propylene epoxidation, phenol hydroxylation, or toluene hydroxylation.

3. The method for improving the in-situ regeneration efficiency of titanium-silicon molecular sieves according to claim 2, characterized in that, The deactivated titanium-silicon molecular sieve is a deactivated TS-1 type titanium-silicon molecular sieve, a Ti-MWW type titanium-silicon molecular sieve, or a deactivated Ti-MOR type titanium-silicon molecular sieve.

4. The method for improving the in-situ regeneration efficiency of titanium-silicon molecular sieves according to claim 1, characterized in that, Before proceeding with step (1), the reaction liquid in the reactor is emptied in advance.

5. The method for improving the in-situ regeneration efficiency of titanium-silicon molecular sieves according to claim 1, characterized in that, In step (2), the carrier containing ozone gas is nitrogen, oxygen, argon, helium, or any combination of these gases.

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