Process for the regeneration of a clay catalyst and regenerated clay catalyst

Abstract

The application provides a regeneration method of a clay catalyst and a regenerated clay catalyst. The regeneration method comprises the following steps: pressurized separation of the clay catalyst and residual reaction liquid on the surface of the clay catalyst to obtain a first separation product and the residual reaction liquid; heating and performing a depolymerization reaction on the residual reaction liquid under the action of a depolymerization catalyst to obtain a gaseous monomer; performing a depolymerization reaction on residual reaction liquid in the first separation product to obtain a second separation product and a liquid monomer; after condensation, the gaseous monomer is washed with the second separation product; purging a third separation product to obtain the clay catalyst and a gaseous component; and using a gas containing N2O to perform oxidative decomposition on the clay catalyst. The application converts the washing process into a polymer depolymerization reaction by using the acid sites of the clay catalyst, and combines the N2O low-temperature oxidation regeneration technology to avoid damage to the crystal structure; the regenerated catalyst has both adsorption performance and depolymerization catalytic activity.

Description

TECHNICAL FIELD

[0001] The present application relates to a regeneration method of a clay catalyst and the regenerated clay catalyst. BACKGROUND

[0002] Clay minerals are a kind of hydrous silicate minerals with a layered structure, mainly composed of SiO2, Al2O3 and water, typical representatives including kaolin, montmorillonite and bentonite, etc. The unique layered structure endows it with the characteristics of interlayer ion exchange, interlayer adsorption, interlayer expansion, thixotropic bonding, etc. The acid-modified clay catalyst has the advantages of high conversion rate, long service life, and neutral product characteristics in the ring-opening polymerization and copolymerization of ethylene oxide, propylene oxide and other cyclic ether compounds.

[0003] In such catalytic polymerization reactions, metal ions, organic impurities and heavy components carried by the raw materials will continue to accumulate on the surface of the catalyst through impregnation adsorption. These pollutants not only occupy the acid active sites, but also block the structure channels, resulting in the following deactivation characteristics of the catalyst: (1) deterioration of product color value; (2) increase in the proportion of polymerization side reactions (chain transfer, chain exchange); (3) deviation of product viscosity and molecular weight distribution from the control indicators. When the above deactivation phenomena are concentrated, the catalyst needs to be replaced in batches. However, the catalyst in the high-viscosity polymer system is difficult to unload directly, and needs to be cleaned through multiple processes to remove the polymer residues in the pores before it can be disposed of or regenerated, which not only produces high-concentration organic wastewater, but also has very high treatment cost.

[0004] The existing regeneration technology has obvious defects: US5268345A discloses a treatment of polytetrahydrofuran (PTMEG) waste catalyst, which uses water and methanol to clean, resulting in a large amount of wastewater; JP1985075331A uses a water-based mixture of methanol or ethanol to wash the clay catalyst to achieve regeneration, and uses the regenerated catalyst for dehydration reaction, esterification reaction, etherification reaction and alkylation reaction, but still has the problems of large amount of wastewater and high treatment cost.

[0005] The conventional treatment method in the industry uses organic solvents (methanol, ethanol, etc.) or steam to clean the polymer on the surface of the catalyst, supplemented by high-temperature calcination to achieve harmless treatment. However, according to the research in Issue 4, Volume 42 of Silicate Bulletin, calcination temperatures exceeding 600℃ will destroy the crystal structure of clay minerals, promote the amorphous transformation of Al2O3 and SiO2, and cause irreversible loss of catalytic activity.

[0006] Therefore, it is urgent to develop an environmentally friendly, low-cost and non-damaging regeneration method for the performance of the catalyst to realize the recycling of the catalyst, reduce production cost and reduce environmental pollution. SUMMARY

[0007] The technical problem solved by the present application is to overcome the defects of the regeneration method of clay catalysts in the prior art, such as environmental pollution, reduced catalytic activity, and high processing cost, and to provide a regeneration method of clay catalysts and regenerated clay catalysts. The present application uses the acid sites of the waste catalyst to convert the washing process into a polymer depolymerization reaction, and simultaneously completes depolymerization and washing without the need for additional addition of other cleaning media such as solvents and water, and combines N2O low-temperature oxidation regeneration technology to avoid damage to the crystal structure caused by high-temperature calcination; the regenerated catalyst has both adsorption performance and depolymerization catalytic activity, and can be reused for polymerization reactions, depolymerization reactions, or used as an adsorbent in the wastewater treatment industry. This technology simultaneously solves the problems of solvent consumption, wastewater discharge, and high cost, and has significant environmental benefits.

[0008] The present application solves the above technical problems by the following technical solutions.

[0009] The inventors of the present application have creatively constructed a self-purification mechanism, which utilizes the acid sites of the clay catalyst itself to achieve depolymerization of the residual polymers on the surface and in the pores of the clay catalyst, generating gas-phase monomers; and the liquid-phase monomers formed by condensation are used to wash the catalyst, achieving in-situ restoration of the flowability of the catalyst. This cyclic process not only avoids the use of external solvents, but also enables the full recovery of polymers in the form of monomers.

[0010] The present application provides a regeneration method of clay catalysts, which comprises the following steps:

[0011] Step 1: pressurized separation of the clay catalyst and the residual reaction liquid on the surface of the clay catalyst to obtain a first separation product and a residual reaction liquid; the residual reaction liquid comprises residual polymers;

[0012] Step 2: heating the residual reaction liquid under the action of a depolymerization catalyst to perform a depolymerization reaction, obtaining a gas-phase monomer;

[0013] Step 3: heating the first separation product to achieve depolymerization of the residual reaction liquid in the first separation product, obtaining a second separation product and a liquid-phase monomer; the gas-phase monomer is washed after condensation and is in contact with the second separation product, and a third separation product and a washing liquid are separated;

[0014] Step 4: purging the third separation product to obtain a clay catalyst and a gas-phase component;

[0015] Step 5: using a gas containing N2O to perform oxidative decomposition on the clay catalyst obtained in step 4; the temperature of the oxidative decomposition is 300-600℃.

[0016] In the present application, the clay catalyst can be selected from one or more of sodium-based montmorillonite, calcium-based montmorillonite, kaolin, bentonite, and halloysite, for example, sodium-based montmorillonite.

[0017] In the present application, preferably, the residual polymer is polytetrahydrofuran, and the monomer is tetrahydrofuran.

[0018] In the present application, preferably, in step 1, the pressurized separation is performed by means of introducing an inert atmosphere. The inert atmosphere is preferably nitrogen.

[0019] In the present application, in step 1, the residual reaction solution can further include unreacted monomers and / or organic impurities. The organic impurities mainly come from by-products generated during the polymerization process, and the content is relatively low, which usually does not have a significant impact on the subsequent regeneration method.

[0020] In the present application, after the pressurized separation in step 1, the impregnation of the clay catalyst surface and the inside of the pores still has residual reaction solution that is difficult to separate, which needs to be further separated.

[0021] In the present application, in step 2, the depolymerization catalyst can be selected from a clay catalyst. The depolymerization catalyst used in the present application can be selected from a new clay catalyst or a regenerated clay catalyst.

[0022] In the present application, in step 3, preferably, the heat source for heating comes from the condensation heat of the gas-phase monomers generated in step 2. The gas-phase monomers generated in step 2 can be directly used in step 3, and the heat released by condensation promotes the depolymerization reaction of the residual polymer on the surface and in the pores of the clay catalyst.

[0023] In the present application, in step 2 or step 3, the temperature of the depolymerization reaction can be independently 110-220℃, preferably 130-200℃, more preferably 150-180℃, for example 155℃, 160℃ or 165℃.

[0024] In the present application, in step 2 or step 3, the pressure of the depolymerization reaction can be independently 0.2-3.5MPa, preferably 0.3-2.5MPa, more preferably 0.5-1.0MPa, for example 0.75MPa or 0.8MPa.

[0025] In the present application, after step 3 and before step 4, a step of judging whether the clay catalyst has completely recovered fluidity can be further included; if the fluidity has not been completely recovered, the operations of step 2 to step 3 are repeated in turn until the fluidity is completely recovered; if the fluidity has been completely recovered, the operation of step 4 is performed.

[0026] Preferably, according to the size of the angle of repose, it is judged whether the clay catalyst has completely recovered fluidity; when the angle of repose is ≤45°, it indicates that the clay catalyst has completely recovered fluidity, and the cycle is stopped.

[0027] Preferably, if the flowability is not fully recovered, the washing liquid produced in step 3 is recycled to step 2, the residual polymer in the washing liquid is subjected to the first depolymerization reaction to produce the gaseous monomer, and the liquid monomer in the washing liquid is partially gasified into the gaseous monomer; the produced gaseous monomer is reused in step 3 to form a recycling and regeneration process.

[0028] Preferably, in step 3, the washing liquid can also be used for monomer purification and recovery. The washing liquid produced in step 3 contains a large amount of liquid monomer, a part of which is used for gasification into gaseous monomer and recycling to step 2, and the other part of which is used for purification and recovery.

[0029] Preferably, in step 4, the purging is performed by using a hot nitrogen stripping method.

[0030] In the hot nitrogen stripping method, the temperature of the hot nitrogen can be 150-180℃, for example, 165℃.

[0031] In the hot nitrogen stripping method, the system pressure can be 0.1-0.5MPa, for example, 0.15MPa.

[0032] Preferably, in the hot nitrogen stripping method, the supply of hot nitrogen is terminated when the detected monomer content in the hot nitrogen is lower than 500ppm.

[0033] In step 4, after purging the third separation product, the operation of monomer purification and recovery of the gaseous components is further included.

[0034] Preferably, the monomer is purified and recovered by using a rectification method, for example, THF monomer is purified and recovered by using a three-tower rectification method. Preferably, the three-tower rectification is performed by using an atmospheric tower, a pressurized tower and a refining tower.

[0035] In step 5, the N2O-containing gas can be pure N2O or a mixed gas of N2O and air; when the N2O-containing gas is a mixed gas of N2O and air, the molar ratio of N2O to air is 1:(1-1000).

[0036] In step 5, the total volume space velocity of the N2O-containing gas can be 50-2000hr -1 , for example, 1000hr -1 In the present application, the total volume space velocity refers to the volume flow rate of the gas passing through a unit volume of catalyst per unit time.

[0037] In step 5, the oxidative decomposition can be achieved by heating operation. The temperature of the oxidative decomposition can be 300-550℃, for example, 300℃. The time of the oxidative decomposition can be 1-12h, for example, 3h.

[0038] The application adopts N2O as a regeneration gas to perform redox treatment on the catalyst, compared with traditional high-temperature calcination (700-1000 DEG C), the method can effectively decompose heavy component organic matters in the catalyst pores at a lower temperature, and avoid irreversible damage to the catalyst structure caused by sharp heat release in the traditional high-temperature calcination method, so as to retain the activity of the catalyst and optimize the pore structure of the catalyst, and good adsorption is shown.

[0039] In the application, preferably, the regeneration method is performed by using the following regeneration system:

[0040] The regeneration system comprises a first reactor, a second reactor and a calcining device.

[0041] The internal space of the first reactor is used for loading the clay catalyst to be regenerated, the first reactor further comprises a first inlet, a first outlet, a second outlet and a fourth inlet, the fourth inlet is used for introducing inert gas; the second reactor comprises a second inlet and a third outlet; the calcining device comprises a third inlet, and the calcining device is used for oxidizing and decomposing the clay catalyst;

[0042] The first outlet is communicated with the second inlet through a first pipeline, the first outlet is used for conveying residual reaction liquid separated by step 1 pressurization in the first reactor or washing liquid generated in step 3 into the first pipeline; the second reactor is used for depolymerizing residual polymers in the residual reaction liquid or the washing liquid to obtain gas-phase monomers, and the gas-phase monomers are output from the third outlet, and the first inlet is used for introducing the gas-phase monomers into the first reactor to wash the first separation product or the second separation product in the first reactor;

[0043] The second outlet is communicated with the third inlet through a third pipeline, and the second outlet is used for discharging the separated clay catalyst into the third pipeline;

[0044] The third outlet is communicated with the first inlet through a second pipeline.

[0045] Preferably, the first reactor further comprises a fourth outlet, the first inlet and the fourth inlet are located at the upper part of the first reactor, the first outlet and the second outlet are located at the bottom of the first reactor, and the fourth outlet is located at the top of the first reactor, and the fourth outlet is used for discharging inert gas carrying gas-phase monomers.

[0046] Preferably, the first reactor further comprises a fifth inlet, the fifth inlet is arranged at the lower part of the first reactor, and the fifth inlet is used for introducing inert gas.

[0047] Preferably, the regeneration system further comprises a first delivery pump arranged on the first pipeline, the first delivery pump being used to pressurize the residual reaction liquid or the washing liquid in the first pipeline so as to make the residual reaction liquid or the washing liquid enter the second reactor.

[0048] Preferably, the regeneration system further comprises a second collection tank arranged on the first pipeline, the inlet and the outlet of the second collection tank being communicated with the first pipeline, the second collection tank being used to collect the residual reaction liquid or the washing liquid.

[0049] The present application further provides a regenerated clay catalyst, which is obtained by the regeneration method as described above.

[0050] In the present application, the regenerated clay catalyst can be reused for ring-opening polymerization reaction, and can be used as an adsorbent and a depolymerization catalyst.

[0051] On the basis of common general knowledge in the art, the above-mentioned preferred conditions can be combined arbitrarily, thereby obtaining various preferred examples of the present application.

[0052] The reagents and raw materials used in the present application are commercially available.

[0053] The positive progress effect of the present application is that:

[0054] (1) The present application is based on a self-purification mechanism, which effectively prevents secondary pollution by avoiding the introduction of external solvents, and completely eliminates the generation of organic wastewater; at the same time, the established material internal circulation mechanism overcomes the technical difficulties of large solvent consumption, large wastewater discharge and high treatment cost in traditional processes, realizes the closed-loop utilization of materials, significantly improves the raw material utilization rate and greatly reduces the treatment cost.

[0055] (2) The present application simultaneously utilizes N2O oxidation regeneration technology to completely decompose the residual heavy components and polymers at a lower temperature, avoids the damage to the crystal structure of the catalyst caused by the traditional high-temperature calcination method, and maximizes the recovery of the catalyst performance.

[0056] (3) The regenerated catalyst of the present application has good adsorption performance and can be used as an adsorbent for wastewater treatment and other environmental protection fields; it also has good depolymerization catalytic activity and can be used as a depolymerization catalyst for depolymerization of polymers; it reduces resource waste and environmental pollution, and has good environmental protection benefits. BRIEF DESCRIPTION OF DRAWINGS

[0057] Figure 1 FIG. 1 is a structural schematic diagram of the regeneration system of Example 1.

[0058] Legend of reference signs:

[0059] first reactor 1

[0060] first inlet 101

[0061] first outlet 102

[0062] second outlet 103

[0063] fourth inlet 104

[0064] fourth outlet 105

[0065] fifth inlet 106

[0066] second reactor 2

[0067] second inlet 201

[0068] third outlet 202

[0069] level controller 203

[0070] calcination device 3

[0071] third inlet 301

[0072] fifth outlet 302

[0073] eighth inlet 303

[0074] condenser 4

[0075] monomer purification and recovery device 5

[0076] sixth inlet 501

[0077] seventh inlet 502

[0078] first pipe 6

[0079] second pipe 7

[0080] third pipe 8

[0081] fourth pipe 9

[0082] fifth pipe 10

[0083] first valve 11

[0084] second valve 12

[0085] third valve 13

[0086] first transfer pump 14

[0087] second transfer pump 15

[0088] first collection tank 16

[0089] gas discharge port 161

[0090] Second collection tank 17 DETAILED DESCRIPTION

[0091] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0092] It should be noted that if the embodiments of the present application involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement condition, etc. between components in a certain posture, and if the certain posture changes, the directional indications also change accordingly.

[0093] In addition, if the embodiments of the present application involve descriptions such as “first”, “second”, etc., the descriptions of “first”, “second”, etc. are only for description purposes, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features limited by “first” and “second” can explicitly or implicitly include at least one of the features. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the fact that a person of ordinary skill in the art can realize it, and when the combination of technical solutions contradicts each other or cannot be realized, it should be considered that the combination of technical solutions does not exist and is not within the scope of protection claimed by the present application.

[0094] The waste catalyst of a polytetrahydrofuran device of an enterprise in Xinjiang adopts K-306 clay catalyst of Clariant, the main raw material is sodium-based montmorillonite, and has been continuously operated for 7 years and needs to be scrapped. The loading amount of the reactor catalyst is 50 tons.

[0095] Example 1

[0096] Step 1, in the polymerization reactor, the residual reaction liquid (including polytetrahydrofuran (PTMEG), unreacted tetrahydrofuran (THF) monomer and other trace amounts of organic impurities) remaining on the surface of the catalyst to be recovered is blown to a collection tank by using nitrogen.

[0097] The main components of the residual reaction liquid are PTMEG and THF, and the specific contents are as shown in Table 1:

[0098] Table 1

[0099]

[0100] Step 2, the residual reaction solution is transported to the depolymerization reactor by a transport pump, and a depolymerization reaction occurs under the catalysis of a brand-new clay catalyst (Claysoil Catalyst K-306, main raw material sodium-based montmorillonite) (the pressure is maintained at 0.8 MPa, and the temperature is controlled at 160±5°C), to generate THF monomers and a small amount of water, forming a gaseous mixture.

[0101] Step 3, the gaseous mixture of THF monomers and water formed in Step 2 is introduced into the polymerization reactor in a gaseous phase from the top of the depolymerization reactor, and is in contact with the catalyst to be recovered, and the gaseous phase condenses to release heat, so that the temperature of the polymerization reactor is maintained at 160±5°C, and the pressure is 0.75 MPa.

[0102] Under this condition, the residual polymer immersed in the channels in Step 1 is decomposed into THF monomers and water by using the acid sites of the catalyst to be recovered; in this process, the generated liquid-phase THF monomers and water also play a washing role, and dissolve and remove the accumulated substances on the surface and in the channels of the catalyst to be recovered.

[0103] The mixture in the polymerization reactor enters a collection tank from top to bottom, and is then transported to the depolymerization reactor by a transport pump, to generate a gaseous mixture of THF and water, part of which continues to circulate back to the reactor, and part of which is transported to a monomer purification and recovery device under the liquid level control of the depolymerization reactor. The decomposition and washing are continued until the surface of the catalyst to be recovered is clean and the fluidity is restored.

[0104] During this period, the fluidity of the catalyst to be recovered is judged according to the size of the angle of repose, and when the angle of repose is ≤45°, it is considered that the fluidity of the catalyst has been restored. If it has been restored, Step 4 is performed; if it has not been completely restored, the process cycle is continued in Step 2.

[0105] Step 4, when the surface of the catalyst is clean and the fluidity is restored, a stripping method is used to remove residual THF and water, hot nitrogen gas at 165°C is introduced into the polymerization reactor, and the system pressure is maintained at 0.15 MPa, and the gaseous phase components discharged are condensed, THF monomers are transported to a monomer purification and recovery device, and hot nitrogen is discharged. When the THF content in the hot nitrogen gas in the polymerization reactor is less than 500 ppm, the nitrogen gas supply is terminated, and the catalyst to be recovered is unloaded.

[0106] Step 5, the catalyst to be recovered is transported to a rotary kiln, and a pure N2O is used as a regeneration gas to perform a redox treatment at a low temperature of 300°C for 3 h, and the total volume space velocity is 1000 h -1 The regenerated catalyst is unloaded into a barrel for standby, and the catalyst regeneration process is completed.

[0107] The structure diagram of the above-mentioned regeneration system is shown in Figure 1 , and specifically:

[0108] The regeneration system comprises a first reactor 1, a second reactor 2 and a calcining device 3; the internal space of the first reactor 1 is used for loading the clay catalyst to be regenerated, the first reactor 1 further comprises a first inlet 101, a first outlet 102, a second outlet 103 and a fourth inlet 104, the fourth inlet 104 is used for introducing inert gas; the second reactor 2 comprises a second inlet 201 and a third outlet 202; the calcining device 3 comprises a third inlet 301, and the calcining device 3 is used for oxidizing and decomposing the clay catalyst; the first outlet 102 is communicated with the second inlet 201 through a first pipeline 6, the first outlet 102 is used for conveying the residual reaction liquid separated by pressurized separation in step 1 or the washing liquid generated in step 3 to the first pipeline 6; the second reactor 2 is used for depolymerizing the residual polymer in the residual reaction liquid or the washing liquid to obtain a gas-phase monomer, and the gas-phase monomer is output by the third outlet 202; the first inlet 101 is used for introducing the gas-phase monomer into the first reactor 1 to wash the first separation product or the second separation product in the first reactor 1; the second outlet 103 is communicated with the third inlet 301 through a third pipeline 8, and the second outlet 103 is used for discharging the separated clay catalyst to the third pipeline 8; and the third outlet 202 is communicated with the first inlet 101 through a second pipeline 7. Specifically, the calcining device 3 is a rotary kiln.

[0109] By setting the first reactor 1, the second reactor 2 and the calcining device 3 to work cooperatively, the method of inert gas auxiliary blowing and gas-phase monomer circulating washing is used to replace the traditional chemical cleaning method, the efficient regeneration of the clay catalyst is realized, the residual reaction liquid or the washing liquid is preliminarily separated from the clay catalyst in the first reactor 1, the residual reaction liquid or the washing liquid is recycled to the first reactor 1 after being depolymerized into a gas-phase monomer by the second reactor 2 and is used for washing, the pollution of chemical solvents and the abrasion of the catalyst are avoided, and finally the residual impurities are completely oxidized and decomposed by the calcining device 3, so that the problems of incomplete cleaning of the traditional device, large solvent consumption, serious wastewater pollution and mechanical damage of the catalyst are solved, and the regeneration system has the significant advantages of high regeneration efficiency, environmental protection and energy saving and low catalyst loss.

[0110] In the embodiment, the first reactor 1 further comprises a fourth outlet 105, the first inlet 101 and the fourth inlet 104 are located at the upper part of the first reactor 1, the first outlet 102 and the second outlet 103 are located at the bottom of the first reactor 1, and the fourth outlet 105 is located at the top of the first reactor 1, and the fourth outlet 105 is used for discharging the inert gas carrying the gas-phase monomer. The inert gas is nitrogen.

[0111] By setting the fourth outlet 105 at the top, the inert gas carrying the gas-phase monomer can be discharged from the first reactor 1 in time, the accumulation of the inert gas in the reactor is effectively prevented to cause the pressure to rise, and the internal pressure of the reactor is ensured to be stable and the airflow is ensured to be smooth.

[0112] Further, the first reactor 1 further comprises a fifth inlet 106, which is arranged at the lower part of the first reactor 1 and is used for introducing inert gas.

[0113] In this embodiment, the regeneration system further comprises a monomer collecting device, which comprises a condenser 4, an inlet of the condenser 4 being communicated with the fourth outlet 105, and the condenser 4 is used for condensing the inert gas carrying the gaseous monomer.

[0114] By additionally arranging the monomer collecting device with the condenser 4 and communicating the fourth outlet 105 with the inlet of the condenser 4, the inert gas carrying the gaseous monomer discharged from the first reactor 1 can be effectively condensed, so that the gaseous monomer is liquefied and recovered, not only realizing the recycling of the monomer, but also avoiding the environmental pollution and resource waste caused by direct discharge of the monomer, and reducing the content of the monomer entrained in the inert gas.

[0115] Specifically, the inert gas carrying the gaseous monomer is output from the fourth outlet 105 of the first reactor 1, input into the condenser 4, condensed through the condenser 4, and the monomer is changed from gaseous phase to liquid phase, so that the monomer and the inert gas are separated.

[0116] The collecting device further comprises a first collecting tank 16, an inlet of the first collecting tank 16 being communicated with an outlet of the condenser 4, and the first collecting tank 16 is used for collecting the monomer condensate output from the condenser 4. A gas discharge port 161 is further arranged on the first collecting tank 16, and the gas discharge port 161 is used for discharging the inert gas.

[0117] By additionally arranging the first collecting tank 16 communicated with the outlet of the condenser 4, the monomer condensate output from the condenser 4 can be collected in the first collecting tank 16, so that the stable storage and subsequent recycling of the monomer condensate are realized. By arranging the gas discharge port 161 on the first collecting tank 16, the remaining inert gas after condensation can be discharged in time, so that the abnormal increase of the pressure in the tank is prevented, the stable pressure in the first collecting tank 16 is ensured, and the safe storage and normal collection of the monomer condensate are ensured.

[0118] In this embodiment, the regeneration system further comprises a monomer purification and recovery device 5, which comprises a sixth inlet 501 communicated with a liquid outlet of the first collecting tank 16 through a fourth pipeline 9, and the monomer purification and recovery device 5 is used for purifying the recovered monomer condensate.

[0119] By additionally arranging the monomer purification and recovery device 5 communicated with the liquid outlet of the collecting tank, the recovered monomer condensate can be further purified and treated to remove the impurities and unreacted components, so that the purity and quality of the monomer are significantly improved.

[0120] Specifically, the monomer purification and recovery device 5 further comprises a seventh inlet 502, and the seventh inlet 502 is communicated with the third outlet 202 through the fifth pipeline 10. A part of the gas-phase monomer produced by the depolymerization in the second reactor 2 is transported into the first reactor 1 through the second pipeline 7 to wash the clay catalyst in the first reactor 1, and another part is directly transported into the monomer purification and recovery device 5 for purification and recovery.

[0121] In the embodiment, the regeneration system further comprises a first delivery pump 14 arranged on the first pipeline 6, and the first delivery pump 14 is used to pressurize the residual reaction liquid or the washing liquid in the first pipeline 6 so that the residual reaction liquid or the washing liquid enters the second reactor 2. The fourth pipeline 9 is further provided with a second delivery pump 15, and the second delivery pump 15 is used to pressurize the monomer condensate in the fourth pipeline 9 so that the monomer condensate enters the monomer purification and recovery device 5.

[0122] By arranging the first delivery pump 14 and the second delivery pump 15 on the key pipelines, the residual reaction liquid or the washing liquid and the monomer condensate are effectively pressurized and delivered, respectively, so that the residual reaction liquid or the washing liquid can smoothly enter the second reactor 2 from the first reactor 1 through the first pipeline 6 for depolymerization treatment, and the monomer condensate can stably enter the monomer purification and recovery device 5 from the first collection tank 16 through the fourth pipeline 9 for purification. This not only improves the material transmission efficiency of each process link and the continuity of system operation, but also avoids the problem of poor delivery caused by insufficient fluid pressure, thereby enhancing the reliability and stability of the entire regeneration system operation.

[0123] Optionally, the regeneration system further comprises a second collection tank 17 arranged on the first pipeline 6, and the inlet and the outlet of the second collection tank 17 are communicated with the first pipeline 6. The second collection tank 17 is used to collect the residual reaction liquid or the washing liquid.

[0124] By arranging the second collection tank 17 on the first pipeline 6, the residual reaction liquid or the washing liquid discharged from the first reactor 1 can be temporarily stored and collected, thereby providing a stable buffering and adjusting function for subsequent delivery of the residual reaction liquid or the washing liquid to the second reactor 2 for depolymerization treatment, so as to ensure that the waste liquid enters the subsequent treatment link at a controllable flow rate and pressure, and avoid affecting the stable operation of the second reactor 2 due to flow fluctuation.

[0125] The use method of the regeneration system of the clay catalyst will be specifically described below in combination with Figure 1

[0126] ​The clay catalyst to be treated is loaded into the first reactor 1 through the special loading port of the first reactor 1. The first reactor 1 is provided with a first inlet 101 on the right side wall of the upper part, a fourth inlet 104 on the left side wall of the upper part, a fifth inlet 106 on the left side wall of the lower part, a fourth outlet 105 on the top, and a first outlet 102 and a second outlet 103 on the bottom. The fourth inlet 104 and the fifth inlet 106 are used to introduce inert gas nitrogen to purge the surface of the clay catalyst in the first reactor 1, so as to pressurize and separate the residual reaction liquid on the surface of the clay catalyst. The residual reaction liquid (containing residual polymer) generated after pressurization and separation is discharged from the first outlet 102, collected by the second collection tank 17 provided on the first pipeline 6, and communicated with the inlet of the second reactor 2. A first delivery pump 14 is further provided between the second collection tank 17 and the second reactor 2. The residual reaction liquid collected by the second collection tank 17 is pressurized by the first delivery pump 14 and delivered to the second reactor 2 through the first pipeline 6. The second reactor 2 depolymerizes the residual polymer in the residual reaction liquid to obtain gas-phase monomer, which is output through the third outlet 202. The gas-phase monomer is then input into the first reactor 1 through the second pipeline 7 to wash the clay catalyst. The above-mentioned circulation loop is used to wash the clay catalyst in the first reactor 1 for multiple times. The first pipeline 7 is further provided with a first valve 11 for controlling the opening or closing of the second pipeline 7. During the circulation and washing of the clay catalyst, the first valve 11 is in an open state. After the washing is completed, the first valve 11 is closed.

[0127] After the washing of the clay catalyst is completed, the clay catalyst is unloaded from the second outlet 103 of the first reactor 1 and delivered to the calcining device 3. The calcining device 3 is a rotary kiln. The calcining device 3 includes an eighth inlet 303 and a fifth outlet 302. The eighth inlet 303 is used to introduce a gas containing N2O. The calcining device 3 is used to oxidize and decompose the clay catalyst. The final product is discharged from the fifth outlet 302 of the calcining device 3 to realize the regeneration of the clay catalyst.

[0128] After the washing of the clay catalyst is completed, the fourth outlet 105 of the first reactor 1 discharges the inert gas carrying the gas-phase monomers, the fourth outlet 105 is communicated with the inlet of the condenser 4, and a second valve 12 is further arranged between the first reactor 1 and the condenser 4, the second valve 12 is closed during the process of the circulating washing of the clay catalyst, and the second valve 12 is opened after the washing is completed. The inert gas carrying the gas-phase monomers is condensed by the condenser 4 to obtain monomer condensate, and the monomer condensate and the inert gas are discharged through the outlet of the condenser 4 into the first collecting tank 16, the first collecting tank 16 is provided with a gas discharge port 161, and the inert gas is discharged from the gas discharge port 161. The subsequent monomer condensate is transported to the monomer purification and recovery device 5 through the fourth pipeline 9, and the monomer purification and recovery device 5 is used for purifying the recovered monomer condensate. A second delivery pump 15 is further arranged between the first collecting tank 16 and the monomer purification and recovery device 5, and is used for pressurizing the monomer condensate.

[0129] The monomer purification and recovery device 5 further comprises a seventh inlet 502, the seventh inlet 502 is communicated with the third outlet 202 through a fifth pipeline 10, the fifth pipeline 10 is further provided with a third valve 13, the second reactor 2 is further provided with a liquid level controller 203, the liquid level controller 203 is electrically connected with the third valve 13, and is used for controlling the opening or closing of the third valve 13 based on the liquid level in the second reactor 2. During the process of the circulating washing of the clay catalyst, if the liquid level in the second reactor 2 exceeds the preset value, the third valve 13 is opened, and the excess monomers in the second reactor 2 are directly transported to the monomer purification and recovery device 5 through the fifth pipeline 10 for purification and recovery.

[0130] Example 2

[0131] In this example, only the pressure of the depolymerization reaction in step 2 is adjusted to 2.0 MPa, and the reaction temperature is 180°C, and the other operations are the same as in Example 1.

[0132] Example 3

[0133] In this example, only the depolymerization reaction temperature in step 2 is adjusted to 120°C, and the other operations are the same as in Example 1.

[0134] Comparative Example 1

[0135] The brand-new commercially available catalyst (Clariant K-306, main raw material montmorillonite) has not been subjected to catalytic reaction.

[0136] Comparative Example 2 (high-temperature calcination regeneration method)

[0137] The comparative example is based on example 1, only step 5 is adjusted to high temperature calcination method to treat the deactivated catalyst, specifically: the catalyst to be recovered is transported to a rotary kiln and air is introduced, heated at 750°C for 3h, and other operations are the same as example 1.

[0138] Effect example 1 catalyst pore distribution

[0139] The pore size distribution is analyzed by mercury intrusion method, specifically the method of ASTM D4284-07 is used, and the Autopore II9220 type mercury porosimeter is used for measurement, and the results are shown in the following table 2.

[0140] Table 2

[0141]

[0142] The test results show that the regenerated catalyst of example 1 shows uniform pore distribution, the pore size is mainly concentrated in the interval of 10-100nm, and the pore volume and pore size distribution characteristics are highly consistent with the fresh catalyst (comparative example 1). The pore volume of comparative example 2 (high temperature calcined catalyst) is significantly reduced, and the 10-100nm pore size ratio is significantly reduced, which is inferred to be due to the fact that the high temperature calcination process destroys the ordered microstructure of the catalyst, resulting in pore collapse and wide pore size distribution degradation.

[0143] Effect example 2 adsorption performance test

[0144] The regenerated catalysts obtained by treating examples 1-3 and comparative examples 1-2 are used for adsorption performance test of ammonia nitrogen removal rate.

[0145] The test method is as follows: 100mL ammonia nitrogen wastewater is taken and added to a 250mL conical flask, then 10g of regenerated catalyst is weighed and added to the above conical flask, and placed in a 25°C constant temperature water bath shaking box with a shaking speed of 100rpm for 1hr, and the ammonia nitrogen concentration of the solution is measured by Nash reagent colorimetry (GB7479.87). The adsorption rate V (%) is used to represent the adsorption capacity of the regenerated catalyst, v=(C o -C) / C o *100, C0 refers to the initial concentration of ammonia nitrogen wastewater, C0 is 100mg / L.

[0146] The test results are shown in the following table 3.

[0147] Table 3

[0148]

[0149] The test results show that the catalysts of Examples 1-3 all exhibit excellent ammonia-nitrogen adsorption performance, and the adsorption capacity even exceeds that of Comparative Example 1 (fresh catalyst). This indicates that the regeneration process effectively protects the crystal structure of the catalyst while optimizing its pore structure, thereby improving the adsorption efficiency. In sharp contrast, the adsorption performance of Comparative Example 2 (high-temperature calcined catalyst) is significantly lower than that of Examples 1-3, which further proves that high-temperature calcination can remove organic matter in the pores, but will irreversibly damage the porous structure of the catalyst.

[0150] Effect Example 3 Depolymerization reaction test

[0151] The regenerated catalysts obtained by treating Examples 1-3 and Comparative Examples 1-2 were used for depolymerization reaction tests.

[0152] The test method is as follows:

[0153] 1. Reaction steps

[0154] In a 500 mL reaction kettle, 300 g of commercially available polytetrahydrofuran (molecular weight ~ 1800) and 60 g of catalyst were added, the reaction kettle was tightly closed, airtight test was performed, and the reaction kettle was replaced with nitrogen three times. Set the reaction conditions: temperature 130℃, normal pressure, stirring rate 1000r / min, reaction time 1 hour. After the reaction was completed, the reaction system was cooled to room temperature. Sampling was performed for subsequent analysis.

[0155] Note: The entire reaction process must ensure that the system is sealed and leak-free.

[0156] 2. Depolymerization rate determination

[0157] The content of the polymer was separated using a rotary evaporator (BUCHI, R-490) with the following operation steps: about 100 g of the above cooled reaction liquid sample was weighed into a 500 mL rotary evaporator flask with a known mass, and was kept in an oil bath at 160℃ for 30 min under normal pressure. Then the vacuum pump was turned on, and the distillation was continued for 1 hour under 10 mbar. After cooling to room temperature, the rotary evaporator flask was removed, and the oil bath medium residue on the outside of the flask was carefully wiped off with filter paper. The total mass of the rotary evaporator flask and the residue inside was weighed, and the depolymerization rate was calculated according to the following formula: Depolymerization rate (wt%) = (A / E)*100%.

[0158] Wherein:

[0159] A: mass of residue after rotary evaporation (g)

[0160] E: initial mass of the sample (g)

[0161] 3. Distillate component analysis

[0162] The organic matter distilled by rotary evaporation was collected and analyzed using a gas chromatograph (Thermo Fisher Trace1310). Area normalization method was used to quantitatively analyze the content of each component.

[0163] The test results are shown in Table 4 below.

[0164] Table 4

[0165]

[0166] The test results show that Examples 1-3 all show high depolymerization rates, indicating that the regenerated catalysts maintain good activity in the polymer depolymerization reaction, and their performance is close to that of Comparative Example 1 (fresh catalyst), which is consistent with the aforementioned pore distribution results. In contrast, the depolymerization performance of Comparative Example 2 (high-temperature calcined catalyst) is significantly reduced, far lower than that of Examples 1-3 and Comparative Example 1, indicating that the high-temperature calcination process damages the catalyst activity.

[0167] Effect Example 4 Polymerization Reaction Test

[0168] The regenerated catalyst obtained by Example 1 and the brand new catalyst in Comparative Example 1 were respectively subjected to THF polymerization reaction test. The test method is as follows:

[0169] (1) Conversion rate

[0170] Take 21.6g of catalyst, 80g of THF monomer, and 3.5g of acetic anhydride, and place them in a reaction kettle. Tighten the kettle cover plate to ensure airtightness. Replace with nitrogen, repeat the pressure rise and pressure drop 3 times, and then keep the pressure of the reaction kettle at 3MPa. Place the reaction kettle in a 36℃ constant temperature water bath, stir at 300rpm, and continue to react for 24h. After the reaction is completed, use a centrifuge to separate the catalyst from the reaction liquid. Take the supernatant to an oil bath at 95℃ for rotary evaporation, and measure the conversion rate.

[0171] Among them, the polymer conversion rate = the mass of the polymer in the reaction liquid / the total amount of raw materials x 100%.

[0172] The mass of the polymer is the weight of the polymer obtained after rotary evaporation at -80kPaG and 130℃. The rotary evaporator is Buchi Rotavapor R215, and the vacuum pump is VACUUBRAND GMBH +CO KG MD 1C +AK +EK.

[0173] (2) Unreacted acetic anhydride

[0174] The potentiometric titrator (Methrom 794 with 20 ml exchange unit) was used according to the following procedure: 10.000 g of sample was accurately weighed into a 250 ml conical flask, 50.0 ml of isopropanol was added and mixed well until the sample was completely dissolved. The titration was performed with 0.1000 M KOH / isopropanol solution until the solution changed from colorless to a stable red color. The titration was performed as follows: blank group: 1 ml was added before titration only; sample group: three additions of indicator: 1.0 ml before titration, 1.0 ml at about 2 / 3 of the titration, and 0.5 ml near the end point.

[0175] The following formula was used for the calculation:

[0176] 1) Acid value

[0177]

[0178] wherein,

[0179] P: volume of KOH solution consumed by the sample group in mL

[0180] B: volume of KOH solution consumed by the blank group in mL

[0181] N: concentration of KOH solution in mol / L

[0182] E: weight of the sample in g

[0183] 2) Unreacted acetic anhydride

[0184]

[0185] (3) Color

[0186] The color number was determined using a British Lovibond full-automatic colorimeter PFX195, and the color value was based on the platinum-cobalt standard according to ASTM D1209.

[0187] (4) Viscosity

[0188] The method for measuring viscosity (Visco) was the Ubbelohde viscometer method, which obtained the viscosity by measuring the time required for a certain volume of liquid to flow through a capillary tube of a certain length and radius. The viscometer tube was clamped in a constant-temperature water bath at 50 ± 0.01 °C, and after 20 min, the sample to be tested was sucked into the tube from port A to 2-3 mm above the graduation C. When the liquid flowed through graduation C, the time t (s) required for the liquid to flow from graduation C to graduation E was recorded. Visco (50 °C) = time s x K (viscometer constant) x specific gravity.

[0189] (5) Molecular weight

[0190] The determination of the molecular weight was obtained by titration of the number of ester functions according to the method ASTM D94-07 (2017); the titrator was an automatic potentiometer T7 by Mettler Toledo.

[0191] (6) Molecular weight distribution index

[0192] The molecular weight distribution index was measured by Agilent 1260 Infinity II Gel Permeation Chromatograph (GPC) with THF as the mobile phase.

[0193] The test results are shown in Table 5 below.

[0194] Table 5

[0195]

[0196] From the above table, the conversion rates and performances of the two are close, and even the conversion rate of the regenerated catalyst of Example 1 is better than that of the fresh catalyst of Comparative Example 1, which shows that the regeneration method of the present application has a significant effect.

Claims

1. A method for regenerating a clay catalyst, characterized by, It comprises the following steps: Step 1: pressurized separation of the clay catalyst and the residual reaction liquid on the surface of the clay catalyst to obtain a first separation product and a residual reaction liquid; the residual reaction liquid comprises residual polymer; the clay catalyst is selected from one or more of sodium-based montmorillonite, calcium-based montmorillonite, kaolin, bentonite and halloysite; the residual polymer is polytetrahydrofuran; Step 2: heating the residual reaction liquid to perform a depolymerization reaction under the action of a depolymerization catalyst to obtain a gaseous monomer; the temperature of the depolymerization reaction is 160±5℃ and the pressure is 0.8MPa, or the temperature is 180℃ and the pressure is 2.0MPa, or the temperature is 120℃ and the pressure is 0.8MPa; the monomer is tetrahydrofuran; Step 3: heating the first separation product to perform a depolymerization reaction on the residual reaction liquid in the first separation product to obtain a second separation product and a liquid monomer; the gaseous monomer after condensation is in contact with the second separation product for washing to separate a third separation product and a washing liquid; the heat source of the heating is derived from the condensation heat of the gaseous monomer generated in step 2, and the temperature of the depolymerization reaction is 160±5℃ and the pressure is 0.75MPa; Step 4: purging the third separation product to obtain a clay catalyst and a gaseous component; Step 5: using a gas containing N2O to perform oxidative decomposition on the clay catalyst obtained in step 4; the temperature of the oxidative decomposition is 300-600℃.

2. The method for regenerating a clay catalyst according to claim 1, characterized by, The regeneration method satisfies one or more of the following conditions: (a) in step 1, the pressurized separation is performed by introducing an inert atmosphere; (b) in step 1, the residual reaction liquid further comprises unreacted monomer and / or organic impurities; (c) in step 2, the depolymerization catalyst is selected from a clay catalyst.

3. The method for regenerating a clay catalyst according to claim 2, characterized in that, The regeneration method satisfies one or more of the following conditions: (a) in step 1, the inert atmosphere is nitrogen; (b) in step 2, the depolymerization catalyst is selected from a new clay catalyst or a regenerated clay catalyst.

4. The method for regenerating a clay catalyst according to claim 1, characterized by, The regeneration method satisfies one or more of the following conditions: (a) after step 3 and before step 4, further comprising a step of judging whether the clay catalyst has completely recovered fluidity; if not, steps 2 to 3 are repeated in sequence until the fluidity is completely recovered; if so, step 4 is performed; (b) in step 4, the purging is performed by a hot nitrogen stripping method; (c) in step 4, after purging the third separation product, further comprising an operation of monomer purification and recovery of the gaseous component.

5. The method for regenerating a clay catalyst according to claim 4, characterized in that, The regeneration method satisfies one or more of the following conditions: (a) after step 3 and before step 4, whether the clay catalyst has completely recovered fluidity is judged according to the size of the angle of repose; when the angle of repose is ≤45°, it indicates that the clay catalyst has completely recovered fluidity; (b) in step 3, the washing liquid can also be used for monomer purification and recovery; (c) in the hot nitrogen stripping method in step 4, the temperature of the hot nitrogen is 150-180℃; (d) in the hot nitrogen stripping method in step 4, the system pressure is 0.1-0.5MPa; (e) in step 4, the heating nitrogen stripping method is terminated when the monomer content in the heating nitrogen is less than 500 ppm; (f) in step 4, the monomer is recovered by distillation.

6. The method for regenerating a clay catalyst according to claim 1, wherein The regeneration method satisfies one or more of the following conditions: (a) in step 5, the N2O-containing gas is pure N2O or a mixture of N2O and air, and when the N2O-containing gas is a mixture of N2O and air, the molar ratio of N2O to air is 1:(1-1000); (b) in step 5, the total volume space velocity of the N2O-containing gas is 50-2000 hr -1 ; (c) in step 5, the temperature of the oxidative decomposition is 300-550℃; (d) in step 5, the time of the oxidative decomposition is 1-12h.

7. The method of regenerating a clay catalyst according to Claim 1, wherein, The regeneration method is carried out using the following regeneration system: The regeneration system comprises a first reactor, a second reactor and a calcination device; The internal space of the first reactor is used to load the clay catalyst to be regenerated, and the first reactor further comprises a first inlet, a first outlet, a second outlet and a fourth inlet, the fourth inlet is used to introduce inert gas; the second reactor comprises a second inlet and a third outlet; the calcination device comprises a third inlet, and the calcination device is used to oxidatively decompose the clay catalyst; The first outlet is in communication with the second inlet through a first pipeline, and the first outlet is used to transport the residual reaction liquid separated by pressurization in step 1 in the first reactor or the washing liquid generated in step 3 into the first pipeline; the second reactor is used to depolymerize the residual polymer in the residual reaction liquid or the washing liquid to obtain a gas-phase monomer, which is output from the third outlet, and the first inlet is used to introduce the gas-phase monomer into the first reactor to wash the first separation product or the second separation product in the first reactor; The second outlet is in communication with the third inlet through a third pipeline, and the second outlet is used to discharge the separated clay catalyst into the third pipeline; The third outlet is in communication with the first inlet through a second pipeline.

8. The method for regenerating a clay catalyst according to claim 7, characterized by, The regeneration system satisfies one or more of the following conditions: (a) the first reactor further comprises a fourth outlet, the first inlet and the fourth inlet are located in the upper part of the first reactor, the first outlet and the second outlet are located in the bottom of the first reactor, and the fourth outlet is located in the top of the first reactor, and the fourth outlet is used to discharge the inert gas carrying the gas-phase monomer; (b) the first reactor further comprises a fifth inlet, the fifth inlet is arranged in the lower part of the first reactor, and the fifth inlet is used to introduce inert gas; (c) the regeneration system further comprises a first conveying pump, the first conveying pump is arranged on the first pipeline, and the first conveying pump is used to pressurize the residual reaction liquid or the washing liquid in the first pipeline to make the residual reaction liquid or the washing liquid enter the second reactor; (d) the regeneration system further comprises a second collecting tank, which is arranged on the first pipeline, the inlet and outlet of the second collecting tank are both communicated with the first pipeline, and the second collecting tank is used for collecting the residual reaction liquid or the washing liquid.

9. A regenerated clay catalyst characterized by, The regenerated clay catalyst is obtained by the regeneration method according to any one of claims 1-8.

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