Process for the regeneration of a catalyst for the dehydrogenation of alkanes to alkenes

Abstract

The present application relates to the field of catalyst regeneration, and discloses a regeneration method of an alkane dehydrogenation olefin catalyst, which comprises the following steps: (1) performing first charring of the catalyst to be regenerated in the charring zone of a first regenerator; (2) performing second charring of the product obtained in step (1) in the charring zone of a second regenerator to obtain the regenerated catalyst; wherein the pressure in the charring zone of the second regenerator is 0.01-0.3 MPa higher than that in the charring zone of the first regenerator. The method improves the catalyst regeneration efficiency, solves the problem of activity reduction caused by the difficulty in removing the coke deposited on the catalyst, and prolongs the operation cycle of the device.

Description

Technical Field

[0001] This invention relates to the field of catalyst regeneration, and more specifically to a method for regenerating a catalyst for alkane dehydrogenation to olefins. Background Technology

[0002] Propylene is an important organic chemical raw material used to produce polypropylene, acrylonitrile, butanol, octanol, propylene oxide, isopropanol, and other products. Traditionally, propylene is mainly derived from a byproduct of ethylene production via steam cracking, while isobutylene is almost entirely obtained from refinery gas and C4 fractions from cracking. With the increasing demand for propylene and isobutylene from the petrochemical industry, traditional sources cannot meet market demand. The maturity of shale gas extraction technology has provided the market with a large quantity of high-quality, inexpensive propane and butane. The process of direct catalytic dehydrogenation of alkanes to produce propylene and isobutylene is gaining increasing market acceptance due to its economic and environmentally friendly nature. The dehydrogenation process of low-carbon alkanes to produce low-carbon olefins is mainly divided into moving bed and fixed bed processes. The fixed bed process has a relatively simple reaction system design, but frequent catalyst regeneration and switching operations place high demands on the control system, valves, and equipment. The moving bed process can achieve continuous catalyst regeneration and circulation, maintaining the catalyst in a high-activity state, significantly improving catalyst activity and ensuring propylene yield.

[0003] In existing moving bed dehydrogenation plants for low-carbon alkane, the "core coke" phenomenon is highly likely to occur, meaning that coke deposits deep within the catalyst channels cannot be completely removed during the coking process. This is partly because the coke deposits on the dehydrogenation catalyst are deep dehydrogenation products with a low H / C ratio, making them more difficult to remove; and partly because oxygen molecules have difficulty penetrating deep into the channels during catalyst regeneration, hindering the removal of these deep-seated coke deposits. Research shows that increasing the regeneration oxygen partial pressure can effectively improve the oxygen molecule diffusion rate, facilitating oxygen molecules to penetrate deeper into the channels and thus accelerating the catalyst decoking rate. However, excessively high oxygen content can easily cause overheating during regeneration, which is detrimental to plant operation. Therefore, the most effective method is to increase the regeneration pressure.

[0004] However, catalyst coking produces a certain amount of water during combustion. Under high-pressure regeneration conditions, the water pressure also increases accordingly. Prolonged exposure to high temperature and high water content will severely damage the catalyst's pore structure and affect its performance. Therefore, it is necessary to remove water from the regeneration circulating flue gas. However, the process of removing water also removes chlorine from the circulating flue gas, making it difficult to inhibit metal aggregation on the catalyst surface under high temperature and low chlorine conditions. This will also affect the subsequent chlorine replenishment and metal redispersion effects.

[0005] CN112569872A discloses a moving bed system for the dehydrogenation of low-carbon alkanes to produce low-carbon olefins. The technical solution includes: a raw material pretreatment unit, a fuel separation unit, a moving bed reaction unit, a hydrogen separation unit, a product purification unit, a product separation and purification unit, and a catalyst regeneration unit, connected sequentially by pipelines; the moving bed reaction unit includes several parallel reaction pipelines, on which a heating furnace and a reactor are installed.

[0006] CN1100852C discloses a method and equipment for regenerating a hydrocarbon conversion catalyst. The catalyst to be generated passes through the coking zone, oxychlorination zone, pre-drying zone and calcination zone of the regenerator from top to bottom. The added pre-drying zone can use the regeneration circulating gas after dechlorination and drying to pre-dry the catalyst after oxychlorination, thereby reducing the amount of drying gas used in the calcination zone. The amount of oxygen-containing gas entering the calcination zone is determined by the amount of oxygen required for coking. All the gas entering the calcination zone can enter the oxychlorination zone and then enter the regeneration gas circulation loop to supply oxygen for coking. This ensures that there is no excess oxygen-containing gas venting from the calcination zone of the regenerator, thereby eliminating the need for purification measures for the vented gas in the calcination zone.

[0007] CN110452085A discloses a countercurrent moving bed C3 / C4 alkane dehydrogenation process, in which the catalyst flows in the opposite direction to the reactant stream between reactors. The method includes a mixed hydrogen and C3 / C4 alkane feed stream passing through a combined heat exchanger and a furnace, entering the first-stage reactor, and then sequentially flowing through the second and final-stage reactors to form the reactant stream. The catalyst is regenerated in a regenerator and enters the final-stage reactor, then sequentially flowing through the second and first-stage reactors to form the catalyst feed stream. Each reactor outlet is equipped with a hydrogen permeation membrane separator. Compared with existing industrialized propane dehydrogenation processes, this method can improve the single-pass conversion rate of C3 / C4 alkanes, reduce the reaction temperature, improve selectivity, save energy, reduce carbon buildup on the catalyst, extend catalyst life, and reduce equipment investment.

[0008] US9302261B2 discloses a method for supplying cooling gas to a CCR cooling zone and preventing condensation in the cooler. The method involves heating a portion of the airflow from the cooler blower using regenerated circulating gas through a heat exchanger, then mixing the heated airflow with the incoming airflow to ensure the temperature of the cooling airflow entering the cooler is not lower than 4°C, and then cooling the cooling gas. The cooling gas entering the cooling zone is heated and dry gas, which is a mixture of air and nitrogen.

[0009] CN105498858B discloses a method for regenerating a continuous reforming catalyst. The method involves feeding the reacted catalyst into a regenerator, which then sequentially passes through a coking zone, an oxychlorination zone, and a roasting zone. A portion of the regeneration gas discharged from the coking zone is directly injected into the oxychlorination zone. A chlorine-containing compound is injected into the gas stream at the inlet of the coking zone, with the amount of chlorine injected being 0.01-0.2% of the catalyst's circulating volume (based on elemental chlorine). This method can improve the catalyst regeneration effect and reduce the amount of chlorine injected during the regeneration process.

[0010] While the above technologies have made some progress in optimizing dehydrogenation catalysts and processes for low-carbon alkane, how to effectively solve the problem of catalyst activity decline caused by "core coke" is a technical problem that urgently needs to be solved. Summary of the Invention

[0011] The purpose of this invention is to overcome the problems in the prior art, such as the difficulty in replenishing chlorine to the catalyst and the poor effect of subsequent metal redispersion caused by the imbalance of water and chlorine in the circulating flue gas in the high-pressure regeneration process, and the problem of "core coke" caused by the difficulty of oxygen molecules entering the deep pores of the catalyst in the low-pressure regeneration process. This invention provides a regeneration method for alkane dehydrogenation to olefins catalyst. This method improves the catalyst regeneration efficiency, solves the problem of activity decline caused by the difficulty in removing catalyst coke, and extends the operation cycle of the unit.

[0012] To achieve the above objectives, the present invention provides a method for regenerating an alkane dehydrogenation catalyst for olefin production, the method comprising the following steps:

[0013] (1) The catalyst to be generated is first coked in the coking zone of the first regenerator;

[0014] (2) The product obtained in step (1) is subjected to a second coking in the coking zone of the second regenerator to obtain the regenerated catalyst;

[0015] The pressure in the coking zone of the second regenerator is 0.01-0.3 MPa higher than that in the coking zone of the first regenerator.

[0016] Preferably, the dew point of the regenerated gas in the coking zone of the second regenerator is ≤-50℃, and more preferably ≤-60℃.

[0017] Preferably, the Cl2 content in the regenerated gas from the first coke burner is 1-500 vppm, more preferably 100-300 vppm.

[0018] Preferably, the HCl content in the regenerated gas from the second coke burner is ≤0.5vppm.

[0019] The beneficial effects achieved through the above technical solution are as follows:

[0020] (1) The regeneration method provided by the present invention optimizes the regeneration system, overcomes the problems existing in high-pressure and low-pressure regeneration systems, improves the conversion rate of low-carbon alkanes and the catalyst regeneration efficiency, and realizes continuous catalyst circulation;

[0021] (2) In this invention, preferably, the introduction of chloride or chlorine gas into the coking zone of the first regenerator with lower pressure can effectively alleviate the chlorine loss and metal accumulation of the catalyst during the coking process, which is beneficial to the subsequent metal redispersion process; in the coking zone of the second regenerator with higher pressure, the oxygen partial pressure is effectively increased, the coking rate of the catalyst is accelerated, and the problem of "core coke" caused by the difficulty of oxygen molecules entering the deep pores of the catalyst is effectively solved. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the low-carbon alkane dehydrogenation process of the method of the present invention;

[0023] Figure 2 This is a schematic diagram of the catalyst regeneration process of the method of the present invention.

[0024] Explanation of reference numerals in the attached figures

[0025] Figure 1

[0026] I - First Reactor II - Second Reactor III - Third Reactor

[0027] IV - Fourth Reactor 101 / 102 / 103 / 104 / 105 - Pipeline 110 - Heating Furnace

[0028] 121 - Upper part of the first reactor I; 122 / 125 / 128 / 132 / 144 - Lifting; 123 / 126 / 129 / 133 / 145 - Lifting of the reduction tank lifter riser pipeline. 124 - Upper part of the second reactor II; 127 - Upper part of the third reactor III; 130 - Upper part of the fourth reactor IV, hopper hopper hopper.

[0029] 131-1 Locked Hopper, 141-Catalyst Separation Hopper, 142-Flow Control Zone

[0030] 143 - Gas Isolation Zone 200 - No. 2 Locking Hopper 300 - First Regenerator 301 - Second Regenerator

[0031] Figure 2

[0032] 201 - High-pressure zone replenishment gas; 202 - High-pressure zone external exhaust gas; 203 - Balance zone regulating gas. 204 - Low-pressure air vent; 205 - No. 2 lock hopper external vent.

[0033] 302 - Coking in the first regenerator; 303 - Coking in the second regenerator; 304 - Cooling transition zone.

[0034] 305 - Oxychlorination zone; 306 - Drying zone; 311 / 314 / 315 / 320 - Electric heaters 312 / 317 - Fan; 313 - First coke burner regeneration gas; 316 - Dryer and dechlorinator cooling.

[0035] 318 - Second coke regeneration gas air supply; 319 - Cooler; 321 / 322 / 323 / 324 / 326 / 327 Cooler; 328 / 329 / 330 / 331 / 332 / 334 / 337 / 340 - Piping 341 / 342 / 343 - Oxygen-containing gas; 325 / 336 - Chlorine-containing gas; 333 - Cooling transition zone gas. 335 / 339 - Mixed Gas 350 - Partition Detailed Implementation

[0036] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0037] This invention provides a method for regenerating a catalyst for alkane dehydrogenation to olefins, the method comprising the following steps:

[0038] (1) The catalyst to be generated is first coked in the coking zone of the first regenerator;

[0039] (2) The product obtained in step (1) is subjected to a second coking in the coking zone of the second regenerator to obtain the regenerated catalyst;

[0040] The pressure in the coking zone of the second regenerator is 0.01-0.3 MPa higher than that in the coking zone of the first regenerator.

[0041] In this invention, by optimizing the regeneration system, a first regenerator and a second regenerator are set up. The pressure of the coking zone in the second regenerator is adjusted to be higher than that in the first regenerator. The coking zone in the first regenerator is a low-pressure, low-oxygen, humid and hot environment. This removes most of the carbon deposits while inhibiting chlorine loss and metal accumulation in the catalyst. This avoids the problems of difficulty in replenishing chlorine in the catalyst and poor subsequent metal redispersion caused by the imbalance of water and chlorine in the circulating flue gas during the high-pressure regeneration process.

[0042] In this invention, preferably, the dew point of the regeneration gas in the coking zone of the first regenerator is greater than 0°C.

[0043] In this invention, the spent catalyst after the first coking process enters the second regenerator via pressure transformation. The method of pressure transformation is not particularly limited; those skilled in the art can control the pressure in the coking zone of the second regenerator to be 0.01-0.3 MPa higher than the pressure in the coking zone of the first regenerator. According to a preferred embodiment of the invention, the pressure transformation is performed in a closed hopper.

[0044] Compared with existing low-pressure regeneration processes and high-pressure regeneration processes used in continuous reforming, the regeneration method provided in this invention improves the conversion rate of low-carbon alkanes and the catalyst regeneration efficiency, realizes continuous catalyst circulation, solves the problem of activity decline caused by the difficulty in removing catalyst coke, and extends the operating cycle of the unit.

[0045] According to the present invention, preferably, the pressure in the coking zone of the second regenerator is 0.15-0.3 MPa higher than that in the coking zone of the first regenerator. In this invention, the coking zone of the second regenerator is a high-pressure, high-oxygen, dry, and cold environment, which can accelerate the removal of carbon deposits within the catalyst channels and effectively solve the "core coke" problem. In this invention, the "core coke" refers to the phenomenon of incomplete coking in the low-pressure regeneration process because oxygen molecules have difficulty penetrating deep into the catalyst channels.

[0046] The term "regenerated catalyst" as used in this invention has the conventional meaning in the art, and this invention does not particularly limit it. Any catalyst whose reaction performance is lower than that of a fresh catalyst can be used as a regenerated catalyst. For example, it can be a catalyst whose reaction activity or selectivity does not meet requirements and needs to be regenerated.

[0047] The spent catalyst described in this invention can be a spent catalyst in different catalytic fields, preferably a spent catalyst obtained from the dehydrogenation reaction of low-carbon alkanes.

[0048] According to the present invention, preferably, the catalyst to be generated includes a support, an active component, and carbon.

[0049] According to the present invention, preferably, the carbon content of the catalyst to be generated is 1-5% by mass, more preferably 1-3% by mass, based on the total amount of the support and active components.

[0050] According to the present invention, preferably, the carrier is selected from at least one of alumina, silicon oxide and zirconium oxide, preferably alumina, and more preferably θ-alumina.

[0051] According to the present invention, preferably, the active component comprises platinum group metals, group IVA metals, alkali metals and chlorine.

[0052] According to the present invention, preferably, the platinum group metal is platinum and / or palladium, and more preferably platinum.

[0053] According to the present invention, preferably, the IVA group metal is selected from at least one of silicon, germanium and tin, and preferably tin.

[0054] According to the present invention, preferably, the alkali metal is selected from at least one of potassium, sodium and rubidium, and more preferably potassium.

[0055] According to the present invention, preferably, based on the total amount of the carrier, the content of the platinum group metals is 0.1-1% by mass; the content of the group IVA metals is 0.1-1% by mass; the content of the alkali metals is 0.5-2% by mass; and the content of chlorine is 0.4-2% by mass.

[0056] In this invention, preferably, the platinum group metal is platinum, and the content of the platinum group metal is 0.1-1% by mass, based on the total amount of the carrier.

[0057] In this invention, preferably, the Group IVA metal is tin, and the content of the Group IVA metal is 0.1-1% by mass, based on the total amount of the carrier.

[0058] In this invention, preferably, the alkali metal is potassium, and the content of the alkali metal is 0.5-2% by mass, based on the total amount of the carrier.

[0059] In this invention, preferably, the chlorine content is 0.5-1.5% by mass, based on the total amount of the carrier.

[0060] The method provided by this invention is particularly suitable for the regeneration of the above-mentioned catalyst. By using the method provided by this invention to regenerate the above-mentioned catalyst, the regenerated catalyst has the characteristics of high conversion rate and high selectivity. The method of this invention improves the conversion rate of low-carbon alkanes and the catalyst regeneration efficiency, and effectively solves the problem of catalyst activity decline caused by incomplete coking.

[0061] According to the present invention, preferably, the dew point of the regeneration gas in the coke burning zone of the second regenerator is ≤-50℃, and more preferably ≤-60℃. Controlling the dew point of the regeneration gas to meet the above conditions can reduce the influence of water molecules on the regeneration of the catalyst, and reduce the aggregation of catalyst metal grains and rapid loss of specific surface area caused by excessive water content.

[0062] In this invention, preferably, the pressure of the second coke burner is higher than that of the first coke burner, the inlet temperature of the regeneration gas of the second coke burner is higher than that of the regeneration gas of the first coke burner, and the oxygen content in the regeneration gas of the second coke burner is higher than that in the regeneration gas of the first coke burner.

[0063] According to the present invention, preferably, the first coking conditions include: a regeneration gas inlet temperature of 450-550°C, more preferably 460-500°C; a pressure of 0.001-0.1 MPa, more preferably 0.01-0.1 MPa; an oxygen content in the regeneration gas of 0.1-1.2 v%, more preferably 0.8-1.2 v%; a gas-solvent volume ratio of 1000-10000, more preferably 2000-5000; and a residence time of 1-5 hours, more preferably 2-4 hours.

[0064] In this invention, the first coking under the above conditions can remove most of the carbon deposits on the outer surface and external pores of the catalyst.

[0065] In this invention, the coking zone of the first regenerator generates recirculated gas, which can be discharged from the system or recycled back to the coking zone of the first regenerator for use. According to the invention, preferably, the method further includes: partially discharging the recirculated gas generated in the coking zone of the first regenerator from the system, and partially returning it to the coking zone of the first regenerator after heat exchange, supplemented with chlorinating agent gas and oxygen-containing gas. In this preferred embodiment, the recirculated gas generated in the coking zone of the first regenerator, after being supplemented with chlorinating agent gas and oxygen-containing gas, provides at least a portion of the first regeneration gas.

[0066] In this invention, a chlorinating agent-containing gas is introduced into the coking zone of the first regenerator, where the pressure is relatively low. This effectively mitigates chlorine loss and metal accumulation in the catalyst during the coking process, which is beneficial for the subsequent metal redispersion process.

[0067] According to the present invention, preferably, the chlorinating agent is Cl2 and / or an organochloride.

[0068] In this invention, the amount of Cl added to the coke-burning zone of the first regenerator is not particularly limited, as long as the Cl2 content in the regenerator of the first coke-burning is 1-500 vppm. Preferably, the amount of Cl added to the coke-burning zone of the first regenerator is 0.01-0.2% of the flow rate of the catalyst to be generated. The amount of Cl added to the coke-burning zone of the first regenerator is the amount of Cl additionally added through the chlorination agent gas.

[0069] In this invention, the flow rate of the catalyst to be generated can be adaptively adjusted by those skilled in the art based on the reaction conditions.

[0070] According to the present invention, preferably, the Cl2 content in the regeneration gas of the first coke burner is 1-500 vppm, more preferably 100-300 vppm. The Cl2 content in the regeneration gas of the first coke burner refers to the Cl2 content in the coke burner zone of the first regenerator during the first coke burner process. Using the aforementioned regeneration gas of the first coke burner for the first coke burner can effectively remove carbon deposits from the outer surface and external pores of the catalyst, while mitigating the phenomenon of metal accumulation during catalyst regeneration.

[0071] According to the present invention, preferably, the second coking conditions include: a regeneration gas inlet temperature of 500-600°C, preferably 520-560°C; a pressure of 0.06-0.3 MPa, preferably 0.1-0.3 MPa; an oxygen content of 1.2-5 vol%, preferably 2-4 vol% in the regeneration gas; a gas-solvent volume ratio of 1000-10000, preferably 3000-6000; and a residence time of 1-5 hours, preferably 2-4 hours.

[0072] In this invention, the second coking under the above conditions can effectively remove carbon deposits deep within the catalyst pores.

[0073] According to the present invention, preferably, the HCl content in the regeneration gas of the second coke is ≤0.5vppm. Controlling the HCl content in the regeneration gas of the second coke to ≤0.5vppm can effectively control the chlorine content of the catalyst and avoid the increased acidity of the catalyst and the increase of side reactions due to the high chlorine content of the catalyst.

[0074] According to the present invention, preferably, the method further includes: partially discharging the circulating gas generated in the coking zone of the second regenerator from the system, and partially returning it to the coking zone of the second regenerator after heat exchange, dechlorination, drying, and replenishment with oxygen-containing gas.

[0075] In this invention, the second regenerator includes a coking zone, a cooling transition zone, an oxychlorination zone, and a drying zone. The operating conditions of each zone are not particularly limited, and those skilled in the art can make adaptive adjustments based on the catalyst regeneration situation in the second regenerator. Preferably, the temperature of the cooling transition zone is 200-480°C, the temperature of the oxychlorination zone is 120-600°C, and the temperature of the drying zone is 120-600°C.

[0076] In this invention, preferably, a portion of the circulating gas generated in the coking zone of the second regenerator is cooled to 350-460°C by a cooler and then enters the cooling transition zone.

[0077] In this invention, preferably, oxygen-containing gas is added to the coking zone of the second regenerator. The coking zone of the second regenerator has a high pressure, and adding oxygen-containing gas can effectively increase the oxygen partial pressure, accelerate the coking rate of the catalyst, and remove the hard-to-burn carbon deposits in the pores of the catalyst to be regenerated, thereby effectively solving the "core coke" problem caused by the difficulty of oxygen molecules entering the depths of the catalyst pores.

[0078] According to a preferred embodiment of the present invention, the second coked catalyst is cooled, oxychlorinated, and dried.

[0079] According to a preferred embodiment of the present invention, the cooling is carried out in a cooling transition zone. After cooling, the catalyst enters an oxychlorination zone where it is oxychlorinated using a chlorinating agent gas. A high-temperature mixed gas is used to adjust the redispersion properties of the platinum group metals in the catalyst. The mixed gas includes an oxygen-containing gas and a protective gas, preferably air and nitrogen. The temperature of the mixed gas is 400-600°C.

[0080] In this invention, preferably, the drying of the spent catalyst is carried out in a drying zone. The drying zone removes moisture generated from the second coking process to ensure the good performance of the spent catalyst.

[0081] In this invention, the regenerated catalyst obtained by the regeneration method provided by this invention has better performance.

[0082] According to the present invention, preferably, the method further includes contacting the regenerated catalyst with low-carbon alkanes to carry out a dehydrogenation reaction.

[0083] The present invention does not particularly limit the type of reactor used for the dehydrogenation reaction, and can use various reactors conventionally used in the art.

[0084] In this invention, preferably, the regenerated catalyst is reduced from an oxidized state catalyst to a reduced state catalyst before undergoing a dehydrogenation reaction.

[0085] According to a preferred embodiment of the present invention, the dehydrogenation reaction is carried out in a moving bed reaction zone. Preferably, the moving bed reaction zone includes at least two radial moving bed reactors connected in series, more preferably four to five radial moving bed reactors connected in series, and a heater is provided in front of each reactor. Preferably, the regenerated catalyst first enters a gas isolation zone, where the oxygen environment is converted into a hydrogen environment. The catalyst is then lifted by a booster to the upper reduction tank of the first reactor I. In the upper reduction tank of the first reactor I, the oxidized catalyst is reduced to a reduced catalyst and enters the first reactor I to participate in the dehydrogenation reaction, completing the catalyst circulation, regeneration, and reduction.

[0086] According to the present invention, preferably, the products of the dehydrogenation reaction include at least one of hydrogen, alkanes, and olefins.

[0087] According to the present invention, preferably, the low-carbon alkane is a C2-C4 alkane. Preferably, the content of C3 alkanes in the low-carbon alkane is greater than 95% by volume. The low-carbon alkane is derived from at least one of refinery by-products, shale gas, and associated gas from oil fields.

[0088] In this invention, the conditions for the dehydrogenation reaction can be adapted by those skilled in the art to meet the needs of the dehydrogenation reaction. According to a preferred embodiment of this invention, the conditions for the dehydrogenation reaction include: a temperature of 550-700℃, preferably 600-650℃; a pressure of 0.01-0.5 MPa, preferably 0.01-0.2 MPa; a hydrogen-to-hydrocarbon volume ratio of 0.2-2, preferably 0.4-0.7; and a mass hourly space velocity (HHSV) of 0.1-10 h⁻¹. -1 Preferably 0.3-4h -1 .

[0089] According to a preferred embodiment of the present invention, the spent catalyst generated from the dehydrogenation reaction flows out from the bottom of the fourth reactor, and dust in the catalyst is separated from the catalyst in a catalyst separation hopper. At the top of the catalyst separation hopper, purging gas from a dust removal fan blows a small amount of dust from the spent catalyst out from the top of the hopper to a dust collector for separation of dust and purging gas. The separated purging gas is then pressurized and recycled. The purified spent catalyst enters the pressure transformation and flow control zone under gravity, completing the pressure transformation from the low-pressure reactor to the high-pressure regenerator, and then enters the first regenerator from the top.

[0090] According to a preferred embodiment of the present invention, the low-carbon alkane dehydrogenation process is as follows: Figure 1 As shown, the regeneration process of the spent catalyst is as follows: Figure 2 As shown. After heat exchange, low-carbon alkanes enter the heater 110 via pipeline 101 for heating, and then enter the first reactor I for dehydrogenation. The effluent from the first reactor I enters the heater 110 via pipeline 102 for heating, and then enters the second reactor II. The effluent from the second reactor II enters the heater 110 via pipeline 103 for heating, and then enters the third reactor III. The effluent from the third reactor III enters the heater 110 via pipeline 104 for heating, and then enters the fourth reactor IV. The product from the fourth reactor IV enters the product fractionation system via pipeline 105 for separation. Part of the hydrogen separated by fractionation is discharged as product, and part is recycled back to the reaction zone as circulating hydrogen; olefins are discharged as product; unconverted alkanes are returned to the reaction zone for reprocessing.

[0091] According to a preferred embodiment of the present invention, the regenerated catalyst is reduced to a reduced state in the reduction tank 121 at the top of the first reactor I, and enters the first reactor I to participate in the dehydrogenation reaction. It is then lifted by the elevator 122 and the lift line 123 to the upper hopper 124 of the second reactor II, and enters the second reactor II. The catalyst then sequentially passes through the elevator 125, the lift line 126, the upper hopper 127 of the third reactor III, the third reactor III, the elevator 128, the lift line 129, the upper hopper 130 of the fourth reactor IV, and finally the fourth reactor IV. The spent catalyst flows out from the bottom of the fourth reactor IV, passes through the catalyst collector (not shown), and enters the catalyst separation hopper 141 via the No. 1 lock hopper 131, the elevator 132, and the lift line 133. After passing through the flow control zone 142, it enters the first regenerator 300.

[0092] According to a preferred embodiment of the present invention, such as Figure 2 As shown, the catalyst to be generated undergoes a first coking process in the coking zone 302 of the first regenerator. The circulating gas in the coking zone 302 of the first regenerator is discharged through pipeline 321, a small portion is discharged from the system through pipeline 322, and the remainder enters the blower 312. After heat exchange by the first coking regeneration gas air cooler 313, it is fully mixed with the supplemented oxygen-containing gas 343 through pipeline 324 and chlorination-containing gas 325, and sent to the electric heater 311. The outlet temperature of the electric heater 311 is controlled at 400-600℃, and it is returned to the inlet of the coking zone 302 of the first regenerator through pipeline 326.

[0093] After the first coking process, the spent catalyst enters the No. 2 closed hopper 200 for pressurization. The discharged low-pressure gas 204 is partially discharged as the No. 2 closed hopper exhaust gas 205, and partially returned to the No. 2 closed hopper 200 as the balance zone regulating gas 203. It is then introduced into the high-pressure zone supplementary gas 201 for further pressurization, and discharged as the high-pressure zone exhaust gas 202. After pressurization, it enters the second regenerator 301. The spent catalyst passes from top to bottom through the partition 350, the coking zone 303 of the second regenerator, the cooling transition zone 304, the oxychlorination zone 305, and the drying zone 306. Secondary coking occurs in the coking zone 303 of the second regenerator. The circulating gas from the coking zone 303 of the second regenerator is discharged through pipeline 327, a small portion is discharged from the system through pipeline 328, and a portion enters the blower 317. The oxygen-containing gas 341 is divided into oxygen-containing gas 342 and oxygen-containing gas 343. The circulating gas entering the blower 317 enters the second coking regeneration gas air cooler 318 through pipeline 329 for cooling, and then enters pipeline 330 to be fully mixed with the oxygen-containing gas 342. It is then sent to the dryer and dechlorinator 316 to remove water and chlorine from the circulating gas. After that, part of it is used as cooling transition zone gas 333 through pipeline 331, and the rest enters the electric heater 314 to be heated to 400-600°C. It is then returned to the coking zone 303 of the second regenerator through pipeline 332.

[0094] After the second coking process, the catalyst flows to the cooling transition zone 304. The gas 333 in the cooling transition zone is cooled to 350-450°C by the cooler 319 and then enters the cooling transition zone 304 through pipeline 334. The mixed gas 335 contains a certain amount of nitrogen and air, and is heated to 400-600°C by the electric heater 320. It is then fully mixed with the chlorinating agent-containing gas 336 and enters the oxychlorination zone 305 through pipeline 337.

[0095] The mixed gas 339 is heated to 400-600℃ by the electric heater 315 and sent into the drying zone 306 through the pipeline 340. The dried and regenerated catalyst flows out from the bottom of the second regenerator 301, enters the gas isolation zone 143, and is lifted by the lifter 144 to the upper reduction tank 121 of the first reactor I, completing the circulation of the catalyst to be regenerated.

[0096] According to a particularly preferred embodiment of the present invention, a method for regenerating an alkane dehydrogenation catalyst for olefin production includes the following steps:

[0097] (1) The catalyst to be generated is first coked in the coking zone of the first regenerator;

[0098] (2) The product obtained in step (1) is subjected to a second coking in the coking zone of the second regenerator to obtain the regenerated catalyst;

[0099] The pressure in the coking zone of the second regenerator is 0.15-0.3 MPa higher than that in the coking zone of the first regenerator.

[0100] The dew point of the regeneration gas in the coking zone of the second regenerator is ≤-60℃;

[0101] The Cl2 content in the regenerated gas from the first coke burner is 100-300 vppm;

[0102] The HCl content in the regenerated gas from the second coke burner is ≤0.5vppm.

[0103] The present invention will be described in detail below through examples and comparative examples. Unless otherwise specified, the reagents and materials used in the following examples and comparative examples are commercially available.

[0104] The carbon content in the catalyst was obtained by testing with a high-frequency infrared carbon-sulfur analyzer.

[0105] The Cl2 content in the regenerated gas from the first coke burner was determined by ion chromatography.

[0106] The HCl content in the regenerated gas from the second coke burner was determined by the detection tube method.

[0107] Catalyst A Preparation Example

[0108] (1) Preparation of composite carrier

[0109] Take 54g of aluminum sheet and add 610g of 18% hydrochloric acid solution to dissolve the aluminum sheet, obtaining a solution with an aluminum trichloride content of 4% by mass. Transfer the aluminum trichloride solution to a neutralization tank, add 850g of 6% ammonia solution, mix thoroughly at 60℃, and adjust the pH to 7.5-8.5. The generated aluminum hydroxide is filtered and washed, and 9mL of nitric acid (1:1 volume ratio) is added to the filter cake for acidification to obtain a sol. Under stirring, add 40mL of a solution containing 30g of urea and a hydrochloric acid solution containing 0.32g of tin to the sol, so that the Sn content in the solution is 0.32% of the dry basis of alumina, and stir for 1 hour for acidification. Then, under stirring, add 30g of kerosene and 3g of fatty alcohol polyoxyethylene ether dropwise to the acidified sol. Drop this sol into an oil-ammonia column with an oil phase on top and an ammonia phase on the bottom to form droplets. The oil phase is kerosene, and the ammonia concentration in the ammonia phase is 8% by mass. The wet bulbs were cured in an ammonia-water phase for 1 hour, then rinsed with deionized water, dried at 60°C for 6 hours, dried at 120°C for 10 hours, calcined in an air stream at 650°C for 4 hours, then treated in air with a water vapor content of 5% by volume at 650°C for 10 hours, and finally calcined at 1000°C for 4 hours to obtain the tin-containing θ-Al2O3 support a.

[0110] (2) Preparation of catalyst A

[0111] The tin-containing θ-Al₂O₃ support a was impregnated with an impregnation solution containing chloroplatinic acid and hydrochloric acid at 25°C for 4 hours. The impregnation solution contained 0.30% by mass platinum and 2.0% by mass chlorine (both relative to dry alumina), with a liquid / solid ratio of 1.8 mL / g. The resulting solid was dried at 120°C for 12 hours and calcined at 500°C for 4 hours. The calcined solid was then impregnated with a potassium nitrate solution at 25°C for 4 hours. The potassium nitrate solution contained 1% by mass potassium (relative to dry alumina), with a liquid / solid ratio of 1.4 mL / g. The resulting solid was dried at 120°C for 12 hours and calcined at 600°C for 4 hours. The calcined catalyst was reduced with hydrogen at 550°C for 2 hours to obtain catalyst A.

[0112] Example 1

[0113] according to Figure 1 The schematic diagram of the carbon alkane dehydrogenation process shown is as follows: Figure 2 The schematic diagram of the catalyst regeneration process shown in Table 1 illustrates the dehydrogenation reaction of low-carbon alkane feedstocks in the presence of catalyst A.

[0114] Table 1. Composition of low-carbon alkanes

[0115]

[0116]

[0117] The low-carbon alkane feedstock, after heat exchange, enters heater 110 via pipeline 101 for heating, and then enters the first reactor I for dehydrogenation. The effluent from the first reactor I enters heater 110 via pipeline 102 for heating and then enters the second reactor II. The effluent from the second reactor II enters heater 110 via pipeline 103 for heating and then enters the third reactor III. The effluent from the third reactor III enters heater 110 via pipeline 104 for heating and then enters the fourth reactor IV. The product from the fourth reactor IV enters the product fractionation system via pipeline 105 for separation. The inlet temperatures of the first to fourth reactors are controlled at 615℃, 636℃, 637℃, and 633℃, respectively; the hydrogen-to-hydrogen volume ratio is 0.53; the inlet pressures of the first to fourth reactors are 0.186MPa, 0.135MPa, 0.086MPa, and 0.039MPa, respectively; and the total mass hourly space velocity is 3h⁻¹. -1 The carbon content in the catalyst to be generated is 1.5% by mass.

[0118] Catalyst A enters the first reactor I to participate in the dehydrogenation reaction. It is then lifted by the elevator 122 and the elevator line 123 to the upper hopper 124 of the second reactor II. It then enters the second reactor II and passes through the elevator 125, the elevator line 126, the upper hopper 127 of the third reactor III, the third reactor III, the elevator 128, the elevator line 129, the upper hopper 130 of the fourth reactor IV, and the fourth reactor IV, where it is converted into a catalyst to be produced.

[0119] The catalyst to be generated flows out from the bottom of the fourth reactor IV, passes through the catalyst collector (not shown), through the No. 1 lock hopper 131, the elevator 132, and the elevator line 133 into the catalyst separation hopper 141, and after passing through the flow control zone 142, it enters the first regenerator 300.

[0120] The first coking is carried out in the coking zone 302 of the first regenerator. The conditions for the first coking include: a regeneration gas inlet temperature of 480℃, a pressure of 0.01MPa, an oxygen content of 0.9v% in the regeneration gas, a gas-to-agent volume ratio of 3500:1, and a residence time of 3.5 hours. The circulating gas from the coking zone 302 of the first regenerator is discharged through pipeline 321, a small portion is discharged from the system through pipeline 322, and the remainder enters the blower 312. After heat exchange by the first coking regeneration gas air cooler 313, it is fully mixed with the supplementary oxygen-containing gas 343 through pipeline 324 and the chlorinating agent-containing gas 325. The flow rate of the catalyst to be generated is 300kg / h, the mass of the supplementary Cl element is 0.54kg / h, and the Cl2 content in the first coking regeneration gas is 160vppm. The circulating gas is sent to the electric heater 311, and the outlet temperature of the electric heater 311 is controlled at 480℃. It is then returned to the inlet of the coking zone 302 of the first regenerator through pipeline 326.

[0121] The catalyst, after the first coking process, enters the No. 2 closed hopper 200 for pressurization. Low-pressure gas is discharged as exhaust gas 204, part of which is discharged as exhaust gas 205 from the No. 2 closed hopper, and part is returned to the No. 2 closed hopper 200 as regulating gas 203 in the balance zone. High-pressure supplementary gas 201 is introduced for further pressurization, and exhaust gas 202 from the high-pressure zone is discharged. After pressurization, it enters the second regenerator 301. The catalyst passes through the partition 350, the coking zone 303 of the second regenerator, the cooling transition zone 304, the oxychlorination zone 305, and the drying zone 306 from top to bottom. Second coking occurs in the coking zone 303 of the second regenerator. The conditions for the second coking include: regeneration gas inlet temperature of 530℃, pressure of 0.3MPa, oxygen content of 2.5v% in the regeneration gas, gas-to-catalyst volume ratio of 5000:1, and residence time of 3 hours.

[0122] The circulating gas in the coking zone 303 of the second regenerator is discharged through pipeline 327, a small portion is discharged from the system through pipeline 328, and a portion enters the blower 317. Oxygen-containing gas 341 is divided into oxygen-containing gas 342 and oxygen-containing gas 343. The circulating gas entering the blower 317 is cooled by the second coking regeneration gas air cooler 318 via pipeline 329 and then enters pipeline 330 to be thoroughly mixed with oxygen-containing gas 342. It is then sent to the dryer and dechlorinator 316 to remove water and chlorine from the circulating gas. Part of the gas then enters pipeline 331 as cooling transition zone gas 333, and the remainder enters the electric heater 314 to be heated to 530°C. Finally, it returns to the coking zone 303 of the second regenerator via pipeline 332. The dew point of the coking zone of the second regenerator is -60°C.

[0123] After the second coking process, the spent catalyst flows to the cooling transition zone 304. Gas 333 in the cooling transition zone is cooled to 460°C by cooler 319 and then enters the cooling transition zone 304 through pipeline 334. Mixed gas 335, containing a certain amount of nitrogen and air, is heated to 540°C by electric heater 320 and thoroughly mixed with chlorinating agent gas 336. It then enters the oxychlorination zone 305 through pipeline 337, with an average chlorine injection rate of 2.7 kg / h. Mixed gas 339 is heated to 560°C by electric heater 315 and sent to the drying zone 306 through pipeline 340. The dried, regenerated catalyst flows out from the bottom of the second regenerator 301 and enters the gas isolation zone 143. It is then lifted by elevator 144 to the upper reduction tank 121 of the first reactor I, where it participates in the dehydrogenation reaction, completing the cycle of the spent catalyst. The reaction time is 24 hours from the time oil enters the reactor.

[0124] Example 2

[0125] The dehydrogenation of low-carbon alkane and the regeneration of the spent catalyst were carried out according to the method of Example 1, except that the pressure of the coking zone of the second regenerator was changed to be 0.09 MPa higher than that of the coking zone of the first regenerator. All other aspects were the same as in Example 1.

[0126] Example 3

[0127] The dehydrogenation of low-carbon alkane and the regeneration of the catalyst were carried out according to the method of Example 1, except that the dew point of the regenerated gas in the coke burning zone of the second regenerator was -40°C, and the rest were the same as in Example 1.

[0128] Example 4

[0129] The dehydrogenation of low-carbon alkane and the regeneration of the spent catalyst were carried out according to the method of Example 1, except that the Cl2 content in the regeneration gas of the first coke was 70 vppm, and the rest were the same as in Example 1.

[0130] Example 5

[0131] The dehydrogenation of low-carbon alkane and the regeneration of the catalyst were carried out according to the method of Example 1, except that the Cl2 content in the regeneration gas of the first coke was 340 vppm, and the rest were the same as in Example 1.

[0132] Example 6

[0133] The dehydrogenation of low-carbon alkane and the regeneration of the spent catalyst were carried out according to the method of Example 1, except that the HCl content in the regenerated gas of the second coke was 2vppm, and the rest were the same as in Example 1.

[0134] Comparative Example 1

[0135] The dehydrogenation of low-carbon alkane and the regeneration of the spent catalyst were carried out according to the method of Example 1, except that a second regenerator was not set up. Instead, a first coking zone and a second coking zone were set up in the first regenerator. The pressure of the first coking zone and the second coking zone was 0.01 MPa. Everything else was the same as in Example 1.

[0136] Comparative Example 2

[0137] The dehydrogenation of low-carbon alkane and the regeneration of the spent catalyst were carried out according to the method of Example 1, except that a second regenerator was not set up. Instead, a first coking zone and a second coking zone were set up in the first regenerator. The pressure of the first coking zone and the second coking zone was 0.3 MPa. Everything else was the same as in Example 1.

[0138] The regeneration results of the catalysts in the embodiments and comparative examples of the present invention are shown in Table 2.

[0139] The metal dispersion was determined by the hydrogen chemisorption method.

[0140] Table 2 Results of catalyst regeneration

[0141]

[0142] Note: (1)Randomly select 100 regenerated catalysts, cut them open and observe the "core coke" condition. The presence of black spots inside the regenerated catalyst indicates the presence of "core coke". Record the results.

[0143] As can be seen from the results in Table 2, the regeneration method of this invention results in a low carbon content in the regenerated catalyst, the absence of "core coke" phenomenon, and high metal dispersion. In contrast, the regenerated catalyst obtained by the regeneration method of Comparative Example 1 has a "core coke" ratio as high as 16% and a high carbon content. Although the regenerated catalyst obtained by the regeneration method of Comparative Example 2 has a lower carbon content, its metal dispersion is low.

[0144] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for regenerating a catalyst for alkane dehydrogenation to olefins, characterized in that, The method includes the following steps: (1) The catalyst to be generated is first coked in the coking zone of the first regenerator; (2) The product obtained in step (1) is subjected to a second coking in the coking zone of the second regenerator to obtain the regenerated catalyst; The pressure in the coking zone of the second regenerator is 0.15-0.3 MPa higher than that in the coking zone of the first regenerator. The method also includes partially discharging the circulating gas generated in the coking zone of the first regenerator from the system, and partially returning it to the coking zone of the first regenerator after heat exchange, supplemented with chlorinating agent gas and oxygen-containing gas. The dew point of the regenerated gas in the coking zone of the second regenerator is ≤-50℃. The catalyst to be generated includes a support, an active component, and carbon; the active component includes platinum group metals, group IVA metals, alkali metals, and chlorine; The first coking conditions include: a pressure of 0.001-0.1 MPa; and an oxygen content of 0.1-1.2 v% in the regenerated gas. The second coking conditions include: a pressure of 0.06-0.3 MPa; and an oxygen content of 1.2-5 v% in the regenerated gas. The Cl2 content in the regenerated gas of the first coking is 1-500 vppm. The Cl2 content in the regenerated gas of the first coking refers to the Cl2 content in the coking zone of the first regenerator during the first coking process.

2. The method according to claim 1, wherein, Based on the total amount of the support and active components, the carbon content of the catalyst to be generated is 1-5% by mass.

3. The method according to claim 2, wherein, Based on the total amount of the support and active components, the carbon content of the catalyst to be generated is 1-3 by mass.

4. The method according to claim 1, wherein, The carrier is selected from at least one of alumina, silicon oxide, and zirconium oxide.

5. The method according to claim 4, wherein, The carrier is aluminum oxide.

6. The method according to claim 1, wherein, Based on the total amount of the carrier, the content of the platinum group metals is 0.1-1 by mass; the content of the group IVA metals is 0.1-1 by mass; the content of the alkali metals is 0.5-2 by mass; and the content of chlorine is 0.4-2 by mass.

7. The method according to claim 1, wherein, The dew point of the regeneration gas in the coking zone of the second regenerator is ≤-60℃.

8. The method according to any one of claims 1-7, wherein, The first coking conditions include: a regeneration gas inlet temperature of 450-550℃; a gas-agent volume ratio of 1000-10000; and a residence time of 1-5 hours.

9. The method according to claim 8, wherein, The first coking conditions include: a regeneration gas inlet temperature of 460-500℃; a pressure of 0.01-0.1MPa; an oxygen content of 0.8-1.2v in the regeneration gas; a gas-agent volume ratio of 2000-5000; and a residence time of 2-4 hours.

10. The method according to any one of claims 1-7, wherein, The chlorinating agent is Cl2.

11. The method according to any one of claims 1-7, wherein, The second coking conditions include: a regeneration gas inlet temperature of 500-600℃; a gas-agent volume ratio of 1000-10000; and a residence time of 1-5 hours.

12. The method according to claim 11, wherein, The second coking conditions include: a regeneration gas inlet temperature of 520-560℃; a pressure of 0.1-0.3MPa; an oxygen content of 2-4v% in the regeneration gas; a gas-agent volume ratio of 3000-6000; and a residence time of 2-4 hours.

13. The method according to any one of claims 1-7, wherein, The HCl content in the regenerated gas from the second coke burner is ≤0.5vppm.

14. The method according to claim 1, wherein, The Cl2 content in the regenerated gas from the first coke burner is 100-300 vppm.

15. The method according to any one of claims 1-7, wherein, The method further includes: partially discharging the circulating gas generated in the coking zone of the second regenerator from the system, and partially returning it to the coking zone of the second regenerator after heat exchange, dechlorination, drying, and replenishment with oxygen-containing gas.

16. The method according to any one of claims 1-7, wherein, The method further includes: contacting the regenerated catalyst with low-carbon alkanes to carry out a dehydrogenation reaction.

17. The method according to claim 16, wherein, The low-carbon alkane is a C2-C4 alkane.

18. The method according to claim 16, wherein, The conditions for the dehydrogenation reaction include: a temperature of 550-700℃; a pressure of 0.01-0.5 MPa; a hydrogen-to-hydrocarbon volume ratio of 0.2-2; and a mass hourly space velocity (HHSV) of 0.1-10 h⁻¹. -1 .

19. The method according to claim 18, wherein, The conditions for the dehydrogenation reaction include: a temperature of 600-650℃; a pressure of 0.01-0.2 MPa; a hydrogen-to-hydrocarbon volume ratio of 0.4-0.7; and a mass hourly space velocity (HHSV) of 0.3-4 h⁻¹. -1 .

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