Process for the regeneration of dehydrogenation catalysts

Abstract

The present application relates to the technical field of petroleum chemical industry, and discloses a regeneration method of dehydrogenation catalyst, which comprises the following steps: (1) carrying out first charring on the catalyst to be regenerated in a first charring zone, and then carrying out second charring in a second charring zone; (2) drying the product after the second charring, and then carrying out oxychlorination and cooling to obtain the regenerated catalyst; wherein the gases discharged from the first charring zone, the second charring zone and the oxychlorination zone are independently recycled. By arranging the drying zone below the charring zone, the independent circulation of the gases in the charring zone and the oxychlorination zone is realized, the dispersion of noble metals in the low-carbon alkane dehydrogenation catalyst is improved, and the regeneration effect of the catalyst is improved.

Description

Technical Field

[0001] This invention relates to the field of petrochemical technology, and more specifically to a method for regenerating a dehydrogenation catalyst. 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 the byproduct of steam cracking to produce ethylene, while isobutylene is almost entirely derived from refinery gas and cracked C4 fractions.

[0003] The dehydrogenation process for producing low-carbon olefins from low-carbon alkanes is mainly divided into moving bed and fixed bed processes. Fixed bed processes have a relatively simple reaction system design, but require frequent catalyst regeneration and switching operations, placing high demands on the control system, valves, and equipment. Moving bed processes, on the other hand, enable continuous catalyst regeneration and recycling, maintaining the catalyst in a high-activity state, significantly improving catalyst activity and ensuring propylene yield.

[0004] The regeneration process of moving bed low-carbon alkane catalysts generally involves processes such as carbonization, redispersion of metallic Pt, and reduction of oxidized metals. The redispersion effect of metallic Pt is crucial to the reaction performance of the regenerated catalyst. The redispersion reaction process of metallic Pt is shown below:

[0005] Metal + Cl₂ + O₂ → Oxidized / Redispersed Metal

[0006] In the redispersion process of metal Pt, high chlorine content and oxygen-rich environment are conducive to the redispersion of metal on the catalyst. However, in the existing process, the catalyst flows down from the coking zone and carries some moisture. In the oxychlorination zone, water reacts with Cl2 as follows, which leads to increased acidity of the catalyst and thus affects the catalyst performance.

[0007] 2Cl₂ + H₂O → 4HCl + O₂

[0008] Meanwhile, the existing process injects chloride into the oxychlorination zone in a "one-pass" manner, which leads to problems such as increased chlorine injection during regeneration, increased risk of chlorine corrosion, and high chlorine content in the regeneration gas tail gas.

[0009] CN104107704B discloses a method for regenerating a platinum-containing low-carbon alkane dehydrogenation catalyst. The technical solution includes: staged carbonization treatment with a gas stream containing 0.1-10 mol% O2; deactivating the catalyst by contacting a halogen-containing component with a gas stream of H2O or decomposable oxygen-containing compounds to increase the halogen content of the catalyst; treating the catalyst with a gas stream containing 1-10 mol% O2 to promote the redispersion of the active metal component Pt; and reducing the active metal component at 450-650℃ under a reducing atmosphere. The regeneration process involves a relatively large amount of O2, requires a long regeneration time, and necessitates the introduction of different gases at different stages of the staged carbonization treatment, making the operation quite complex.

[0010] 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.

[0011] 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 then enters the final-stage reactor, 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. This method mainly changes the catalyst flow direction, without significantly improving catalyst regeneration.

[0012] Therefore, for the spent catalysts after dehydrogenation of low-carbon alkanes, there is a need for a catalyst regeneration method that can effectively remove carbon deposits, improve the dispersion of precious metals, and is easy to operate. Summary of the Invention

[0013] The purpose of this invention is to overcome the problems of poor noble metal dispersion, difficulty in removing carbon deposits, and poor regeneration effect of low-carbon alkane dehydrogenation catalysts after regeneration in the prior art. This invention provides a method for regenerating dehydrogenation catalysts. This method achieves independent circulation of gases in the coking zone and the oxychlorination zone by placing the drying zone below the coking zone, which can improve the noble metal dispersion of low-carbon alkane dehydrogenation catalysts and improve the catalyst regeneration effect.

[0014] To achieve the above objectives, the present invention provides a method for regenerating a dehydrogenation catalyst, wherein the method includes:

[0015] (1) After the catalyst to be generated is first coked in the first coking zone, it is second coked in the second coking zone;

[0016] (2) The product after the second coking is passed through a drying zone, an oxychlorination zone and a cooling zone to obtain the regenerated catalyst;

[0017] The gases discharged from the first coking zone, the second coking zone, and the oxychlorination zone are each circulated independently.

[0018] Preferably, the oxygen content in the regenerated gas of the coking zone is 0.2-1% by volume, more preferably 0.5-1% by volume.

[0019] Preferably, the oxygen content in the regenerated gas of the second-stage coking zone is 1-10% by volume, and more preferably 2-6% by volume.

[0020] Preferably, the oxychlorination zone further introduces a chlorinating agent, which is chlorine gas and / or an organic chloride.

[0021] Preferably, the chlorinating agent is mixed with the third circulating gas discharged from the oxychlorination zone and then recycled back into the oxychlorination zone.

[0022] The beneficial effects achieved through the above technical solution are as follows:

[0023] (1) The regeneration method provided by the present invention, by placing the drying zone below the coking zone, realizes independent circulation of gas in the coking zone and the oxychlorination zone, and the oxychlorination zone is self-circulating, which can improve the noble metal dispersion of the low-carbon alkane dehydrogenation catalyst and improve the catalyst regeneration effect.

[0024] (2) In this invention, preferably, the chlorine loss is reduced by the self-circulation of the oxychlorination zone without external chlorine discharge, and the chlorine content in the circulating gas of the oxychlorination zone is guaranteed by reasonably adjusting the chlorine injection amount, and the chlorine injection amount is reduced.

[0025] (3) In this invention, preferably, for the presence of easily coked carbon deposits with low carbonization degree and difficult-to-coke carbon deposits with high carbonization degree on the catalyst to be produced, the oxygen content of the first coking zone and the second coking zone is controlled to remove the carbon deposits on the catalyst in a targeted manner without damaging the catalyst. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the process flow for regenerating the dehydrogenation catalyst.

[0027] Explanation of reference numerals in the attached figures

[0028] Figure 1

[0029] 101, 116, 117, 120, 121, 123, 124, 127, 128, 130, 132, 133, 134, 136, 139, 141, 142 - Pipelines 102-Catalyst Separation Hopper 103-Pressure Transformation and Flow Control Area

[0030] 104-Buffer 105 - Section 1 (Scorched Zone) 106, 108, 110, 112 - Catalyst feed legs

[0031] 107 - Second stage of charring zone 109-Drying Zone 111-Oxychlorination Zone

[0032] 113-Cooling Area 114 - Gas Isolation Zone 115-lifter 118, 125, 137, 140 - Booster compressors 119, 126 - Heat exchangers 122, 129, 131, 135 - Electric heaters

[0033] 138-Cooler Detailed Implementation

[0034] 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.

[0035] This invention provides a method for regenerating a dehydrogenation catalyst, wherein the method includes:

[0036] (1) After the catalyst to be generated is first coked in the first coking zone, it is second coked in the second coking zone;

[0037] (2) The product after the second coking is passed through a drying zone, an oxychlorination zone and a cooling zone to obtain the regenerated catalyst;

[0038] The gases discharged from the first coking zone, the second coking zone, and the oxychlorination zone are each circulated independently.

[0039] In this invention, by placing the drying zone below the coking zone, independent circulation of gases in the coking zone and the oxychlorination zone is achieved. The oxygen content and coking conditions in the two coking zones are controlled separately, effectively removing carbon deposits of different carbonization degrees on the catalyst to be regenerated. The oxychlorination zone achieves self-circulation. By maintaining appropriate oxygen and chlorine content in the oxychlorination zone, the noble metal dispersion of the low-carbon alkane dehydrogenation catalyst can be improved, thereby improving the catalyst regeneration effect.

[0040] In this invention, unless otherwise stated, "the gases discharged from the first-stage coking zone and the second-stage coking zone are circulated independently" means that a portion of the gas discharged from the first-stage coking zone is circulated back to the first-stage coking zone as the first circulating gas, and does not go to the second-stage coking zone; a portion of the gas discharged from the second-stage coking zone is circulated back to the second-stage coking zone as the second circulating gas, and does not go to the first-stage coking zone. That is, the regeneration gas from the first-stage coking zone and the second-stage coking zone will not cross-circulate.

[0041] In this invention, unless otherwise stated, the regeneration gas of the coking zone refers to the gas introduced into the coking zone, which is the gas drawn from the coking zone, mixed with air and / or the gas discharged from the drying zone, and then circulated back into the coking zone. When the regeneration system is first started, gas can be introduced from outside the system as the regeneration gas for the coking zone.

[0042] In this invention, "the gas in the oxychlorination zone is independently circulated" means that the gas discharged from the oxychlorination zone is circulated back to the oxychlorination zone.

[0043] According to the present invention, preferably, the gas discharged from the drying zone is divided into gas I and gas II.

[0044] According to the present invention, preferably, gas I is mixed with the first circulating gas discharged from the first coking zone and circulated back to the first coking zone. In the present invention, the regeneration gas of the first coking zone is introduced from outside the system or is gas I mixed with the first circulating gas and then circulated back to the first coking zone.

[0045] In this invention, the first circulating gas is a portion of the gas discharged from the first coking zone. The flow rate of the first circulating gas is determined by the regeneration scale of the device. Those skilled in the art can adjust the mixing of gas I to ensure that the oxygen content in the regenerated gas from the first coking zone meets the conditions for the first coking. In this invention, the device regeneration scale refers to the catalyst circulation mass.

[0046] According to the present invention, preferably, gas II is mixed with the second circulating gas discharged from the second-stage coking zone and recycled back to the second-stage coking zone. In the present invention, the regeneration gas of the second-stage coking zone is the gas that is mixed with gas II and recycled back to the second-stage coking zone.

[0047] In this invention, the second circulating gas is a portion of the gas discharged from the two-stage coking zone. The flow rate of the second circulating gas is determined by the regeneration scale of the device. Those skilled in the art can adjust the mixing of gas II so that the oxygen content in the regenerated gas of the two-stage coking zone meets the conditions for the second coking.

[0048] In this invention, preferably, the above-mentioned cycle can flexibly control the conditions of the first and second coking, thereby improving the regeneration capacity of the regenerator.

[0049] In this invention, the flow rates of Gas I and Gas II are determined by the regeneration scale of the device. Based on the different flow rates of regeneration gas required for the first and second coking zones of the device, those skilled in the art can make adaptive adjustments to meet the conditions for the first and second coking processes.

[0050] According to the present invention, preferably, the oxygen content in the regeneration gas of the coking zone is 0.2-1% by volume, more preferably 0.5-1% by volume.

[0051] According to the present invention, preferably, the conditions for the first coking process include: the inlet temperature of the regeneration gas is 350-600°C, preferably 400-500°C; the pressure is 0.1-1 MPa, preferably 0.3-0.8 MPa; the gas-to-solvent volume ratio is 2000-20000:1, preferably 5000-10000:1; and the residence time is 10-600 min, preferably 30-480 min.

[0052] Unless otherwise specified, the pressure referred to in this invention is gauge pressure.

[0053] In this invention, preferably, the regeneration gas in the coking zone has a low oxygen content, which can remove carbon deposits with a low degree of carbonization during the first coking process and reduce the carbon content of the resulting regenerated catalyst.

[0054] According to the present invention, preferably, the oxygen content in the regenerated gas of the two-stage coking zone is 1-10% by volume, more preferably 2-6% by volume.

[0055] According to the present invention, preferably, the conditions for the second coking process include: an inlet temperature of 400-600°C, more preferably 440-550°C; a pressure of 0.1-1 MPa, more preferably 0.4-0.8 MPa; a gas-to-agent volume ratio of 2000-20000:1, more preferably 5000-10000:1; and a residence time of 10-600 min, more preferably 30-480 min.

[0056] In this invention, the oxygen content in the regenerated gas of the second-stage coking zone is higher than that of the regenerated gas of the first-stage coking zone. Increasing the oxygen content of the regenerated gas can burn off the carbon deposits that are difficult to burn.

[0057] In this invention, the spent catalyst contains both easily charred low-carbonized carbon deposits and difficult-to-char high-carbonized carbon deposits. By controlling different charring conditions and regeneration gas oxygen content during the two-step charring process, carbon deposits of different carbonization levels can be removed in a targeted manner. This avoids situations where the oxygen content is too low during charring, leading to incomplete charring of the spent catalyst and the presence of unburned nuclei in the catalyst core; or where the oxygen content is too high, causing overheating damage to the catalyst and regenerator internal components.

[0058] According to the present invention, preferably, the drying conditions of the drying zone include: the gas temperature at the inlet of the drying zone is 120-600℃, preferably 400-600℃; the oxygen content in the drying gas is 0.1-21% by volume, preferably 5-21% by volume; the gas-solvent volume ratio is 100-500:1, preferably 200-400:1; and the residence time is 20-100 min, preferably 30-80 min.

[0059] In this invention, preferably, the dew point of the gas entering the drying zone is below -60°C, and the water content of the gas exiting the drying zone is not particularly limited.

[0060] The regeneration method of this invention features completely isolated coking zones, with separate gas circulation and independent control of oxygen content and regeneration pressure. This improves regeneration capacity and coking flexibility, allowing for flexible adjustment of conditions in both zones based on catalyst regeneration progress. A drying zone, located below the second coking zone, removes moisture generated during coking, allowing the dried catalyst to enter the oxychlorination zone, reducing side reactions between the chlorinating agent and water. In the oxychlorination zone, gas circulates independently, and the catalyst flows through designated feed legs. The oxygen concentration in the oxychlorination zone is not limited by the coking zone, maintaining higher oxygen and chlorine content, reducing chlorine loss, decreasing the amount of chlorinating agent injected, and resulting in better oxychlorination of the catalyst.

[0061] According to the present invention, preferably, the oxychlorination conditions of the oxychlorination zone include: the gas temperature at the inlet of the oxychlorination zone is 120-600℃, preferably 400-550℃; the oxygen content is 3-21% by volume, preferably 7-21% by volume; the gas-agent volume ratio is 100-500:1, preferably 200-400:1; and the residence time is 10-100 min, preferably 30-50 min.

[0062] According to the present invention, preferably, a chlorinating agent is further introduced into the oxychlorination zone, wherein the chlorinating agent is chlorine gas and / or an organic chloride. In the present invention, the amount of chlorinating agent injected is not particularly limited, as long as the chlorine content in the oxychlorination zone meets the oxychlorination conditions; based on the catalyst cycle mass, the chlorine content in the oxychlorination zone is 0.02-1% by mass, preferably 0.1-0.5% by mass.

[0063] In this invention, the organochlorine is a conventional organochlorine used for catalyst regeneration in the art, preferably selected from at least one of tetrachloroethylene, dichloroethane, and trichloroethane.

[0064] In this invention, preferably, the oxychlorination zone may also optionally introduce air and / or oxygen together with the chlorinating agent.

[0065] In this invention, preferably, after the first circulating gas is replenished with a chlorinating agent, it is mixed with gas I and circulated back to the first-stage coking zone; after the second circulating gas is replenished with a chlorinating agent, it is mixed with gas I and circulated back to the second-stage coking zone. Replenishing chlorine in both the first and second-stage coking zones can reduce metal accumulation of the catalyst during the coking process.

[0066] In this invention, there is no particular limitation on the amount of chlorinating agent-containing gas supplemented to the first and second circulating gas. Preferably, based on the catalyst circulation mass, the mass of Cl element in the first coking zone is 0.01-0.5% by mass, and the mass of Cl element in the second coking zone is 0.01-0.5% by mass.

[0067] According to the present invention, preferably, the chlorine content in the oxychlorination zone is 0.02-1% by mass, more preferably 0.1-0.5% by mass, based on the catalyst cycle mass. The role of chlorine is to provide acidity and disperse metals in the catalyst; it is an indispensable component of bifunctional catalysts, and too much or too little chlorine will affect catalyst performance.

[0068] According to the present invention, preferably, the chlorinating agent is mixed with the third circulating gas discharged from the oxychlorination zone and then recycled back into the oxychlorination zone. In conventional methods, chlorine from the oxychlorination zone is often discharged through the tail gas or used to replenish the coking zone. Discharge after coking inevitably leads to chlorine waste and increases treatment and investment costs. The present invention reduces chlorine loss through self-circulation within the oxychlorination zone, eliminating external chlorine discharge, and ensures the chlorine content in the oxychlorination zone by rationally adjusting the chlorine injection rate.

[0069] According to the present invention, preferably, the cooling conditions of the cooling zone include: the oxygen content in the cooling gas is 0.1-21% by volume, preferably 5-21% by volume; the gas temperature at the inlet of the cooling zone is 0-200°C, preferably 20-80°C; the gas-solvent volume ratio is 100-500:1, preferably 200-400:1; and the residence time is 20-100 min, preferably 30-80 min.

[0070] In this invention, the catalyst is cooled to 100℃-400℃, preferably 100℃-200℃. After cooling, the catalyst is lifted and then fed into a reducer, where it is reduced to obtain a regenerated catalyst. The regenerated catalyst then enters a moving bed reaction zone to participate in the dehydrogenation reaction. The spent catalyst obtained from the dehydrogenation reaction is lifted, dust-removed, and metered before entering a catalyst regenerator for regeneration, completing the cycle.

[0071] According to the present invention, preferably, the inlet pressure of the first coking zone is 1-20 kPa higher than the inlet pressure of the second coking zone, more preferably 1-10 kPa higher.

[0072] According to the present invention, preferably, the inlet pressure of the second-stage coking zone is 1-20 kPa higher than the outlet pressure of the drying zone, more preferably 2-10 kPa higher.

[0073] According to the present invention, preferably, the outlet pressure of the oxychlorination zone is 1-20 kPa higher than the pressure of the drying zone, more preferably 2-10 kPa higher.

[0074] According to the present invention, preferably, the outlet pressure of the cooling zone is 0-20 kPa higher than the pressure of the oxychlorination zone, more preferably 2-10 kPa higher.

[0075] In this invention, limiting the pressure difference between each zone is to ensure the safety of the regenerator and prevent high-oxygen-content gas from entering areas with low oxygen content, causing overheating and affecting the normal circulation of the gas circuit.

[0076] In this invention, the apparatus used for regenerating the catalyst is not particularly limited, as long as it meets the conditions defined by the regeneration method of this invention.

[0077] 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.

[0078] 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. The source of the spent catalyst is not particularly limited; it can be commercially available or prepared using existing methods.

[0079] According to the present invention, preferably, the catalyst to be generated comprises a support and an active component.

[0080] In this invention, preferably, the catalyst further includes carbon, with a carbon content of 1-5% by mass, preferably 1-3% by mass, based on the total weight of the support and active components.

[0081] According to the present invention, preferably, the carrier is an alumina carrier, and more preferably θ-alumina.

[0082] According to the present invention, preferably, the active component comprises platinum group metals, group IVA metals, alkali metals and chlorine.

[0083] In this invention, preferably, the platinum group metal element is platinum and / or palladium, with platinum being the most preferred.

[0084] In this invention, preferably, the IVA group metal is selected from at least one of silicon, germanium and tin, and preferably tin.

[0085] In this invention, preferably, the alkali metal is selected from at least one of potassium, sodium and rubidium, with potassium being the most preferred.

[0086] In this invention, preferably, based on the total mass 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.

[0087] In this invention, preferably, the platinum group metal element is platinum, and the content of the platinum group metal element is 0.1-1% by mass, based on the total amount of the carrier.

[0088] In this invention, preferably, the Group IVA metal element is tin, and the content of the Group IVA metal element is 0.1-1% by mass, based on the total amount of the carrier.

[0089] In this invention, preferably, the alkali metal element is potassium, and the content of the alkali metal element is 0.5-2% by mass, based on the total amount of the carrier.

[0090] In this invention, preferably, the chlorine content is 0.5-1.5% by mass, based on the total amount of the carrier.

[0091] In this invention, preferably, the carbon content in the regenerated catalyst is less than 0.02% by mass, and more preferably less than 0.01% by mass.

[0092] 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.

[0093] The following combination Figure 1 To further illustrate the regeneration method of the present invention, the regeneration process flow of the catalyst to be regenerated is as follows: Figure 1As shown, the regeneration cycle of the spent catalyst is as follows: the spent catalyst flows out from the bottom of the moving bed reaction zone, passes through the elevator (not shown in the figure), enters the catalyst separation hopper 102 through pipeline 101, and separates the dust in the catalyst. The washed spent catalyst enters the pressure conversion and flow control zone 103. Under the action of gravity, the spent catalyst enters the first coking zone 105 through the buffer zone 104 for the first coking, enters the second coking zone 107 through the catalyst discharge leg 106 for the second coking, enters the drying zone 109 through the catalyst discharge leg 108 for drying, enters the oxychlorination zone 111 through the catalyst discharge leg 110 for oxychlorination, enters the cooling zone 113 through the catalyst discharge leg 112 for cooling, and then enters the gas isolation zone 114. In the gas isolation zone 114, the oxygen environment is converted into a hydrogen environment, and then the gas is lifted to the reduction tank (not shown in the figure) through the lifter 115 and the lift pipeline. In the reduction tank, the oxidized catalyst is reduced to the reduced catalyst. The reduced catalyst enters the moving bed reaction zone to participate in the reaction and completes the catalyst cycle.

[0094] According to a preferred embodiment of the present invention, such as Figure 1 As shown, the gas circulation process is as follows: In the first coking zone 105, regenerated gas is introduced for the first coking process. The generated gas is discharged through pipeline 116, a small amount is discharged to the atmosphere through pipeline 117, and the majority serves as the first circulating gas. This gas is pressurized by compressor 118, heat-exchanged by heat exchanger 119, and then mixed with the drying zone gas I introduced through pipeline 120. After being heated by electric heater 122 through pipeline 121, it is circulated back to the first coking zone 105, achieving independent circulation. In the second coking zone 107, the regenerated gas undergoes the second coking process. The generated gas is discharged through pipeline 123, a small amount is discharged to the atmosphere through pipeline 124, and the majority serves as the second circulating gas. This gas is pressurized by compressor 125, heat-exchanged by heat exchanger 126, and then mixed with the drying zone gas II introduced through pipeline 127. After being heated by electric heater 129 through pipeline 128, it is circulated back to the second coking zone 107, achieving independent circulation.

[0095] Air is introduced through pipeline 130, and part of it is heated by electric heater 131 before entering drying zone 109. The dried gas flows upward, removing moisture from the catalyst. The dried gas is discharged through pipeline 132, with a portion serving as Gas I in the first coking zone 105 and Gas II in the second coking zone 107. The excess is discharged through pipeline 133. Chlorin is introduced through pipeline 134, mixed with air from pipeline 130, heated by electric heater 135, and then enters oxychlorination zone 111. The gas in oxychlorination zone flows upward over the catalyst awaiting generation, undergoing oxychlorination in zone 111, which redisperses the accumulated Pt metal on the catalyst. The oxychlorinated gas is drawn out through pipeline 136, pressurized by booster 137, mixed with supplementary air introduced through pipeline 130 and chlorin introduced through pipeline 134, and then circulated back to oxychlorination zone 111, achieving independent circulation.

[0096] Part of the air introduced through pipeline 130 is cooled by cooler 138 and then enters cooling zone 113 to cool the catalyst to be generated. The cooling gas discharged from cooling zone 113 is led out through pipeline 139, pressurized by booster 140, mixed with the air introduced through pipeline 130, and circulated back to cooling zone 113 to complete the cycle. Chloride is introduced into the first coking zone 105 and the second coking zone 107 through pipelines 141 and 142, respectively.

[0097] In this invention, the regenerated catalyst is used for the dehydrogenation reaction of low-carbon alkanes, wherein the low-carbon alkanes are C2-C4 alkanes. The source of the low-carbon alkanes is not particularly limited, but is preferably from at least one of refinery by-products, shale gas, and associated gas from oil fields.

[0098] In this invention, the dehydrogenation reaction conditions are not particularly limited and can be conventional low-carbon dehydrogenation reactions in the art. According to a preferred embodiment of the invention, the dehydrogenation reaction conditions 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 molar ratio of 0.2-2:1, preferably 0.4-0.7:1; and a feed volume hourly space velocity of 0.1-10 h⁻¹. -1 Preferably 0.3-8h -1 .

[0099] The present invention will now be described in detail through examples and comparative examples. In the following examples and comparative examples,

[0100] The dispersion of metallic Pt in the catalyst was measured using a Micron AutoChem2920 chemisorption analyzer.

[0101] The carbon content in the catalyst was analyzed using the standard method Q / SH 3360 317—2020;

[0102] During the regeneration process, the oxygen content was measured using an online oxygen analyzer, and the chlorine content was measured using ion chromatography.

[0103] The dehydrogenation catalyst was industrial grade PST-100, purchased from Hunan Jianchang Petrochemical Co., Ltd.

[0104] The chlorinating agent is chlorine gas.

[0105] Dehydrogenation of low-carbon alkanes yields a catalyst to be produced.

[0106] In the moving bed reaction zone of the microreactor, 2 ml of industrial-grade PST-100 dehydrogenation catalyst was charged, using a mixture of hydrogen and propane as feed gas, and the reaction was carried out at 620 °C, 0.11 MPa, and a propane feed volume hourly space velocity of 2.8 h⁻¹. -1The catalyst was reacted for 10 hours under a hydrogen / propane molar ratio of 0.5:1 to obtain the catalyst to be generated. The carbon content of the catalyst was analyzed by the standard method Q / SH 3360 317—2020 and was found to be 1.5% by mass.

[0107] Example 1

[0108] The spent catalyst obtained from the dehydrogenation of low-carbon alkanes is processed according to... Figure 1 The process shown involves the recycling of the catalyst to be generated and the recycling of the regenerated gas.

[0109] The spent catalyst flows out from the bottom of the moving bed reaction zone, passes through an elevator (not shown in the figure), and enters the catalyst separation hopper 102 via pipeline 101 to separate the dust from the catalyst. The washed spent catalyst enters the pressure switching and flow control zone 103. Under the action of gravity, the spent catalyst enters the first coking zone 105 through the buffer zone 104 for the first coking. The conditions for the first coking are: the inlet temperature of the regeneration gas is 460℃, the oxygen content in the regeneration gas is 0.9% by volume, the pressure is 0.4MPa, the residence time is 50min, and the gas-catalyst volume ratio is 8000:1.

[0110] After the first coking, the spent catalyst enters the second coking zone 107 via the catalyst feeding leg 106 for the second coking. The conditions for the second coking are: the inlet temperature of the regenerated gas is 480℃, the oxygen content in the regenerated gas is 2.5% by volume, the pressure is 0.4MPa, the residence time is 50min, and the gas-catalyst volume ratio is 8000:1.

[0111] The second coke-burned catalyst enters the drying zone 109 via catalyst feed leg 108 for drying. The drying conditions are: inlet temperature of 550℃, oxygen content in the drying gas of 21% by volume, gas-catalyst volume ratio of 200:1, and residence time of 40 min.

[0112] The spent catalyst enters the oxychlorination zone 111 via catalyst feed leg 110 for oxychlorination. The oxychlorination conditions are: inlet temperature 490℃, oxygen content in the oxychlorination zone 21% by volume, gas-to-catalyst volume ratio 200:1, and residence time 40 min. Based on the mass of the spent catalyst, the chlorination content in the oxychlorination zone is 0.4% by mass, and the chlorinating agent injection rate is 2.7 g / h. After oxychlorination, the spent catalyst enters the cooling zone 113 via catalyst feed leg 112 for cooling. The cooling conditions are: oxygen content in the cooling gas 21% by volume, inlet gas temperature 50℃, gas-to-catalyst volume ratio 100-500:1, preferably 200-400:1, and residence time 20-100 min, preferably 30-80 min. The catalyst temperature after cooling is 200℃.

[0113] The catalyst then enters the gas isolation zone 114, where the oxygen environment is converted into a hydrogen environment. It is then lifted to the reduction tank (not shown in the figure) via the lifter 115 and the lift pipeline. In the reduction tank, the oxidized catalyst is reduced to the reduced catalyst, and the regenerated catalyst is obtained. The reduced catalyst enters the moving bed reaction zone to participate in the reaction, completing the catalyst cycle.

[0114] The gas circulation process is as follows: The regenerated gas from the first-stage coking zone 105 undergoes primary coking. The generated gas is discharged through pipeline 116, a small amount is discharged to the atmosphere through pipeline 117, and the majority serves as the first circulating gas. This gas is pressurized by booster 118, heat-exchanged by heat exchanger 119, and then mixed with the drying zone gas I introduced through pipeline 120. After being heated by electric heater 122 through pipeline 121, it is circulated back to the first-stage coking zone 105, achieving independent circulation. The regenerated gas from the second-stage coking zone 107 undergoes secondary coking. The generated gas is discharged through pipeline 123, a small amount is discharged to the atmosphere through pipeline 124, and the majority serves as the second circulating gas. This gas is pressurized by booster 125, heat-exchanged by heat exchanger 126, and then mixed with the drying zone gas II introduced through pipeline 127. After being heated by electric heater 129 through pipeline 128, it is circulated back to the second-stage coking zone 107, achieving independent circulation.

[0115] Air is introduced through pipeline 130. Part of this air is heated by electric heater 131 and then enters drying zone 109. The dried gas flows upwards to remove moisture from the catalyst. The dried gas is discharged through pipeline 132, with a portion used as supplementary gas for the first-stage coking zone 105 and the second-stage coking zone 107, and the remainder discharged through pipeline 133. Chlorin is introduced through pipeline 134, mixed with the air from pipeline 130, heated by electric heater 135, and then enters oxychlorination zone 111. The gas in oxychlorination zone flows upwards over the catalyst awaiting generation, undergoing oxychlorination in zone 111, which redisperses the accumulated Pt metal on the catalyst. The oxychlorinated gas is drawn out through pipeline 136, pressurized by booster 137, and then mixed with the supplementary air introduced through pipeline 130 and the chlorinating gas introduced through pipeline 134 before being recycled back to oxychlorination zone 111, achieving independent circulation.

[0116] Part of the air introduced through pipeline 130 is cooled by cooler 138 and then enters cooling zone 113 to cool the catalyst to be generated. The cooling gas discharged from cooling zone 113 is led out through pipeline 139, pressurized by booster 140, mixed with the air introduced through pipeline 130, and circulated back to cooling zone 113 to complete the cycle. Chloride is introduced into the first coking zone 105 and the second coking zone 107 through pipelines 141 and 142, respectively.

[0117] Example 2

[0118] The catalyst to be regenerated was carried out according to the method of Example 1, except that the oxygen content in the regeneration gas of the first coke burning zone was 0.9% by volume, the oxygen content in the regeneration gas of the second coke burning zone was 0.9% by volume, and other conditions were the same as in Example 1.

[0119] Example 3

[0120] The catalyst to be regenerated was carried out according to the method of Example 1, except that the chlorine content in the oxychlorination zone was 0.08% by mass, based on the mass of the catalyst to be regenerated, and other conditions were the same as in Example 1.

[0121] Comparative Example 1

[0122] The spent catalyst was regenerated according to the method of Example 1, wherein the spent catalyst was the same as that in Example 1, being a spent catalyst obtained from the dehydrogenation of low-carbon alkanes. The difference was that...

[0123] The conditions for the first coking process are as follows: the inlet temperature of the regenerated gas is 460℃, the oxygen content in the regenerated gas is 0.9% by volume, the pressure is 0.4MPa, the average residence time is 50min, and the gas-solvent volume ratio is 8000:1.

[0124] The conditions for the second coking process are as follows: the inlet temperature of the regenerated gas is 480℃, the oxygen content in the regenerated gas is 2.5% by volume, the pressure is 0.4MPa, the average residence time is 50min, and the gas-solvent volume ratio is 8000:1.

[0125] No drying zone is set up. Instead, a cooling zone I is set up after the second coking zone. The cooling conditions of the cooling zone I are as follows: the inlet temperature of the cooling gas is 450℃, the oxygen content in the cooling gas is 2.5% by volume, the pressure is 0.4MPa, and the catalyst temperature after cooling is 430℃.

[0126] After cooling, the catalyst enters the oxychlorination zone for oxychlorination under the same conditions as in Example 1. After oxychlorination, the catalyst enters cooling zone II for further cooling. The exhaust gas from the oxychlorination zone is not recirculated; after being discharged, it passes through a dechlorination tank to remove chlorides before being released into the atmosphere. The cooling conditions are: oxygen content in the cooling gas is 21% by volume, inlet gas temperature is 50°C, and catalyst temperature after cooling is 200°C.

[0127] Test case

[0128] The regeneration results of the catalysts in the embodiments and comparative examples of this invention are shown in Table 1. The catalyst color was obtained by direct observation.

[0129] The Pt dispersion of a catalyst refers to the ratio of the number of Pt atoms on the catalyst surface to the total number of Pt atoms on the catalyst.

[0130] Table 1

[0131]

[0132] Note: The gray agent ratio refers to the proportion of gray agent in the total amount of catalyst in the obtained regenerated catalyst.

[0133] As can be seen from the results in Table 1, the method provided by this invention can improve the noble metal dispersion of the low-carbon alkane dehydrogenation catalyst and improve the catalyst regeneration effect.

[0134] 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 low-carbon alkane dehydrogenation catalyst, characterized in that, The method includes: (1) After the catalyst to be generated is first coked in the first coking zone, it is coked a second time in the second coking zone; (2) The product after the second coking is passed through a drying zone, an oxychlorination zone and a cooling zone to obtain a regenerated catalyst; The gases discharged from the first coking zone, the second coking zone, and the oxychlorination zone are each circulated independently. The oxygen content in the regenerated gas in the second-stage coking zone is 2-6% by volume. The regenerated catalyst includes a support and an active component; the active component includes platinum group metals, group IVA metals, alkali metals and chlorine; the inlet pressure of the first-stage coking zone is 1-20 kPa higher than the inlet pressure of the second-stage coking zone; the oxygen content in the regeneration gas of the first-stage coking zone is 0.2-1% by volume.

2. The method according to claim 1, wherein, The gas discharged from the drying zone is divided into gas I and gas II. Gas I is mixed with the first circulating gas discharged from the first coking zone and circulated back to the first coking zone. Gas II is mixed with the second circulating gas discharged from the second coking zone and circulated back to the second coking zone.

3. The method according to claim 1, wherein, The oxygen content in the regenerated gas of the coking zone is 0.5-1% by volume.

4. The method according to any one of claims 1-3, wherein, The conditions for the first coking process include: the inlet temperature of the regeneration gas is 350-600℃; the pressure is 0.1-1MPa; the gas-solvent volume ratio is 2000-20000:1; and the residence time is 10-600min.

5. The method according to claim 4, wherein, The conditions for the first coking process include: the inlet temperature of the regeneration gas is 400-500℃; the pressure is 0.3-0.8MPa; the gas-solvent volume ratio is 5000-10000:1; and the residence time is 30-480min.

6. The method according to any one of claims 1-3, wherein, The conditions for the second coking process include: an inlet temperature of 400-600℃ for the regeneration gas; a pressure of 0.1-1MPa; a gas-solvent volume ratio of 2000-20000:1; and a residence time of 10-600min.

7. The method according to claim 6, wherein, The conditions for the second coking process include: an inlet temperature of 440-550℃ for the regeneration gas; a pressure of 0.4-0.8MPa; a gas-solvent volume ratio of 5000-10000:1; and a residence time of 30-480min.

8. The method according to any one of claims 1-3, wherein, The drying conditions in the drying zone include: the gas temperature at the inlet of the drying zone is 120-600℃; and the oxygen content in the drying gas is 0.1-21% by volume.

9. The method according to claim 8, wherein, The drying conditions in the drying zone include: the gas temperature at the inlet of the drying zone is 400-600℃; and the oxygen content in the drying gas is 5-21% by volume.

10. The method according to any one of claims 1-3, wherein, The oxychlorination conditions in the oxychlorination zone include: a gas temperature of 120-600℃ at the inlet of the oxychlorination zone; and an oxygen content of 3-21% by volume.

11. The method according to claim 10, wherein, The oxychlorination conditions in the oxychlorination zone include: a gas temperature of 400-550℃ at the inlet of the oxychlorination zone; and an oxygen content of 7-21% by volume.

12. The method according to any one of claims 1-3, wherein, The oxychlorination zone also introduces a chlorinating agent, which is chlorine gas and / or an organic chloride.

13. The method according to any one of claims 1-3, wherein, The chlorine content in the oxychlorination zone is 0.02-1% by mass, based on the catalyst cycle mass.

14. The method according to claim 13, wherein, The chlorine content in the oxychlorination zone is 0.1-0.5% by mass, based on the catalyst cycle mass.

15. The method according to claim 12, wherein, The chlorinating agent is mixed with the third circulating gas discharged from the oxychlorination zone and then circulated back to the oxychlorination zone.

16. The method according to any one of claims 1-3, wherein, The cooling conditions of the cooling zone include: the oxygen content in the cooling gas is 0.1-21% by volume; and the gas temperature at the inlet of the cooling zone is 0-200℃.

17. The method according to claim 16, wherein, The cooling conditions of the cooling zone include: the oxygen content in the cooling gas is 5-21% by volume; and the gas temperature at the inlet of the cooling zone is 20-80℃.

18. The method according to any one of claims 1-3, wherein, The inlet pressure of the second-stage coking zone is 1-20 kPa higher than the outlet pressure of the drying zone. And / or, the outlet pressure of the oxychlorination zone is 1-20 kPa higher than the inlet pressure of the drying zone; And / or, the outlet pressure of the cooling zone is 0-20 kPa higher than the inlet pressure of the oxychlorination zone.

19. The method according to claim 1, wherein, The inlet pressure of the first-stage coking zone is 1-10 kPa higher than that of the second-stage coking zone.

20. The method according to claim 18, wherein, The inlet pressure of the second-stage coking zone is 2-10 kPa higher than the outlet pressure of the drying zone. And / or, the outlet pressure of the oxychlorination zone is 2-10 kPa higher than the inlet pressure of the drying zone; And / or, the outlet pressure of the cooling zone is 2-10 kPa higher than the inlet pressure of the oxychlorination zone.

21. The method according to claim 1, wherein, The carrier is an alumina carrier.

22. The method according to claim 21, wherein, The carrier is θ-alumina.

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