A method and system for dehydrogenation of low carbon alkanes to olefins

Abstract

This invention relates to the field of petrochemical technology, specifically to a method and system for dehydrogenating low-carbon alkanes to olefins. The method includes: (1) introducing low-carbon alkanes into a moving bed reaction zone packed with a dehydrogenation catalyst to undergo a dehydrogenation reaction, obtaining dehydrogenation products, and separating the dehydrogenation products to obtain hydrogen, olefins, and alkanes; (2) introducing the spent catalyst flowing out from the bottom of the moving bed reaction zone into a regenerator for regeneration treatment to obtain a regenerated catalyst, and recycling the regenerated catalyst back to the moving bed reaction zone to participate in the dehydrogenation reaction. Using the method provided by this invention, the conversion rate of low-carbon alkanes can be improved, continuous catalyst circulation can be achieved, and the operating cycle of the unit can be extended.

Description

Technical Field

[0001] This invention relates to the field of petrochemical technology, specifically to a method and system for the dehydrogenation of low-carbon alkanes 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 maturation of shale gas extraction technology has provided the market with a large quantity of high-quality, inexpensive propane and butane. The process of directly catalytic dehydrogenating alkanes to produce propylene and isobutylene is gaining increasing market acceptance due to its economic and environmentally friendly nature.

[0003] The dehydrogenation process for producing low-carbon alkanes is mainly divided into moving bed process and fixed bed process. The fixed bed process has a relatively simple reaction system design, but because the catalyst needs to be regenerated frequently and the switching operation is very frequent, the requirements for the control system, valves and equipment are high.

[0004] Moving bed technology enables continuous catalyst regeneration and recycling, maintaining the catalyst in a high-activity state, significantly improving catalyst activity and ensuring propylene yield. Existing continuous regeneration processes for propane dehydrogenation catalysts have pressure conversion and atmosphere replacement systems at the bottom of the moving bed reaction zone, and pressure conversion and flow control systems at the bottom of the regenerator. The catalyst feeding is a pulsed, discontinuous process, which easily leads to metal fatigue at the regenerator connections and cracking of the regenerator's internal mesh.

[0005] CN112569872A discloses a moving bed system for the dehydrogenation of low-carbon alkanes to produce low-carbon alkanes. 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. Summary of the Invention

[0008] The purpose of this invention is to solve the problems of low conversion rate of low-carbon alkanes and poor catalyst regeneration capacity and coking flexibility in the prior art.

[0009] To achieve the above objectives, a first aspect of the present invention provides a method for dehydrogenating low-carbon alkanes to olefins, the method comprising:

[0010] (1) Low-carbon alkanes are introduced into a moving bed reaction zone packed with a dehydrogenation catalyst to carry out a dehydrogenation reaction, and the dehydrogenation products are separated to obtain hydrogen, olefins and alkanes.

[0011] (2) The catalyst flowing out from the bottom of the moving bed reaction zone is introduced into the regenerator for regeneration treatment to obtain a regenerated catalyst, and the regenerated catalyst is recycled back to the moving bed reaction zone to participate in the dehydrogenation reaction;

[0012] The regenerator includes, along the flow direction of the catalyst to be generated, a buffer zone, a first-stage coking zone, a second-stage coking zone, an oxychlorination zone, a drying zone, and a cooling zone connected in sequence, and the gases in the first-stage coking zone and the second-stage coking zone are circulated independently.

[0013] A portion of the chlorine-containing gas discharged from the air and / or the oxychlorination zone is introduced as Gas I into the first-stage coking zone, and another portion of the chlorine-containing gas discharged from the air and / or the oxychlorination zone is introduced as Gas II into the second-stage coking zone, such that the oxygen content of the regenerated gas in the first-stage coking zone is 0.2-1% by volume, the chlorine content of the regenerated gas in the first-stage coking zone is 0-0.3% by volume, and the oxygen content of the regenerated gas in the second-stage coking zone is 1%-10% by volume, and the chlorine content of the regenerated gas in the second-stage coking zone is 0-0.3% by volume.

[0014] A second aspect of the present invention provides a system for the dehydrogenation of low-carbon alkanes to olefins, the system comprising:

[0015] The moving bed reaction zone is used for the dehydrogenation reaction of low-carbon alkanes;

[0016] The regenerator has a moving bed reaction zone whose bottom is connected to the top of the regenerator via a pipeline. The regenerator, from top to bottom, includes a buffer zone, a first-stage coking zone, a second-stage coking zone, an oxychlorination zone, a drying zone, and a cooling zone. A sealing partition is provided between the first-stage and second-stage coking zones to allow the gases in the first-stage and second-stage coking zones to circulate independently. A chlorine-containing gas circulation pipeline is provided on the oxychlorination zone, and the chlorine-containing gas circulation pipeline is connected to both the first-stage and second-stage coking zones.

[0017] The method provided by this invention can improve the conversion rate of low-carbon alkanes, achieve continuous catalyst circulation, and improve the regeneration capacity and coking flexibility of the catalyst regeneration system. The oxygen concentration in the oxychlorination zone is not limited by the regenerator. At the same time, it can reduce the wear during the catalyst lifting process, improve the problem of filter screen blockage at the reducing gas outlet, and thus extend the operating cycle of the unit. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the process flow of a specific embodiment of the method for dehydrogenating low-carbon alkanes to olefins provided by the present invention.

[0019] Figure 2 This is a schematic flowchart of a specific implementation of the catalyst regeneration gas recycling method in the method for dehydrogenating low-carbon alkane to olefins provided by the present invention.

[0020] Figure 3 This is a schematic diagram of the process flow for the dehydrogenation of low-carbon alkanes to olefins in the prior art.

[0021] Figure 4 This is a schematic flowchart illustrating a specific implementation of catalyst regeneration gas in a prior art method for dehydrogenating low-carbon alkanes to olefins.

[0022] Explanation of reference numerals in the attached figures

[0023] 103. Heating Furnace I 111. Separation Hopper I

[0024] 112. Pressure Transformation and Flow Control Area 113. Buffer Zone

[0025] 114. First stage of charring zone I 115. Second stage of charring zone I

[0026] 116. Oxychlorination Zone I 117. Drying Zone I

[0027] 118. Cooling Zone; 119. Gas Isolation Zone I

[0028] 122. Reduction Tank I; 125. Upper Hopper of Second Reactor II

[0029] 127. Upper hopper of reactor III; 129. Upper hopper of reactor IV

[0030] 134. Electric heater I 141. Dechlorination tank

[0031] 143. Sealing isolation plate; 144. Material discharge leg

[0032] 150. First fan; 151. First cooler

[0033] 153. First electric heater; 158. Second fan.

[0034] 159. Second cooler; 161. Second electric heater

[0035] 165. Heating Furnace I' 173. Atmosphere Converter

[0036] 176. Separating hopper I' 177. First stage coking zone I'

[0037] 178. Second-stage coking zone I' 179. Oxychlorination zone I'

[0038] 180. Drying Zone I' 181. Flow Control Zone

[0039] 182. Gas Isolation Zone I' 185. Reduction Tank I'

[0040] 188. Upper hopper of the second reactor II' 191. Upper hopper of the third reactor III'

[0041] 194. Upper hopper of the fourth reactor IV' 198. Circulating fan

[0042] 199. Cooler I' 201. First Electric Heater'

[0043] 204. Second electric heater' 208. Electric heater I'

[0044] Numbers 132, 133, 136, 137, 138, 139, 140, 145, 147, 148, 152, 154, 156, 157, 160, 162, 195, 196, 197, 200, 202, 203, 205, 206, and 207 are all pipelines. Detailed Implementation

[0045] 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.

[0046] In this invention, unless otherwise stated, "the gas in the first coking zone and the second coking zone circulates independently" means that a portion of the regenerated gas discharged from the first coking zone is circulated back to the first coking zone as the first circulating gas, without going to the second coking zone; the regenerated gas discharged from the second coking zone is circulated back to the second coking zone as the second circulating gas, without going to the first coking zone. That is, the regenerated gas in the first coking zone and the second coking zone will not cross-circulate.

[0047] In this invention, unless otherwise stated, the regeneration gas in the coking zone refers to the gas drawn from the coking zone, mixed with air and / or chlorine-containing gas discharged from the oxychlorination zone, and then recycled back into the coking zone; it can be nitrogen.

[0048] As previously stated, a first aspect of the present invention provides a method for the dehydrogenation of low-carbon alkanes to olefins, the method comprising:

[0049] (1) Low-carbon alkanes are introduced into a moving bed reaction zone packed with a dehydrogenation catalyst to carry out a dehydrogenation reaction, and the dehydrogenation products are separated to obtain hydrogen, olefins and alkanes.

[0050] (2) The catalyst flowing out from the bottom of the moving bed reaction zone is introduced into the regenerator for regeneration treatment to obtain a regenerated catalyst, and the regenerated catalyst is recycled back to the moving bed reaction zone to participate in the dehydrogenation reaction;

[0051] The regenerator includes, along the flow direction of the catalyst to be generated, a buffer zone, a first-stage coking zone, a second-stage coking zone, an oxychlorination zone, a drying zone, and a cooling zone connected in sequence, and the gases in the first-stage coking zone and the second-stage coking zone are circulated independently.

[0052] A portion of the chlorine-containing gas discharged from the air and / or the oxychlorination zone is introduced as Gas I into the first-stage coking zone, and another portion of the chlorine-containing gas discharged from the air and / or the oxychlorination zone is introduced as Gas II into the second-stage coking zone, such that the oxygen content of the regenerated gas in the first-stage coking zone is 0.2-1% by volume, the chlorine content of the regenerated gas in the first-stage coking zone is 0-0.3% by volume, and the oxygen content of the regenerated gas in the second-stage coking zone is 1%-10% by volume, and the chlorine content of the regenerated gas in the second-stage coking zone is 0-0.3% by volume.

[0053] The two coking zones of this invention are completely isolated, with separate gas circulation and independent control of oxygen content and regeneration pressure, which improves regeneration capacity and coking flexibility. Simultaneously, the gas circulation between the coking zone and the oxychlorination zone is separate, and the catalyst flows through the feed leg. The oxygen concentration in the oxychlorination zone is not limited by the coking zone, making operation in the oxychlorination zone more convenient and achieving better oxychlorination results.

[0054] Furthermore, the inventors of this invention discovered during their research that dividing the chlorine-containing gas discharged from the oxychlorination zone into two parts and introducing them into the two coking zones respectively can not only improve the conversion rate of low-carbon alkanes, but also alleviate the accumulation of metals on the catalyst in the coking zone and reduce the amount of chlorinating agent injected.

[0055] Preferably, a portion of the regenerated gas discharged from the coking zone is mixed with gas I as the first circulating gas and then circulated back into the coking zone.

[0056] Preferably, the amount of the first circulating gas and / or the gas I introduced is controlled such that the oxygen content of the regenerated gas in the coking zone is 0.5-1% by volume. The inventors have found that, by adopting this preferred embodiment, higher olefin yields can be obtained.

[0057] Preferably, the amount of the first circulating gas and / or the gas I introduced is controlled such that the chlorine content of the regenerated gas in the coking zone is 0.0003-0.2% by volume.

[0058] Preferably, the regenerated gas discharged from the second-stage coking zone is mixed with gas II as the second circulating gas and then circulated back into the second-stage coking zone.

[0059] Preferably, the introduction amounts of the second circulating gas and gas II are controlled such that the oxygen content of the regenerated gas in the second-stage coking zone is 2-6% by volume. The inventors have found that, in this preferred embodiment, higher olefin yields can be obtained.

[0060] Preferably, the amount of the second circulating gas and the amount of gas II introduced are controlled so that the chlorine content of the regenerated gas in the second-stage coking zone is 0.0003-0.2% by volume.

[0061] Preferably, gas I is a portion of the chlorine-containing gas discharged from the oxychlorination zone, and gas II is another portion of the chlorine-containing gas discharged from the oxychlorination zone.

[0062] It should be noted that the present invention does not have any special requirements for the introduction amount of the first circulating gas, the second circulating gas, gas I and gas II. It is only necessary to ensure that the oxygen content of the regenerated gas in the first coking zone is 0.2-1% by volume and the chlorine content of the regenerated gas is 0-0.3% by volume, and that the oxygen content of the regenerated gas in the second coking zone is 1%-10% by volume and the chlorine content of the regenerated gas is 0-0.3% by volume.

[0063] Preferably, in step (1), a portion of the hydrogen obtained after separation is recycled back to the moving bed reaction zone to participate in the dehydrogenation reaction.

[0064] Preferably, in step (1), the low-carbon alkane is a C3-C5 alkane.

[0065] Preferably, in step (1), the low-carbon alkane is selected from at least one of refinery by-products, shale gas, and associated gas from oil fields.

[0066] Preferably, in step (1), the conditions for the dehydrogenation reaction include at least: a temperature of 550-700℃, a pressure of 0.01-0.5 MPa, a hydrogen-to-hydrocarbon volume ratio of 0.2-2:1, and a volume hourly space velocity of 0.1-10 h⁻¹. -1 .

[0067] More preferably, in step (1), the conditions for the dehydrogenation reaction include at least: a temperature of 600-650°C, a pressure of 0.01-0.2 MPa, a hydrogen-to-hydrocarbon volume ratio of 0.4-0.7:1, and a volume hourly space velocity of 0.3-8 h⁻¹. -1 .

[0068] Preferably, in step (1), the dehydrogenation catalyst includes a support and an active component, wherein the support is an alumina support, more preferably θ-alumina; the active component contains platinum group metals, group IVA metals, alkali metals and chlorine, wherein the alkali metal is preferably potassium.

[0069] Preferably, in step (1), based on the total mass of the carrier, the active component contains 0.1-1% by mass of the platinum group metal element, 0.1-1% by mass of the group IVA metal element, 0.5-2% by mass of the alkali metal element and 0.4-2% by mass of the chlorine element;

[0070] More preferably, in step (1), based on the total mass of the carrier, the active component contains 0.1-1% by mass of platinum, 0.1-1% by mass of tin, 0.5-2% by mass of potassium and 0.5-1.5% by mass of chlorine.

[0071] The method provided by this invention, in conjunction with the aforementioned catalyst that has high conversion rate and high selectivity, can effectively improve the conversion rate of low-carbon alkanes.

[0072] Preferably, in step (2), the carbon content in the catalyst to be generated is 1-5% by mass, more preferably 1-3% by mass.

[0073] Preferably, in step (2), the pressure of the regenerator is 0.1-2 MPa, more preferably 0.3-1.0 MPa.

[0074] Preferably, in step (2), the conditions of the coking zone include at least the following: the inlet temperature of the regeneration gas is 350-600℃, more preferably 400-500℃; and the pressure is 0.1-1.0MPa, more preferably 0.3-1.0MPa.

[0075] Preferably, in step (2), the conditions of the second-stage coking zone include at least: the inlet temperature of the regeneration gas is 400-600℃, more preferably 440-550℃; and the pressure is 0.1-1.0MPa, more preferably 0.4-1.0MPa.

[0076] Preferably, in step (2), the average residence time of the catalyst to be generated in the first coking zone and the second coking zone is 10-600 min, more preferably 30-480 min.

[0077] Preferably, in step (2), the conditions of the oxychlorination zone include at least: an inlet temperature of 120-600°C, more preferably 400-500°C; and an oxygen content of 3-21% by volume, more preferably 7-21% by volume.

[0078] Preferably, in step (2), the conditions of the drying zone include at least: an inlet gas temperature of 120-600°C, more preferably 400-600°C; and an oxygen content in the drying gas of 0.1-21% by volume, more preferably 5-21% by volume.

[0079] Preferably, in step (2), the conditions of the cooling zone include at least: the oxygen content in the cooling gas is 0.1-21% by volume, more preferably 5-21% by volume; and the inlet gas temperature is 0-200°C, more preferably 20-80°C.

[0080] Preferably, in step (2), the oxychlorination zone contains a chlorinating agent, and the chlorinating agent is selected from at least one of chlorine gas and organic chlorides.

[0081] Preferably, in step (2), the method further includes: before introducing the chlorinating agent into the oxychlorination zone, the chlorinating agent is first pressurized by a regeneration chlorine injection pump and heated and vaporized by a steam heating sleeve.

[0082] It should be noted that the chlorinating agent provided by the present invention mixes with the high-temperature gas rising in the drying zone and then passes through the catalyst bed and flows upward.

[0083] As previously described, a second aspect of the present invention provides a system for the dehydrogenation of low-carbon alkanes to olefins, the system comprising:

[0084] The moving bed reaction zone is used for the dehydrogenation reaction of low-carbon alkanes;

[0085] The regenerator has a moving bed reaction zone whose bottom is connected to the top of the regenerator via a pipeline. The regenerator, from top to bottom, includes a buffer zone, a first-stage coking zone, a second-stage coking zone, an oxychlorination zone, a drying zone, and a cooling zone. A sealing partition is provided between the first-stage and second-stage coking zones to allow the gases in the first-stage and second-stage coking zones to circulate independently. A chlorine-containing gas circulation pipeline is provided on the oxychlorination zone, and the chlorine-containing gas circulation pipeline is connected to both the first-stage and second-stage coking zones.

[0086] The system for dehydrogenation of low-carbon alkanes to olefins provided by the present invention enables continuous circulation of the catalyst in the regenerator by adding a buffer zone before the coking zone, thereby mitigating the problem of easy cracking of the mesh inside the regenerator caused by temperature fatigue due to the pulsed flow pattern of the catalyst in existing industrial plants.

[0087] Preferably, the cooling zone includes at least one section of axial bed cooling zone arranged vertically from top to bottom.

[0088] In this invention, unless otherwise stated, the cooling gas enters the regenerator and flows upward to cool the catalyst; the cooler exits from the cooling zone outlet, and after being heated, recirculates to the drying zone. The temperature of the catalyst falling from the cooling zone to the isolation container is no higher than 200°C, preferably no higher than 150°C.

[0089] The system provided by this invention has a cooling zone at the bottom of the drying zone, which can reduce the temperature during the catalyst lifting process, reduce the wear of the catalyst during the lifting process, improve the problem of clogging of the reducing gas outlet filter, and thus extend the operating cycle of the device.

[0090] According to a particularly preferred embodiment of the present invention, the moving bed reaction zone comprises at least two radially moving bed reactors connected in series.

[0091] Preferably, the number of radially moving bed reactors is 4-5.

[0092] Preferably, a heater I is provided in front of each of the radially moving bed reactors.

[0093] It should be noted that in this invention, after heat exchange between C3-C5 raw materials and products, the raw materials are heated to the reaction temperature in the first heating furnace and then enter the first reactor for dehydrogenation reaction. The effluent from the first reactor enters the second heating furnace for heating, and then enters the second reactor. Subsequently, it passes through the third heating furnace, the third reactor, the fourth heating furnace, and the fourth reactor in sequence, until the downstream heating furnace and reactor. The resulting reaction products are heated with the raw materials and then enter the fractionation system. Part of the hydrogen gas from the fractionation is used as a product discharge device, and part of it is recycled to the moving bed reaction zone as circulating hydrogen. The olefins are also used as a product discharge device. The unconverted alkanes are returned to the reaction zone for reprocessing.

[0094] In order to reduce the oxidized catalyst to the reduced catalyst, preferably, a reduction tank is also provided at the top of each radial moving bed reactor.

[0095] Preferably, the gas inlet temperature of the reduction vessel is 350-600℃, and more preferably 400-550℃.

[0096] Preferably, the reduction vessel contains reducing gas, and the hydrogen content in the reduction is 80-100% by volume, preferably 95-100% by volume.

[0097] Preferably, the system further includes:

[0098] A separation hopper, which is connected to the moving bed reaction zone;

[0099] A pressure conversion and flow control zone is provided between the separation hopper and the regenerator to increase the regeneration pressure of the catalyst to be regenerated.

[0100] An isolation zone is provided at the bottom of the regenerator, and the isolation zone is used to convert the oxygen environment into a hydrogen environment.

[0101] This invention places the pressure transformation and flow control area above the regenerator, which can increase the regenerator pressure, thereby increasing the oxygen partial pressure and improving the regeneration capacity of the regenerator.

[0102] According to a particularly preferred embodiment of the present invention, a circulating gas branch I is provided on the coking zone, and the circulating gas branch I includes a first fan, a first cooler and a first heater connected in sequence along the first circulating gas flow direction.

[0103] Preferably, a circulating gas branch II is provided on the second coking zone, and the circulating gas branch II includes a second fan, a second cooler and a second heater connected in sequence along the second circulating gas flow direction.

[0104] The catalyst moves between reactors by gravity and lifting. After the reaction, the spent catalyst flows out from the bottom of the moving bed reaction zone. In this invention, the spent catalyst containing carbon deposits passes through a spent catalyst lifter, a spent catalyst lift pipeline, and a spent catalyst separation hopper. At the top of the separation hopper, the purging gas from the dust removal fan blows a small amount of dust from the catalyst out of the top of the separation hopper and into a dust collector for separation of dust and purging gas. The separated purging nitrogen is pressurized and recycled. The purged catalyst enters the pressure conversion and flow control system under gravity to complete the pressure conversion of the catalyst from the low-pressure reactor to the high-pressure regenerator, and then enters the catalyst regenerator from the top.

[0105] The following combination Figure 1 , Figure 2 , Figure 3 and Figure 4 The technical solutions of the present invention are further explained below, but the present invention is not limited thereto, and those skilled in the art should not understand it as a limitation of the present invention.

[0106] Figure 1 This is a schematic diagram of a specific embodiment of the method for dehydrogenating low-carbon alkanes to olefins provided by the present invention.

[0107] like Figure 1 As shown, the reaction process is as follows: C3-C5 low-carbon alkanes are piped into heating furnace I 103 and heated to the reaction temperature, then enter the first reactor I for dehydrogenation. The effluent from the first reactor I is piped into heating furnace I 103 and heated, then piped into the second reactor II. The effluent from the second reactor II is piped into heating furnace I 103 and heated, then piped into the third reactor III. The effluent from the third reactor III is piped into heating furnace I 103 and heated, then piped into the fourth reactor IV. The product from the fourth reactor IV is piped into the product fractionation system (not shown in the attached figure) for separation.

[0108] The catalyst regeneration cycle is as follows: the catalyst to be regenerated flows out from the bottom of the fourth reactor IV, passes through an elevator, and enters the catalyst separation hopper I 111 via an elevator pipeline. Dust is separated from the catalyst. The washed catalyst enters the pressure switching and flow control zone 112. Under gravity, the catalyst sequentially enters the regenerator's buffer zone 113, the first-stage coking zone I 114, the second-stage coking zone I 115, the oxychlorination zone I 116, the drying zone I 117, and the cooling zone 118. It then enters the gas isolation zone I 119, where the oxygen environment is converted to a hydrogen environment. Finally, it is lifted by an elevator and elevator pipeline to the reduction tank I 122 at the top of the first reactor I. In step 122, the oxidized catalyst is reduced to a reduced catalyst. The reduced catalyst enters the first reactor I to participate in the reaction, and is then lifted by the elevator and the lifting pipeline to the upper hopper 125 of the second reactor II. The catalyst falls from the upper hopper 125 of the second reactor II into the second reactor II. Subsequently, the catalyst passes sequentially through the elevator of the second reactor II, the lifting pipeline, the upper hopper 127 of the third reactor III, the third reactor III, the elevator of the third reactor III, the lifting pipeline, the upper hopper 129 of the fourth reactor IV, the fourth reactor IV, and the elevator of the fourth reactor IV. Finally, it is lifted by the elevator of the fourth reactor IV and the lifting pipeline to the separation hopper I 111 to complete the catalyst circulation.

[0109] Figure 2 This is a schematic flowchart illustrating a specific embodiment of the catalyst regeneration gas recycling process in the method for dehydrogenating low-carbon alkanes to olefins provided by the present invention.

[0110] exist Figure 2 In the process, cooling gas is introduced into cooling zone 118 through pipeline 132 to cool the catalyst to below 200°C. After being cooled by the catalyst, the cooling gas is led out through pipeline 133 and enters electric heater I 134 for heating. Then it enters drying zone I 117 to dry the catalyst. The drying gas moves upward (that is, the drying gas contacts the catalyst in the opposite direction). The chlorinating agent is pressurized by the regeneration chlorine injection pump and heated and vaporized by the steam heating sleeve. It enters oxychlorination zone I 116 through pipeline 136 and mixes with the high-temperature gas rising from drying zone I 117. It passes through the catalyst bed and flows upward. The chlorine-containing gas discharged from the oxychlorination zone is discharged through pipeline 137. Part of it is introduced into the coking zone through pipelines 138 and 139. The remaining part enters dechlorination tank 141 through pipeline 140 to remove chlorides and then is discharged from the system.

[0111] The regenerated gas from the first coking zone is discharged via pipeline 145, a portion of the regenerated gas is discharged from the system via pipeline 147, and the remaining regenerated gas, as the first circulating gas, enters the first blower 150 via pipeline 148, then enters the first cooler 151 for cooling, and then enters the first electric heater 153 via pipeline 152 for heating, before entering the first coking zone I 114 via pipeline 154 for coking. The first coking zone I 114 and the second coking zone I 115 are completely separated by a sealing isolation plate 143, and the catalyst enters the second coking zone I 115 from the first coking zone I 114 via the feed leg 144. The regenerated gas from the second-stage coking zone is discharged through pipeline 155, and part of the regenerated gas is discharged from the system through pipeline 156. The remaining regenerated gas is used as the second circulating gas and enters the second blower 158 through pipeline 157. After being cooled by the second cooler 159, it enters the second electric heater 161 through pipeline 160 for heating, and finally enters the second-stage coking zone I 115 through pipeline 162 for coking.

[0112] Figure 3 This is a schematic diagram of the process flow for the dehydrogenation of low-carbon alkanes to olefins in the prior art.

[0113] like Figure 3 As shown, the reaction process is as follows: low-carbon alkane feedstock enters the heater I'165 via pipeline and is heated, then enters the first reactor I' via pipeline. The effluent from the first reactor I' is discharged via pipeline and enters the heater I'165, then sequentially passes through pipeline, the second reactor II', pipeline, heater I'165, pipeline, the third reactor III', pipeline, heater I'165, pipeline, and the fourth reactor IV'. The product from the fourth reactor IV' is transported to the fractionation system via pipeline (not shown in the attached figure).

[0114] The catalyst flow process is as follows: the catalyst to be generated flows out from the bottom of the fourth reactor IV', passes through the atmosphere converter 173, and converts the hydrogen atmosphere to a nitrogen atmosphere. Under the action of nitrogen, the catalyst is lifted by the elevator and the lifting pipeline to the regenerator separation hopper I'176, where the dust in the catalyst is washed out. Under the action of gravity, the catalyst passes sequentially through the first coking zone I'177, the second coking zone I'178, the oxychlorination zone I'179, and the drying zone I'180 in the regenerator, and then enters the flow control zone 181 and the gas isolation zone I'182. The coked catalyst is then lifted by the hydrogen and the pipeline to the reduction zone. Tank I'185 reduces the oxidized metal to the reduced metal, completing catalyst regeneration. The regenerated catalyst sequentially passes through the first reactor I', the first reactor I' elevator, the elevator line, the upper hopper 188 of the second reactor II', the second reactor II', the second reactor II' elevator, the elevator line, the upper hopper 191 of the third reactor III', the third reactor III', the third reactor III' elevator, the elevator line, the upper hopper 194 of the fourth reactor IV', and the fourth reactor IV'. The catalyst to be regenerated flows out from the bottom of the fourth reactor IV', completing the catalyst circulation.

[0115] Figure 4 This is a schematic flowchart illustrating a specific implementation of catalyst regeneration gas in a prior art method for dehydrogenating low-carbon alkanes to olefins.

[0116] A mixture of air and nitrogen, or air, is supplied through pipeline 207 and heated in electric heater I'208. It then enters drying zone I'180 to dry the catalyst. The drying gas moves upward (i.e., the drying gas contacts the catalyst in reverse). The chlorinating agent is pressurized by the regeneration chlorine injection pump and vaporized by the steam heating sleeve. It then enters oxychlorination zone I'179 through pipeline 206, mixes with the high-temperature gas rising from drying zone I'180, passes through the catalyst bed, and flows upward. The gas from the chlorination zone continues to rise into the coking zone to supply air to the coking zone.

[0117] In this process, the regenerated gas from the first coking zone is discharged through pipeline 195, a portion of the regenerated gas is discharged from the system through pipeline 196, and the other portion of the regenerated gas is used as circulating gas and enters the cooler I'199 through pipeline 197 via circulating fan 198 for cooling. After cooling, a portion of the circulating gas enters the first electric heater '201 through pipeline 200 for heating, and then enters the first coking zone I'177 through pipeline 202; the other portion of the regenerated gas enters the second electric heater '204 through pipeline 203 for heating, and then enters the second coking zone I'178 through pipeline 205.

[0118] The present invention will be described in detail below through examples. In the following examples, unless otherwise specified, all raw materials used are commercially available products.

[0119] Kerosene: purchased from Aladdin Company;

[0120] Fatty alcohol polyoxyethylene ether: AEO-3, product number A304364, purchased from Aladdin Company;

[0121] In the following examples, chlorine gas is used as the chlorinating agent.

[0122] In the following example, the propane single-pass conversion rate is calculated as follows: Propane single-pass conversion rate = (conversion rate × selectivity);

[0123] The method for calculating the relative mass yield of propylene to propane is: relative mass yield of propylene to propane = (mass of propylene produced / mass of alkanes converted) × 100%;

[0124] The calculation method for the amount of propane required to produce 1 ton of propylene is as follows: Amount of propane required to produce 1 ton of propylene = 1 / (Propylene relative to propane mass yield)

[0125] In the absence of the opposite case, the composition of the low-carbon alkanes in the following examples is as shown in Table 1.

[0126] Components Composition / v% <![CDATA[C2H6]]> 1.49 <![CDATA[C3H8]]> 97.68 <![CDATA[C3H6]]> 0.05 <![CDATA[C4H 10 ]]> 0.78

[0127] Preparation Example 1

[0128] This preparation example illustrates the preparation process of dehydrogenation catalyst A.

[0129] Take 27g of aluminum sheet and add 610g of 18% hydrochloric acid solution to dissolve the aluminum sheet, obtaining an aluminum chloride solution (the aluminum chloride content is 4% by mass). Transfer the aluminum chloride solution to a neutralization tank, add 850g of 6% ammonia water, mix evenly at 60℃, and the pH value is 7.5-8.5. The generated aluminum hydroxide is filtered and washed, and 9mL of nitric acid with a volume ratio of 1:1 is added to the filter cake for acidification to obtain a sol.

[0130] Add 40 mL of an aqueous solution containing 30 g of urea and a hydrochloric acid solution containing 32 g of stannous chloride to the sol while stirring at 100 rpm, so that the Sn content in the solution is 0.32% of the dry basis alumina. Stir at 100 rpm for 1 hour to obtain an acidified sol.

[0131] Then, 30g of kerosene and 3g of fatty alcohol polyoxyethylene ether were added dropwise to the acidified sol while stirring at 100rpm. This sol was then dropped into an oil-ammonia column with an oil phase on the top and an ammonia phase on the bottom to form droplets. The oil phase was kerosene, and the ammonia concentration in the ammonia phase was 8% by mass. The wet pellets were cured in the ammonia phase for 1 hour, then removed and rinsed with deionized water. They were dried at 60℃ for 6 hours, dried at 120℃ for 10 hours, calcined in an air stream at 650℃ for 4 hours, and then treated in air with a water vapor content of 5% by volume at 650℃ for 10 hours. Finally, the temperature was raised to 1000℃ for a second calcination for 4 hours to obtain the tin-containing θ-Al2O3 carrier.

[0132] The tin-containing θ-Al₂O₃ support prepared above was placed in an impregnation solution (based on the total mass of alumina on a dry basis, the impregnation solution contains 0.30% by mass of platinum and 2.0% by mass of chlorine) and impregnated at 25°C for 4 hours, with a liquid / solid ratio (impregnation solution / tin-containing θ-Al₂O₃ support) 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 potassium nitrate solution (based on the total mass of alumina on a dry basis, the potassium nitrate solution contains 1.0% by mass of potassium) at 25°C for 4 hours, with a liquid / solid ratio (potassium nitrate solution / calcined solid) 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 then reduced with hydrogen at 550°C for 2 hours to obtain dehydrogenation catalyst A.

[0133] Example 1

[0134] according to Figure 1 The process flow shown uses dehydrogenation catalyst A to dehydrogenate low-carbon alkane to olefins using the low-carbon alkane feedstock shown in Table 1.

[0135] The inlet temperatures of reactors I, II, III, and IV were controlled at 615℃, 636℃, 637℃, and 633℃, respectively, with a hydrogen-to-hydrogen volume ratio of 0.53:1 and a volume hourly space velocity (VHSV) of 2.8 h⁻¹. -1 The inlet pressures of reactors I, II, III, and IV were 0.186 MPa, 0.135 MPa, 0.086 MPa, and 0.039 MPa, respectively, yielding hydrogen, olefins, and alkanes. The specific dehydrogenation reaction results are shown in Table 2.

[0136] according to Figure 1 The process shown involves catalyst recycling and following the instructions. Figure 2 The process shown involves catalyst regeneration gas circulation, with the carbon content in the catalyst to be regenerated being 1.3% by mass and the pressure in the regenerator being 0.4 MPa.

[0137] The conditions in the coking zone 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 chlorine content in the regenerated gas is 0.0005% by volume, the pressure is 0.4MPa, and the average residence time is 50min.

[0138] The conditions in the second-stage coking zone 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 chlorine content in the regenerated gas is 0.0005% by volume, the pressure is 0.4MPa, and the average residence time is 40min.

[0139] The conditions in the oxychlorination zone are: inlet temperature of 490℃, oxygen content of 21% by volume, and chlorinating agent injection rate of 2.7g / h.

[0140] The conditions in the drying zone are: inlet temperature of 550℃ and oxygen content in the drying gas of 21% by volume.

[0141] The conditions in the cooling zone are: oxygen content in the cooling gas is 21% by volume, and the inlet gas temperature is 50℃;

[0142] The gas evacuation rate in the separation hopper is maintained at 2.0 Nm³. 3 / h.

[0143] Example 2

[0144] The dehydrogenation of low-carbon alkanes to olefins was carried out according to the method of Example 1, except that the regenerator pressure was atmospheric pressure.

[0145] The specific dehydrogenation reaction results are shown in Table 2.

[0146] Example 3

[0147] The dehydrogenation of low-carbon alkanes to olefins was carried out according to the method of Example 1, except that the oxygen content in the oxychlorination zone was controlled to be 3% by volume by mixing nitrogen.

[0148] The specific dehydrogenation reaction results are shown in Table 2.

[0149] Example 4

[0150] The dehydrogenation of low-carbon alkanes to olefins was carried out according to the method of Example 1, except that the oxygen content in the coking zone was 0.3% by volume.

[0151] The specific dehydrogenation reaction results are shown in Table 2.

[0152] Example 5

[0153] The dehydrogenation of low-carbon alkanes to olefins was carried out according to the method of Example 1, except that the oxygen content in the second-stage coking zone was 8% by volume.

[0154] The specific dehydrogenation reaction results are shown in Table 2.

[0155] Comparative Example 1

[0156] The dehydrogenation of low-carbon alkanes to olefins was carried out according to the method of Example 1, except that the oxygen content in the second-stage coking zone was 0.9% by volume.

[0157] The specific dehydrogenation reaction results are shown in Table 2.

[0158] Comparative Example 2

[0159] according to Figure 3 The process flow shown, and according to Figure 4 The regenerator and gas circulation process shown herein utilizes dehydrogenation catalyst A and carries out the dehydrogenation of low-carbon alkanes to olefins using the low-carbon alkane feedstocks shown in Table 1. All other conditions are the same as in Example 1. Specific dehydrogenation reaction results are shown in Table 2.

[0160] Table 2

[0161]

[0162] As can be seen from the results in Table 2, the method provided by this invention can improve the conversion rate of low-carbon alkanes, achieve continuous catalyst circulation, reduce wear during catalyst boosting, improve the problem of filter clogging at the reducing gas outlet, and thus extend the operating cycle of the device.

[0163] 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 dehydrogenating low-carbon alkanes to olefins, characterized in that, The method includes: (1) Low-carbon alkanes are introduced into a moving bed reaction zone packed with a dehydrogenation catalyst to carry out a dehydrogenation reaction, and the dehydrogenation products are separated to obtain hydrogen, olefins and alkanes; (2) The unregenerated catalyst flowing out from the bottom of the moving bed reaction zone is introduced into the regenerator for regeneration treatment to obtain a regenerated catalyst, and the regenerated catalyst is recycled back to the moving bed reaction zone to participate in the dehydrogenation reaction; The regenerator includes, along the flow direction of the catalyst to be generated, a buffer zone, a first-stage coking zone, a second-stage coking zone, an oxychlorination zone, a drying zone, and a cooling zone connected in sequence, and the gases in the first-stage coking zone and the second-stage coking zone are circulated independently. A portion of the chlorine-containing gas discharged from the oxychlorination zone is introduced as Gas I into the first-stage coking zone, and another portion of the chlorine-containing gas discharged from the oxychlorination zone is introduced as Gas II into the second-stage coking zone, so that the oxygen content of the regenerated gas in the first-stage coking zone is 0.5-1% by volume, the chlorine content of the regenerated gas in the first-stage coking zone is 0.0003-0.3% by volume, and the oxygen content of the regenerated gas in the second-stage coking zone is 2-6% by volume, and the chlorine content of the regenerated gas in the second-stage coking zone is 0.0003-0.3% by volume.

2. The method according to claim 1, wherein, A portion of the regenerated gas discharged from the first coking zone is mixed with gas I as the first circulating gas and then circulated back to the first coking zone.

3. The method according to claim 2, wherein, The amount of the first circulating gas and / or the gas I introduced is controlled so that the chlorine content of the regenerated gas in the coking zone is 0.0003-0.2% by volume.

4. The method according to claim 1 or 2, wherein, The regenerated gas discharged from the second-stage coking zone is mixed with gas II as the second circulating gas and then circulated back to the second-stage coking zone.

5. The method according to claim 4, wherein, The amount of the second circulating gas and the amount of gas II introduced are controlled so that the chlorine content of the regenerated gas in the second coking zone is 0.0003-0.2% by volume.

6. The method according to any one of claims 1-3, wherein, Gas I is a portion of the chlorine-containing gas discharged from the oxychlorination zone, and gas II is another portion of the chlorine-containing gas discharged from the oxychlorination zone.

7. The method according to any one of claims 1-3, wherein, In step (1), a portion of the hydrogen obtained after separation is recycled back to the moving bed reaction zone to participate in the dehydrogenation reaction.

8. The method according to any one of claims 1-3, wherein, In step (1), the low-carbon alkane is a C3-C5 alkane.

9. The method according to claim 8, wherein, In step (1), the low-carbon alkane is selected from at least one of refinery by-products, shale gas, and associated gas from oil fields.

10. The method according to any one of claims 1-3, wherein, In step (1), the conditions for the dehydrogenation reaction include at least the following: a temperature of 550-700℃, a pressure of 0.01-0.5 MPa, a hydrogen-to-hydrocarbon volume ratio of 0.2-2:1, and a volume hourly space velocity of 0.1-10 h⁻¹. -1 .

11. The method according to claim 10, wherein, In step (1), the conditions for the dehydrogenation reaction include at least the following: a temperature of 600-650℃, a pressure of 0.01-0.2 MPa, a hydrogen-to-hydrocarbon volume ratio of 0.4-0.7:1, and a volume hourly space velocity of 0.3-8 h⁻¹. -1 .

12. The method according to any one of claims 1-3, wherein, In step (1), the dehydrogenation catalyst includes a support and an active component. The support is an alumina support, and the active component contains platinum group metals, group IVA metals, alkali metals, and chlorine.

13. The method according to claim 12, wherein, The carrier is θ-alumina.

14. The method according to claim 12, wherein, The alkali metal element is potassium.

15. The method according to claim 12, wherein, In step (1), based on the total mass of the carrier, the active component contains 0.1-1% by mass of the platinum group metal element, 0.1-1% by mass of the group IVA metal element, 0.5-2% by mass of the alkali metal element and 0.4-2% by mass of the chlorine element.

16. The method according to claim 15, wherein, In step (1), based on the total mass of the carrier, the active component contains 0.1-1% by mass of platinum, 0.1-1% by mass of tin, 0.5-2% by mass of potassium and 0.5-1.5% by mass of chlorine.

17. The method according to any one of claims 1-3, wherein, In step (2), the carbon content in the catalyst to be generated is 1-5% by mass.

18. The method according to claim 17, wherein, The carbon content in the catalyst to be generated is 1-3 by mass.

19. The method according to any one of claims 1-3, wherein, In step (2), the conditions of the coking zone include at least the following: the inlet temperature of the regeneration gas is 350-600℃; and the pressure is 0.1-1.0MPa.

20. The method according to claim 19, wherein, The conditions for the coking zone include at least the following: the inlet temperature of the regenerated gas is 400-500℃.

21. The method according to claim 19, wherein, The conditions for the charred zone include at least the following: pressure of 0.3-1.0 MPa.

22. The method according to any one of claims 1-3, wherein, In step (2), the conditions of the second-stage coking zone include at least the following: the inlet temperature of the regeneration gas is 400-600℃; and the pressure is 0.1-1.0MPa.

23. The method according to claim 22, wherein, The conditions for the second-stage coking zone include at least the following: the inlet temperature of the regenerated gas is 440-550℃.

24. The method according to claim 22, wherein, The conditions for the two-stage coking zone include at least the following: pressure of 0.4-1.0 MPa.

25. The method according to any one of claims 1-3, wherein, In step (2), the average residence time of the catalyst to be generated in the first coking zone and the second coking zone is 10-600 min.

26. The method of claim 25, wherein, In step (2), the average residence time of the catalyst to be generated in the first coking zone and the second coking zone is 30-480 min.

27. The method according to any one of claims 1-3, wherein, In step (2), the conditions of the oxychlorination zone include at least: an inlet gas temperature of 120-600°C and an oxygen content of 3-21% by volume.

28. The method according to claim 27, wherein, In step (2), the conditions of the oxychlorination zone include at least the following: the inlet gas temperature is 400-500℃.

29. The method according to claim 27, wherein, In step (2), the conditions of the oxychlorination zone include at least: an oxygen content of 7-21% by volume.

30. The method according to any one of claims 1-3, wherein, In step (2), the conditions of the drying zone include at least: the inlet gas temperature is 120-600℃; and the oxygen content in the drying gas is 0.1-21% by volume.

31. The method according to claim 30, wherein, In step (2), the conditions of the drying zone include at least the following: the inlet gas temperature is 400-600℃.

32. The method according to claim 30, wherein, In step (2), the conditions of the drying zone include at least the following: the oxygen content in the drying gas is 5-21% by volume.

33. The method according to any one of claims 1-3, wherein, In step (2), the conditions of the cooling zone include at least: the oxygen content in the cooling gas is 0.1-21% by volume; and the inlet gas temperature is 0-200℃.

34. The method according to claim 33, wherein, In step (2), the conditions of the cooling zone include at least the following: the oxygen content in the cooling gas is 5-21% by volume.

35. The method according to claim 33, wherein, In step (2), the conditions of the cooling zone include at least the following: the inlet gas temperature is 20-80°C.

36. The method according to any one of claims 1-3, wherein, In step (2), the oxychlorination zone contains a chlorinating agent, and the chlorinating agent is selected from at least one of chlorine gas and organic chlorides.

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