PROPANE DEHYDROGENATION METHOD IN A MOVING BED AND REACTION SYSTEM

Abstract

A process method and a reaction system for moving bed propane dehydrogenation conversion, belonging to the field of petrochemical engineering. The method comprises: after preheating, and in the presence of hydrogen, a propane feed gas sequentially passing through reaction zones (2 to 6 zones) of a downflow moving bed partitioned reactor in a countercurrent manner, and then passing through a series of downflow moving bed reactors in a cocurrent manner; under reaction conditions of a temperature of 500-700°C, pressure of 0.01-3 MPa and a volume space velocity of 0.3-5 h⁻¹, contacting and reacting with a spherical catalyst having a diameter of 1.5-2 mm, which is a γ-alumina / θ-alumina composite carrier loaded with platinum, tin, potassium, chlorine and phosphorus, and a conversion gas entering a subsequent unit for separation, to obtain propylene; a coked and deactivated catalyst entering a regenerator, and introducing nitrogen gas containing oxygen and chlorine, to perform coke burning, oxychlorination and reduction regeneration at 500-700°C. The continuous reaction-regeneration process and reaction system of the present invention can improve dehydrogenation conversion efficiency, simplify equipment, reduce coking, energy consumption, investment and land use, and improve the operability and operational stability of the process.

Description

A process and reaction system for moving bed propane dehydrogenation conversion Technical Field

[0001] The present invention relates to a process method and a reaction system for propane dehydrogenation conversion in a moving bed; more specifically, the present invention relates to a process method and a reaction system for implementing a propane dehydrogenation conversion process by using a descending moving bed zoned reactor and a series of descending moving bed reactors; and belongs to the technical field of petrochemical industry. Background Art

[0002] Propylene is an important basic raw material second only to ethylene in the petrochemical field. It can be used to synthesize polypropylene, polyacrylonitrile, acrolein, acrylic acid, propylene oxide, isopropyl alcohol, isopropylbenzene, propylene copolymers, etc., and is widely used in various industries such as materials, medicine, and textiles.

[0003] Currently, the most common technologies for producing propylene include catalytic cracking, steam cracking, olefin cleavage, olefin disproportionation, methanol-to-olefins, and propane dehydrogenation. Propane dehydrogenation is gaining increasing attention due to its advantages such as high yield and good selectivity, and the number of industrialized plants is steadily increasing.

[0004] Industrial propane dehydrogenation methods primarily include the Oleflex process from UOP (Universal Oil Products), the Catofin process from ABB Lummus, the STAR process from Uhde, the PDH process from Linde / BASF, and the FBD process from Snamprogetti / Yarsintez. These processes are described in USP3978150, USP4926005, CA113133048, DE3841800, and GB2177317A. Catalysts include platinum-based and chromium-based catalysts, as described in USP4827066, GB1168342A, USP02956030, and CN113244907A.

[0005] The Oleflex process, a moving-bed continuous regeneration reaction system, achieved industrial production in 1990 and has been applied in most propane dehydrogenation to propylene projects both domestically and internationally. The process boasts continuous operation, uniform load, and high space velocity, achieving propylene yields of up to 85%. (See USP 3584060, USP 3878131, USP 4438238, USP 4595673, USP 4716143, USP 4786265, and USP 4827072.) The Oleflex process utilizes a platinum catalyst that can be recycled through isothermal regeneration, as described in USP 4778942 and USP 6756340.

[0006] CN112074499A discloses a dehydrogenation method and reaction system, in which a moving bed reactor includes a heat exchanger with a heating medium, the catalyst material and the heating medium are not in contact, and more than half of the enthalpy change in at least one reaction zone is provided by the heat exchanger; the hydrocarbon feed and the catalyst are contacted and reacted in at least one reaction zone of the moving bed reactor to be converted into products comprising olefins, alkynes, cyclic hydrocarbons and / or aromatic hydrocarbons.

[0007] CN110452085A discloses a moving-bed C3 / C4 alkane dehydrogenation process. The catalyst flows between reactors in the opposite direction to the reactant flow. The process involves a mixed hydrogen and C3 / C4 alkane feed flowing through a combined heat exchanger and a heating furnace, entering a first-stage reactor, and then flowing sequentially through a second and final reactor in series to form a reactant stream. The catalyst is then regenerated in a regenerator, entering a final reactor, and then flowing sequentially through the second and first reactors in series to form a catalyst stream. Each reactor outlet is equipped with a hydrogen-permeable membrane separator. Compared to existing industrialized processes, this process improves single-pass conversion and selectivity, reduces reaction temperature, saves energy, reduces carbon deposition, extends reactor life, and reduces investment.

[0008] CN116020356A also discloses a method and system for dehydrogenating low-carbon alkanes in a countercurrent moving bed, which includes introducing low-carbon alkanes from the inlet of a dehydrogenation reaction zone to countercurrently contact with a dehydrogenation catalyst; the dehydrogenation reaction zone contains at least two reactors connected in series, so that the gas phase flow can pass through each of the reactors in sequence; obtaining a catalyst to be regenerated from the upstream reactor; regenerating and reducing the catalyst to be regenerated in sequence to obtain a regenerated catalyst; recycling the regenerated catalyst back to the downstream reactor; and introducing a sulfur-containing coking inhibitor into each reactor to ensure smooth operation of the device.

[0009] The method disclosed in CN116693360A involves contacting a low-carbon alkane with a catalyst in a reaction unit in the presence of hydrogen and in the absence of water for dehydrogenation. When the carbon content of the dehydrogenation catalyst at the outlet of an upstream moving bed reactor falls within a range of 1wt% to 1.8wt%, the catalyst enters a regeneration unit for regeneration. The catalyst comprises active components such as platinum, tin, and rare earth elements supported on an alumina carrier, which improves conversion, selectivity, and product yield.

[0010] CN115612519A discloses a novel regeneration method and system for a moving bed low-carbon alkane dehydrogenation catalyst, comprising a catalytic dehydrogenation reaction unit, a dust removal unit, a charcoal burning and chlorination unit, a reduction unit, an activation unit, and an exhaust gas purification unit, which are sequentially connected through pipelines; after the deactivated catalyst is dusted, it flows to the charcoal burning and chlorination unit to remove carbon deposits, and then is sent to the reduction unit for reduction and activation to improve olefin selectivity.

[0011] CN111170821A also discloses a propane dehydrogenation process involving catalyst regeneration and dual-online reactor switching, including a catalytic dehydrogenation process and a catalyst regeneration process. The raw material exchanges heat with the product gas flowing out of the last-stage reactor in a heat exchanger, and then is heated in a heating furnace and enters the reactor. Each reactor stage is equipped with an intermediate heating furnace. The process gas is heated to the reaction temperature in the heating furnace and enters the next-stage reactor. The last-stage reactor is equipped with two reactors, namely an operating reactor and a standby reactor, and the two reactors can be freely switched. The product gas flowing out of the last-stage reactor exchanges heat with the raw material, is then cooled, and then enters a separation system for separation to obtain the final product, propylene. The catalyst to be regenerated from the last-stage reactor is collected in a catalyst collector, elutriated, and charred to obtain the regenerated catalyst. The regenerated catalyst enters each reactor stage in turn to participate in the reaction, achieving recycling.

[0012] CN114570437A also discloses a method for removing sulfur from a catalyst during propane dehydrogenation in a moving bed. Propane is introduced into a reaction zone of the moving bed to contact the propane dehydrogenation catalyst. The propane dehydrogenation reaction is carried out at 580-650°C. The sulfur-containing regenerated catalyst flowing out of the reaction zone enters a regeneration zone, where it is charred and oxychlorinated to obtain a regenerated catalyst. The regenerated catalyst is then sent to a reduction zone, where hydrogen containing 0.02% to 0.8% water vapor is introduced. The regenerated catalyst is reduced and desulfurized at 500-600°C to improve the reaction performance of the catalyst.

[0013] Further improving the performance of the moving-bed dehydrogenation process, including the catalyst, is a key issue in the development of propane dehydrogenation to propylene technology. Existing technologies still suffer from insufficient conversion efficiency, harsh reaction conditions, high operational complexity, uneven catalyst performance, severe coking, high energy consumption, and frequent downtime. Ensuring the full and balanced utilization of the catalyst's catalytic activity in a process operating with multiple moving-bed reactors, as well as effectively suppressing coking and controlling side reactions, are key research areas. Reducing precious metal usage and energy consumption, and simplifying reactors, equipment systems, process steps, and operational complexity are all crucial for reducing costs, facilitating smooth process operation, and improving operability and economic efficiency. Summary of the Invention

[0014] Propane dehydrogenation is a highly endothermic, reversible reaction that increases the number of molecules. High temperatures and low pressures favor the dehydrogenation reaction. The chemical reactions involved primarily include the main propane dehydrogenation reaction, hydrocarbon cracking and coking, and side reactions that generate other products. The typical reaction temperature is around 600°C. Such high temperatures lead to increased propane cracking and deep propane dehydrogenation, reducing propylene selectivity. They also increase carbon accumulation on the catalyst surface, leading to rapid catalyst deactivation, necessitating continuous or ongoing regeneration to restore activity.

[0015] In the propane dehydrogenation process, a moving bed reactor allows for uninterrupted, continuous reaction and regeneration. To maintain the desired conversion rate for propane dehydrogenation, multiple moving bed reactors are often used in series. The catalysts in each reactor (zone) are subject to varying activity levels. The propane dehydrogenation process requires the catalyst and process to maintain stable and efficient conversion performance under demanding reaction conditions, while also ensuring a simple and easy-to-operate reaction-regeneration process. Balancing and maintaining a good match in the catalyst activity of each reactor (zone), coordinating external preheating and internal heating, addressing heat shortages, suppressing coke formation and side reactions, and maintaining good reaction selectivity are crucial for improving and enhancing the conversion efficiency, operability, and smooth operation of the dehydrogenation process.

[0016] The present invention aims to obtain a stable and efficient propane dehydrogenation conversion method. In a moving bed propane dehydrogenation conversion process, the method further balances and promotes the activity of the catalyst to maintain a high conversion rate; solves the problem of insufficient heat and unbalanced heat supply, coordinates the external preheating and internal heat supplementation of multiple moving bed reactors; ensures effective contact between reactants and catalysts, easy transportation, and efficient heat transfer; minimizes the severity of the reaction conversion process, suppresses side reactions and coke formation rate, and improves the operability and operational stability of the process and apparatus.

[0017] Specifically, in order to achieve the above-mentioned purpose of the present invention, the technical solutions and invention contents adopted are as follows:

[0018] The present invention provides a moving bed propane dehydrogenation conversion process, characterized by comprising:

[0019] (1) After the propane feed gas is heated to 300-600°C in a preheating furnace, it enters the reactor from the lower part of the downward moving bed partitioned reactor (2-6 reaction zones) at a hydrogen / hydrocarbon volume ratio of 0.1-6:1, and contacts the catalyst after the reaction in the series downward moving bed reactor from the upper port of the reactor in countercurrent;

[0020] (2) The reacted material coming out of the upper end of the partitioned reactor is heated at 300-500°C and then enters the upper end of the series-connected downward moving bed reactor and comes into contact with the regenerated catalyst from the regenerator entering from the upper port (co-currently);

[0021] (3) The dehydrogenation conversion reaction in the two reactors is carried out at a temperature of 500-680°C, a pressure of 0.01-1 MPa, and a volume space velocity of 0.1-2 h⁻¹, in contact with a 1.5-2 mm diameter alumina pellet catalyst loaded with platinum, tin, potassium, chlorine, and phosphorus. The product gas after the reaction is separated by entering the subsequent device;

[0022] (4) The carbon-deposited and deactivated catalyst from the lower port of the partitioned reactor enters the upper port of the moving bed regenerator, and is introduced with nitrogen containing oxygen and chlorine elements. It is charred and oxychlorinated at 500-700°C, and is reduced by contact with hydrogen at 500-600°C. It then flows out of the lower port of the regenerator and enters the reaction-regeneration process of the next cycle.

[0023] The present invention provides a moving bed propane dehydrogenation conversion process method, characterized in that the catalyst is a high pore volume macroporous -alumina and -alumina composite carrier pellet with a pore diameter of 3 to 25 nanometers, the -alumina / -alumina mass ratio is 1:(0.1 to 10), and the catalyst is loaded with 0.3wt% to 0.6wt% platinum, 0.3wt% to 0.5wt% tin, 0.1wt% to 1.3wt% potassium, 0.3 to 1.5wt% chlorine and 0.1wt% to 0.5wt% phosphorus, based on the total amount of the absolute dry catalyst. The catalyst has a specific surface area of ​​95 to 120 square meters per gram, a pore volume of 0.5 to 0.9 milliliters per gram, a bulk density of 0.5 to 0.7 milliliters per gram, a diameter of 1.6 to 1.8 millimeters, and a crushing strength of 45 to 65 Newtons per pellet.

[0024] The present invention provides a moving bed propane dehydrogenation conversion process method, characterized in that the catalyst regeneration, charring and oxychlorination process is carried out at 510-650° C., and nitrogen with an oxygen content of 0.1% to 8% by volume and a chlorine content of 0.05% to 1.0% by volume is introduced to reduce the carbon content of the regenerated catalyst from 1.2% to 3% by volume before regeneration by charring to a carbon content of 0.01% to 0.2% by volume in the regenerated catalyst after regeneration.

[0025] The process for propane dehydrogenation conversion in a moving bed provided by the present invention is characterized in that the oxygen-containing element comes from oxygen in the air added to the nitrogen, and the chlorine-containing element comes from tetrachloroethylene and / or dichloroethane compounds added to the nitrogen.

[0026] The present invention provides a moving bed propane dehydrogenation conversion process method, characterized in that the reduction process of the regenerated catalyst is to contact with hydrogen containing 0.02% to 0.8% water by volume at 510 to 570° C. for 1 to 6 hours.

[0027] The present invention also provides a reaction system for implementing the moving bed propane dehydrogenation conversion process, characterized in that it comprises a reaction material propane (1), a platinum-tin composite alumina pellet dehydrogenation catalyst, a downward moving bed partitioned reactor (4) in countercurrent contact with the catalyst, a downward moving bed series reactor (8) in parallel (cocurrent) contact with the catalyst, a moving bed regenerator (30), a feed preheating furnace (9) for the partitioned reactor, a feed heating furnace (10) for the series reactor, and a high-temperature heat medium heating furnace for the partitioned reactor. Furnace (11), partitioned reactor partitions (5-7) and heat exchange coils of high-temperature heat medium for supplementary heat and grate plate internal components (29), heat exchangers (3) for propane reaction raw materials (1) and conversion product gas materials (2), catalyst lifting hoppers (12-14), transfer hoppers (15-17), lock hoppers (18-19), catalyst nitrogen sealing tanks (20), material conveying pipelines (27), catalyst conveying pipelines (28), fans, pumps, gas-solid separators, hydrogen separators, dust separators and collectors.

[0028] The reaction system of a moving bed propane dehydrogenation conversion process provided by the present invention is characterized in that the upper parts of the countercurrent downward moving bed partitioned reactor (4), the parallel downward moving bed series reactor (8), and the moving bed regenerator (30) each include a catalyst buffer hopper (21-22), a separation hopper (23), and a sealing leg; and the lower parts each include a lower leg and a catalyst collecting hopper (24-26) and a catalyst flow controller.

[0029] The reaction system of the moving bed propane dehydrogenation conversion process provided by the present invention is characterized in that the high-temperature heat medium in the heat exchange coil (29) of the internal component of the partitioned reactor (4) is selected from molten nitrate, chloride salt and caustic soda, and the operating temperature range is 550 to 900°C.

[0030] The present invention also provides a step of the reaction material flow when implementing the moving bed propane dehydrogenation conversion process method and reaction system, characterized in that: the reaction material flow (1) exchanges heat with the reaction product (2) through the heat exchanger (3), is heated by the preheating furnace (9), enters the reactor from the lower part of the partitioned moving bed reactor (4), and ascends to the reaction zones (5-7) inside the reactor in sequence; the heating furnace (11) heats the high-temperature heat medium in the coil (29) separating the reaction zones, and replenishes the heat required for the dehydrogenation reaction in the reaction zones (5-7) through heat exchange; the reaction conversion product comes out from the upper end of the partitioned reactor (4), is separated from hydrogen by the hydrogen separator, is heated again by the heating furnace (10), and descends from the upper part of the series moving bed reactor (8) into the reactor; the reaction product comes out from the lower part of the reactor, is separated from hydrogen by the hydrogen separator, enters the heat exchanger (3), exchanges heat with the fresh reaction material flow (1), and then enters the subsequent separation device for separation.

[0031] The present invention also provides a step of the catalyst flow when implementing the moving bed propane dehydrogenation conversion process and reaction system, characterized in that: the regenerated catalyst exiting the regenerator (30) is lifted from the regenerated catalyst lifting hopper (12) to the catalyst transfer hopper (15) of the series moving bed reactor (8) by hydrogen; descends through the catalyst buffer hopper (21) into the series moving bed reactor (8), passes through the feed leg and the catalyst collecting hopper (24); enters the catalyst transfer hopper (16) of the partition reactor through the catalyst lifting hopper (14), passes through the feed leg and the buffer hopper of the partition reactor, and then enters the catalyst transfer hopper (16) of the partition reactor. (22), descends in sequence into the reaction zones (7, 6, 5) of the partitioned reactor (4), descends through the down-feed leg into the catalyst collecting hopper (25), passes through the lock hopper (18) and the catalyst lifting hopper (13), enters the catalyst transfer hopper (17), passes through the regenerator separation hopper (23) and the down-feed leg, descends into the regenerator (30) and the regenerated catalyst collecting hopper (26), passes through the down-feed leg and the catalyst cooling flow controller, the regenerated catalyst nitrogen sealing tank (20), and the lock hopper (19), enters the regenerated catalyst lifting hopper (12), thus forming a complete cyclic conveying process of the catalyst material flow.

[0032] The materials, chemicals, and reagents involved in the propane dehydrogenation process and reaction system provided by the present invention, as well as commercially available unit equipment and devices, can be readily obtained through commercial purchase. Conventional chemical operations involved in the propane dehydrogenation process and reaction system of the present invention are well known to those skilled in the art and are used in routine scientific research and production.

[0033] The beneficial effects of the moving bed propane dehydrogenation process and reaction system of the present invention are:

[0034] The present invention adopts a countercurrent downward moving bed zoned reactor and a series parallel (cocurrent) downward moving bed reactor, in combination with a platinum-tin composite alumina dehydrogenation catalyst modified with metal and non-metallic elements and a moving bed regenerator, so that the catalytic activity of the regenerated catalyst in each reactor (zone) is more reasonably distributed, the dehydrogenation conversion and coking rate control are more balanced, the reactor preheating and the heat replenishment in the reactor are more coordinated and sufficient, the preheating temperature can be lowered and the coking of the heating furnace can be reduced, and a high-efficiency, stably operating continuous reaction-regeneration process and reaction system are formed, which improves the propane dehydrogenation conversion efficiency, simplifies the reactor, internal components and device system, reduces shutdowns and tedious maintenance, reduces floor space and investment, and improves the catalyst transportation and process operability, operation stability and economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The content, implementation methods and effects of the present invention will be further described with reference to FIG1 , and other features, purposes and advantages of the present application will become clearer, but the broad interpretation of the present invention will not be limited thereby. FIG1 is a schematic flow diagram illustrating a moving bed propane dehydrogenation process and reaction system of the present invention.

[0036] In Figure 1: 1- raw material propane; 2- product gas; 3- heat exchanger; 4- countercurrent downward moving bed zoned reactor; 5-7- reaction zones of zoned reactor (example of 3 reaction zones); 8- series parallel (cocurrent) downward moving bed reactor; 9- preheating furnace of zoned reactor; 10- feed heating furnace of series reactor; 11- high-temperature heat medium heating furnace; 12-14- catalyst lifting hopper; 15-17- catalyst transfer hopper; 18-19- lock hopper; 20- catalyst nitrogen sealing tank; 21-22- catalyst buffer hopper; 23- regenerator separation hopper; 24-26- catalyst collection hopper; 27- material conveying pipeline; 28- catalyst conveying pipeline; 29; high-temperature heat medium heat exchange coil; 30- moving bed regenerator.

[0037] It should be noted that, for the purpose of simplicity, clarity and ease of description, the flow diagram 1 used to illustrate the present invention only shows the parts most relevant to the invention, and does not list in detail the fans, pumps, catalyst cooling flow controllers, gas-solid separators, hydrogen separators, dust separators, collectors and subsequent separation processes that are also needed in the present invention. However, this does not affect or limit the disclosure and interpretation of the present invention. Modes for Carrying Out the Invention

[0038] The present invention will be further described in detail below with reference to FIG1 and specific implementation methods. It will be understood that the specific implementation methods and examples described herein are only used to explain the relevant invention, rather than to limit the invention. In the absence of conflict, the features in the implementation content may be combined with each other.

[0039] The specific implementation of the moving bed propane dehydrogenation conversion process and reaction system of the present invention is as follows:

[0040] First, referring to the steps and contents disclosed in the Chinese patent applied for and authorized by the inventor (see listed in the examples), the pellet dehydrogenation catalyst of the present invention was prepared according to the contents and calculated amounts of the present invention.

[0041] Propane dehydrogenation reaction process:

[0042] The propane reactant stream (1) exchanges heat with the reaction product (2) through the heat exchanger (3), is heated by the preheating furnace (9), and ascends from the lower part of the partitioned moving bed reactor (4) into the reactor, and ascends through the reaction zones 5, 6, and 7 inside the reactor in sequence; the catalyst that has reacted and partially deposited carbon and exits the lower port of the series reactor enters the catalyst transfer hopper (16) of the partitioned reactor through the catalyst lifting hopper (14), passes through the down-feeding leg and the buffer hopper (22) of the partitioned reactor, and descends in sequence into the reaction zones (7, 6, and 5) of the partitioned reactor (4), and contacts with the ascending propane material in countercurrent to carry out a dehydrogenation conversion reaction, and helps loosen the partitioned catalyst bed, which is beneficial to the downward movement of the pellet catalyst.

[0043] The heating furnace (11) heats the high-temperature heat medium in the coil (29) separating the reaction zones, replenishing the heat required for the dehydrogenation reaction in the reaction zones (5-7) through heat exchange. The grate plate and coil (29) divide the zoned reactor into 2-4 reaction zones. The reaction temperature of each reaction zone is adjusted by the coil (29). Each reaction zone can use the same reaction temperature or a different reaction temperature.

[0044] After the dehydrogenation reaction product comes out from the upper end of the partitioned reactor (4), it is separated from hydrogen by a hydrogen separator, and then heated again by a heating furnace (10). It descends from the upper part of the series moving bed reactor (8) and enters and passes through the reactor. The regenerated catalyst exiting the regenerator (30) is lifted from the regenerated catalyst lifting hopper (12) to the catalyst transfer hopper (15) of the series moving bed reactor (8) by hydrogen. It descends through the catalyst buffer hopper (21) and enters the series moving bed reactor (8), and comes into parallel (co-current) contact with the conversion product gas exiting the partitioned reactor (4) to carry out the dehydrogenation reaction. The catalyst after the parallel (co-current) contact reaction enters the lifting hopper (14) and the partitioned reactor through the lower leg and the catalyst collecting hopper (24).

[0045] After the reaction product comes out from the lower part of the series reactor (8), it is separated from hydrogen by the hydrogen separator, enters the heat exchanger (3) and exchanges heat with the fresh reactant stream (1), and then enters the subsequent separation device for separation to obtain the product propylene.

[0046] Catalyst regeneration process:

[0047] The carbon-deposited and deactivated catalyst to be regenerated after the reaction in the partitioned reactor (4) descends through the downhole leg and enters the catalyst collecting hopper (25); enters the catalyst transfer hopper (17) through the locking hopper (18) and the catalyst lifting hopper (13); descends through the regenerator separation hopper (23) and the downhole leg and enters the regenerator (30) and the regenerated catalyst collecting hopper (26); and enters the regenerated catalyst lifting hopper (12) through the downhole leg and the catalyst cooling flow controller, the regenerated catalyst nitrogen sealing tank (20), and the locking hopper (19) to perform a cyclic reaction-regeneration.

[0048] Through the description of the above specific embodiments of the present invention, the detailed steps and implementation contents of a moving bed propane dehydrogenation process method and reaction system of the present invention are disclosed.

[0049] In the following examples, the composition analysis of the feed gas and the reformed gas was performed using an Agilent 6890N gas chromatograph; various analyses of the catalyst were performed according to the relevant analytical methods in the Petrochemical Analysis Methods (RIPP Test Methods), published by Science Press in 1990; other analytical tests can be found in the National Standard for Test Methods for Petroleum and Petroleum Products, published by China Standards Press in 1989.

[0050] Example

[0051] First, the required platinum-tin composite alumina pellet dehydrogenation catalyst is prepared according to the invention content of the present invention.

[0052] Referring to the preparation steps and methods in the authorized Chinese patent CN113289673B and the disclosed Chinese patent CN114988447A embodiments obtained by the inventor, macroporous α-alumina with high pore volume was prepared; according to the preparation steps and methods in the embodiments of the Chinese patent CN113751080A applied by the inventor, α-alumina was prepared; and referring to the alumina drop ball forming method in the inventor's authorized patent CN108273566B, α-alumina and α-alumina composite carrier beads required by the present invention were prepared.

[0053] According to the preparation steps and methods in the inventor's authorized patent CN108435221B and the disclosed example CN111085199A, combined with the specific requirements for the catalyst in the claims and the invention content of the present invention, the platinum-tin composite alumina pellet dehydrogenation catalyst required by the present invention was prepared.

[0054] The prepared alumina pellet carrier was impregnated with calculated amounts of chloroplatinic acid, tin dichloride, and potassium chloride solution. After drying, the carrier was sprayed with a dilute aluminum phosphate sol and calcined at 580°C for 6 hours to obtain a pellet dehydrogenation conversion catalyst with platinum tin as the dehydrogenation active component and modified with metal and non-metal elements.

[0055] The catalyst contains 0.3 wt% of platinum, 0.4 wt% of tin, 0.9 wt% of potassium, 1.2 wt% of chlorine, and 0.5 wt% of phosphorus based on the total amount of the absolute dry catalyst; the catalyst has a specific surface area of ​​95 square meters per gram, a pore volume of 0.5 milliliters per gram, a mesopore diameter range of 3.9 to 10 nanometers, a bulk density of 0.65 g / ml, and a strength of 55 Newtons per particle.

[0056] A small-scale laboratory test apparatus was used to simulate the moving bed process of the present invention and demonstrate the effectiveness of the process and reaction system of the present invention for propane dehydrogenation. The platinum-tin composite alumina dehydrogenation catalyst prepared above was loaded into the dehydrogenation reaction apparatus. Industrial-grade propane, with a propane content of no less than 96 wt%, was used as the reaction feedstock. Propane and hydrogen were introduced into the reaction apparatus to carry out the conversion.

[0057] The reaction conditions were a propane feedstock: hydrogen volume ratio of 1:0.6, a volumetric space velocity of 0.5 h⁻¹, a pressure of 0.1 MPa, and a temperature of 600°C. To simplify the experimental simulation process, propane feedstock and hydrogen were introduced through the lower ports of the front reactors No. 1 to 3 for 20, 40, and 60 hours, respectively, to induce pre-carbon deposition, simulating the carbon deposition conditions on the catalysts in the three reaction zones of the zoned reactors during actual industrial operation.

[0058] Reactor No. 4, located downstream in the series, uses regenerated catalyst after carbon deposits have been burned to simulate actual industrial operation. Regeneration conditions involve burning the carbon at 600°C with nitrogen containing 5% oxygen by volume, followed by oxychlorination with a chlorinating agent until the carbon monoxide content in the tail gas is less than 0.1% by volume. This is followed by reduction with hydrogen containing 0.1% water by volume at 520°C for two hours. The feedstock enters Reactor No. 4 through its upper port.

[0059] Under the aforementioned reaction and regeneration test conditions, after 100 hours of stable reaction operation, the total propylene yield reached 85%, and the propane single-pass conversion rate reached 27%. Simulations compared the process with an existing, mature, industrially operated moving bed process demonstrated that, while achieving the same conversion results, carbon deposits were reduced by 25% to 35%, energy consumption dropped by 10% to 15%, and the single-pass cycle was extended by 20% to 25%. Furthermore, the number of reactors was reduced from four to two, and the reactor internals were significantly simplified, simplifying operations, reducing equipment investment and floor space, and improving process efficiency.

[0060] Finally, the above description is only a preferred embodiment of the present application and an illustration of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to the technical solutions formed by the specific combination of the above technical features.

[0061] At the same time, it should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the inventive concept; for example, the above-mentioned features and the technical features with similar functions disclosed in this application (but not limited to) are replaced with each other to form a technical solution.

Claims

1. A method for dehydrogenating propane in a moving bed, characterized in that it includes propane feedstock, which is heated in a preheating furnace to 300-600°C, then fed from below into a sectioned descending reactor with a moving bed of reaction zones at a volumetric ratio of hydrogen to hydrocarbon (0.1-6):1, where it contacts countercurrently with a catalyst supplied from above from a sequential descending reactor with a moving bed, the reaction products exiting the top of the sectioned reactor are heated to 300-500°C and fed from above into a sequential descending moving bed reactor, where they come into direct contact with the regenerated catalyst entering from above from the regenerator, the dehydrogenation reaction in both reactors is carried out at a temperature of 500-680°C, a pressure of 0.01-1 MPa and a feed volumetric feed rate of 0.1-2 h -1in contact with a catalyst in the form of balls with a diameter of 1.5-2 mm based on γ-aluminum oxide / θ-aluminum oxide, containing deposited platinum, tin, potassium, chlorine and phosphorus, the reaction product after conversion is sent to a subsequent unit for the separation of propylene, coked deactivated spent catalyst from the bottom pipe of the sectioned reactor is fed from above into a moving bed regenerator, where nitrogen containing oxygen and chlorine is introduced to burn off the coke and oxychlorinate at 500-700°C, and then reduced with hydrogen at 500-600°C, The restored catalyst exits from the bottom of the regenerator and enters the next reaction-regeneration cycle.

2. The dehydrogenation method according to claim 1, characterized in that the catalyst is balls based on γ-aluminum oxide and θ-aluminum oxide with a pore size of 3-25 nm, highly porous, with a large pore volume, with a mass ratio of γ-Al2O3: θ-Al2O3 = 1: (0.1-10), with the following applied, based on an absolutely dry catalyst: 0.3-0.6 wt.% platinum, 0.3-0.5 wt.% tin, 0.1-1.3 wt.% potassium, 0.3-1.5 wt.% chlorine and 0.1-0.5 wt.% phosphorus; the specific surface area of ​​the catalyst is 95-120 m 2 / g, pore volume 0.5-0.9 ml / g, bulk density 0.5-0.7 g / ml, diameter 1.6-1.8 mm, crushing strength 45-65 N / pcs.

3. The dehydrogenation method according to claim 1, characterized in that the regeneration of the catalyst by burning off coke and oxychlorination is carried out at 510-650°C by feeding nitrogen with an oxygen content of 0.1-8 vol.% and chlorine of 0.1-1.0 wt.%, wherein the carbon content in the spent catalyst before regeneration is 1.2-3 wt.%, and after regeneration is reduced to 0.01-0.2 wt.%.

4. The dehydrogenation method according to paragraph 3, characterized in that the oxygen-containing element comes from atmospheric oxygen added to the nitrogen, and the chlorine-containing element comes from compounds of tetrachloroethylene and / or dichloroethane added to the nitrogen.

5. The dehydrogenation method according to claim 1, characterized in that the reduction of the regenerated catalyst is carried out at 510-570°C in contact with hydrogen containing 0.02-0.8 vol.% water for 1-6 hours.

6. A reaction system for implementing the method for dehydrogenating propane in a moving bed according to any one of paragraphs. 1-5, characterized in that it includes propane feedstock, an aluminum-tin bead dehydrogenation catalyst based on aluminum oxide, a descending sectioned reactor with a moving bed for countercurrent catalyst, a descending sequential reactor with a moving bed for cocurrent catalyst, a regenerator with a moving bed, a furnace for preheating the feed of the sectioned reactor, a furnace for heating the feed of the sequential reactor, a furnace for heating the high-temperature coolant of the sectioned reactor, sections of the sectioned reactor and internal devices - heat exchange coils with a high-temperature coolant for heat supply and grate plates, a heat exchanger for propane feedstock and conversion product, catalyst lifting bins, transfer bins, shut-off bins, a nitrogen seal for the catalyst, process pipelines,catalyst transport pipelines, fans, pumps, gas and particulate separators, hydrogen separators, dust separators and collectors, 7. The reaction system according to claim 6, characterized in that the upper part of the descending sectional reactor with a moving bed, the descending sequential reactor with a moving bed and the regenerator with a moving bed contains catalyst buffer bins, separation bins and sealed legs, and the lower part contains unloading legs and collecting bins of the catalyst, as well as catalyst flow controllers.

8. The reaction system according to paragraph 6, characterized in that the high-temperature coolant in the coils of the sectioned reactor is selected from molten nitrates, chlorides and alkalis, the operating temperature range of which is 550-900°C.

9. The reaction system according to paragraphs 1 and 6, characterized in that the stages of movement of the reaction flows include a flow of reaction raw material, which, after heat exchange with the reaction product in the heat exchanger, is heated in a preheating furnace and fed from below into a sectioned reactor with a moving bed, then it rises sequentially inside the reactor through the reaction zones, the furnace heats the high-temperature coolant in the coils separating the reaction zones, and through heat exchange compensates for the heat required for the dehydrogenation reaction in the zones, the conversion product leaving the top of the sectioned reactor, after separation of hydrogen in the hydrogen separator, is again heated in a furnace and fed from the top into a sequential moving bed reactor, The product coming out of the bottom of this reactor, after separation of hydrogen, enters a heat exchanger for heat exchange with fresh feedstock, and is then sent to the subsequent separation unit.