CN105585400B - A kind of method by low-carbon alkanes preparing low-carbon olefins - Google Patents

Abstract

The invention discloses a method for producing low-carbon olefins from low-carbon alkanes. The method comprises: reacting low-carbon alkanes in a fluidized bed reactor in the presence of a dehydrogenation catalyst to prepare low-carbon olefins; After entering the fluidized bed regenerator through the lock hopper for regeneration, it is circulated back to the reactor through the lock hopper. In the method of the present invention, compared with the fixed bed and moving bed technology, the activity of the catalyst is more stable, and because a plurality of reactors and intermediate heaters do not need to be arranged, the construction and operation costs of the device are reduced, and due to the reaction, burning Regeneration and other processes are carried out in different separate areas. By using the lock hopper, the operating pressure of the reactor and regenerator can be flexibly adjusted, completely avoiding the contact of hydrogen-containing gas flow and oxygen-containing gas flow, which is safer and more reliable. By adopting the method of the invention, not only is the operation process simple and continuous, but also low investment, large processing capacity and high safety can be achieved.

Description

A method for preparing low-carbon olefins from low-carbon alkanes

technical field

The invention relates to a method for preparing low-carbon olefins from low-carbon alkanes.

Background technique

Light olefins are basic feedstocks for the production of petrochemicals and are used in the production of products such as polypropylene, methyl tert-butyl ether, high-octane gasoline components, alkylate and rubber. Although demand for these products is growing rapidly, access to light olefins is limited and large imports are required. Most of China's oilfield gas contains more than 10v% C ₂ ⁺ alkane resources, and in recent years, the exploitation and utilization of shale gas resources has gradually been put on the agenda. Therefore, with the vigorous exploration and exploitation of shale gas resources, it can be expected that the sources and production of low-carbon alkanes will be very abundant. Therefore, it is very important to vigorously develop low-carbon alkane dehydrogenation technologies other than catalytic cracking and steam cracking by-product light olefins.

The reaction of dehydrogenation of low-carbon alkanes to produce low-carbon olefins is an endothermic reaction, and there is a thermodynamic equilibrium. High temperature is conducive to the dehydrogenation reaction. In order to achieve a certain conversion rate and selectivity, the reaction also needs a suitable catalyst. The catalyst needs to ensure high raw material conversion rate and target product selectivity, and should minimize side reactions such as isomerization, cracking, polymerization and aromatization, which are determined by the composition and structure of the catalyst.

There are too many catalyst formulations for dehydrogenation of light alkanes to produce light olefins, such as noble metal catalyst systems, transition metal oxides and composite metal oxide systems, heteropolyacid catalyst systems and molecular sieve catalyst systems. Several patents describe catalysts using chromium oxide as an active component or cocatalyst, such as US 2956030 and US 2945823. Many patents such as US4056576 disclose the use of catalysts containing gallium oxide for alkane dehydrogenation. US 4914075 discloses a method for alkane dehydrogenation reaction using a catalyst containing noble metal platinum and gallium oxide, and describes that the regenerated catalyst needs to be chlorinated to redistribute the active metal components. GB 2162082A discloses a chromium oxide/alumina catalyst for catalytic dehydrogenation of C3-C5 alkanes; the synthesis method of the catalyst adopts an equal-volume impregnation method, which is different from impregnation of an alumina support in an excess chromium solution; according to the patent As introduced in the examples, the alkane conversion rate and the corresponding olefin selectivity of the catalyst synthesis method are greatly improved.

At present, the low-carbon alkane dehydrogenation processes that have been industrialized include Lummus's Catofin process, UOP's Oleflex, Phillips' STAR process, and Italy's Snamprogetti's FBD-4 process. However, at present, there are few devices in my country for the dehydrogenation of low-carbon alkanes in industrial production. The reason is that the investment in foreign technology is high and the production enterprises have concerns about the technical service guarantee in the later stage. Therefore, it is a good way out to develop a new technology for producing low-carbon alkenes by dehydrogenating low-carbon alkanes.

The Catofin process of Lummus uses 4 sets of fixed-bed reactors arranged side by side, and the catalyst is chromium oxide/Al ₂ O ₃ . When the raw material of this process is isobutane, the conversion rate of isobutane reaches 60% and the selectivity of isobutene is greater than 90%. , is the highest yield of target olefins in the isobutane dehydrogenation process so far; the reaction and regeneration of this process are carried out intermittently, that is, during the operation of the device, some reactors carry out the reaction process, and some reactors carry out the catalyst regeneration process , it can be seen that the efficiency of the device is reduced. UOP's Oleflex process uses 3 sets of moving bed reactors in series and precious metal catalyst Pt/Al ₂ O ₃ . The process includes three parts: reaction, continuous catalyst regeneration and product recovery. The reaction temperature is about 650°C. US 3978150 discloses a moving bed alkane dehydrogenation process. The advantage of the Oleflex process is that the reactor is operated continuously, the reaction does not need to be stopped for catalyst regeneration, and the total selectivity of converting isobutane to isobutene can reach 91% to 93%, but the investment of the process equipment is relatively large. The former Soviet Union used aluminum chromic acid catalyst and ebullating bed process to dehydrogenate isobutane (and n-butane or a mixture of isobutane and n-butane). This method has a good effect, and the conversion rate of isobutane is 50% to 55%. , The selectivity of converting to isobutene is 82%～86%.

Summarizing the existing patent and non-patent literature, it can be concluded that fixed bed dehydrogenation and moving bed dehydrogenation have their own characteristics and shortcomings. The fixed bed process is a cycle operation of multiple fixed bed reactors, which are frequently switched between the reaction and regeneration processes; each reactor in this process is intermittently operated, so in order to achieve continuous feeding operation, multiple reactors are used at the same time; The main disadvantage of this process is that the operating conditions of the reactor change frequently in the oxidation and reduction environment, and the temperature change of the reactor is very complicated; another concern is that the inlet temperature of the reactants passing through the fixed bed is higher than the outlet temperature. The moving bed process uses multiple moving bed reactors, in which the catalyst slowly flows downward in the reactor; the heat required for the reaction is provided by multiple intermediate heating furnaces; the regenerated catalyst is sent to the first reactor, and then sequentially Flow to the last reactor; the problem with this process is that multiple reactors and intermediate heating furnaces are also required, and the equipment investment is relatively large. Another potential problem is how to maintain the stability of the catalyst activity in each reactor.

In order to reduce investment, improve the continuity of the process and the stability of the catalyst activity, a possible solution is to use a process similar to fluid catalytic cracking (FCC) to carry out the dehydrogenation of light alkanes to produce light olefins. That is, a reactor and a regenerator are used to realize continuous reaction-regeneration operation. However, if this idea is adopted, there will be two major problems to be solved: first, since the reactor is a hydrogen atmosphere (dehydrogenation reaction will produce hydrogen), and the regenerator is an oxygen-containing atmosphere (catalyst burnt regeneration requires oxygen) , the gas flow of the reactor and regenerator must be well isolated to ensure process safety; second, when using one reactor, to achieve the same throughput as the fixed bed or moving bed process, the size of the reactor needs to be increased , which will also increase investment and cost.

Both EP0894781 A1 and US7235706 B2 disclose a method for producing light olefins by dehydrogenating corresponding alkanes. The method uses a dense-phase fluidized bed reaction-regeneration system with a reaction temperature of 450-800°C and a reaction pressure of 0.1-3 atm , the volumetric space velocity is 100～1000h ^-1 , the catalyst composition used in the two patents is different, the catalyst component of the former is chromium oxide, tin oxide, potassium oxide, the carrier is alumina modified by silica, while the catalyst group of the latter Divided into gallium oxide, metallic platinum, and potassium oxide, the carrier is also silica-modified alumina; the catalyst after carbon deposition is regenerated in a dense-phase fluidized bed; transfer between devices. The problem that the method of these two pieces of patents exists is: the reactor and the reductor that is used for the reduction of the unborn catalyst is a reducing atmosphere (hydrogen atmosphere), and the burnt regeneration of the regenerator is an oxygen-containing atmosphere, and the two are not well integrated. In addition, the reactor and the regenerator are connected through a U-shaped tube, and the operating pressure of the reactor and the regenerator is the same, and the operating pressure of the reactor and the regenerator cannot be flexibly adjusted.

Contents of the invention

The purpose of the present invention is to provide a method for producing low-carbon olefins from low-carbon alkanes, which can overcome the problems in the production of low-carbon olefins by using a fluidized bed reaction-regeneration system, and can ensure the safety of the process on the one hand. The further aspect is that the throughput of the device can be increased under the same reactor size.

In order to achieve the above object, the present invention provides a method for producing lower olefins from lower alkanes, the method comprising: continuously contacting the preheated lower alkanes with a dehydrogenation catalyst in a fluidized bed reactor and Dehydrogenation reaction occurs under dehydrogenation conditions to produce oil gas rich in low-carbon olefins and carbon-deposited catalyst; the oil gas is separated from the catalyst, and the separated oil and gas are sent to the product separation and recovery system, and the catalyst is removed from the The reactor is continuously drawn; after the spent catalyst drawn from the reactor is transported to the spent catalyst receiver, it is then transported to the spent catalyst feed tank through a lock hopper, and then transported from the spent catalyst feed tank to the fluidized bed The regenerator, and regenerate the coke in the regenerator under an oxygen-containing atmosphere to obtain the regenerated catalyst; after the regenerated catalyst is continuously drawn from the regenerator to the regenerated catalyst receiver, it is then transported to the regenerated catalyst feed tank through a lock hopper, and continuously returned to the reactor from the regenerated catalyst feed tank.

Preferably, the method further includes: reducing the regenerated catalyst delivered to the regenerated catalyst feed tank under a reducing atmosphere to obtain a reduced catalyst, and then continuously returning the reduced catalyst to the reactor.

Preferably, the lower alkanes are one or more selected from ethane, propane, isobutane, n-butane, n-pentane and isopentane.

Preferably, the low-carbon alkanes are at least one selected from natural gas condensate, natural gas liquid, catalytically cracked liquefied gas, oilfield gas condensate, and shale gas condensate.

Preferably, the fluidized bed reactor is a bubbling fluidized bed reactor or a turbulent fluidized bed reactor.

Preferably, the fluidized bed reactor has built-in baffles arranged in layers.

Preferably, the built-in baffle is a plate grid, and a layer of plate grid is installed every 20 to 150 cm, and the distance from the bottom surface of the lowermost panel grid to the top surface of the uppermost panel grid is the reactor 20% to 70% of the total height of the internal space.

Preferably, the oil gas and the spent catalyst are separated by a metal sintered filter.

Preferably, wherein the dehydrogenation catalyst contains an active component and a carrier; the active component is metal platinum or chromium oxide, and the carrier is aluminum oxide; based on the total weight of the catalyst, the content of the metal platinum is 0.01% to 1.0% by weight, or the content of the chromium oxide is 1.0% to 30% by weight, and the content of the carrier is a balance amount.

Preferably, the conditions of the dehydrogenation reaction are: reaction temperature 500-700°C, reaction pressure 0.1-3MPa, volume space velocity of light alkanes 100-2000 hours ^-1 , catalyst residence time 1-30 minutes.

Preferably, the conditions of the dehydrogenation reaction are: reaction temperature 530-600°C, reaction pressure 0.4-2.0 MPa, volume space velocity of light alkanes 200-500 hours ^-1 , catalyst residence time 3-8 minutes.

Preferably, the conditions for charred regeneration are: temperature is 550-750°C, pressure is 0.1-0.5MPa, catalyst residence time is 5-60 minutes; the oxygen-containing atmosphere is diluted with air and nitrogen Air, or oxygen-enriched gas is used as the fluidizing medium.

Preferably, the reduction treatment conditions are as follows: temperature is 500-600°C, pressure is 0.4-2.0 MPa, catalyst residence time is 1-10 minutes; the reduction atmosphere is a hydrogen-containing reducing stream as the fluidized Medium; the reducing stream is free of oxygen and contains 50-100% by volume of hydrogen and contains 0-50% by volume of refinery dry gas.

Preferably, the method further includes: controlling the reaction pressure in the reactor to be at least 0.3 MPa higher than the regeneration pressure in the regenerator.

Preferably, wherein the oil and gas contained in the spent catalyst stream in the spent catalyst receiver is stripped with hydrogen to said reactor.

Preferably, the method further includes: returning the unreacted low-carbon alkanes separated by the product separation and recovery system to the reactor as a raw material.

Compared with the method for producing low-carbon olefins from low-carbon alkanes of the present invention, the main advantages are as follows:

1. The carbon-deposited catalyst can be continuously transferred from the reactor to the regenerator for regeneration, and the catalyst activity in the fluidized bed reactor is basically stable, which is different from the fixed bed and moving bed processes;

2. The use of fluidized reaction-regeneration system eliminates the use of multiple reactors and intermediate heaters, which can greatly reduce construction and operation costs compared with fixed bed and moving bed processes;

3. The heat required for the dehydrogenation reaction is directly transferred from the hot regenerated catalyst to the reactants, and the strong mixing of gas and solid avoids the occurrence of hot spots such as in fixed bed operation;

4. More importantly, through the use of the lock hopper, the reducing atmosphere (hydrogen atmosphere) of the reactor and the regenerated catalyst feed tank for the reduction of the regenerated catalyst can be well isolated from the oxygen-containing atmosphere of the burnt regeneration of the regenerator , which can ensure the safe operation of the process;

5. Furthermore, through the use of the lock hopper, the operating pressure of the reactor and the regenerator can be flexibly adjusted, that is to say, the operating pressure of the reactor can be increased while maintaining the normal or low pressure operation of the regenerator , so that the throughput of the device can be increased without increasing the size of the reactor.

Other features and advantages of the present invention will be described in detail in the following detailed description.

Description of drawings

The accompanying drawings are used to provide a further understanding of the present invention, and constitute a part of the description, together with the following specific embodiments, are used to explain the present invention, but do not constitute a limitation to the present invention. In the attached picture:

Fig. 1 is a schematic flow sheet of the method for producing low-carbon olefins from low-carbon alkanes according to a specific embodiment of the present invention;

Fig. 2 is a schematic flow sheet of the method for producing low-carbon olefins from low-carbon alkanes according to a further embodiment of the present invention;

Fig. 3 is a plan view and a front view of an embodiment of the built-in baffle (ie, the panel grill) in Fig. 2 .

Explanation of reference signs

1 Fluidized bed reactor 2 Fluidized bed regenerator 3 Spent catalyst receiver

4 Lock Hopper 5 Spent Catalyst Feed Tank 6 Regenerated Catalyst Receiver

7-line 8-line 9-line 10-line 11-line 12-line

13 pipeline 14 pipeline 15 control valve 16 control valve 17 control valve

18 Control valve 19 Control valve 20 Control valve 21 Pipeline 22 Pipeline

23 pipeline 24 pipeline 25 pipeline 26 pipeline 27 pipeline

28 pipeline 29 pipeline 30 pipeline 31 pipeline

40 regenerated catalyst feed tank 41 pipeline 42 pipeline 50 plate grid

detailed description

Specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments described here are only used to illustrate and explain the present invention, not to limit the present invention.

The invention provides a method for preparing low-carbon alkanes from low-carbon alkanes, the method comprising: continuously contacting the preheated low-carbon alkanes with a dehydrogenation catalyst in a fluidized bed reactor and dehydrogenation under dehydrogenation conditions Dehydrogenation reaction, producing oil and gas rich in low-carbon olefins and carbon-deposited spent catalyst; separating the oil and gas from the spent catalyst, sending the separated oil and gas to the product separation and recovery system, and continuously leading the spent catalyst from the reactor ; After the spent catalyst drawn from the reactor is delivered to the receiver of the spent catalyst, it is delivered to the spent catalyst feed tank through a lock hopper, and then delivered to the fluidized bed regenerator from the spent catalyst feed tank, and In the regenerator, charred regeneration is carried out in an oxygen-containing atmosphere to obtain a regenerated catalyst; after the regenerated catalyst is continuously drawn from the regenerator to the regenerated catalyst receiver, it is then transported to the regenerated catalyst feed tank through a lock hopper, and the regenerated catalyst is fed into the regenerated catalyst The bucket is continuously returned to the reactor.

Those skilled in the art can understand that, although there may be a situation in which the active components are partially oxidized after the spent catalyst is burnt and regenerated by the regenerator, hydrogen will be produced due to the alkane dehydrogenation reaction, and the burnt regenerated catalyst Even without reduction treatment, it can still undergo dehydrogenation reaction while being reduced after returning to the reactor. However, in order to better improve the activity of the catalyst, preferably, the method of the present invention also includes: after the regenerated catalyst drawn from the regenerator is transported to the regenerated catalyst feed tank through a lock hopper, reduction treatment is carried out under a reducing atmosphere, A reduced catalyst is obtained which is then continuously returned to the reactor.

According to the present invention, the low-carbon alkanes can be C2～C5 alkanes or their mixtures, such as one or more selected from ethane, propane, isobutane, n-butane and isopentane, It can also be at least one selected from natural gas condensate, natural gas liquid, catalytic cracking liquefied gas, oilfield gas condensate and shale gas condensate, and can also be industrial or natural low-carbon alkane monomers from other sources or a mixture.

According to the present invention, the described fluidized bed reactor is well known to those skilled in the art, and can be a bubbling fluidized bed reactor or a turbulent fluidized bed reactor, or other fluidized bed reactors such as ebullating fluidized bed reactors. A fluidized bed reactor commonly used in industry. The fluidized bed reactor is preferably a bubbling fluidized bed reactor or a turbulent fluidized bed reactor, more preferably a bubbling fluidized bed reactor.

According to a specific embodiment of the present invention, built-in baffles arranged in layers may be arranged inside the fluidized bed reactor to prevent uneven mixed flow of oil gas and/or catalyst, so that oil gas and/or catalyst can be mixed in a A plug-flow state is reacted through the reactor to increase the conversion rate of low-carbon alkanes and the selectivity of the required low-carbon olefins; the built-in baffle can be a plate grid, and the plate grid can be used every 20 to 150cm One layer is installed, preferably 50 to 100 cm, and the distance from the bottom surface of the lowermost panel grille to the top surface of the uppermost panel grille can be 5% to 80% of the total height of the reactor internal space , preferably 20% to 70%, more preferably 30% to 50%; the material of the plate grid can be selected from the materials used in the catalytic cracking regenerator gas distributor or the large-pore distribution plate, and the grid shape can be Wave-shaped and other shapes, the grid has evenly arranged small or large holes for catalysts and gases to pass through regularly.

In order to separate the oil gas produced after the reaction in the reactor from the spent catalyst, a traditional cyclone separator can be used, which is well known to those skilled in the art, and will not be described in detail in the present invention.

According to a preferred embodiment of the present invention, the oil gas and the spent catalyst can also be separated by using a metal sintered filter; the metal sintered filter is a known porous material, which can effectively Solid particles or powders are separated from gas components and are robust. The present invention has no special limitation on the type and structure of the metal sintered filter, as long as it can effectively separate the oil gas from the spent catalyst, so no further description is given. By using metal sintered filter, you can save investment, simplify operation, and the separation effect is better than cyclone separator.

According to the present invention, the dehydrogenation catalyst can be a conventional alkane dehydrogenation catalyst well known to those skilled in the art, and the present invention has no special limitation thereto. In order to meet the operating requirements of fluidized bed reactors and regenerators, the shape of the dehydrogenation catalyst is generally microspheres. The dehydrogenation catalyst generally contains active components and a support. According to a specific embodiment of the present invention, for example, the active component can be metal platinum or chromium oxide, and the support can be alumina; the alumina is preferably γ-Al ₂ O ₃ and θ-Al _{2 O3} or a mixture of the two; based on the total weight of the catalyst, the content of the metal platinum can be 0.01% to 1.0% by weight, preferably 0.05% to 0.2% by weight, or when the active component is chromium oxide The content of the chromium oxide may be 1.0 wt% to 30 wt%, preferably 8.0 wt% to 20 wt%, and the content of the carrier is a balance amount (ie, the total weight is 100%). According to a specific embodiment of the present invention, the dehydrogenation catalyst may or may not contain iron oxide and/or tin oxide, and may or may not contain an alkali metal oxide or an alkaline earth metal oxide; the total weight of the catalyst is Based on the standard, the content of iron oxide and/or tin oxide can be 0% by weight to 5.0% by weight, preferably 0.2% by weight to 2% by weight; the content of alkali metal oxide or alkaline earth metal oxide can be 0% by weight to 5.0% by weight %, preferably 0.5% to 2% by weight, the alkali metal oxide can be, for example, potassium oxide, and the alkaline earth metal oxide can be, for example, magnesium oxide.

According to the present invention, the process conditions of the dehydrogenation reaction are well known to those skilled in the art, and the present invention has no special limitation thereon. For example, the conditions for the dehydrogenation reaction may be: reaction temperature 500-700°C, reaction pressure 0.1-3MPa, light alkane volume space velocity 100-2000 hours ^-1 , catalyst residence time 1-30 minutes; preferred dehydrogenation The reaction conditions may be: reaction temperature 530-600°C, reaction pressure 0.4-2.0 MPa, light alkanes volume space velocity 200-500 hours ^-1 , catalyst residence time 3-8 minutes.

According to the present invention, the conditions for char regeneration are well known to those skilled in the art, and the present invention has no particular limitation thereon. For example, the conditions for charred regeneration may be: temperature 550-750°C, pressure 0.1-0.5 MPa, catalyst residence time 5-60 minutes; the oxygen-containing atmosphere may be air diluted with air or nitrogen , or oxygen-enriched gas as the fluidizing medium. The preferred regenerator fluidizing medium is air or air diluted with nitrogen. If necessary, fuel gas such as refinery dry gas can be supplemented to increase the temperature of the catalyst bed in the regenerator.

As mentioned above, preferably, the method of the present invention may also include: transporting the regenerated catalyst drawn from the regenerator to the regenerated catalyst feed tank through a lock hopper, and performing reduction treatment under a reducing atmosphere to obtain a reduced catalyst, so that The oxidized high-valence metal oxides in the catalyst are reduced to low-valence active dehydrogenation components, and then the reduced catalyst is continuously returned to the reactor. The conditions of the reduction treatment can be determined according to the conditions of the catalyst used, which is well known and understood by those skilled in the art, and the present invention does not need to describe it in detail. For example, the conditions of the reduction treatment may be: the temperature is 500-600° C., the pressure is 0.4-2.0 MPa, and the residence time of the catalyst is 1-10 minutes; the reduction atmosphere may be a reducing stream containing hydrogen as the fluidized Medium; the reducing stream may be substantially free of oxygen and contain 50-100 volume percent hydrogen, and may contain 0-50 volume percent refinery dry gas. In addition, when a catalyst with platinum as the active component is used, the catalyst after long-time reaction may need a chlorination renewal process after being regenerated and burnt to redistribute the platinum active center. At this time, the regenerated catalyst can be fed into The tank is used as a chlorination processor.

In the fluidized bed process for producing light olefins from light alkanes, when only one reactor is used, and the reactor is operated at normal pressure or low pressure like the regenerator, to achieve the same effect as fixed bed or moving bed For the same processing capacity of the process, the size of the reactor needs to be increased, which will also increase investment and cost. To solve this problem, the solution adopted by the present invention is: increase the operating pressure of the reactor so as to increase the processing capacity of the device. Since the lock hopper is arranged in the catalyst flow channel between the reactor and the regenerator, it is possible to control the operating pressure of the reactor to be higher than that of the regenerator.

Therefore, according to a preferred embodiment of the present invention, in the method for producing light olefins from light alkanes according to the present invention, the reaction pressure in the control reactor is at least 0.3MPa higher than the regeneration pressure in the regenerator .

According to the present invention, the lock hopper can safely and effectively transfer the catalyst from the high-pressure hydrocarbon or hydrogen environment of the reactor to the low-pressure oxygen environment of the regenerator, and from the low-pressure oxygen environment of the regenerator to the high-pressure hydrocarbon or hydrogen environment of the reactor. transfer. That is to say, by using the lock hopper, on the one hand, the reducing atmosphere (hydrogen atmosphere) of the reactor and the regenerated catalyst feed tank for regenerated catalyst reduction can be well isolated from the burnt regeneration oxygen-containing atmosphere of the regenerator, To ensure the safety of the process method of the present invention, on the other hand, the operating pressure of the reactor and the regenerator can be flexibly adjusted, especially the operating pressure of the reactor can be increased without increasing the operating pressure of the regenerator to increase the processing capacity of the device .

The lock hopper of the present invention is a device that can switch the same material flow between different atmospheres (such as oxidizing atmosphere and reducing atmosphere) and/or between different pressure environments (such as from high pressure to low pressure, or vice versa). The structure of the device is well known to those skilled in the art. The steps for completing the transfer of catalyst particles from a high-pressure hydrocarbon environment to a low-pressure oxygen environment through a lock hopper may include: 1. Using hot nitrogen to purge residual oxygen in the emptied lock hopper into the regenerator; Purge out from the lock hopper; 3. Pressurize the emptied lock hopper with hydrogen; 4. Fill the emptied lock hopper with spent catalyst from the spent catalyst receiver; 5. Pressurize by venting The hydrogen in the lock hopper decompresses the filled lock hopper; 6. Use hot nitrogen to purge the hydrogen out of the filled lock hopper; 7. Discharge the standby catalyst from the filled lock hopper to the standby catalyst feed tank. The steps for completing the transfer of catalyst particles from a low-pressure oxygen environment to a high-pressure hydrocarbon environment through a lock hopper may include: 1. Using hot nitrogen to blow oxygen from a lock hopper filled with regenerated catalyst into the regenerator; 2. Using hydrogen to blow nitrogen from the lock hopper 3. Use hydrogen to pressurize the filled lock hopper; 4. Discharge the regenerated catalyst from the filled lock hopper to the regenerated catalyst feed tank; 5. By discharging the hydrogen in the pressurized lock hopper, the discharged The empty lock hopper is depressurized; 6. The hydrogen is purged from the emptied lock hopper with hot nitrogen; 7. The regenerated catalyst is filled from the regenerator receiver into the emptied lock hopper.

According to a specific embodiment of the present invention, only one lock hopper can be used, that is, the spent catalyst and the regenerated catalyst can be transported using the same lock hopper, or different lock hoppers can be used to transport the spent catalyst separately as required. and the delivery of the regenerated catalyst, these changes all belong to the protection scope of the present invention.

According to a specific embodiment of the present invention, by setting the spent catalyst receiver, the regenerated catalyst receiver, the spent catalyst feed tank and the regenerated catalyst feed tank, the spent catalyst drawn from the reactor can be continuously transported to The raw catalyst receiver is then transported to the raw catalyst feed tank through the lock hopper, and then continuously sent from the raw catalyst feed tank to the regenerator, and the regenerated catalyst drawn from the regenerator can be continuously sent to the regenerated catalyst The receiver is then transported to the regenerated catalyst feed tank through the lock hopper, and then continuously transported from the regenerated catalyst feed tank to the reactor, so as to realize the continuous progress of the reaction process and the regeneration process; the regenerated catalyst feed tank can be used as It can be used as a feed tank and also as a reducer for regenerated catalyst. In the spent catalyst receiver, hydrogen can be used to strip the oil and gas contained in the spent catalyst stream into the reactor to avoid material loss; in the regenerated catalyst receiver, nitrogen or other non-oxygen gas can be used on the one hand. Catalyst remains fluidized in the receiver while on the other hand the oxygen contained in the regenerated catalyst stream is stripped into said regenerator; likewise, in the spent catalyst feed tank, air or nitrogen can be used as lift catalyst Gas to keep the catalyst in the feed tank in a fluidized state.

In the present invention, the heat required for the dehydrogenation reaction is mainly provided by the high-temperature regenerated catalyst, and if necessary, additional heating devices for the raw materials and/or catalysts entering the reactor can also be provided.

The specific implementation manners of the present invention will be further described below in conjunction with the accompanying drawings.

The flow process of the method that the low-carbon alkane that Fig. 1 provides produces low-carbon olefin is as follows:

As shown in Figure 1, the preheated raw material enters the fluidized bed reactor 1 through the raw material distributor through the pipeline 7, and is transported to the fluidized bed reactor after being contacted with the reactivated regenerated catalyst from the pipeline 28, gasified and reacted 1 top. At the top of fluidized bed reactor 1, the reaction oil gas and a small amount of catalyst particles are separated by gas-solid separation equipment, and the catalyst particles return to the bed of the fluidized bed reactor, and the separated dehydrogenation products enter the subsequent separation system through pipeline 8 for product separation . The carbon-deposited spent catalyst on the upper part of the fluidized bed reactor enters the spent catalyst receiver 3 through the pipeline 21 . After the catalyst in the raw catalyst receiver 3 is stripped of the reaction oil gas carried by the hydrogen gas from the pipeline 11, it flows into the lock hopper 4 through the pipeline 22 and the control valve 15 in sequence, and the stripped oil gas is sent into the fluidized bed reactor through the pipeline 31 1.

After undergoing a series of processes such as purging, boosting, filling and depressurizing in the lock hopper 4, the raw catalyst flows into the raw catalyst feed tank 5 through the pipeline 23 and the control valve 18, and then through the pipeline 24 and the control valve in turn. 19 is mixed with the air from the pipeline 12, and then lifted to the middle and upper part of the fluidized bed regenerator 2 through the pipeline 25. The spent catalyst is contacted and coked with oxygen-containing gas from line 9 in fluidized bed regenerator 2 to restore catalyst activity. The regenerated flue gas is discharged from the top of the regenerator 2 through the pipeline 10 and then vented through the heat exchange and catalyst dust recovery system. After the regenerated catalyst is mixed with the nitrogen from the pipeline 13 through the control valve 20, it is lifted to the regenerated catalyst receiver 6 through the pipeline 26, and the catalyst in the regenerated catalyst receiver 6 is fluidized by the nitrogen from the pipeline 14 and the oxygen carried by the catalyst is stripped. , into the lock hopper 4 through the pipeline 27 and the control valve 17 in turn.

After the regenerated catalyst goes through a series of purging, depressurization, filling and boosting processes in the lock hopper 4, it first flows into the regenerated catalyst feed tank 40 through the control valve 16 and the pipeline 28, and then flows into the fluidized bed reaction through the pipeline 42. In vessel 1, the feed from line 7 is contacted and reacted.

Fig. 2 is a kind of further embodiment of the present invention, and its flow process is on the basis of Fig. 1, after regenerated catalyst is discharged by lock hopper 4, flows into regenerated catalyst feed tank 40 first through control valve 16 and pipeline 28 successively, After being reduced by the hydrogen-containing gas from the pipeline 41, it flows into the fluidized bed reactor 1 through the pipeline 42 to contact with the raw material. The raw material and the catalyst contact and react in the fluidized bed reactor 1 arranged with a plate grid 50 .

The following embodiments will describe the specific implementation of the invention in conjunction with the accompanying drawings.

The devices used in the examples are all pressurized fluidized bed devices, which have similar implementations to those described in the accompanying drawings, so as to achieve similar reaction and regeneration effects.

The raw materials used in the examples are purchased gas sources, which are propane (purity above 99.5%), isobutane (purity above 99.5%), and a mixture of propane and isobutane (mass ratio 1:1).

The catalysts used in the examples are prepared catalysts, namely Cr-Fe-K/Al ₂ O ₃ catalyst and Pt-Sn-K/Al ₂ O ₃ catalyst.

The preparation process of Cr-Fe _- K/ _Al2O3 catalyst (hereinafter referred to as chromium series catalyst) is as follows: first, 780g chromium nitrate (analytical pure), 100g ferric nitrate (analytical pure), 80g potassium nitrate (analytical pure) solid feeding Put it into a vertical stirring tank filled with 3000g of distilled water, and stir for 1 hour; then, feed 2000g of γ-Al ₂ O ₃ dried in advance into the above vertical stirring tank, fully stir and soak for 2 hours; transfer the slurry in the stirring tank Filter out the excess water in the filter tank, and then place the catalyst in a drying oven at 200°C for drying. This process takes at least 2 hours; place the dried catalyst in a muffle furnace at 520°C for 6 hours to obtain activated The Cr-Fe-K/Al ₂ O ₃ dehydrogenation catalyst was put in a desiccator for later use.

The preparation process of Pt-Sn-K/Al ₂ O ₃ catalyst (hereinafter referred to as platinum catalyst) is as follows: first, 20g chloroplatinic acid (analytical pure), 120g tin nitrate (analytical pure), 90g potassium nitrate (analytical pure) solid Feed into a vertical stirring tank containing 2400g of distilled water, and stir for 1 hour; then, feed 2000g of γ-Al ₂ O ₃ dried in advance into the above vertical stirring tank, fully stir and soak for 2 hours; the slurry in the stirring tank Transfer to a filter tank to filter out excess water, and then place the catalyst in a 180°C drying oven for drying, which takes at least 2 hours; place the dried catalyst in a muffle furnace at 500°C for 4 hours to obtain an activated Pt-Sn-K/Al ₂ O ₃ dehydrogenation catalyst, put it in a desiccator for later use.

Example 1

Embodiment 1 is carried out according to the process shown in Figure 1, the raw material used is propane, and the prepared chromium-based catalyst and platinum-based catalyst are used respectively. The experimental conditions, raw material conversion and product selectivity data are listed in Table 1.

Example 2

Embodiment 2 is carried out according to the process shown in Figure 2, the raw material used is isobutane, and the prepared chromium-based catalyst and platinum-based catalyst are used respectively. The experimental conditions, raw material conversion and product selectivity data are listed in Table 2.

Example 3

Example 3 is carried out according to the process shown in Figure 2, the raw material used is a mixture of propane and isobutane, and the prepared chromium-based catalyst and platinum-based catalyst are used respectively. The experimental conditions, raw material conversion and product selectivity data are listed in Table 3.

As can be seen from Table 1, Table 2 and Table 3, using the fluidized bed reaction-regeneration system of the present invention, under the lower conditions of reaction temperature and regeneration temperature, the conversion rate of raw materials and the yield of target olefins can reach the existing The level of industrial dehydrogenation technology, and because the pressure of the reaction system is higher than that of existing industrial devices, so under the same conditions of other operating conditions, the raw material processing capacity of the reaction system of the present invention is higher than that of existing industrial devices.

Table 1

Table 2

table 3

Claims (15)

1. A method for producing low-carbon olefins from low-carbon alkanes, the method comprising: Continuously contact the preheated low-carbon alkanes with a dehydrogenation catalyst in a fluidized bed reactor and undergo a dehydrogenation reaction under dehydrogenation conditions to produce oil and gas rich in low-carbon olefins and a carbon-deposited catalyst; The low-carbon alkanes are C2-C5 alkanes or mixtures thereof; Separating the oil gas from the raw catalyst, sending the separated oil gas to the product separation and recovery system, and continuously leading the raw catalyst out of the reactor; After the spent catalyst drawn from the reactor is transported to the spent catalyst receiver, it is transported to the spent catalyst feed tank through a lock hopper, and then sent from the spent catalyst feed tank to the fluidized bed regenerator, and regenerated Carry out charred regeneration in an oxygen-containing atmosphere to obtain a regenerated catalyst; After the regenerated catalyst is continuously drawn from the regenerator to the regenerated catalyst receiver, it is transported to the regenerated catalyst feed tank through a lock hopper, and is continuously returned to the reactor from the regenerated catalyst feed tank; The reaction pressure is at least 0.3MPa higher than the regeneration pressure in the regenerator. 2. according to the method for claim 1, this method also comprises: the regenerated catalyst that will be transported in the regenerated catalyst feed tank is carried out reduction treatment under reducing atmosphere, obtains reduced catalyst, then this reduced catalyst is returned to described reaction continuously device. 3. The method according to claim 1, wherein the lower alkanes are one or more selected from ethane, propane, isobutane, n-butane, n-pentane and isopentane. 4. The method according to claim 1, wherein the low-carbon alkane is at least one selected from natural gas condensate, natural gas liquid, catalytic cracking liquefied gas, oil field gas condensate and shale gas condensate. 5. The method according to claim 1, wherein the fluidized bed reactor is a bubbling fluidized bed reactor or a turbulent fluidized bed reactor. 6. The method of claim 1, wherein the fluidized bed reactor has built-in baffles arranged in layers. 7. The method according to claim 6, wherein the built-in baffle is a panel grid, and a layer of panel grid is installed every 20-150 cm, from the bottom surface of the lowermost panel grid to the top of the uppermost panel grid. The distance between the surfaces is 20% to 70% of the total height of the inner space of the reactor. 8. The method according to claim 1, wherein the oil gas and spent catalyst are separated by a metal sintered filter. 9. The method according to claim 1, wherein said dehydrogenation catalyst contains an active component and a carrier; said active component is metallic platinum or chromium oxide, and said carrier is aluminum oxide; taking the total weight of the catalyst as a basis, said The content of the metal platinum is 0.01 wt% to 1.0 wt%, or the content of the chromium oxide is 1.0 wt% to 30 wt%, and the content of the carrier is a balance amount. 10. The method according to claim 1, wherein the conditions of the dehydrogenation reaction are: a reaction temperature of 500 to 700° C., a reaction pressure of 0.1 to 3 MPa, a low-carbon alkane volume space velocity of 100 to 2000 hours ⁻¹ , and a catalyst residence time of 1 to 3 MPa. 30 minutes. 11. The method according to claim 10, wherein the conditions of the dehydrogenation reaction are: reaction temperature 530-600° C., reaction pressure 0.4-2.0 MPa, light alkane volume space velocity 200-500 hours ⁻¹ , catalyst residence time 3 ~8 minutes. 12. The method according to claim 1, wherein the conditions for said burnt regeneration are: temperature is 550-750° C., pressure is 0.1-0.5 MPa, catalyst residence time is 5-60 minutes; said oxygen-containing atmosphere is Air, air diluted with nitrogen, or oxygen-enriched gas is used as the fluidizing medium. 13. The method according to claim 2, wherein the conditions of the reduction treatment are: the temperature is 500-600° C., the pressure is 0.4-2.0 MPa, and the residence time of the catalyst is 1-10 minutes; the reduction atmosphere is hydrogen-containing The reducing stream is used as the fluidizing medium; the reducing stream does not contain oxygen and contains 50-100 volume percent hydrogen, and contains 0-50 volume percent refinery dry gas. 14. The process of claim 1, wherein oil vapors contained in the spent catalyst stream in the spent catalyst receiver are stripped to the reactor with hydrogen. 15. The method according to claim 1, further comprising: returning the unreacted low-carbon alkanes separated by the product separation and recovery system to the reactor as a raw material.