CN105585407B - A kind of method by small molecule hydrocarbon mixture preparing low-carbon olefins - Google Patents

Abstract

The invention discloses a method for preparing low-carbon olefins from a small-molecular hydrocarbon mixture. The method comprises: dehydrogenating the small-molecular hydrocarbon mixture in a fluidized bed dehydrogenation reactor in the presence of a dehydrogenation catalyst , to obtain olefin-rich oil gas and dehydrogenation catalyst; the dehydrogenation catalyst is passed through the lock hopper into the fluidized bed regenerator for regeneration, and then circulated back to the dehydrogenation reactor through the lock hopper; the olefin-rich oil gas Send it to a fluidized bed cracking reactor for cracking reaction to obtain oil and gas rich in light olefins. In the present invention, the dehydrogenation and cracking reactions of the small molecule hydrocarbon mixture are separately carried out sequentially, so that the dehydrogenated small molecule hydrocarbon mixture is easier to crack, and the temperature and energy consumption of the cracking reaction can be reduced. In addition, the dehydrogenation reaction system of the present invention can flexibly adjust the operating pressure of the dehydrogenation reactor and the regenerator through the use of the lock hopper, completely avoiding the contact of the hydrogen-containing gas flow and the oxygen-containing gas flow, and is safer and more reliable.

Description

A method for preparing low-carbon olefins from small molecule hydrocarbon mixtures

technical field

The invention relates to a method for preparing low-carbon olefins from small molecular hydrocarbon mixtures.

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. At present, there are mainly the following methods for producing ethylene, propylene, butene or pentene from petroleum-based hydrocarbon raw materials that have been industrialized: steam cracking, fluidized catalytic cracking or catalytic cracking and dehydrogenation. These existing technologies have the following disadvantages:

Steam cracking: The main product of steam cracking is ethylene, which has technical limitations such as high energy consumption and production cost, low propylene/ethylene ratio, and difficult adjustment of product structure; propylene and heavier olefins are by-products of this method, and the proportion of the product is far less than Ethylene, other by-products including fuel gas, tar and coke, etc., are of very low value.

Fluid catalytic cracking or catalytic cracking: The main product of conventional catalytic cracking is high-octane gasoline, and the yield of light olefins is low. In order to increase the production of light olefins, catalytic cracking technology came into being, requiring higher operating temperature or the use of more shape-selective molecular sieve catalysts. It is worth mentioning that the processing and utilization of alkane components in liquefied gas has gradually received attention.

Catalytic dehydrogenation: The dehydrogenation reaction of hydrocarbons is a strong endothermic reaction that requires high temperature to proceed, especially low-carbon alkanes. The large amount of heat input to the reaction zone means that the reactor/regenerator is expensive to design and manufacture.

In order to improve the selectivity of low-carbon olefins and fundamentally reduce energy consumption and production costs, naphtha catalytic cracking technology has become a research hotspot. The reaction mechanism of naphtha catalytic cracking varies with different catalysts. Generally speaking, it is the result of the joint action of two reaction mechanisms of carbocations and free radicals. At present, domestic and foreign research institutes have conducted extensive research on catalytic cracking of naphtha and developed unique catalysts and processes. According to the type of reactor, naphtha catalytic cracking technology is mainly divided into two categories. One is fixed bed catalytic cracking technology. The representative technology is the new process of naphtha catalytic cracking in Japan, which uses 10% La/ZSM-5 as the catalyst. , the reaction temperature is 650°C, the total yield of ethylene and propylene can reach 61%, and the P/E mass ratio is about 0.7; the naphtha catalytic cracking process developed by Korea LG Petrochemical Company uses metal oxide catalysts, and the reaction temperature can be reduced by 50 ～100℃, the yield of ethylene increased by 20%, and the yield of propylene increased by 10%. Japan Asahi Kasei Co., Ltd. adopts C ₂ ～C ₁₂ linear alkanes, with Mg/ZSM-5 as the catalyst, the reaction temperature is 680℃, and the total yield of ethylene and propylene The ratio is 43%, and the P/E mass ratio is about 0.93. Although the yield of olefins in the fixed-bed catalytic cracking process is high, the reduction in reaction temperature is not large, and it is difficult to fundamentally overcome the limitations of the steam cracking process. The other is fluidized catalytic cracking technology, the representative technology is ACO process, which combines fluidized catalytic cracking reaction system and high acid ZSM-5 catalyst, compared with steam cracking technology, the total yield of ethylene and propylene can be increased 15% to 25%, the P/E mass ratio is about 1. CN200810032922.5 discloses a composite molecular sieve catalyst in which ZSM-5/mordenite, ZSM-5/beta zeolite and ZSM-5/Y zeolite are mixed as active components. This type of composite molecular sieve catalyst has a higher yield of low-carbon olefins and the ability to process complex cracking raw materials such as naphtha than single-component catalysts. Using ZSM-5/mordenite symbiotic molecular sieve, ZSM-5/beta zeolite symbiotic molecular sieve, ZSM-5/Y zeolite symbiotic molecular sieve to support at least one element or its oxide in P, As, or Bi, the obtained catalyst has It has the characteristics of high acid density, high acid strength, stable acidity and not easy to lose. Using naphtha from Shanghai Gaoqiao Petrochemical Company as raw material, under the conditions of reaction temperature 600-650℃, reaction pressure 0.001-0.5MPa, space velocity 0.25-4h ^-1 , water/oil mass ratio 1-4, low The carbon olefin yield can reach 55%.

Although the above-mentioned process has achieved relatively satisfactory results in the laboratory research stage and the pilot test stage, various technical difficulties exist so that the industrialization process is still relatively slow. The present invention aims to find a process and device for preparing low-carbon olefins from small molecule hydrocarbon mixtures. Those who study catalytic cracking or catalytic cracking generally know that under the action of acidic catalysts, alkenes are easily converted into carbocations, and its catalytic cracking rate is much faster than that of corresponding alkanes. Therefore, the present invention aims to seek a method for producing olefins through catalytic dehydrogenation of small molecule hydrocarbon mixtures rich in alkanes, and then rapidly catalytically cracking the olefins for maximum production of light olefins.

At present, the dehydrogenation processes of low-carbon alkanes mainly include the Catofin process of Lummus Company, the Oleflex process of UOP Company, the STAR process of Phillips Company and the FBD-4 process of Snamprogetti Company of Italy. 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 ; the Oleflex process of UOP uses 3 sets of moving bed reactors in series and the noble metal catalyst Pt/Al ₂ O ₃ , published in US3978150 A moving bed alkane dehydrogenation process was developed; the former Soviet Union used a chromoaluminic acid catalyst ebullating bed process for isobutane (and a mixture of n-butane or isobutane and n-butane) dehydrogenation. Both EP0894781A1 and US7235706B2 have announced a method for producing low-carbon olefins by dehydrogenating corresponding alkanes, using a dense-phase fluidized bed reaction-regeneration system, with a reaction temperature of 450-800°C, a reaction pressure of 0.1-3atm, and a volumetric space velocity of 100～1000h ^-1 , the two patents use different catalyst compositions, the catalyst components of the former are chromium oxide, tin oxide, and potassium oxide, while the catalyst components of the latter are gallium oxide, metal platinum, and potassium oxide; after carbon deposition The catalyst is regenerated by a dense-phase fluidized bed; the spent agent and regenerated agent are transferred between the reactor and the regenerator through a U-shaped tube.

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 working condition of the reactor changes frequently in the oxidation and reduction environment, and the temperature change of the reactor is very complicated, which affects the reaction stability to a certain extent. 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.

There are numerous catalyst formulations for the dehydrogenation of low-carbon alkanes or the oxidation of low-carbon alkanes to produce low-carbon olefins, such as noble metal catalyst systems, transition metal oxides and composite metal oxide systems, heteropolyacid catalyst systems and molecular sieve catalyst systems, etc. . A number of patents describe catalysts using chromium oxide as active components or cocatalysts, such as US 2956030 and US 2945823; US 4056576 and other patents have announced the use of catalysts containing gallium oxide for alkane dehydrogenation; US 4914075 has published A process for the dehydrogenation of alkanes using catalysts containing the noble metals platinum and gallium oxide, and describes the need for chlorination of the regenerated catalyst after charring to redistribute the active metal components. GB 2162082A discloses a catalytic dehydrogenation reaction of C ₃ -C ₅ alkanes using a chromium oxide/alumina catalyst. The synthesis method of the catalyst adopts an equal-volume impregnation method, which is different from impregnation of an alumina carrier in excess chromium solution.

CN 102465001A discloses a method for catalytically converting naphtha into low-carbon olefins, which mainly involves contacting naphtha and a ZSM-5 molecular sieve catalyst loaded with dehydrogenation functional metals in a fluidized bed reactor, aiming to solve the current There is a problem that the yield of low-carbon olefins is not high in the technology. The dehydrogenation functional metal described in the patent is preferably at least one of Mo, Ni, Cu, Pt and Pd, and the mass of ZSM-5 molecular sieve accounts for 20-60% of the total mass of the catalyst. According to the patent, the highest yield of low-carbon olefins can reach 47.55%. It can be seen from the description of this patent that the content of molecular sieve used in the catalyst is relatively high and the yield of low-carbon olefins has not reached a very ideal yield, which shows that the operating cost is relatively high.

CN 101462916A discloses a method for producing low-carbon olefins by catalytic cracking of petroleum hydrocarbons. The method includes contacting and reacting petroleum hydrocarbons with catalytic dehydrogenation catalysts at 450-550°C and 0.1-0.3 MPa to produce olefins containing 5% by weight to 30 The dehydrogenation product of olefin, and then the dehydrogenation product is contacted with catalytic cracking catalyst to undergo catalytic cracking to prepare light olefin. The advantage of the method described in this patent is that the required reaction temperature is greatly reduced, which indirectly saves energy consumption. However, the reactors used in the examples and comparative examples published in this patent are two fixed-bed reactors filled with dehydrogenation and cracking catalysts respectively, and the catalyst regeneration and recycling conditions are not explained; and because the catalyst reaction of the fixed-bed reactor And regeneration is carried out intermittently in multiple fixed bed beds, the reaction cannot be carried out continuously, and the dehydrogenation and cracking or cracking reactions are all endothermic reactions, and the heat transfer performance of the fixed bed reactor is poor, requiring a heating furnace or Other heating devices provide heat, which increases the cost of the process; in addition, the patent does not describe the specific process devices and structural forms that the inventive method is applicable to.

Contents of the invention

The purpose of the present invention is to provide a method for producing low-carbon olefins from a mixture of small molecule hydrocarbons, which carries out dehydrogenation and cracking reactions separately in sequence with the mixture of small molecule hydrocarbons, wherein the fluidized bed dehydrogenation of the present invention The reaction-regeneration system can overcome the problems existing in the process of producing light olefins by using the fluidized bed reaction-regeneration system. On the one hand, it can ensure the safety of the process, and on the other hand, it can be used in the same dehydrogenation reactor size. Increase the throughput of the device.

In order to achieve the above object, the present invention provides a method for producing low-carbon olefins from small molecule hydrocarbon mixtures, the method comprising: continuously combining the preheated small molecule hydrocarbon mixture in a fluidized bed dehydrogenation reactor with The dehydrogenation catalyst contacts and undergoes a dehydrogenation reaction to produce oil and gas rich in olefins and a carbon-deposited ungenerated dehydrogenation catalyst; separate the oil and gas rich in olefins from the ungenerated dehydrogenation catalyst, and send the separated oil and gas rich in olefins to into the cracking reactor to contact with the cracking catalyst, and the cracking reaction occurs under the cracking reaction conditions, and the obtained oil and gas rich in light olefins are sent to the product separation and recovery system; It is continuously drawn to the receiver of the raw dehydrogenation catalyst and then transported to the feed tank of the raw dehydrogenation catalyst through a lock hopper; the raw dehydrogenation catalyst in the feed tank of the raw dehydrogenation catalyst is transported or transported to the fluidized Bed regenerator, and regenerate coke in the regenerator under an oxygen-containing atmosphere to obtain a regenerated dehydrogenation catalyst; after the regenerated dehydrogenation catalyst is continuously drawn from the regenerator to the receiver of the regenerated dehydrogenation catalyst, it is then transported through a lock hopper to the regenerated dehydrogenation catalyst feed tank, and continuously from the regenerated dehydrogenation catalyst feed tank to the dehydrogenation reactor.

Preferably, the method also includes: reducing the regenerated dehydrogenation catalyst delivered to the regenerated dehydrogenation catalyst feed tank under a reducing atmosphere to obtain a reduced catalyst, and then continuously returning the reduced catalyst to the dehydrogenation reaction device.

Preferably, the small molecule hydrocarbon mixture is a mixture of C3-C12 hydrocarbons.

Preferably, the small molecule hydrocarbon mixture is one or more of straight run naphtha, oilfield condensate, shale oil light components, hydrogenated naphtha, coker gasoline and cracked gasoline.

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

Preferably, the fluidized bed dehydrogenation 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 dehydrogenation 20% to 70% of the total height of the inner space of the reactor.

Preferably, wherein the oil gas and the raw dehydrogenation 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 alumina or aluminum silicate; based on the total weight of the catalyst, the metal The content of 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 as follows: the reaction temperature is 500-700°C, the reaction pressure is 0.1-3.0 MPa, the volume space velocity of the small molecule hydrocarbon mixture is 100-2000 hours ^-1 , and the catalyst residence time is 1-2. 30 minutes.

Preferably, the conditions of the dehydrogenation reaction are: the reaction temperature is 530-600°C, the reaction pressure is 0.4-2.0MPa, the volume space velocity of the small molecule hydrocarbon mixture is 200-500 hours ^-1 , and the residence time of the catalyst is 3 ~8 minutes.

Preferably, the cracking reaction is carried out in a riser reactor, and the cracking reaction conditions are as follows: reaction temperature is 500-620°C, reaction pressure is 0.1-1 MPa, and volume space velocity is 150-1500h ^-1 .

Preferably, wherein the cracking catalyst contains a molecular sieve and a carrier; the molecular sieve is at least one of ZSM type, Y type molecular sieve and β-type zeolite, and the carrier is aluminum silicate; the molecular sieve content is 5% of the catalyst weight % by weight to 50% by weight, the content of the carrier is 50% to 95% by weight of the weight of the catalyst.

Preferably, the conditions for charred regeneration are: temperature 550-750°C, pressure 0.1-0.5 MPa, catalyst residence time 5-60 minutes; the oxygen-containing atmosphere is air diluted with air and nitrogen , or oxygen-enriched gas 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 substantially free of oxygen and contains 50-100 volume percent hydrogen, and contains 0-50 volume percent refinery dry gas.

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

Preferably, wherein the olefin-rich oil gas contained in the raw dehydrogenation catalyst stream in the raw dehydrogenation catalyst receiver is stripped with hydrogen to the dehydrogenation reactor.

The present invention provides a method for preparing low-carbon olefins from a mixture of small molecular hydrocarbons. Compared with the existing method for preparing low-carbon olefins from petroleum-based hydrocarbons, the main advantages are as follows:

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

2. The use of fluidized reaction-regenerated dehydrogenation reaction system eliminates the use of multiple dehydrogenation 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 to the reactants by the hot regenerated dehydrogenation catalyst, 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 dehydrogenation reactor and the regenerated dehydrogenation catalyst feed tank used for the reduction of the regenerated dehydrogenation catalyst can be combined with the charred regeneration of the regenerator. The oxygen atmosphere is well isolated to ensure the safe operation of the process;

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

6. The dehydrogenation and cracking reactions of small molecule hydrocarbon mixtures are carried out using different reaction devices. The dehydrogenated small molecule hydrocarbon mixtures are easier to crack, which can reduce the temperature of the cracking reaction and reduce energy consumption.

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 a dehydrogenation and cracking system according to a specific embodiment of the present invention;

Fig. 2 is a schematic flow sheet of a dehydrogenation reaction system according to a further embodiment of the present invention;

Fig. 3 is a top view and a front view of an embodiment of the built-in baffle (i.e., the plate grid) in Fig. 2;

Fig. 4 is a schematic flow sheet of the method for preparing low-carbon olefins from a small molecule hydrocarbon mixture according to a specific embodiment of the present invention, including a cracking reaction system and a dehydrogenation reaction system, wherein the dehydrogenation reaction system can refer to Fig. 1 or Figure 2 for setup.

Explanation of reference signs

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

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

7 Line 8 Line 9 Line 10 Line 11 Line 12 Line

13 Line 14 Line 15 Control Valve 16 Control Valve 17 Control Valve

18 Control valve 19 Control valve 20 Control valve 21 Line 22 Line

23 Line 24 Line 25 Line 26 Line 27 Line

28 Line 29 Line 30 Line 31 Line

40 Regenerated dehydrogenation catalyst feed tank 41 Pipeline 42 Pipeline 50 Plate grid

101 Fluidized bed regenerator 102 Settler 103 Catalytic cracking reactor

104 Line 105 Regular Feed Nozzle 106 Line

107 Waiting ramp 108 Regenerating ramp 109 Upper nozzle 110 Pipeline

111 Double action slide valve 112 Pipeline 113 Three-way valve 114 Dehydrogenation reaction system

115 cracking reaction system

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, and are not intended to limit the present invention.

The invention provides a method for preparing low-carbon olefins from a small molecule hydrocarbon mixture, the method comprising: continuously contacting the preheated small molecule hydrocarbon mixture with a dehydrogenation catalyst in a fluidized bed dehydrogenation reactor and A dehydrogenation reaction occurs to produce oil and gas rich in olefins and a carbon-deposited dehydrogenation catalyst; separate the oil and gas rich in olefins from the dehydrogenation catalyst, and send the separated oil and gas rich in olefins to the cracking reactor and The cracking catalyst is contacted, and the cracking reaction occurs under the cracking reaction conditions, and the obtained oil gas rich in light olefins is sent to the product separation and recovery system; the separated dehydrogenation catalyst is continuously drawn from the dehydrogenation reactor to the waiting After the raw dehydrogenation catalyst receiver is transported to the raw dehydrogenation catalyst feed tank through the lock hopper; the raw dehydrogenation catalyst in the raw dehydrogenation catalyst feed tank is transported or gas-lifted to the fluidized bed regenerator, and Carry out coke regeneration in the regenerator under an oxygen-containing atmosphere to obtain a regenerated dehydrogenation catalyst; after the regenerated dehydrogenation catalyst is continuously drawn from the regenerator to the receiver of the regenerated dehydrogenation catalyst, it is then transported to the regenerated dehydrogenation catalyst through a lock hopper feed tank, and from the regenerated dehydrogenation catalyst feed tank is continuously returned to the dehydrogenation 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 dehydrogenation catalyst is burnt and regenerated by the regenerator, hydrogen will be generated due to the dehydrogenation reaction of the small molecule hydrocarbon mixture, and the burning Even if the coked regenerant has not undergone reduction treatment, it can still undergo dehydrogenation reaction while being reduced after returning to the dehydrogenation reactor. However, in order to better improve the activity of the catalyst, it is preferred that the method of the present invention also includes: transporting the regenerated dehydrogenation catalyst drawn from the regenerator to the regenerated dehydrogenation catalyst feed tank through a lock hopper for reduction under a reducing atmosphere treatment to obtain a reduced catalyst which is then continuously returned to the dehydrogenation reactor.

According to the present invention, the small molecule hydrocarbon mixture may be a mixture of C3-C12 hydrocarbons, for example, it may be selected from straight-run naphtha, oilfield condensate, shale oil light components, hydrogenated naphtha One or more of , coker gasoline and cracked gasoline, or industrial or natural small molecule hydrocarbon mixtures from other sources.

According to the present invention, the fluidized bed dehydrogenation 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 can be a boiling fluidized bed reactor And other fluidized bed reactors commonly used in industry. The fluidized bed dehydrogenation 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, the inside of the fluidized bed dehydrogenation reactor can be provided with built-in baffles arranged in layers to prevent the uneven mixing of oil gas and/or catalyst, so that oil gas and/or catalyst React in a plug-flow state through the dehydrogenation reactor to increase the conversion rate of the small molecule hydrocarbon mixture and the selectivity of the required low-carbon olefins; the built-in baffle can be a plate grid, a plate grid The grid can be installed with one layer every 20-150cm, preferably 50-100cm, and the distance from the bottom surface of the lowermost panel-type grid to the top surface of the uppermost panel-type grid can be the inner space of the dehydrogenation reactor. 5% to 80% of the total height, preferably 20% to 70%, more preferably 30% to 50%; the material of the plate grid can be selected from the gas distributor of the catalytic cracking regenerator or the large hole distribution plate. Using materials, the shape of the grille can be wave-like trapezoidal or triangular shapes, and there are evenly arranged small or large holes on the grille for the catalyst and gas to pass through regularly.

In order to separate the oil gas rich in olefins and the dehydrogenation catalyst to be produced after the reaction in the fluidized bed dehydrogenation reactor, a traditional cyclone separator can be used, which is well known to those skilled in the art, and the present invention Not described in detail.

According to a preferred embodiment of the present invention, the oil gas and the unborn dehydrogenation catalyst can also be separated by using a metal sintered filter; the metal sintered filter is a known porous material that can effectively Separation of solid particles or powders from gaseous components accurately and robustly. 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 dehydrogenation 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 olefin-rich oil and gas produced by the dehydrogenation reaction can be cooled to the required working temperature of the feed compression pump, and then enter the catalytic cracking reactor through the feed nozzle, or refer to other conventional catalytic cracking feeding methods Enter the cracking reactor; wherein, the operating parameters of the dehydrogenation reactor can be adjusted to control the olefin content in the olefin-rich oil gas to be greater than 30% by weight, preferably between 30% by weight and 50% by weight.

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 dehydrogenation 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 or aluminum silicate; the alumina is preferably γ-Al ₂ O ₃ and θ-Al ₂ O ₃ 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 group When divided into 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 alkali metal oxides or alkaline earth metal oxides; 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 of the dehydrogenation reaction may be: reaction temperature 500-700°C, reaction pressure 0.1-3.0MPa, light alkane volume space velocity 100-2000 hours ^-1 , catalyst residence time 1-30 minutes; preferred dehydrogenation The conditions for the hydrogen reaction 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 cracking reaction is well known to those skilled in the art, and is generally carried out in a riser reactor, which will not be described in the present invention. The conditions of the cleavage reaction are also well known to those skilled in the art, and the present invention is not particularly limited, for example, the reaction temperature can be 500～620°C, preferably 520～600°C; the reaction pressure can be 0.1～1MPa, preferably 0.2-0.5 MPa; volumetric space velocity may be 150-1500h ^-1 , preferably 300-1000h ^-1 .

According to the present invention, the cracking catalyst is well known to those skilled in the art, for example, the molecular sieve can be at least one of ZSM type, Y type molecular sieve and beta type zeolite, preferably ZRP zeolite, and the carrier can be is an inorganic oxide, preferably aluminum silicate. The content of the molecular sieve can be 5% to 50% by weight of the catalyst, preferably 20% to 30% by weight of the catalyst, and the content of the carrier is 50% to 95% by weight of the catalyst, preferably the catalyst 70% to 80% by weight. In the present invention, the cracking catalyst may also be a cracking catalyst commonly used in industry, which is not limited in the present invention.

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: regeneration temperature is 550-750°C, preferably 640-700°C; regeneration pressure is 0.1-0.5MPa, preferably 0.2-0.5MPa; catalyst residence time is 5-60min, It is preferably 10-20 minutes; the oxygen-containing atmosphere can be air, air diluted with nitrogen, or oxygen-enriched gas as the fluidizing medium, and 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 dehydrogenation catalyst drawn from the regenerator to the regenerated dehydrogenation catalyst feed tank through a lock hopper, and performing a reduction treatment under a reducing atmosphere to obtain a reduced catalyst, so that the oxidized high-valence metal oxide in the catalyst is reduced to a low-valence active dehydrogenation component, and then the reduced catalyst is continuously returned to the dehydrogenation 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 using a catalyst with platinum as the active component, the catalyst after a long time of reaction may need a chlorination renewal process after being regenerated and burnt to redistribute the platinum active center. At this time, the regenerated dehydrogenation catalyst can be The feed tank is used as a chlorination processor.

In the fluidized bed process for producing light olefins from small molecule hydrocarbon mixtures, when only one dehydrogenation reactor is used, and the dehydrogenation reactor is operated at normal pressure or low pressure like the regenerator, if the For the same processing capacity as fixed bed or moving bed process, it is necessary to increase the size of the dehydrogenation reactor, which also increases investment and cost. To solve this problem, the solution adopted in the present invention is: increase the operating pressure of the dehydrogenation reactor so as to increase the processing capacity of the device. Since the present invention is provided with a lock hopper in the catalyst flow channel between the dehydrogenation reactor and the regenerator, it becomes possible to control the operating pressure of the dehydrogenation 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 dehydrogenation reactor is controlled to be at least higher than the regeneration pressure in the regenerator 0.3MPa.

According to the present invention, the lock hopper can make the catalyst flow from the high-pressure hydrocarbon or hydrogen environment of the dehydrogenation 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 dehydrogenation reactor. Safe and efficient transfer. That is to say, by using the lock hopper, on the one hand, the reducing atmosphere (hydrogen atmosphere) of the dehydrogenation reactor and the regenerated dehydrogenation catalyst feed tank used for the reduction of the regenerated dehydrogenation catalyst can be combined with the oxygen-containing regenerated charred regeneration of the regenerator. The atmosphere is well isolated to ensure the safety of the process of the present invention. On the other hand, the operating pressure of the dehydrogenation reactor and the regenerator can be flexibly adjusted, especially the dehydrogenation reaction can be improved without increasing the operating pressure of the regenerator. The operating pressure of the device can 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 dehydrogenation catalyst from the spent catalyst receiver into the emptied lock hopper; Pressurize the hydrogen in the lock hopper to depressurize the filled lock hopper; 6. Use hot nitrogen to purge the hydrogen out of the filled lock hopper; 7. Discharge the dehydrogenation catalyst from the filled lock hopper to the ungenerated catalyst feed tank. The step of 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 a regenerated dehydrogenation catalyst into the regenerator; Purge out from the lock hopper; 3. Use hydrogen to pressurize the filled lock hopper; 4. Discharge the regenerated dehydrogenation catalyst from the filled lock hopper to the regenerated dehydrogenation catalyst feed tank; 5. Discharge the pressurized lock hopper by discharging 6. Purge the hydrogen from the emptied lock hopper with hot nitrogen; 7. Fill the regenerated dehydrogenation catalyst from the regenerator receiver into the emptied lock hopper hopper.

According to a specific embodiment of the present invention, only one lock hopper can be used, that is, the standby dehydrogenation catalyst and the regenerated dehydrogenation catalyst are transported using the same lock hopper, or different lock hoppers can be used to carry out the dehydrogenation separately according to the needs. The transportation of the standby dehydrogenation catalyst and the regenerated dehydrogenation catalyst all belong to the protection scope of the present invention.

According to a specific embodiment of the present invention, by arranging the receiver of the dehydrogenation catalyst to be produced, the receiver of the regenerated dehydrogenation catalyst, the feed tank of the dehydrogenation catalyst to be produced and the feed tank of the regenerated dehydrogenation catalyst, the dehydrogenation reaction The standby dehydrogenation catalyst drawn from the device is continuously transported to the receiver of the standby dehydrogenation catalyst, and then transported to the feed tank of the standby dehydrogenation catalyst through the lock hopper, and then continuously transported from the feed tank of the standby dehydrogenation catalyst to the regeneration tank. device, and the regenerated dehydrogenation catalyst drawn from the regenerator can be continuously conveyed to the regenerated dehydrogenation catalyst receiver and then conveyed to the regenerated dehydrogenation catalyst feed tank through a lock hopper, and then continuously from the regenerated dehydrogenation catalyst feed tank It is transported to the dehydrogenation reactor to realize the continuous process of the reaction process and the regeneration process; the feed tank of the regenerated dehydrogenation catalyst can be used as a feed tank or as a reducer for the regenerated dehydrogenation catalyst. In the raw dehydrogenation catalyst receiver, hydrogen can be used to strip the olefin-rich oil gas contained in the raw dehydrogenation catalyst stream into the dehydrogenation reactor to avoid the loss of material; in the regenerated dehydrogenation catalyst receiver , nitrogen or other non-oxygen gas can be used to keep the catalyst in the receiver fluidized on the one hand, and to strip the oxygen contained in the regenerated dehydrogenation catalyst stream into the regenerator on the other hand; In the feed tank, air or nitrogen can be used as the lifting gas for lifting the catalyst 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 dehydrogenation catalyst. If necessary, additional heating devices for the raw materials and/or catalysts entering the dehydrogenation reactor can also be provided.

According to a specific embodiment of the present invention, the device of the method for preparing low-carbon olefins from a mixture of small molecule hydrocarbons can be divided into a dehydrogenation reaction system and a cracking reaction system. The specific embodiment of the method for taking low-carbon olefins will be further described.

Fig. 1 is the embodiment of a kind of dehydrogenation and cracking system of the present invention, and its flow process is as follows:

As shown in Figure 1, the preheated raw material enters the fluidized bed dehydrogenation reactor 1 through the raw material distributor through the pipeline 7, and is transported to the fluidized bed dehydrogenation reactor 1 after being contacted with the reactivated dehydrogenation catalyst from the pipeline 28, gasified and reacted. 1 top of bed dehydrogenation reactor. At the top of the fluidized bed dehydrogenation 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 layer of the fluidized bed dehydrogenation reactor, and the separated dehydrogenation products enter the subsequent Cracking system 115. The carbon-deposited standby dehydrogenation catalyst in the upper part of the fluidized bed dehydrogenation reactor enters the standby dehydrogenation catalyst receiver 3 through the pipeline 21 . The catalyst in the receiver 3 of the raw dehydrogenation catalyst is stripped of the reaction oil gas carried by the hydrogen gas from the pipeline 11, and then flows into the lock hopper 4 through the pipeline 22 and the control valve 15, and the stripped oil gas is sent to the fluidized bed through the pipeline 31 Dehydrogenation Reactor 1.

After undergoing a series of purging, boosting, filling and depressurizing processes in the lock hopper 4, the raw dehydrogenation catalyst flows into the raw dehydrogenation catalyst feed tank 5 through the pipeline 23 and the control valve 18, and then through the pipeline 24 and the control valve 19 are 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 dehydrogenation catalyst is contacted with oxygen-containing gas from line 9 in the fluidized bed regenerator 2 and undergoes a charring reaction 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 dehydrogenation catalyst is mixed with the nitrogen from the pipeline 13 through the control valve 20, it is lifted to the regenerated dehydrogenation catalyst receiver 6 through the pipeline 26, and the catalyst in the regenerated dehydrogenation catalyst receiver 6 is fluidized and vaporized by the nitrogen from the pipeline 14 After the oxygen carried by the catalyst is extracted, it flows into the lock hopper 4 through the pipeline 27 and the control valve 17 in sequence.

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

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

Fig. 4 is a schematic flow diagram of a cracking reaction system and a dehydrogenation reaction system of a method for preparing light olefins from a small molecule hydrocarbon mixture according to the present invention. As shown in Figure 4, wherein the dehydrogenation reaction system 114 can be the dehydrogenation reaction system of Fig. 1 or Fig. 2 in the present invention, the olefin-rich oil and gas obtained from the dehydrogenation reaction system 114 is quenched and compressed from the pipeline 8 The feed nozzle of the catalytic cracking reactor 103 that is sent into cracking reaction system 115 after, after feeding three-way valve 113, passes into cracking reactor by conventional feed nozzle 105 or the upper nozzle 109 of independent design, as the catalytic cracking raw material. The raw material is contacted with the cracking catalyst from the regenerator to undergo a cracking reaction to produce reaction oil gas rich in low-carbon olefins and a carbon-deposited catalyst. After the reaction oil gas and carbon deposition catalyst are separated by the cyclone separation system in the settler 102, the oil gas enters the subsequent cooling, compression and separation system through the pipeline 106 for processing, and the carbon deposition catalyst enters through the pipeline 104. The inclined pipe 107 enters the fluidized bed regenerator for coke regeneration, and the charred air enters the regenerator through the pipe 110 at the bottom of the regenerator, and the generated flue gas is discharged through the pipe 112, and the regenerated catalyst returns to the catalytic cracking reaction through the overflow hopper and the regeneration inclined pipe 108 device. Among them, the single-action slide valves on the standby pipeline and the regeneration pipeline can be used to adjust the circulation rate of the standby catalyst and the regenerated catalyst, and the double-action slide valve 111 on the top of the regenerator can adjust the operating pressure of the regenerator within a certain range.

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

The dehydrogenation reaction system used in the embodiment adopts a pressurized fluidized bed device, which has a similar implementation with the device described in accompanying drawing 1 or 2, to achieve similar reactions and regeneration effects; the cracking reactor is an existing industrial The specific structure of a medium-sized fluidized bed cracking reactor is shown in Figure 4.

The raw materials used in Examples 1, 2, and 3 are hydrogenated naphtha, cracked gasoline, and straight-run naphtha, respectively, and their properties are shown in Table 1.

The dehydrogenation catalyst used in the experiment is Cr-Fe-K/Al ₂ O ₃ catalyst (hereinafter referred to as chromium-based catalyst), the preparation process is as follows: first, 780g chromium nitrate (analytical pure), 100g iron nitrate (analytical pure), 80g nitric acid Potassium (analytical pure) solid is fed into a vertical stirring tank filled with 3000g distilled water, stirred for 1h; then, 2000g gamma _{- Al2O3} which has been dried in advance is fed into the above-mentioned vertical stirring tank, fully stirred and impregnated for 2h; Transfer the slurry in the stirring tank to a filter tank to filter out excess water, 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 Medium roasting for 6 hours to obtain an activated Cr-Fe-K/Al ₂ O ₃ dehydrogenation catalyst, and put it in a desiccator for later use.

The catalytic cracking catalyst used in the experiment is CIP-2 (produced by Sinopec Catalyst Qilu Branch), the molecular sieve active component is ZRP molecular sieve, the content is 25% by weight, and the rest is aluminum silicate.

Example 1

The dehydrogenation reaction of Example 1 is carried out according to the process shown in Figure 1, and the raw material used is hydrogenated naphtha, and the experimental conditions, raw material conversion rate and product selectivity data are listed in Table 2.

Example 2

The dehydrogenation reaction of Example 2 is carried out according to the process shown in Figure 2, and the raw material used is cracked gasoline, and the experimental conditions, raw material conversion rate and product selectivity data are listed in Table 2.

Example 3

The dehydrogenation reaction of embodiment 3 was carried out according to the process shown in Figure 2, and the raw material used was straight-run naphtha, and the experimental conditions, raw material conversion rate and product selectivity data are listed in Table 2.

As can be seen from Table 2, the process of producing light olefins by using the small molecule hydrocarbon mixture of the present invention, under the condition that the dehydrogenation reaction temperature and the regeneration temperature are all low, the cracked gas and the (C ₂ ⁼ +C ₃ ⁼ ) The yield can reach the existing industrial level, and because the pressure of the dehydrogenation reaction system is higher than that of the existing industrial equipment, so if the cracking reaction capacity is sufficient, the raw material handling capacity of the process of the present invention is higher than that of the existing industrial equipment .

Table 1

Table 2

Claims (16)

1. a kind of method by small molecule hydrocarbon mixture preparing low-carbon olefins, this method includes：

Continuously the small molecule hydrocarbon mixture after preheating is contacted concurrently in fluid bed dehydrogenation reactor with dehydrogenation Raw dehydrogenation reaction, produce the dehydrogenation to be generated of oil gas and carbon distribution rich in alkene；

Make the oil gas rich in alkene and dehydrogenation to be generated separation, the oil gas rich in alkene after separation is sent into cracking reaction Device contacts with catalyst for cracking, and cracking reaction occurs under crack reacting condition, the oil gas rich in low-carbon alkene that will be obtained It is sent into product separation and recovery system；

Lead to after the dehydrogenation to be generated after separation is continuously drawn out into dehydrogenation receiver to be generated from dehydrogenation reactor Cross locking hopper and be delivered to dehydrogenation head tank to be generated；

Dehydrogenation to be generated conveying in dehydrogenation head tank to be generated or air lift are delivered to fluid bed regenerator, and Coke burning regeneration is carried out in regenerator under an oxygen-containing atmosphere, obtains regenerating dehydrogenation；

After regeneration dehydrogenation is continuously drawn out into regeneration dehydrogenation receiver from regenerator, then pass through locking hopper Regeneration dehydrogenation head tank is delivered to, and the dehydrogenation reactor is continuously returned to from regeneration dehydrogenation head tank In；Control the reaction pressure in dehydrogenation reactor at least higher 0.3MPa than the regeneration pressure in regenerator.

2. method according to claim 1, this method also include：The regeneration being delivered in regeneration dehydrogenation head tank is taken off Hydrogen catalyst carries out reduction treatment under reducing atmosphere, obtains reducing catalyst, then continuously returns to the reducing catalyst Into the dehydrogenation reactor.

3. method according to claim 1, wherein the small molecule hydrocarbon class mixture is the mixture of C3~C12 hydro carbons.

4. method according to claim 3, wherein the small molecule hydrocarbon class mixture is straight-run naphtha, oil field condensed liquid, page One or more in shale oil light component, hydrotreated naphtha, coker gasoline and cracking gasoline.

5. method according to claim 1, wherein the fluid bed dehydrogenation reactor is bubbling fluidized bed reactor or turbulent flow Fluidized bed reactor.

6. method according to claim 1, wherein the fluid bed dehydrogenation reactor has the internal baffle of layered arrangement.

7. according to the method for claim 6, wherein the internal baffle is board-like grid, the board-like every 20~150cm of grid One layer of installing, from the bottom surface of bottom board-like grid to the distance between top surface of board-like grid topmost in dehydrogenation reactor The 20%~70% of portion space total height.

8. method according to claim 1, wherein separating oil gas and dehydrogenation to be generated by metal sintered filter.

9. method according to claim 1, wherein the dehydrogenation contains active component and carrier；The active component is Metal platinum or chromium oxide, the carrier are aluminum oxide or alumina silicate；On the basis of the gross weight of catalyst, the metal platinum Content is the 0.01 heavy % in weight %~1.0, or the content of the chromium oxide is the 1.0 heavy % in weight %~30, the content of the carrier For aequum.

10. method according to claim 1, wherein the condition of the dehydrogenation reaction is：Reaction temperature is 500~700 DEG C, reaction Pressure is 0.1~3.0MPa, and small molecule hydro carbons volume of mixture air speed is 100~2000 hours^-1, catalyst residence times 1~ 30 minutes.

11. method according to claim 10, wherein the condition of the dehydrogenation reaction is：Reaction temperature is 530~600 DEG C, instead It is 0.4~2.0MPa to answer pressure, and small molecule hydro carbons volume of mixture air speed is 200~500 hours^-1, catalyst residence times 3 ~8 minutes.

12. method according to claim 1, wherein described cracking reaction is carried out in riser reactor, cracking reaction Condition is：Reaction temperature is 500~620 DEG C, and reaction pressure is 0.1~1MPa, and volume space velocity is 150~1500h^-1。

13. method according to claim 1, wherein the catalyst for cracking contains molecular sieve and carrier；The molecular sieve is ZSM At least one of type, Y type molecular sieve and zeolite beta, the carrier are alumina silicate；The molecular sieve content is catalyst weight The 5 heavy % in weight %~50, the vector contg be catalyst weight the 50 heavy % in weight %~95.

14. method according to claim 1, wherein the condition of the coke burning regeneration is：550~750 DEG C of temperature, pressure 0.1 ~0.5MPa, catalyst residence times are 5~60 minutes；Described oxygen-containing atmosphere be with air, with nitrogen dilution air or Person's oxygen rich gas is as fluidizing agent.

15. method according to claim 2, wherein the condition of the reduction treatment is：Temperature is 500~600 DEG C, and pressure is 0.4~2.0MPa, catalyst residence times are 1~10 minute；Described reducing atmosphere is to be used as stream using hydrogeneous reduction logistics Change medium；The reduction logistics is substantially free of oxygen and containing 50~100 volume % hydrogen, and contains 0~50 volume % Refinery dry gas.

16. method according to claim 1, wherein by the dehydrogenation logistics institute to be generated in dehydrogenation receiver to be generated The oil gas hydrogen stripped rich in alkene contained is to the dehydrogenation reactor.