CN114181027A

CN114181027A - A kind of method for preparing light olefins from methanol

Info

Publication number: CN114181027A
Application number: CN202111486758.7A
Authority: CN
Inventors: 龚小燕; 张瑞驰; 俞祥麟; 张丰豪; 张芳; 丁艳明; 赵春艳; 孙艳茹; 张�浩
Original assignee: BEIJING HUIERSANJI GREEN CHEM-TECH CO LTD
Current assignee: BEIJING HUIERSANJI GREEN CHEM-TECH CO LTD
Priority date: 2021-12-03
Filing date: 2021-12-03
Publication date: 2022-03-15

Abstract

The invention relates to a method for preparing low-carbon olefin from methanol. In the method, the reaction of preparing low-carbon olefin from methanol and the reaction of preparing ethylene and propylene by cracking four carbon five carbon atoms after ether are carried out in the same reactor. The reactor is a fast fluidized bed reactor with a riser. The method comprises the following steps: the method comprises the following steps of (1) vaporizing and preheating raw material methanol, then feeding the raw material methanol into a fast fluidized bed reactor, reacting to generate product gas containing low-carbon olefin under the action of a modified ZSM-5 molecular sieve catalyst, and simultaneously obtaining a spent catalyst; separating the product gas to obtain ethylene, propylene, C4, C five and aromatic oil, reacting the C four with a de-etherification device to generate MTBE, returning the C five and the C four after etherification to the reactor through a riser, and cracking to generate ethylene and propylene; the spent catalyst is divided into two streams, one stream enters a regenerator to be coked and regenerated to obtain a regenerated catalyst, and the other stream is used as a circulating spent catalyst and is mixed with the regenerated catalyst from the regenerator and then returns to the reactor through a riser.

Description

Method for preparing low-carbon olefin from methanol

Technical Field

The invention relates to a method for preparing low-carbon olefin by taking methanol as a raw material. In particular to a fast fluidized bed reactor and a matched regenerator, which are adopted to carry out the reaction of preparing olefin from methanol and the cracking reaction of C, C and V after ether in the same reactor and share a reaction regeneration system and a set of reaction product separation system.

Background

Ethylene and propylene are important basic chemical products, mainly prepared by cracking naphtha. With the development of economic society, the demand for ethylene and propylene continues to rapidly increase worldwide, while at the same time non-renewable petroleum resources are becoming scarce. The technology of synthesizing the low-carbon olefin from the coal, the natural gas and the like serving as raw materials through the methanol is different from the military project, the method for preparing the low-carbon olefin through a non-petroleum route is provided, the advantages of Chinese coal resources are exerted, the defects of petrochemical raw materials are made up, and the method conforms to the basic national situation of rich coal and less oil in China.

In recent years, the technology of preparing light olefins from methanol is receiving more and more attention. According to different product distributions, technologies for preparing low-carbon olefins from methanol are mainly divided into an MTO technology and an MTP technology, the MTO technology generally adopts a fluidized bed reactor and an SAPO-34 molecular sieve catalyst to generate the low-carbon olefins mainly containing ethylene and propylene by a one-step method, the MTP technology generally adopts a fixed bed reactor and a ZSM-5 molecular sieve catalyst to prepare by a two-step method, firstly, methanol is converted into a material flow containing dimethyl ether in a DME reactor, and then the material flow of the dimethyl ether enters the MTP reactor to generate the low-carbon olefins mainly containing propylene.

MTP technology needs to recycle a large amount of circulating hydrocarbon, process steam is used for controlling reaction temperature, energy consumption is high, propylene yield is low, and MTO technology is more mature than MTP technology. At present, most of MTO technical researches are to develop a novel catalyst, reduce the coking rate of the catalyst, improve the yield of ethylene and propylene and the like.

CN102060644A discloses a method for preparing olefin by methanol two-step method, wherein the catalytic reaction system comprises a catalytic distillation reactor and a moving bed reactor, and the catalyst adopts ZSM-5 molecular sieve catalyst. In order to improve the olefin yield, the C4-containing hydrocarbon stream and the C5-C7-containing hydrocarbon stream separated from the reaction product respectively enter two fixed bed reactors for catalytic reaction. This process requires multiple reactors and no yield data are given.

CN102190548A discloses a method for improving the yield of low-carbon olefin in a process for preparing olefin from methanol. Raw material methanol enters a first fast fluidized bed reaction zone to obtain a product material flow I and a deactivated catalyst; the deactivated catalyst enters a riser reaction zone after being regenerated, contacts with hydrocarbon with more than four carbon atoms, and the generated product and the catalyst enter a second fast fluidized bed reaction zone to contact with the hydrocarbon with more than four carbon atoms and part of the regenerant to generate a product material flow II and a pre-deposited carbon catalyst; and mixing the product material flows I and II, entering a separation section, and returning the pre-deposited carbon catalyst to the first fast bed reaction zone. The catalyst used in the method is SAPO-34, and the selectivity of the low-carbon olefin can reach 90.33 percent at most. When SAPO-34 and SAPO-18 were used in example 11, the yield of low carbon olefins reached 88.22%.

CN112299939A discloses a method and a system for preparing olefin from methanol, which comprises a methanol-to-olefin reactor, a cracking reactor, a regenerator, and a gas-solid separator, wherein the feed of the cracking reactor is C4+ hydrocarbons. The system divides the spent catalyst (carbon-containing catalyst) from the cracking reactor into two streams, namely the methanol removal reactor and the regenerator, and compared with the prior art, the spent catalyst to the regenerator increases the circulation amount of the catalyst, reduces the coke rate, and simultaneously provides enough cracking heat for cracking C4+ hydrocarbons by a large amount of the regenerant from the regenerator, thereby finally improving the total yield of ethylene and propylene. The method is additionally provided with a cracking reactor for converting C4+ hydrocarbon, the catalyst grade of the example is SMC-001, the active component is SAPO-34, and the unit consumption of methanol in the example is about 2.65.

CN102875285A discloses a method for catalytically converting methanol and light naphtha into low-carbon olefins. The method comprises the steps of converting raw material light naphtha into low-carbon olefin in a riser reaction zone, enabling a product material flow and a catalyst to enter a raw material methanol reaction zone, enabling the raw material methanol reaction zone to be a turbulent bed or a fast bed, enabling a part of formed spent catalyst to return to the methanol reaction zone, enabling a part of the formed spent catalyst to go to a regenerator for regeneration, and enabling the regenerated catalyst to return to the riser reaction zone. The method is used for solving the problem of low yield of low-carbon olefin when two raw materials of methanol and naphtha are coupled. The catalyst used in the method is a ZSM-5 molecular sieve catalyst, and the carbon-based yield of the low-carbon olefin reaches 53.19 percent.

In a word, the method for improving the yield of the low-carbon olefin by the methanol-to-olefin technology at present mainly comprises the steps of catalytically cracking or steam cracking the byproduct C4 and above hydrocarbons generated in the reaction to generate ethylene and propylene, and because the carbon-deposited SAPO molecular sieve catalyst is more favorable for the methanol-to-olefin reaction, and the high-activity SAPO molecular sieve regenerant is more favorable for the hydrocarbon cracking reaction, the high-activity SAPO molecular sieve regenerant from the regenerator is usually pre-deposited with carbon in the C4+ hydrocarbon cracking reactor, and then enters the methanol reactor.

Disclosure of Invention

The invention aims to provide a process method for preparing low-carbon olefins such as ethylene, propylene and the like by using methanol as a raw material. The method simplifies equipment, fully utilizes reaction heat effect, greatly reduces energy consumption of the device, can obtain ethylene and propylene products with high yield, produces MTBE (methyl tert-butyl ether) and aromatic hydrocarbon as byproducts, and greatly improves economic benefit of refineries.

In order to achieve the above object, the present invention comprises the steps of:

(1) the method comprises the following steps of (1) vaporizing and preheating raw material methanol, then feeding the raw material methanol into a fast fluidized bed reactor, reacting to generate product gas containing low-carbon olefin under the action of a modified ZSM-5 molecular sieve catalyst, and simultaneously obtaining a spent catalyst;

(2) after the entrained catalyst is recovered by the gas-solid rapid separation of the product gas, the product gas flows out from the top of the settler and enters a reaction product separation system to obtain target products of ethylene, propylene, C4, C five and aromatic oil; the four-carbon de-etherification device reacts to generate an MTBE product, the five carbon and the four carbon after etherification are returned to the reactor together with the lifting steam through the lifting pipe, and the target products of ethylene and propylene are generated through cracking under the action of the catalyst;

(3) the spent catalyst is divided into two parts after passing through a gas-solid rapid separation device, a settler and a stripper, one part enters a regenerator to be burnt and regenerated to obtain a regenerated catalyst, the other part is used as a circulating spent agent and is mixed with the regenerated catalyst from the regenerator, and the mixed agent returns to the reactor through a riser.

In the invention, the reaction of preparing low-carbon olefin from methanol and the reaction of preparing ethylene and propylene by cracking C4 and C4 after ether are carried out in the same reactor, and a reaction regeneration system and a set of reaction product separation system are shared.

The invention adopts a fast fluidized bed reactor with a riser and a matched regenerator. The reactor mainly generates a reaction for preparing low-carbon olefin from methanol and a reaction for preparing ethylene and propylene by cracking C five and C four after ether, wherein the strong exothermic reaction directly provides heat for the strong endothermic reaction, the reaction heat effect is reduced, the cracking reaction temperature is reduced, and the yield of the low-carbon olefin, particularly the propylene, is improved.

In the step (1) of the method, raw material methanol enters a fast fluidized bed reactor from the lower part of the reactor to generate target products of ethylene and propylene.

In the step (2), the mixed hydrocarbon of carbon five and carbon four after etherification returns to the reactor through a riser along with the lift steam, and the target products of ethylene and propylene are generated through cracking.

The raw material methanol entering the reactor can also be a mixed material of methanol and/or dimethyl ether. A proper amount of water vapor can be added into the raw materials to reduce the coking and deactivation of the catalyst.

The mixed hydrocarbon material entering the reactor can be the hydrocarbon with four and/or more than four carbon atoms produced by the device, and can also be the hydrocarbon with four and/or more than four carbon atoms from other sources.

In the present invention, the catalyst is circulated between the fast fluidized bed reactor and the associated regenerator.

The regenerant is mixed with the circulating spent regenerant from the stripping section of the settler through the regeneration stripping section, the regenerant slide valve and the stripping section of the settler, and the mixture returns to the fast fluidized bed reactor through the riser. Under the action of the mixing agent, methanol quickly reacts to generate low-carbon olefin, the ether is cracked by four carbon five to generate ethylene and propylene, and meanwhile, a spent catalyst containing carbon is formed.

The spent catalyst and the reaction product flow out from the top of the reactor together, the spent catalyst is divided into two parts after passing through a gas-solid rapid separation device, a settler and a stripper, one part enters a regenerator for scorching regeneration to obtain a regenerated catalyst, the other part is used as a circulating spent catalyst and is mixed with the regenerated catalyst from the regenerator, and the mixture returns to the reactor through a riser.

The mixture entering the reactor through the riser comprises a circulating spent catalyst and a regenerated catalyst, wherein the circulating amount of the spent catalyst is 1-10 times of that of the regenerated catalyst.

According to the invention, the catalyst-to-alcohol ratio of the fast fluidized bed reactor can be increased by increasing the circulation amount of the spent catalyst, the density of a catalyst bed layer is increased, and the proper carbon content of the catalyst is maintained, so that the reaction selectivity is improved, and the yield of the low-carbon olefin is increased.

In the invention, the mixed hydrocarbon of carbon five and carbon four after etherification in the step (2), the mixed agent of the recycling spent catalyst and the regenerated catalyst in the step (3) and the lifting steam enter the lifting pipe. The riser mainly plays three roles: firstly, the above-mentioned mixed hydrocarbon and mixing agent are quickly mixed, secondly, the fluidization state and flow rate of catalyst fed into reactor are regulated, thirdly, the steam quantity is regulated and raised, reaction residence time and reaction depth are controlled so as to raise conversion rate of methyl alcohol and remilled hydrocarbon and improve selectivity of low-carbon olefin.

In the fast fluidized bed reactor, the reaction pressure is 0.01-0.5 MPa (gauge pressure), the reaction temperature is 450-550 ℃, and the alcohol-solvent ratio is 2: 1-3: 1. The regeneration temperature of the matched regenerator is 580-650 ℃, the operation pressure is 0.1-0.5 MPa, and the average residence time of the catalyst is 10-30 min.

The catalyst is a modified ZSM-5 molecular sieve catalyst, and the modified element is at least one of I A group, V A group, II B group, VIB group and rare earth element. Based on the total weight of the catalyst, the catalyst contains 40-90% of molecular sieve, 10-50% of clay, 5-20% of binder and 0.1-10% of modifying elements. The clay is well known to those skilled in the art, and can be one or a mixture of kaolin, diatomite, montmorillonite, bentonite and attapulgite; the binder is one or a mixture of more of pseudo-boehmite, aluminum sol, silicon-aluminum sol and water glass; the modifying element may be present in the catalyst in the form of one or more of an oxide, phosphate, phosphite, basic phosphate or acid phosphate of the metal.

The catalyst of the invention can be prepared by a general method: firstly, respectively pulping and mixing a molecular sieve and clay with water to form slurry; adding the modified element precursor into the molecular sieve slurry, pulping and mixing uniformly; adding a binder into the clay slurry, pulping, uniformly mixing, adding the molecular sieve slurry, and continuously pulping and uniformly mixing to prepare catalyst slurry; spray drying and forming the catalyst slurry; and roasting or washing and drying the formed microspheres to obtain the molecular sieve catalyst.

In the invention, a reaction product flows out from the top of the fast fluidized bed reactor, exchanges heat with the recycled carbon five, the ether carbon four and the raw material methanol and is cooled, and then enters the quenching tower. The two-stage heat exchange fully utilizes the heat brought by the reaction product, preheats two feeds of the fast fluidized bed reactor, and simultaneously, the temperature of the product is cooled to the proper range of the feed of the quenching tower.

And compressing the gas at the top of the quenching tower, and then feeding the compressed gas into a subsequent separation system to separate dry gas, ethylene, propylene, C4, C five and aromatic oil. The dry gas is recycled or emptied; ethylene and propylene products are discharged from the device; a C4 de-etherification device, and the byproduct isobutene reacts to generate an MTBE product; heating the mixed hydrocarbon of C five and C four after the etherification, then returning the heated mixed hydrocarbon to the fast fluidized bed reactor along with the lifting steam, and continuously reacting to generate target products of ethylene and propylene; the byproduct aromatic oil can be used as a high-octane gasoline component.

The invention has the following effects:

(1) the reaction of preparing low-carbon olefin and ether from methanol and then preparing ethylene and propylene from four-carbon five-cracking is carried out in the same reactor, and one reaction regeneration system and one set of separation system are shared, so that the equipment is simplified, simultaneously, the reaction heat is fully utilized, the energy consumption of the device is greatly reduced, and the selectivity and the yield of target products of ethylene and propylene are improved.

(2) The invention adopts a fast fluidized bed reactor with a lifting pipe, the raw material methanol is fast reacted, and the gas and the solid are fast separated, thereby reducing the yield of dry gas and increasing the yield of ethylene and propylene.

(3) The mixture entering the reactor through the riser in the invention comprises two parts of a circulating spent catalyst and a regenerated catalyst. The catalyst bed density can be improved and the proper carbon content of the catalyst can be maintained by increasing the circulation amount of the spent catalyst and increasing the catalyst-to-alcohol ratio of the fast fluidized bed reactor, thereby improving the reaction selectivity and increasing the yield of the low-carbon olefin.

(4) Compared with the prior art for preparing olefin from methanol, the invention adopts the modified ZSM-5 molecular sieve catalyst, so that the coke is less (less than 1 percent), the dry gas is less, and the propylene selectivity is high; more propylene and ethylene are produced, a byproduct isobutylene is produced, and the isobutylene generates an MTBE product through an etherification device, so that the economic benefit is further improved; c four and C five after the etherification return to the fast fluidized bed reactor, continue the cracking reaction and produce the target product, ethylene and propylene selectivity and yield are higher.

(5) The invention can obtain ethylene and propylene products with high yield and byproducts MTBE and aromatic hydrocarbon, has the advantages of simple equipment, convenient operation and lower energy consumption, and is suitable for the industrial production of low-carbon olefin. When the method is applied to industry, the conversion rate of methanol can reach 99.9%, and the yield of ethylene and propylene can reach 89%.

Drawings

FIG. 1 is a schematic process flow diagram of the method of the present invention, but the present invention is not limited thereto.

1-raw material heat exchanger, 2-methanol steam drum, 3-methanol vaporizer, 4-methanol heating furnace, 5-fast fluidized bed reactor, 6-regenerator, 7-reaction product heat exchanger, 8-remill heating furnace, 9-quench tower, 10-liquid separation tank, 11-compressor, 12-separation system, 13-etherification device, 14-settling tank and 15-methanol recovery tower.

The process flow of the method shown in figure 1 is as follows:

the raw material methanol is vaporized and preheated, then enters a fast fluidized bed reactor, and is in contact reaction with a catalyst to generate a product gas containing low-carbon olefin, and a spent catalyst is obtained at the same time;

after the entrained catalyst is recovered by the gas-solid rapid separation of the product gas, the product gas flows out from the top of the settler and enters a reaction product separation system to obtain target products of ethylene, propylene, C4, C five and aromatic oil; the four-carbon de-etherification device reacts to generate an MTBE product, the five carbon and the four carbon after etherification are returned to the reactor together with the lifting steam through the lifting pipe, and the target products of ethylene and propylene are generated through cracking under the action of the catalyst;

the spent catalyst is divided into two parts after passing through a gas-solid rapid separation device, a settler and a stripper, one part enters a regenerator to be burnt and regenerated to obtain a regenerated catalyst, the other part is used as a circulating spent agent and is mixed with the regenerated catalyst from the regenerator, and the mixed agent returns to the reactor through a riser.

FIG. 2 is a schematic diagram of the structure of a fluidized bed reactor and a mating regenerator of the present invention.

1-a reaction product outlet, 2-a reactor cyclone separator, 3-a settling tank, 4-a stripper, 5-a stripping steam inlet, 6-a spent agent circulation vertical pipe, 7-a spent agent vertical pipe, 8-a spent agent slide valve, 9-a spent agent circulation slide valve, 10-a steam/ether lifting carbon four/carbon five inlet, 11-a lifting pipe, 12-a methanol/steam inlet, 13-a fast fluidized bed reactor, 14-a reaction heat extractor, 15-a reactor rough rotation, 16-a regenerant slide valve, 17-a spent agent conveying pipe, 18-a regeneration gas extractor, 19-a gas stripping nitrogen, 20-a regeneration heat extractor, 21-a regeneration air inlet, 22-a regeneration dense phase bed, 23-a regenerant cyclone separator, 24-a regenerator settling tank, 25-CO boiler, 26-regenerated flue gas outlet.

Detailed Description

The present invention will be further described with reference to the following examples, but the present invention is not limited thereto.

Specification of raw materials

(1) The test raw material is a mixed feed composed of industrial methanol, carbon four and carbon five, and the mixing ratio is 70: 25: 5 respectively. Wherein carbon four is selected from ether rear carbon four of Ningxia petrochemical catalytic cracking unit, and the composition is shown in table 1; the carbon five is taken from raw material carbon five obtained by etherifying Ningxia petrochemical light gasoline.

(2) Catalyst type XMTO-1, with a phi 10 μm sphere appearance. The catalyst is produced by green chemical technology of Beijing Huilltrigi, and contains 56.8% of ZSM-5 and 1.5% of P₂O₅、2.8％K₂O, 2.8 percent of CdO, 0.46 percent of ZnO and the balance of Al₂O₃. The ZSM-5 molecular sieve is synthesized by an in-situ crystallization method, and the silica-alumina ratio is 200.

Example 1

The experimental data in this example illustrate the performance of a method for producing light olefins from methanol.

The test device is a riser reactor with 10kg of catalyst inventory, four carbon and five carbon after test raw materials of methanol, water and ether are respectively pumped into a preheating furnace by a metering pump, then the raw materials enter the riser reactor from the lower part of the reactor, the pressure of an oil-gas mixture generated by reaction is controlled by a regulating valve through heat exchange, liquid generated by the reaction is separated and weighed through a condensation and gas-liquid separator, the gas is measured by a wet flowmeter, the liquid and the gas are sampled and then analyzed by gas chromatography, and the yield (based on the weight of the raw material of methanol) is calculated.

The flow rate of the raw material methanol is 3kg/h, the preheating temperature is 350 ℃, the reaction temperature is 520 ℃, and the reaction pressure is 0.1MPa (gauge pressure). Continuously reacting for 7 days, balancing the clamped materials every day, taking 2 times of reaction gas for composition analysis, and collecting 1 time of liquid for composition analysis; after 7 days of reaction, the coke yield was calculated. Table 2 is the average data for 7 days.

TABLE 1 post C four composition of ether

Name (R)	Volume composition, v%
		Carbon III	0.45
N-butane	12.62
		Isobutane	39.23
N-butene	16.62
		Isobutene	0.84
Butene of trans-butene	17.06
		Cis-butenediol	12.8
Carbon five	0.38
		Total of	100

TABLE 2 reaction conditions and product distribution of the examples

Test number	Example 1
		Catalyst and process for preparing same	XMTO-1
Reaction temperature of	520
		Reaction pressure, MPa	0.1
Space velocity of methanol feed h^-1	0.3
		Proportion of water vapor in wt%	66.7
Distribution of reaction products in wt%
		Hydrogen gas	0.04％
Methane	0.39％
		Ethane (III)	0.20％
Ethylene	4.25％
		Propane	0.40％
Propylene (PA)	14.85％
		Isobutane	2.88％
N-butane	0.36％
		Butene of trans-butene	2.18％
N-butene	1.24％
		Isobutene	2.88％
Cis-butenediol	1.89％
		C5+ gasoline	7.58％
Carbon monoxide	0.02％
		Carbon dioxide	0.01％
Methanol	0.01％
		Water (W)	60.20％
Coke	0.62％
		Total of	100

Claims

1. a method for preparing light olefins from methanol, comprising the following steps:

(1) The raw methanol enters the fast fluidized bed reactor after being vaporized and preheated, and under the action of the modified ZSM-5 molecular sieve catalyst, the reaction generates a product gas containing low-carbon olefins, and the catalyst to be produced is obtained at the same time;

(2) the product gas flows out from the top of the settler after recovering the entrained catalyst through gas-solid rapid separation, and enters the reaction product separation system to obtain target products ethylene and propylene, C4, C5 and aromatic oil; C4 de-etherification device The reaction generates MTBE products, and after C5 and ether, C4 is returned to the reactor through the riser together with the lifting steam, and under the action of the catalyst, cracked to generate the target products ethylene and propylene;

(3) The to-be-grown catalyst is divided into two strands after the gas-solid separation, settler and stripper, one strand enters the regenerator for coking regeneration to obtain a regenerated catalyst, and the other strand is used as a circulating standby agent, which is combined with the regenerator from the regenerator. The regenerated catalyst is mixed, and the mixture is returned to the reactor through the riser.

2. method according to claim 1, it is characterized in that the reaction that methanol makes light olefin and the reaction of C5, ether rear C4 cracking to make ethylene propylene are carried out in same reactor, and share a reaction regeneration system and A set of reaction product separation system.

3. method according to claim 1, it is characterized in that the reaction that mainly takes place in the fast fluidized bed reactor is the reaction that methanol makes light olefins and C5, the reaction of C4 cracking to make ethylene propylene after ether, wherein strong exothermic reaction The heat is directly provided for the strong endothermic reaction, the thermal effect of the reaction is reduced, the temperature of the cracking reaction is lowered, and the yield of light olefins, especially propylene is improved.

4. method according to claim 1, is characterized in that in step (1), raw material methanol enters fast fluidized bed reactor from reactor bottom, generates target product ethylene and propylene; After carbon five and ether in step (2) The mixed hydrocarbons of C4 are returned to the reactor through the riser together with the lifting steam, and cracked to generate the target products ethylene and propylene.

5. The method according to claim 1, characterized in that in step (3), the mixed agent entering the reactor through the riser comprises two parts, the circulating unborn agent and the regenerated catalyst, wherein the circulating amount of the unborn agent is the regenerant circulation 1 to 10 times the amount.

6. the method according to claim 1 and 5 is characterized in that, can increase the agent-alcohol ratio of the fast fluidized bed reactor by increasing the circulating amount of the unborn agent, improve the catalyst bed density, and keep the suitable carbon content of the catalyst , thereby improving the reaction selectivity and increasing the yield of light olefins.

7. method according to claim 1, it is characterized in that the mixed hydrocarbon of carbon four after carbon five and ether in step (2), the mixture of circulating unborn agent and regenerated catalyst in step (3), and boosting The steam enters the riser; the riser has three main functions: one is the rapid mixing of the above-mentioned mixed hydrocarbons and the admixture; the other is to adjust the fluidization state and flow rate of the catalyst entering the reactor; Reaction residence time and reaction depth, thereby increasing the conversion of methanol and recycled hydrocarbons and improving the selectivity of light olefins.

8. The method according to claim 1, characterized in that the reaction pressure of the fast fluidized bed reactor is 0.01-0.5MPa (gauge pressure), the reaction temperature is 450-550°C, and the alcohol-agent ratio is 2:1-3:1.

9. method according to claim 1, is characterized in that in step (1), the raw material methanol that enters reactor can also be the mixture material of methyl alcohol and/or dimethyl ether; Can add appropriate amount of steam in raw material, with Reduce catalyst coking and deactivation.

10. method according to claim 1, is characterized in that in step (2), the mixed hydrocarbon material that enters reactor can be the carbon four and/or more than carbon four hydrocarbons that this device is self-produced, also can be other sources C4 and/or C4+ hydrocarbons.

11. method according to claim 1 is characterized in that described catalyst is modified ZSM-5 molecular sieve catalyst, and its modified element is from at least one of IA family, VA family, IIB family, VIB family, rare earth element .