CN113429250A

CN113429250A - System and method for co-producing ethylene, propylene and butylene through catalytic dehydration of methanol

Info

Publication number: CN113429250A
Application number: CN202110867460.4A
Authority: CN
Inventors: 李学刚; 肖文德; 阎建民; 罗漫
Original assignee: Shanghai Jiaotong University
Current assignee: Shanghai Runhe Shengjian Petrochemical Engineering Technology Co.,Ltd.
Priority date: 2021-07-30
Filing date: 2021-07-30
Publication date: 2021-09-24

Abstract

The invention relates to a system and a method for co-producing ethylene, propylene and butylene through catalytic dehydration of methanol. The system comprises a reaction unit and a separation unit, wherein the reaction unit comprises a pre-reactor, a process steam tower and a main reactor, and the separation unit comprises a quencher, a compressor and a separation tower; the main reactor adopts a ZSM-5 molecular sieve catalyst, the separation unit comprises 3 product towers, namely an ethylene tower, a propylene tower and a butylene tower, high-purity ethylene, propylene and butylene products are respectively obtained, part of ethane, propane, butane, C five and C six hydrocarbons return to the main reactor, and other materials are extracted as byproducts. Compared with the prior MTO or MTP technology, the method can produce propylene and ethylene, also can co-produce butylene, simultaneously reduces the amount of circulating hydrocarbon, improves the reaction efficiency and reduces the unit energy consumption.

Description

System and method for co-producing ethylene, propylene and butylene through catalytic dehydration of methanol

Technical Field

The invention belongs to the technical field of chemical industry, and particularly relates to a system and a method for co-producing ethylene, propylene and butylene through catalytic dehydration of methanol.

Background

Low-carbon olefins, including ethylene, propylene, butylene and the like, are important chemical basic raw materials, are monomers for producing three synthetic materials (synthetic resin, synthetic fiber and synthetic rubber), and are also important raw materials or intermediates for synthesizing fine chemicals such as detergents, medicines, fuels, essences and the like.

The production of lower olefins has in the past relied primarily on petroleum routes, including steam cracking and catalytic cracking processes. Because of the limited petroleum reserves in China, the olefin market is full of uncertainty due to the wide fluctuation of international petroleum prices. In recent years, non-oil pipelines represented by coal-based methanol to olefin/methanol to propylene (MTO/MTP) and Propane Dehydrogenation (PDH) have been rapidly developed, and the diversity of low-carbon olefin sources in China has been increased. However, the main products of MTO, MTP, PDH, etc. technologies that have been commercialized are ethylene and propylene. Taking the MTP technology developed by Lurgi as an example, the main product is propylene, and C4-C6 including butene are returned to the main reactor.

In recent years, with the improvement of ecological environmental protection consciousness, biodegradable materials are paid more and more attention and attention, and the biodegradable materials have a prospect of replacing traditional polyolefin in the fields of packaging, agricultural mulching films and the like. The butylene glycol serving as a butylene derivative is an important biodegradable material monomer, so that the expansion of the capacity and the source diversity of the butylene becomes practical.

Patent CN201710438828 discloses a method and a system for preparing olefin from methanol, wherein a part of the obtained product stream containing ethylene and propylene is returned to the crude methanol as a conditioning gas after heat exchange and water washing, and the other part is subjected to olefin separation to obtain ethylene and propylene. CN200910172577 and CN200910172577 respectively disclose a method and a process for preparing olefin by methanol dehydration, and the main idea is that methanol is subjected to catalytic distillation reaction to obtain dimethyl ether material flow, then the dimethyl ether material flow enters a moving bed reactor to be contacted and reacted with a ZSM-5 zeolite molecular sieve catalyst, ethylene and propylene products obtained by product separation are discharged from a device, the obtained C4 hydrocarbon material flow and C5-C7 hydrocarbon material flow respectively enter two fixed bed reactors, and are further reacted to obtain low-carbon hydrocarbons and return the low-carbon hydrocarbons to a separation unit. CN201910509571 discloses a method for increasing the yield of olefins in the technology of methanol to propylene, namely, after MTP product separation, the obtained C2 hydrocarbon (including ethylene), C4 (including butylene) and C5-C7 are returned to the MTP reactor as the recycle hydrocarbon product stream to achieve the purpose of increasing the yield of olefins, i.e., propylene. The above patent is characterized in that only propylene (and ethylene) products are produced from the separation unit, and other hydrocarbons including C4 are returned to the main reactor or enter another reactor for further reaction, so as to improve the yield of the main product propylene (and ethylene) without producing butylene products.

Disclosure of Invention

The invention aims to provide a system and a method for co-producing ethylene, propylene and butylene by catalytic dehydration of methanol.

According to the invention, the products of catalytic dehydration of methanol are separated, high-purity ethylene, propylene and butylene products are obtained by coproduction, and meanwhile, part of ethane, part of propane, part of butane and part of C five and C six hydrocarbons obtained by separation are returned to the main reactor, so that the yield of the target product is improved, and the problem that only propylene (and ethylene) is produced but butylene is not produced in the traditional MTO or MTP technology is solved.

The purpose of the invention can be realized by the following technical scheme:

the invention firstly provides a system for coproducing ethylene, propylene and butylene by catalytic dehydration of methanol, which comprises a reaction unit and a separation unit,

the reaction unit comprises a pre-reactor, a process steam tower and a main reactor,

the separation unit comprises a chiller and a plurality of separation columns,

the pre-reactor is used for partial dehydration reaction of methanol, the process steam tower is used for heating and vaporizing water from the quencher into steam,

the main reactor is used for contacting and reacting the reaction products of the pre-reactor and part of ethane, part of propane, part of butane and part of carbon five and carbon six hydrocarbons and steam from the separation unit with a catalyst;

the quencher is used for receiving the product of the main reactor after heat exchange and dehydrating the product to obtain a hydrocarbon mixture,

the separation tower is used for separating the compressed hydrocarbon mixture and comprises an ethylene tower, a propylene tower, a butylene tower, a four decarburization tower, a three decarburization tower, a two decarburization tower, a demethanizer and a six decarburization tower,

in the separation tower, an ethylene tower, a propylene tower and a butylene tower are respectively used for obtaining high-purity ethylene, propylene and butylene products,

and the other separation towers are used for separating different mixtures, part of ethane, part of propane and part of butane obtained by the separation unit and part of C five and C six hydrocarbons are returned to the main reactor, and other materials are produced as byproducts.

In one embodiment of the present invention, the pre-reactor is a fixed bed reactor using a catalyst selected from at least one of zeolite, alumina or aluminosilicate catalyst, preferably alumina.

In one embodiment of the invention, the main reactor is selected from one of a single-stage or multi-stage axial fixed bed, a radial fixed bed, a fluidized bed or a moving bed.

In one embodiment of the invention, the main reactor is selected from a multi-stage in-line axial fixed bed reactor with side feed, a single-stage multi-channel axial fixed bed reactor or a radial fixed bed reactor.

In one embodiment of the invention, the separation unit further comprises a compressor for compressing the hydrocarbon mixture obtained by the chiller and then feeding the compressed hydrocarbon mixture into the separation column.

In one embodiment of the invention, a heat exchanger is arranged between the reaction unit and the separation unit and used for exchanging heat between products of the main reactor entering the quencher. In one embodiment of the invention, the heat exchanger may be a dividing wall heat exchanger.

In one embodiment of the invention, the quench cooler is a water wash column or a dividing wall heat exchanger.

In one embodiment of the present invention, the ethylene column, the propylene column, the butene column, the four decarburization columns, the three decarburization columns, the two decarburization columns, the demethanizer column and the six decarburization columns in the separation column are connected in different manners according to the order of dealkylation.

For example, a front debutanization separation sequence, a front depropanization separation sequence, or a front deethanization separation sequence may be selected.

In one embodiment of the invention, the process steam column is used to heat and vaporize water from the chiller into steam.

The invention also provides a method for coproducing ethylene, propylene and butylene by catalytic dehydration of methanol, which is carried out based on the system and comprises the following steps:

(1) a pre-reaction stage: the methanol enters a pre-reactor to carry out partial dehydration reaction to obtain a mixture of the methanol, the dimethyl ether and the water;

(2) a main reaction stage: the mixture of methanol, dimethyl ether and water from the pre-reaction stage and the steam from the process steam tower enter a main reactor to contact and react with a catalyst to obtain a mixture containing ethylene, propylene and butylene;

(3) an oil-water separation stage: the mixture containing ethylene, propylene and butylene from the main reaction stage enters a quencher, the temperature is reduced, the moisture is removed, a hydrocarbon mixture is obtained, the removed part of water returns to the process evaporation tower, and the rest water is extracted from the system;

(4) a compression and rectification stage: compressing a hydrocarbon mixture from an oil-water separation stage by a compressor, cutting the hydrocarbon mixture by a four decarburization tower, a three decarburization tower, a two decarburization tower, a butene tower, a propylene tower, a demethanizer, an ethylene tower and a six decarburization tower to obtain high-purity ethylene, high-purity propylene and high-purity butene, discharging the obtained high-purity ethylene, high-purity propylene and high-purity butene from a system as products, returning mixed hydrocarbons formed by part of carbon five and carbon six hydrocarbons, part of butane, part of propane and part of ethane to a main reactor, and taking the rest carbon five and carbon six hydrocarbons, butane, propane, ethane and all methane and high-carbon hydrocarbons as byproducts to be extracted from the system.

In one embodiment of the invention, the outlet temperature of the pre-reactor is 150-450 ℃, the operating pressure is 0.1-0.5 MPa, the outlet temperature of the main reactor is 450-550 ℃, and the operating pressure is 0.1-0.5 MPa.

In one embodiment of the invention, the process steam tower outlet temperature is 100-300 ℃.

In one embodiment of the invention, the mixture of methanol, dimethyl ether and water is further subjected to at least one heat exchanger to recover heat before entering a quencher, and the temperature of the hydrocarbon mixture obtained at the outlet of the quencher is 30-90 ℃.

In one embodiment of the invention, the sequence in which the separation column performs the cut separation of the hydrocarbon mixture comprises a pre-debutanization separation sequence, a pre-depropanization separation sequence or a pre-deethanization separation sequence.

Compared with the prior art, the beneficial effects of the invention are embodied in the following aspects:

a high-purity butene product is cut from the C-Si material through the butene tower and is discharged out of the system, part of the residual butane returns to the main reactor, and the rest butane is discharged out of the system as a byproduct, so that the problem that only propylene (and ethylene) is produced but butene is not produced in the traditional methanol-to-olefin technology is solved, the amount of circulating hydrocarbon is reduced, the reaction efficiency is improved, and the unit energy consumption is reduced.

Drawings

FIG. 1: the system structure schematic diagram of the co-production of ethylene, propylene and butylene through catalytic dehydration of methanol in one embodiment of the invention.

FIG. 2: the system structure schematic diagram of the co-production of ethylene, propylene and butylene by catalytic dehydration of methanol in the embodiment 1 of the invention.

FIG. 3: the system structure schematic diagram of the co-production of ethylene, propylene and butylene by catalytic dehydration of methanol in the embodiment 2 of the invention.

FIG. 4: the system structure schematic diagram of the co-production of ethylene, propylene and butylene by catalytic dehydration of methanol in the embodiment 3 of the invention.

Reference numbers in the figures:

100. a reaction unit;

101. a pre-reactor 102, a main reactor 103 and a process steam tower;

200. a separation unit;

201. a chiller, 202, a first compressor, 203, a second compressor, 204, a four decarbonizing tower, 205, a three decarbonizing tower, 206, a two decarbonizing tower, 207, a butene tower, 208, a propylene tower, 209, a demethanizer, 210, an ethylene tower, 211 and a six decarbonizing tower.

1. Methanol, 2, methanol, a mixture of dimethyl ether and water, 3, steam, 4, methanol, dimethyl ether, a mixture of water, steam, 5, water, 6, a mixture comprising ethylene, propylene and butenes, 7, produced water, 8, a hydrocarbon mixture, 9, a compressed hydrocarbon mixture, 10, hydrocarbons of four and less carbons, 11, hydrocarbons of five and more carbons, 12, four, 13, hydrocarbons of three and less carbons, 14, a mixture of carbon dioxide and methane, 15, carbon three, 16, high purity butenes, 17, butane, 18, remaining butane, 19, part of butane, 20, propane, 21, remaining propane, 22, part of propane, 23, high purity propylene, 24, a mixture of compressed carbon two and methane, 25, methane, 26, carbon two, 27, high purity ethylene, 28, ethane, 29, part of carbon five and carbon six hydrocarbons, 30, remaining carbon five and carbon six hydrocarbons, 31, high carbon hydrocarbons, 32. carbon five and carbon six hydrocarbons, 33, mixed hydrocarbons, 34, remaining ethane, 35, part of ethane, 36, carbon four and above hydrocarbons, 37, compressed carbon three and below hydrocarbons, 38, carbon two and carbon three mixtures, 39, carbon two and methane mixtures, 40, carbon three and above hydrocarbons.

Detailed Description

Referring to fig. 1, the present invention firstly provides a system for co-production of ethylene, propylene and butylene by catalytic dehydration of methanol, comprising a reaction unit 100 and a separation unit 200, wherein the reaction unit 100 comprises a pre-reactor 101, a process steam tower 103 and a main reactor 102, the separation unit 200 comprises a quencher 201 and a plurality of separation towers, the pre-reactor 101 is used for partial dehydration reaction of methanol, the process steam tower 103 is used for heating and vaporizing water from the quencher 201 into steam 3, and the main reactor 102 is used for contacting and reacting reaction products of the pre-reactor 101 and part of ethane, part of propane, part of butane and part of carbon five and carbon six hydrocarbons and steam from the separation unit 200 with a catalyst; the chiller 201 is used for receiving the products of the main reactor 102 after heat exchange and dehydrating the products to obtain a hydrocarbon mixture, the separation columns are used for separating the compressed hydrocarbon mixture, the separation columns comprise an ethylene column 210, a propylene column 208, a butene column 207, a four decarbonization column 204, a three decarbonization column 205, a two decarbonization column 206, a demethanizer 209 and a six decarbonization column 211, the ethylene column 210, the propylene column 208 and the butene column 207 in the separation columns are respectively used for obtaining high-purity ethylene, propylene and butene products, the other separation columns are used for realizing separation of different mixtures, part of ethane, part of propane, part of butane and part of carbon five and carbon six hydrocarbons obtained by the separation unit 200 are returned to the main reactor 102, and the other materials are extracted as byproducts.

In one embodiment of the present invention, the pre-reactor 101 is a fixed bed reactor using a catalyst selected from at least one of zeolite, alumina or aluminosilicate catalyst, preferably alumina.

In one embodiment of the present invention, the main reactor 102 is selected from one of a single-stage or multi-stage axial fixed bed, a radial fixed bed, a fluidized bed, or a moving bed.

In one embodiment of the present invention, the separation unit 200 further comprises a compressor for compressing the hydrocarbon mixture obtained from the chiller 201 and then feeding the compressed hydrocarbon mixture into the separation column.

In one embodiment of the present invention, a heat exchanger is further disposed between the reaction unit 100 and the separation unit 200, and the heat exchanger is used for exchanging heat between the product of the main reactor 102 entering the chiller 201. In one embodiment of the invention, the heat exchanger may be a dividing wall heat exchanger.

In one embodiment of the present invention, the chiller 201 is a water wash column or a dividing wall heat exchanger.

In one embodiment of the present invention, the ethylene column 210, the propylene column 208, the butene column 207, the four decarburization columns 204, the three decarburization columns 205, the two decarburization columns 206, the demethanizer 209 and the six decarburization columns 211 in the separation columns are connected in different manners according to the order of dealkylation. For example, a front debutanization separation sequence, a front depropanization separation sequence, or a front deethanization separation sequence may be selected.

Referring to fig. 1, the invention also provides a method for co-producing ethylene, propylene and butylene by catalytic dehydration of methanol, which is carried out based on the system and comprises the following steps:

(1) a pre-reaction stage: the methanol enters a pre-reactor 101 to carry out partial dehydration reaction to obtain a mixture of methanol, dimethyl ether and water;

(2) a main reaction stage: a mixture formed by a mixture of methanol, dimethyl ether and water from the pre-reaction stage and steam from a process steam tower 103 enters a main reactor 102 to contact and react with a catalyst to obtain a mixture containing ethylene, propylene and butylene;

(4) a compression and rectification stage: after a hydrocarbon mixture from an oil-water separation stage is compressed by a compressor, the compressed hydrocarbon mixture is cut by a four decarburization tower 204, a three decarburization tower 205, a two decarburization tower 206, a butene tower 207, a propylene tower 208, a demethanizer 209, an ethylene tower 210 and a six decarburization tower 211, the obtained high-purity ethylene, high-purity propylene and high-purity butene are discharged from a system as products, the obtained mixed hydrocarbon formed by part of the five and six carbon hydrocarbons, part of butane, part of propane and part of ethane returns to a main reactor, and the rest of the five and six carbon hydrocarbons, butane, propane, ethane and all of methane and high carbon hydrocarbons are extracted from the system as byproducts.

In one embodiment of the invention, the outlet temperature of the pre-reactor 101 is 150-450 ℃, the operating pressure is 0.1-0.5 MPa, the outlet temperature of the main reactor 102 is 450-550 ℃, and the operating pressure is 0.1-0.5 MPa.

In one embodiment of the invention, the process steam tower 103 outlet temperature is 100 to 300 ℃.

In one embodiment of the invention, the mixture of methanol, dimethyl ether and water is further subjected to at least one heat exchanger to recover heat before entering the quencher 201, and the temperature of the hydrocarbon mixture obtained at the outlet of the quencher 201 is 30-90 ℃.

The invention is described in detail below with reference to the figures and specific embodiments.

It should be noted that all the directional indicators (such as up, down, left, right, front, and rear … …) in the embodiment of the present invention are only used to explain the relative position relationship between the components, the movement situation, etc. in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indicator is changed accordingly.

In addition, the descriptions related to "first", "second", etc. in the present invention are only for descriptive purposes and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the present invention, unless otherwise expressly stated or limited, the terms "connected," "secured," and the like are to be construed broadly, and for example, "secured" may be a fixed connection, a removable connection, or an integral part; the connection can be mechanical connection, electrical connection, physical connection or wireless communication connection; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In addition, the technical solutions in the embodiments of the present invention may be combined with each other, but it must be based on the realization of those skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination of technical solutions should not be considered to exist, and is not within the protection scope of the present invention.

Example 1

The embodiment provides a system for co-producing ethylene, propylene and butylene through catalytic dehydration of methanol, as shown in fig. 2, comprising a reaction unit 100 and a separation unit 200, wherein the reaction unit 100 comprises a pre-reactor 101, a process steam tower 103 and a main reactor 102, the separation unit 200 comprises a chiller 201, a first compressor 202, a second compressor 203 and a plurality of separation towers, and specifically, the separation towers comprise a four decarbonization tower 204, a three decarbonization tower 205, a two decarbonization tower 206, a butylene tower 207, a propylene tower 208, a demethanizer 209, an ethylene tower 210 and a six decarbonization tower 211.

In the embodiment, high-purity ethylene 27, high-purity propylene 23 and high-purity butene 16 are obtained by coproducing the system for coproducing ethylene, propylene and butylene through catalytic dehydration of methanol, part of ethane 35, part of propane 22, part of butane 19 and part of carbon five and carbon six hydrocarbons 29 are returned to the main reactor 102, and the rest produced water 7, the rest ethane 34, the rest propane 21, the rest butane 18, the rest carbon five and carbon six hydrocarbons 30, and all methane 25 and high-carbon hydrocarbons 31 are discharged from the system as byproducts.

In this embodiment, the pre-reactor 101 is a fixed bed reactor, and the catalyst used is γ -Al₂O₃. The reactor 102 is a multistage tandem axial fixed bed reactor with side feed, and employs a ZSM-5 molecular sieve catalyst. The process steam column 103 heats and vaporizes water 5 from the chiller 201 into steam 3. The quencher 201 is a water washing tower. The separation unit 200 takes the form of a front-end debutanizer separation sequence in which the separation columns include a four decarbonizer column 204, a three decarbonizer column 205, a two decarbonizer column 206, a butenes column 207, a propene column 208, a demethanizer column 209, an ethylene column 210, and a six decarbonizer column 211.

A chemical plant takes methanol as a raw material to perform catalytic dehydration and coproduce ethylene, propylene and butylene, and a system for performing catalytic dehydration and coproduction of ethylene, propylene and butylene by using methanol, which is shown in figure 2, is applied, and comprises the following steps:

(1) a pre-reaction stage: the methanol 1 enters a pre-reactor 101 to carry out partial dehydration reaction, the temperature of the outlet of the reactor is 250 ℃, and the operation pressure is 0.15MPa, so that a mixture 2 of the methanol, the dimethyl ether and the water is obtained;

(2) a main reaction stage: a mixture 4 of methanol, dimethyl ether, water and steam, which is formed by a mixture 2 of methanol, dimethyl ether and water from a pre-reaction stage and steam 3 from a process steam tower 103, enters a main reactor 102 to contact with a ZSM-5 molecular sieve catalyst and react, wherein the mass fraction of the water in the mixture 4 of the methanol, the dimethyl ether, the water and the steam is 20%, the outlet temperature of the process steam tower 103 is 250 ℃, the outlet temperature of the main reactor 102 is 460 ℃, and the operating pressure is 0.14MPa, so that a mixture 6 containing ethylene, propylene and butylene is obtained;

(3) an oil-water separation stage: the mixture 6 containing ethylene, propylene and butylene from the main reaction stage passes through a once dividing wall type heat exchanger to recover heat, the temperature is reduced to 200 ℃ and then enters a quencher 201, the temperature is reduced to 85 ℃ and the moisture is removed to obtain a hydrocarbon mixture 8, the removed part of water 5 returns to the process evaporation tower 103, and the rest produced water 7 is extracted from the system;

(4) a compression and rectification stage: the hydrocarbon mixture 8 from the oil-water separation stage is compressed by a first compressor 202 to obtain a compressed hydrocarbon mixture 9, the compressed hydrocarbon mixture 9 is cut into hydrocarbons 10 with four or less carbons and hydrocarbons 11 with five or more carbons by a four decarbonization tower 204, the hydrocarbons 10 with four or less carbons are cut into hydrocarbons 13 with three or less carbons and four 12 by a three decarbonization tower 205, the hydrocarbons 13 with three or less carbons are cut into a mixture 14 of carbon two and methane and carbon three 15 by a two decarbonization tower 206, the carbon four 12 is cut into high-purity butene 16 and butane 17 by a butene tower 207, the carbon three 15 is cut into high-purity propene 23 and propane 20 by a propene tower 208, the mixture 14 of carbon two and methane is compressed by a second compressor 203 to obtain a mixture 24 of carbon two and methane, the mixture 24 of carbon two and methane enters a demethanizer 209 after compression to be cut into methane 25 and carbon two 26, the carbon two 26 is cut into high-purity ethylene 27 and ethane 28 by an ethylene tower 210, the hydrocarbon 11 of five or more carbons is cut into the hydrocarbon 32 of five and six carbons and the hydrocarbon 31 of higher carbon by the six decarbonizing towers 211, and the hydrocarbon 32 of five and six carbons includes a part of the hydrocarbon 29 of five and six carbons and the hydrocarbon 30 of five and six carbons of the rest carbon.

Wherein a mixed hydrocarbon 33 formed by a part of the five-carbon six-hydrocarbon 29, a part of the butane 19, a part of the propane 22 and a part of the ethane 35 is returned to the main reactor 102, the remaining five-carbon six-hydrocarbon 30, the remaining butane 18, the remaining propane 21, the remaining ethane 34 and all of the methane 25 and the higher-carbon hydrocarbon 31 are extracted from the system as by-products, wherein the proportion of the ethane 35 to the ethane 28 is 0, the proportion of the propane 22 to the propane 20 is 30%, the proportion of the butane 19 to the butane 17 is 50%, the proportion of the five-carbon six-hydrocarbon 29 to the five-carbon six-hydrocarbon 32 is 80%, and the high-purity ethylene 27, the high-purity propylene 23 and the high-purity butene 16 are discharged from the system as products.

Example 2

The embodiment provides a system for co-producing ethylene, propylene and butylene through catalytic dehydration of methanol, as shown in fig. 3, comprising a reaction unit 100 and a separation unit 200, wherein the reaction unit 100 comprises a pre-reactor 101, a process steam tower 103 and a main reactor 102, the separation unit 200 comprises a chiller 201, a first compressor 202, a second compressor 203 and a plurality of separation towers, wherein the separation towers comprise a four decarburization tower 204, a three decarburization tower 205, a two decarburization tower 206, a butylene tower 207, a propylene tower 208, a demethanizer 209, an ethylene tower 210 and a six decarburization tower 211.

In this embodiment, the pre-reactor 101 is a fixed bed reactor, and the catalyst used is γ -Al₂O₃. The reactor 102 is a single-stage multi-channel axial fixed bed reactor and adopts ZSM-5 molecular sieve catalystAn oxidizing agent. The process steam column 103 heats and vaporizes water 5 from the chiller 201 into steam 3. The quencher 201 is a water washing tower. The separation unit 200 takes the form of a front-end depropanizer separation sequence in which the separation columns include a four decarbonizer column 204, a three decarbonizer column 205, a two decarbonizer column 206, a butenes column 207, a propene column 208, a demethanizer column 209, an ethylene column 210, and a six decarbonizer column 211.

A chemical plant takes methanol as a raw material to perform catalytic dehydration and coproduce ethylene, propylene and butylene, and a system for performing catalytic dehydration and coproduction of ethylene, propylene and butylene by using methanol, which is shown in figure 3, is applied, and comprises the following steps:

(1) a pre-reaction stage: the methanol 1 enters a pre-reactor 101 to carry out partial dehydration reaction, the temperature of the outlet of the reactor is 300 ℃, and the operation pressure is 0.2MPa, so that a mixture 2 of the methanol, the dimethyl ether and the water is obtained;

(2) a main reaction stage: a mixture 4 of methanol, dimethyl ether, water and steam, which is formed by a mixture 2 of methanol, dimethyl ether and water from a pre-reaction stage and steam 3 from a process steam tower 103, enters a main reactor 102 to contact with a ZSM-5 molecular sieve catalyst and react, wherein the mass fraction of the water in the mixture 4 of the methanol, the dimethyl ether, the water and the steam is 25 percent, the outlet temperature of the process steam tower 103 is 300 ℃, the outlet temperature of the main reactor 102 is 490 ℃, and the operating pressure is 0.19MPa, so that a mixture 6 containing ethylene, propylene and butylene is obtained;

(3) an oil-water separation stage: the mixture 6 containing ethylene, propylene and butylene from the main reaction stage passes through a double-dividing-wall type heat exchanger, the temperature is reduced to 180 ℃, then the mixture enters a quencher 201, the temperature is reduced to 75 ℃, moisture is removed, a hydrocarbon mixture 8 is obtained, the removed part of water 5 returns to the process evaporation tower 103, and the rest produced water 7 is extracted from the system;

(4) a compression and rectification stage: the hydrocarbon mixture 8 from the oil-water separation stage is compressed by a first compressor 202 to obtain a compressed hydrocarbon mixture 9, the compressed hydrocarbon mixture 9 is cut into hydrocarbons 13 with three or less carbons and hydrocarbons 36 with four or more carbons by a decarburization three tower 205, the hydrocarbons 13 with three or less carbons are compressed by a second compressor 203 to obtain hydrocarbons 37 with three or less carbons, the hydrocarbons 37 with three or less carbons enter a demethanizer 209 and are cut into a mixture 38 of methane 25 and three carbon two, the mixture 38 of three carbon two and three carbon two is cut into two carbon 26 and three carbon 15 by a decarburization two tower 206, the two carbon 26 is cut into high purity ethylene 27 and ethane 28 by an ethylene tower 210, the three carbon 15 is cut into high purity propylene 23 and propane 20 by a propylene tower 208, the hydrocarbons 36 with four or more carbons are cut into hydrocarbons 11 with four carbon 12 and five or more carbons by a decarburization four tower 204, the four carbon 12 is cut into high purity butene 16 and butane 17 by a butene tower 207, the hydrocarbon 11 of five or more carbons is cut into the hydrocarbon 32 of five and six carbons and the hydrocarbon 31 of higher carbon by the six decarbonizing towers 211, and the hydrocarbon 32 of five and six carbons includes a part of the hydrocarbon 29 of five and six carbons and the hydrocarbon 30 of five and six carbons of the rest carbon.

Wherein the obtained mixed hydrocarbon 33 formed by part of the five-carbon six-hydrocarbon 29, part of the butane 19, part of the propane 22 and part of the ethane 35 is returned to the main reactor 102, the rest of the five-carbon six-hydrocarbon 30, the rest of the butane 18, the rest of the propane 21, the rest of the ethane 34 and all of the methane 25 and the high-carbon hydrocarbon 31 are taken out of the system as byproducts, wherein the part of the ethane 35 accounts for 3 percent of the ethane 28, the part of the propane 22 accounts for 20 percent of the propane 20, the part of the butane 19 accounts for 40 percent of the butane 17, the part of the five-carbon six-hydrocarbon 29 accounts for 70 percent of the five-carbon six-hydrocarbon 32, and the high-purity ethylene 27, the high-purity propylene 23 and the high-purity butene 16 are taken out of the system as products.

Example 3

The embodiment provides a system for co-producing ethylene, propylene and butylene by catalytic dehydration of methanol, as shown in fig. 4, comprising a reaction unit 100 and a separation unit 200, wherein the reaction unit 100 comprises a pre-reactor 101, a process steam tower 103 and a main reactor 102, and the separation unit 200 comprises a chiller 201, a first compressor 202 and a plurality of separation towers. The separation tower comprises a four decarbonizing tower 204, a three decarbonizing tower 205, a two decarbonizing tower 206, a butene tower 207, a propylene tower 208, a demethanizer 209, an ethylene tower 210 and a six decarbonizing tower 211.

In this embodiment, the pre-reactor 101 is a fixed bed reactor, and the catalyst used is γ -Al₂O₃. The reactor 102 is a radial fixed bed reactor, employing a ZSM-5 molecular sieve catalyst. The process steam column 103 heats and vaporizes water 5 from the chiller 201 into steam 3. The quencher 201 is a water washing tower. The separation unit 200 takes the form of a front end deethanizer separation sequence in which the separation columns include a four decarbonizer column 204, a three decarbonizer column 205, a two decarbonizer column 206, a butenes column 207, a propene column 208, a demethanizer column 209, an ethylene column 210, and a six decarbonizer column 211.

A chemical plant takes methanol as a raw material to perform catalytic dehydration and coproduce ethylene, propylene and butylene, and a system for performing catalytic dehydration and coproduction of ethylene, propylene and butylene by using methanol, which is shown in figure 4, is applied, and comprises the following steps:

(1) a pre-reaction stage: the methanol 1 enters a pre-reactor 101 to carry out partial dehydration reaction, the temperature of the outlet of the reactor is 230 ℃, and the operation pressure is 0.12MPa, so that a mixture 2 of the methanol, the dimethyl ether and the water is obtained;

(2) a main reaction stage: a mixture 4 of methanol, dimethyl ether, water and steam, which is formed by a mixture 2 of methanol, dimethyl ether and water from a pre-reaction stage and steam 3 from a process steam tower 103, enters a main reactor 102 to contact with a ZSM-5 molecular sieve catalyst and react, wherein the mass fraction of the water in the mixture 4 of the methanol, the dimethyl ether, the water and the steam is 18 percent, the outlet temperature of the process steam tower 103 is 280 ℃, the outlet temperature of the main reactor 102 is 460 ℃, and the operating pressure is 0.11MPa, so that a mixture 6 containing ethylene, propylene and butylene is obtained;

(3) an oil-water separation stage: the mixture 6 containing ethylene, propylene and butylene from the main reaction stage passes through a double-dividing-wall type heat exchanger, the temperature is reduced to 150 ℃, then the mixture enters a quencher 201, the temperature is reduced to 60 ℃, moisture is removed, a hydrocarbon mixture 8 is obtained, the removed part of water 5 returns to the process evaporation tower 103, and the rest produced water 7 is extracted from the system;

(4) a compression and rectification stage: the hydrocarbon mixture 8 from the oil-water separation stage is compressed by a first compressor 202 to obtain a compressed hydrocarbon mixture 9, the compressed hydrocarbon mixture 9 is cut into a carbon two and methane mixture 39 and hydrocarbons 40 with three or more carbon atoms by a decarbonizing second tower 206, the carbon two and methane mixture 39 is cut into methane 25 and carbon two 26 by a demethanizer 209, the carbon two 26 is cut into high-purity ethylene 27 and ethane 28 by an ethylene tower 210, the hydrocarbons 40 with three or more carbon atoms are cut into carbon three 15 and hydrocarbons 36 with four or more carbon atoms by a decarbonizing third tower 205, the carbon three 15 is cut into high-purity propylene 23 and propane 20 by a propylene tower 208, the hydrocarbons 36 with four or more carbon atoms are cut into hydrocarbons 11 with four 12 carbon atoms and five or more carbon atoms by a decarbonizing fourth tower 204, the carbon four 12 carbon atoms are cut into high-purity butylene 16 and butane 17 by a butylene tower 207, the hydrocarbons 11 with five carbon atoms and more carbon atoms are cut into hydrocarbons 32 with five carbon atoms and six carbon atoms 31 by a decarbonizing sixth tower 211, and the hydrocarbons 32 with five and six carbon atoms including part of carbon atoms 29 and the rest hydrocarbons 30.

Wherein the obtained mixed hydrocarbon 33 formed by part of the five-carbon six-hydrocarbon 29, part of the butane 19, part of the propane 22 and part of the ethane 35 is returned to the main reactor 102, the rest of the five-carbon six-hydrocarbon 30, the rest of the butane 18, the rest of the propane 21, the rest of the ethane 34 and all of the methane 25 and the high-carbon hydrocarbon 31 are taken out of the system as byproducts, wherein the part of the ethane 35 accounts for 10 percent of the ethane 28, the part of the propane 22 accounts for 25 percent of the propane 20, the part of the butane 19 accounts for 35 percent of the butane 17, the part of the five-carbon six-hydrocarbon 29 accounts for 85 percent of the five-carbon six-hydrocarbon 32, and the high-purity ethylene 27, the high-purity propylene 23 and the high-purity butene 16 are taken out of the system as products.

Comparative example 1

The existing technology of preparing propylene (MTP) from methanol is adopted, the main product is propylene, the main reactor is a multi-section series axial fixed bed reactor, and the four separation sequences of front decarburization are adopted in the separation unit.

The effects of the examples and comparative examples are shown in the following table:

	example 1	Example 2	Example 3	Comparative example
					Total olefin yield	72％	85％	88％	60％
Wherein: ethylene yield	7％	10％	11％	0
					Propylene yield	56％	62％	63％	60％
Butene yield
		9％	13％	14％	0
Recycle hydrocarbon to main reactor feed ratio						36％	28％	22％	50％
	Reduction of specific energy consumption	21％	35％	46％	0

The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.

Claims

1. A system for the co-production of ethylene, propylene and butylene by catalytic dehydration of methanol, comprising a reaction unit (100) and a separation unit (200), characterized in that said reaction unit (100) comprises a pre-reactor (101), a process steam tower (103) and a main reactor (102),

the separation unit (200) comprises a chiller (201) and a plurality of separation columns,

the pre-reactor (101) is used for partial dehydration reaction of methanol, the process steam tower (103) is used for heating and vaporizing water from the quencher (201) into steam (3),

the main reactor (102) is used for contacting and reacting the reaction products of the pre-reactor (101) and part of ethane, part of propane, part of butane and part of five-carbon and six-carbon hydrocarbons and steam from the separation unit (200) with a catalyst;

the quencher (201) is used for receiving the heat-exchanged products of the main reactor (102), further reducing the temperature and dehydrating the products;

the separation tower is used for separating the compressed hydrocarbon mixture and comprises an ethylene tower (210), a propylene tower (208), a butylene tower (207), a four decarburization towers (204), a three decarburization towers (205), a two decarburization towers (206), a demethanizer (209) and a six decarburization towers (211),

an ethylene tower (210), a propylene tower (208) and a butylene tower (207) in the separation tower are respectively used for obtaining high-purity ethylene, propylene and butylene products,

part of ethane, part of propane, part of butane and part of carbon five and carbon six hydrocarbons obtained by the separation unit (200) are returned to the main reactor (102), and other materials are extracted as byproducts.

2. The system for the co-production of ethylene, propylene and butylene by the catalytic dehydration of methanol according to claim 1, characterized in that said pre-reactor (101) is a fixed bed reactor.

3. The system for the co-production of ethylene, propylene and butylene through the catalytic dehydration of methanol according to claim 1, characterized in that said main reactor (102) is selected from one of single-stage or multi-stage axial fixed bed, radial fixed bed, fluidized bed or moving bed.

4. The system for co-production of ethylene, propylene and butylene through catalytic dehydration of methanol according to claim 1, characterized in that the separation unit (200) further comprises a compressor for compressing the hydrocarbon mixture obtained from the chiller (201) and then feeding the compressed hydrocarbon mixture into the separation column.

5. A system for co-production of ethylene, propylene and butylene through catalytic dehydration of methanol according to claim 1, characterized in that a heat exchanger is further arranged between the reaction unit (100) and the separation unit (200) for exchanging heat between the product of the main reactor (102) entering the chiller (201).

6. A process for the co-production of ethylene, propylene and butenes by catalytic dehydration of methanol, carried out on the basis of the system of claim 1, comprising the following steps:

(1) a pre-reaction stage: the methanol enters a pre-reactor (101) to carry out partial dehydration reaction to obtain a mixture of the methanol, the dimethyl ether and the water;

(2) a main reaction stage: a mixture formed by a mixture of methanol, dimethyl ether and water from the pre-reaction stage and steam from a process steam tower (103) enters a main reactor (102) to contact with a catalyst and react to obtain a mixture containing ethylene, propylene and butylene;

(4) a compression and rectification stage: after a hydrocarbon mixture from an oil-water separation stage is compressed by a compressor, the compressed hydrocarbon mixture is cut by a four decarburization tower (204), a three decarburization tower (205), a two decarburization tower (206), a butene tower (207), a propylene tower (208), a demethanizer (209), an ethylene tower (210) and a six decarburization tower (211), the obtained high-purity ethylene, high-purity propylene and high-purity butene are discharged from a system as products, the obtained mixed hydrocarbons formed by part of the five carbon and six carbon hydrocarbons, part of butane, part of propane and part of ethane return to a main reactor, and the rest of the five carbon and six carbon hydrocarbons, butane, propane, ethane and all of methane and high carbon hydrocarbons are extracted from the system as byproducts.

7. The method for co-producing ethylene, propylene and butylene through catalytic dehydration of methanol according to claim 6, characterized in that the outlet temperature of the pre-reactor (101) is 150-450 ℃, the operating pressure is 0.1-0.5 MPa, the outlet temperature of the main reactor (102) is 450-550 ℃, and the operating pressure is 0.1-0.5 MPa.

8. The method for the co-production of ethylene, propylene and butylene through the catalytic dehydration of methanol according to claim 6, characterized in that the outlet temperature of the process steam tower (103) is 100-300 ℃.

9. The method for co-producing ethylene, propylene and butylene through catalytic dehydration of methanol according to claim 6, characterized in that the mixture of methanol, dimethyl ether and water is passed through at least one heat exchanger to recover heat before entering a quench cooler (201), and the temperature of the hydrocarbon mixture obtained at the outlet of the quench cooler (201) is 30-90 ℃.

10. The method for coproducing ethylene, propylene and butylene through catalytic dehydration of methanol according to claim 6, wherein the sequence of hydrocarbon mixture cutting separation performed by the separation tower comprises a front debutanization separation sequence, a front depropanization separation sequence or a front deethanization separation sequence.