Device and method for preparing isobutene and methanol by cracking methyl tert-butyl ether

Abstract

The invention relates to a device and a method for preparing isobutene and methanol by cracking methyl tert-butyl ether. The device comprises a methyl tert-butyl ether vaporization refining tower, a reactor, a cooling tower, an absorption tower, a methanol extraction tower, an isobutene light component removal tower and an isobutene heavy component removal tower which are sequentially connected along a material conveying direction, a top discharge hole of the cooling tower is connected with a lower gas-phase material inlet of the absorption tower; an absorbent outlet at the bottom of the absorption tower is circularly connected with a cooling absorption liquid inlet at the top of the cooling tower; the bottom extract liquor outlet of the methanol extraction tower is circularly connected with the top absorbent inlet of the absorption tower; an isobutylene discharge hole is formed in the top of the isobutylene heavy component removal tower; the device further comprises a methanol recovery tower and a methanol refining tower which are connected in sequence along the material conveying direction; a bottom cooling absorption liquid outlet of the cooling tower is connected with the methanol recovery tower; a methanol discharge hole is formed in the bottom of the methanol refining tower. The device provided by the invention not only can relax the limitation of the purity of methyl tert-butyl ether in raw materials, but also can prepare high-purity isobutene and high-purity methanol at the same time.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of rectification, in particular to a device and method for preparing isobutylene and methanol by cracking methyl tert-butyl ether. BACKGROUND

[0002] Isobutylene is an important organic chemical raw material, and high-purity isobutylene is widely used to produce butyl rubber or polyisobutylene products. Since the boiling points of different C4 fractions are similar, it is difficult to purify isobutylene by rectification. High-purity isobutylene is mainly obtained by cracking methyl tert-butyl ether (MTBE). However, the existing MTBE cracking technology has the following defects: 1) strict requirement on the purity of raw materials (MTBE > 98.5%); 2) difficulty in simultaneously obtaining high-purity isobutylene and methanol; and 3) high energy consumption. Among the impurities in the MTBE raw material, the most influential on the product indicators of isobutylene and methanol is methyl sec-butyl ether (MSBE), because MSBE can be cracked into 1-butene and methanol, and 1-butene has a boiling point similar to that of isobutylene, which is difficult to remove. Therefore, in order to obtain high-quality polymer-grade isobutylene, the existing technology generally requires that the content of MSBE in the MTBE raw material be less than 0.12wt% or even lower. Moreover, in order to obtain high-purity isobutylene, the purity of methanol is generally sacrificed to ensure the product quality of isobutylene.

[0003] CN117820066A discloses a production method and system of high-purity isobutylene for rubber, which comprises the following steps: 1) cracking refined methyl tert-butyl ether to obtain a cracking product, and then cooling and performing gas-liquid separation to obtain gas-phase carbon four and liquid-phase methanol solution; 2) compressing the gas-phase carbon four obtained in the above step, and then feeding it into a heavy-removal tower as gas-phase feed, and feeding the liquid-phase methanol solution into the heavy-removal tower as liquid-phase feed, and then obtaining an azeotrope of isobutylene and methanol after heavy-removal separation; 3) extracting the azeotrope of isobutylene and methanol obtained in the above step by an extraction tower to obtain crude isobutylene; and 4) removing light components from the crude isobutylene obtained in the above step by a light-removal tower, and then obtaining high-purity isobutylene through side-line discharge. Although the patent obtains polymer-grade high-purity isobutylene, it requires that the purity of the raw material MTBE be greater than 99%, and high-purity methanol is not obtained at the same time.

[0004] In summary, in view of the defects of the existing MTBE cracking technology, it is necessary to provide a device and method for preparing isobutylene and methanol by cracking MTBE, so as to reduce the requirement on the purity of MTBE, and simultaneously obtain high-purity isobutylene and high-purity methanol. SUMMARY

[0005] To solve the above technical problems, the application provides a device and a method for preparing isobutene and methanol by cracking methyl tert-butyl ether, which first uses a methyl tert-butyl ether vaporization refining tower to treat methyl tert-butyl ether, so as to relax the restriction on the purity of methyl tert-butyl ether in the raw material containing methyl tert-butyl ether, and sequentially connects the methyl tert-butyl ether vaporization refining tower, a reactor, a cooling tower, an absorption tower, a methanol extraction tower, an isobutene light-removing tower and an isobutene heavy-removing tower, so as to obtain isobutene with a purity greater than 99.9%, and sequentially connects the cooling tower, a methanol recovery tower and a methanol refining tower, so as to obtain methanol with a purity greater than 99.9%.

[0006] To achieve the above purpose, the application adopts the following technical solutions:

[0007] In a first aspect, the application provides a device for preparing isobutene and methanol by cracking methyl tert-butyl ether, which comprises, in the direction of material conveying, a methyl tert-butyl ether vaporization refining tower, a reactor, a cooling tower, an absorption tower, a methanol extraction tower, an isobutene light-removing tower and an isobutene heavy-removing tower connected in sequence.

[0008] The cooling tower comprises a top cooling absorption liquid inlet, a top discharge outlet and a bottom cooling absorption liquid outlet.

[0009] The absorption tower comprises a top absorption agent inlet, a bottom absorption agent outlet and a lower gas phase material inlet.

[0010] The top discharge outlet of the cooling tower is connected with the lower gas phase material inlet of the absorption tower, and the bottom absorption agent outlet of the absorption tower is connected with the top cooling absorption liquid inlet of the cooling tower in circulation.

[0011] The methanol extraction tower comprises a bottom extraction liquid discharge outlet, and the bottom extraction liquid discharge outlet of the methanol extraction tower is connected with the top absorption agent inlet of the absorption tower in circulation.

[0012] The isobutene heavy-removing tower is provided with an isobutene discharge outlet at the top.

[0013] The device further comprises, in the direction of material conveying, a methanol recovery tower and a methanol refining tower connected in sequence, the bottom cooling absorption liquid outlet of the cooling tower is connected with the methanol recovery tower, and the methanol refining tower is provided with a methanol discharge outlet at the bottom.

[0014] The methyl tert-butyl ether vaporization refining tower is used firstly in the application to refine the raw material, so as to relax the restriction on the purity of methyl tert-butyl ether in the raw material containing methyl tert-butyl ether, and relax the requirement that the purity of methyl tert-butyl ether in the raw material in the prior art is greater than 98.5% to a purity of greater than or equal to 98%, and meanwhile, the difficulty of separation of isobutene and methanol is reduced, and the energy consumption of separation is reduced, the device provided by the application can simultaneously prepare isobutene with a purity of greater than 99.9% and methanol with a purity of greater than 99.9%, and further, the absorbent is recycled in the application, so that the water consumption and energy consumption in the reaction process are reduced, and the total water consumption is only 0.065 times that of the raw material.

[0015] As a preferred technical scheme of the application, the methyl tert-butyl ether vaporization refining tower comprises a first tower section and a second tower section from bottom to top.

[0016] Preferably, the total number of trays of the methyl tert-butyl ether vaporization refining tower is 45-50, for example, can be 45, 46, 47, 48, 49 or 50, but is not limited to the listed values, and other values not listed in the above value range are also applicable.

[0017] Preferably, the number of trays of the first tower section is 40-45, for example, can be 40, 41, 42, 43, 44 or 45, but is not limited to the listed values, and other values not listed in the above value range are also applicable.

[0018] Preferably, the number of trays of the second tower section is 4-6, for example, can be 4, 5 or 6, but is not limited to the listed values, and other values not listed in the above value range are also applicable.

[0019] Preferably, the methyl tert-butyl ether vaporization refining tower is a variable-diameter tower.

[0020] Preferably, the diameter of the second tower section is smaller than the diameter of the first tower section.

[0021] The variable-diameter tower is used to refine methyl tert-butyl ether in the application, wherein the diameter of the second tower section is smaller than the diameter of the first tower section, after the gaseous phase of refined methyl tert-butyl ether is extracted from the side line, the flow rate of the ascending gaseous phase is reduced, in order to match the lower gas-liquid load of the second tower section, a smaller tower diameter is used to avoid liquid leakage, uneven distribution or efficiency reduction due to too low flow rate in the low load section, so as to improve the operation flexibility and stability of the methyl tert-butyl ether vaporization refining tower; at the same time, the amount of light components in the raw material is very small, so the effect of the small tower diameter of the second tower section is better.

[0022] Preferably, the ratio of the column diameter of the second column section to the column diameter of the first column section is (0.6-0.8):1, for example, it can be 0.6:1, 0.65:1, 0.7:1, 0.75:1 or 0.8:1, but is not limited to the listed values, and other values not listed in the above range are also applicable.

[0023] By limiting the ratio of the column diameter of the second column section to the column diameter of the first column section of the methyl tert-butyl ether vaporization refining column to (0.6-0.8):1, not only can the purity of refined methyl tert-butyl ether be increased, but also liquid flooding or entrainment of mist can be avoided under high load. If the ratio of the column diameter of the second column section to the column diameter of the first column section is less than 0.6:1, the rising gas phase of the second column section will entrain the liquid phase, resulting in a decrease in the purity of refined methyl tert-butyl ether taken from the side line, and in severe cases, even liquid flooding will occur. If the ratio of the column diameter of the second column section to the column diameter of the first column section is greater than 0.8:1, the gas velocity of the second column section will be too low, causing the tray to leak liquid, and even causing the second column section to be unable to operate normally.

[0024] Preferably, the methyl tert-butyl ether vaporization refining column comprises a methyl tert-butyl ether feed port and a side line outlet, and the side line outlet is connected to the reactor.

[0025] Preferably, the methyl tert-butyl ether feed port and the side line outlet are both located in the first column section.

[0026] Preferably, the methyl tert-butyl ether feed port is located below the side line outlet.

[0027] Preferably, the methyl tert-butyl ether vaporization refining column further comprises a vaporization refining top outlet and a vaporization refining bottom outlet.

[0028] As a preferred technical solution of the present application, the device further comprises a compressor arranged between the absorption tower and the methanol extraction tower.

[0029] Preferably, the methanol extraction tower further comprises a top extraction liquid inlet, a middle extraction liquid inlet and a lower liquid phase material inlet.

[0030] Preferably, the lower liquid phase material inlet of the methanol extraction tower is connected to the compressor.

[0031] Preferably, the methanol recovery tower comprises a bottom heavy component outlet.

[0032] Preferably, the bottom heavy component outlet of the methanol recovery tower is connected to the middle extraction liquid inlet of the methanol extraction tower in a circulation manner.

[0033] Preferably, the number of trays of the cooling tower is in the range of 15 to 20, for example, it can be 15, 16, 17, 18, 19 or 20, but is not limited to the listed values, and other values not listed within the above range are also applicable.

[0034] Preferably, the number of trays of the methanol recovery column is in the range of 45 to 50, for example, it can be 45, 46, 47, 48, 49 or 50, but is not limited to the listed values, and other values not listed within the above range are also applicable.

[0035] Preferably, the number of trays of the methanol recovery column is in the range of 45 to 50, for example, it can be 45, 46, 47, 48, 49 or 50, but is not limited to the listed values, and other values not listed within the above range are also applicable.

[0036] Preferably, the number of trays of the absorption column is in the range of 18 to 25, for example, it can be 18, 19, 20, 21, 22, 23, 24 or 25, but is not limited to the listed values, and other values not listed within the above range are also applicable.

[0037] Preferably, the number of trays of the methanol extraction column is in the range of 28 to 32, for example, it can be 28, 29, 30, 31 or 32, but is not limited to the listed values, and other values not listed within the above range are also applicable.

[0038] Preferably, the number of trays of the isobutylene light ends removal column is in the range of 44 to 48, for example, it can be 44, 45, 46, 47 or 48, but is not limited to the listed values, and other values not listed within the above range are also applicable.

[0039] Preferably, the number of trays of the isobutylene heavy ends removal column is in the range of 40 to 43, for example, it can be 40, 41, 42 or 43, but is not limited to the listed values, and other values not listed within the above range are also applicable.

[0040] Preferably, the reactor comprises a fixed bed reactor.

[0041] Preferably, the cooling tower and the absorption column are both packed columns.

[0042] Preferably, the methanol extraction column, the methanol recovery column, the methanol purification column, the isobutylene light ends removal column and the isobutylene heavy ends removal column are all plate columns.

[0043] The method for preparing isobutene and methanol by cracking methyl tert-butyl ether provided in the first aspect of the present application is not particularly limited, as long as isobutene and methanol described in the first aspect can be obtained; further, the method for preparing isobutene and methanol by cracking methyl tert-butyl ether provided in the second aspect of the present application is preferably used, which can relax the limitation on the purity of methyl tert-butyl ether in the raw material containing methyl tert-butyl ether while ensuring the purity of isobutene and methanol.

[0044] In the second aspect, the present application provides a method for preparing isobutene and methanol by cracking methyl tert-butyl ether, which comprises the following steps:

[0045] (1) a raw material containing methyl tert-butyl ether is sent into a methyl tert-butyl ether vaporization refining tower for refining treatment to obtain refined methyl tert-butyl ether;

[0046] (2) the refined methyl tert-butyl ether in step (1) is sent into a reactor for cracking reaction under the action of a catalyst to obtain a mixed gas of isobutene and methanol;

[0047] (3) the mixed gas in step (2) is subjected to separation treatment to obtain isobutene and methanol;

[0048] The catalyst in step (2) comprises a carrier and active components and an auxiliary agent supported on the carrier;

[0049] The carrier comprises silicon dioxide and aluminum oxide;

[0050] The active components comprise phosphotungstic acid and / or a combination of phosphotungstic acid and phosphomolybdic acid;

[0051] The auxiliary agent comprises any one or a combination of at least two of V, Ce or Cs, wherein a typical but non-limiting combination comprises a combination of V and Ce, a combination of V and Cs, a combination of Ce and Cs, a combination of V, Ce and Cs.

[0052] In the present application, the raw material is first refined by using a methyl tert-butyl ether vaporization refining tower to relax the limitation on the purity of methyl tert-butyl ether in the raw material containing methyl tert-butyl ether, and the requirement that the purity of methyl tert-butyl ether in the raw material in the prior art is greater than 98.5% is relaxed to a purity of ≥98%, at the same time, the difficulty of separation of isobutene and methanol is reduced, and the energy consumption of separation is reduced, further, the catalyst is used in the process of cracking refined methyl tert-butyl ether to obtain a mixed gas of isobutene and methanol, and by limiting the materials of the carrier, active components and auxiliary agent in the catalyst, the catalyst has good selectivity in the reaction process, and the conversion rate of methyl tert-butyl ether is high.

[0053] As a preferred technical scheme of the present application, the mass ratio of the active component to the carrier is 1:(3-4), for example, it can be 1:3, 1:3.2, 1:3.5, 1:3.6, 1:3.8 or 1:4, but is not limited to the listed values, and other values not listed in the above range are also applicable.

[0054] By limiting the mass ratio of the active component to the carrier in the catalyst to 1:(3-4), the catalyst has a high specific surface area and strength, and sufficient active component loading on the catalyst is ensured. The high specific surface area enables efficient mass transfer of the active component of the catalyst with the gas-phase reactants during the reaction, thereby improving the catalytic efficiency of the catalyst. Meanwhile, the high strength of the carrier also enables long-term operation of the catalyst, avoiding breakage and pulverization. If the mass ratio of the two is less than 1:4, the catalyst will have insufficient active sites, and the conversion rate of methyl tert-butyl ether will decrease. If the mass ratio of the two is greater than 1:3, excessive WO3 will be produced during the reaction cracking process, which will cause the catalyst pores to be blocked and reduce the service life of the catalyst.

[0055] Preferably, the mass ratio of the silicon dioxide to the aluminum oxide is (5-6):1, for example, it can be 5:1, 5.2:1, 5.4:1, 5.6:1, 5.8:1 or 6:1, but is not limited to the listed values, and other values not listed in the above range are also applicable.

[0056] By limiting the mass ratio of the silicon dioxide to the aluminum oxide in the catalyst carrier to (5-6):1, the catalyst has high strength, thereby prolonging the service life of the catalyst.

[0057] Preferably, the mass ratio of the phosphomolybdic acid to the phosphotungstic acid is (0-1):8, for example, it can be 0:8, 1:32, 1:16, 1:10 or 1:8, but is not limited to the listed values, and other values not listed in the above range are also applicable.

[0058] By limiting the mass ratio of the phosphomolybdic acid to the phosphotungstic acid in the active component of the catalyst to (0-1):8, the catalyst not only has good catalytic activity, but also has a long service life. If the mass of the phosphotungstic acid is too small, the activity of the catalyst will decrease, and the conversion rate of methyl tert-butyl ether will eventually decrease.

[0059] Preferably, the content of V in the catalyst, calculated based on V2O5, accounts for (0.02-0.05):1 of the total mass of the catalyst, for example, it can be 0.02:1, 0.03:1, 0.04:1 or 0.05:1, but is not limited to the listed values, and other values not listed in the above range are also applicable.

[0060] The application can improve the selectivity of the catalyst to isobutene and methanol, and can make the service life of the catalyst reach more than 3 years by limiting the ratio of the content of V (calculated as V2O5) in the catalyst to the total mass of the catalyst to (0.02-0.05):1.

[0061] Preferably, the ratio of the content of Ce in the catalyst to the total mass of the catalyst, calculated as CeO2, is (0.05-0.08):1, for example, it can be 0.05:1, 0.06:1, 0.07:1 or 0.08:1, but is not limited to the listed values, and other values not listed in the above numerical range are also applicable.

[0062] The application can avoid high-temperature sintering deactivation of the catalyst by limiting the ratio of the content of Ce in the catalyst to the total mass of the catalyst to (0.05-0.08):1, so that the service life of the catalyst reaches more than 3 years; if the content of Ce is too low, the high-temperature performance of the catalyst will be reduced, and when the reaction temperature exceeds 260℃, the catalyst is prone to sintering deactivation, thereby reducing the service life of the catalyst; if the content of Ce is too high, it will lead to the occurrence of oxidation side reactions, ultimately reducing the reaction selectivity.

[0063] Preferably, the ratio of the content of Cs in the catalyst to the total mass of the catalyst is (0.16-0.19):1, for example, it can be 0.16:1, 0.17:1, 0.18:1 or 0.19:1, but is not limited to the listed values, and other values not listed in the above numerical range are also applicable.

[0064] The application can not only ensure the yield of isobutene and methanol, but also make the service life of the catalyst reach more than 3 years by limiting the ratio of the content of Cs in the catalyst to the total mass of the catalyst to (0.16-0.19):1; if the content of Cs is too low, it will lead to an increase in the occurrence rate of side reactions to generate dimeric isobutene, not only reducing the yield of isobutene and methanol, but also easily polluting the catalyst and reducing the service life of the catalyst; if the content of Cs is too high, it is easy to produce oxidation byproducts, which will also reduce the yield of isobutene and methanol.

[0065] As a preferred technical solution of the application, the methyl tert-butyl ether vaporization refining tower comprises a first tower section and a second tower section from bottom to top.

[0066] Preferably, the methyl tert-butyl ether vaporization refining tower is a variable-diameter tower.

[0067] Preferably, the column diameter of the second column section is smaller than the column diameter of the first column section.

[0068] Preferably, the ratio of the column diameter of the second column section to the column diameter of the first column section is (0.6-0.8): 1, for example, it can be 0.6: 1, 0.65: 1, 0.7: 1, 0.75: 1 or 0.8: 1, but is not limited to the listed values, other values not listed in the above value range are also applicable.

[0069] Preferably, the feedstock enters the MTBE vaporization refining column from the 24th to 26th theoretical plate of the first column section, for example, it can be the 24th theoretical plate, the 25th theoretical plate or the 26th theoretical plate, but is not limited to the listed values, other values not listed in the above value range are also applicable.

[0070] Preferably, the refined MTBE is withdrawn from the 15th to 17th plate of the first column section, for example, it can be the 15th plate, the 16th plate or the 17th plate, but is not limited to the listed values, other values not listed in the above value range are also applicable.

[0071] Preferably, the feed temperature of the feedstock is 95-100°C, for example, it can be 95°C, 96°C, 97°C, 98°C, 99°C or 100°C, but is not limited to the listed values, other values not listed in the above value range are also applicable.

[0072] Preferably, the overhead pressure of the MTBE vaporization refining column is 0.3-0.35 MPa, for example, it can be 0.3 MPa, 0.31 MPa, 0.32 MPa, 0.33 MPa, 0.34 MPa or 0.35 MPa, but is not limited to the listed values, other values not listed in the above value range are also applicable.

[0073] Preferably, the overhead temperature of the MTBE vaporization refining column is 69-80°C, for example, it can be 69°C, 70°C, 72°C, 74°C, 76°C, 78°C or 80°C, but is not limited to the listed values, other values not listed in the above value range are also applicable.

[0074] Preferably, the overhead liquid of the MTBE vaporization refining column is fully refluxed.

[0075] Preferably, the temperature of the refined MTBE is 105-110°C, for example, it can be 105°C, 106°C, 107°C, 108°C, 109°C or 110°C, but is not limited to the listed values, other values not listed in the above value range are also applicable.

[0076] Preferably, the methyl tert-butyl ether vaporization refining column has a column bottom temperature of 118-125°C, for example, it can be 118°C, 120°C, 122°C, 124°C or 125°C, but is not limited to the listed values, and other values not listed within the above range are also applicable.

[0077] Preferably, the reactor has a temperature of 180-280°C, for example, it can be 180°C, 200°C, 220°C, 240°C, 260°C or 280°C, but is not limited to the listed values, and other values not listed within the above range are also applicable.

[0078] Preferably, the reactor has a pressure of 0.1-0.2 MPa, for example, it can be 0.1 MPa, 0.12 MPa, 0.14 MPa, 0.16 MPa, 0.18 MPa or 0.2 MPa, but is not limited to the listed values, and other values not listed within the above range are also applicable.

[0079] Preferably, the reactor has a space velocity of 0.3-1.0 h -1 , for example, it can be 0.3 h -1 , 0.5 h -1 , 0.7 h -1 , 0.9 h -1 or 1.0 h -1 , but is not limited to the listed values, and other values not listed within the above range are also applicable.

[0080] As a preferred technical solution of the present application, the separation treatment comprises:

[0081] S3.1, the mixed gas of step (2) is cooled and treated by a cooling tower to obtain an isobutene-containing gas phase and a methanol-containing liquid phase;

[0082] S3.2, the methanol-containing liquid phase is subjected to first rectification treatment by a methanol recovery column to obtain crude methanol and an aqueous phase, wherein a first part of the aqueous phase is returned to the methanol extraction column to be used as an extractant, a second part of the aqueous phase is discharged, and the crude methanol is subjected to second rectification treatment by a methanol refining column to obtain methanol;

[0083] S3.3, the isobutene-containing gas phase enters an absorption tower to be subjected to absorption treatment to obtain a demethanized isobutene gas phase and an absorption-rich liquid, the absorption-rich liquid is returned to the cooling tower to be used as a cooling absorption liquid, the demethanized isobutene gas phase enters a compressor to be subjected to compression treatment to obtain an isobutene-containing liquid phase, the isobutene-containing liquid phase enters a methanol extraction tower to be subjected to extraction treatment to obtain crude isobutene and a treated extractant, the crude isobutene is subjected to first purification treatment and second purification treatment by an isobutene light-removing tower and an isobutene heavy-removing tower in sequence to obtain isobutene, and the treated extractant is returned to the absorption tower to be used as an absorbent.

[0084] The application adopts a sequence type different concentration gradient absorption liquid absorption separation process, reduces the wastewater production, and improves the isobutene purity and yield, and the total water consumption is only 0.065 times of the raw material.

[0085] As a preferred technical scheme of the application, the extractant used in the extraction process comprises desalted water and the first part of the aqueous phase.

[0086] Preferably, the volume ratio of the first part of the aqueous phase to the desalted water is (9-10):1, for example, it can be 9:1, 9.2:1, 9.4:1, 9.6:1, 9.8:1 or 10:1, but is not limited to the listed values, and other values not listed in the above value range are also applicable.

[0087] Preferably, the volume ratio of the first part of the aqueous phase to the second part of the aqueous phase is (7.7-8.5):1, for example, it can be 7.7:1, 7.8:1, 7.9:1, 8:1, 8.1:1, 8.2:1, 8.3:1, 8.4:1 or 8.5:1, but is not limited to the listed values, and other values not listed in the above value range are also applicable.

[0088] Preferably, the mass percentage of methanol in the first part of the aqueous phase used as the extractant for recycling is 0.12-0.16%, for example, it can be 0.12%, 0.13%, 0.14%, 0.15% or 0.16%, but is not limited to the listed values, and other values not listed in the above value range are also applicable.

[0089] Preferably, the mass percentage of methanol in the treated extractant used as the absorbent for recycling is 1.6-1.8%, for example, it can be 1.6%, 1.65%, 1.7%, 1.75% or 1.8%, but is not limited to the listed values, and other values not listed in the above value range are also applicable.

[0090] Preferably, the mass percentage of methanol in the absorption rich liquid used as the cooling absorbent for recycling is 16-18%, for example, it can be 16%, 16.5%, 17%, 17.5% or 18%, but is not limited to the listed values, and other values not listed in the above value range are also applicable.

[0091] Preferably, the mass percentage of methanol in the methanol-containing liquid phase obtained after the cooling treatment is 40-42%, for example, it can be 40%, 40.5%, 41%, 41.5% or 42%, but is not limited to the listed values, and other values not listed in the above value range are also applicable.

[0092] As a preferred technical solution of the present application, the top pressure of the cooling tower is 0.04-0.06 MPa, for example, it can be 0.04 MPa, 0.045 MPa, 0.05 MPa, 0.055 MPa or 0.06 MPa, but not limited to the listed values, other values not listed in the above range are also applicable.

[0093] Preferably, the top temperature of the cooling tower is 54-56℃, for example, it can be 54℃, 54.5℃, 55℃, 55.5℃ or 56℃, but not limited to the listed values, other values not listed in the above range are also applicable.

[0094] Preferably, the liquid-gas ratio of the cooling tower is 8-12 L / m 3 , for example, it can be 8 L / m 3 , 9 L / m 3 , 10 L / m 3 , 11 L / m 3 or 12 L / m 3 , but not limited to the listed values, other values not listed in the above range are also applicable.

[0095] Preferably, the top pressure of the methanol recovery tower is 0.03-0.04 MPa, for example, it can be 0.03 MPa, 0.032 MPa, 0.034 MPa, 0.036 MPa, 0.038 MPa or 0.04 MPa, but not limited to the listed values, other values not listed in the above range are also applicable.

[0096] Preferably, the top temperature of the methanol recovery tower is 70-75℃, for example, it can be 70℃, 71℃, 72℃, 73℃, 74℃ or 75℃, but not limited to the listed values, other values not listed in the above range are also applicable.

[0097] Preferably, the bottom pressure of the methanol recovery tower is 0.05-0.07 MPa, for example, it can be 0.05 MPa, 0.055 MPa, 0.06 MPa, 0.065 MPa or 0.07 MPa, but not limited to the listed values, other values not listed in the above range are also applicable.

[0098] Preferably, the bottom temperature of the methanol recovery tower is 110-115℃, for example, it can be 110℃, 111℃, 112℃, 113℃, 114℃ or 115℃, but not limited to the listed values, other values not listed in the above range are also applicable.

[0099] Preferably, the reflux ratio of the methanol recovery column is 1.5-2.0, for example, it can be 1.5, 1.6, 1.7, 1.8, 1.9 or 2.0, but is not limited to the listed values, and other values not listed in the above range are also applicable.

[0100] Preferably, the top pressure of the methanol refining column is 0.34-0.36 MPa, for example, it can be 0.34 MPa, 0.345 MPa, 0.35 MPa, 0.355 MPa or 0.36 MPa, but is not limited to the listed values, and other values not listed in the above range are also applicable.

[0101] Preferably, the top temperature of the methanol refining column is 71-73°C, for example, it can be 71°C, 71.5°C, 72°C, 72.5°C or 73°C, but is not limited to the listed values, and other values not listed in the above range are also applicable.

[0102] Preferably, the bottom pressure of the methanol refining column is 0.38-0.4 MPa, for example, it can be 0.38 MPa, 0.385 MPa, 0.39 MPa, 0.395 MPa or 0.4 MPa, but is not limited to the listed values, and other values not listed in the above range are also applicable.

[0103] Preferably, the bottom temperature of the methanol refining column is 92-95°C, for example, it can be 92°C, 93°C, 94°C or 95°C, but is not limited to the listed values, and other values not listed in the above range are also applicable.

[0104] Preferably, the reflux ratio of the methanol refining column is 3-5, for example, it can be 3, 3.5, 4, 4.5 or 5, but is not limited to the listed values, and other values not listed in the above range are also applicable.

[0105] Preferably, the top pressure of the absorption column is 0.02-0.03 MPa, for example, it can be 0.02 MPa, 0.022 MPa, 0.024 MPa, 0.026 MPa, 0.028 MPa or 0.03 MPa, but is not limited to the listed values, and other values not listed in the above range are also applicable.

[0106] Preferably, the top temperature of the absorption column is 38-40°C, for example, it can be 38°C, 38.5°C, 39°C, 39.5°C or 40°C, but is not limited to the listed values, and other values not listed in the above range are also applicable.

[0107] Preferably, the liquid-gas ratio of the absorption column is 6-8 L / m 3 , for example, it can be 6 L / m3 , 6.5 L / m 3 , 7 L / m 3 , 7.5 L / m 3 or 8 L / m 3 but not only the listed values, other values within the range are also applicable.

[0108] Preferably, the pressure at the top of the methanol extraction column is 0.45-0.48 MPa, for example it can be 0.45 MPa, 0.46 MPa, 0.47 MPa or 0.48 MPa, but not only the listed values, other values within the range are also applicable.

[0109] Preferably, the temperature at the top of the methanol extraction column is 38-40 °C, for example it can be 38 °C, 38.5 °C, 39 °C, 39.5 °C or 40 °C, but not only the listed values, other values within the range are also applicable.

[0110] Preferably, the pressure at the bottom of the methanol extraction column is 0.76-0.8 MPa, for example it can be 0.76 MPa, 0.77 MPa, 0.78 MPa, 0.79 MPa or 0.8 MPa, but not only the listed values, other values within the range are also applicable.

[0111] Preferably, the temperature at the bottom of the methanol extraction column is 39-41 °C, for example it can be 39 °C, 39.5 °C, 40 °C, 40.5 °C or 41 °C, but not only the listed values, other values within the range are also applicable.

[0112] Preferably, the mass ratio of the extractant used in the extraction process to the isobutene-containing liquid phase is (0.8-0.85): 1, for example it can be 0.8:1, 0.81:1, 0.82:1, 0.83:1, 0.84:1 or 0.85:1, but not only the listed values, other values within the range are also applicable.

[0113] Preferably, the pressure at the top of the isobutene light-ends removal column is 0.75-0.78 MPa, for example it can be 0.75 MPa, 0.76 MPa, 0.77 MPa or 0.78 MPa, but not only the listed values, other values within the range are also applicable.

[0114] Preferably, the temperature at the top of the isobutene light-ends removal column is 50-52 °C, for example it can be 50 °C, 50.5 °C, 51 °C, 51.5 °C or 52 °C, but not only the listed values, other values within the range are also applicable.

[0115] Preferably, the column bottom pressure of the isobutene light-removing column is 0.79-0.8 MPa, for example, can be 0.79 MPa, 0.792 MPa, 0.794 MPa, 0.796 MPa, 0.798 MPa or 0.8 MPa, but not only limited to the listed values, other values not listed in the above range are also applicable.

[0116] Preferably, the column bottom temperature of the isobutene light-removing column is 66-68℃, for example, can be 66℃, 66.5℃, 67℃, 67.5℃ or 68℃, but not only limited to the listed values, other values not listed in the above range are also applicable.

[0117] Preferably, the overhead liquid phase of the isobutene light-removing column is total reflux.

[0118] Preferably, the column top pressure of the isobutene heavy-removing column is 0.59-0.61 MPa, for example, can be 0.59 MPa, 0.595 MPa, 0.6 MPa, 0.605 MPa or 0.61 MPa, but not only limited to the listed values, other values not listed in the above range are also applicable.

[0119] Preferably, the column top temperature of the isobutene heavy-removing column is 55-56.5℃, for example, can be 55℃, 55.5℃, 56℃ or 56.5℃, but not only limited to the listed values, other values not listed in the above range are also applicable.

[0120] Preferably, the column bottom pressure of the isobutene heavy-removing column is 0.62-0.64 MPa, for example, can be 0.62 MPa, 0.625 MPa, 0.63 MPa, 0.635 MPa or 0.64 MPa, but not only limited to the listed values, other values not listed in the above range are also applicable.

[0121] Preferably, the column bottom temperature of the isobutene heavy-removing column is 90-93℃, for example, can be 90℃, 91℃, 92℃ or 93℃, but not only limited to the listed values, other values not listed in the above range are also applicable.

[0122] Preferably, the reflux ratio of the isobutene heavy-removing column is 1.7-2.0, for example, can be 1.7, 1.8, 1.9 or 2.0, but not only limited to the listed values, other values not listed in the above range are also applicable.

[0123] As a preferred technical solution of the present application, the method comprises the following steps:

[0124] (1) the raw material containing methyl tert-butyl ether is sent into a variable-diameter methyl tert-butyl ether vaporization refining tower to perform a refining treatment, and refined methyl tert-butyl ether is obtained;

[0125] (2) the refined methyl tert-butyl ether in step (1) is sent into a reactor to perform a cracking reaction under the action of a catalyst, and a mixed gas of isobutene and methanol is obtained; wherein the catalyst comprises a carrier and an active component and an auxiliary agent supported on the carrier, the carrier comprises silica and alumina in a mass ratio of (5-6):1, the active component comprises phosphomolybdic acid and phosphotungstic acid in a mass ratio of (0-1):8, and the auxiliary agent comprises any one or a combination of at least two of V, Ce or Cs;

[0126] (3) the mixed gas in step (2) is subjected to a cooling treatment through a cooling tower, and a gas phase containing isobutene and a liquid phase containing methanol are obtained;

[0127] (4) the liquid phase containing methanol is subjected to a first rectification treatment through a methanol recovery tower, and a crude methanol and an aqueous phase are obtained, wherein a first part of the aqueous phase is returned to a methanol extraction tower for recycling, a second part of the aqueous phase is discharged, and the crude methanol is subjected to a second rectification treatment through a methanol refining tower, and methanol is obtained;

[0128] (5) the gas phase containing isobutene is subjected to an absorption treatment through an absorption tower, and a demethanolized isobutene gas phase and an absorption rich liquid are obtained, the absorption rich liquid is returned to the cooling tower to be used as a cooling absorption liquid, the demethanolized isobutene gas phase is subjected to a compression treatment through a compressor, and an isobutene-containing liquid phase is obtained, the isobutene-containing liquid phase is subjected to an extraction treatment through a methanol extraction tower, and a crude isobutene and a treated extractant are obtained, the crude isobutene is subjected to a first purification treatment and a second purification treatment through an isobutene light-removing tower and an isobutene heavy-removing tower in sequence, and isobutene is obtained, and the treated extractant is returned to the absorption tower to be used as an absorbent.

[0129] Compared with the prior art, the present application has at least the following beneficial effects:

[0130] (1) The device for preparing isobutene and methanol by cracking methyl tert-butyl ether provided by the present application can not only relax the limitation on the purity of methyl tert-butyl ether in the raw material containing methyl tert-butyl ether, so that the purity of methyl tert-butyl ether in the raw material is ≥98%, but also can prepare isobutene with a purity greater than 99.9% and methanol with a purity greater than 99.9%;

[0131] (2) The selectivity of the catalyst used in the method for preparing isobutene and methanol by cracking methyl tert-butyl ether provided by the present application in the reaction process can reach more than 99%, the conversion rate of methyl tert-butyl ether can reach more than 99%, and the service life of the catalyst can reach more than 3 years. BRIEF DESCRIPTION OF DRAWINGS

[0132] Figure 1 is a device for preparing isobutene and methanol by cracking methyl tert-butyl ether provided by the embodiment 1 of the present application.

[0133] Figure 2 is a device for preparing isobutene and methanol by cracking methyl tert-butyl ether provided by the embodiment 1 of the present application. Figure 1 is a partial schematic diagram of the methyl tert-butyl ether vaporization and refining tower in the embodiment 1 of the present application.

[0134] Figure 3 is a device for preparing isobutene and methanol by cracking methyl tert-butyl ether provided by the embodiment 1 of the present application.

[0135] wherein, 1-methyl tert-butyl ether vaporization and refining tower; 101-methyl tert-butyl ether feeding port; 102-side line outlet; 103-vaporization and refining top outlet; 104-vaporization and refining bottom outlet; 2-reactor; 3-cooling tower; 301-top cooling absorption liquid inlet; 302-bottom cooling absorption liquid outlet; 303-top outlet; 4-absorption tower; 401-top absorption agent inlet; 402-bottom absorption agent outlet; 403-lower gas phase material inlet; 5-compressor; 6-methanol extraction tower; 601-top extraction liquid inlet; 602-middle extraction liquid inlet; 603-bottom extraction liquid outlet; 604-lower liquid phase material inlet; 7-methanol recovery tower; 701-bottom heavy component outlet; 8-methanol refining tower; 801-methanol outlet; 9-isobutene light component removal tower; 10-isobutene heavy component removal tower; 1001-isobutene outlet; 11-gas-liquid separation tank; 12-tower top reflux pump; 13-condenser; 14-cooler; 15-methanol water washing tower. DETAILED DESCRIPTION

[0136] The technical solutions of the present application are further illustrated by specific embodiments in combination with the accompanying drawings. However, the following examples are only simple examples of the present application, and do not represent or limit the protection scope of the present application, and the protection scope of the present application is subject to the claims.

[0137] Embodiment 1

[0138] The present embodiment provides a device for preparing isobutene and methanol by cracking methyl tert-butyl ether, as shown in the figure, the device comprises, in sequence along the material conveying direction, a methyl tert-butyl ether vaporization and refining tower 1, a reactor 2, a cooling tower 3, an absorption tower 4, a compressor 5, a methanol extraction tower 6, an isobutene light component removal tower 9 and an isobutene heavy component removal tower 10. Figure 1 The device further comprises, in sequence along the material conveying direction, a methanol recovery tower 7 and a methanol refining tower 8.

[0139]

[0140] ​The methyl tert-butyl ether vaporization refining column 1 comprises a methyl tert-butyl ether feed port 101, a side outlet 102, a vaporization refining top outlet 103 and a vaporization refining bottom outlet 104; the side outlet 102 is connected with the reactor 2; as shown in the figure, the device further comprises a gas-liquid separation tank 11 connected with the top of the methyl tert-butyl ether vaporization refining column 1, a column top reflux pump 12, a condenser 13 and a cooler 14. Figure 2

[0141] The methyl tert-butyl ether vaporization refining column 1 is a variable-diameter column, comprising a first column section and a second column section from bottom to top; the total number of column plates of the methyl tert-butyl ether vaporization refining column 1 is 48; the number of column plates of the first column section is 43; the number of column plates of the second column section is 5; the ratio of the column diameter of the second column section to the column diameter of the first column section is 0.6:1; the methyl tert-butyl ether feed port 101 and the side outlet 102 are both located in the first column section; and the methyl tert-butyl ether feed port 101 is located below the side outlet 102.

[0142] The reactor 2 is a fixed-bed reactor with tubes.

[0143] The cooling tower 3 is a packed column with 18 column plates; the cooling tower 3 comprises a top cooling absorption liquid inlet 301, a bottom cooling absorption liquid outlet 302 and a top outlet 303; the bottom cooling absorption liquid outlet 302 of the cooling tower is connected with the methyl alcohol recovery column 7.

[0144] The absorption tower 4 is a packed column with 20 column plates; the absorption tower 4 comprises a top absorbent inlet 401, a bottom absorbent outlet 402 and a lower gas phase material inlet 403; the top outlet 303 of the cooling tower is connected with the lower gas phase material inlet 403 of the absorption tower; the bottom absorbent outlet 402 of the absorption tower is connected with the top cooling absorption liquid inlet 301 of the cooling tower in circulation.

[0145] The methyl alcohol extraction column 6 is a plate column with 30 column plates; the methyl alcohol extraction column 6 comprises a top extraction liquid inlet 601, a middle extraction liquid inlet 602, a bottom extraction liquid outlet 603 and a lower liquid phase material inlet 604; the bottom extraction liquid outlet 603 of the methyl alcohol extraction column is connected with the top absorbent inlet 401 of the absorption tower in circulation; the lower liquid phase material inlet 604 of the methyl alcohol extraction column is connected with the compressor 5.

[0146] The methyl alcohol recovery column 7 is a plate column with 48 column plates; the methyl alcohol recovery column 7 comprises a bottom heavy component outlet 701; the bottom heavy component outlet 701 of the methyl alcohol recovery column is connected with the middle extraction liquid inlet 602 of the methyl alcohol extraction column in circulation.

[0147] ​The methanol refining tower 8 is a plate tower, and the number of plates is 32; the bottom of the methanol refining tower is provided with a methanol discharge port 801.

[0148] The isobutene light-removing tower 9 is a plate tower, and the number of plates is 46; the isobutene heavy-removing tower 10 is a plate tower, and the number of plates is 42, and the top of the isobutene heavy-removing tower is provided with an isobutene discharge port 1001.

[0149] Embodiment 2

[0150] The embodiment provides a device for preparing isobutene and methanol by cracking methyl tert-butyl ether, which comprises, in sequence along a material conveying direction, a methyl tert-butyl ether vaporization refining tower, a reactor, a cooling tower, an absorption tower, a compressor, a methanol extraction tower, an isobutene light-removing tower and an isobutene heavy-removing tower.

[0151] The device further comprises, in sequence along the material conveying direction, a methanol recovery tower and a methanol refining tower.

[0152] The methyl tert-butyl ether vaporization refining tower comprises a methyl tert-butyl ether feeding port, a side outlet, a vaporization refining top discharge port and a vaporization refining bottom discharge port; the side outlet is connected with the reactor; the device further comprises a gas-liquid separation tank connected with the top of the methyl tert-butyl ether vaporization refining tower, a tower top reflux pump, a condenser and a cooler.

[0153] The methyl tert-butyl ether vaporization refining tower is a variable-diameter tower, which comprises, in sequence from bottom to top, a first tower section and a second tower section; the total number of plates of the methyl tert-butyl ether vaporization refining tower is 45; the number of plates of the first tower section is 40; the number of plates of the second tower section is 5; the ratio of the tower diameter of the second tower section to the tower diameter of the first tower section is 0.7:1; the methyl tert-butyl ether feeding port and the side outlet are both located in the first tower section; and the methyl tert-butyl ether feeding port is located below the side outlet.

[0154] The reactor is a fixed-bed reactor with tubes arranged in lines.

[0155] The cooling tower is a packed tower, and the number of plates is 20; the cooling tower comprises a top cooling absorption liquid feeding port, a top discharge port and a bottom cooling absorption liquid outlet; the bottom cooling absorption liquid outlet of the cooling tower is connected with the methanol recovery tower.

[0156] The absorption tower is a packed tower, and the number of plates is 25; the absorption tower comprises a top absorbent feeding port, a bottom absorbent outlet and a lower gas phase material inlet; the top discharge port of the cooling tower is connected with the lower gas phase material inlet of the absorption tower; the bottom absorbent outlet of the absorption tower is connected with the top cooling absorption liquid feeding port of the cooling tower in circulation.

[0157] The methanol extraction column is a plate column, and the number of plates is 28; the methanol extraction column comprises a top extraction liquid inlet, a middle extraction liquid inlet, a bottom extraction liquid outlet, and a lower liquid phase material inlet; the bottom extraction liquid outlet of the methanol extraction column is connected in circulation with the top absorbent inlet of the absorption tower; and the lower liquid phase material inlet of the methanol extraction column is connected with the compressor.

[0158] The methanol recovery column is a plate column, and the number of plates is 45; the methanol recovery column comprises a bottom heavy component outlet; and the bottom heavy component outlet of the methanol recovery column is connected in circulation with the middle extraction liquid inlet of the methanol extraction column.

[0159] The methanol refining column is a plate column, and the number of plates is 35; the bottom of the methanol refining column is provided with a methanol outlet.

[0160] The isobutene light-removing column is a plate column, and the number of plates is 48; the isobutene heavy-removing column is a plate column, and the number of plates is 40; and the top of the isobutene heavy-removing column is provided with an isobutene outlet.

[0161] Example 3

[0162] The present embodiment provides a device for preparing isobutene and methanol by cracking methyl tert-butyl ether, which comprises, in sequence and along the material conveying direction, a methyl tert-butyl ether vaporization refining column, a reactor, a cooling tower, an absorption tower, a compressor, a methanol extraction column, an isobutene light-removing column, and an isobutene heavy-removing column.

[0163] The device further comprises, in sequence and along the material conveying direction, a methanol recovery column and a methanol refining column.

[0164] The methyl tert-butyl ether vaporization refining column comprises a methyl tert-butyl ether inlet, a side outlet, a vaporization refining top outlet, and a vaporization refining bottom outlet; the side outlet is connected with the reactor; and the device further comprises a gas-liquid separation tank connected with the top of the methyl tert-butyl ether vaporization refining column, a tower top reflux pump, a condenser, and a cooler.

[0165] The methyl tert-butyl ether vaporization refining column is a variable-diameter column, which comprises, in sequence from bottom to top, a first column segment and a second column segment; the total number of plates of the methyl tert-butyl ether vaporization refining column is 50; the number of plates of the first column segment is 44; the number of plates of the second column segment is 6; the ratio of the column diameter of the second column segment to the column diameter of the first column segment is 0.8:1; the methyl tert-butyl ether inlet and the side outlet are both located in the first column segment; and the methyl tert-butyl ether inlet is located below the side outlet.

[0166] The reactor is a fixed-bed reactor with tubes arranged in columns.

[0167] The cooling tower is a packed tower, and the number of trays is 15; the cooling tower comprises a top cooling absorbent inlet, a top outlet, and a bottom cooling absorbent outlet, and the bottom cooling absorbent outlet of the cooling tower is connected to the methanol recovery tower.

[0168] The absorption tower is a packed tower, and the number of trays is 18; the absorption tower comprises a top absorbent inlet, a bottom absorbent outlet, and a lower gas phase material inlet; the top outlet of the cooling tower is connected to the lower gas phase material inlet of the absorption tower; and the bottom absorbent outlet of the absorption tower is connected to the top cooling absorbent inlet of the cooling tower.

[0169] The methanol extraction tower is a plate tower, and the number of trays is 32; the methanol extraction tower comprises a top extraction liquid inlet, a middle extraction liquid inlet, a bottom extraction liquid outlet, and a lower liquid phase material inlet; the bottom extraction liquid outlet of the methanol extraction tower is connected to the top absorbent inlet of the absorption tower; and the lower liquid phase material inlet of the methanol extraction tower is connected to the compressor.

[0170] The methanol recovery tower is a plate tower, and the number of trays is 50; the methanol recovery tower comprises a bottom heavy component outlet; and the bottom heavy component outlet of the methanol recovery tower is connected to the middle extraction liquid inlet of the methanol extraction tower.

[0171] The methanol refining tower is a plate tower, and the number of trays is 30; the bottom of the methanol refining tower is provided with a methanol outlet.

[0172] The isobutene light component removal tower is a plate tower, and the number of trays is 44; the isobutene heavy component removal tower is a plate tower, and the number of trays is 43; and the top of the isobutene heavy component removal tower is provided with an isobutene outlet.

[0173] Example 4

[0174] The present example provides a device for preparing isobutene and methanol by cracking methyl tert-butyl ether, which is identical to example 1 except that the ratio of the column diameter of the second column section to the column diameter of the first column section in the methyl tert-butyl ether vaporization refining tower is 0.5:1.

[0175] Example 5

[0176] The present example provides a device for preparing isobutene and methanol by cracking methyl tert-butyl ether, which is identical to example 1 except that the ratio of the column diameter of the second column section to the column diameter of the first column section in the methyl tert-butyl ether vaporization refining tower is 0.9:1.

[0177] Example 6

[0178] The embodiment provides a device for preparing isobutene and methanol by cracking methyl tert-butyl ether, which is different from the device in the embodiment 1 only in that, in addition to that the methyl tert-butyl ether vaporization and refining tower is an isometric tower, the rest is the same as the embodiment 1.

[0179] Comparative example 1

[0180] The comparative example provides a device for preparing isobutene and methanol by cracking methyl tert-butyl ether, which is different from the device in the embodiment 1 only in that, in addition to that the device comprises, in sequence and along the material conveying direction, an isometric methyl tert-butyl ether vaporization and refining tower 1, a reactor 2, a cooler 14, a gas-liquid separation tank 11, a compressor 5, a methanol water washing tower 15, an isobutene light-removing tower 9 and an isobutene heavy-removing tower 10; the device further comprises, along the material conveying direction, a methanol recovery tower 7, the top of the methanol recovery tower 7 is provided with a methanol discharge port; the methanol recovery tower 7 further comprises a bottom liquid phase inlet and a bottom liquid phase outlet.

[0181] The methanol water washing tower 15 comprises a bottom washing liquid outlet, the bottom washing liquid outlet is connected with the bottom liquid phase inlet of the methanol recovery tower 7 in circulation, and the bottom liquid phase outlet is connected with the methanol water washing tower 15.

[0182] The methanol water washing tower 15 is a plate tower, and the number of tower plates is 26, and the rest is the same as the embodiment 1.

[0183] The device for preparing isobutene and methanol by cracking methyl tert-butyl ether in the comparative example is as shown in the figure. Figure 3

[0184] Application example 1

[0185] The application example provides a method for preparing isobutene and methanol by cracking methyl tert-butyl ether, which is carried out by using the device in the embodiment 1, and the method comprises the following steps.

[0186] (1) raw materials containing methyl tert-butyl ether and having a temperature of 98 DEG C are sent to the 25th tower plate of the first tower section of the variable-diameter methyl tert-butyl ether vaporization and refining tower for refining treatment, so as to obtain refined methyl tert-butyl ether in a gaseous phase and having a temperature of 108 DEG C; wherein the purity of methyl tert-butyl ether in the raw materials is 98%, the refined methyl tert-butyl ether is collected from the 16th tower plate of the first tower section, the top pressure of the methyl tert-butyl ether vaporization and refining tower is 0.32 MPa, the top temperature is 75 DEG C, and the top liquid phase is totally refluxed, the temperature of the tower kettle of the methyl tert-butyl ether vaporization and refining tower is 120 DEG C, the pressure of the gas-liquid separation tank connected with the top of the methyl tert-butyl ether vaporization and refining tower is 0.12 MPa, and the temperature is 40 DEG C.

[0187] (2) the refined methyl tert-butyl ether in step (1) is sent to the reactor 2, the temperature of the reactor 2 is 240 DEG C, the pressure is 0.15 MPa, the space velocity is 0.7 h -1 ​The mixture gas is subjected to a cracking reaction in a reactor in the presence of a catalyst to obtain a mixed gas of isobutene and methanol; wherein the catalyst comprises a carrier, an active component and an auxiliary agent supported on the carrier, and the mass ratio of the active component to the carrier is 1:3; the carrier comprises silica and alumina with a mass ratio of 5.5:1, the active component comprises phosphomolybdic acid and phosphotungstic acid with a mass ratio of 1:15, and the auxiliary agent comprises V, Ce and Cs; and the content of V in the catalyst is 0.03:1 of the total mass of the catalyst, the content of Ce in the catalyst is 0.06:1 of the total mass of the catalyst, and the content of Cs in the catalyst is 0.18:1 of the total mass of the catalyst, in terms of V2O5, CeO2 and Cs, respectively;

[0188] (3) The mixed gas in step (2) is subjected to a cooling treatment in a cooling tower with a tower top pressure of 0.05 MPa, a tower top temperature of 55 ℃ and a liquid-gas ratio of 10 L / m 3 to obtain a gas phase containing isobutene and a liquid phase containing methanol; the mass percentage of methanol in the liquid phase containing methanol is 41%;

[0189] (4) The liquid phase containing methanol is subjected to a first rectification treatment in a methanol recovery tower with a tower top pressure of 0.035 MPa, a tower top temperature of 72 ℃, a tower top reflux ratio of 1.8, a tower bottom pressure of 0.06 MPa and a tower bottom temperature of 113 ℃ to obtain crude methanol and an aqueous phase, wherein a first part of the aqueous phase is returned to the methanol extraction tower for recycling, the mass percentage of methanol in the first part of the aqueous phase is 0.155%, a second part of the aqueous phase is discharged, and the crude methanol is subjected to a second rectification treatment in a methanol refining tower with a tower top pressure of 0.35 MPa, a tower top temperature of 72 ℃, a tower top reflux ratio of 4, a tower bottom pressure of 0.39 MPa and a tower bottom temperature of 93 ℃ to obtain methanol; the volume ratio of the first part of the aqueous phase to the second part of the aqueous phase is 8:1;

[0190] (5) The gas phase containing isobutene is subjected to a rectification treatment in a tower with a tower top pressure of 0.025 MPa, a tower top temperature of 39 ℃ and a liquid-gas ratio of 7 L / m 3absorption tower, to obtain a demethanized isobutene gas phase and an absorption rich liquid, the mass percentage of methanol in the absorption rich liquid being 17%, the absorption rich liquid being returned to the cooling tower to be recycled as a cooling absorption liquid, the demethanized isobutene gas phase being subjected to compression treatment in a compressor to obtain an isobutene-containing liquid phase, the isobutene-containing liquid phase being subjected to extraction treatment in a methanol extraction tower with a tower top pressure of 0.46 MPa, a tower top temperature of 39°C, a tower bottom pressure of 0.78 MPa and a tower bottom temperature of 40°C, to obtain crude isobutene and a treated extraction agent, the extraction agent used in the extraction treatment comprising desalted water and the first part of the aqueous phase in a volume ratio of 1:9.5, and the mass ratio of the extraction agent used in the extraction treatment to the isobutene-containing liquid phase being 0.82:1; the mass percentage of methanol in the treated extraction agent being 1.7%, the treated extraction agent being returned to the absorption tower to be recycled as an absorbent.

[0191] The crude isobutene is subjected to first purification treatment and second purification treatment in a isobutene light-removing tower with a tower top pressure of 0.76 MPa, a tower top temperature of 51°C, full reflux of the tower top liquid phase, a tower bottom pressure of 0.79 MPa and a tower bottom temperature of 67°C, and a isobutene heavy-removing tower with a tower top pressure of 0.6 MPa, a tower top temperature of 56°C, a tower top reflux ratio of 1.8, a tower bottom pressure of 0.63 MPa and a tower bottom temperature of 92°C, to obtain isobutene.

[0192] Application Example 2

[0193] This application example provides a method for preparing isobutene and methanol by cracking methyl tert-butyl ether, which is carried out by using the device in Example 2, and the method comprises the following steps:

[0194] (1) The raw material containing methyl tert-butyl ether and having a temperature of 95°C is fed into the 26th tray of the first tower section of the variable-diameter methyl tert-butyl ether vaporization refining tower to be subjected to refining treatment, to obtain gaseous refined methyl tert-butyl ether having a temperature of 105°C; wherein the purity of methyl tert-butyl ether in the raw material is 98.2%, the refined methyl tert-butyl ether is collected from the 17th tray of the first tower section, the tower top pressure of the methyl tert-butyl ether vaporization refining tower is 0.35 MPa, the tower top temperature is 80°C and the tower top liquid phase is fully refluxed, the tower bottom temperature of the methyl tert-butyl ether vaporization refining tower is 125°C, and the pressure of the gas-liquid separation tank connected to the top of the methyl tert-butyl ether vaporization refining tower is 0.11 MPa and the temperature is 38°C;

[0195] (2) The refined methyl tert-butyl ether in step (1) is subjected to cracking treatment in a temperature of 280°C, a pressure of 0.2 MPa and an airspeed of 1.0 h -1The mixture gas is subjected to a cracking reaction in a reactor in the presence of a catalyst to obtain a mixed gas of isobutene and methanol; wherein the catalyst comprises a carrier, an active component and an auxiliary agent supported on the carrier, and the mass ratio of the active component to the carrier is 1:4; the carrier comprises silica and alumina with a mass ratio of 5:1, the active component comprises phosphotungstic acid, and the auxiliary agent comprises V, Ce and Cs; and the content of V in the catalyst is 0.02:1 of the total mass of the catalyst, the content of Ce in the catalyst is 0.08:1 of the total mass of the catalyst, and the content of Cs in the catalyst is 0.19:1 of the total mass of the catalyst, all in terms of V2O5, CeO2 and Cs;

[0196] (3) The mixed gas in step (2) is subjected to a cooling treatment in a cooling tower with a tower top pressure of 0.04 MPa, a tower top temperature of 54 ℃ and a liquid-gas ratio of 12 L / m 3 to obtain a gas phase containing isobutene and a liquid phase containing methanol; the mass percentage of methanol in the liquid phase containing methanol is 40%;

[0197] (4) The liquid phase containing methanol is subjected to a first rectification treatment in a methanol recovery tower with a tower top pressure of 0.04 MPa, a tower top temperature of 75 ℃, a tower top reflux ratio of 2.0, a tower bottom pressure of 0.07 MPa and a tower bottom temperature of 115 ℃ to obtain crude methanol and an aqueous phase, wherein a first part of the aqueous phase is returned to the methanol extraction tower for recycling, the mass percentage of methanol in the first part of the aqueous phase is 0.16%, and a second part of the aqueous phase is discharged, and the crude methanol is subjected to a second rectification treatment in a methanol refining tower with a tower top pressure of 0.34 MPa, a tower top temperature of 71 ℃, a tower top reflux ratio of 3, a tower bottom pressure of 0.38 MPa and a tower bottom temperature of 92 ℃ to obtain methanol; the volume ratio of the first part of the aqueous phase to the second part of the aqueous phase is 8.5:1;

[0198] (5) The gas phase containing isobutene is subjected to a rectification treatment in a tower with a tower top pressure of 0.03 MPa, a tower top temperature of 40 ℃ and a liquid-gas ratio of 8 L / m 3absorption tower, to obtain a demethanized isobutene gas phase and an absorption rich liquid, the mass percentage of methanol in the absorption rich liquid being 18%, the absorption rich liquid being returned to the cooling tower to be recycled as a cooling absorption liquid, the demethanized isobutene gas phase being subjected to compression treatment in a compressor to obtain an isobutene-containing liquid phase, the isobutene-containing liquid phase being subjected to extraction treatment in a methanol extraction tower with a tower top pressure of 0.45 MPa, a tower top temperature of 38°C, a tower bottom pressure of 0.76 MPa and a tower bottom temperature of 39°C, to obtain crude isobutene and a treated extraction agent, the extraction agent used in the extraction treatment comprising desalted water and the first part of the aqueous phase in a volume ratio of 1:9, and the mass ratio of the extraction agent used in the extraction treatment to the isobutene-containing liquid phase being 0.8:1; the mass percentage of methanol in the treated extraction agent being 1.8%, and the treated extraction agent being returned to the absorption tower to be recycled as an absorbent.

[0199] The crude isobutene is subjected to first purification treatment and second purification treatment in a isobutene light-removing tower with a tower top pressure of 0.75 MPa, a tower top temperature of 50°C, full reflux of the tower top liquid phase, a tower bottom pressure of 0.79 MPa and a tower bottom temperature of 66°C, and a isobutene heavy-removing tower with a tower top pressure of 0.61 MPa, a tower top temperature of 56.5°C, a tower top reflux ratio of 2.0, a tower bottom pressure of 0.64 MPa and a tower bottom temperature of 93°C, to obtain isobutene.

[0200] Application Example 3

[0201] The present application provides a method for preparing isobutene and methanol by cracking methyl tert-butyl ether, and the present application is carried out by using the device in Example 3, the method comprising the following steps:

[0202] (1) feeding raw material containing methyl tert-butyl ether and having a temperature of 100°C into the 24th tray of the first tower section of a variable-diameter methyl tert-butyl ether vaporization refining tower to obtain refined methyl tert-butyl ether in a gas phase and having a temperature of 110°C; wherein the purity of methyl tert-butyl ether in the raw material is 98.1%, the refined methyl tert-butyl ether is collected from the 15th tray of the first tower section, the tower top pressure of the methyl tert-butyl ether vaporization refining tower is 0.3 MPa, the tower top temperature is 69°C and the tower top liquid phase is fully refluxed, the tower bottom temperature of the methyl tert-butyl ether vaporization refining tower is 118°C, and the pressure of the gas-liquid separation tank connected to the top of the methyl tert-butyl ether vaporization refining tower is 0.14 MPa and the temperature is 45°C;

[0203] (2) feeding the refined methyl tert-butyl ether in step (1) into a reactor with a temperature of 180°C, a pressure of 0.1 MPa and an airspeed of 0.3 h -1The mixture gas is subjected to a cracking reaction in a reactor in the presence of a catalyst to obtain a mixed gas of isobutene and methanol; wherein the catalyst comprises a carrier, an active component and an auxiliary agent supported on the carrier, and the mass ratio of the active component to the carrier is 1:3.5; the carrier comprises silica and alumina at a mass ratio of 6:1, the active component comprises phosphomolybdic acid and phosphotungstic acid at a mass ratio of 1:8, and the auxiliary agent comprises V, Ce and Cs; and the content of V in the catalyst is 0.05:1 based on V2O5, the content of Ce in the catalyst is 0.05:1 based on CeO2, and the content of Cs in the catalyst is 0.16:1 based on Cs;

[0204] (3) The mixed gas obtained in step (2) is subjected to cooling treatment in a cooling tower with a tower top pressure of 0.06 MPa, a tower top temperature of 56 ℃ and a liquid-gas ratio of 8 L / m 3 to obtain a gas phase containing isobutene and a liquid phase containing methanol; the mass percentage of methanol in the liquid phase containing methanol is 42%;

[0205] (4) The liquid phase containing methanol is subjected to first rectification treatment in a methanol recovery tower with a tower top pressure of 0.03 MPa, a tower top temperature of 70 ℃, a tower top reflux ratio of 1.5, a tower bottom pressure of 0.05 MPa and a tower bottom temperature of 110 ℃ to obtain crude methanol and an aqueous phase, wherein a first part of the aqueous phase is returned to the methanol extraction tower for recycling, the mass percentage of methanol in the first part of the aqueous phase is 0.15%, and a second part of the aqueous phase is discharged, and the crude methanol is subjected to second rectification treatment in a methanol refining tower with a tower top pressure of 0.36 MPa, a tower top temperature of 73 ℃, a tower top reflux ratio of 5, a tower bottom pressure of 0.4 MPa and a tower bottom temperature of 95 ℃ to obtain methanol; the volume ratio of the first part of the aqueous phase to the second part of the aqueous phase is 7.7:1;

[0206] (5) The gas phase containing isobutene is subjected to absorption treatment in an absorption tower with a tower top pressure of 0.02 MPa, a tower top temperature of 38 ℃ and a liquid-gas ratio of 6 L / m 3 to obtain a methanol-removed isobutene gas phase and an absorption rich liquid, the mass percentage of methanol in the absorption rich liquid is 16%, the absorption rich liquid is returned to the cooling tower for recycling as a cooling absorption liquid, and the methanol-removed isobutene gas phase is subjected to compression treatment in a compressor to obtain an isobutene-containing liquid phase, which is subjected to extraction treatment in a methanol extraction tower with a tower top pressure of 0.48 MPa, a tower top temperature of 40 ℃, a tower bottom pressure of 0.8 MPa and a tower bottom temperature of 41 ℃ to obtain crude isobutene and a treated extraction agent, the extraction agent used in the extraction treatment comprises desalted water and the first part of the aqueous phase at a volume ratio of 1:10, and the mass ratio of the extraction agent used in the extraction treatment to the isobutene-containing liquid phase is 0.85:1.

[0207] The crude isobutene is subjected to first purification treatment and second purification treatment in an isobutene light-removing column with a column top pressure of 0.78 MPa, a column top temperature of 52°C, full reflux of liquid phase at the column top, a column bottom pressure of 0.8 MPa, and a column bottom temperature of 68°C, and an isobutene heavy-removing column with a column top pressure of 0.59 MPa, a column top temperature of 55°C, a column top reflux ratio of 1.7, a column bottom pressure of 0.62 MPa, and a column bottom temperature of 90°C, to obtain isobutene, the mass percentage of methanol in the treated extractant is 1.6%, and the treated extractant is returned to the absorption tower to be recycled as absorbent.

[0208] Application Example 4

[0209] This application example provides a method for preparing isobutene and methanol by cracking methyl tert-butyl ether, which is different from application example 1 only in that, in addition to using the device for preparing isobutene and methanol by cracking methyl tert-butyl ether provided in example 4, the rest is the same as application example 1.

[0210] Application Example 5

[0211] This application example provides a method for preparing isobutene and methanol by cracking methyl tert-butyl ether, which is different from application example 1 only in that, in addition to using the device for preparing isobutene and methanol by cracking methyl tert-butyl ether provided in example 5, the rest is the same as application example 1.

[0212] Application Example 6

[0213] This application example provides a method for preparing isobutene and methanol by cracking methyl tert-butyl ether, which is different from application example 1 only in that, in addition to using the device for preparing isobutene and methanol by cracking methyl tert-butyl ether provided in example 6, the rest is the same as application example 1.

[0214] Application Example 7

[0215] This application example provides a method for preparing isobutene and methanol by cracking methyl tert-butyl ether, which is different from application example 1 only in that, in addition to the mass ratio of the active component to the carrier in the catalyst being 1:6, the rest is the same as application example 1.

[0216] Application Example 8

[0217] This application example provides a method for preparing isobutene and methanol by cracking methyl tert-butyl ether, which is different from application example 1 only in that, in addition to the mass ratio of the active component to the carrier in the catalyst being 2:3, the rest is the same as application example 1.

[0218] Application Example 9

[0219] The application example provides a method for preparing isobutene and methanol by cracking methyl tert-butyl ether, which is different from the application example 1 only in that the mass ratio of the silica and the alumina in the carrier of the catalyst is 8:1, and the rest is the same as the application example 1.

[0220] Application example 10

[0221] The application example provides a method for preparing isobutene and methanol by cracking methyl tert-butyl ether, which is different from the application example 1 only in that the mass ratio of the silica and the alumina in the carrier of the catalyst is 4:1, and the rest is the same as the application example 1.

[0222] Application example 11

[0223] The application example provides a method for preparing isobutene and methanol by cracking methyl tert-butyl ether, which is different from the application example 1 only in that the mass ratio of the phosphomolybdic acid and the phosphotungstic acid in the active component of the catalyst is 1:4, and the rest is the same as the application example 1.

[0224] Application example 12

[0225] The application example provides a method for preparing isobutene and methanol by cracking methyl tert-butyl ether, which is different from the application example 1 only in that the ratio of the content of V in the catalyst to the total mass of the catalyst is 0.01:1, and the rest is the same as the application example 1.

[0226] Application example 13

[0227] The application example provides a method for preparing isobutene and methanol by cracking methyl tert-butyl ether, which is different from the application example 1 only in that the ratio of the content of V in the catalyst to the total mass of the catalyst is 0.1:1, and the rest is the same as the application example 1.

[0228] Application example 14

[0229] The application example provides a method for preparing isobutene and methanol by cracking methyl tert-butyl ether, which is different from the application example 1 only in that the ratio of the content of Ce in the catalyst to the total mass of the catalyst is 0.02:1, and the rest is the same as the application example 1.

[0230] Application example 15

[0231] The application example provides a method for preparing isobutene and methanol by cracking methyl tert-butyl ether, which is different from the application example 1 only in that the ratio of the content of Ce in the catalyst to the total mass of the catalyst is 0.1:1, and the rest is the same as the application example 1.

[0232] Application example 16

[0233] The application example provides a method for preparing isobutene and methanol by cracking methyl tert-butyl ether, which is different from the application example 1 only in that, in addition to the content of Cs in the catalyst being 0.1:1 relative to the total mass of the catalyst, the rest is the same as the application example 1.

[0234] Application example 17

[0235] The application example provides a method for preparing isobutene and methanol by cracking methyl tert-butyl ether, which is different from the application example 1 only in that, in addition to the content of Cs in the catalyst being 0.25:1 relative to the total mass of the catalyst, the rest is the same as the application example 1.

[0236] Comparative application example 1

[0237] The comparative application example provides a method for preparing isobutene and methanol by cracking methyl tert-butyl ether, which is different from the application example 1 only in that, in addition to the method being carried out by using the device for preparing isobutene and methanol by cracking methyl tert-butyl ether provided in the comparative example 1, and the top temperature of the methanol washing tower being 40 DEG C, the top pressure being 0.1 MPa, the bottom temperature being 41 DEG C, the bottom pressure being 0.11 MPa and the liquid-gas ratio being 7:1 L / m 3 , the rest of the corresponding equipment related parameters are the same as the application example 1.

[0238] Comparative application example 2

[0239] The comparative application example provides a method for preparing isobutene and methanol by cracking methyl tert-butyl ether, which is different from the application example 1 only in that, in addition to the YL-2 type heteropoly acid catalyst being added in the cracking reaction of the step (2), the rest is the same as the application example 1.

[0240] Comparative application example 3

[0241] The comparative application example provides a method for preparing isobutene and methanol by cracking methyl tert-butyl ether, which is different from the application example 1 only in that, in addition to the ZSM-5 based catalyst being used in the cracking reaction of the step (2), the rest is the same as the application example 1.

[0242] The purity of isobutene and methanol obtained from the application examples 1 to 17 and the comparative application examples 1 to 3 is tested by using a gas chromatography method, the content of dimerized isobutene in the isobutene is tested, and the yield of isobutene and methanol is calculated by the following formula:

[0243] The yield of methanol (%) = the mass of methanol x the purity of methanol / the theoretical equivalent value of methanol x 100%;

[0244] The yield of isobutene (%) = mass of isobutene x purity of isobutene / theoretical equivalent value of isobutene x 100%; and the service life of the catalyst is detected, and the service life of the catalyst is the time when the selectivity of the catalyst is greater than 90% of the initial selectivity, and the detection results are shown in Table 1.

[0245] Table 1

[0246]

[0247] It can be seen from the test results that:

[0248] (1) It can be seen from application examples 1 to 3 that the device for preparing isobutene and methanol by cracking methyl tert-butyl ether provided by the application can not only relax the restriction on the purity of methyl tert-butyl ether in the raw material containing methyl tert-butyl ether, so that the purity of methyl tert-butyl ether in the raw material is greater than or equal to 98%, but also can prepare isobutene with a purity of up to 99.99% and methanol with a purity of greater than 99.9%, and the yield of isobutene is greater than 96.5%, the yield of methanol is greater than 97.5%, and the service life of the catalyst is greater than 3 years.

[0249] (2) It can be seen from application examples 1 and 4-6 that by limiting the ratio of the column diameter of the second column section to the column diameter of the first column section of the methyl tert-butyl ether vaporization refining tower, the purity of refined methyl tert-butyl ether can be increased, and liquid flooding or mist entrainment under high load can be avoided. If the ratio of the column diameter of the second column section to the column diameter of the first column section of the methyl tert-butyl ether vaporization refining tower is not within the preferred range, the refining effect of methyl tert-butyl ether will be affected, and under the condition that the purity of the methyl tert-butyl ether raw material is 98%, the purity of isobutene or methanol will be reduced.

[0250] (3) By application example 1 and application example 7-8 can be seen, the mass ratio of active component and carrier in the catalyst used in application example 1 is 1:3, the yield of isobutylene obtained by reaction is 96.6%, the yield of methanol is 97.6%, and at the same time, the service life of the catalyst is 3.4 years; while the mass ratio of active component and carrier in the catalyst used in application example 7 is 1:6, the yield of isobutylene obtained by reaction is 96%, the yield of methanol is 97%, and at the same time, the service life of the catalyst is 2.6 years, the mass ratio of active component and carrier in the catalyst used in application example 8 is 2:3, the yield of isobutylene obtained by reaction is 95.6%, the yield of methanol is 96.5%, and at the same time, the service life of the catalyst is 2.8 years, so it can be seen that the mass ratio of active component and carrier in the catalyst is limited to 1:(3-4) in the application, this ratio can make the catalyst have a higher specific surface area and strength, and ensure sufficient active component loading on the catalyst, the high specific surface area can make the active component of the catalyst have efficient mass transfer with the gas phase reactants in the reaction process, and improve the catalytic efficiency of the catalyst. At the same time, the high strength of the carrier also makes the catalyst run for a long period of time, avoiding crushing and pulverization.

[0251] (4) By application example 1 and application example 9-10 can be seen, the mass ratio of silica and alumina in the carrier of the catalyst used in application example 1 is 5.5:1, the service life of the catalyst is 3.4 years; while the mass ratio of silica and alumina in the carrier of the catalyst used in application example 9 is 8:1, the service life of the catalyst is 3 years, the mass ratio of silica and alumina in the carrier of the catalyst used in application example 10 is 4:1, the service life of the catalyst is 2.8 years, so it can be seen that by limiting the mass ratio of silica and alumina in the carrier of the catalyst, the catalyst can have high strength to prolong the service life of the catalyst.

[0252] (5) By application example 1 and application example 11 can be seen, the mass ratio of phosphomolybdic acid and phosphotungstic acid in the active component of the catalyst used in application example 1 is 1:15, the yield of isobutylene obtained by reaction is 96.6%, the yield of methanol is 97.6%, and at the same time, the service life of the catalyst is 3.4 years; while the mass ratio of phosphomolybdic acid and phosphotungstic acid in the active component of the catalyst used in application example 11 is 1:4, the yield of isobutylene obtained by reaction is 95.4%, the yield of methanol is 96.5%, and at the same time, the service life of the catalyst is 3.2 years, so it can be seen that if the content of molybdenum in the catalyst used in the application is too high, it will lead to a decrease in catalyst activity, ultimately reducing the yield of isobutylene and methanol.

[0253] (6) As can be seen from the application example 1 and the application examples 12-13, the ratio of the content of V in the catalyst used in the application example 1 to the total mass of the catalyst is 0.03:1, the purity of the methanol obtained by the reaction is 99.93wt%, and the service life of the catalyst is 3.4 years; the ratio of the content of V in the catalyst used in the application example 12 to the total mass of the catalyst is 0.01:1, the purity of the methanol obtained by the reaction is 99.93wt%, and the service life of the catalyst is 2.3 years; the ratio of the content of V in the catalyst used in the application example 13 to the total mass of the catalyst is 0.1:1, the purity of the methanol obtained by the reaction is 99.81wt%, and the service life of the catalyst is 3 years; thus, it can be seen that the content of V in the catalyst of the present application has an optimal range, if the content of V is lower than the optimal range, the service life of the catalyst will be obviously reduced, and if the content of V is higher than the optimal range, by-products which are difficult to separate from the methanol will be produced, resulting in the reduction of the purity of the methanol.

[0254] (7) As can be seen from the application example 1 and the application examples 14-15, the ratio of the content of Ce in the catalyst used in the application example 1 to the total mass of the catalyst is 0.06:1, the purity of the methanol obtained by the reaction is 99.93wt%, and the service life of the catalyst is 3.4 years; the ratio of the content of Ce in the catalyst used in the application example 14 to the total mass of the catalyst is 0.02:1, the purity of the methanol obtained by the reaction is 99.93wt%, and the service life of the catalyst is 2.4 years; the ratio of the content of Ce in the catalyst used in the application example 15 to the total mass of the catalyst is 0.1:1, the purity of the methanol obtained by the reaction is 99.78wt%, and the service life of the catalyst is 3.2 years; thus, it can be seen that the content of Ce in the catalyst of the present application has an optimal range, if the content of Ce is lower than the optimal range, the service life of the catalyst will be obviously reduced, and if the content of Ce is higher than the optimal range, by-products which are difficult to separate from the methanol will be produced, resulting in the reduction of the purity of the methanol and the increase of the content of the dimerized isobutylene in the isobutylene.

[0255] (8) By applying example 1 and application examples 16-17, it can be seen that the ratio of the content of Cs in the catalyst used in application example 1 to the total mass of the catalyst is 0.18:1, the content of dimerized isobutene in the isobutene obtained by the reaction is 0.5 ppm, the purity of methanol is 99.93 wt%, and at the same time, the service life of the catalyst is 3.4 years; while in application example 16, the ratio of the content of Cs in the catalyst to the total mass of the catalyst is 0.1:1, the content of dimerized isobutene in the isobutene obtained by the reaction is 20 ppm, the purity of methanol is 99.86 wt%, and at the same time, the service life of the catalyst is 2.3 years; in application example 17, the ratio of the content of Cs in the catalyst to the total mass of the catalyst is 0.25:1, the content of dimerized isobutene in the isobutene obtained by the reaction is 5 ppm, the purity of methanol is 99.83 wt%, and at the same time, the service life of the catalyst is 3.2 years; it can be seen that the content of Cs in the catalyst of the present application has an optimal range, if the content of Cs is lower than the optimal range, the service life of the catalyst will be significantly reduced, and at the same time, the content of dimerized isobutene in isobutene will increase; if the content of Cs is higher than the optimal range, the production of by-products will increase, resulting in a decrease in the purity and yield of methanol.

[0256] (9) By comparing application example 1 with comparative application example 1, it can be seen that the device for preparing isobutene and methanol by cracking methyl tert-butyl ether of the present application is improved, which not only relaxes the restriction on the purity of methyl tert-butyl ether in the raw material containing methyl tert-butyl ether, so that the purity of methyl tert-butyl ether in the raw material is ≥98%, but also can prepare isobutene with a purity of more than 99.9% and methanol with a purity of more than 99.9%.

[0257] (10) By comparing application example 1 with comparative application examples 2-3, it can be seen that by designing the catalyst used in the cracking reaction, the catalyst of the present application has a longer service life and higher product yield compared with the catalysts in the prior art.

[0258] In summary, the device for preparing isobutene and methanol by cracking methyl tert-butyl ether of the present application not only relaxes the restriction on the purity of methyl tert-butyl ether in the raw material containing methyl tert-butyl ether, so that the purity of methyl tert-butyl ether in the raw material is ≥98%, but also can prepare isobutene with a purity of more than 99.9% and methanol with a purity of more than 99.9%; at the same time, the selectivity of the catalyst used in the present application is high, and the service life of the catalyst can be more than 3 years.

[0259] The applicant declares that the above description is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and those skilled in the art should understand that any changes or replacements within the technical scope disclosed by the present application can be easily thought of by any person skilled in the art, and all fall within the protection scope and disclosure scope of the present application.

Claims

1. A plant for the production of isobutene and methanol by cleavage of methyl tert-butyl ether, characterized in that, The device comprises, in sequence along the material conveying direction, a methyl tert-butyl ether vaporization refining tower, a reactor, a cooling tower, an absorption tower, a methanol extraction tower, an isobutylene light component removal tower, and an isobutylene heavy component removal tower; The cooling tower comprises a top cooling absorption liquid inlet, a top outlet, and a bottom cooling absorption liquid outlet; The absorption tower comprises a top absorption agent inlet, a bottom absorption agent outlet, and a lower gas phase material inlet; The top outlet of the cooling tower is connected to the lower gas phase material inlet of the absorption tower, and the bottom absorption agent outlet of the absorption tower is connected to the top cooling absorption liquid inlet of the cooling tower in circulation; The methanol extraction tower comprises a bottom extraction liquid outlet, and the bottom extraction liquid outlet of the methanol extraction tower is connected to the top absorption agent inlet of the absorption tower in circulation; The isobutylene heavy component removal tower is provided with an isobutylene outlet at the top; The device further comprises, in sequence along the material conveying direction, a methanol recovery tower and a methanol refining tower; the bottom cooling absorption liquid outlet of the cooling tower is connected to the methanol recovery tower, and the methanol refining tower is provided with a methanol outlet at the bottom.

2. The apparatus of claim 1, wherein, The methyl tert-butyl ether vaporization refining tower comprises, from bottom to top, a first tower section and a second tower section; Preferably, the total number of tower plates of the methyl tert-butyl ether vaporization refining tower is 45-50; Preferably, the number of tower plates of the first tower section is 40-45; Preferably, the number of tower plates of the second tower section is 4-6; Preferably, the methyl tert-butyl ether vaporization refining tower is a variable-diameter tower; Preferably, the diameter of the second tower section is smaller than that of the first tower section; Preferably, the ratio of the diameter of the second tower section to that of the first tower section is (0.6-0.8):1; Preferably, the methyl tert-butyl ether vaporization refining tower comprises a methyl tert-butyl ether inlet and a side outlet, and the side outlet is connected to the reactor; Preferably, the methyl tert-butyl ether inlet and the side outlet are both located in the first tower section; Preferably, the methyl tert-butyl ether inlet is located below the side outlet.

3. The apparatus of claim 1 or 2, wherein, The device further comprises a compressor arranged between the absorption tower and the methanol extraction tower; Preferably, the methanol extraction tower further comprises a top extraction liquid inlet, a middle extraction liquid inlet, and a lower liquid phase material inlet; Preferably, the lower liquid phase material inlet of the methanol extraction tower is connected to the compressor; Preferably, the methanol recovery tower comprises a bottom heavy component outlet; Preferably, the bottom heavy component outlet of the methanol recovery tower is connected to the middle extraction liquid inlet of the methanol extraction tower in circulation; Preferably, the number of tower plates of the cooling tower is 15-20; Preferably, the number of tower plates of the methanol recovery tower is 45-50; Preferably, the number of tower plates of the methanol refining tower is 30-35; Preferably, the number of tower plates of the absorption tower is 18-25; Preferably, the number of tower plates of the methanol extraction tower is 28-32; Preferably, the number of tower plates of the isobutylene light component removal tower is 44-48; Preferably, the number of tower plates of the isobutylene heavy component removal tower is 40-43.

4. A process for the cleavage of methyl tert-butyl ether to produce isobutene and methanol, characterized in that, The method comprises the following steps: (1) the raw material containing methyl tert-butyl ether is fed into a methyl tert-butyl ether vaporization refining tower for refining treatment to obtain refined methyl tert-butyl ether; (2) the refined methyl tert-butyl ether in step (1) is fed into a reactor for cracking reaction under the action of a catalyst to obtain a mixed gas of isobutene and methanol; (3) the mixed gas in step (2) is subjected to separation treatment to obtain isobutene and methanol; the catalyst in step (2) comprises a carrier, an active component and an auxiliary agent supported on the carrier; the carrier comprises silica and alumina; the active component comprises phosphotungstic acid and / or a combination of phosphotungstic acid and phosphomolybdic acid; the auxiliary agent comprises any one or a combination of at least two of V, Ce or Cs.

5. The method of claim 4, wherein, the mass ratio of the active component to the carrier is 1:(3-4); preferably, the mass ratio of the silica to the alumina is (5-6):1; preferably, the mass ratio of the phosphomolybdic acid to the phosphotungstic acid is (0-1):8; preferably, the content of V in the catalyst accounts for (0.02-0.05)% of the total mass of the catalyst, calculated based on V2O5; preferably, the content of Ce in the catalyst accounts for (0.05-0.08)% of the total mass of the catalyst, calculated based on CeO2; preferably, the content of Cs in the catalyst accounts for (0.16-0.19)% of the total mass of the catalyst, calculated based on Cs.

6. The method according to claim 4 or 5, characterized in that, the methyl tert-butyl ether vaporization refining tower comprises a first tower section and a second tower section from bottom to top; preferably, the methyl tert-butyl ether vaporization refining tower is a variable-diameter tower; preferably, the tower diameter of the second tower section is smaller than that of the first tower section; preferably, the ratio of the tower diameter of the second tower section to that of the first tower section is (0.6-0.8):1; preferably, the raw material is fed into the methyl tert-butyl ether vaporization refining tower from the 24th to 26th tray of the first tower section; preferably, the refined methyl tert-butyl ether is collected from the 15th to 17th tray of the first tower section; preferably, the feeding temperature of the raw material is 95-100℃; preferably, the tower top pressure of the methyl tert-butyl ether vaporization refining tower is 0.3-0.35 MPa; preferably, the tower top temperature of the methyl tert-butyl ether vaporization refining tower is 69-80℃; preferably, the methyl tert-butyl ether vaporization refining tower is in full liquid reflux at the tower top; preferably, the temperature of the refined methyl tert-butyl ether is 105-110℃; preferably, the temperature of the methyl tert-butyl ether vaporization refining tower at the tower bottom is 118-125℃; preferably, the temperature of the reactor is 180-280℃; preferably, the pressure of the reactor is 0.1-0.2 MPa; Preferably, the space velocity of the reactor is between 0.3 and 1.0 h -1 .

7. The method according to any one of claims 4-6, characterized in that, the separation treatment comprises: S3.1, the mixed gas in step (2) is subjected to cooling treatment by a cooling tower to obtain a gas phase containing isobutene and a liquid phase containing methanol; S3.2, the liquid phase containing methanol is subjected to first rectification treatment by a methanol recovery tower to obtain crude methanol and an aqueous phase, wherein a first part of the aqueous phase is returned to a methanol extraction tower for recycling as an extractant, a second part of the aqueous phase is discharged, and the crude methanol is subjected to second rectification treatment by a methanol refining tower to obtain methanol; S3.3, the isobutene-containing gas phase enters an absorption tower for absorption treatment, to obtain a demethanized isobutene gas phase and an absorption rich liquid, the absorption rich liquid is returned to the cooling tower to be used as a cooling absorption liquid, the demethanized isobutene gas phase enters a compressor for compression treatment, to obtain an isobutene-containing liquid phase, the isobutene-containing liquid phase enters a methanol extraction tower for extraction treatment, to obtain crude isobutene and a treated extractant, the crude isobutene is subjected to first purification treatment and second purification treatment in turn through an isobutene light-removing tower and an isobutene heavy-removing tower, to obtain isobutene, and the treated extractant is returned to the absorption tower to be used as an absorbent.

8. The method of claim 7, wherein, The extractant used in the extraction treatment process comprises desalted water and the first part of the aqueous phase; Preferably, the volume ratio of the first part of the aqueous phase to the desalted water is (9-10):1; Preferably, the volume ratio of the first part of the aqueous phase to the second part of the aqueous phase is (7.7-8.5):1; Preferably, the mass percentage of methanol in the first part of the aqueous phase used as the extractant is 0.12-0.16%; Preferably, the mass percentage of methanol in the treated extractant used as the absorbent is 1.6-1.8%; Preferably, the mass percentage of methanol in the absorption rich liquid used as the cooling absorption liquid is 16-18%.

9. The method according to claim 7 or 8, characterized in that, The tower top pressure of the cooling tower is 0.04-0.06 MPa; Preferably, the tower top temperature of the cooling tower is 54-56℃; Preferably, the cooling tower has a liquid-gas ratio of 8 to 12 L / m 3 ; Preferably, the tower top pressure of the methanol recovery tower is 0.03-0.04 MPa; Preferably, the tower top temperature of the methanol recovery tower is 70-75℃; Preferably, the tower bottom pressure of the methanol recovery tower is 0.05-0.07 MPa; Preferably, the tower bottom temperature of the methanol recovery tower is 110-115℃; Preferably, the tower top reflux ratio of the methanol recovery tower is 1.5-2.0; Preferably, the tower top pressure of the methanol refining tower is 0.34-0.36 MPa; Preferably, the tower top temperature of the methanol refining tower is 71-73℃; Preferably, the tower bottom pressure of the methanol refining tower is 0.38-0.4 MPa; Preferably, the tower bottom temperature of the methanol refining tower is 92-95℃; Preferably, the tower top reflux ratio of the methanol refining tower is 3-5; Preferably, the tower top pressure of the absorption tower is 0.02-0.03 MPa; Preferably, the tower top temperature of the absorption tower is 38-40℃; Preferably, the liquid-gas ratio of the absorption column is between 6 and 8 L / m 3 ; Preferably, the tower top pressure of the methanol extraction tower is 0.45-0.48 MPa; Preferably, the tower top temperature of the methanol extraction tower is 38-40℃; Preferably, the tower bottom pressure of the methanol extraction tower is 0.76-0.8 MPa; Preferably, the tower bottom temperature of the methanol extraction tower is 39-41℃; Preferably, the mass ratio of the extractant used in the extraction treatment process to the isobutene-containing liquid phase is (0.8-0.85):1; Preferably, the tower top pressure of the isobutene light-removing tower is 0.75-0.78 MPa; Preferably, the tower top temperature of the isobutene light-removing tower is 50-52℃; Preferably, the column bottom pressure of the isobutylene light-removing column is 0.79-0.8 MPa; Preferably, the column bottom temperature of the isobutylene light-removing column is 66-68℃; Preferably, the column top liquid phase of the isobutylene light-removing column is total reflux; Preferably, the column top pressure of the isobutylene heavy-removing column is 0.59-0.61 MPa; Preferably, the column top temperature of the isobutylene heavy-removing column is 55-56.5℃; Preferably, the column bottom pressure of the isobutylene heavy-removing column is 0.62-0.64 MPa; Preferably, the column bottom temperature of the isobutylene heavy-removing column is 90-93℃; Preferably, the column top reflux ratio of the isobutylene heavy-removing column is 1.7-2.

0.

10. The method according to any one of claims 5 to 9, characterized in that, The method comprises the following steps: (1) feeding a raw material containing methyl tert-butyl ether into a variable-diameter methyl tert-butyl ether vaporization refining column for refining treatment to obtain refined methyl tert-butyl ether; (2) feeding the refined methyl tert-butyl ether in step (1) into a reactor for cracking reaction under the action of a catalyst to obtain a mixed gas of isobutylene and methanol; wherein the catalyst comprises a carrier and active components and an auxiliary agent supported on the carrier, the carrier comprises silica and alumina in a mass ratio of (5-6):1, the active components comprise phosphomolybdic acid and phosphotungstic acid in a mass ratio of (0-1):8, and the auxiliary agent comprises any one or a combination of at least two of V, Ce or Cs; (3) obtaining a gas phase containing isobutylene and a liquid phase containing methanol after the mixed gas in step (2) is subjected to cooling treatment by a cooling tower; (4) subjecting the liquid phase containing methanol to first rectification treatment by a methanol recovery column to obtain crude methanol and an aqueous phase, wherein a first part of the aqueous phase is returned to a methanol extraction column for recycling use, a second part of the aqueous phase is discharged, and the crude methanol is subjected to second rectification treatment by a methanol refining column to obtain methanol; (5) feeding the gas phase containing isobutylene into an absorption tower for absorption treatment to obtain a post-methanol-removal isobutylene gas phase and an absorption rich solution, returning the absorption rich solution to the cooling tower for recycling use as a cooling absorption liquid, feeding the post-methanol-removal isobutylene gas phase into a compressor for compression treatment to obtain a liquid phase containing isobutylene, feeding the liquid phase containing isobutylene into a methanol extraction column for extraction treatment to obtain crude isobutylene and a treated extraction agent, and sequentially subjecting the crude isobutylene to first purification treatment by an isobutylene light-removing column and second purification treatment by an isobutylene heavy-removing column to obtain isobutylene, and returning the treated extraction agent to the absorption tower for recycling use as an absorbent.

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