A method and device for refining and recovering residues in the process of preparing isobutylene from tert-butyl alcohol

Abstract

The present invention provides a method and device for refining and recovering residues in a process of preparing isobutylene from tert-butyl alcohol. The present invention separates and refines residues in a process of preparing isobutylene from tert-butyl alcohol by a combination of conventional distillation, azeotropic distillation and water washing, and obtains methyl tert-butyl ether and diisobutylene with relatively high purity. By different retention ratios of isopropyl alcohol at the top of a tower and in the bottom of a tower, an equal amount of isopropyl alcohol in the residues in a process of preparing isobutylene from tert-butyl ester is extracted, and accumulation of isopropyl alcohol in a reaction dehydration system of tert-butyl alcohol is avoided, and recycling of more than 95% of tert-butyl alcohol and effective purification of methyl tert-butyl ether are achieved, and waste of high-value products is avoided, thereby improving the atomic economy of the tert-butyl alcohol dehydration process.

Description

Technical Field

[0001] The invention belongs to the technical field of separation and recovery of residual organic matter in organic reactions, and specifically relates to a method and a device for refining and recovering residues in a process for preparing isobutylene with tert-butyl alcohol. Background Art

[0002] In the existing process of preparing polymerization-grade isobutylene from tert-butyl alcohol, since the raw material tert-butyl alcohol usually contains impurities such as methanol, acetone, isopropanol, and isobutanol, MTBE will be generated during the process of catalytic dehydration of tert-butyl alcohol to generate isobutylene; in addition, isobutylene undergoes a superposition reaction to generate diisobutylene, and isobutylene reacts with isopropanol to generate impurities such as tert-butyl isopropyl ether. After separating the product isobutylene, the obtained heavy component (i.e., the residue in the process of preparing isobutylene from tert-butyl alcohol) has a complex composition, and there is azeotropy between the various components. It is difficult to recycle the unreacted tert-butyl alcohol, and it is usually used as a fuel in the prior art, with low added value. Summary of the invention

[0003] It is known that the residue in the process of preparing isobutylene from tert-butyl alcohol, i.e., the heavy components obtained from the bottom of the dehydration tower, contains a large amount of unreacted tert-butyl alcohol and methyl tert-butyl ether. Direct incineration or treatment as waste liquid will cause resource waste and reduce the atomic economy of the process. In addition, because the tert-butyl alcohol raw material contains impurities such as methanol, acetone, isopropanol, and isobutyl alcohol, and there are side reactions such as isobutylene superposition, isobutylene etherification, and dehydration between alcohol molecules in the tert-butyl alcohol reaction dehydration tower, the heavy components extracted from the bottom of the dehydration tower are complex, and it is difficult to separate and purify the heavy components; the heavy components include diisobutylene, the dimerization product of isobutylene, and tert-butyl alcohol, which have an azeotropic reaction, which increases the difficulty of separating and purifying tert-butyl alcohol. In order to improve the above technical problems, the present invention proposes a refining method for separating the heavy components and recovering tert-butyl alcohol and by-products.

[0004] In the present invention, methyl tert-butyl ether is recorded as MTBE, tert-butyl alcohol is recorded as TBA, diisobutylene is recorded as DIB, and isopropyl alcohol is recorded as IPA; the methyl tert-butyl ether recovery tower is recorded as MTBE recovery tower; the tower for separating components such as TBA, DIB, IPA and heavy components such as tert-butyl isopropyl ether and isobutyl tert-butyl ether is recorded as DIB removal tower; and the tower for separating DIB from TBA and IPA by water washing is recorded as DIB recovery tower.

[0005] Specifically, the present invention proposes the following technical solutions:

[0006] A method for refining and recovering residues in a process for preparing isobutylene from tert-butyl alcohol, the method comprising:

[0007] (1) sending the residue in the process of preparing isobutylene from tert-butyl alcohol to an MTBE recovery tower for distillation, obtaining refined methyl tert-butyl ether at the top of the MTBE recovery tower, and obtaining a poor methyl tert-butyl ether component at the bottom of the MTBE recovery tower;

[0008] (2) sending the depleted methyl tert-butyl ether component in step (1) to a de-DIB tower for distillation, obtaining a diisobutylene / tert-butyl alcohol / isopropyl alcohol mixture at the top of the de-DIB tower, and obtaining a depleted diisobutylene / tert-butyl alcohol mixture and tert-butyl isopropyl ether, isobutyl tert-butyl ether and the like in the bottom of the de-DIB tower;

[0009] (3) sending part of the organic wastewater from the reaction dehydration tower as an extractant together with the diisobutylene / tert-butyl alcohol / isopropyl alcohol mixture in step (2) into a DIB recovery tower, the organic wastewater entering the top of the DIB recovery tower, the diisobutylene / tert-butyl alcohol / isopropyl alcohol mixture entering the bottom of the DIB recovery tower, extracting, obtaining refined DIB at the top of the DIB recovery tower, and obtaining a tert-butyl alcohol-rich isopropyl alcohol aqueous solution in the bottom of the DIB recovery tower;

[0010] (4) The tert-butanol-rich and isopropanol aqueous solutions in step (3) are mixed with the tert-butanol entering the reaction dehydration tower before being sent back to the reaction dehydration tower, and the reaction is continued after entering the reaction dehydration tower. The gaseous mixture obtained at the top of the reaction dehydration tower is heated and compressed and then sent to the deweighting tower again. The reactor of the reaction dehydration tower obtains wastewater with an organic content of less than 2000 ppm, and part of the organic wastewater is recycled to the top of the DIB recovery tower as an extractant.

[0011] According to the present invention, the residue in the process of preparing isobutylene from tert-butyl alcohol is the heavy component extracted from the bottom of the dehydration tower in the process of preparing isobutylene from tert-butyl alcohol. Specifically, the process of preparing isobutylene from tert-butyl alcohol comprises the following steps: the tert-butyl alcohol is dehydrated in a reaction dehydration tower, and condensed and separated to obtain a liquid mixture and a gaseous mixture of isobutylene and unreacted tert-butyl alcohol; the liquid mixture is returned to the dehydration reaction tower to continue the reaction; the gaseous mixture is heated and compressed and then sent to the dehydration tower, crude isobutylene is obtained at the top of the dehydration tower, and the residue of the process is obtained in the bottom of the dehydration tower.

[0012] According to the present invention, in step (1), based on the weight of the residue in the existing process for preparing isobutylene from tert-butyl alcohol as 100%, the residue in the process for preparing isobutylene from tert-butyl alcohol comprises the following composition: 30-40wt% of tert-butyl alcohol, 10-14wt% of diisobutylene, 30-40wt% of methyl tert-butyl ether, 5-9wt% of isopropanol, 3-5wt% of tert-butyl isopropyl ether, 5-8wt% of isobutyl tert-butyl ether and 0-2wt% of other components, wherein the other components include water, and / or acetone, and / or isobutyl alcohol.

[0013] According to the present invention, the rich tert-butyl alcohol and isopropanol aqueous solution in the DIB recovery tower are circulated in the tert-butyl alcohol preparation isobutylene process and the refining and recovery system of the process of the present invention. The circulating amount of isopropanol is 5 to 10 times the weight of the isopropanol component in the residue of the conventional tert-butyl alcohol dehydration preparation isobutylene process. Specifically, the circulating isopropanol is transferred to the MTBE recovery tower via step (1), then to the top of the DIB removal tower via step (2), then to the DIB recovery tower via step (3), and then circulated back to the tert-butyl alcohol dehydration preparation isobutylene system via step (4).

[0014] In the present invention, the percentage of the amount of refined MTBE taken out from the top of the MTBE recovery tower to the amount of MTBE in the residue in the existing process for preparing isobutylene from tert-butanol is defined as the MTBE recovery rate. The percentage of the sum of the amount of IPA taken out from the top of the MTBE recovery tower and the amount of IPA taken out from the bottom of the DIB removal tower to the amount of IPA in the residue in the existing process for preparing isobutylene from tert-butanol is defined as the IPA removal rate. The percentage of the amount of tert-butyl isopropyl ether taken out from the bottom of the DIB removal tower to the amount of tert-butyl isopropyl ether in the residue in the existing process for preparing isobutylene from tert-butanol is defined as the tert-butyl isopropyl ether removal rate. The percentage of the amount of isobutyl tert-butyl ether taken out from the bottom of the DIB removal tower to the amount of isobutyl tert-butyl ether in the residue in the existing process for preparing isobutylene from tert-butanol is defined as the tert-butyl isopropyl ether removal rate. The percentage of the amount of DIB extracted from the top of the DIB recovery tower and the amount of DIB in the residue in the existing process for preparing isobutylene with tert-butyl alcohol is defined as the DIB recovery rate; the percentage of the amount of TBA extracted from the bottom of the DIB recovery tower and the sum of the amount of TBA in the residue in the existing process for preparing isobutylene with tert-butyl alcohol and the amount of TBA in the organic wastewater entering the DIB recovery tower is defined as the TBA recovery rate.

[0015] According to the present invention, in step (1), the MTBE recovery rate is ≥90%; preferably, the recovery rate is ≥95%; more preferably, the recovery rate is ≥98%. That is, in step (1), the MTBE mass concentration in the overhead product of the MTBE recovery tower is ≥90%; preferably, ≥95%; more preferably, ≥99%.

[0016] According to the present invention, in step (1), the top pressure of the MTBE recovery tower is 110-130 KPa, exemplarily 110, 115, 120, 125 or 130 KPa; the top temperature is 50-70°C, exemplarily 55-65°C, for example 55, 58, 60, 63 or 65; the bottom pressure is 140-160 KPa, exemplarily 140, 145, 150, 155 or 160 KPa; the bottom temperature is 85-100°C, exemplarily 88-95°C, for example 88, 90, 92 or 90°C; the reflux ratio of the tower is 5-15, exemplarily 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15.

[0017] According to the present invention, in steps (1) and (2), the IPA removal rate is ≥94%, and the optimized IPA removal rate is ≥98%; more preferably, the IPA removal rate is ≥99.5%. The tert-butyl isopropyl ether removal rate is ≥97%, and the optimized tert-butyl isopropyl ether removal rate is ≥99%. The isobutyl tert-butyl ether removal rate is ≥99%.

[0018] According to the present invention, in step (2), the top pressure of the DIB removal tower is 110-130 kPa, exemplarily 110, 115, 120, 125 or 130 kPa; the top temperature is 75-90° C., exemplarily 80-85° C., for example 80, 82, 84 or 85° C.; the bottom temperature is 85-105° C., exemplarily 90-100° C., for example 90, 95, 96, 98 or 100° C.; the reflux ratio of the tower is 1-10, exemplarily 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10.

[0019] According to the present invention, in step (3), the DIB recovery tower adopts extraction separation, and the extractant is water with an organic matter content not higher than 2000 ppm.

[0020] According to the present invention, in step (3), the mass ratio of the extractant to the diisobutylene / tert-butyl alcohol / isopropanol mixture is (0.5-5):1, for example, it can be 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, preferably (1.2-3):1.

[0021] According to the present invention, in step (3), the DIB recovery rate is ≥99%. The purity of DIB at the top of the DIB recovery tower is ≥90%, and the DIB purity is ≥96% in an optimized manner; more preferably, the DIB purity is ≥99%. The recovery rate of TBA is ≥95%.

[0022] According to the present invention, in step (4), the organic-containing wastewater is returned to the reaction dehydration tower along with the tert-butyl alcohol-rich and isopropanol aqueous solution in the bottom of the DIB recovery tower, discharged from the bottom of the reaction dehydration tower, and then circulated back to the top of the DIB recovery tower in step (3) as an extractant.

[0023] The present invention also provides the following technical solutions:

[0024] A device for realizing the method for refining and recovering residues in the process of preparing isobutylene with tert-butyl alcohol, the device comprises an MTBE recovery tower, a DIB removal tower and a DIB recovery tower which are connected in sequence.

[0025] According to the present invention, the MTBE recovery tower, the DIB removal tower and the DIB recovery tower can all be plate towers or packed towers.

[0026] According to the present invention, the number of plates of the MTBE recovery tower is 40-56, preferably 48; the number of feed plates is 24-32, preferably 28.

[0027] According to the present invention, the number of plates of the DIB removal tower is 45-70, preferably 58; the number of feed plates is 34-43, preferably 38.

[0028] According to the present invention, the number of plates of the DIB recovery tower is 4-8, preferably 5; the number of plates for feeding the extractant is 1, and the feeding position of the diisobutylene-depleted / isopropanol heavy component is the bottom of the tower.

[0029] According to the present invention, the top of the MTBE recovery tower obtains refined methyl tert-butyl ether, and the bottom of the MTBE recovery tower obtains a depleted methyl tert-butyl ether heavy component; the depleted methyl tert-butyl ether heavy component is sent to a DIB removal tower.

[0030] According to the present invention, the diisobutylene / tert-butyl alcohol / isopropanol mixture obtained at the top of the DIB removal tower is sent to the kettle of the DIB recovery tower.

[0031] According to the present invention, the DIB recovery tower is connected to a reaction dehydration tower in the process of preparing isobutylene from tert-butyl alcohol.

[0032] According to the present invention, part of the wastewater with an organic matter content of less than 2000 ppm obtained from the reactor of the reaction dehydration tower is recycled to the top of the DIB recovery tower as an extractant.

[0033] According to the present invention, the rich tert-butanol and isopropanol aqueous solution obtained in the kettle of the DIB recovery tower are sent back to the reaction dehydration tower to continue the reaction.

[0034] According to the present invention, the reaction dehydration tower in the process of preparing isobutylene with tert-butyl alcohol is further connected to a deweighting tower, and the kettle of the deweighting tower is connected to an MTBE recovery tower.

[0035] According to the present invention, the tert-butanol-rich isopropanol aqueous solution in step (3) is sent back to the reaction dehydration tower to continue the reaction, and the gaseous mixture obtained at the top of the reaction dehydration tower is heated and compressed and then sent to the deweighting tower again.

[0036] Beneficial Effects

[0037] (1) The present invention separates and refines the residue in the process of preparing isobutylene from tert-butyl alcohol by a combination of conventional distillation, azeotropic distillation and water washing, thereby obtaining methyl tert-butyl ether and diisobutylene with relatively high purity, recovering tert-butyl alcohol, avoiding the waste of high-value products, and improving the atomic economy of the tert-butyl alcohol dehydration process.

[0038] (2) The present invention first separates high-purity methyl tert-butyl ether through conventional distillation; through different retention ratios of isopropanol in the tower top and tower bottom, an equal amount of isopropanol as the raw material for preparing isobutylene residue with tert-butyl alcohol is extracted, thereby avoiding the accumulation of isopropanol in the tert-butyl alcohol reaction dehydration system, achieving the recycling of more than 90% of tert-butyl alcohol and the effective purification of methyl tert-butyl ether. In addition, part of the organic wastewater in the tower bottom of the reaction dehydration tower can be used as the extractant of the DIB recovery tower, without the need to introduce additional fresh water. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The present invention is a simplified flow chart of the refining and recovery method; wherein, S1-MTBE recovery tower feed; S2-MTBE recovery tower top material; S3-DIB removal tower bottom material; S4-extractant (containing organic wastewater); S5-DIB recovery tower top material; S6-DIB recovery tower bottom material.

[0040] Figure 2 The figure is a simplified flow chart of the separation of the isobutylene refining kettle residue in Example 1; wherein: 1-MTBE recovery tower; 2-DIB removal tower; 3-DIB recovery tower. DETAILED DESCRIPTION

[0041] The technical scheme of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0042] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0043] In the following embodiments, the residual liquid of tert-butanol dehydration to prepare isobutylene is the bottom residue extracted from the bottom of the dehydration tower in the following process: fresh tert-butanol and DIB recovery tower bottom rich tert-butanol aqueous solution are mixed and reacted in a reaction dehydration tower, and the materials in the tower are distilled to the top of the tower to form a gaseous mixture, which is heated and compressed and then sent to the dehydration tower, and crude isobutylene is obtained at the top of the dehydration tower, and the residual liquid is obtained in the bottom of the tower.

[0044] Example 1

[0045] The composition of the residual liquid from the process of dehydrating fresh tert-butanol to produce isobutylene is shown in Table 1. After the existing process of dehydrating tert-butanol to produce isobutylene is connected with the process of the present invention, the residual liquid after mixing fresh tert-butanol with the tert-butanol-rich aqueous solution in the bottom of the DIB recovery tower of the present invention, that is, the material composition of the MTBE recovery tower feed of this embodiment is shown in Table 2.

[0046] (1) The residual liquid of this embodiment is first sent to MTBE recovery tower 1, and the refined MTBE recovered from the top of MTBE recovery tower 1 is taken out, and the lean MTBE component (i.e., bottom stream) taken out from the bottom of MTBE recovery tower 1 is sent to de-DIB tower 2. MTBE recovery tower 1 adopts a plate tower with 48 plates, 28 feed plates, 12 reflux ratio, 60.2°C top temperature, 120KPa top pressure, 90.3°C bottom temperature, and 150KPa bottom pressure. The purity of MTBE at the top of MTBE recovery tower 1 is 99.12%, and the MTBE recovery rate is 99.96%. The composition of the top and bottom streams of MTBE recovery tower 1 is shown in Table 2.

[0047] (2) The bottom stream of MTBE recovery tower 1 is sent to de-DIB tower 2, and a diisobutylene / tert-butyl alcohol / isopropanol mixture is produced from the top of de-DIB tower 2, and a diisobutylene-poor / isopropanol heavy component is produced from the bottom of de-DIB tower 2. The diisobutylene / tert-butyl alcohol / isopropanol mixture is sent to DIB recovery tower 3. De-DIB tower 2 adopts a plate tower with 58 plates, 38 feed plates, reflux ratio 3, top temperature 84.6°C, top pressure 120KPa, bottom temperature 95.6°C, and bottom pressure 160KPa. In this embodiment, the IPA removal rate is 99.9%, the tert-butyl isopropyl ether removal rate is 99.5%, and the isobutyl tert-butyl ether removal rate is 99.9%. The composition of the top and bottom streams of de-DIB tower 2 is shown in Table 2.

[0048] (3) The diisobutylene / tert-butyl alcohol / isopropanol mixture and the organic wastewater from the tert-butyl alcohol reaction dehydration tower are sent to the DIB recovery tower 3, the diisobutylene / tert-butyl alcohol / isopropanol mixture is sent to the bottom of the DIB recovery tower 3, and the organic wastewater is sent to the top of the DIB recovery tower 3. The material composition of the organic wastewater is shown in Table 2. The wastewater inlet temperature is 40°C, and the mass ratio of the wastewater to the diisobutylene / tert-butyl alcohol / isopropanol mixture is 1.39:1. After extraction, the refined DIB is extracted from the top of the DIB recovery tower 3, and the rich tert-butyl alcohol / isopropanol aqueous solution is extracted from the bottom of the DIB recovery tower 3. The DIB recovery tower 3 adopts a plate tower with 5 plates, a top pressure of 200 KPa, and a bottom pressure of 300 KPa. The purity of DIB at the top of the DIB recovery tower is 99.58%, and the DIB recovery rate is 99.9%; the TBA recovery rate in the bottom of the DIB recovery tower is 96.89%. The composition of the top and bottom logistics of DIB recovery tower 3 is shown in Table 2.

[0049] Table 1 Composition of residues from fresh tert-butyl alcohol dehydration to isobutylene

[0050] composition Isobutylene Tert-Butanol acetone Diisobutylene Methyl tert-butyl ether Flow rate kg / h 0 212.5 1.56 75 225 composition Isopropyl alcohol Isobutanol Tert-Butyl Isopropyl Ether Isobutyl tert-butyl ether water Flow rate kg / h 43.75 1.56 26.88 38.75 0

[0051] Table 2 Composition of each tower logistics in Example 1

[0052]

[0053] Table 2 (Continued) Composition of each tower logistics in Example 1

[0054]

[0055] Example 2

[0056] In Example 2, except that the reflux ratio of the DIB removal tower 2 is 2, the feed composition, temperature, pressure and other parameters of the MTBE recovery tower 1, and the operating conditions of the MTBE recovery tower 1 and the DIB recovery tower 3 are the same as those in Example 1.

[0057] In this embodiment, the MTBE purity at the top of MTBE recovery tower 1 is 99.12%, and the MTBE recovery rate is 99.96%. The IPA removal rate is 95.1%, the tert-butyl isopropyl ether removal rate is 97.8%, and the isobutyl tert-butyl ether removal rate is 99.9%. The DIB purity at the top of DIB recovery tower 3 is 99%, the DIB recovery rate is 99.9%, and the TBA recovery rate in the DIB recovery tower bottom is 96.1%. The logistics data of each tower are shown in Table 3.

[0058] Table 3 Composition of each tower logistics in Example 2

[0059]

[0060] Table 3 (Continued) Composition of each tower logistics in Example 2

[0061]

[0062] Example 3

[0063] In Example 3, except that the mass ratio of the extractant to the diisobutylene-depleted / isopropanol heavy component in the DIB recovery tower 3 is 0.5:1, other conditions are the same as those in Example 1.

[0064] In this embodiment, the MTBE purity at the top of MTBE recovery tower 1 is 99.12%, and the MTBE recovery rate is 99.96%. The IPA removal rate of the DIB removal tower is 99.9%, the tert-butyl isopropyl ether removal rate is 97.8%, and the isobutyl tert-butyl ether removal rate is 99.9%. The DIB purity at the top of the DIB recovery tower is 97.6%, and the DIB recovery rate is 99.9%; the TBA recovery rate at the bottom of the DIB recovery tower is 96.2%. The logistics data of each tower are shown in Table 4.

[0065] Table 4 Composition of each tower logistics in Example 3

[0066]

[0067] Table 4 (Continued) Composition of each tower logistics in Example 3

[0068]

[0069] Example 4

[0070] (1) The residual liquid of this embodiment is first sent to MTBE recovery tower 1, and the refined MTBE recovered from the top of MTBE recovery tower 1 is taken out, and the lean MTBE component (i.e., bottom stream) taken out from the bottom of MTBE recovery tower 1 is sent to de-DIB tower 2. MTBE recovery tower 1 adopts a plate tower with 48 plates, 28 feed plates, reflux ratio of 9.5, top temperature of 60.8°C, top pressure of 120KPa, bottom temperature of 90°C, and bottom pressure of 150KPa. The purity of MTBE at the top of MTBE recovery tower 1 is 96.1%, and the recovery rate of MTBE is 96.9%. The composition of the top and bottom streams of MTBE recovery tower 1 is shown in Table 5.

[0071] (2) The bottom stream of MTBE recovery tower 1 is sent to de-DIB tower 2, and a diisobutylene / tert-butyl alcohol / isopropanol mixture is produced from the top of de-DIB tower 2, and a diisobutylene / isopropanol heavy component is produced from the bottom of de-DIB tower 2. The diisobutylene / tert-butyl alcohol / isopropanol mixture is sent to DIB recovery tower 3. De-DIB tower 2 adopts a plate tower with 58 plates, 38 feed plates, reflux ratio 3, top temperature 84.4°C, top pressure 120KPa, bottom temperature 96°C, and bottom pressure 160KPa. In this embodiment, the IPA removal rate is 94.8%, the tert-butyl isopropyl ether removal rate is 99.6%, and the isobutyl tert-butyl ether removal rate is 99.9%. The composition of the top and bottom streams of de-DIB tower 2 is shown in Table 5.

[0072] Table 5 Composition of each tower logistics in Example 4

[0073]

[0074] (3) The diisobutylene / tert-butyl alcohol / isopropanol mixture and the organic wastewater from the tert-butyl alcohol reaction dehydration tower are sent to the DIB recovery tower 3, the diisobutylene / tert-butyl alcohol / isopropanol mixture is sent to the bottom of the DIB recovery tower 3, and the organic wastewater is sent to the top of the DIB recovery tower 3. The wastewater inlet temperature is 40°C, and the mass ratio of wastewater to diisobutylene / tert-butyl alcohol / isopropanol mixture is 1.37:1. After extraction, the refined DIB is extracted from the top of the DIB recovery tower 3, and the rich tert-butyl alcohol / isopropanol aqueous solution is extracted from the bottom of the DIB recovery tower 3. The DIB recovery tower 3 adopts a plate tower with 5 plates, a top pressure of 200 KPa, and a bottom pressure of 300 KPa. The purity of DIB at the top of the DIB recovery tower is 91.2%, and the DIB recovery rate is 99.4%; the TBA recovery rate in the bottom of the DIB recovery tower is 97.3%. The composition of the top / bottom flow of the DIB recovery tower 3 is shown in Table 5.

[0075] Table 5 (Continued) Composition of each tower logistics in Example 4

[0076]

[0077] As can be seen from the data of Examples 1-4, the method of the present invention can recover methyl tert-butyl ether, diisobutylene and tert-butyl alcohol in the residual components of the isobutylene dehydration tower kettle by dehydrating tert-butyl alcohol, thereby avoiding material loss. The recovered methyl tert-butyl ether and diisobutylene can be used as refined products, and the recovered tert-butyl alcohol can be repeatedly involved in the tert-butyl alcohol dehydration reaction, thereby improving the utilization rate of the tert-butyl alcohol. The DIB recovery tower uses organic wastewater from part of the tert-butyl alcohol dehydration reaction tower kettle as an extractant, thereby avoiding the introduction of new materials, and the tert-butyl alcohol in the wastewater can also be further recovered.

[0078] The above is an explanation of the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for refining and recovering residues in a process for preparing isobutylene from tert-butyl alcohol, characterized in that: The method comprises: (1) The residue in the process of preparing isobutylene from tert-butyl alcohol is sent to the MTBE recovery tower for distillation, and the refined methyl tert-butyl ether is obtained at the top of the MTBE recovery tower, and the lean methyl tert-butyl ether component is obtained at the bottom of the MTBE recovery tower; (2) sending the depleted methyl tert-butyl ether component in step (1) to a de-DIB tower for distillation to obtain a diisobutylene / tert-butyl alcohol / isopropanol mixture at the top of the de-DIB tower and a depleted diisobutylene / tert-butyl alcohol component in the bottom of the de-DIB tower; (3) sending part of the organic wastewater from the reaction dehydration tower as an extractant together with the diisobutylene / tert-butyl alcohol / isopropyl alcohol mixture in step (2) into a DIB recovery tower, the organic wastewater entering the top of the DIB recovery tower, the diisobutylene / tert-butyl alcohol / isopropyl alcohol mixture entering the bottom of the DIB recovery tower, extracting, obtaining refined DIB at the top of the DIB recovery tower, and obtaining a tert-butyl alcohol-rich isopropyl alcohol aqueous solution in the bottom of the DIB recovery tower; (4) The tert-butyl alcohol and isopropanol aqueous solution in step (3) are sent back to the reaction dehydration tower to continue the reaction. The gaseous mixture obtained at the top of the reaction dehydration tower is heated and compressed and then sent to the deweighting tower again. The bottom of the reaction dehydration tower obtains wastewater with an organic content of less than 2000 ppm, and part of the organic wastewater is recycled to the top of the DIB recovery tower as an extractant; In step (1), the residue in the process of preparing isobutylene from tert-butyl alcohol is the heavy component obtained from the bottom of the deweighting tower; the residue in the process of preparing isobutylene from tert-butyl alcohol comprises the following composition: 30-40wt% of tert-butyl alcohol, 10-14wt% of diisobutylene, 30-40wt% of methyl tert-butyl ether, 5-9wt% of isopropanol, 3-5wt% of tert-butyl isopropyl ether, 5-8wt% of isobutyl tert-butyl ether and 0-2wt% of other components, and the other components include water, and / or acetone, and / or isobutyl alcohol.

2. The method according to claim 1, characterized in that The method also includes circulating isopropanol in the tert-butyl alcohol dehydration system to produce isobutylene, wherein the circulating isopropanol is transferred to the bottom of the MTBE recovery tower through step (1), then transferred to the top of the DIB removal tower through step (2), then transferred to the bottom of the DIB recovery tower through step (3), and then transferred back to the tert-butyl alcohol dehydration system to produce isobutylene through step (4).

3. The method according to claim 1, characterized in that In step (1), the top pressure of the MTBE recovery tower is 110-130 KPa, the top temperature is 50-70°C, the bottom pressure is 140-160 KPa, the bottom temperature is 85-100°C, and the reflux ratio of the tower is 5-15; the mass concentration of MTBE in the top extract of the MTBE recovery tower is ≥90-99%.

4. The method according to claim 1, characterized in that In step (2), the top pressure of the DIB removal tower is 110-130 kPa, the top temperature is 75-90° C., the bottom temperature is 85-105° C., and the reflux ratio of the tower is 1-10.

5. The method according to claim 1, characterized in that In step (3), the extractant is water with an organic matter content not higher than 2000 ppm, and the mass ratio of the extractant to the diisobutylene / tert-butyl alcohol / isopropanol mixture is (0.5-5):

1.

6. The method according to any one of claims 1 to 5, characterized in that: The method is carried out in the following device, which comprises an MTBE recovery tower, a DIB removal tower and a DIB recovery tower which are connected in sequence.

7. The method according to claim 6, characterized in that The number of plates of the MTBE recovery tower is 40-56; the number of feed plates is 24-32; And / or, the number of plates of the DIB removal tower is 45-70; the number of feed plates is 34-43; And / or, the number of plates of the DIB recovery tower is 4-8; the number of plates for feeding the extractant is 1, and the feeding position of the diisobutylene-depleted / isopropanol heavy component is the bottom of the tower.

8. The method according to claim 7, characterized in that The top of the MTBE recovery tower obtains refined methyl tert-butyl ether, and the bottom of the MTBE recovery tower obtains a lean methyl tert-butyl ether component; the lean methyl tert-butyl ether recombinant component is sent to a DIB removal tower; And / or, the diisobutylene / tert-butyl alcohol / isopropanol mixture obtained at the top of the DIB removal tower is sent to the kettle of the DIB recovery tower.

9. The method according to claim 6, characterized in that The DIB recovery tower is connected to a reaction dehydration tower in the process of preparing isobutylene from tert-butyl alcohol; Part of the wastewater with an organic matter content of less than 2000 ppm obtained in the reactor of the reaction dehydration tower is recycled to the top of the DIB recovery tower as an extractant; and / or the tert-butanol-rich and isopropanol aqueous solutions obtained in the reactor of the DIB recovery tower are sent back to the reaction dehydration tower to continue the reaction.

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