Method for purifying isopropyl alcohol

Abstract

Provided are a method of and a device for purifying isopropyl alcohol. Water may be effectively removed from a feed including water and isopropyl alcohol while consuming a minimum amount of energy, and therefore, a high-purity isopropyl alcohol may be obtained.

Claims

1. A method for purifying isopropyl alcohol, comprising: removing water by providing a feed including isopropyl alcohol and water to a membrane system to obtain a feed having a water content adjusted to 1,200 ppm or less; and performing purification by providing the feed having the water content adjusted to 1,200 ppm or less to a divided wall column to obtain a discharged product including purified isopropyl alcohol and having a water content of 150 ppm or less, wherein the divided wall column is divided into a feed inflow region, a top region, a bottom region and a product outflow region, and the product outflow region is divided into an upper product outflow region and a lower product outflow region, wherein the discharged product including the purified isopropyl alcohol and having a water content of 150 ppm or less is discharged from the lower product outflow region of the divided wall column, and wherein the discharged product including the purified isopropyl alcohol and having a water content of 150 ppm or less is obtained at a location of 50 to 90% of plates among a number of theoretical plates calculated based on a top of the divided wall column.

2. The method according to claim 1, wherein the membrane system is a pervaporation system or a vapor permeation system.

3. The method according to claim 1, wherein the feed provided to the membrane system has a water content of 1,200 to 5,000 ppm.

4. The method according to claim 1, wherein the temperature of the top region of the divided wall column is adjusted to 40 to 120° C.

5. The method according to claim 1, wherein the pressure of the top region of the divided wall column is adjusted to 0.1 to 10.0 kg/cm.sup.2.

6. The method according to claim 4, wherein the temperature of flow discharged from the lower product outflow region of the divided wall column is 60 to 130° C.

7. The method according to claim 5, wherein the pressure of the lower product outflow region of the divided wall column is 0.3 to 6.0 kg/cm.sup.2.

8. The method according to claim 4, wherein the temperature of the bottom region of the divided wall column is 80 to 160° C.

9. The method according to claim 5, wherein the pressure of the bottom region of the divided wall column is 0.3 to 6.0 kg/cm.sup.2.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 shows a process of the above-described method;

(2) FIG. 2 shows a dehydration means used in the method;

(3) FIG. 3 shows a purification device according to a first example of the present invention; and

(4) FIGS. 4 and 5 show a purification device according to a comparative example of the present invention.

MODE FOR INVENTION

(5) Hereinafter, the present invention will be described in further detail with reference to Examples and Comparative Examples, but the scopes of the method and device are not limited to the following Examples.

Example 1

(6) Isopropyl alcohol (IPA) was purified using a membrane system and a divided wall column (DWC) connected with the membrane system as shown in FIG. 3. Particularly, as the dehydration means, a pervaporation system including a membrane device (HybSi membrane, Pervatech corporation) and a vacuum device was used. As a feed, a liquid feed including 98.6 wt % of IPA, approximately 3,000 ppm of water and approximately 1.1 wt % of other impurities was used. A dehydration process was performed by providing the above-described feed to the membrane system at 90° C. and adjusting a water content of the feed to approximately 1,000 ppm. Afterwards, purification was performed by introducing the feed having a water content of approximately 1,000 ppm, which went through the dehydration process, into a feed inflow region of the DWC, particularly, 20 plates of the DWC having the number of theoretical plates of 90 plates calculated based on a top, and a product material including the IPA was obtained from 60 plates of the DWC having the number of theoretical plates of 90 plates calculated based on the top.

(7) Here, the reflux ratio of a top region of the DWC was adjusted to 57, and operating temperature and pressure of the top region were adjusted to approximately 71° C. and 1.1 kg/cm.sup.2, respectively. In this case, operating temperature and pressure of a lower product outflow region were approximately 98° C. and 1.34 kg/cm.sup.2, respectively, and operating temperature and pressure of the bottom region were approximately 109° C. and 1.37 kg/cm.sup.2, respectively.

(8) In this case, a content of a high boiling point component in the IPA obtained from the lower product outflow region was detected at approximately 32 ppm.

Example 2

(9) Purification was performed by the same method as described in Example 1, except that a reflux ratio of the top region was adjusted to 54.

Example 3

(10) Purification was performed by the same method as described in Example 1, except that a reflux ratio of the top region was adjusted to 46.

Example 4

(11) Purification was performed by the same method as described in Example 1, except that a product including IPA was obtained from 45 plates of the DWC having the number of theoretical plates of 90 plates.

Example 5

(12) Purification was performed by the same method as described in Example 1, except that a product including IPA was obtained from 70 plates of the DWC having the number of theoretical plates of 90 plates.

(13) In this case, a content of a high boiling point component in IPA obtained from the lower product outflow region was detected at approximately 40 ppm.

Example 6

(14) Purification was performed by the same method as described in Example 1, except that operating temperature and pressure of a top region were adjusted to approximately 60° C. and 0.82 kg/cm.sup.2, respectively.

(15) In this case, operating temperature and pressure of a lower product outflow region were approximately 78° C. and 0.98 kg/cm.sup.2, respectively, and operating temperature and pressure of the bottom region were approximately 98° C. and 1.05 kg/cm.sup.2, respectively.

Example 7

(16) Purification was performed by the same method as described in Example 1, except that operating temperature and pressure of a top region were adjusted to approximately 100° C. and 3.2 kg/cm.sup.2, respectively, and a reflux ratio was applied to maintain a water content in IPA finally obtained to be 100 ppm.

(17) In this case, operating temperature and pressure of a lower product outflow region were approximately 115° C. and 3.27 kg/cm.sup.2, respectively, and operating temperature and pressure of a bottom region were approximately 138° C. and 3.4 kg/cm.sup.2, respectively.

Comparative Example 1

(18) A liquid feed including 98.6 wt % of IPA, approximately 3,000 ppm of water, and approximately 1.1 wt % of other impurities was purified in a purification device in which two general columns were connected without a dehydration process as shown in FIG. 4. In this case, top operating temperature and pressure of a first column were adjusted to approximately 76° C. and 1.12 kg/cm.sup.2, respectively, and bottom operating temperature and pressure of the first column were adjusted to approximately 93° C. and 1.54 kg/cm.sup.2, respectively. In addition, top operating temperature and pressure of the second column were adjusted to approximately 83° C. and 1.04 kg/cm.sup.2, respectively, and bottom operating temperature and pressure of the second column were adjusted to approximately 110° C. and 1.18 kg/cm.sup.2, respectively.

Comparative Example 2

(19) As shown in FIG. 5, a process was performed by the same method as described in Example 1, except that a feed passing through a membrane system was purified by being introduced into a purification device in which two general columns were connected, instead of a DWC. In this case, top operating temperature and pressure of a first column were adjusted to approximately 70° C. and 1.12 kg/cm.sup.2, respectively, and bottom operating temperature and pressure of the first column were adjusted to approximately 93° C. and 1.54 kg/cm.sup.2, respectively. In addition, top operating temperature and pressure of a second column were adjusted to approximately 83° C. and 1.04 kg/cm.sup.2, respectively, and bottom operating temperature and pressure of the second column were adjusted to approximately 110° C. and 1.18 kg/cm.sup.2, respectively.

Comparative Example 3

(20) A process was performed by the same method as described in Example 1, except that a liquid feed including 98.6 wt % of IPA, approximately 3,000 ppm of water, and approximately 1.1 wt % of other impurities was introduced directly into a DWC shown in FIG. 2 without a dehydration process. In this case, a reflux ratio of a top region of the DWC was adjusted to 52, operating temperature and pressure of the top region were adjusted to approximately 78° C. and 1.12 kg/cm.sup.2, respectively, and operating temperature and pressure of a bottom region were adjusted to approximately 111° C. and 1.37 kg/cm.sup.2, respectively.

Comparative Example 4

(21) Purification was performed by the same method as described in Example 1, except that a product including IPA was obtained from 35 plates of a DWC having the number of theoretical plates of 90 plates.

Comparative Example 5

(22) Purification was performed by the same method as described in Example 1, except that a product including IPA was obtained from 85 plates of a DWC having the number of theoretical plates of 90 plates.

(23) In this case, a content of a high boiling point component in IPA obtained from a lower product outflow region was detected at approximately 442 ppm.

Comparative Example 6

(24) A process was performed by the same method as described in Example 1, except that a water content in a feed introduced into a purification means after a dehydration means was adjusted to approximately 1,500 ppm.

(25) A total amount of energy and a water content in IPA used in Examples and Comparative Examples are summarized and listed in Tables 1 and 2.

(26) TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Heat duty Condenser 1.9 1.86 1.81 1.9 1.9 1.88 2.16 (Gcal/hr) Reboiler 1.88 1.84 1.8 1.88 1.88 1.84 2.27 Saved amount of energy 1.14 1.18 1.22 1.14 1.14 1.18 0.61 (Gcal/hr) Energy saving rate (%) 38% 39% 40% 38% 38% 39% 25% Water content in IPA (ppm) 89 100 110 110 100 65 100 Saved amount of energy: Saved amount of energy compared to C. Example 1, Energy saving rate: Energy saving rate compared to C. Example 1

(27) TABLE-US-00002 TABLE 2 C. C. C. C. C. C. Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Heat duty Condenser 3.13 2.98 2.02 1.9 1.9 1.9 (Gcal/hr) Reboiler 3.02 2.88 2 1.88 1.88 1.88 Saved amount of energy 0 0.14 1.02 1.14 1.14 1.14 (Gcal/hr) Energy saving rate (%) 0% 5% 34% 38% 38% 38% Water content in IPA (ppm) 100 100 100 142 100 130 Saved amount of energy: Saved amount of energy compared to C. Example 1, Energy saving rate: Energy saving rate compared to C. Example 1 * C. Example: Comparative Example