Industrial process for production of diol
The invention provides an apparatus and process for producing a diol by taking a cyclic carbonate and an aliphatic monohydric alcohol as starting materials, continuously feeding the starting materials into column A, carrying out reactive distillation in column A, continuously withdrawing a low boiling point reaction mixture containing a produced dialkyl carbonate and the aliphatic monohydric alcohol from an upper portion of column A, continuously withdrawing a high boiling point reaction mixture containing a produced diol from a lower portion of column A, continuously feeding the high boiling point reaction mixture into distillation column C, distilling off material having a lower boiling point than that of the diol contained in the high boiling point reaction mixture as a column top component and a side cut component so as to obtain a column bottom component, continuously feeding the column bottom component into column C, and obtaining the diol.
1. In an industrial process for the production of a diol in which a diol is produced by taking a cyclic carbonate and an aliphatic monohydric alcohol as starting materials, continuously feeding the starting materials into a continuous multi-stage distillation column A in which a catalyst is present, carrying out reactive distillation in said column A, continuously withdrawing a low boiling point reaction mixture A T containing a produced dialkyl carbonate and said aliphatic monohydric alcohol from an upper portion of the column A in a gaseous form, continuously withdrawing a high boiling point reaction mixture A B containing a produced diol from a lower portion of the column A in a liquid form, then continuously feeding said high boiling point reaction mixture A B into a continuous multi-stage distillation column C for separating off material having a lower boiling point than that of the diol contained in said high boiling point reaction mixture A B , continuously obtaining the material having a lower boiling point than the diol as a column top component C T and a side cut component C S , and continuously obtaining the diol substantially not containing the material having a lower boiling point than that of the diol as a column bottom component C B , wherein the improvement comprises:
(a) said continuous multi-stage distillation column C comprises a continuous multi-stage distillation column comprising a stripping section having a length L 1 (cm), an inside diameter D 1 (cm) and an internal with a number of stages n 1 thereinside, and an enrichment section having a length L 2 (cm), an inside diameter D 2 (cm) and an internal with a number of stages n 2 thereinside, wherein L 1 , D 1 , n 1 , L 2 , D 2 , and n 2 satisfy the following formulae (1) to (9):
300 ≦L 1 ≦3000 (1)
50 ≦D 1 ≦700 (2)
3 ≦L 1 /D 1 ≦30 (3)
3 ≦n 1 ≦30 (4)
1000 ≦L 2 ≦5000 (5)
50 ≦D 2 ≦500 (6)
10 ≦L 2 /D 2 ≦50 (7)
20 ≦n 2 ≦100 (8) and
D 2 ≦D 1 (9);
(b) the enrichment section of said continuous multi-stage distillation column C has at least one chimney tray installed therein as an internal, said chimney tray having installed therein one or more chimneys each having an opening having a cross-sectional area S (cm 2 ) satisfying the formula (10):
200 ≦S≦ 1000 (10),
and each of the chimneys being such that a height h (cm) from said opening of said chimney to a gas outlet of said chimney satisfies the formula (II):
10 ≦h≦ 80 (11); and
(c) a side cut outlet is connected to a liquid collecting portion of said chimney tray of said continuous multi-stage distillation column C.
2. The process according to claim 1 , wherein an amount produced of the diol is not less than 1 ton/hr.
3. The process according to claim 1 , wherein a plurality (n 3 stages) of trays K are further provided in a lower portion of the internals in a lowermost portion of the stripping section which is in a lower portion of said continuous multi-stage distillation column C, a liquid is continuously withdrawn from an uppermost stage of said trays K, and after heat is given to require for distillation in a reboiler, the heated liquid is returned into the distillation column C from a feeding port provided between the uppermost stage of the trays K and the internal in the lowermost portion of the stripping section, while a remainder of the liquid is fed into a lower tray in order.
4. The process according to claim 3 , wherein each of the trays K is a baffle tray.
5. The process according to claim 3 , wherein an inside diameter D 3 of said continuous multi-stage distillation column C where the trays K are present satisfies D 1 ≦D 3 .
6. The process according to claim 3 , wherein L 1 , D 1 , L 1 /D 1 , n 1 , L 2 , D 2 , L 2 /D 2 , n 2 , and n 3 for said continuous multi-stage distillation column C satisfy respectively 500≦L 1 ≦2000, 70≦D 1 ≦500, 5≦L 1 /D 1 ≦20, 5≦n 1 ≦20, 1500≦L 2 ≦4000, 70≦D 2 ≦400, 15≦L 2 /D 2 ≦40, 30≦n 2 ≦90, and 3≦n 3 ≦20.
7. The process according to claim 1 , wherein the internal in the stripping section of said continuous multi-stage distillation column C and the internal excluding the chimney tray in the enrichment section are trays and/or packings.
8. The process according to claim 7 , wherein the internal in the stripping section of said continuous multi-stage distillation column C is the tray, and the internal excluding the chimney tray in the enrichment section are trays and/or structured packings.
9. The process according to claim 7 , wherein said tray is a sieve tray.
10. The process according to claim 9 , wherein said sieve tray has 100 to 1000 holes/m 2 in a sieve portion thereof, and a cross-sectional area per hole in a range of from 0.5 to 5 cm 2 .
11. The process according to claim 9 , wherein an aperture ratio (a ratio of a total cross-sectional area of the hole in one tray stage to an area of the tray) of said sieve tray in the enrichment section of said continuous multi-stage distillation column C is in a range of from 2 to 15%.
12. The process according to claim 9 , wherein an aperture ratio (a ratio of a total cross-sectional area of the hole in one tray stage to an area of the tray) of said sieve tray in the enrichment section of said continuous multi-stage distillation column C is in a range of from 1.5 to 12%.
13. The process according to claim 1 , wherein an aperture ratio (a ratio of a total cross-sectional area of the opening in the chimney to an area of the chimney tray including a total cross-sectional area of the opening) of said chimney tray is in a range of from 10 to 40%.
14. The process according to claim 1 , wherein said continuous multi-stage distillation column C has a column bottom temperature in a range of from 150 to 250° C.
15. The process according to claim 1 , wherein said continuous multi-stage distillation column C has a column top pressure in a range of from 50000 to 300000 Pa.
16. The process according to claim 1 , wherein said continuous multi-stage distillation column C has a reflux ratio in a range of from 0.3 to 5.
17. The process according to claim 1 , wherein a content of the diol in said column top component C T is not more than 100 ppm.
18. The process according to claim 1 , wherein a content of the diol in said side cut component C S is not more than 0.5% of the diol fed into said continuous multi-stage distillation column C.
19. A continuous multi-stage distillation column being a continuous multi-stage distillation column C for producing a diol, wherein:
(a) said continuous multi-stage distillation column C comprises a distillation column comprising a stripping section having a length L 1 (cm), an inside diameter D 1 (cm) and an internal with a number of stages n 1 thereinside, and an enrichment section having a length L 2 (cm), an inside diameter D 2 (cm) and an internal with a number of stages n 2 thereinside, wherein L 1 , D 1 , n 1 , L 2 , D 2 , and n 2 satisfy the following formulae (1) to (9):
300 ≦L 1 ≦3000 (1)
50 ≦D 1 ≦700 (2)
3 ≦L 1 /D 1 ≦30 (3)
3 ≦n 1 ≦30 (4)
1000 ≦L 2 ≦5000 (5)
50 ≦D 2 ≦500 (6)
10 ≦L 2 /D 2 ≦50 (7)
20 ≦n 2 ≦100 (8) and
D 2 ≦D 1 (9);
(b) the enrichment section of said continuous multi-stage distillation column C has at least one chimney tray installed therein as an internal, the chimney tray having installed therein one or more chimneys each having an opening having a cross-sectional area S (cm 2 ) satisfying the formula (10):
200 ≦S≦ 1000 (10),
and each of the chimneys being such that a height h (cm) from said opening of said chimney to a gas outlet of the chimney satisfies the formula (II):
10 ≦h≦ 80 (11); and
(c) a side cut outlet is connected to a liquid collecting portion of said chimney tray of said continuous multi-stage distillation column C.
20. The continuous multi-stage distillation column according to claim 19 , wherein a plurality (n 3 stages) of trays K are further provided in a lower portion of the internals in a lowermost portion of the stripping section which is in a lower portion of said continuous multi-stage distillation column C.
21. The continuous multi-stage distillation column according to claim 20 , wherein each of the trays K is a baffle tray.
22. The continuous multi-stage distillation column according to claim 20 , wherein an inside diameter D 3 of said column where the trays K are present satisfies D 1 ≦D 3 .
23. The continuous multi-stage distillation column according to claim 19 , wherein L 1 , D 1 , L 1 /D 1 , n 1 , L 2 , D 2 , L 2 /D 2 , n 2 , and n 3 satisfy respectively 500≦L 1 ≦2000, 70≦D 1 ≦500, 5≦L 1 /D 1 ≦20, 5≦n 1 ≦20, 1500≦L 2 ≦4000, 70≦D 2 ≦400, 15≦L 2 /D 2 ≦40, 30≦n 2 ≦90, and 3≦n 3 ≦20.
24. The continuous multi-stage distillation column according to claim 19 , wherein the internal in the stripping section of the stripping section and the internal excluding the chimney tray in the enrichment section are trays and/or packings.
25. The continuous multi-stage distillation column according to claim 24 , wherein the internal in the stripping section is a tray, and the internal excluding the chimney tray in the enrichment section is a tray and/or a structured packing.
26. The continuous multi-stage distillation column according to claim 24 , wherein said tray is a sieve tray.
27. The continuous multi-stage distillation column according to claim 26 , wherein said sieve tray has 100 to 1000 holes/m 2 in a sieve portion thereof, and a cross-sectional area per hole in a range of from 0.5 to 5 cm 2 .
28. The continuous multi-stage distillation column according to claim 26 , wherein an aperture ratio (a ratio of a total cross-sectional area of the hole in one tray stage to an area of the tray) of said sieve tray in the stripping section is in a range of from 2 to 15%.
29. The continuous multi-stage distillation column according to claim 26 , wherein an aperture ratio (a ratio of a total cross-sectional area of the hole in one tray stage to an area of the tray) of said sieve trays in the enrichment section is in a range of from 1.5 to 12%.
30. The continuous multi-stage distillation column according to claim 19 , wherein an aperture ratio (a ratio of a total cross-sectional area of the opening in the chimneys to an area of the chimney tray including a total cross-sectional area of the opening) of said chimney tray is in a range of from 10 to 40%.