Industrial process for production of an aromatic carbonate
It is an object of the present invention to provide, for the case of continuously producing aromatic carbonates containing a diaryl carbonate as a main product by taking an alkyl aryl carbonate as a starting material, which is obtainable through a transesterification reaction between a dialkyl carbonate and an aromatic monohydroxy compound, using a continuous multi-stage distillation column in which a catalyst is present, and continuously feeding the starting material into the continuous multi-stage distillation column, a specific process that enables the diaryl carbonate to be produced with high selectivity and high productivity stably for a prolonged period of time on an industrial scale of not less than 1 ton per hour. Although there have been various proposals regarding processes for the production of aromatic carbonates by means of a reactive distillation method, these have all been on a small scale and short operating time laboratory level, and there have been no disclosures whatsoever on a specific process or apparatus enabling mass production on an industrial scale. According to the present invention, there is provided a specified continuous multi-stage distillation column, and there is also provided a specific process that enables a diaryl carbonate to be produced with high selectivity and high productivity stably for a prolonged period of time on an industrial scale of not less than 1 ton per hour from an alkyl aryl carbonate.
1. A process for the production of an aromatic carbonate containing a diaryl carbonate as a main product from a strating material comprising an alkyl aryl carbonate, which is obtainable through a transesterification reaction between a dialkyl carbonate and an aromatic monohydroxy compound, which comprises the steps of:
(i) continuously feeding said starting material into a continuous multi-stage distillation column in which a catalyst is present;
(ii) carrying out the reaction in the column to produce a dialkyl carbonate and the diaryl carbonate;
(iii) continuously withdrawing a low boiling point reaction mixture containing said produced the dialkyl carbonate from an upper portion of the column in a gaseous form and continuously withdrawing a high boiling point reaction mixture containing the diaryl carbonate from a lower portion of the column in a liquid form, wherein said continuous multi-stage distillation column comprises a structure having a pair of end plates above and below a cylindrical trunk portion having a length L (cm) and an inside diameter D (cm), and having an internal with a number of stages n thereinside, and comprises a gas outlet having an inside diameter d 1 (cm) at the top of the column or in an upper portion of the column near to the top, a liquid outlet having an inside diameter d 2 (cm) at the bottom of the column or in a lower portion of the column near to the bottom, at least one inlet provided in the upper portion and/or a middle portion of the column below the gas outlet, and at least one inlet provided in the lower portion of the column above the liquid outlet, wherein
(1) said length L (cm) satisfies the following formula (1),
1500≦L≦8000 (1),
(2) said inside diameter D (cm) of the column satisfies the following formula (2),
100≦D≦2000 (2),
(3) a ratio of said length L (cm) to said inside diameter D (cm) of the column satisfies the following formula (3),
2 ≦L/D≦ 40 (3),
(4) said number of stages n satisfies the following formula (4),
10≦n≦80 (4),
(5) a ratio of said inside diameter D (cm) of the column to said inside diameter d 1 (cm) of the gas outlet satisfies the following formula (5),
2 ≦D/d 1 ≦15 (5), and
(6) a ratio of said inside diameter D (cm) of the column to said inside diameter d 2 (cm) of the liquid outlet satisfies the following formula (6),
5 ≦D/d 2 ≦30 (6).
2. The process according to claim 1 , wherein distillation is carried out simultaneously in said step (ii).
3. The process according to claim 1 , wherein said aromatic carbonate containing the diaryl carbonate as the main product is continuously produced and an amount of said diaryl carbonate produced is not less than 1 ton per hour.
4. In a process for the production of an aromatic carbonate containing a diaryl carbonate as a main product in which the aromatic carbonate containing the diaryl carbonate as the main product is produced continuously by continuously feeding an alkyl aryl carbonate as a starting material, which is obtainable through a transesterification reaction between a dialkyl carbonate and an aromatic monohydroxy compound, into a continuous multi-stage distillation column in which a catalyst is present, carrying out the reaction and the distillation simultaneously in the column, continuously withdrawing a low boiling point reaction mixture containing a produced dialkyl carbonate from an upper portion of the column in a gaseous form, and continuously withdrawing a high boiling point reaction mixture containing the diaryl carbonate from a lower portion of the column in a liquid form, the improvement in which
said continuous multi-stage distillation column comprises a structure having a pair of end plates above and below a cylindrical trunk portion having a length L (cm) and an inside diameter D (cm), and having an internal with a number of stages n thereinside, and comprises a gas outlet having an inside diameter d 1 (cm) at the top of the column or in an upper portion of the column near to the top, a liquid outlet having an inside diameter d 2 (cm) at the bottom of the column or in a lower portion of the column near to the bottom, at least one inlet provided in the upper portion and/or a middle portion of the column below the gas outlet, and at least one inlet provided in the lower portion of the column above the liquid outlet, wherein
(1) said length L (cm) satisfies the following formula (1),
1500≦L≦8000 (1),
(2) said inside diameter D (cm) of the column satisfies the following formula (2),
100≦D≦2000 (2),
(3) a ratio of said length L (cm) to said inside diameter D (cm) of the column satisfies the following formula (3),
2 ≦L/D≦ 40 (3),
(4) said number of stages n satisfies the following formula (4),
10≦n≦80 (4),
(5) a ratio of said inside diameter D (cm) of the column to said inside diameter d 1 (cm) of the gas outlet satisfies the following formula (5),
2 ≦D/d 1 ≦15 (5), and
(6) a ratio of said inside diameter D (cm) of the column to said inside diameter d 2 (cm) of the liquid outlet satisfies the following formula (6),
5 ≦D/d 2 ≦30 (6).
5. The process according to claim 4 , wherein an amount of the diaryl carbonate produced is not less than 1 ton per hour.
6. The process according to claim 1 , wherein d 1 and d 2 satisfy the following formula (7)
1 ≦d 1 /d 2 ≦6 (7).
7. The process according to claim 1 , wherein L, D, L/D, n, D/d 1 , and D/d 2 for said continuous multi-stage distillation column satisfy the following formulae; 2000≦L≦6000, 150≦D≦1000, 3≦L/D≦30, 15≦n≦60, 2.5≦D/d 1 ≦12, and 7≦D/d 2 ≦25, respectively.
8. The process according to claim 1 , wherein L, D, L/D, n, D/d 1 , and D/d 2 for the continuous multi-stage distillation column satisfy the following formulae; 2500≦L≦5000, 200≦D≦800, 5≦L/D≦15, 20≦n≦50, 3≦D/d 1 ≦10, and 9≦D/d 2 ≦20, respectively.
9. The process according to claim 1 , wherein said continuous multi-stage distillation column is a distillation column having a packing and a tray as the internal.
10. The process according to claim 9 , wherein said continuous multi-stage distillation column is a distillation column having, as the internal, the packing in the upper portion of the column, and the tray in the lower portion of the column.
11. The process according to claim 9 , wherein said packing of the internal is a structured packing.
12. The process according to claim 9 , wherein said tray of the internal is a sieve tray having a sieve portion and a down comer portion.
13. The process according to claim 9 , wherein said packing of the internal is one or more of the structured packing, and said trays is a sieve tray having a sieve portion and a down comer portion.
14. The process according to claim 11 , wherein said structured packing is at least one selected from the group consisting of Mellapak, Gempak, TECHNO-PAK, FLEXI-PAK, a Sulzer packing, a Goodroll packing and a Glitchgrid.
15. The process according to claim 12 , wherein said sieve tray has 100 to 1000 holes/m 2 in the sieve portion.
16. The process according to claim 12 , wherein the cross-sectional area per hole of said sieve tray is in a range of from 0.5 to 5 cm 2 .
17. The process according to claim 13 , wherein said structured packing is at least one selected from the group consisting of Mellapak, Gempak, TECHNO-PAK, FLEXI-PAK, a Sulzer packing, a Goodroll packing and a Glitchgrid, aid sieve tray has 100 to 1000 holes/m 2 in the sieve portion, and the cross-sectional area per hole of said sieve tray is in a range of from 0.5 to 5 cm 2 .