An apparatus comprising a continuous multi-stage distillation column A, a continuous multi-stage distillation column C, and a continuous multi-stage distillation column E, for carrying out a process for producing a high-purity diol by taking a cyclic carbonate and an aliphatic monohydric alcohol as starting materials, the process comprising the steps of:
- (I) 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 distillation column A, continuously withdrawing a low boiling point reaction mixture AT containing a produced dialkyl carbonate and the aliphatic monohydric alcohol from an upper portion of the distillation column A in a gaseous form, and continuously withdrawing a high boiling point reaction mixture AB containing a produced diol from a lower portion of the distillation column A in a liquid form;
- (II) continuously feeding said high boiling point reaction mixture AB into the continuous multi-stage distillation column C, continuously withdrawing material having a lower boiling point than that of the diol contained in said high boiling point reaction mixture AB as a column top component CT and/or a side cut component CS, and continuously withdrawing a column bottom component CB having the diol as a main component thereof from a lower portion of the distillation column C;
- and
- (III) continuously feeding said column bottom component CB into the continuous multi-stage distillation column E, and continuously withdrawing a high-purity diol as a side cut component ES from a side cut outlet of said continuous multi-stage distillation column E;
- wherein improvement comprises:
- (a) said continuous multi-stage distillation column A comprising a distillation column having a length L0 (cm), an inside diameter D0 (cm) and an internal having a number of stages n0 thereinside, and further having a gas outlet having an inside diameter d01 (cm) at a top of the column or in an upper portion of the column near to the top, a liquid outlet having an inside diameter d02 (cm) at a bottom of the column or in a lower portion of the column near to the bottom, at least one first inlet provided in the upper portion and/or a middle portion of the column below the gas outlet, and at least one second inlet provided in the middle portion and/or the lower portion of the column above the liquid outlet, wherein L0, D0, n0, d01, and d02 satisfy the following formulae (1) to (6):
- 2100≦L0≦8000 (1)
- 180≦D0≦2000 (2)
- 4≦L0/D0≦40 (3)
- 20≦n0≦120 (4)
- 3≦D0/d01≦20 (5) and
- 5≦D0/d02≦30 (6);
- (b) said continuous multi-stage distillation column C comprising a continuous multi-stage distillation column comprising a stripping section having a length LC1 (cm), an inside diameter DC1 (cm) and an internal with a number of stages nC1 thereinside, and an enrichment section having a length LC2 (cm), an inside diameter DC2 (cm) and an internal with a number of stages nC2 thereinside, wherein LC1, DC1, nC1, LC2, DC2, and nC2 satisfy the following formulae (7) to (15):
- 300≦LC1≦3000 (7)
- 50≦DC1≦700 (8)
- 3≦LC1/DC1≦30 (9)
- 3≦nC1≦30 (10)
- 1000≦LC2≦5000 (11)
- 50≦DC2≦500 (12)
- 10≦LC2/DC2≦50 (13)
- 20≦nC2≦100 (14) and
- DC2≦DC1 (15);
- (c) the enrichment section of said continuous multi-stage distillation column C has at least one chimney tray installed therein as the internal, said chimney tray having installed therein one or more chimneys each having an opening having a cross-sectional area SC (cm2) satisfying the formula (16):
- 200≦SC≦1000 (16),
- and each of the chimneys being such that a height hC (cm) from said opening of said chimney to a gas outlet of said chimney satisfies the formula (17):
- 10≦hC≦80 (17);
- (d) the side cut outlet is connected to a liquid collecting portion of said chimney tray of said continuous multi-stage distillation column C;
- (e) said continuous multi-stage distillation column E comprising a continuous multi-stage distillation column comprising a stripping section having a length LE1 (cm), an inside diameter DE1 (cm) and an internal with a number of stages nE1 thereinside, and an enrichment section having a length LE2 (cm), an inside diameter DE2 (cm) and an internal with a number of stages nE2 thereinside, wherein LE1, DE1, nE1, LE2, DE2, and nE2 satisfy the following formulae (18) to (26):
- 400≦LE1≦3000 (18)
- 50≦DE1≦700 (19)
- 2≦LE1/DE1≦50 (20)
- 3≦nE1≦30 (21)
- 600≦LE2≦4000 (22)
- 100≦DE2≦1000 (23)
- 2≦LE2/DE2≦30 (24)
- 5≦nE2≦50 (25) and
- DE1≦DE2 (26);
- (f) the enrichment section of said continuous multi-stage distillation column E has at least one chimney tray installed therein among the internals, said chimney tray having installed therein at least two chimneys each having an opening having a cross-sectional area SE (cm2) satisfying the formula (27):
- 50≦SE≦2000 (27),
- and each of the chimneys being such that a height hE (cm) from said opening of said chimney to a gas outlet of said chimney satisfies the formula (28):
- 20≦hE≦100 (28);
- and
- (g) the side cut outlet is connected to a liquid collecting portion of said chimney tray of said continuous multi-stage distillation column E.