Process for continuously producing an aromatic carbonate

Details Process for continuously producing an aromatic carbonate Process for continuously producing an aromatic carbonate

1991-06-28

1993-05-11

Dees, Jose G.

Organic compounds -- part of the class 532-570 series

Organic compounds

Carbonate esters

558274, 558277, C07C 6996

Patent

active

052102688

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

1. Technical Field
The present invention relates to a process for continuously producing an aromatic carbonate. More particularly, the present invention is concerned with a process comprising transesterifying a starting material selected from the group consisting of a dialkyl carbonate represented by ##STR1## an alkyl aryl carbonate represented by ##STR2## and a mixture thereof with a reactant selected from the group consisting of an aromatic hydroxy compound represented by Ar.sup.1 OH, an alkyl aryl carbonate represented by ##STR3## and a mixture thereof, to thereby produce an aromatic carbonate or aromatic carbonate mixture corresponding to the starting material and the reactant and represented by ##STR4## wherein R and Ar are, respectively, selected from R.sup.1, R.sup.2 and R.sup.3 and selected from Ar.sup.1, Ar.sup.2 and Ar.sup.3 in correspondence to the starting material and the reactant, wherein the starting material and the reactant are continuously fed to a continuous multi-stage distillation column to effect a transesterification reaction therebetween in the presence of a catalyst in the distillation column, while continuously withdrawing the aromatic carbonate or aromatic carbonate mixture produced as a high boiling point product in a liquid form from a lower portion of the distillation column and continuously withdrawing a by-product produced as a low boiling point product in a gaseous form from an upper portion of the distillation column by distillation, thereby enabling the aromatic carbonate or aromatic carbonate mixture to be produced continuously with high efficiency.
2. Background Art
An aromatic carbonate is useful as a raw material for the production of an aromatic polycarbonate (whose utility as engineering plastics has been increasing in recent years) without using poisonous phosgene, or as a raw material for the production of various isocyanates without using poisonous phosgene. With respect to the method for the production of an aromatic carbonate, a method for producing an aromatic carbonate or an aromatic carbonate mixture, is known, in which a dialkyl carbonate, an alkyl aryl carbonate or a mixture thereof is used as a starting material and an aromatic hydroxy compound, an alkyl aryl carbonate or a mixture thereof is used as a reactant, and in which a transesterification reaction is performed between the starting material and the reactant.
However, since this type of transesterification is a reversible reaction in which, moreover, not only is the equilibrium biased toward the original system but the reaction rate is also low, the production of an aromatic carbonate by the above-mentioned method on an industrial scale is accompanied with great difficulties.
To improve the above-mentioned method, several proposals have been made, most of which relate to the development of a catalyst for increasing the reaction rate. As a catalyst for use in the method for producing an alkyl aryl carbonate, a diaryl carbonate or a mixture thereof by reacting a dialkyl carbonate with an aromatic hydroxy compound, there have been proposed various catalysts, which include for example, a Lewis acid, such as a transition metal halide, or compounds capable of forming a Lewis acid, [Japanese Patent Application Laid-Open Specification No. 51-105032, Japanese Patent Application Laid-Open Specification No. 56-123948 and Japanese Patent Application Laid-Open Specification No. 56-123949 (corresponding to West German Patent Application Laid-Open Specification No. 2528412, British Patent No. 1499530 and U.S. Pat. No. 4,182,726)], a tin compound, such as an organotin alkoxide and an organotin oxide [Japanese Patent Application Laid-Open Specification No. 54-48733 (corresponding to West German Patent Application Laid-Open Specification No. 2736062), Japanese Patent Application Laid-Open Specification No. 54-63023, Japanese Patent Application Laid-Open Specification No. 60-169444 (corresponding to U.S. Pat. No. 4,554,110), Japanese Patent Application Laid-Open Specification No. 60-169445 (corresponding

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