Process for production of dialkyl carbonate and diol
It is an object of the present invention to provide, for a case of producing a dialkyl carbonate and a diol from a cyclic carbonate and an aliphatic monohydric alcohol, a process that simultaneously satisfies the cyclic carbonate conversion being high, the selectivities for the dialkyl carbonate and diol to be produced being high, and a high-purity diol having a high UV transmittance and a low aldehyde content being obtained without carrying out complicated treatment such as feeding water into a diol distillation purification step. The present invention discloses a process for the production of the dialkyl carbonate and the diol in which, when producing the dialkyl carbonate and the diol by reacting the cyclic carbonate and the aliphatic monohydric alcohol together in the presence of a catalyst in a transesterification reactor comprising a tray type continuous multi-stage distillation column, reaction conditions (residence times, temperatures) in the distillation column are controlled to be specific conditions.
1. In a process for continuous production of a dialkyl carbonate and a diol, by continuously feeding a first starting material containing a cyclic carbonate as a main component thereof and a second starting material containing an aliphatic monohydric alcohol as a main component thereof into a tray column type continuous multi-stage distillation column, bringing the starting materials into contact with a catalyst present in said distillation column so as to bring about reaction in a tray portion and a column bottom portion, continuously withdrawing a low boiling point component containing a produced dialkyl carbonate from an upper portion of said distillation column, and continuously withdrawing a high boiling point component containing a produced diol from a lower portion of said distillation column, wherein the improvement comprises:
the following formula (1) being satisfied,
780≦α+1.24×β≦5150 (1),
wherein
α=θ 1 0.52 ×(T 1 +120) 1.2 ,
β=θ 2 0.52 ×(T 2 +120) 1.2 ,
θ 1 (hours) is an average residence time of the reaction liquid in the tray portion of said distillation column in which the catalyst is present;
T 1 (° C.) is a temperature at a (n/2) th stage (a ((n+1)/2) th stage in the case that n is odd) from the top of the tray portion in which the catalyst is present wherein n is a total number of stages therein;
θ 2 (hours) is an average residence time of the reaction liquid in the column bottom portion of said distillation column; and
T 2 (° C.) is a temperature in the column bottom portion.
2. The process for continuous production of the dialkyl carbonate and the diol according to claim 1 , wherein the catalyst is a homogeneous catalyst.
3. The process for continuous production of the dialkyl carbonate and the diol according to claim 1 or 2 , wherein θ 1 is in a range of from 0.3 to 20 hours, and θ 2 is in a range of from 0.3 to 25 hours.
4. The process for continuous production of the dialkyl carbonate and the diol according to claim 1 , wherein each of T 1 and T 2 is in a range of from −20° C. to 350° C.