TH29611B - Methods for the continuous production of dialkyl carbonate and diol. - Google Patents

Abstract

DC60 (06/09/42) A method for the continuous, highly productive and selective production of dialkyl carbonates and diols, which involves the continuous feeding of cyclic carbonates and aliphatic monohydric alcohols into a continuous multistage distillation column, resulting in continuous transesterification between cyclic carbonates and aliphatic monohydric alcohols under transesterification-catalyzed conditions in the multistage distillation column. This results in the continuous production of dialkyl carbonates and diols, while continuously drawing a low-boiling point mixture containing the produced dialkyl carbonate in gaseous form from the upper part of the multistage distillation column and a high-boiling point mixture containing the produced diol in liquid form from the lower part of the multistage distillation column. The transesterification is carried out under conditions where (a) the reaction pressure is 5 x 10⁴ Pa or less; (b) the reaction temperature ranges from -20 °C to less than 60 °C; (c) The multistage distillation column has a factor F in the range of 0.2 to 5.0 and the factor F is represented by the following formula (1): Factor F = Ug²⁻g)1/2 (1), where ug represents the gas velocity (m/s) in the multistage distillation column and rg represents the gas density (kg/m³) in the multistage distillation column. The method for the continuous production of high-yield and highly selectivity dialkyl carbonate and diol consists of the continuous feeding of cyclic carbonate and aliphatic monohydric alcohol into a continuous multistage distillation column and resulting in continuous transesterification between cyclic carbonate and aliphatic monohydric alcohol under transesterification-catalyzed conditions in the multistage distillation column, thus producing continuous dialkyl carbonate and diol. While continuously drawing a low-boiling point mixture containing dialkyl carbonate produced in gaseous form from the upper part of the multistage distillation column and continuously drawing a high-boiling point mixture containing diol produced in liquid form from the lower part of the multistage distillation column, where transesterification is carried out under conditions where (a) the reaction pressure is 5 x 10⁴ Pa or less; (b) the reaction temperature is in the range from -20 °C to less than 60 °C; and (c) the distillation column has a factor F in the range from 0.2 to 5.0 and the factor F is represented by the following formula (1): Factor F = Ug ((formula)g)1/2, where Ug represents the gas velocity (m/s) in the multistage distillation column and (formula)g represents the gas density (kg.m²) in the distillation column.

Claims (6)

1. A method for the continuous production of dialkyl carbonates and diols from cyclic carbonates and aliphatic monohydric alcohols, which involves the continuous feeding of cyclic carbonates, represented by the following formula (A) (chemical formula), where R1 is a divalent group represented by the formula -(CHZ)m, where m is an integer from 2 to 6, which is either unreplaced or replaced by at least one selective substitute from the C1-C10 alkyl and C6-C10 aryl groups, and an aliphatic monohydric alcohol, represented by the following formula (B), R2OH (B), where R2 is a monovalent aliphatic C1-C12 hydrocarbon group, which is either unreplaced or replaced by at least one selective substitute from the C1-C10 alkyl and C6-C10 aryl groups, into a continuous multistage distillation column, resulting in continuous transesterification between the said cyclic carbonates. The aliphatic monohydric alcohols are then catalyzed by transesterification in the aforementioned multistage distillation column, resulting in the continuous production of dialkyl carbonates and diols. A low-boiling point mixture containing the produced dialkyl carbonates in gaseous form is continuously drawn from the upper part of the multistage distillation column, while a high-boiling point mixture containing the produced diols in liquid form is continuously drawn from the lower part of the multistage distillation column. This transesterification is carried out under conditions where (a) the reaction pressure is 5 x 10⁴ Pa or less, as measured at the inner lower part of the multistage distillation column; (b) the reaction temperature ranges from -20 °C to less than 60 °C, as measured at the inner lower part of the multistage distillation column; and (c) the multistage distillation column has a factor F ranging from 0.2 to 5.0, and this factor F is represented by the following formula (1): Factor F = Ug ((formula)g) 1/2, where Ug represents the gas velocity. (meters/second) in a multistage distillation column, and (formula) Pg represents the gas density (kg/m³) in a multistage distillation column. 2. The method according to claim 1, where the aforementioned factor F ranges from 0.4 to 4.0. 3. The method according to claim 2, where the aforementioned factor F ranges from 0.6 to 4.0. 4. Any of the methods under Responses 1 through 3, where the aliphatic monohydric alcohol is concomitantly contained with dialkyl carbonate in an amount ranging from 0 to 40% by weight, based on the total weight of the concomitant aliphatic monohydric alcohol and dialkyl carbonate. 5. Any of the methods under Requisitions 1 through 3, using such cyclic carbonate as at least one carbonate of choice from the group consisting of ethylene carbonate and propylene carbonate, and such aliphatic monohydric alcohol as methanol. 6. Any of the methods under Reputations 1 through 3, whereby the cyclic carbonate is continuously fed into the upper part of the multistage distillation column in liquid or gas-liquid mixture form, and the aliphatic monohydric alcohol is continuously fed into the lower part of the multistage distillation column in gaseous or gas-liquid mixture form, or specifically in gaseous and liquid forms.