A method of distilling a liquid containing dimethyl sulfoxide using a distillation system, including mixing sodium carbonate with a liquid containing dimethyl sulfoxide at a bottom of the distillation system such that sodium carbonate accounts for 0.005% to 25% by weight relative to 100% by weight of the liquid containing dimethyl sulfoxide and sodium carbonate in total at the bottom of the distillation system and heating the bottom; and obtaining a distillate containing dimethyl sulfoxide at a position lower than a position at which the liquid containing dimethyl sulfoxide is introduced and higher than a position of the heating portion.

An apparatus and process doubles the number of trays in a single fractionation column. A dividing wall is used to isolate a first side from a second side and fractionation on trays on each side is independent of the other. A transition vapor stream is ducted from a top of a first side to the bottom of the second side, and a transition liquid stream is ducted from a bottom of the second side to the top of the first side.

A method of distilling a liquid containing dimethyl sulfoxide using a distillation system, including mixing sodium carbonate with a liquid containing dimethyl sulfoxide at a bottom of the distillation system such that sodium carbonate accounts for 0.005% to 25% by weight relative to 100% by weight of the liquid containing dimethyl sulfoxide and sodium carbonate in total at the bottom of the distillation system and heating the bottom; and obtaining a distillate containing dimethyl sulfoxide at a position lower than a position at which the liquid containing dimethyl sulfoxide is introduced and higher than a position of the heating portion.

A method for controlling a reactive distillation column for effecting a transalcoholisation reaction, comprising feeding a metal methoxide into the reactive distillation column via a side feed; feeding a reactant alcohol into a lower part of the reactive distillation column; withdrawing methanol from the top of the reactive distillation column; and withdrawing a solution of a product metal alkoxide in the reactant alcohol from the bottom of the reactive distillation column; wherein the method comprises a process control scheme selected from: Scheme A: establishing a signal S1 which is responsive to a temperature in the rectifying section disposed above the feed of the metal methoxide; and manipulating in response to the signal S1 the feed amount of the reactant alcohol; Scheme B: establishing a signal S1 which is responsive to a temperature in the rectifying section disposed above the feed of the metal methoxide; and manipulating in response to the signal S1 the heat supplied to the bottom of the reactive distillation column. The invention also relates to a method for controlling a reactive distillation column for effecting a transalcoholisation reaction, comprising feeding a metal methoxide into the reactive distillation column via a side feed; feeding a reactant alcohol into a lower part of the reactive distillation column; causing an auxiliary alcohol to be present in the reactive distillation column; and optionally replenishing the auxiliary alcohol via a side feed located above the feed of the reactant alcohol and below the top of the column; withdrawing methanol from the top of the reactive distillation column; and withdrawing a solution of a product metal alkoxide in the reactant alcohol from the bottom of the reactive distillation column; wherein the method comprises a process control scheme selected from: Scheme C: establishing a signal S2 which is responsive to a temperature at a point located between the feed of the metal methoxide and the bottom of the reactive distillation column; and manipulating in response to the signal S2 the feed amount of the reactant alcohol; Scheme D: establishing a signal S2 which is responsive to a temperature at a point located between the feed of the metal methoxide and the bottom of the reactive distillation column; and manipulating in response to the signal S2 the heat supplied to the bottom of the reactive distillation column. The methods of the invention allow for improved controlling of a reactive distillation column for effecting a transalcoholisation reaction.

An apparatus and process doubles the number of trays in a single fractionation column. A dividing wall is used to isolate a first side from a second side and fractionation on trays on each side is independent of the other. A transition vapor stream is ducted from a top of a first side to the bottom of the second side, and a transition liquid stream is ducted from a bottom of the second side to the top of the first side.