Dimethyl ether (dme) synthesis

A process for producing dimethyl ether, comprising:

• obtaining a crude methanol feedstock comprising methanol, water, acetone, methyl formate, and one or more of ethanol, propanol, and butanol;
• contacting the crude methanol with a glycol, a glycerol, or a mixture of glycols in an azeotropic distillation column to recover a first overhead stream comprising the acetone and methyl formate and a first bottoms stream comprising the glycol or glycerol, water, methanol, and, when contained in the feed, the ethanol, propanol and butanol;
• separating the first bottoms stream in a dividing wall distillation column to recover a second overhead stream comprising methanol and water, a second bottoms stream comprising the glycol or glycerol, a side draw stream comprising water and, when contained in the feed, the ethanol, propanol and butanol;
• and
• feeding the second overheads stream comprising methanol and water to a reaction system for converting the methanol to dimethyl ether and to recover a reaction effluent comprising dimethyl ether, methanol, and water.

A system for producing dimethyl ether, comprising:

• a feed stream for supplying a crude methanol feedstock comprising methanol, water, one or more hydrocarbon impurities that form an azeotrope with methanol and one or more hydrocarbons having a boiling point greater than methanol;
• an azeotropic distillation column configured for contacting the crude methanol with a glycol or glycerol to recover a first overhead stream comprising the one or more hydrocarbon impurities that form an azeotrope with methanol and a first bottoms stream comprising the glycol or glycerol, water, methanol, and the one or more hydrocarbons having a boiling point greater than methanol;
• a dividing wall distillation column configured for separating the first bottoms stream to recover a second overheads stream comprising methanol and water, a second bottoms stream comprising the glycol or glycerol, and a side draw stream comprising water and the one or more hydrocarbons having a boiling point greater than methanol;
• and
• a reaction system configured for receiving the second overheads stream comprising methanol and water and for converting the methanol to dimethyl ether and to recover a reaction effluent comprising dimethyl ether, methanol, and water.