Process for separating ethyl tert-butyl ether and ethanol

A process for producing ethyl tert-butyl ether through etherification by ethanol of the isobutene contained in a steam-cracking, catalytic cracking or isobutane dehydrogenation C.sub.4 cut, comprising contacting ethanol and the isobutene-containing cut, in a reaction zone A, under reaction conditions such that the product from the reaction zone A, contains ethyl tert-butyl ether, ethanol, C.sub.4 hydrocarbons including non-reacted isobutene;

• sending the product from reaction zone A into a distillation zone B, collecting the C.sub.4 hydrocarbons including the non-reacted isobutene overhead and a mixture of ethyl tert-butyl ether and ethanol at the base;
• sending the mixture into a separation zone C and conducting therein a process for separating ethyl tert-butyl ether and ethanol, which comprises:
• (1) an extraction stage comprising introducing a charge, consisting essentially of a mixture of ethyl tert-butyl ether and ethanol, into an extraction zone, introducing water as an extraction solvent into the extraction zone and therefrom collecting a raffinate, consisting essentially of ethyl tert-butyl ether saturated in water, and an extract comprising an ethanol and water mixture containing ethyl tert-butyl ether;
• (2) a concentration stage comprising passing the extract from stage (1) into a concentration zone, withdrawing therefrom an overhead product having a composition close to that of an azeotropic ethanol and water composition at the head, a residue consisting essentially of water at the base, and a phase consisting essentially of ethyl tert-butyl ether at a withdrawal point between the head and the base and condensing said overhead product to obtain a distillate;
• and
• (3) a heteroazeotropic distillation stage having first and second distillation zones using ethyl tert-butyl ether as an azeotroping agent, comprising passing the distillate from the concentration stage into a first distillation zone and collecting therefrom a residue at the base consisting essentially of ethanol and an overhead vapor at the head, combining the overhead vapor with vapor from the head of the second distillation zone, condensing the resultant combined vapor, and passing the resultant condensate into a decanter, separating said condensate into an upper phase, rich in ethyl tert-butyl ether and a lower phase, rich in water, passing the upper phase as reflux to the head of the first distillation zone as the azeotroping agent, passing the lower phase as reflux to the head of the second distillation zone, and collecting from the second distillation zone a residue consisting essentially of water.

In a process for separating a composition comprising ethanol and water having a composition close to that of an azeotropic ethanol and water composition in a heteroazeotropic distillation stage, the improvement wherein ethyl tert-butyl ether is used as an azeotroping agent, which improved process comprises:

• introducing said ethanol and water composition and ethyl tert-butyl ether into a first distillation zone,
• collecting therefrom a residue at the base consisting essentially of ethanol and a vapor from the head,
• combining the vapor with the vapor from the head of a second distillation zone,
• condensing the resultant combined vapor,
• passing the resultant condensate into a decanter,
• separating the condensate in the decanter into an upper phase rich in ethyl tert-butyl ether and a lower phase rich in water,
• passing the upper phase in reflux to the head of the first distillation zone as the azeotroping agent,
• passing the lower phase as reflux to the head of the second distillation zone, and
• collecting from the second distillation zone a residue consisting essentially of water.

A process for producing ethyl tert-butyl ether through etherification by ethanol of the isobutene contained in a steam-cracking, catalytic cracking or isobutane dehydrogenation C.sub.4 cut, comprising contacting ethanol and the isobutene-containing cut, in a reaction zone A, under reaction conditions such that the product from the reaction zone A, contains ethyl tert-butyl ether, ethanol and C.sub.4 hydrocarbons including non-reacted isobutene;

• sending the product from reaction zone A into a reactive distillation zone B.sup.1, introducing ethanol into the reactive distillation zone under reaction conditions such that the ethanol reacts with the non-reacted isobutene, collecting the C.sub.4 hydrocarbons including the non-reacted isobutene overhead and a mixture of ethyl tert-butyl ether and ethanol at the base;
• sending the mixture into a separating zone C and conducting therein a process for separating ethyl tert-butyl ether and ethanol, which comprises:
• (1) an extraction stage comprising introducing a charge, consisting essentially of a mixture of ethyl tert-butyl ether and ethanol, into an extraction zone, introducing water as an extraction solvent into the extraction zone and therefrom collecting a raffinate, consisting essentially of ethyl tert-butyl ether saturated in water, and an extract comprising an ethanol and water mixture containing of ethyl tert-butyl ether;
• (2) a concentration stage comprising passing the extract from stage (1) into a concentration zone, withdrawing therefrom an overhead product having a composition close to that of an azeotropic ethanol and water composition at the head, a residue consisting essentially of water at the base, and a phase consisting essentially of ethyl tert-butyl ether at a withdrawal point between the head and the base and condensing said overhead product to obtain a distillate;
• and
• (3) a heteroazeotropic distillation stage having first and second distillation zones using ethyl tert-butyl ether as azeotroping agent, comprising passing the distillate from the concentration stage into a first distillation zone and collecting therefrom a residue at the base consisting essentially of ethanol and overhead vapor combining the overhead vapor at the head, with the vapor from the head of a second distillation zone, condensing the resultant combined vapor, and passing the resultant condensate into a decanter, separating the condensate into an upper phase, rich in ethyl ether and a lower phase, rich in water, passing the upper phase in reflux to the head of the first distillation zone as the azeotroping agent, passing the lower phase as reflux to the head of the second distillation zone, and collecting from the second distillation zone a residue consisting essentially of water.