Use of closed or semi-closed loop regeneration of molecular sieve in dehydration driers using nitrogen or process gases in alcohol to olefins processes

A semi-closed loop or closed loop regeneration process for an adsorber comprising a molecular sieve comprising:

• heating a dry regenerant gas stream forming a heated regenerant gas stream, wherein the dry regenerant gas stream comprises a vapor comprising a hydrocarbon having one to three carbon atoms;
• introducing the heated regenerant gas stream into the adsorber to remove water from the adsorber forming a wet regenerant gas stream;
• cooling the wet regenerant gas stream to form a cooled wet regenerant gas stream;
• separating water from the cooled wet regenerant gas stream in a knockout drum forming a dehydrated regenerant gas stream and a water stream;
• compressing the dehydrated regenerant gas stream with a compressor to form a compressed dehydrated regenerant gas stream;
• and
• recycling the compressed, dehydrated regenerant gas stream to regenerate the adsorber;
• cooling the dehydrated regenerant gas stream or the compressed dehydrated regenerant gas stream;
• and
• replacing the dry regenerant gas stream with a second regenerant gas stream comprising nitrogen when the dry regenerant gas stream is not within a desired range or when the dry regenerant gas stream is not available.