Fast-fluidized bed reactor for MTO process

A process for the conversion of a feedstream comprising an oxygenate to produce light olefins, said process comprising:

• a) passing said feedstream in the presence of a diluent to a dense phase zone in a lower reaction zone of a fast-fluidized bed reactor containing a fluidized non-zeolitic catalyst, and at least at effective conditions partially converting said feedstream to a product stream comprising light olefins and deactivating at least a portion of said catalyst to produce a spent catalyst having a carbonaceous deposit thereon;
• b) passing said product stream, an unconverted portion of the feedstream, and a catalyst mixture comprising spent catalyst and a regenerated catalyst to a transition phase zone at a superficial velocity of greater than or equal to 2 meters per second located in said lower reaction zone above said dense phase zone wherein the unconverted portion of the feedstream is essentially completely converted to produce a transition zone effluent comprising light olefins and the catalyst mixture;
• c) passing the transition zone effluent to a first separation zone in an upper disengaging zone of said reaction zone to separate a first portion of the catalyst mixture and to provide a first separated product stream and passing the first portion of the catalyst mixture to an upper catalyst bed in the upper disengaging zone;
• d) passing the first separated product stream to a second separation zone to provide a net product stream comprising a reduced amount of the catalyst mixture and returning a second portion of the catalyst mixture to the upper catalyst bed;
• e) returning at least a portion of the catalyst mixture from the upper catalyst bed to the dense phase zone;
• and
• f) withdrawing a third portion of the catalyst mixture from the upper catalyst bed, at least partially regenerating the third portion of the catalyst mixture to provide a regenerated catalyst, and returning the regenerated catalyst to the lower reaction zone at a point above the dense phase zone to decrease catalyst inventory.