Disclosed herein is a method of recovery of the activity of a molecular sieve catalyst following use of the catalyst in an OTO conversion process. This is achieved by a regeneration apparatus and a method of regenerating a molecular sieve catalyst, comprising two stages. In a pretreatment stage, the catalyst is pretreated under pretreatment conditions by heating the catalyst to a temperature of between 320° C. to 700° C. in an oxygen depleted medium for a residence time of between 1 minute to two hours; and, in a regeneration stage, the catalyst is regenerated under regeneration conditions by heating the catalyst at a temperature of between 200° C. to 700° C. in an oxidizing medium for a residence time of between 1 to 60 minutes.