A process for converting oxygenates to olefins comprising: a) contacting an oxygenate containing stream with a molecular sieve catalyst under oxygenate to olefins conversion conditions in a reactor to form an effluent comprising olefins and entrained solids; b) removing the effluent from the reactor; and c) passing the effluent to a cyclone for separation of the olefins from any entrained solids wherein at least one of the inner surfaces of the cyclone is coated with a protective layer.