A riser reactor system comprising a riser reactor and a catalyst feed device for fluidized catalyst, the riser reactor having a riser interior in which catalyst is flowing during normal operation, and the feed device comprising an annular trough surrounding the riser interior, the annular trough having an upstream opening for receiving fluidized catalyst, and at least one substantially circumferential downstream opening providing fluid communication between the trough and the riser interior; and a process for the preparation of an olefinic product using a riser reactor system as claimed in any one of the preceding claims, the process comprising reacting an oxygenate feedstock in the presence of an oxygenate conversion catalyst under oxygenate-to-olefin conversion conditions in the riser reactor system, to obtain the olefinic product.