In a catalyst carrier for insertion in a tube of a reactor, an annular container holds the catalyst in use and has a perforated inner wall defining a tube, a perforated outer wall, a top surface closing the annular container and a bottom surface closing the annular container. A surface closes the bottom of the tube formed by the inner wall of the annular container. A skirt extends upwardly from the perforated outer wall of the annular container from a position at or near the bottom surface to a position below the location of a seal located at or near the top surface and extending from the container by a distance which extends beyond an outer surface of the skirt.