Bi-modal radial flow reactor

A process for replacing catalyst in a bi-modal radial flow reactor, the process comprising:

• providing a bi-modal radial flow reactor, wherein the bi-modal radial flow reactor comprises:
• a) a cylindrical outer housing surrounding at least five cylindrical, concentric zones, including at least three annulus vapor zones and at least two catalyst zones, wherein the at least two catalyst zones comprise an outer catalyst zone and an inner catalyst zone, and wherein the at least three annulus vapor zones comprise an outer annulus vapor zone, a middle annulus vapor zone, and a central annulus vapor zone, wherein the central annulus vapor zone extends along a centerline of the bi-modal radial flow reactor, and wherein the outer catalyst zone is intercalated with the outer annulus vapor zone and the middle annulus vapor zone, and wherein the inner catalyst zone is intercalated with the middle annulus vapor zone and the central annulus vapor zone;
• and
• b) a manifold configured to introduce a feed vertically into a bottom end of each of one or two of the at least three annulus vapor zones, and remove a product from a bottom end of each of the one or two remaining of the at least three annulus vapor zones;
• operating the bi-modal radial flow reactor until a catalyst in a catalyst zone comprising the outer catalyst zone, the inner catalyst zone, or both is spent;
• and
• providing the catalyst zone with catalyst that is not spent by filling the catalyst zone with fresh catalyst, by regenerating the spent catalyst, or a combination thereof.