This invention relates to hydrocarbon conversion processes using a novel crystalline metallo manganese oxides that have the hollandite structure. The composition is represented by the formula A.sub.y Mn.sub.8-x M.sub.x O.sub.16 where A is a templating agent such as potassium, ammonium, and y varies from about 0.5 to about 2.0, M is a metal such as chromium, vanadium, gallium, antimony and x varies from about 0.01 to about 4.0. These oxides have a three-dimensional structure with manganese and the M metals forming the framework. Examples of the processes in which these compositions can be used are oxydehydrogenation and ammoxidation. These compositions are also effective for oxidizing cyanide in aqueous streams.