Catalyst structures

An ammonia oxidation process comprising the step of passing a gas mixture comprising ammonia, an oxygen containing gas and optionally a methane containing gas through a catalyst structure comprising an ammonia oxidation catalyst and/or a nitrous oxide decomposition catalyst, wherein the catalyst structure comprises a plurality of shaped catalyst units supported on one or more members in a spaced relationship that avows the structure to flex, wherein the shaped catalyst units have maximum and minimum dimensions in the range 1.5 to 20 mm, and an aspect ratio less than 3, the supporting members are metal or ceramic wires, and the separation of adjacent shaped catalyst units is in the range 1-10 mm, wherein the catalyst structure is disposed on a support mesh.