Abstract: The invention relates to processes for high-temperature catalytic conversion of ammonia in a two-stage catalytic system in which the first stage, in the downstream direction of the flow of gas comprising at least ammonia and oxygen, is a layer of nettings made of alloys comprising platinoids, while the second stage is composed of catalysts that do not comprise noble metals. The field of use of the proposed invention extends to the production of nitric acid and prussic acid, and also hydroxylamine sulfate. The object of the instant invention is to reduce the content and loss of platinoids and to increase the yield of the desired product. This object is attained by passing a reaction gaseous mixture comprising ammonia and an oxygen-containing gas through a two-stage catalytic system in which the first stage in the downstream direction of the flow of gas is a layer of platinoid nettings, and 2-5 spaced layers of a catalyst of a regular honeycomb structure are used in the second stage of the catalytic system.