In a certain area of ​​the apparatus, where the pressure is 1 atm and the temperature is 200 ° C, the analysis of the gas is 33.33% NH 3 (A), 16.67% N 2 (B), and 50% H 2 (C) by volume. The conditions are such that the ammonia diffuses from the gas stream to the catalyst surface; also the Reaction products diffuse in the opposite direction, as if there were molecular diffusion to through a 1 mm thick gaseous film under a laminar regime.