<p>In a fluidized-bed reactor having a specific equivalent diameter and made of a material with a particular iron content, hydrogen chloride and oxygen are reacted in particular gas volumes and at specific molar ratio, superficial velocity, temperature and pressure in the presence of a catalyst composed principally of a chromium oxide and having a specific particle size distribution. The catalyst is present in a specific amount in terms of catalyst layer height at rest. The catalyst can retain its high activity.</p>
