(FR2752175-A1)      In the treatment of a catalyst with a lead-based active phase, contaminated with arsenic, the catalyst is heated to at least 550C in the presence of a gaseous mixture comprising at least 20 vol.% of a reducing gas, the remainder being an inert gas.    USE -   Arsenic is an element particularly harmful to the environment, and is usually present in cracked gases from vapour cracking units. It is usually eliminated by contacting the gases with a lead compound, e.g. an oxide, the arsenic forming a mixed compound of arsenic and lead which is ad/absorbed on the catalyst. In the above process, the arsenic is eliminated by heating and can be recovered by any means, e.g. by condensation to give the metal. The amount of arsenic in the catalyst may be up to 22%. The elimination of the arsenic can be monitored by atomic absorption analysis.    ADVANTAGE -   The process regenerates the active phase of the catalyst and the support has almost the same characteristics as in the original product.    (US5942458-A)      In the treatment of a catalyst with a lead-based active phase, contaminated with arsenic, the catalyst is heated to at least 550C in the presence of a gaseous mixture comprising at least 20 vol.% of a reducing gas, the remainder being an inert gas.    USE -   Arsenic is an element particularly harmful to the environment, and is usually present in cracked gases from vapour cracking units. It is usually eliminated by contacting the gases with a lead compound, e.g. an oxide, the arsenic forming a mixed compound of arsenic and lead which is ad/absorbed on the catalyst. In the above process, the arsenic is eliminated by heating and can be recovered by any means, e.g. by condensation to give the metal. The amount of arsenic in the catalyst may be up to 22%. The elimination of the arsenic can be monitored by atomic absorption analysis.    ADVANTAGE -   The process regenerates the active phase of the catalyst and the support has almost the same characteristics as in the original product.