No, they are NOT interchangeable. "上级对下级用敦促" (used by people when speaking to their underlings) is also incorrect.
Nowadays 敦促 means urging someone/some authority to *do* something.
催促 is more about urgency in time, and is usually usually between persons, say A wants B to do/finish something sooner. So, for "the manager urges Wang to finish his task as soon as possible", we say 经理催促小王尽快完成任务
in a word, 敦促 is saying "do it!"
催促 is saying "do it fast!"
(Sorry I don't speak French, otherwise I would have answered in your language)