Device and process for separating at least one compound from a mixture in a simulated moving bed, comprising: an enclosure comprising several absorbent beds, two adsorbent beds being separated by a fluid distribution and extraction plate (Pi), the plate comprising one or more distribution, mixing and/or extracting panels, comprising a chamber (Ci), main fluid delivery (4) and extraction (2) lines, several secondary fluid extraction or injection lines (10, 11, 12, 13, Ti), a bypass circuit communicating a distribution plate with a bypass line, means (14, Voi,j, 20) communicating at least one chamber (Ci) with at least one bypass line (Li,j), at least one of the ends of a bypass line communicates with a zone Ri, R′I of an adsorbent bed, said zone being distinct from a distribution chamber (Ci) and another end is connected to said chamber (Ci).