Homogeneous Rh(I)-species are excellent catalysts for carbonylation. A limiting factor for an economical use of these catalysts is the necessity of catalyst separation. In the last 20 years, research was focused on the immobilization of noble metal catalysts at different supports. Until now, none of the immobilized catalysts is used in industrial processes. In this work, a more sophisticated system was developed leading to promising results. It consists of a Rh(I)-catalyst immobilized on an activated carbon. The stability of the catalyst was tested in the carbonylation of 1,3-butadiene to 3-pentenoic acid. An increase of the selectivity of pentenoic acid compared to the homogeneous reaction was found by immobilization of the nobel metal.