Glycerol is a renewable resource, obtained as a co-product of the transesterification of vegetables oils to produce biodiesel. Its conversion to 1,2-propanediol (1,2-PDO) and 1,3- propanediol (1,3- PDO) in the presence of heterogeneous catalysts has been particularly investigated.[1-4] The selective production of 1,3-PDO has appeared to be much more challenging than the one of 1,2-PDO. Indeed, it hasn’t been achieved yet. To the best of our knowledge, no theoretical study on this topic has ever been published. More- over, the mechanisms which take place at the surface are still relatively misunderstood. However, coupling DFT calculations with experimental results could be very powerful to explain the metal influence on the selectivity. Considering previous DFT investigations done in our laboratory, some interesting pieces of infor- mation have been pointed out for the dehydration of glycerol on Ni (111), Rh (111) and Pd(111)[5]. We are currently pursuing this work by studying the mechanism of the dehydrogenation of glycerol on Rh (111) and Ir (111) with VASP code (PW91 functional).[6] We are particularly interested in the comparison of the different pathways of dehydrogenation on these metals. [1] Alhanash,A.;Kozhevnikova,E.;Kozhevnikov,I.CatalysisLetters2008,120,307-311. [2] Kurosaka,T.;Maruyama,H.;Naribayashi,I.;Sasaki,Y.CatalysisCommunications2008,9,1360-1363. [3] Furikado,I.;Miyazawa,T.;Koso,S.;Shimao,A.;Kunimori,K.;Tomishige,K.GreenChemistry2007,9, 582-588. [4] Chaminand, J.; Djakovitch, L..; Gallezot, P.; Marion, P.; Pinel, C.; Rosier, C. Green Chemistry 2004, 6, 359-361. [5] Coll,D.S.;Sautet,P.;Aray,Y.;Delbecq,F.Unpublishedresults. [6] G.Kresse;J.Furthmüller.PhysicalReviewsB,199654,11169