OP-II-3

KN-7at temperature lower than 873K, MWCN with Ni at tip regularly formed and catalystsdestroys due to the detachment of Ni particle from the carrier surface.CarbonFilamentsCoFig. 1. Relative activity as a function ofreaction /regeneration cycles:Co catalyst; Tr = 923K.Fig. 2. Evidence of carbon filament growingmechanism on Co thin layer catalyst.On the contrary, Co catalysts were found not so active at low temperature(< 873K) but they resulted to be very active and sufficiently stable at highertemperature (923K) and can be regenerated by oxygen treatment (see Fig.1).Iirrespective of reaction temperature investigated, on the contrary of what occur onNi-based catalysts, on Co TLC sample due to a strong MSI filamentous coke formswith a “base” reaction mechanism (see Fig. 2) and Co particles remain well anchoredon Al 2 O 3 carrier. This allowed to realize a dual-step system based on CDNG reactionat 923K and regeneration at 823K in oxygen stream without any deactivationproblem.References[1]. G. Italiano, C.Espro, F.Arena, F.Frusteri, A.Parmaliana, Stud. Surf. Sci. Catal. 162 (2006) 633.[2]. D. Chen, R. Lødeng, A. Anundskas, O. Olsvik, and A. Holmen, Chem. Eng. Sci. 56 (2001)1371.[3]. S. Takenaka, H. Ogihara, I. Yamanaka, K. Otsuka, Appl. Catal. A: Gen. 217 (2001)633.[4]. B. Monnerat, L. Kiwi-Minsker, A. Renken, Chem. Eng. Sci. 56 (2001) 633.[5]. L.B. Avdeeva, O.V. Ghoncarova, D.I. Kochubey, V.I. Zaikovskii, L.M. Plyasova, B.N.Novgorodov,S.K. Shaikhutdinov, Appl. Catal. A 141 (1996) 117.[6]. L.B. Avdeeva, D.I. Kochubey, Sh.K. Shaikhutdinov, Appl. Catal. A 177 (1999) 43.[7]. M.A. Ermakova, D.Yu. Ermakov, G.G. Kuvshinov, Appl. Catal. A 201 (2000) 61.[8]. S. Takenaka, Y. Tomikubo, E. Kato, K. Otsuka, Fuel 83 (2004) 47.[9]. T.V. Choudhary, C. Sivadinarayana, A. Klinghoffer, D.W. Goodman, Stud. Surf. Sci. Catal.1362001) 197.[10]. G. Italiano, C. Espro, F. Arena, F. Frusteri, A. Parmaliana, Catal. Letters 124 (2008) 7.[11]. M. Wietschel, U. Hasenauer, Renewable Energy 32 (2007) 2129.35