Long-Chain-Amine Metal Complexes as Hydrogenation Catalysts. Heterogenisation on Activated Carbon

The catalytic activity of [PdCl₂(NH₂(CH₂)₁₂CH₃)₂] (named [Pd(TDA)]) and [RhCl(NH₂(CH₂)₁₂CH₃)₃] (named [Rh(TDA)]) complexes for the hydrogenation of cyclohexene has been analysed both in homogeneous phase and heterogenised on activated carbon. The [Rh(TDA)] complex has been found to be more active than the [Pd(TDA)], both homogeneous and heterogenised. Experimental and modelled results indicate that these complexes follow a similar reaction mechanism, but with different rates. A clear positive effect of the carbon support has been found in the case of the complex [Rh(TDA)], which has been related to the anchorage of the aliphatic chains of the amine ligands on the activated carbon pores. Experiments in consecutive catalytic runs show that the heterogenised complexes can be used several times giving an acceptable conversion level.     

Highly Active Catalyst from [PdCl2(NH2(CH2)12CH3)2] on NH4ZSM-5

A palladium catalyst highly active for the cyclohexene hydrogenation has been obtained by heterogenisation of [PdCl₂(NH₂(CH₂)₁₂CH₃)₂] on zeolite NH₄ZSM-5. TOF is more than twenty times higher than for the homogeneous catalyst or the activated carbon heterogenised complex. Changes in the electronic state of palladium have been observed by XPS analysis. Palladium reduction is produced upon heterogenisation on the NH₄ZSM-5 zeolite.