Homogeneous models for hydrodenitrogenation catalysis

Hydrodenitrogenation (HDN) catalysis is the process of removing nitrogen from petroleum feedstocks in the form of NH3 to provide more processable and environmentally compatible liquid fuels. In practice, HDN is carried out simultaneously with other catalytic hydrotreating reactions such as hydrodesulfurization (HDS), yet HDN is significantly less well-studied than HDS. This contribution provides an overview of the heterogeneous HDN process, then outlines various homogeneous models for hydrodenitrogenation catalysis including binding modes of HDN substrates, catalytic hydrogenation processes and recent C--N bond cleavage reactions of nitrogen heterocycles. Emphasis is placed on aryloxide and alkoxide complexes of the early metals that afford some of the best homogeneous models for hydrodenitrogenation catalysis to date. (C) 1997 Elsevier Science Ltd.