Thermodynamics of the hydrodenitrogenation of carbazole

A thermodynamic analysis, based on accurate experimental Gibbs energies of formation, was completed for the key hydrogen-consuming steps in the HDN reaction network for carbazole. The results were compared with literature reaction studies. The concept of crossover temperature'' is shown to be a valuable tool in the interpretation of literature reaction-study results. Methods of nitrogen removal from aromatic materials are discussed in light of the findings of the thermodynamic analysis. It is concluded that the removal of nitrogen from heterocyclic aromatic nitrogen-containing compounds with conventional hydrodesulfurization catalysts, temperatures, and hydrogen pressures occurs under thermodynamic control'' with unavoidably high hydrogen consumption. The report also concludes that to reduce hydrogen consumption in the HDN of carbazole, pathways via 1,2,3,4a,9a-hexahydrocarbazole must be followed. Conditions under which these processes are possible are discussed. 36 refs., 9 figs.