C. Sayag

Kinetic study of the hydrodenitrogenation of carbazole over bulk molybdenum carbide

Abstract Hydrodenitrogenation (HDN) of N-containing compounds (carbazole in this paper) in the presence of a small amount of sulfur (50 ppm) requires a strong catalytic hydrogenating function. Bulk molybdenum carbide, Mo 2 C, behaves like a noble metal and has strong hydrogenating properties and can catalyse deep HDN if the S content is not too high. A kinetic investigation monitored both the hydrogenating function through carbazole consumption and the HDN of carbazole through two kinetically coupled cycles. Biphenyl was not observed. Kinetic coupling occurs by means of adsorbed orthocyclohexylaniline. The first route is the direct HDN reaction, leading to cyclohexylbenzene, while the second hydrogenation route leads to bicyclohexyl. At 633 K, a zero-order reaction is observed with respect to carbazole; total HDN is observed for 0.4 s, and the selectivity ratio of bicyclohexyl to cyclohexylbenzene is equal to 9.

HDN of 1–4 tetrahydroquinoline over MoNxOy and NbNxOy: effect of transition metal, solvent and ammonia

Oxynitrides of early transition metals are bifunctional catalysts active in hydrodenitrogenation (HDN). The strength of the hydrogenating function and the acidic properties of molybdenum and niobium oxynitrides were investigated, as well as the inhibiting effect of ammonia and the effect of solvent (cyclohexane or tetradecane) on HDN of 1,2,3,4‐tetrahydroquinoline (1–4 THQ). Even under high hydrogen pressure (4.5 MPa) the reaction was found to be able to proceed without hydrogenation of the aromatic cycle of 1–4 THQ before C–N bond scission, which is not the case over sulfided NiMo supported catalysts in HDN. Experiments in presence of ammonia permitted to support a bifunctional dual site concept.

Chemical alteration of coals and their reactivity with tetralin and methanol under liquefaction conditions

Abstract The effect was studied of pretreatment techniques, including O-methylation with (CH 3 ) 2 SO 4 , reduction with both K-isopropanol in THF and LiAlH 4 , reductive methylation with KCH 3 I in THF and combination thereof, on the extractability in THF of coals of different rank and on their reactivity in non-catalytic hydroliquefaction in methanol and tetralin at 380 °C. Dramatic changes in composition of the treated coals and products were found. Chemical pretreatment had a beneficial effect on coal solubility in THF and on hydroliquefaction in tetralin. O-methylation was the most effective for lignite, but reductive methylation had the most beneficial effect for high-rank coal. With methanol as solvent, reduction and O-methylation had a small effect on coal reactivity for liquefaction. The role of cross-links is discussed in order to explain the liquefaction behaviour of coals in solvents.