Abstract
The decomposition of model molecules reacting alone or in competition was studied in a fixed bed reactor at 623 K and 7 MPa over a sulfided NiMo/Al{sub 2}O{sub 3} catalyst. The inhibiting effect of H{sub 2}S and some nitrogen molecules, namely quinoline type compounds plays a major role in the transformation of anilines intermediates. On the other hand H{sub 2}S acts as a cocatalyst and promote carbon-nitrogen bond cleavage, specially at low H{sub 2}S partial pressure. When the H{sub 2}S partial pressure is greater than the nitrogen compound partial pressure an inhibiting effect of H{sub 2}S occurs and its promoting effect on carbon-nitrogen bond cleavage is cancelled. Hydrogen has a positive but moderate effect in hydrogenation steps. The mechanism of carbon-nitrogen bond scission depends on the structure of the nitrogen molecule namely on the hybridization of the carbon atom bearing the nitrogen atom. If the carbon a with respect to the nitrogen is monosubstituted the mechanism is essentially a nucleophilic substitution. When the degree of substitution increases the elimination mechanism becomes more important and the two mechanisms are in competition. With a sulfided catalyst, H{sub 2}S from the gas phase doesn`t change the importance of each mechanism, it just increases
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Citation Formats
D`Araujo, P A.P.
Hydrodenitrogenation mechanism of aromatic amines. Kinetic study and simulation; Mecanisme de l`hydrodesazotation d`amines aromatiques. Etude cinetique et modelisation.
France: N. p.,
1994.
Web.
D`Araujo, P A.P.
Hydrodenitrogenation mechanism of aromatic amines. Kinetic study and simulation; Mecanisme de l`hydrodesazotation d`amines aromatiques. Etude cinetique et modelisation.
France.
D`Araujo, P A.P.
1994.
"Hydrodenitrogenation mechanism of aromatic amines. Kinetic study and simulation; Mecanisme de l`hydrodesazotation d`amines aromatiques. Etude cinetique et modelisation."
France.
@misc{etde_10113205,
title = {Hydrodenitrogenation mechanism of aromatic amines. Kinetic study and simulation; Mecanisme de l`hydrodesazotation d`amines aromatiques. Etude cinetique et modelisation}
author = {D`Araujo, P A.P.}
abstractNote = {The decomposition of model molecules reacting alone or in competition was studied in a fixed bed reactor at 623 K and 7 MPa over a sulfided NiMo/Al{sub 2}O{sub 3} catalyst. The inhibiting effect of H{sub 2}S and some nitrogen molecules, namely quinoline type compounds plays a major role in the transformation of anilines intermediates. On the other hand H{sub 2}S acts as a cocatalyst and promote carbon-nitrogen bond cleavage, specially at low H{sub 2}S partial pressure. When the H{sub 2}S partial pressure is greater than the nitrogen compound partial pressure an inhibiting effect of H{sub 2}S occurs and its promoting effect on carbon-nitrogen bond cleavage is cancelled. Hydrogen has a positive but moderate effect in hydrogenation steps. The mechanism of carbon-nitrogen bond scission depends on the structure of the nitrogen molecule namely on the hybridization of the carbon atom bearing the nitrogen atom. If the carbon a with respect to the nitrogen is monosubstituted the mechanism is essentially a nucleophilic substitution. When the degree of substitution increases the elimination mechanism becomes more important and the two mechanisms are in competition. With a sulfided catalyst, H{sub 2}S from the gas phase doesn`t change the importance of each mechanism, it just increases the rate of the reaction. In the presence of an oxide catalyst the contribution of the two mechanisms change. This result shows the importance of the sulphur species from the surface. The sites able to dissociate H{sub 2}S and H{sub 2} are the same, and the dissociation is of heterolytic nature. The kinetic modeling of using the CHEMKIN/SURFACE CHEMKIN package seems to be a convenient method in order to understand the kinetic and mechanistic phenomena in hydrodenitrogenation. The preliminary simulations in the case of 2.6 diethylaniline showed that only one type of site is not sufficient to account for the experimental results. Further simulations will be necessary.}
place = {France}
year = {1994}
month = {Jun}
}
title = {Hydrodenitrogenation mechanism of aromatic amines. Kinetic study and simulation; Mecanisme de l`hydrodesazotation d`amines aromatiques. Etude cinetique et modelisation}
author = {D`Araujo, P A.P.}
abstractNote = {The decomposition of model molecules reacting alone or in competition was studied in a fixed bed reactor at 623 K and 7 MPa over a sulfided NiMo/Al{sub 2}O{sub 3} catalyst. The inhibiting effect of H{sub 2}S and some nitrogen molecules, namely quinoline type compounds plays a major role in the transformation of anilines intermediates. On the other hand H{sub 2}S acts as a cocatalyst and promote carbon-nitrogen bond cleavage, specially at low H{sub 2}S partial pressure. When the H{sub 2}S partial pressure is greater than the nitrogen compound partial pressure an inhibiting effect of H{sub 2}S occurs and its promoting effect on carbon-nitrogen bond cleavage is cancelled. Hydrogen has a positive but moderate effect in hydrogenation steps. The mechanism of carbon-nitrogen bond scission depends on the structure of the nitrogen molecule namely on the hybridization of the carbon atom bearing the nitrogen atom. If the carbon a with respect to the nitrogen is monosubstituted the mechanism is essentially a nucleophilic substitution. When the degree of substitution increases the elimination mechanism becomes more important and the two mechanisms are in competition. With a sulfided catalyst, H{sub 2}S from the gas phase doesn`t change the importance of each mechanism, it just increases the rate of the reaction. In the presence of an oxide catalyst the contribution of the two mechanisms change. This result shows the importance of the sulphur species from the surface. The sites able to dissociate H{sub 2}S and H{sub 2} are the same, and the dissociation is of heterolytic nature. The kinetic modeling of using the CHEMKIN/SURFACE CHEMKIN package seems to be a convenient method in order to understand the kinetic and mechanistic phenomena in hydrodenitrogenation. The preliminary simulations in the case of 2.6 diethylaniline showed that only one type of site is not sufficient to account for the experimental results. Further simulations will be necessary.}
place = {France}
year = {1994}
month = {Jun}
}