Artículos de revistas
Liquid-Phase Hydrogenation of Methyl Oleate on a Ni/α-Al2O3 Catalyst: A Study on Kinetic Models Describing Extreme and Intermediate Adsorption Regimes
Cabrera, Maria Ines; Grau, Ricardo José Antonio; Liquid-Phase Hydrogenation of Methyl Oleate on a Ni/α-Al2O3 Catalyst: A Study on Kinetic Models Describing Extreme and Intermediate Adsorption Regimes; Elsevier Science; Journal of Molecular Catalysis A: Chemical; 260; 1-2; 12-2006; 269-279
Cabrera, Maria Ines
Grau, Ricardo José Antonio
The kinetics of the hydrogenation of methyl oleate on a Ni/alpha-Al2O3 catalyst was studied in the absence of mass-transport limitation, at 398=T=443K and 3.7=PH2 =6.5 bar. The kinetic modeling was performed on the basis of elementary step mechanisms involving different regimes of competition between hydrogen and methyl oleate. Admitting a distinction between occupied-sites and covered-sites by the large molecule of methyl oleate, a rigorous proposal was made to link the seemingly separate kinetic models corresponding to the extreme modes of competitive and non-competitive adsorption, without having to draw the common distinction between two types of surface sites. General rate equations were formulated without expressing opinion a priori on whether the adsorption regime is competitive or non-competitive. Then, typical LHHW rate equations for both extreme adsorption regimes were straightforwardly derived as special cases. Statistical results demonstrated the inadequacy of the models approaching non-competitive adsorption to describe the experimental data but results did not allow a definite discrimination between rival models with competitive and semi-competitive adsorption. A mechanistic model featuring dissociative adsorption of hydrogen, molecule of methyl oleate interacting with a single atom of Ni, and second insertion of hydrogen as RDS, proved to be the best candidate to describe the experimental data satisfactorily with physically reasonable parameters. As a distinctive feature, the model considering semi-competitive adsorption gave additional indication that the adsorbed molecule of methyl oleate could cover up to seven surface sites. From this finding, the semi-competitive model seems to be more realistic than the competitive one.