Kinetic study of the hydrogenation of trans-cinnamaldehyde over Ir/Nb2O5 catalysts

Abstract

The hydrogenation of trans-cinnamaldehyde was studied over Ir/Nb2O5catalysts reduced at 473 K (LTR) and 773 K (HTR). The catalysts were characterized by N2 physisorption at 77 K, H2 chemisorption, TPR, and TPD-NH3. Kinetic study of trans-cinnamaldehyde over Ir/Nb2O5 reduced at HTR was carried out in n-heptane at hydrogen pressures in the range of 0.48 to 0.98 MPa, the reaction temperatures were 323-363 K, catalyst loadings 0.1 to 0.3 g and cinnamaldehyde concentrations 0.025 to 0.1 M. Trans-cinnamaldehyde can be selectively hydrogenated to cinnamyl alcohol although the support acidity leads to the formation of byproducts. A Langmuir–Hinshelwood model with molecular adsorption of hydrogen non competitive with organic molecules and considering the surface reaction as the rate-controlling step provided the best fit of the experimental data.

Keywords

• Nb2O5
• hydrogenation
• trans-cinnamaldehyde
• SMSI effect
• Langmuir-Hinshelwood