Kinetics of the one-pot transformation of citronellal to menthols on Ru/H-BEA catalysts

Temperature, pressure, and concentration variation experiments were conducted in the one-pot-transformation of citronellal to menthol with 1%Ru/H-BEA-25 as bifunctional catalyst. This reaction requires a combination of a cyclization and hydrogenation step, therefore the product distribution strongly depends on reaction conditions, especially on the reaction temperature. At lower temperatures the consecutive hydrogenation of citronellal prevails, whereas at high temperatures defunctionalization of menthols is favored leading to a maximum menthol yield at 373 K. A kinetic model was proposed based on a Langmuir–Hinshelwood mechanism and different active sites for cyclization and hydrogenation reactions. Kinetic parameters (reaction constants, activation energies, and adsorption coefficients) were estimated by using nonlinear regression.