Kinetics of liquid phase cyclohexene hydrogenation on Pd–Al/biomorphic carbon catalysts

• Pd–Al/biomorphic carbon catalysts are active for liquid-phase hydrogenation reactions.
• Pd–Al/BC catalysts are prepared by a reactive technique under reductive atmosphere at high temperature.
• In situ real-time Raman probe technique is a powerful tool to follow liquid-phase hydrogenation reactions.
• The kinetic model developed considers the existence of two types of metallic sites on the Pd surface and non-competitive adsorption.
• The values of apparent kinetic orders and activation energy of the power-law model, depend on the operating conditions.

The biomorphic mineralization technique is a powerful tool that allows to synthetize inorganic materials using as templates some structures of biological origin. This work presents kinetics results obtained during the liquid-phase hydrogenation of cyclohexene using a novel Pd–Al catalyst supported on biomorphic carbon.The catalysts have been prepared by a reactive method, using cellulose as carbonaceous precursor of the biomorphic support. The influence of the time and decomposition temperature (600–800 °C) of cellulose under hydrogen atmosphere has been studied. The characterization results indicate that the synthesis of these biomorphic materials produce solids with high microporosity. The metallic dispersion of the Pd nanoparticles is strongly dependent on the preparation conditions (i.e. heating rate, thermal decomposition temperature and time) of the carbonaceous precursor.The kinetic study has covered the effect of the hydrogen pressure and temperature, and was carried out using a real-time in situ Raman probe. The developed kinetic model considers the non-competitive adsorption between hydrogen and cyclohexene in two different types of Pd metallic sites. The model explains all the experimental results obtained, providing a rational explanation for the variation of the kinetic orders and apparent activation energy obtained using the empirical power-law model.

Evolution along time of in situ Raman spectra and cyclohexene conversion.Figure optionsDownload high-quality image (162 K)Download as PowerPoint slide