Pd-γAl2O3 applied to triglycerides hydrogenation with supercritical propane: Experimental and theoretical catalysts characterization

A set of Pd-γAl2O3 catalysts of different metallic particle sizes and modified with 2-chloro-butane was used for triglyceride hydrogenation. The experiments were carried out in single-phase conditions using propane as a supercritical solvent. A generalized criterion was used to determine the absence of mass-transfer limitations for both reactants inside the pore structure of the catalyst.FTIR spectra of CO on diverse catalysts showed different absorption bands and significant shifts to higher wavelengths of the CO species corresponding to on-top and bridge configurations. In order to test these results, theoretical studies using the density functional theory (DFT) were carried out for the FTIR of CO adsorption on two Pd ensembles, with or without charge deficiency and with Cl adsorbed on them. The results showed similar displacements of the band frequencies to those obtained experimentally, and demonstrate an enhancement of the CO adsorption energy of the on-top, isolated bridge and three-fold bridge CO species on electron deficient ensembles. Enhancement of the adsorption bond strength could promote the direct hydrogenation of the diunsaturated compound to complete saturated fatty acid chains. The decrease of the specific reaction rate (TOF) and the increase of the saturated fatty acids production, as well as a decrease of the monounsaturated and isomers content observed is in line with a possible modification of the electronic properties of the Pd particles. The influence of some planes of Pd clusters intervening on the direct hydrogenation is discussed.

Pd-γAl2O3 catalysts with different metallic particle size and modified with Cl were used in the triglyceride hydrogenation. The experiences were carried out in homogeneous-phase conditions using supercritical propane. FTIR spectra's and DFT calculations evidenced the enhancement of the CO adsorption energy due to the presence of electro deficient ensembles. These lasts could promote the modification of the reaction selectivity and (TOF) values.Figure optionsDownload as PowerPoint slide