Selective hydrogenation of cinnamaldehyde in supercritical CO2 over Pt/SiO2 and Pt/HS-CeO2: An insight about the role of carbonyl interaction with supercritical CO2 or with ceria support sites in cinamyl alcohol selectivity

C. M. PIQUERAS; V. GUTIERREZ; D. A. VEGA; D. E. DAMIANI

APPLIED CATALYSIS A-GENERAL

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2013 vol. 467 p. 253 - 260

0926-860X

The catalytic hydrogenation of cinnamaldehyde employing H2as the reductant was carried out undersupercritical (sc) CO2, propane and other CO2dense mixture, employing Pt supported on silica and highsurface (HS) ceria. The phase behavior of the mixtures was found to be in good agreement with thepredictions obtained from the MHV2 (modified Huron-Vidal second-order) model. In order to study theinfluence of scCO2on the selectivity, the reaction was also conducted in dense propane and near-criticalCO2?isopropanol mixtures. These results were compared with those corresponding to classical gas?liquidconditions with isopropanol as solvent and low H2pressure. In scCO2, the selectivity to cinnamyl alco-hol over Pt/SiO2was 91%, quite higher than under classical conditions (38%). Such an enhancement isoriginated by the interaction of the C O with scCO2. For Pt/HS-CeO2the selectivity under supercriticalconditions was slightly lower (80%) than the one corresponding to Pt/SiO2but quite higher than the onecorresponding to gas?liquid conditions (54%). The interaction of the carbonyl group with ceria supportpredominates in this case, thus, the beneficial effect of scCO2is not observed in the same magnitudeas in the case of Pt/SiO2. A catalytic scenario is drawn for each catalyst in order to explain the differentselectivity patterns.