Copper Substitute MCM-48 for the Selective Hydrogenation of Cinnamaldehyde in Liquid Phase

MARIANA DENNEHY; ALEJANDRA SOLEDAD DIEZ; VICTORIA SOLEDAD GUTIERREZ; MARÍA ALICIA VOLPE

Angra Dos Reis, RJ

Congreso; XIV BRAZILIAN MEETING ON INORGANIC CHEMISTRY; 2010

The selective hydrogenation of a,b-unsaturated compounds over heterogeneous catalysts has been extensively studied. Catalysts based on noble metals supported on alumina, silica or carbon were mainly studied[1-3]. An alternative to these traditional catalysts are the ones based on copper (a low cost metal). Besides, mesoporous oxides are excellent supports for the formulation of catalysts to be employed in liquid phase reactions, since their large channels allow free diffusion of reactants and products.   The present work deals with the synthesis and characterization (BET, XRD, FTIR, TPR, TEM) of Cu substituted MCM-48 catalysts. The samples are tested for the liquid phase hydrogenation of cinnamaldehyde, trying to obtain cinnamyl alcohol, the desired product from an industrial point of view.   Two ways are followed for preparing samples: a traditional hydrothermal synthesis [4], and a novel method from Cu(AcAc)2. In the latter case, the copper precursor is introduced to MCM-48 before removing the structure-directing agent (CTBA). The samples are tested in a Batch reactor, using H2 as the reductant and isopropanol as the solvent. Conversion and selectivity towards cinnamyl alcohol are measured. From both preparation methods, selective catalysts are obtained, however from Cu(AcAc)2 the metal loading in MCM-48 can be increased up to 10wt% without loosing the mesoporous structure (as measured from low angle XRD). For the catalysts obtained from the hydrothermal synthesis  copper loading higher than 5wt% leads to systems with low surface area (as measured by BET) and low ordered structure.   The selectivity of the Cu-MCM-48 catalysts is much higher (>40%) than the one corresponding to Cu/g-Al2O3 (<3%). The origin of the improved selectivity of mesoporous catalysts would be due to the fact that Copper is highly dispersed in MCM-48. Besides, the reducibility of copper species supported on MCM-48 is higher than the corresponding to conventional supports, as g-Al2O3.