Investigating the mechanism of the selective hydrogenation reaction of cinnamaldehyde catalyzed by Pt-n clusters

摘要

Cinnamaldehyde (CAL) belongs to the group of aromatic alpha,beta-unsaturated aldehydes; the selective hydrogenation of CAL plays an important role in the fine chemical and pharmaceutical industries. Using Pt-n clusters as catalytic models, we studied the selective hydrogenation reaction mechanism for CAL catalyzed by Pt-n (n = 6, 10, 14, 18) clusters by means of B3LYP in density functional theory at the 6-31+ G(d) level (the LanL2DZ extra basis set was used for the Pt atom). The rationality of the transition state was proved by vibration frequency analysis and intrinsic reaction coordinate computation. Moreover, atoms in molecules theory and nature bond orbital theory were applied to discuss the interaction among orbitals and the bonding characteristics. The results indicate that three kinds of products, namely 3-phenylpropyl aldehyde, 3-phenyl allyl alcohol and cinnamyl alcohol, are produced in the selective hydrogenation reaction catalyzed by Pt-n clusters; each pathway possesses two reaction channels. Pt-n clusters are more likely to catalyze the activation and hydrogenation of the C = O bond in CAL molecules, eventually producing cinnamic alcohol, which proves that Pt-n clusters have a strong reaction selectivity to catalyze CAL. The reaction selectivity of the catalyzer cluster is closely related to the size of the Pt-n cluster, with Pt-14 clusters having the greatest reaction selectivity.