Biomimetic Regulation Of Pt Nanocrystals: Morphology And Catalytic Activity For Hydrogenation

Catalytic hydrogenation reaction is an important means of processing petroleum chemical products because of its atom economy, good product quality, post-processing easily, reaction selectivity controllability. Aromatic amines have important applications in chemical engineering, macromolecule, medicine and biology. So it is necessary to selective catalytic reduction of the nitro with the integrity of other unsaturated bonds in the unsaturated aromatic compounds. Noble metal nanoparticles?NPs? have been used as catalyst for many reactions because of their good catalytic performance. Their catalytic activity and selectivity are lagerly related to their size and morphology.According to Gibbs-Wulff theory, we can effectively control the morphology and size of NPs. In this paper, Na BH₄ has been used to reduce different precursors of platinum?such as H₂ PtCl₆ and K₂ Pt Cl₄? to get Pt NPs in water solution. Different biomimetic molecules, including 3-hydroxybutyric acid, topic acid, DNA basic groups and their corresponding nucleoside, deoxynucleoside, nucleate and deoxyribonucleic, have been employed as capping agent to control the size and shape of Pt NPs. Moreover, Pt NPs are loaded on SBA-15 by two-step method?ultrasound? and in situ method?conventional precipitation? and used as catalyst.Moreover, different metal precursors have been reduced in the presence of NH₃·H₂O to prepare monometal or multi-metal nanocrystals with small size?less than 5nm? and homogeneous dispersion. The obtained metal NPs are used to catalyze the reaction of p-NIP reduction by Na BH₄. The apparent kinetic constant k1 is calculated based on the kinetic data and the size of NPs.The hydrogenation of p-nitrophenol?p-NIP? to p-aminophenol is one of the most used model reactions to evaluate the activity of catalyst. Herein, the reduction of p-NIP by Na BH₄ or H₂ has been used as model reaction to evaluate catalytic performance of the as-synthesized noble-metal nanoparticles. UV-vis spectroscopy is employed to detect the absorbance changing of p-NIP over time. To eliminate the resistance to diffusion as much as possible, experiments have been conducted at various agitation speeds. Then the experimental data are fitted to a Langmuir-Hinshelwood?L-H? model involving a surface reaction controlling mechanism for p-NIP hydrogenation. This model follows a dual-site adsorption with molecular adsorption of p-NIP and dissociative adsorption of hydrogen. A non-linear multivariable regression analysis is carried out for the kinetic data in order to obtain the best fitted parameters using a program written in MATLAB. Besides, the catalytic activity of SBA-15 supported Pt NPs has also been tested for p-NIP hydrogenation.