Recyclable Magnetic PT Catalysts In The Liquid-Phase Hydrogenation Of3-Methylcrotonaldehyde

3-Methylcrotonaldehyde (3-MeCal) is a typical a, p-unsaturated aldehydes having C=C and C=O conjugated double bonds. The half-hydrogenation product3-methylcrotonalcohol (3-MeCol) has a wide application in the production of perfumes and pesticides. Therefore, from both theoretical and application point of view, it is of great importance to develop active catalysts with high selectivity for C=O bond hydrogenation. Multi-walled carbon nanotubes (MCNT) possess some superior properties such as unique lumen structure, peculiar conductivity, good adsorption capability, and excellent chemical and thermal stability, which make them good supports to prepare catalysts with unique activity and selectivity in some catalytic reactions.In this thesis, multi-walled carbon nanotubes were used as supports to prepare Pt/MCNT catalysts with uniform and controlled Pt nanoparticle sizes, which were further used in the liquid-phase selective hydrogenation of3-MeCal to3-MeCol. XRD, SEM, TEM, and ICP techniques etc. were used to characterized the Pt catalysts. This thesis mainly consists of three parts as follows:1. Pt nanoparticles with uniform size of about2.5nm have been prepared by a two-phase water/toluene reduction method using toluene as solvent, H2PtCl4as precursor, sodium borohydride as reductant, and oleylamine as protector.2. Pt/MCNT catalysts with uniform sizes and high dispersion of Pt nanoparticles have been successfully prepared via a multi-step method by loading the beforehand Pt nanoparticles on MCNT. Effects of Pt loadings, reaction temperature, reaction pressure, and activation conditions of the catalysts on the liquid-phase hydrogenation of3-MeCal were investigated in detail. The reaction results indicate that the prepared Pt/MCNT catalysts exhibit a very high activity and selectivity, i.e. the selectivity for3-MeCol is up to90%at a conversion of3-MeCal of almost100%. 3. To achieve the facile recovery of catalysts from the liquid-phase reaction system, we design a series of magnetic Pt/Fe3O4-MCNT catalysts, which show good supermagnetic properties as well as good catalytic properties in the selective hydrogenation of3-MeCal. The magnetic catalysts can be facilely recovered from the liquid-phase reaction system under an external magnetic field. Moreover, the magnetic catalysts have good recyclability, showing no obviously degradation after five-cycle using.