Preparation Of Pt Nanocrystals And Their Catalytic Properties For Ring Opening Of Decalin

In recent years，it has been a focus to study selective ring opening of polycyclicalkanes aiming to improve cetane number of diesel fuels. Catalyst activity andproduct selectivity depends on the size and morphology of active metal. In order toimprove ring opening selectivity of decalin, a systematical study on preparation ofmorphology-controlled Pt nanocrystals has been carried out. Then we investigated theinfluence of morphology and size of Pt nanocrystals on hydrogenation and ringopening of decalin.First，a preliminary study on synthesis of monodisperse Pt nanocrystals wasexplored. Ethylene glycol(EG), sodium borohydride and CO were used as reductantsrespectively. Pt nanocrystals with tunable size were obtained by changing Pt(IV)/Pt(II)ratio of metal precursors in EG solution. The particle size decreased as Pt(IV)incrementally replaced by Pt(II). Larger Pt nanocrystals were synthesized usingsodium borohydride as a reductant, and hydrogen was proved to play a key role tocontrol the morphology of Pt nanocrystals. Well monodispersed oil-soluble Pt cubeswere prepared using CO as a reductant and adsorbate in oleylamine solution.Water-soluble Pt cubes and truncated octahedrons with controllable size wereobtained in a EG-PVP system in the presence of amines with different chain length.Removal methods of surfactants on Pt nanoparticles was investigated. A fixedbed reactor was used for ring opening of decalin over Pt/USY and Pt/CNT-USYbifunctional catalysts. The reaction temperature varied between200°C and380°C,and the hydrogen pressure kept at4.0MPa. Surfactants can be removed moreeffectively by calcinating in air than refluxing in hot water. Under higher calcinationtemperature, the catalytic activity increased with less surfactants residues but moreaggregating of Pt particles. The optimal calcination temperature was235°C.Pt/CNT-USY showed higher catalytic activity than Pt/USY. Increased catalyticactivity of Pt/CNT-USY and yield of ring opening products were obtained whensmaller Pt particles were used. Pt {111} facets showed higher catalytic activity andring opening selectivity.