Synthesis Of Hierarchical Porous Silica Supports And Their Applications For Supported Catalysts

Many catalysts need to be loaded on specific supports for better performance.Due to the low surface areas of heteropoly compounds,there are only a small number of active sites available on the surface of the catalysts,and it consequently causes low catalytic activities and high costs of the catalysts.To solve this problem,many attempts have been made to disperse HPCs on various supports with high surface areas.Most of the noble metal catalysts need to be loaded on supports to increase their active surface and reduce the amount of the metal.The synthesis and modification of hierarchical Si-containing materials were carried out in this study,and then they were used to support heteropoly acid or noble metal for the applications in the selective oxidation of methacrolein?MAL?and the hydrogenation of styrene.Three-dimensionally ordered macroporous?3DOM?SiO₂ was prepared by a colloidal templating method and used as the support of heteropoly acid for the selective oxidation of MAL to methacrylic acid?MAA?.3DOM SiO₂ with uniform morphology was prepared and the specific surface area was 141 m² g^-1.After heteropoly acid was supported,it was found that the addition of Cu or Cs as counter-ions can improve the catalytic property of the catalysts.Meanwhile,Mg,Al,Fe,Cu,V or Ti doped 3DOM SiO₂ were prepared,and the Cu-doped support corresponded to the best catalytic performance.The conversion of MAL and the selectivity to MAA were respectively 63%and 82%on HPVA/3DOM?5%Cu?-SiO₂.Characterizations results revealed that the improvement of the reducibility and the increase in specific surface area contributed to the enhancement of the catalytic performance.Hierarchical Ni₃Si₂O₅?OH?₄ microspheres were synthesized by a hydrothermal method.The effects of the process parameters on the phase composition and morphology of the products were investigated.The pure phase Ni₃Si₂O₅?OH?₄microspheres exhibited a specific surface area of 196 m² g^-1.When employed as the support of Pd catalyst,the as-prepared Pd/Ni₃Si₂O₅?OH?₄ catalyst indicated excellent catalytic activity for the hydrogenation of styrene under mild conditions with a conversion rate of 100%in 1 h.Moreover,the catalyst was reused for five cycles without loss of activity,revealing good recyclability as a supported catalyst.