Chemical structure and catalytic activity of quaternary onium salt-type triphase catalysts based on CPS microspheres

摘要

In this work, diversified quaternary onium salt-type triphase catalysts (TPC) were prepared based on crosslinked polystyrene (CPS) microspheres, and the relationship between their chemical structures and catalytic activities in liquid-solid-liquid reaction system were investigated in depth by using the esterification reaction of benzyl chloride with sodium acetate as a model system. The experimental results indicate that the chemical structures of the TPC affect their catalytic activity greatly and there are four basic points: (1) the quaternary phosphonium-type TPC have higher activity than quaternary ammonium-type catalyst; (2) the TPC with more lipophilic substitutes at N atom have higher catalytic activity; (3) the TPC with longer spacer arm, which links quaternary onium salt group to the matrix microsphere, have higher catalytic activity; (4) the bonding density of quaternary onium salt group on the polymeric carrier affects the hydrophilic and hydrophobic property of the TPC, and consequently, influences the catalytic activity significantly. For a given triphase catalysis system, there is an optimal bonding density of quaternary onium salt group on the solid catalysts.