Preparation And Applications Of Polycarboxylic Acids-functionalized Non-magnetic And Magnetic Silica Materials

Hydrosilylation of alkene is a crucial reaction to provide access to organo-functional silanes and silicones,which are commonly applied in the fields of national defense,machinery,electrical,medicine and agriculture.The hydrosilylation reaction is usually activated by homogeneous Pt catalysts.However,there are lots of disadvantages for the homogeneous Pt catalysts?such as poor selectivity,non-reusability?.Therefore,a series of nonmagnetic and magnetic poly-carboxyl acids modified silica gel supported Pt catalysts were prepared and applied to the hydrosilylation of olefins.Furthermore,the magnetic polycarboxyl modified silica materials were applied to the separation of Cu???in aqueous solution.?1?Three novel poly-carboxylic acids functionalized silica gel supported Pt catalysts?SiO₂-DTPA-Pt,SiO₂-NTA-Pt and SiO₂-SA-Pt?were prepared in this research and were characterized by infrared spectroscopy?IR?,transmission electron microscopy?TEM?,X-ray photoelectron spectroscopy?XPS?,energy dispersive X-ray spectrometer?EDS?,and atomic absorption spectroscopy?AAS?.Then,the catalytic activities for these three novel Pt catalysts were evaluated using the hydrosilylation reaction of 1-hexene with methyldichlorosilane as the model reaction.The prepared conditions were investigated and the results indicated that the yield of the product catalyzed by SiO₂-DTPA-Pt reached to 99.6%as the immobilized temperature was 78^oC while the solvent was anhydrous ethanol.Then,the catalytic performance of SiO₂-DTPA-Pt was compared with that of SiO₂-NTA-Pt and SiO₂-SA-Pt.?2?The catalytic conditions were also investigated.The results indicated these three Pt catalysts showed high selectivity and activity for the alkenes hydrosilylation.Based on this,some hydrosilylation reactions between other linear alkenes or ring type alkenes with methyldichlorosilane catalyzed by these three Pt catalysts were also investigated.These three Pt catalysts also showed high activity and selectivity for other alkenes hydrosilylation,which were better than the homogeneous Pt catalyst.In addition,SiO₂-DTPA-Pt showed the highest reusability for thirteen catalytic runs with a small loss in the yield of the product under the optimal conditions.?3?In order to simplify the separated steps for the traditional immobilized Pt catalysts,thepoly-carboxylicacidsfunctionalizedmagneticsilica?Fe₃O₄@SiO₂-DTPA and Fe₃O₄@SiO₂-NTA?were synthesized.These two magnetic materials were characterized by IR,TEM,SEM,EDS,XPS,TGA,XRD and magnetic analysis.Then,they were applied to the field of Pt catalyst and the adsorption of Cu???from aqueous solution.For the immobilized Pt catalysts,we investigated the effect of the catalytic conditions on the catalytic activity for Fe₃O₄@SiO₂-DTPA-Pt and Fe₃O₄@SiO₂-NTA-Pt.In addition,the applicability and reusability of these two magnetic Pt catalysts were also investigated under the optimal conditions.The results showed that these two magnetic Pt catalysts also had high activity and selectivity for the alkenes hydrosilylation.Furthermore,Fe₃O₄@SiO₂-DTPA-Pt showed more active after reused for 10 times.For Cu???adsorption,the effect of the adsorption conditions,the research of the adsorption kinetics and thermodynamics were investigated.