戊二醛改性交联壳聚糖纳米纤维膜负载钯催化剂的制备及其催化性能研究

Immobilization of palladium on glutaraldehyde chemical modified chitosan fiber mat and its catalytic performance

以壳聚糖(CS)为基体聚合物、聚甲基丙烯酸(PMAA)为共纺聚合物,通过静电纺丝和热交联技术制备了具有良好形貌和稳定性的交联壳聚糖/聚甲基丙烯酸(CS/PMAA)纳米纤维膜,然后采用戊二醛对纤维进行化学改性后用于负载钯催化剂.采用扫描电镜(SEM)表征纤维膜的微观结构;通过扫描电子显微镜-能谱仪(SEM-EDS)和X-射线衍射仪(XRD)分析钯催化中心在纤维膜上的分布;采用红外光谱(FT-IR)表征戊二醛改性后纤维膜的化学结构变化;利用密度泛函理论(DFT)研究戊二醛改性对壳聚糖纤维膜与钯催化中心之间络合强度的影响.Sonogashira偶联反应催化结果显示,戊二醛改性有助于提高纤维膜负载钯催化剂的催化活性,且该催化剂在重复使用9次后,催化反应转化率和产率基本保持不变.

Using poly（methacrylic acid） （PMAA） as the coelectrospinning agent, well-defined chitosan/poly（methacrylic acid） （CS/PMAA） fiber mat was fabricated by electrospinning and crosslinked at 180 ℃ for 2 h, then chemically modified with glutaraldehyde to immobilize palladium species. The fiber morphologies were observed by scan- ning electron microscopy （SEM） and the dispersion of palladium species were analyzed by SEM-energy dispersive spectrometer （EDS） and X-ray diffraction （XRD）. The chemical modification of CS/PMAA fiber was characterized by fourier transform infrared spectroscopy （FT-IR） spectra. Density functional theory （DFT） calculation results demonstrate that the chemical modification can decrease the chelating strength between the CS/PMAA fiber and pal- ladium species. The catalytic performances of these novel chitosan fiber supported Pd catalysts were evaluated by Sonogashira coupling reaction. It is found that the glutaraldehyde modification can improve the catalytic activity of CS/PMAA fiber supported palladium catalyst. Moreover, this novel catalyst can be reused at least nine times with- out obvious loss of initial activity.