聚磷链和聚氮链的自洽场晶体轨道研究

利用自治场全略微分重叠晶体轨道方法(SCFCNDO/2-CO)对聚磷链和聚氮链的各种可能构型的稳定性、能带结构和电子特性进行了研究.结果表明,本征聚磷链为半导体,而本征聚氮链为绝缘体.     

New Solution Method of Pi-Orbital Axis Vector and Its Applications in Fullerenes and Carbon Nanotubes

A new solution method to perform the pi-orbital axis vector analysis was developed in this paper. The model of circular cone was built and the solution equations of the pyramidalization angle were obtained based on the model and the space analytic geometry. Our method merely requires the atomic coordinates of the conjugated central atom and the three attached atoms. Moreover, systematic calculations on the pyramidalization angles of fullerenes and carbon nanotubes were performed using the method we developed. The relationship of pyramidalization angle and the stability for the carbon cages and tubes was also discussed.     

结构原子组成对Keggin型杂多酸铯盐上丙烷选择氧化性能的影响

系统地研究了具有不同结构原子组成的Keggin型杂多酸铯盐上丙烷选择氧化性能,重点考察了H3+n-xCsxPMo12-nVnO40(n=0-4,x=0-3)系列化合物以及H0.5Cs2.5PW12O40,H1.5Cs2.5PW11VO40和H1.5Cs2.5SiMo12O40样品.应用BET,UV-Vis,FTIR,XRD,TPR和SEM等手段研究了催化剂的物化性质.V取代Mo增加了H3+nPMo12-nVnO40(n=0-4)系列杂多酸的酸量和氧化性能.Cs+对质子的取代调变了样品的表面酸性以及氧化还原性,同时催化剂的热稳定性也随着Cs+取代数的递增而增强,当Cs+的取代数达到2以上时催化剂的热稳定性较好.Cs+取代对H3+n-xCsxPMo12-nVnO40(n=0-4,x=0-3)催化剂上丙烷选择氧化性能有重要影响.随着一级结构中V5+取代数目的增多,可能的Cs+取代数目相应减少;而对丙烯酸的选择性则存在一适宜的Cs+取代数目.Keggin型杂多阴离子的结构原子组成及平衡离子的种类和数量决定了其酸性、氧化还原性和热稳定性,这是影响该类催化剂上丙烷选择氧化性能的首要因素.研究结果表明,以P为中心原子,以Mo和V为配位原子的杂多酸铯盐[x(Cs+)=2.5]具有较好的催化性能.