金属Pt表面氢同位素解离吸附的热力学研究

基于电子与振动近似方法和密度泛函B3LYP理论,对氢原子采用6-311G"基函数,Pt选择赝势基组LanL2DZ,优化得到Pt-H和Pt-H2结构和微观性质,Pt-H分子平衡键长和谐振频率分别为0.1528nm和2336cm-1,与实验值一致.氢气分子吸附于Pt表面反应的Gibbs自由能⊿G0为正值,远大于解离反应⊿G0值,氢气在Pt表面不能以完整分子形式与Pt结合,易于解离成氢原子.计算了氢同位素在Pt表面解离反应的⊿S0,⊿H0,⊿G0和平衡压力,并导出它们与温度的关系.由⊿G=0kJ.mol-1计算得0.1MPa时H2,D2和T2的脱附温度分别为962K,919K和892K,大多数反应Pt-H(D或T)都能稳定存在.     

高压微波制备Pt／C催化剂的工艺研究

利用高压微波消解仪密闭带压、升温速率可控的特点,选择XC-72碳黑为载体,乙二醇为碳黑分散溶剂和还原剂,研究反应温度、升温速率、水含量、Pt含量及表面活性剂等工艺条件对Pt粒子尺寸及其分散度的影响．研究结果表明,快速升温到190℃、控制反应体系中水含量和Pt含量等工艺条件,可以得到Pt粒子平均粒径小于3．1nm的Pt／C催化剂,且Pt粒子分布均匀,无团聚．     

Pt在SAPO-11分子筛上的分散性研究

采用H2-TPR、NH3-TPD、H2脉冲化学吸附和H2-O2化学滴定等方法对Pt/SAPO-11催化剂上金属分散进行了表征，并与该催化剂制备因子及其正构烷烃骨架异构化反应性能进行关联。实验表明，以与NH3配位的阳离子形式制备的催化剂，Pt的分散效果最好；用低浓度浸渍液、多次浸渍的方式制备的催化剂，Pt的分散度高；Mn2+、Sm3+、Zn2+等作助剂和Pd-Pt复合浸渍可提高Pt的分散度。调整分子筛的酸量使之与金属含量达到平衡时，催化剂活性和选择性最佳。     

Density functional study of uranyl （VI） amidoxime complexes

Uranyl (VI) amidoxime complexes are investigated using relativistic density functional theory. The equilibrium structures, bond orders, and Mulliken populations of the complexes have been systematically investigated under a generalized gradient approximation (GGA). Comparison of (acet) uranyl amidoxime complexes ([UO₂(AO)_n]^2-n, 1 ≤ n ≤ 4) with available experimental data shows an excellent agreement. In addition, the U-O(1), U-O(3), C(1)-N(2), and C(3)-N(4) bond lengths of [UO₂(CH₃AO)₄]^2- are longer than experimental data by about 0.088, 0.05, 0.1, and 0.056 Å. The angles of N(3)-O(3)-U, O(2)-N(1)-C(1), N(3)-C(3)-N(4), N(4)-C(3)-C(4), and C(4)-C(3)-N(3) are different from each other, which are due to existing interaction between oxygen in uranyl and hydrogen in amino group. This interaction is found to be intra-molecular hydrogen bond. Studies on the bond orders, Mulliken charges, and Mulliken populations demonstrate that uranyl oxo group functions as hydrogen-bond acceptors and H atoms in ligands act as hydrogen-bond donors forming hydrogen bands within the complex.