非负载型磷化钼加氢精制催化剂的研制

 尽管有相当多的文献和专利报道了含磷加氢精制催化剂的研究及磷的加入对Mn-Ni、Ni-Mo、Ni-W、Co-Mo、Mo、W、Ni、Co等各类加氢精制催化剂结构、及HDS、HDN活性的影响，并证明了磷或含磷化合物可作为加氢精制催化剂的助剂和稳定剂，但对于磷化物加氢催化剂的合成及对其HDS、HDN活性的研究还很少。本文在较低温度下用氢气直接还原磷钼酸铵盐得到非负载型的磷化钼催化剂，并以制备的磷化钼为活性组分，以SiC和γ-Al2O3为稀释剂，选择高浓度和低浓度的吡啶、噻吩和环己烯的混合物为模型化合物，以环己烷作溶剂，测定了制备催化剂的HDS、HDN及HYD活性。结果表明，所研制的非负载型磷化钼加氢精制催化剂对两种含有吡啶、噻吩和环己烯的模型化合物具有同时HDN, HDS 和 HYD的性能。     

High-field transport in semiconductor superlattices for interacting Wannier–Stark levels

We developed a microscopic theory of electron transport in superlattices within the Wannier–Stark approach by including the interaction associated with Zener tunneling between the energy levels pertaining to adjacent quantum wells. By using a Monte Carlo technique we have simulated the hopping motion associated with absorption and emission of polar optical phonons and determined the main transport parameters for the case of a GaAs/GaAlAs structure at room temperature. Interaction between the levels is found to be responsible for a systematic increase of the level energy with respect to the bottom of the quantum well at electric fields above about 20 kV/cm. When compared with the non-interacting case, at the highest fields the average carrier energy evidences a consistent increase, which leads to a significant softening of the negative slope of both the drift velocity and diffusivity versus electric field behavior.