Nano-alkali Metal Hydrides, Chemical Reaction Activity

Nano-alkali metal hydrides can be prepared easily by the direct hydrogenation catalyzed by TiCl4 in tetrahydrofunan (THF) under normal pressure. Lanthanide powder of nanometric size in a finely dispersed active form was generated by the thermal decomposition of organolanthanide in vacuum.1. Using nano-LiH and nano-NaH as reducers, in refluxing THF and under normal pressure, cinnamaldehyde were selectively reduced to cinnamyl alcohol with selectivities of 99 % at higher conversions. Changing reaction temperature or the molar ratio between reactants and cinnamaldehyde can improve the selectivities and conversions. In addition, the sequence of the reactants is another factor to affect the selectivity and conversion in this reaction.2. Four kinds of model reactions were employed to draw comparisons of initial reaction rates between nano-NaH and the commercial one. The experimental results indicate that the initial reaction rates of nano-NaH are several orders of magnitude higher than those of the commercial one. The large specific surface area and the high surface energy of nano-NaH should be the main factors for their extremely high chemical reactivity. With nano-NaH, many reactions can be carried out efficiently.3.The hydrogenation of 1-hexene was catalyzed by titanocenes with various substituted groups in combination with nanometric sodium hydride. When the steric hindrance is large (for instance , five-membered ring or six-membered ring), the titanium complex gives lower initial catalytic activity but better stability. Only the terminal olefin could be hydrogenated by using this kind of catalytic system. Isomerization of olefins did not occur in the course of hydrogenation.