Electrochemical Construction of Hydrogenation System Using Active Hydrogen at Hydrogen Storage Alloy/Gas Interphase

从这项工作中获得的信息可以概括如下。MmNi_<4.2>Al_<0.5>M_<0.3> （Mm=misch metal， M=Cr, Mn, Fe, Co, Ni）合金中氢的扩散系数（Einstein扩散系数）随着M原子半径的增大而减小，这是由于其吸收氢的稳定性增强所致。此外，无论x值如何，在Mm(B_5)_x （B_5=Ni_<3.6>Mn_<0.4>Al_<0.3>Co_<0.7>,0.8*x*1.12）合金电极上的析氢反应均通过Volmer-Tafel机制进行。x值的增大有效地抑制了Tafel反应，促进了合金的吸氢。采用Pd片电极分离的双室池，构建了一种新型的乙烯加氢连续系统。经过适当的诱导期后，乙苯的产量呈线性增加，目前乙苯的生产效率在90%以上。电解水时，随着电流密度的增加，乙苯的产率也随之增加。采用快速淬火法制备的储氢合金片电极也可构建加氢体系。上述加氢体系可适用于α -甲基斯蒂烯、1-辛烯、2-辛烯和环己烯的加氢，加氢速率依次为环己烯<2-辛烯< α -甲基斯蒂烯<1-辛烯<斯蒂烯。气态不饱和有机化合物乙炔也进行加氢反应，由乙炔生成乙烷。Pd黑具有较高的加氢催化活性，可以通过Pd^<2+>与通过Pd片电极的活性氢反应生成三维的Pd黑。钯化Pd片电极与钯化Pd片电极相比，4-甲基乙烯和2-辛烯的加氢速率显著提高。

The information obtained from this work can be summarized as follows.1. Hydrogen diffusion coefficient (Einstein diffusion coefficient) in MmNi_<4.2>Al_<0.5>M_<0.3> (Mm=misch metal, M=Cr, Mn, Fe, Co, Ni) alloys decreases with an increase in atomic radius of M because of enhanced stability of absorbed hydrogen in them. In addition, hydrogen evolution reaction at Mm(B_5)_x (B_5=Ni_<3.6>Mn_<0.4>Al_<0.3>Co_<0.7>,0.8*x*1.12) alloy electrodes proceeds via the Volmer-Tafel mechanism irrespective of x value. An increase in x value depresses the Tafel reaction effectively, leading to promotion of hydrogen absorption in the alloys.2. A new successive system for hydrogenation of stirene was constructed using a two-compartment cell separated by a Pd sheet electrode. The amount of produced ethylbenzene increases linearly after an appropriate induction period and current efficiency for ethylbenzene production is over 90%. The rate of ethylbenzene production increases with an increase in current density for electrolysis of water. The hydrogenation system can be also constructed by using hydrogen storage alloy sheet electrodes prepared by rapid-quenching method.3. The above-mentioned hydrogenation system can be applied to the hydrogenation of alpha-methylstirene, 1-octene, 2-octene and cyclohexene, and the hydrogenation rate increases in the order of cyclohexene<2-octene<alpha-methylstirene<1-octene<stirene. The hydrogenation of acetylene, gaseous unsaturated organic compound, also proceeds and ethane is produced via ethylene.4. Pd black, which is well-known to show high catalytic activity for the hydrogenation, can be deposited three-dimensionally by a reaction of Pd^<2+> with active hydrogen passing through a Pd sheet electrode. The hydrogenation rates of 4-methylstirene and 2-octene using a palladinized Pd sheet electrode increase markedly in comparison with those using a Pd sheet electrode.