Ca-N-H system

K. Tokoyoda, S. Hino, T. Ichikawa, K. Okamoto, H. Fujii, Hydrogen desorption/absorption properties of Li-Ca-N-H system , J. Alloys Compd. 439 (2007) 337-341. 

The Ca-N-H system possesses even more complicated properties. Hino et al. [34] reported the thermal desorption properties of the mixture of calcium amide (Ca(NH2)2) and calcium hydride (CaH2) with two different ratios (1 1 and 1 3) and the mixture of CaNH and CaH2 as shown in Figure 6.5. From this result, Ca(NH2)2 and CaH2 with the 1 3 ratio desorbs H2 gas by the following two-step reaction (3.5 and 2.1mass%, respectively) ... 

More recently, Hino et al. explored the Ca-N-H system starting from the amide, Ca(NH2)2 and focusing on the desorption process [79]. First synthesising calcium amide by ball milling CaH2 under ammonia gas, the decomposition product upon heating the amide at 350 °C was found to be calcium imide according to Eq. (16.16) ... 

In the presence of MgH2 however, and by analogy with the Li-N-H and Ca-N-H systems, the decomposition should evolve H2 in place of NH3 presumably, also by analogy, via the rapid reaction of the hydride with evolved NH3. Hence by changing the ratio of amide hydride, two outcomes are potentially possible (Eqs 16.20 and 16.21) ... 

The Na-Li-N-H [14], Mg-Na-N-H [39], Ca-Na-N-H [40], Mg-Ca-N-H [41, 42] and Mg-Ca-Li-N-H [43] systems have also been investigated, where the metal elements used in these works were mainly limited to the alkali and alkaline earth... 

The M-N-H systems are the composites of alkali or alkaline-earth based metal hydrides (LiH, NaH, MgHj, and CaHj) and amides (LiNH2, NaNHj, Mg(NH2)2, and Ca(NH2>2) [99-126]. Chen et al. reported on hydrogen absorption of a lithium nitride LisN as hydrogen storage material [99], in which reversible reactions of hydrogen absorption and desorption reactions proceed with the following two steps ... 

The catechol-based hgands 14 show fairly low selectivity similar to that of the unmodified system. In contrast, the biphenol-derived phosphites 17 gave excellent chemoselectivity. The best results were obtained with 17c, where a TOP of ca. 1900 h was achieved which is close to the maximum value of 2000 h The n-selectivity of 71% was also appreciable, corresponding to an n/iso ratio of 2.4. The substituents in the biphenol backbones in hgands 19 re-... 

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