| Based on the review of the development of the metal amines, the alkaline earth metal chlorides were selected as the study object of this work. By means of XRD, FTIR, Raman and TPD, volumetic measurements, the ammonia storage perporties and the hydrogen storage performances and the mechanism of the MgCl2(NH3)6-18LiH mixture were systematically investiaged for developing a new type meatal ammine-complexes-based hydrogen storage materials with high capacity.The effects of the operation temperature, starting pressure, ball milling treatment and the addition of metal catalystes were systematically investigated. Results indicated that the ammonia absorption/desorbtion reactions of MgCl2 were completely reversible. The post-2 h milled sample can be fully ammoniated to form MgCl2(NH3)6 within 60 mins at 20℃and 0.4 MPa, and the ammonia storage capacity was 51.2wt.%, equivalent to be 9.1 wt.% of hydrogen. NH3 can be desorbed from MgCl2(NH3)6 in the temperature range of 100-330℃. The desobtion reaction can be divided into three stages, and controlled by temperature and pressure. Four NH3 molecules could be desorbed with the peak temperature of 160℃, then the fifth and sixth NH3 molecule released from the complexes with the peak temperature of 260℃and 320℃, respectively. Further investigations indicated that higher operation temperature and starting pressure can improve the ammonia absorption kinetics of MgCl2. Prolonging ball milling time can decrease the operation temperature for ammonia desorption of MgCl2(NH3)6 and improve its ammonia desorption kinetics. Doping with some metal catalysts (Co,Ti,Fe,Cu,Ni) can decrease the operation temperature for ammonia desorption of MgCl2(NH3)6 and improve its ammonia desorption kinetics. The operation temperature for ammonia desorption of the sample doped with 5% Co can be decreased by about 45℃.The investigations on the ammonia absorption/desorption properties of CaCl2 showed that the post-2 h milled sample can be fully ammoniated to form CaCl2(NH3)8 within 15 mins at 20℃and 0.55 Mpa, and the ammonia storage capacity was 55.1 wt.%, equivalent to be 9.72 wt.% of hydrogen. NH3 can be desorbed from CaCl2(NH3)8 in the temperature range of 20-300℃. The desobtion reaction had three stages, and it was controlled by temperature and pressure. Six NH3 molecules could be desorbed at room temperature and room pressure. Further investigations indicated that higher operation temperature and starting pressure can improve the ammonia absorption kinetics of CaCl2, and longer time ball milling can decrease the operation temperature for ammonia desorption of CaCl2(NH3)8 and improve its ammonia desorption kinetics.Based on the above investigations, the MgCl2(NH3)6-18LiH mixture was prepared by ball milling and its hydrogen desorption performances and the mechanism were systematically studied. Results indicated that the post-24 h milled sample could release 3.7 wt.% H2, equivalent to be six H2 molecules, and its dehydrogenation consisted of two stages within 20-350℃. It releasd about 1.2 wt.% H2 from 130℃to 200℃, equivalent to be two H2, and 2.4 wt.% H2 from 200℃-350℃, equivalent to be four H2. Totally -7.1wt% of hydrogen, equivalent to be 12 H2 molecules can be released from the MgCl2(NH3)6-18LiH mixture. The intermediate products of Mg(NH2)2 and LiNH2 were found by means of XRD and FTIR. By consideration of the amount of H2 release and the XRD and FTIR analyses, we deduced the mechanism of the dehydrogenation during the ball milling treatment and heating can be expressed as:...
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