Hydrogen Storage with Metal Hydrides

Metals, intermetallic compounds, and alloys generally react with hydrogen and form mainly solid metal-hydrogen compounds (MH ). Hydrides exist as ionic, polymeric covalent, volatile covalent and metallic hydrides. Hydrogen reacts at elevated temperatrrres with many transition metals and their alloys to form hydrides. Many of the MH show large deviations from ideal stoichiometry (n= 1, 2, 3) and can exist as multiphase systems. 

When hydrogen combines with the metal alloy (in granular form or particles), an exothermic reaction occurs. The gas is thus stored in these metal particles until some heat is applied to release the hydrogen and build up the pressure in the tanks. When a metal hydride absorbs hydrogen, heat is given off. A hydride cold-start heater can be developed that instantly heats an automobile s catalytic converter when the car is started to dramatically reduce overall exhaust pollution up to 80%. 

Metal hydrides generate hydrogen gas via reversible pyrolysis reactions, i.e., 2M + nH, 5 2MH + Heat (5.48) 

Hydrolysis is defined as the reaction of a hydride with water to liberate hydrogen gas. The reactions are as follows (Fakioglu et al., 2004)  

There are two classes of hydrides metallic hydrides and complex hydrides. The main difference between these two is the transition of metals to ionic or cova- 

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The EU "STORMY" program aims to develop the next generation of compressed and liquefied hydrogen storage and metal hydrides. The EU consortium includes about 40 partners including car industry players. The program is support with a 10 million budget... 

The different techniques, together with the corresponding detectors and the experimental vessels, can be adapted and adjusted to the investigations of new materials or new processes. This is the case for example with the research on hydrogen storage on metal hydrides, all the works related to the capture and sequestration of CO2 with the evaluation of solid and liquid sorbents, the development of the Chemical Looping Combustion with improved catalysts... 

With support from the U.S. DOE hydrogen program, ECD has demonstrated the viability of H-ICE scooters with metal hydride for on-board hydrogen storage. Hydrogen fueled small ICE vehicles and distributed power generation devices... 

Among the many candidates of hydrogen transportation or seasonal storage methods, the H2 evolution from cyclohexanes at the demand site and the reverse reaction, the hydrogenation of benzene, at the supply site offers the advantages of safe and commonly used transport at ambient temperature in chemical tank ships or trucks and mild reaction conditions. Cyclohexanes have a hydrogen density and content comparable with metal hydrides [8]. Methylcyclohexane is the choice of preference, since unlike benzene, toluene is not carcinogenic. 

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