Adsorption and phase equilibria for hydrogen storage system based on dehydrogenation reaction of naphthenes, and its process design

Abstract

A hydrogen storage medium, using a dehydrogenation reaction of naphthene in a membrane reactor, is proposed for fuel cell systems. In this system, the permeation rate of hydrogen is not high so that the residual hydrogen, not passing through the membrane, must be recovered. A gas-liquid separator and an adsorption column were evaluated. For the design of the separator, the hydrogen solubility has been already reported for aromatic hydrocarbon, naphthenes, and equimolar mixtures. In this study, adsorption on activated carbon was measured in hydrogen flow saturated with pure benzene, cyclohexane, methycyclohexane, and toluene, and the equimolar mixtures, benzene+cyclohexane and methycyclohexane+toluene. The measurement was carried out by a new apparatus specially designed for this study, based on a flow type method, and equipped with gas chromatograph with both FID and TCD. In the measurement, the breakthrough curve and the specific mass adsorbed were measured at 347 kPa and 303.15 K. The adsorption mechanism was also discussed based on the breakthrough curves for the pure adsorbates and mixtures. Finally, the required mass of adsorbate, activated carbon, was estimated for the system by assuming the reaction rate and the hydrogen permeation ratio in the membrane reactor.