Passive production of hydrogen from aqueous methanol solution using a combined packed bed of porous particles

The passive production of hydrogen by steam reforming of methanol was investigated, where the entire process from supply of source liquid to reaction was achieved stably and efficiently only by heating of a packed bed. When a combined packed bed with the bottom immersed in aqueous methanol solution was heated, a liquid-phase region, a two-phase region, and a dry region were formed along the tube axis. An upward flow of liquid and/or vapor was induced over the entire length. Gas containing primarily hydrogen produced by the steam reforming reaction of methanol flowed out of the top of the packed bed. The flow rate increased in proportion to the heating rate, which corresponded to a decrease in the liquid saturation of the two-phase region and a subsequent enhancement of the capillary force. The time response of the flow rate corresponded to the process of decrease in the liquid saturation due to evaporation. The composition of the vapor flowing into the dry region was consistent with that of the feed solution. The methanol conversion increased with increasing heating rate to achieve a maximum of approximately 96%. A gas production rate comparable to that achieved with only a feed of liquid methanol was obtained for the same heating rate. An increase in the steam-carbon ratio caused an increase in conversion of the water–gas shift reaction towards increased equilibrium conversion. The hydrogen production rate showed a significant dependence on the parameters that affected the flow rate and conversion for these reactions.