Hydrogen Separation and Purification

Realization of the vision of “hydrogen economy” and utilization of hydrogen as an energy carrier will require increasing the hydrogen production by more than an order of magnitude over the current production levels. About 42 million t of hydrogen is currently produced per year worldwide. Most of the hydrogen is used captively on-site in “nonenergy” uses for the production of ammonia, methanol, and other chemicals and for hydroprocessing in petroleum refi neries primarily to remove sulfur and upgrade the heavier fractions into more valuable products (ORNL, 2003). The hydrogen production in the United States is estimated to be about 9 million t/year, 7.5 million of which are consumed on-site. The remaining 1.5 million t/year of hydrogen production may be considered as transportable and available for other applications (National Academies Press, 2004). For utilization in hydrogen-powered cars, almost 40 million t/year of hydrogen will have to be produced to be able to support 100 million cars in the United States (U.S. Department of Energy, 2002). The demand for hydrogen will escalate even more if hydrogen is used as an energy carrier for power generation applications, for example, portable or distributed power. Centralas well as distributed hydrogen generation plants will probably be necessary to meet the projected hydrogen demand. For successful transition to hydrogen economy, hydrogen must also be affordable.