The U. S. currently produces nine million tons of hydrogen per year. This will need to increase by an order of magnitude to fully implement the hydrogen economy. Traditionally, hydrogen has been produced by reforming or partial oxidation of hydrocarbons to produce synthesis gas, followed by the water-gas shift reaction to convert CO to CO_2 and produce more hydrogen, followed by separation procedures. However, further purification steps are then required to reduce CO to the ppm levels tolerable by the catalysts used in the PEM fuel cells that will likely be used in vehicles. Non-oxidative, catalytic decomposition of hydrocarbon gases and liquids is an alternative one-step process to produce pure hydrogen. Previously, we have reported that binary Fe-M catalysts (M = Ni, Mo, or Pd) supported on high surface area γ-alumina decreased the decomposition temperatures of methane, ethane, and propane by 400-500°C and yielded 70-90% hydrogen in the temperature range of 650 to 800°C. Most of the carbon is produced in the form of multi-walled nanotubes (MWNT), whose form can be varied from parallel-walled MWNT to stacked-cone nanotubes (SCNT) by lowering the temperature from 700 to ～500°C. Although the nanotubes are obviously a potentially valuable by-product, significant problems were encountered in cleaning the nanotubes because of difficulty in dissolving the alumina support. In this paper, new results are reported using a Mg-Al oxide support that was easily dissolved in a nitric acid solution.
展开▼
