Hydrogen production via catalytic decomposition of methane

Methane decomposition on various Ni-supported catalysts has been investigated as a method for production of CO-free hydrogen for use in fuel cells. The low levels of CO formed due to the interaction of surface carbon (formed from methane decomposition) with the support have been quantitatively analyzed (part per million levels) by methanation of the CO and subsequent analysis by flame ionization detection (FID). This study highlights the dependence of the type of carbon formed and the amount of CO evolved on the nature of the support. No filamentous carbon was observed on Ni/H-ZSM-5 at elevated methane decomposition temperatures, whereas Ni/HY and Ni/SiO2 showed filamentous carbon formation over the entire temperature range studied (723 K to 873 K). While two forms of carbon (carbidic and graphitic) were observed on the Ni/SiO2 after methane decomposition at 723 K, only graphitic carbon was observed at 823 K. The rate of CO formation was observed to be highest on Ni/H-ZSM-5 and lowest on Ni/SiO2. The CO formation rates showed a common trend for ail the catalysts: high initial rates followed by a lower stabilized rate. The CO formation rates were found to increase with increasing temperature. The CO content in the hydrogen stream was ca. 50 ppm and 250 ppm for Ni/SiO2 and Ni/HY, respectively, after the CO production rates stabilized. The low levels of CO coupled with the stability of the catalysts for methane decomposition make this an interesting conceptual process for hydrogen production for fuel cell applications. Regeneration studies have shown that there is no loss of activity for methane decomposition at 723 K on Ni/H-ZSM-5 over many reaction cycles. (C) 2001 Academic Press.