Hydrogen production via catalytic decomposition of methane

Methane decomposition on various Ni-supported catalysts has been investigat ed as a method for production of CO-free hydrogen for use in fuel cells. Th e low levels of CO formed due to the interaction of surface carbon (formed from methane decomposition) with the support have been quantitatively analy zed (part per million levels) by methanation of the CO and subsequent analy sis by flame ionization detection (FID). This study highlights the dependen ce 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 elevate d methane decomposition temperatures, whereas Ni/HY and Ni/SiO2 showed fila mentous carbon formation over the entire temperature range studied (723 K t o 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 stabil ized rate. The CO formation rates were found to increase with increasing te mperature. 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 stabili zed. The low levels of CO coupled with the stability of the catalysts for m ethane decomposition make this an interesting conceptual process for hydrog en production for fuel cell applications. Regeneration studies have shown t hat 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.