Catalytic Methane Pyrolysis with Liquid and Vapor Phase Tellurium
Jiren Zeng, Maryam Tarazkar, Tyler Pennebaker, Michael J. Gordon, Horia Metiu, Eric W. McFarland
Abstract
Methane pyrolysis transforms CH4 into hydrogen and solid carbon without a CO2 byproduct. Using a high-temperature liquid catalyst in a bubble column reactor, deactivation from coking is avoided and the solid carbon removed. As an element with high electron affinity, liquid tellurium is an active methane pyrolysis catalyst with an apparent activation energy of 166 kJ/mol. At the reaction temperature of approximately 1000 °C, Te has a high vapor pressure and the vapor is also found to be a catalyst with an apparent activation energy of 178 kJ/mol. Contrary to results obtained for other molten alloy catalysts, dissolving Ni in molten tellurium lowers the pyrolysis activity. Quantum mechanical calculations were performed with accurate methods for the gas-phase reaction, and with ab initio, constant-temperature, molecular dynamics (MD) simulations with energies computed using density functional theory for the liquid phase.