A semi-continuous process for co-production of CO2-free hydrogen and carbon nanotubes via methane pyrolysis

Heterogeneous catalytic pyrolysis of hydrocarbons to produce CO2-free hydrogen and high-quality solid carbon have historically been stymied by issues related to catalyst deactivation by carbon formed during pyrolysis on the catalyst surface. In addition, a sys-tem that demonstrates sustained performance in terms of high con-version, high H2 yield, and high quality of produced carbon has remained elusive. Here, we propose and demonstrate a semi -contin-uous methane pyrolysis process to H2 and carbon nanotubes (CNTs) consisting of repeated pyrolysis and in situ (i.e., within the reactor) CNT dislodging by vigorous steam/argon fluidization. With this pro-cess, we demonstrate 10 process cycles with high H2 yield from CH4 and CNT dislodging in a fluidized-bed reactor with an Fe/q-Al2O3 catalyst synthesized by an easily scalable incipient wetness impreg-nation process. We also identify and present opportunities for future catalyst and process development.