A semi-continuous process for co-production of CO2-free hydrogen and carbon nanotubes via methane pyrolysis
Eddie Sun, Shang Zhai, Dohyung Kim, Marco Gigantino, Vasudev Haribal, Oliver S. Dewey, Steven M. Williams, Gang Wan, Alexander Nelson, Sebastian Marin-Quiros, Joel Martis, Chengshuang Zhou, Jinwon Oh, Richard Randall, Max Kessler, Dongjae Kong, Jimmy Rojas, Andrew Tong, Xintong Xu, Cassandra Huff, Matteo Pasquali, Raghubir Gupta, Matteo Cargnello, Arun Majumdar
Abstract
Heterogeneous catalytic pyrolysis of hydrocarbons to produce CO<sub>2</sub>-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 system that demonstrates sustained performance in terms of high conversion, high H<sub>2</sub> yield, and high quality of produced carbon has remained elusive. Here, we propose and demonstrate a semi-continuous methane pyrolysis process to H<sub>2</sub> 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 process, we demonstrate 10 process cycles with high H<sub>2</sub> yield from CH<sub>4</sub> and CNT dislodging in a fluidized-bed reactor with an Fe/q-Al<sub>2</sub>O<sub>3</sub> catalyst synthesized by an easily scalable incipient wetness impregnation process. We also identify and present opportunities for future catalyst and process development.