Solar-thermal production of graphitic carbon and hydrogen via methane decomposition

05 November 2021, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

This work reports a process in which concentrated irradiation from a simulated solar source converts methane to high-value graphitic carbon and hydrogen gas. Methane flows within a photo-thermal reactor through the pores of a thin substrate irradiated by several thousand suns at the focal peak. The methane decomposes primarily into hydrogen while depositing highly graphitic carbon that grows conformally over ligaments in the porous substrate. The localized solar heating of the porous substrate serves to capture the solid carbon into a readily extractable and useful form while maintaining active deposition site density with persistent catalytic activity. Results indicate a strong temperature dependence with high decomposition occurring in the central heating zone with concentration factors and temperatures above 1000 suns and 1300 K, respectively. Even with a large flow area through regions of lower irradiation and temperature, methane conversion and hydrogen yields of approx. 70\% are achieved, and 58\% of the inlet carbon is captured in graphitic form.

Keywords

hydrogen
methane pyrolysis
concentrated solar
graphite

Supplementary materials

Title
Description
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Title
Video of methane decomposition products under periodic irradiation.
Description
Time response of (left) methane mole fraction in the product stream and (right) IR absorption spectrum during pulsed on/off exposure of the simulated solar concentrator at 1-minute intervals. Flow rate of 100 sccm, pressure of 25 Torr, gross peak radiant power of 2.24 kW.
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