(512b) Modular Processing of Flare Gas for Hydrogen and Carbon Nanofibers

In the United States, the “shale boom” and wide implementation of hydraulic fracturing has dramatically reduced the price of natural gas. As a result, oil producers increasingly choose to flare or vent associated natural gas rather than sell it, as investing in expensive transportation infrastructure, such as pipelines, is less economically prudent. Moreover, tight oil wells exhaust quickly as production from a single well depletes rapidly, thus imposing difficulties in predicting the optimal pipeline location_[1]. A profitable alternative to harnessing this waste of natural resources is needed.

A one-step Catalytic-Chemical Vapor Deposition (CCVD) process to produce carbon nanofibers (CNFs), carbon nanoparticles (CNPs), and hydrogen is a financially promising repurposing of the flared natural gas. An economically viable CCVD process largely depends on the production of a cheap catalyst. Particle Atomic Layer Deposition (ALD) enables the formation of highly dispersed metal nanocatalysts on a given support. The highly dispersed low-cost catalyst is essential as this process contains a sacrificial catalyst; the catalyst, support, CNFs and CNPs combine as one product to improve the strength and durability of concrete. The sacrificial catalyst circumvents the well-known disadvantages of rapid catalyst deactivation in methane thermal cracking_[2] and avoids the costly step of catalyst/product separation. To combat the challenges of rapid well depletion, this process will be scaled up to a modular unit that can be transferred between hydraulic fracturing sites. If each flare site in the United States transitioned to this modular CCVD process, over 30 million metric tons of CO₂ emissions per annum could be eliminated_[3].

In this work, transition metals are deposited onto a silica fume support via ALD. CNFs and CNPs are then produced via CCVD of methane with the ALD nanocatalyst. The carbon product is evaluated for its improvements to concrete durability via various compression and deformation tests. The carbon product evaluation and empirical reaction data inform both the modular unit design and technoeconomic analysis.

[1] Energy, B. The Williston Basin: Greasing the Gears for Growth in North Dakota; BENTEK Energy: 2012, 2012

[2] Abanades, A.; Ruiz, E.; Ferruelo, E. M.; Hernandez, F.; Cabanillas, A.; Martinez-Val, J. M.; Rubio, J. A.; Lopez, C.; Gavela, R.; Barrera, G.; Rubbia, C.; Salmieri, D.; Rodilla, E.; Gutierrez, D., Experimental analysis of direct thermal methane cracking. International Journal of Hydrogen Energy 2011, 36 (20), 12877-12886.

[3] U.S. Energy Information Administration. Natural Gas Gross Withdrawals and Production.

http://www.eia.gov/dnav/ng/ng_prod_sum_a_epg0_vgv_mmcf_a.htm (accessed April, 2021)