Authors:

Jackson Boodry

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About Paper:

Non-oxidative conversion of methane (NOCM) into value-added longer-chain hydrocarbons facilitates the transport of gas resources from drilling locations to chemical plants/refineries. The NOCM reaction is hypothesized to be catalyzed by edge-defect sites on carbon-based supports at high (>1100 K) temperatures to overcome thermodynamic constraints. Zeolite-templated carbons (ZTCs) and carbon deposited on desilicated zeolite frameworks such as chabazite (CHA) are proposed to contain large densities of these edge-defects. ZTCs are synthesized via furfuryl alcohol impregnation into a faujasite (FAU) zeolite before heat treatment and propylene chemical vapor deposition (CVD). The zeolite framework is subsequently dissolved with hydrofluoric acid, leaving a carbonaceous material with the negative pore structure of FAU. Desilication of CHA zeolites involves selectively removing silicon from the framework through an alkaline (NaOH) treatment by preserving structure-directing-agents (SDAs) from zeolite synthesis inside the material, creating mesopores at crystallite exteriors to increase the surface area for carbon formation during NOCM. The crystallinity and pore volume of ZTC and CHA-based materials were studied via X-ray diffraction and gas adsorption characterization. Broader use of desilicated CHA as a catalyst is dependent on maintaining the number of Brønsted acid sites, which is quantified through temperature-programmed desorption. ZTC crystallinity and stability depends on CVD time and reactor hydrodynamics. Desilicated CHA stability is related to the Si/Al ratio of the parent framework and the temperature used for SDA removal. These results indicate a complex relationship between synthesis conditions and crystal stability, with application to NOCM necessitating treatment at conditions best suited for the reaction.

Source:

Purdue University / 2023

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Co-authors:

Jackson Boodry