Aiming at the valorization of CO2 through its capture by simply extruded high cell-density coal honeycombs

Abstract

Integral coal honeycomb monoliths were easily prepared achieving the cell densities typical of commercial cordierites through extrusion plus physical activation. Different techniques such as volumetric adsorption, TGA, TPD and transient kinetic analysis were employed to study their interaction with CO2 at different temperatures (35–100 °C) and under both static and dynamic atmosphere. The CO2 capture capacity resulted to be 0.95 mmol/g at 35 °C, much higher than that of previously studied clay honeycomb adsorbents. The CO2 uptake exhibited fast second order kinetics, and a wide operative window for a highly efficient CO2 removal was found. Moreover, due to a weak interaction, most CO2 adsorbed could be released at 110 °C, what allows minimizing the costs related to controlled regeneration if ones wants to reuse the captured CO2 but at the same time prevents from desorption when this is undesirable. Treatment of the coal honeycomb monolith with a 1:1 CO2+CH4-containing stream revealed, through gas chromatography analysis, the conversion into syngas at relatively low temperatures (50% at 750 °C) in spite of the metal-free character of the monolith. Moreover, this activity reached 90% and remained quite stable for at least 12 h at 900 °C. These results demonstrate the potential of preparing honeycomb monoliths from coal as a strategy to diversify the uses of this abundant natural resource and as an alternative in the field of CO2 capture and valorization.