Iron–Potassium on Single-Walled Carbon Nanotubes as Efficient Catalyst for CO2 Hydrogenation to Heavy Olefins

Abstract

The iron–potassium catalysts supported on single- and multiwalled carbon nanotubes, FeK/SWNTs and FeK/MWNTs, were fabricated, characterized, and evaluated in CO 2 hydrogenation. The FeK/SWNTs catalyst outperforms the FeK/MWNTs catalyst in selectivity during CO 2 hydrogenation to olefins with the selectivities being 62.3% and 52.4%, respectively. Of particular interest is that the FeK/SWNTs catalyst is more selective toward heavy olefins (C 5+ = selectivity, 39.8%), whereas the FeK/MWNTs catalyst is more selective to light olefins (C 2 –C 4 = selectivity, 30.7%). The FeK/SWNTs catalyst also affords much lower selectivities to undesired CO and CH 4 in addition to higher productivity of hydrocarbons, thus resulting in an unprecedentedly high productivity of heavy olefins of 27.6 μmol CO2 g Fe –1 s –1 . The more electron-enriched exterior of SWNTs with large curvature, higher abundance of Hägg carbide, and stronger interaction with light olefins may rationalize the superior catalytic behavior of the FeK/SWNTs catalyst in CO 2 hydrogenation to heavy olefins. The FeK/SWNTs catalyst also exhibited a minor change in catalytic performance in a 120 h stability test, highlighting SWNTs as a promising catalyst support for producing value-added chemicals from greenhouse gas CO 2 .